Next Article in Journal
Halomonas kashgarensis sp. nov., a Novel Species Isolated from the Rhizosphere Soil of Phragmites australis (Cav.) Trin. ex Steud in Kashgar County, Xinjiang, China
Previous Article in Journal
New Mitogenomes of the Harnischia Generic Complex (Diptera: Chironomidae) and Their Implication in Phylogenetics
Previous Article in Special Issue
Habitat Fragmentation Enhances the Difference between Natural and Artificial Reefs in an Urban Marine Coastal Tract
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Diversity
Volume 17
Issue 2
10.3390/d17020097
diversity-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Mesopelagic Fish Biodiversity in the Ligurian Cetacean Sanctuary

by
Luca Lanteri
1,*,
Cecilia Pinto
1,
Giovanni Palandri
1,
Chantal Cima
1,
Matteo Dei
2,
Giulio Relini
1,
Lidia Orsi Relini
1 and
Fulvio Garibaldi
1
1
Dipartimento di Scienze della Terra dell’Ambiente e della Vita (DISTAV), Università degli Studi di Genova, Corso Europa 26, 16132 Genoa, Italy
2
Geostream Iberica SL, Calle Santiago Ramón y Cajal 84, 28939 Arroyomolinos, Spain
*
Author to whom correspondence should be addressed.
Diversity 2025, 17(2), 97; https://doi.org/10.3390/d17020097
Submission received: 17 July 2024 / Revised: 24 January 2025 / Accepted: 24 January 2025 / Published: 29 January 2025
(This article belongs to the Special Issue The Ligurian Sea and the National Biodiversity Future Centre (NBFC): Biodiversity Conservation in a Temperate Marine Environment under Threat)
Browse Figures
Versions Notes

Abstract

:
Mesopelagic fish belonging to the families Gonostomatidae, Phosichthyidae, Sternoptychidae, Stomiidae, Paralepididae, Myctophidae, Evermannellidae, Microstomatidae, and Nemichthyidae were sampled using an Isaacs Kidd Midwater Trawl (IKMT) in the Ligurian Sea, Northwestern Mediterranean, the core of the Cetacean Sanctuary established in 2001. In September–October 2002 and September 2003, 31 species of mesopelagic fish were captured in oblique hauls from 800 m depth to the surface. The mesopelagic fish fraction represented about 22% of the collected biomass, dominated by two main species of the genus Cyclothone, representing 93.8% of total abundance, followed by Argyropelecus hemigymnus and Lampanyctus crocodilus. The presence of Valenciennellus tripunctulatus was a new record for the study area. The family Myctophidae was the most represented in terms of number of species (n = 13). The abundance and biodiversity of mesopelagic fishes were influenced by the sampling period and oceanographic conditions, specifically temperature. While no diel vertical migrations could be observed, day and night samples revealed different compositions of juveniles and adults of Benthosema glaciale and Ceratoscopelus maderensis. The broad size range of specimens sampled confirmed that adult individuals of Chauliodus sloani and Lampanyctus crocodilus can inhabit and forage within the water column beyond the slope rather than exclusively near the bottom.

1. Introduction

For descriptive purposes, the mesopelagic ichthyofauna of the Mediterranean Sea can be divided into two groups. The first one is represented by large fish, such as Centrolophidae, Gempylidae, Lampridae, Luvaridae, Trichiuridae, etc., which are caught occasionally or regularly during professional and/or recreational fishing activities [1]. They frequently constitute an appreciated fishery resource, forming a continuum with other fish that live both at the surface and in mesopelagic waters, e.g., swordfish, which are probably the best known mesopelagic hunters [2,3]; tunas, which have similar feeding habits [4,5]; and pelagic sharks, such as Prionace glauca (Linnaeus, 1758) [6,7,8].
The second group is represented by small species (Gonostomatidae, Sternoptychidae, Myctophidae, etc.) of no commercial value, which can be studied only by dedicated sampling.
Studying the qualitative and quantitative aspects of pelagic ichthyofauna is a necessary step towards understanding the trophic web of the Cetacean Sanctuary. Small mesopelagic fish, ranging from the size of Cyclothone to larger species, such as Chauliodus sloani Bloch & Schneider, 1801 or Sudis hyalina Rafinesque, 1810 occupy an important trophic level positioned between mesozooplankton and intermediate or top predators, which include cephalopods, the above-mentioned large fish, and marine mammals. In the study area, the Ligurian Sea, which forms a major part of the established Cetacean Sanctuary, small mesopelagic fish are common prey also for cetaceans such as Stenella coeruleoalba (Meyen, 1833), the most abundant species of the Sanctuary, and for Delphinus delphis Linnaeus, 1758 [9,10,11,12]. It is still a matter of debate whether larger cetacean species such as Physeter macrocephalus Linnaeus, 1758; Ziphius cavirostris Cuvier, 1823; and Balaenoptera physalus Lacépède, 1804 feed, at least occasionally [13], on this kind of prey.
In recent years, other reasons for studying mesopelagic fish are becoming evident, as the Mediterranean Sea ichthyofauna has rapidly been enriched by exotic species coming both from the Atlantic Ocean and the Indo-Pacific Ocean [14]. The Atlantic group of immigrants includes deep sea species such as Cubiceps capensis (Smith, 1845) [15,16]; Hyperoglyphe perciformis (Mitchill, 1818) [16]; Halosaurus ovenii Johnson, 1864 [14]; Chaunax suttkusi Caruso, 1989 [14]; Gephyroberyx darwinii (Johnson, 1866) [14]; Beryx splendens Lowe, 1834 [17]; and Zenopsis conchifer (Lowe, 1852) [18]. In the Atlantic, several species that inhabit the slope are known to be moving northward in response to ocean warming [19,20]. In addition, the Indo-Pacific group includes at least one species living in deep waters that has never been recorded in the Red Sea, Synagrops japonicus (Doderlein, 1883), whose presence in the Mediterranean Sea could be attributed to transport in ballast water [21]. More recent arrivals of exotic species in the Northwestern Mediterranean area [22,23,24,25] are becoming increasingly important due to both global warming and anthropic activities, such as maritime traffic and aquaculture, and it could potentially also affect the small mesopelagic ichthyofauna, but so far, they all belong to shallow water species.
Many studies were performed in the Ligurian Sea by Italian and French teams to investigate the diel migration and vertical distribution of macroplankton and micronekton, which concerned different taxa (euphausiids, copepods, jellyfish, siphonophores, etc.) [26,27,28,29,30,31,32,33,34,35,36,37,38]. However, while in other areas of the Western Mediterranean, a number of scientific campaigns were held, in the Ligurian Sea, less attention has been given to the mesopelagic fish community: the Danish Oceanographical expedition with the R/V Thor (1908–1910) [39,40,41], the Smithsonian Expedition [42], and more recently the R/V Sarmiento de Gamboa expedition in 2009–2010 [43,44] and 2020 [45].
Within the Central and Western Ligurian Sea, our team investigated the community of small mesopelagic fish living in the depth range 0–800 m during several surveys of the R/V Minerva and Urania (1988–1993), which allowed the publication of the first description of the species composition and of their relative abundance in the area [5,46]. Taking into account the above-listed reasons of interest, this paper describes the composition of small mesopelagic ichthyofauna that was obtained in samples collected from the surveys of the R/V Urania and tug Messico (2002 and 2003), comparing it with other studies carried out in the Mediterranean Sea.

2. Materials and Methods

In September–October 2002 and September 2003, mesopelagic fish and macroplankton were sampled in the Central and Western Ligurian Sea (Figure 1), by means of a non-closing Isaacs Kidd Midwater Trawl (IKMT; mouth opening 15 feet, 2 mm × 2 mm mesh size in the cod end), with the support of two vessels: the tug Messico and the R/V Urania (SOLMAR project, SIRENA cruises 2002–2003, SACLANTCEN—La Spezia).
Sampling was carried out at 29 stations, divided into three surveys: five in September 2002 (Messico), six in October 2002, and 18 in September 2003 (Urania) (Table 1). The stations were located along transects that were established by the CNR, ISMAR (La Spezia, Santa Teresa), for the study of hydrological characteristics of the area. The sampling grid included two stations located near oceanographic buoys, ODAS (CNR, Italy) and DYFAMED (France), where measures of environmental and biological parameters have been recorded for many years [47,48,49,50,51].
The morphology of the Ligurian Sea and its hydrological characteristics are complex; in fact, the slope of the basin presents a segment facing north, from Corsica to Genoa, and another larger segment facing southwest, from Genoa to Cap d’Antibes. The main surface current of Atlantic origin, the Western Corsica Current, flows northward to the Gulf of Genoa and mixes with the Tyrrhenian current, thereby creating the Ligurian Current (or Northern Current), which flows to the southwest. In this way, the central part of the study area is encircled by a large permanent front. At the surface, this cyclonic gyre can probably form a complete ring, which tends to maintain planktonic organisms inside the area. In the vertical plane, the system concerns a water column deeper than 2500 m, where three main water masses can be identified: surface Atlantic Water (AW), Levantine Intermediate Water (LIW), and Deep Water (DW) [50,51]. The essential point is that LIW, where sampled mesopelagic fish mainly live, and in part also DW are influenced by the movements of surface water, with the possibility that temporary structures such as mesoscale vortexes may occur [50,51].
A total of 29 oblique hauls, from 800 m depth to the surface, were carried out at a towing speed of 3 knots, lasting 2 h each. A depth recorder and a flowmeter were positioned inside the net. The filtered volume was calculated by multiplying the flowmeter data by the mouth opening of the net, which was about 17.5 m2. Table 1 shows the details of each haul.
The whole catch was sorted in the following fractions: fishes (i.e., bony fishes), cephalopods, decapod crustaceans, northern krill, Meganyctiphanes norvegica (Sars, 1857), other crustaceans, pteropods, and gelatinous macroplankton. These were measured on board the vessel in terms of displaced volume (milliliters—mL) as a proxy of biomass. Fishes were fixed in a solution of 10% formalin/sea water or frozen immediately at −20 °C. Later on, in the laboratory, they were identified and sorted by species. Individuals of fish belonging to different species were counted (total number) in each station and were standardized into catch-per-unit effort (CPUE), considering 10,000 m3 of filtered water as unit of effort (ind./10,000 m3). The main reference textbook for the Mediterranean ichthyofauna is FNAM (Fishes of North-eastern Atlantic and the Mediterranean) [52], with 12 mesopelagic fish families described for Italian waters [53,54,55,56]. Following the Worms Editorial Board [57], we included Astronesthinae, Melanostomiinae, and Chauliodontinae in the family Stomiidae and separated Microstomatidae from the family Argentinidae; we also followed the revision of Paralepididae by Post [58], with changes in nomenclature.
The temperature data of the superficial layer (0–10 m) detected by the DYFAMED 1 buoy (Ligurian Sea, Western Mediterranean) were downloaded and are available on the website donneespubliques.meteofrance.fr (accessed on 1 September 2024).
The fish biodiversity at each station was reported by three indices:
Margalef index (species richness): d = (S − 1)/log(n)
where S is the species number, and n is the number of individuals.
Pielou index (species evenness): J = H′/log (S)
where H′ is the Shannon–Weaver index, and S is the systematic units of the sample.
Shannon–Wiener index: H′ = Σ (ni/n) (ln (ni/n))
where ni is the number of individuals of a taxon, and n is the total number of individuals.
One-way ANOVA was applied to test differences in diversity among the three surveys; a pairwise Tukey post hoc test was performed. Shapiro–Wilk and Levene tests were performed to verify the normal distribution and homogeneity of variance of tested data.
Multivariate analysis was performed to compare mesopelagic fish assemblages among different stations in terms of abundance (ind./10,000 m3). In order to reduce bias caused by the most abundant species, values were square root-transformed before applying multivariate methods.
Cluster and Multidimensional Scaling (MDS) analyses were applied by calculating Bray–Curtis similarity matrices, and a one-way analysis of similarity (ANOSIM) was performed in order to test the significant groups. Similarity Percentage analysis (SIMPER) was useful to verify the similarity between groups and identify species responsible for the differences. A two-way PERMANOVA analysis was performed to tests for differences in the composition of the mesopelagic community, considering light conditions (day vs. night samples) and sampling period (September vs. October) as fixed factors. All statistical analysis were performed using the Primer-6 [59,60] and Past 4.01 [61] software.
The most relevant species were measured as total length (TL, mm); length–frequency distributions (LFDs), expressed as percentages of the catch rate (ind./10,000 m3), were used to investigate modal size classes (cohorts) and differences in behavior among species during the diel vertical migration. To test the significance of the differences between LFDs, a non-parametric Kolmogorov–Smirnov (K-S) two-sample test was applied.

3. Results

3.1. Total Catches and Species List

A total of 29 hauls were made; despite the standardized procedure, the volume of filtered water ranged between 225,366 m3 and 305,178 m3 per haul, with an average of 266,452 m3 (SD = 22,411). Such variability could be explained by differences in the relative directions of the tow and currents that characterize the study area [51,62]. Average volumes of collected organisms were about 925.6 mL per haul, with a catch rate of 35.1 mL/10,000 m3 of filtered water. The average biomass composition (mL/10,000 m3) of the different fractions is shown in Figure 2; mesopelagic fishes followed the gelatinous macroplankton, a heterogeneous category that includes salps, ctenophores, and scyphozoans. By volume, the fraction of fish in each haul showed a lower variability (mean = 7.6 mL/10,000 m3; SD = 2.5) than other fractions.
More than 40,000 mesopelagic fishes, belonging to at least 31 species (9 families), were captured during the three surveys (Table 2). The CPUE of mesopelagic fish was 61.4 ind./10,000 m3; only two families, Gonostomatidae and Myctophidae, represented 96.9% (59.4 ind./10,000 m3) of the total catch, followed by Argyropelecus hemigymnus Cocco, 1829, with 2.4% (1.45 ind./10,000 m3). By abundance, the two Cyclothone species alone represented 93.8% of the total (57.6 ind./10,000 m3).
The group of the rarest species, represented by one to three specimens, included Valenciennellus tripunctulatus (Esmark, 1871); this species was recorded for the first time in the study area and, more generally, in the Western Mediterranean. A number of juvenile Paralepididae (n = 37), leptocephali, and larvae remained unidentified, together with some damaged specimens. These unidentified categories amount to 0.13% of the total number (Table 2).
By volume/biomass (mL/10,000 m3), the top four families were Gonostomatidae, Myctophidae, Stomiidae, and Sternoptychidae (Figure 3), and the top five species were Cyclothone braueri Jespersen & Tåning, 1926; C. sloani; Lampanyctus crocodilus (Risso, 1810); Cyclothone pygmaea Jespersen & Tåning, 1926; and A. hemigymnus, which represented 90% of the species (Figure 3).

3.2. Biodiversity Indexes

The number of species increased in relation to the number of hauls at different growth rates during the three surveys, reaching a total of 19 species in Messico 2002 (5 hauls carried out in the central–western sector), 24 species in Urania 2002 (6 hauls carried out in the western sector) and 27 species in Urania 2003 (18 hauls covering the whole area) (Figure 4).
The number of species per station ranged from 10 to 17 (mean = 13.5; SD = 2.0), but only five were found at all sampling stations: C. braueri, C. pygmaea, L. crocodilus, Benthosema glaciale (Reinhardt, 1837), and A. hemigymnus.
One-way ANOVA was applied to test the difference between the diversity indices in the three surveys. A significant difference was found among the three indices (Shannon, Pielou, and Margalef; p-value < 0.05). The pairwise post hoc Tukey test (Figure 5) highlighted a difference between Urania 2003 and Urania 2002 in Shannon and Pielou indices but not with the Messico 2002 survey, suggesting that in Urania 2002, a single species dominated the catches more significantly than in Urania 2003. Margalef was significantly higher in Urania 2003 compared to the other surveys (p < 0.05), confirming the number of species was significantly higher in Urania 2003 after accounting for the higher number of hauls.

3.3. Mesopelagic Fish Assemblages/Communitys

The cluster analysis showed a high similarity (>75%) among the stations. A first separation occurred at a level of 80% of similarity, where four groups of stations were identified (Figure 6a).
Similar results were obtained by the MDS analysis, which confirmed the presence of two main groups characterized by the samples from the Urania 2002 survey (group c) and by a group comprising the stations of Messico 2002 and Urania 2003 (group b) (Figure 6b). Three hauls, namely 807, 810, and 918 (Urania 2003), had anomalous results.
The analysis of similarity (one-way ANOSIM) was performed considering the a priori hypothesis (H0) that there were no differences in species composition between the groups identified. The pairwise test, at 80% similarity level, detected a significant difference only between two groups (b and c) (global R = 0.83; p < 0.01) and not between the others.
The species contribution to the overall mesopelagic similarity (80% level) is reported in Table 3. SIMPER analysis showed that five species contributed to about 90% of the similarity: C. braueri, C. pygmaea, A. hemigymnus, L. crocodilus, and Ceratoscopelus maderensis (Lowe, 1839).
The two species of genus Cyclothone and A. hemigymnus, in terms of average catch rate, gave a different contribution between the two main groups (b, c): 78.4 ind./10,000 m3 (group c) against 26.2 ind./10,000 m3 (group b) in C. braueri, 29.6 ind./10,000 m3 (group c) against 13.8 ind./10,000 m3 (group b) in C. pygmea, and 2.6 ind./10,000 m3 (group c) against 0.8 ind./10,000 m3 (group b) in A. hemigymnus.
The PERMANOVA analysis, used to test the mesopelagic fish assemblage, revealed a significant difference among sampling periods (p < 0.001) (Table 4), while light presence (day/night samples) was not significant (p > 0.05). The difference due to the sampling period (September vs. October) was affected by the catch rate that, in October (Urania 2002), was more than twice (mean = 112.5 ind./10,000 m3, SD = 31.8) that of the samples from September (Messico 02 and Urania 03) (mean = 50.2 ind./10,000 m3, SD = 16.1).
This effect could be related to the variation in the water temperature of the superficial layer (0–10 m), as detected by the DYFAMED buoy that, in September (Messico 2002 and Urania 2003), showed higher results (~20.9 °C (SD = 0.1) and ~21.3 °C (SD = 0.2)) than in October (Urania 2002) (~18.1 °C (SD = 0.1)) (Figure 7).

3.4. Length Groups and Daily Variations in Species

The LFDs of five mesopelagic fish species revealed that catches were mainly represented by juveniles and, for some species, by the entire population, including subadult and adult specimens (Figure 8).
The jewel lanternfish L. crocodilus showed a polymodal distribution, with the main one comprising juveniles (modal size at 30 mm TL), representing more than 60% of the entire sample, and a second modal distribution at 70 mm TL followed by two less distinctive distributions comprising sub-adult and adult specimens. No significant differences (K-S test: p-value > 0.05) were detected between LFDs observed during day/night samples.
The Sloane’s viperfish C. sloani showed a polymodal distribution as well, with the main one comprising juveniles (modal size at 80 mm TL), representing 40% of the total sample, and at least 3–4 mixed distributions comprising sub-adult and adult specimens. No significant differences (K-S test: p-value > 0.05) were detected between LFDs observed during day/night samples.
The half-naked hatchetfish A. hemigymnus showed a clear division of the population into two size groups, namely the juveniles (modal size at 14 mm) and the adults and sub-adults (modal size at 30 mm TL), which represented more than 80% of the sample. The LFDs did not show significant differences (K-S test: p-value > 0.05) between specimens caught in day/night samples.
The glacier lantern fish B. glaciale showed a bimodal distribution comprising juveniles (24 mm) and subadult/adult individuals (34 mm TL). A significant statistical difference (K-S test: p-value < 0.05) was detected between day/night samples, with a predominance of the juveniles fraction (<28 mm TL) during the daily sample.
The Madeira lantern fish C. maderensis showed a distribution mainly comprising juveniles with a predominant modal size of 25 mm and one less visible at 30 mm TL. A significant statistical difference (K-S test: p-value < 0.05) was detected between day/night distributions, with a predominance of smaller individuals (<28 mm TL) in the daily samples.

4. Discussion

This study allowed the description of the mesopelagic fish community of the Ligurian Sea in offshore waters, integrating the available knowledge on the mesopelagic community of the Mediterranean Sea.
The sample of small mesopelagic fish obtained by the 2002–2003 surveys in the Ligurian Sea was represented by 31 species belonging to nine families, plus some unidentified juveniles. During previous surveys carried out in the same area (1988–1993) using the same IKMT net [5,46], nine additional species belonging to four families were recorded: Zu cristatus (Bonelli, 1819), Trachipterus trachypterus (Gmelin, 1789), Regalecus glesne Ascanius, 1772 (three large mesopelagic species found in larval stages), Nansenia oblita (Facciolà, 1887), Gonostoma denudatum Rafinesque, 1810, Diaphus metopoclampus (Cocco, 1829), S. hyalina, Lestidiops jayakari (Boulenger, 1889), and a species of Notoscopelus different from N. elongatus [5]. The last one was first indicated as Notoscopelus kroyeri (Malm, 1861), as in the Smithsonian list [42], but following [63], it was later identified as Notoscopelus bolini Nafpaktitis, 1975 [64]. The absence of these species in the present surveys could be due to chance, given that they were already listed in the group of “rare” fish (less than 0.01%). Another possibility is that some species are “rarely caught” in mesopelagic surveys, as they are associated with the shelf/slope and can be found only when sampling is carried out above this zone [43]. For example, Maurolicus muelleri (Gmelin, 1789) is surely not rare but probably lives in more coastal waters on the slope [43,65]. In fact, it is a common prey of Micromesistius poutassou (Risso, 1827) at epibathyal levels of the slope [66,67], and mass strandings can occur in winter on the shore of the Western Ligurian Riviera [68,69,70]. On the other hand, in the present sample, V. tripunctulatus was found, a species new to the Western Mediterranean Sea at time of the 2003 survey. Commonly present on the western side of Gibraltar, is rare in the Mediterranean, and it was recorded only in the Strait of Messina, the Southern Tyrrhenian Sea, and the Adriatic Sea [71]. In the Urania survey (2003), this fish was found twice, at stations 410 and 810, positioned along the transect Gulf of Genoa, north of Corsica: it was absent in repeated sampling previously carried out at the same stations during the 1990s. From these observations, considering the geographical distribution of all records and the water circulation in the Mediterranean [72], two alternative hypotheses may be formulated: (a) V. tripunctulatus is an Atlantic stray, and (b) there is a Mediterranean population, which is rarely sampled and more widely distributed than it was previously thought.
It is well known that the Mediterranean mesopelagic fish community is less diverse than the adjacent Atlantic community [45,73]. It includes four endemic species, C. pygmaea, N. elongatus, L. crocodilus [74], and Nansenia iberica Matallanas, 1985. This latter species is reported as being present in the Catalan Sea [75] and around the Balearic Islands [76], taking into account the difficulties in distinguishing it from N. oblita and the other species of the genus. In this context, the Ligurian Sea can be considered the area with the highest mesopelagic fish community richness of the Mediterranean Basin [43,45,65]. This was already shown by the Smithsonian Expedition [42]; from five stations (southwest of the Balearic Islands, west of Corsica, the Central Tyrrhenian Sea, the Central Ionian Sea, and south of Crete), a total of 21,574 specimens were collected, belonging to 35 species. The highest numbers of species were found at the stations positioned in the Central Mediterranean, with 29 species west of Corsica and 30 species in the Tyrrhenian Sea, including an Atlantic stray, Diogenichthys atlanticus (Tåning, 1928) (only one postlarva found in the westernmost station) and Paravocettinops trilinearis Kanazawa and Maul, 1967 (later on determined as a juvenile phase of N. scolopaceus). At the station west of Corsica, N. bolini (under the name N. kroyeri) and G. denudatum were found but not N. oblita, D. metopoclampus, S. hyalina, and Borostomias antarcticus (Lönnberg, 1905), which were found instead in the Ligurian Sea in the present and/or past surveys. Of these, B. antarcticus was discovered in the 1960s offshore Monaco and was later recorded in the Gulf of Genoa [77]. Some species, which were recorded in the Western Mediterranean and have sometimes been mentioned in the literature [78], were later on deleted as junior synonyms (i.e., Parabathophilus gloriae Matallanas, 1984, present accepted name Bathophilus nigerrimus Giglioli, 1882, or misidentification of other species as Lampanyctus intricarius Tåning, 1928) [79]. More recently, scientific cruises conducted in the Western Mediterranean (Balearic Islands and Alboran Sea) in 2009–2010 and 2020 recorded a total of 25 and 22 species, respectively [43,45]. In the Eastern Mediterranean, during the Smithsonian Expedition, only 17 species were found at the station south of Crete, a number comparable to a recent cruise conducted in the Gulf of Corinth in 2018-2019, with 15 species recorded [65], despite the fact that Golani reported 27 species of small mesopelagic fishes in the Eastern Mediterranean [80].
Thus, we can assume that small mesopelagic fish that are currently known to inhabit the Mediterranean also occur in the Sanctuary. They are represented by 40 species belonging to 13 families; only two species were missing: N. iberica found off Blanes [75] and the Balearic Islands [76] and Sygmops elongatus (Günther, 1878) found off the Balearic Islands [81] and in the Southern Tyrrhenian Sea [82] (under the name of Gonostoma elongatum), suggesting a possible immigration from the Atlantic.
At the time of the Smithsonian Mediterranean study, the station closest to our study area (Ligurian Sea—west of Corsica), showed a remarkable abundance of many of the listed species (17 of 29). In fact, the catch (in terms of N per hour) reached the maximum that was registered during the expedition: the top species were C. braueri (564/h vs. 511/h in the present study), C. pygmaea (500/h vs. 211/h), and, in order of decreasing abundance, C. maderensis, B. glaciale, Hygophum benoiti (Cocco, 1838), Vinciguerria attenuata (Cocco, 1838), Arctozenus risso (Bonaparte, 1840), A. hemigymnus, Paralepis coregonoides (Risso, 1820), and Lampanyctus pusillus (Johnson, 1890) [46]. Our study confirms the high abundance of the species C. braueri, which plays a key role in the food web of the Ligurian Sea [38] as much as the northern krill, M. norvegica [83]. Differently from other studies, the third and fourth most abundant species were, respectively, A. hemigymnus and L. crocodilus, while a lower presence of B. glaciale and C. maderensis, the two myctophids frequently reported in other areas of the Western Mediterranean [42,43,45], was observed. Although the characteristics of the net (mouth opened) did not allow to establish in detail the vertical distribution of the different species, it is clear how the presence of Cyclothone spp. strongly influenced the abundance distribution of all our samples. The dominant presence of this group is probably linked to the presence of a permanent layer, mainly around 200–400 m, that does not migrate towards the surface, which was identified in the Ligurian Sea and in the Balearic area [38,43]. Comparison of the Smithsonian data with the present series suggests that the basic structure of the fish community in the Ligurian Sea has remained the same over the years in terms of the dominant species, in both its qualitative and quantitative aspects.
The peculiarity of this research was that sampling stations were positioned in offshore waters generally deeper than 2000 m on the pelagic domain. This, in some way, may influence the catches, which showed a high similarity at all stations (>75%). Moreover, the distribution of mesopelagic fish fauna was uniform over the whole investigated area, probably influenced by its oceanographic specifically in the autumn (October). In fact, diversity indices (Shannon and Pielou) were significantly lower for the Urania 2002 survey held in October, confirming the presence of a few dominant species (Cyclothone spp. and A. hemigymnus) considered as non-migrant or weakly migrant species in other studies [38,43,45,65]. This result might be attributable to the sea surface temperatures registered in September, which were still high compared to temperatures in October (Figure 7). This increase in temperature together with the salinity observed in the superficial layer (0–200 m) and even in deep waters (200–600 m) between 2002 and 2006 [84] was attributed to a propagation of the Eastern Mediterranean Transient in the Western Mediterranean Sea [85,86,87]. This kind of scenario might have affected the composition of the mesopelagic community in the water column and created a vertical stratification delaying the vertical mixing of different strata [49,88]. The pelagic domain in the study area is deeply conditioned by events of dense water formation caused by the decrease in temperature due to cold wind activity in the autumn/winter season, which increases evaporation, increasing the salinity (density) and generating the vertical mixing of the water column [51,84]. Moreover, the Ligurian Sea is characterized by a counterclockwise gyre [50,51]; an important permanent geostrophic front exists between the peripheral zone Corsica Current and the Northern Current, where massive surface currents flow (i.e., the Ligurian Current), and a central zone of divergence that is characterized by slow currents and complex physical dynamics, where upwelling occurs [27,51,89,90,91].
In the literature, it was demonstrated that vertical distribution of mesopelagic fauna (zooplankton and micronekton) was variable and conditioned by many different factors: temperature, salinity, productivity, food availability, nutrient, season, bathymetry, and light [26,27,28,29,30,31,32,33,34,35,36,37,38,43,45,75,86,92]. Among these, light is considered one of the primary factors of diel migration in mesopelagic fish and their prey [26,27,28,29,30,31,32,33,34,35,36,37,38,43,45,75,86,92]. However, in our study, mesopelagic fish assemblages did not appear to be influenced by light conditions (day vs. night samples). This outcome could be attributed to our sampling approach, which employed oblique hauls spanning the entire water column (0–800 m) rather than focusing on a fixed layer, as in other studies [43,45,65]. Despite this limitation, our fishing gear (IKMT) proved effective in terms of both catchability (relative abundance) and selectivity (size range sampling) for various species. This effectiveness was achieved through a combination of a wide mouth opening (17.5 m2) and a fine internal mesh size (2 mm × 2 mm). Smaller nets were shown to be particularly suitable for collecting juveniles, while larger nets were better suited for capturing greater quantities of species and broader size ranges of specimens [43,63]. The efficiency of our gear enabled us to sample a wider range of sizes and life stages of C. sloani and L. crocodilus compared to other regions in the Western Mediterranean Sea [43,45]. The polymodal distributions observed in both species due to the presence of large specimens confirm a longer life span of these species [93,94,95]; furthermore, it might indicate that adult individuals, over the length of first maturity (L50) [96,97], can also live and prey in the water column outside the slope and not only near the bottom [43], where they are frequently caught by trawls [98,99,100]. A. hemigymnus has a short life span, as confirmed by the bimodal distribution and a study carried out in the same area [101]; its population is composed by juveniles and in large part by adults specimens (L50: 25 mm SL [102]), without a clear difference between day/night length distributions. This evidence confirms the habits of A. hemigymnus, which is considered a weakly migrant species without a clear vertical stratification of sizes [43,65]; furthermore, in the Balearic area, A. hemigymnus exhibited a daily mode that was larger (19–25 mm SL) than at night (14–16 mm SL) [43]. B. glaciale has a long life span of up to 7–8 years old [103] but reaches sexual maturity early (L50: 30 mm SL). In other Mediterranean areas, it is one of the more abundant species, together with C. maderensis [43,45]. Our samples were composed by two cohorts, a smaller one composed by juveniles detected during daily sampling and one of sub-adult/adults observed during the night samples. The absence of the largest individuals might be linked to the fact that mature specimens (>30 mm SL) were found deeper near the bottom, while juveniles (<30 mm) were frequently found between 0–80 m and 400–600 m depth at night [43]. C. maderensis has a brief life span (about 1 year old) and quickly reaches maximum size [104,105]. Our sample almost totally comprised juveniles (L50: 38 mm SL; [106]). The significant difference between day/night samples could be related to a bias due to the different growth rates of the two cohorts detected in our sample; this does not allow considerations regarding the vertical distribution in different life stages (juveniles/adults) but simply observation of the presence of juveniles during day and night sampling in equal measure. In other studies, C. maderensis was detected mainly near the surface at night [43], while during the daytime, adults remained in mesopelagic layers (200–1000 m) [105]. On the basis of sizes and sporadic biological data, our sample of small mesopelagic fishes could tentatively be assigned to three trophic levels: (1) at the base, the very abundant Cyclothone spp.; (2) at the intermediate position, A. hemygimnus and myctophids, which feed on both mesozooplanktonic and nektonic crustaceans and small fish, including Cyclothone spp. [98,101,107]; and (3) at the highest level, C. sloani, which feeds on myctophids and gonostomids [106,107]. These trophic levels are mirrored by the decreasing biomass of the corresponding families: (1) Gonostomatidae; (2) Sternoptychidae plus Myctophidae; and (3) Stomiidae (Chauliodontinae). Mesopelagic fishes represent important prey to a diversity of higher-trophic-level predators of the Cetacean Sanctuary (tuna, swordfish, and cetaceans). In past studies carried out in the Ligurian Sea, we observed that the preferred fish prey of the swordfish were Paralepididae and large mesopelagic species of Lampriformes [108,109]. C. sloani was found in the stomach contents of the common dolphin D. delphis, which is at present relatively rare in the Sanctuary [9]. On the other hand, the very common S. coeruleoalba feeds on members of the genera Ceratoscopelus, Chauliodus, Diaphus, Electrona, Hygophum, Lampanyctus, Lobianchia, Myctophum, Notoscopelus, Stomias, and Symbolophorus [5,10,11,12]. This is clearly due to the fact that wild animals feed on not only the most abundant species but also those that, on the basis of scientific sampling, seem to be rare. These patterns probably have a great influence on the distributions of large pelagic predators, and swordfish present the best yield-per-unit effort of the Ligurian professional fishery in the Northwestern sector [110,111], and cetaceans were always observed in large numbers in this area [112].
In conclusion, we acknowledge that our sample represents only a portion of the pelagic ichthyofauna; this is an obvious effect regarding all pelagic animals with good swimming capabilities when sampling is carried out using “scientific” nets. In fact, considering studies conducted on the diet of large pelagic predators or even monitoring professional fishing gear [1,3,5,7,8,9,10,11,12,13,109,110,111], the situation appears slightly different. Often, there may be very abundant populations of some fish species considered “rare”, which remain “hidden” in an environment that is very difficult to study and sample, and it would be more accurate to define them as “rarely sampled” [113]. Some examples include Evermannellidae (i.e., Evermannella balbo (Risso, 1820)) and Paralepididae (i.e S. hyalina) but also large fish such as Trachypteridae (i.e., Z. cristatus), Luvaridae (i.e., Luvarus imperialis Rafinesque, 1810), and Centrolophidae (i.e., Centrolophus niger (Gmelin, 1789)) that represent a by-catch species of the mesopelagic longlines fishery targeting swordfish in the Ligurian Sea [1]. For these reason, a multidisciplinary combination of different studies appears to be a necessary step for the future, even to identify potential good environmental status (GES) in the Marine Strategy Framework Directive (MSFD) for pelagic environmental/ecosystems of the Mediterranean area and, for the Pelagos Sanctuary area, to better understand the dynamics of the pelagic domain for improving the management strategies and tools for the conservation of cetaceans.

Author Contributions

Conceptualization, L.L., C.P., G.P., M.D., L.O.R. and F.G.; data curation, L.L., C.P., C.C., M.D. and F.G.; formal analysis, L.L., C.P., G.P., C.C., M.D., G.R., L.O.R. and F.G.; investigation, L.L., G.P., C.C., M.D., G.R., L.O.R. and F.G.; methodology, L.L., C.P., G.P., C.C., M.D. and L.O.R.; project administration, G.R. and L.O.R.; resources, G.R. and L.O.R.; software, L.L. and C.P.; supervision, G.R., L.O.R. and F.G.; validation, L.L. and C.P.; visualization, L.L., C.P. and F.G.; writing—original draft, L.L., C.P., L.O.R. and F.G.; writing—review and editing, L.L. and F.G. All authors have read and agreed to the published version of the manuscript.

Funding

The research was carried out in collaboration with CNR (Istituto di Oceanografia Fisica of La Spezia), and it was carried out during the SIRENA cruises (2002–2003) organized by SACLANTCEN (SACLANT Undersea Research Centre) within the SOLMAR Project. This research received no direct funding.

Institutional Review Board Statement

All relevant data are presented within the manuscript.

Data Availability Statement

Data are contained within the article.

Acknowledgments

We thank the staff of CNR, headed by M. Astraldi, who planned our sampling operations on board the R/V Urania. In particular, we thank M. Borghini, the chief of the expedition, and the captain and crew of the ship for on-board assistance. We thank also the crew of tug Messico for the collaboration and the referees for insightful comments that improved the quality of our paper.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Garibaldi, F. By-catch in the mesopelagic swordfish longline fishery in the Ligurian Sea (Western Mediterranean). Collect. Vol. Sci. Pap. ICCAT 2015, 71, 1495–1498. [Google Scholar]
  2. Carey, F.G.; Robinson, B.H. Daily patterns in the activities of swordfish, Xiphias gladius, observed by acoustic telemetry. Fish. Bull. 1981, 79, 277–292. [Google Scholar]
  3. Iglesias, I.S.; Santora, J.A.; Fiechter, J.; Field, J.C. Mesopelagic fishes are important prey for a diversity of predators. Front. Mar. Sci. 2023, 10, 1220088. [Google Scholar] [CrossRef]
  4. Legendre, R. La Faune Pelagique de l’Atlantique au Large du Golfe de Gascogne, Recueillie dans des Estomacs de Germon. 1re Partie: Poissons; Annales de l’Institut Océanographique Nouvell Serie; Blondel La Rougery: Paris, France, 1934; Volume 14, pp. 247–418. [Google Scholar]
  5. Orsi Relini, L.; Garibaldi, F.; Palandri, G.; Cima, C. La comunità mesopelagica e i predatori “di superficie”. Biol. Mar. Mediterr. 1994, 1, 105–112. [Google Scholar]
  6. Carey, F.G.; Scharold, J.V. Movements of blue sharks (Prionace glauca) in depth and course. Mar. Biol. 1990, 106, 329–342. [Google Scholar] [CrossRef]
  7. Garibaldi, F.; Orsi Relini, L. Abbondanza estiva, taglie e nicchia alimentare della verdesca nel Santuario Pelagico del Mar Ligure. Biol. Mar. Mediterr. 2000, 7, 324–333. [Google Scholar]
  8. Bernardini, I.; Garibaldi, F.; Canesi, L.; Fossi, M.C.; Baini, M. First data on plastic ingestion by blue sharks (Prionace glauca) from the Ligurian Sea (North-Western Mediterranean Sea). Mar. Pollut. Bull. 2018, 135, 303–310. [Google Scholar] [CrossRef]
  9. Orsi Relini, L.; Relini, M. The stomach content of some Delphinus delphis L. from the Ligurian Sea. Eur. Res. Cetaceans 1993, 7, 199–202. [Google Scholar]
  10. Wurtz, M.; Marrale, D. Food of striped dolphin Stenella coeruleoalba in the Ligurian Sea. J. Mar. Biol. Assoc. U.K. 1993, 73, 571–578. [Google Scholar] [CrossRef]
  11. Würtz, M. Mediterranean Pelagic Habitat: Oceanographic and Biological Processes, an Overview; IUCN: Gland, Switzerland; Malaga, Spain, 2010; pp. 1–88. [Google Scholar]
  12. Garibaldi, F.; Mignone, W.; Ballardini, M.; Di Guardo, G.; Tittarelli, C.; Podestà, M. New observations on Striped dolphin, Stenella coeruleoalba (Meyen, 1833) diet at North Western Tyrrhenian Sea. In Where to Go and What to Eat; Scaravelli, D., Zaccaroni, A., Eds.; Aracne: Rome, Italy, 2012; pp. 103–110. [Google Scholar]
  13. Garibaldi, F.; Cataldini, G.; Insacco, G.; Podestà, M. Stomach contents of Cuvier’s beaked whales, Ziphius cavirostris, stranded in Southern Italy. In Proceedings of the 29th Annual Conference of the European Cetacean Society, St. Julian’s, Malta, 23–25 March 2015. [Google Scholar]
  14. Golani, D.; Azzurro, E.; Dulcic, J.; Massutì, E.; Orsi Relini, L.; Briand, F. CIESM Atlas of Exotic Fishes in the Mediterranean, 2nd ed.; CIESM Publishers: Paris, France; Monaco, 2021; Volume 1, pp. 1–365. [Google Scholar]
  15. Ariola, V. Nuovo pesce abissale del Golfo di Genova (Cubiceps capensis Smith). Riv. Mens. Di Pesca E Idrobiol. Pavia 1912, 7, 185–192. [Google Scholar]
  16. Karrer, C. Occurrence of the barrelfish, Hyperoglyphe perciformis (Teleostei, Perciformes, Stromateoidei), in the Mediterranean Sea and off Portugal. Cybium 1986, 10, 77–83. [Google Scholar]
  17. Orsi Relini, L.; Palandri, G.; Garibaldi, F.; Gavagnin, P.F. First record of Beryx splendens (Osteichthyes, Berycidae) in the Mediterranean. Cybium 1995, 19, 317–319. [Google Scholar]
  18. Pinto, C.; Roppo Valente, G.; Rasore, N.; Olmi, E.; Lanteri, L.; Garibaldi, F.; Viva, C.; Neri, A.; Massaro, A.; De Carlo, F.; et al. Range expansion of the Atlantic fish Zenopsis conchifer (Lowe, 1852), family Zeidae, in the western Mediterranean Sea. Mediterr. Mar. Sci. 2023, 24, 90–95. [Google Scholar] [CrossRef]
  19. Quero, J.C. Changes in the Euro-Atlantic fish species composition resulting from fishing and ocean warming. Ital. J. Zool. 1998, 65, 493–499. [Google Scholar] [CrossRef]
  20. Bañón, R.; Del Rio, J.L.; Piñeiro, C.; Casa, M. Occurrence of tropical affinity fish in Galician waters, north-west Spain. J. Mar. Biol. Assoc. U.K. 2002, 82, 877–880. [Google Scholar] [CrossRef]
  21. Orsi Relini, L. Synagrops japonicus (Steindachner e Doderlein, 1884) (Pisces, Acropomatidae) nel Mediterraneo: Un migrante lessepsiano? Oebalia 1990, 16, 217–223. [Google Scholar]
  22. Vacchi, M.; Chiantore, M. Abudefduf vaigiensis (Quoy & Guinnard, 1825) a tropical damselfish in the Mediterranean Sea. Biol. Mar. Mediterr. 2000, 7, 841–843. [Google Scholar]
  23. Garibaldi, F.; Orsi Relini, L. Record of the bluespotted cornetfish Fistularia commersonii Rüppell, 1838 in the Ligurian Sea (NW Mediterranean). Aquat. Invasions 2008, 3, 471–474. [Google Scholar] [CrossRef]
  24. Orsi Relini, L.; Costa, M.R.; Relini, M. First record of the yellow sea chub Kyphosus incisor in the Mediterranean. Mar. Biodivers. Rec. 2010, 3, e4. [Google Scholar] [CrossRef]
  25. Ligas, A.; Sartor, P.; Sbrana, M.; De Ranieri, S. A new record of Kyphosus saltatrix (Pisces: Kyphosidae) along the Italian coasts (north-western Mediterranean). Mar. Biodivers. Rec. 2011, 4, e6. [Google Scholar] [CrossRef]
  26. Andersen, V.; Sardou, J. The diel migrations and vertical distributions of zooplankton and micronekton in the Northwestern Mediterranean Sea. 1. Euphausiids, mysids, decapods and fishes. J. Plankton Res. 1992, 14, 1129–1154. [Google Scholar] [CrossRef]
  27. Boucher, J.; Ibanez, F.; Prieur, L. Daily and seasonal variations in the spatial distribution of zooplankton populations in relation to the physical structure in the Ligurian Sea Front. J. Mar. Res. 1987, 45, 133–173. [Google Scholar] [CrossRef]
  28. Laval, P.; Braconnot, J.C.; Carré, M.C.; Goy, J.; Morand, P.; Mills, C.E. Small-scale distribution of macroplankton and micronekton in the Ligurian Sea (Mediterranean Sea) as observed from the manned submersible Cyana. J. Plankton Res. 1989, 11, 665–685. [Google Scholar] [CrossRef]
  29. Andersen, V.; François, F.; Sardou, J.; Picheral, M.; Scotto, M.; Nival, P. Vertical distributions of macroplankton and micronekton in the ligurian and tyrrhenian seas (northwestern mediterranean). Oceanol. Acta 1998, 21, 655–676. [Google Scholar] [CrossRef]
  30. Licandro, P.; Ibanez, F. Changes of zooplankton communities in the Gulf of Tigullio (Ligurian Sea, Western Mediterranean) from 1985 to 1995. Influence of hydroclimatic factors. J. Plankton Res. 2000, 22, 2225–2253. [Google Scholar] [CrossRef]
  31. Warren, J.D.; Demer, D.A.; McGehee, D.E.; Di Mento, R.; Borsani, J.F. Zooplankton in the Ligurian Sea: Part II. Exploration of their physical and biological forcing functions during summer 2000. J. Plankton Res. 2004, 26, 1419–1427. [Google Scholar] [CrossRef]
  32. McGehee, D.E.; Demer, D.A.; Warren, J.D. Zooplankton in the Ligurian Sea: Part I. Characterization of their dispersion, relative abundance, and environment during summer 1999. J. Plankton Res. 2004, 26, 1409–1418. [Google Scholar] [CrossRef]
  33. Raybaud, V.; Nival, P.; Mousseau, L.; Gubanova, A.; Altukhov, D.; Khvorov, S.; Ibañez, F.; Andersen, V. Short term changes in zooplankton community during the summer-autumn transition in the open NW Mediterranean Sea: Species composition, abundance and diversity. Biogeosciences 2008, 5, 1765–1782. [Google Scholar] [CrossRef]
  34. Licandro, P.; Icardi, P. Basin scale distribution of zooplankton in the Ligurian Sea (north-western Mediterranean) in late autumn. Hydrobiologia 2009, 617, 17–40. [Google Scholar] [CrossRef]
  35. Guerra, D.; Schroeder, K.; Borghini, M.; Camatti, E.; Pansera, M.; Schroeder, A.; Sparnocchia, S.; Chiggiato, J. Zooplankton diel vertical migration in the Corsica Channel (north-western Mediterranean Sea) detected by a moored acoustic Doppler current profiler. Ocean Sci. 2019, 15, 631–649. [Google Scholar] [CrossRef]
  36. Zagami, G.; Granata, A.; Brugnano, C.; Minutoli, R.; Bonanzinga, V.; Guglielmo, L. Spring copepod vertical zonation pattern and diel migration in the open Ligurian Sea (north-western Mediterranean). Prog. Oceanogr. 2020, 183, 102297. [Google Scholar] [CrossRef]
  37. Granata, A.; Bergamasco, A.; Battaglia, P.; Milisenda, G.; Pansera, M.; Bonanzinga, V.; Arena, G.; Greco, S.; Guglielmo, R.; Spanò, N.; et al. Vertical distribution and diel migration of zooplankton and micronekton in Polcevera submarine canyon of the Ligurian mesopelagic zone (NW Mediterranean Sea). Prog. Oceanogr. 2020, 183, 102298. [Google Scholar] [CrossRef]
  38. Granata, A.; Bergamasco, A.; Zagami, G.; Guglielmo, R.; Bonanzinga, V.; Minutoli, R.; Geraci, A.; Pagano, L.; Swadling, K.; Battaglia, P.; et al. Daily vertical distribution and diet of Cyclothone braueri (Gonostomatidae) in the Polcevera submarine canyon (Ligurian Sea, north-western Mediterranean). Deep-Sea Res. I 2023, 199, 104113. [Google Scholar] [CrossRef]
  39. Jespersen, P. Sternoptychidae. In Report on the Danish Oceanographical Expeditions 1908-10 to the Mediterranean and Adjacent Seas, Biology, A2; Host and Sons: Copenhagen, Denmark, 1915; pp. 1–41. [Google Scholar]
  40. Tåning, A.V. Mediterranean Scopelidae. In Report on the Danish Oceanographical Expeditions 1908-10 to the Mediterranean and Adjacent Seas; Host and Sons: Copenhagen, Denmark, 1918; p. 2. [Google Scholar]
  41. Jespersen, P.; Tåning, A.V. Mediterranean Sternoptychidae. In Report on the Danish Oceanographical Expeditions 1908-10 to the Mediterranean and Adjacent Seas; Host and Sons: Copenhagen, Denmark, 1926; 9A 12; pp. 1–59. [Google Scholar]
  42. Goodyear, R.H.; Gibbs, R.H., Jr.; Roper, C.F.E.; Kleckner, R.C.; Sweeney, M.J.; Zahuranec, B.J.; Pugh, W.L. Mediterranean Biological Studies. Final Report I–II; Smithsonian Institution: Washington, DC, USA, 1972; pp. 1–346. [Google Scholar]
  43. Olivar, M.P.; Bernal, A.; Molı́, B.; Peña, M.; Balbı́n, R.; Castellón, A.M.; Miquel, J.; Massuti, E. Vertical distribution, diversity and assemblages of mesopelagic fishes in the western Mediterranean. Deep-Sea Res. I 2012, 62, 53–69. [Google Scholar] [CrossRef]
  44. Peña, M.; Olivar, M.P.; Balbín, R.; López-Jurado, J.L.; Iglesias, M.; Miquel, J. Acoustic detection of mesopelagic fishes in scattering layers of the Balearic Sea (western Mediterranean). Can. J. Fish. Aquat. Sci. 2014, 71, 1186–1197. [Google Scholar] [CrossRef]
  45. Olivar, M.P.; Castellon, A.; Sabates, A.; Sarmiento-Lezcano, A.; Emelianov, M.; Bernal, A.; Yang, Y.; Proud, R.; Brierley, A.S. Variation in mesopelagic fish community composition and structure between Mediterranean and Atlantic waters around the Iberian Peninsula. Front. Mar. Sci. 2022, 9, 1028717. [Google Scholar] [CrossRef]
  46. Orsi Relini, L.; Garibaldi, F.; Lanteri, L.; Relini, G. Possible use of small mesopelagic ichthyofauna to ascertain GES in ocean areas of the Mediterranean. Biol. Mar. Mediterr. 2013, 20, 79–87. [Google Scholar]
  47. Siccardi, A.; Montanari, M. Odas Italia 1, Laboratorio Marino D’altura in Mar Ligure, Open Sea Laboratory in the Ligurian Sea; Istituto per l’Automazione Navale C.N.R.: Genova, Italy, 1997; pp. 1–40. [Google Scholar]
  48. Marty, J.C. The DYFAMED time-series program (French-JGOFS). Deep-Sea Res. II 2002, 49, 1963–1964. [Google Scholar] [CrossRef]
  49. Sparnocchia, S.; Schiano, M.E.; Picco, P.; Bozzano, R.; Cappelletti, A. The anomalous warming of summer 2003 in the surface layer of the Central Ligurian Sea (Western Mediterranean). Ann. Geophys. 2006, 24, 443–452. [Google Scholar] [CrossRef]
  50. Astraldi, M.; Borghini, M.; Cima, C.; Fabiano, M.; Galli, L.; Garibaldi, F.; Lanteri, L.; Licandro, P.; Marzi, E.; Misic, C.; et al. Pelagic Domain. The Cetacean Sanctuary “Pelagos”; Quaderni Habitat; Ministero Dell’ambiente e della Tutela del Territorio e del Mare in Collaborazione con il Museo Friulano di Storia Naturale: Rome, Italy, 2007; Volume 16, pp. 1–155.
  51. Migon, C.; Nival, P.; Sciandra, A. (Eds.) The Mediterranean Sea in the Era of Global Change 1. In 30 Years of Multidisciplinary Study of the Ligurian Sea; ISTE: London, UK; John Wiley & Sons: Hoboken, NJ, USA, 2020; pp. 1–234. [Google Scholar]
  52. Whitehead, P.J.P.; Bauchot, M.L.; Hureau, J.C.; Nielsen, J.; Tortonese, E. Fishes of the North-Eastern Atlantic and the Mediterranean; UNESCO: Paris, France, 1986; pp. 1–510. [Google Scholar]
  53. Tortonese, E. Fauna d’Italia. Osteichthyes (Pesci Ossei); Calderini: Bologna, Italy, 1970; Volume 10, pp. 1–565. [Google Scholar]
  54. Bini, G. Atlante dei Pesci Delle Coste Italiane; Mondo Sommerso Editrice: Rome, Italy, 1971; Volume 2, pp. 1–311. [Google Scholar]
  55. Relini, G.; Lanteri, L. Osteichthyes. Biol. Mar. Mediterr. 2010, 17, 649–674. [Google Scholar]
  56. Psomadakis, P.; Giustino, S.; Vacchi, M. Mediterranean fish biodiversity: An updated inventory with focus on the Ligurian and Tyrrhenian seas. Zootaxa 2012, 3263, 1–46. [Google Scholar] [CrossRef]
  57. World Register of Marine Species. 2024. Available online: https://www.marinespecies.org (accessed on 1 September 2024).
  58. Post, A. Results of the research cruises of FRV “Walther Herwig” to South America. LXVII. Revision of the subfamily Paralepidinae (Pisces, Aulopiformes, Alepisauroidei, Paralepididae). I. Taxonomy, morphology and geographical distribution. Arch. Fisch. Wiss. 1987, 38, 75–131. [Google Scholar]
  59. Clarke, K.R.; Warwick, R.M. Changes in Marine Communities: An Approach to Statistical Analyses and Interpretation; Natural Environment Research Council: Plymouth, UK, 1994. [Google Scholar]
  60. Clarke, K.R.; Gorley, R.N. PRIMER v6: User Manual/Tutorial; PRIMER-E: Plymouth, UK, 2006. [Google Scholar]
  61. Hammer, Ø.; Harper, D.A.T.; Ryan, P.D. PAST: Paleontological statistics software package for education and data analysis. Palaeontol. Electron. 2001, 4, 1–9. [Google Scholar]
  62. Bethoux, J.P.; Prieur, L.; Bong, J.H. Le courant Ligure au large de Nice. Océanographie pélagique méditerranéenne: Aspects interdisciplinaires de l’océanographie méditerranéenne dans le domaine pélagique. Oceanol. Acta 1988, 9, 59–67. [Google Scholar]
  63. Nafpaktitis, B.G. Review of the lanternfish genus *Notoscopelus* (family Myctophidae) in the North Atlantic and the Mediterranean. Bull. Mar. Sci. 1975, 25, 75–87. [Google Scholar]
  64. Palomera, I. Desarrollo larvario de Notoscopelus elongatus elongatus (Costa, 1844) y Notoscopelus bolini Nafpaktitis, 1975. Inv. Pes. 1983, 47, 263–276. [Google Scholar]
  65. Kapelonis, Z.; Siapatis, A.; Machias, A.; Somarakis, S.; Markakis, K.; Giannoulaki, M.; Badouvas, N.; Tsagarakis, K. Seasonal patterns in the mesopelagic fish community and associated deep scattering layers of an enclosed deep basin. Sci. Rep. 2023, 13, 17890. [Google Scholar] [CrossRef]
  66. Orsi Relini, L. (University of Genoa, Genoa, Italy). Personal communication, 1987.
  67. Mir-Arguimbau, J.; Navarro, J.; Balcells, M.; Martín, P.; Sabates, A. Feeding ecology of blue whiting (Micromesistius poutassou) in the NW Mediterranean: The important role of Myctophidae. Deep–Sea Res. I 2020, 166, 1–16. [Google Scholar] [CrossRef]
  68. Torchio, M. Nuove segnalazioni di Maurolicus muelleri (Gm.) nel Mar Ligure. Natura 1956, 47, 1–2. [Google Scholar]
  69. Torchio, M.; Barletta, G.; Bellagamba, G.; Maldini, D.; Torelli, A.R. Spostamenti dell’ittionecton—E suoi spiaggiamenti—In provincia di Savona, nel corso dell’ultimo trentennio: Nuove osservazioni e considerazioni eco-etologiche e conservazionistiche. Quad. Della Civ. Stn. Idrobiol. Milano 1984, 12, 2–32. [Google Scholar]
  70. Galli, M. Note di Biologia di Maurolicus muelleri (Gmelin, 1789) (Osteichthyes, Sternoptychidae). Master’s Thesis, University of Genoa, Genoa, Italy, 2003. [Google Scholar]
  71. Bacchiani, C.; Ammendolia, G.; De Matteo, S.; Cavallaro, M.; Fanelli, E.; Battaglia, P. New Documented Records of the Mesopelagic Fish Valenciennellus tripunctulatus (Sternoptychidae) in the Strait of Messina and a Review of Its Mediterranean Occurrences. Fishes 2024, 9, 397. [Google Scholar] [CrossRef]
  72. Millot, C. Circulation in the Western Mediterranean Sea. J. Mar. Syst. 1999, 20, 423–442. [Google Scholar] [CrossRef]
  73. Olivar, M.P.; Hulley, P.A.; Castellón, A.; Emelianov, M.; López, C.; Tuset, V.M.; Contreras, T.; Molì, B. Mesopelagic fishes across the tropical and equatorial Atlantic: Biogeographical and vertical patterns. Prog. Oceanogr. 2017, 151, 116–137. [Google Scholar] [CrossRef]
  74. Stefanescu, C.; Lloris, D.; Rucabado, J. Revalidation of Lampanyctus gemmifer (Goode and Bean, 1879), a junior synonym of Lampanyctus crocodilus (Risso, 1810) in the Atlantic ocean (Myctophidae). Cybium 1994, 18, 315–323. [Google Scholar]
  75. Matallanas, J. Nansenia iberica, a new species of Microstomatidae (Pisces, Salmoniformes). Cybium 1986, 10, 193–198. [Google Scholar]
  76. Merella, P.; Alemany, F.; Carbonell, A.; Quetglas, A. New record of Nansenia iberica (Salmoniformes: Microstomatidae) in Western Mediterranean. Cybium 1997, 21, 211–215. [Google Scholar]
  77. Tortonese, E.; Zunini Sartorio, T. Presence of an Astronesthid fish in the Mediterranean (Gulf of Genoa): Borostomias antarcticus (Lönnb). Doriana Suppl. Ann. Mus. Civ. St. Nat. Genova 1970, 5, 1–5. [Google Scholar]
  78. Quignard, J.P.; Tomasini, J.A. Mediterranean fish biodiversity. Biol. Mar. Mediterr. 2000, 7, 1–66. [Google Scholar]
  79. Allué, R.; Rubiés, P. Sobre la presencia de Lampanyctus intricarius Tåning, 1928 (Osteichthyes, Myctophidae) en el Mediterràneo Occidental. Inv. Pes. 1984, 48, 175–180. [Google Scholar]
  80. Golani, D. The Marine ichthyofauna of the Eastern Levant. Isr. J. Zool. 1996, 42, 15–55. [Google Scholar]
  81. Romàn, E.; Alemany, F.; Carbonell, A. First record of Gonostoma elongatum Günther, 1878 (Osteichthyes: Gonostomatidae) in the North-Western Mediterranean. Bol. Soc. Hist. Nat. Balear. 2000, 43, 27–31. [Google Scholar]
  82. Potoschi, A.; Battaglia, P.; Castriota, L.; Andaloro, F. First record of Gonostoma elongatum (Gonostomatidae) in the central Mediterranean Sea. Cybium 2009, 33, 173–174. [Google Scholar]
  83. Orsi Relini, L.; Relini, G.; Palandri, G.; Relini, M.; Garibaldi, F.; Cima, C.; Torchia, G.; Costa, C. Meganyctiphanes norvegica (Crustacea, Euphausiacea) in the Ligurian-Provençal basin: Notes on population size structures and growth. CIESM Rapp. Comm. Int. Mer Médit. 1998, 35, 474–475. [Google Scholar]
  84. Marty, J.C.; Chiaverini, J. Hydrological changes in the Ligurian Sea (NW Mediterranean, DYFAMED site) during 1995–2007 and biogeochemical consequences. Biogeosciences 2010, 7, 2117–2128. [Google Scholar] [CrossRef]
  85. Lopez-Jurado, J.L.; Gonzalez-Pola, C.; Velez-Belchi, P. Observation of an abrupt disruption of the log-term warming trend at the Balearic Sea, western Mediterranean Sea, in summer 2005. Geophys. Res. Lett. 2005, 32, L24606. [Google Scholar] [CrossRef]
  86. Schroder, K.; Gasparini, G.P.; Tangherlini, M.; Astraldi, M. Deep and intermediate water in the western Mediterranean under the influence of the Eastern Mediterranean Transient. Geophys. Res. Lett. 2006, 33, L21607. [Google Scholar] [CrossRef]
  87. Font, J.; Puig, P.; Salat, J.; Palanques, A.; Emelianov, M. Sequence of hydrographic changes in NW Mediterranean deep water due to the exceptional winter of 2005. Sci. Mar. 2007, 71, 339–346. [Google Scholar] [CrossRef]
  88. Bozzano, R.; Fanelli, E.; Pensieri, S.; Picco, P.; Schiano, M.E. Temporal variations of zooplankton biomass in the Ligurian Sea inferred from long time series of ADCP data. Ocean Sci. 2014, 10, 93–105. [Google Scholar] [CrossRef]
  89. Pinca, S.; Dallot, S. Mesozooplankton and macrozooplankton composition patterns related to hydrodynamic structures in the Ligurian Sea (TROPHOS-2 experiment, April–June 1986). Mar. Ecol. Prog. Ser. 1995, 126, 49–65. [Google Scholar] [CrossRef]
  90. Sournia, A.; Brylinski, J.M.; Dallot, S.; Le Corre, P.; Leveau, M.; Prieur, L.; Froget, C. Fronts hydrologiques au large des cotes francaises: Les site-ateliers du programme Frontal. Oceanol. Acta 1990, 13, 413–438. [Google Scholar]
  91. Orsi Relini, L.; Relini, G.; Cima, C.; Fiorentino, F.; Palandri, G.; Relini, M.; Torchia, G. Una zona di tutela biologica ed un parco pelagico per i cetacei del Mar Ligure. Boll. Mus. Ist. Biol. Univ. Genova 1992, 56–57, 247–281. [Google Scholar]
  92. Clavel-Henry, M.; Piroddi, C.; Quattrocchi, F.; Macias Moy, D.; Christensen, V. Spatial distribution and abundance of mesopelagic fish biomass in the Mediterranean Sea. Front. Mar. Sci. 2020, 573986. [Google Scholar] [CrossRef]
  93. Potoschi, A.; Cavallaro, G.; Cefali, A.; Bruno, R. Biologia e distribuzione di Lampanyctus crocodilus (Risso, 1810) sui fondi batiali del Tirreno meridionale. Oebalia 1992, 17, 93–99. [Google Scholar]
  94. Van Utrecht, W.L.; van Utrecht-Cock, C.N.; De Graaf, A.M.J. Growth and seasonal variations in distribution of Chauliodus sloani and C. danae (Pisces) from the mid North Atlantic. Bijdr. Tot De Dierkd. 1987, 57, 164–182. [Google Scholar] [CrossRef]
  95. Sion, L.; Carlucci, R.; Battista, D.; Capezzuto, F.; D’Onghia, G. Growth of Lampanyctus crocodilus (Risso, 1810) in the Ionian sea. Biol. Mar. Mediterr. 2011, 18, 148–149. [Google Scholar]
  96. Fanelli, E.; Papiol, V.; Cartes, J.E.; Rodriguez-Romeu, O. Trophic ecology of Lampanyctus crocodilus on north-west Mediterranean Sea slopes in relation to reproductive cycle and environmental variables. J. Fish. Biol. 2014, 84, 1654–1688. [Google Scholar] [CrossRef]
  97. Marks, A.D.; Kerstetter, D.W.; Wyanski, D.M.; Sutton, T.T. Reproductive Ecology of Dragonfishes (Stomiiformes: Stomiidae) in the Gulf of Mexico. Front. Mar. Sci. 2020, 7, 101. [Google Scholar] [CrossRef]
  98. Stefanescu, C.; Cartes, J.E. Benthopelagic habits of adult specimens of Lampanyctus crocodilus (Risso, 1810) (Osteichthyes, Myctophidae) in the western Mediterranean deep slope. Sci. Mar. 1992, 56, 69–74. [Google Scholar]
  99. Specchi, M.; Valli, G.; Pizzul, E.; Sampietro, L.; Cassetti, P. Osservazioni preliminari sulla struttura di popolazione di alcune specie batiali catturate nel basso Tirreno. Biol. Mar. Mediterr. 1995, 2, 519–521. [Google Scholar]
  100. D’Onghia, G.; Politou, C.Y.; Bozzano, A.; Lloris, D.; Rotllant, G.; Sion, L.; Mastrototaro, F. Deep-water fish assemblages in the Mediterranean Sea. Sci. Mar. 2004, 68, 87–99. [Google Scholar] [CrossRef]
  101. Montaldo, A.; Orsi Relini, L. Note di biologia di Argyroplecus hemigymnus Cocco 1829 (Osteichthyes, Sternoptychidae) in Mar Ligure. Biol. Mar. Mediterr. 1994, 1, 125–126. [Google Scholar]
  102. Badcock, J. Sternoptychidae. In Fishes of the North-Eastern Atlantic and the Mediterranean; Whitehead, P.J.P., Bauchot, M.-L., Hureau, J.-C., Nielsen, J., Tortonese, E., Eds.; UNESCO: Paris, France, 1984; Volume 1, pp. 302–317. [Google Scholar]
  103. Gjøsaeter, J. Growth, production and reproduction of myctophid fish Benthosema glaciale from western Norway and adjacent seas. Fiskdir. Skr. Ser. Havunders. 1981, 17, 79–108. [Google Scholar]
  104. Tomasz, B.L.; Radtke, R.L.; Lenz, P.H. Otolith microstructure, age and growth of two species of Ceratoscopelus (Osteichthyes: Myctophidae) from the eastern North Atlantic. J. Exp. Mar. Biol. Ecol. 1993, 167, 237. [Google Scholar]
  105. Real, E.; Bernal, A.; Morales-Nin, B.; Molí, B.; Alvarez, I.; Pilar Olivar, M. Growth patterns of the lanternfish Ceratoscopelus maderensis in the western Mediterranean Sea. Sci. Mar. 2021, 85, 71–80. [Google Scholar] [CrossRef]
  106. Butler, M.; Bollens, S.M.; Burkhalter, B.; Madin, L.P.; Horgan, E. Mesopelagic fishes of the Arabian Sea: Distribution, abundance and diet of Chauliodus pammelas, Chauliodus sloani, Stomias aznis and Stomias nebulosus. Deep. Sea Res. II Top. Stud. Oceanogr. 2001, 48, 1369–1383. [Google Scholar] [CrossRef]
  107. Battaglia, P.; Ammendolia, G.; Esposito, V.; Romeo, T.; Andaloro, F. Few But Relatively Large Prey: Trophic Ecology of Chauliodus sloani (Pisces: Stomiidae) in Deep Waters of the Central Mediterranean Sea. J. Ichthyol. 2018, 58, 8–16. [Google Scholar] [CrossRef]
  108. Orsi Relini, L.; Garibaldi, F.; Cima, C.; Palandri, G. Feeding of the swordfish, the bluefin and other pelagic nekton in the Western Ligurian Sea. Collect. Vol. Sci. Pap. ICCAT 1995, 44, 283–286. [Google Scholar]
  109. Garibaldi, F. Relazioni Trofiche tra Predatori di Vertice del Santuario dei Cetacei. Ph.D. Thesis, University of Genoa, Genoa, Italy, 2004. [Google Scholar]
  110. Palandri, G.; Orsi Relini, L.; Garibaldi, F. Cartografia di risorse pelagiche: I primi tentativi di rappresentare in GIS l’attività dei palamiti d’altura. Biol. Mar. Mediterr. 2000, 7, 549–557. [Google Scholar]
  111. Garibaldi, F. An update of the swordfish fishery in the Ligurian sea (Western Mediterranean). Collect. Vol. Sci. Pap. ICCAT 2017, 73, 1133–1140. [Google Scholar]
  112. Gnone, G.; Bellingeri, M.; Airoldi, S.; Gonzalvo, J.; David, L.; Di-Méglio, N.; Cañadas, A.M.; Akkaya, A.; Awbery, T.; Mussi, B.; et al. Cetaceans in the Mediterranean Sea: Encounter Rate, Dominant Species, and Diversity Hotspots. Diversity 2023, 15, 321. [Google Scholar] [CrossRef]
  113. Garibaldi, F. (University of Genoa, Genoa, Italy). Personal communication, 2024.
Diversity 17 00097 g001
Figure 1. (a) Western Mediterranean Sea, with emphasis on the study area and (b) sampling stations (red circles = Messico 02; green circles = Urania 02; white circles = Urania 03) for mesopelagic ichthyofauna with the Cetacean Sanctuary limits (red lines).
Figure 1. (a) Western Mediterranean Sea, with emphasis on the study area and (b) sampling stations (red circles = Messico 02; green circles = Urania 02; white circles = Urania 03) for mesopelagic ichthyofauna with the Cetacean Sanctuary limits (red lines).
Diversity 17 00097 g001
Diversity 17 00097 g002
Figure 2. Composition of the total catch in terms of biomass (mL/10,000 m3): (a) average catch rate values for different taxa (bars = SE) and (b) average percentage composition.
Figure 2. Composition of the total catch in terms of biomass (mL/10,000 m3): (a) average catch rate values for different taxa (bars = SE) and (b) average percentage composition.
Diversity 17 00097 g002
Diversity 17 00097 g003
Figure 3. Percentages of the most represented species and families in terms of abundance (ind./10,000 m3) and biomass (mL/10,000 m3).
Figure 3. Percentages of the most represented species and families in terms of abundance (ind./10,000 m3) and biomass (mL/10,000 m3).
Diversity 17 00097 g003
Diversity 17 00097 g004
Figure 4. Cumulative number of species in relation to the progress of the sampling in the three surveys.
Figure 4. Cumulative number of species in relation to the progress of the sampling in the three surveys.
Diversity 17 00097 g004
Diversity 17 00097 g005
Figure 5. Average values of biodiversity indexes in the three surveys (bars = SE).
Figure 5. Average values of biodiversity indexes in the three surveys (bars = SE).
Diversity 17 00097 g005
Diversity 17 00097 g006
Figure 6. Cluster (a) and MDS (b) analysis at 80% of similarity among the stations.
Figure 6. Cluster (a) and MDS (b) analysis at 80% of similarity among the stations.
Diversity 17 00097 g006
Diversity 17 00097 g007
Figure 7. Mean sea surface temperature registerd by the Boa Dyfamed between August and October 2002/2003. Measurements are not available for the first 6 days of September 2003.
Figure 7. Mean sea surface temperature registerd by the Boa Dyfamed between August and October 2002/2003. Measurements are not available for the first 6 days of September 2003.
Diversity 17 00097 g007
Diversity 17 00097 g008
Figure 8. Length–frequency distributions of five mesopelagic species: on the left is the total sample, and on the right, the day/night samples are separated.
Figure 8. Length–frequency distributions of five mesopelagic species: on the left is the total sample, and on the right, the day/night samples are separated.
Diversity 17 00097 g008
Table 1. List of sampling stations, with the main characteristics by haul.
Table 1. List of sampling stations, with the main characteristics by haul.
SurveyStationDateStarting
Time		Lat. NLong. EMinutes
Towed		D
Flowmeter		Day
Night
Messico 2002ikmt 227 September 200216:2243°37′5297°47′79412743,200D
ikmt 5 bis28 September 200206:2843°22′1708°02′42013038,050D
ikmt 328 September 200211:0643°18′6337°47′81113141,371D
ikmt 428 September 200215:3843°06′6107°44′58312544,774D
ikmt 528 September 200219:3343°14′3208°02′19711738,342N
Urania 200292914 October 200210:3942°42′96507°42′729913142,706D
93114 October 200218:4942°52′13607°30′480313339,819N
93415 October 200209:3543°10′847°04′030012842,217D
93815 October 200218:5543°20′62417°11′629612742,319N
92216 October 200209:1643°19′42957°03′633212638,881D
92016 October 200218:2243°07′31087°46′521312946,035N
Urania 20038102 September 200313:3543°05′29009°03′060012737,561D
8072 September 200322:1943°18′28278°35′663012541,192N
6044 September 200312:2744°00′44708°42′853812644,547D
6084 September 200322:4343°46′55888°34′531512650,064N
9025 September 200309:1643°37′14207°50′081012649,604D
9055 September 200321:0243°23′55007°59′717012650,863N
9086 September 200310:4542°53′54418°28′783513246,518D
9106 September 200317:2542°47′57568°33′899712842,262D
9277 September 200309:2742°31′25527°57′652612948,032D
929 bis7 September 200316:5242°43′47957°41′906812747,040D
9338 September 200310:5243°05′51677°11′396712647,040D
9398 September 200318:4643°15′79527°16′922812948,400N
9239 September 200312:1843°21′98477°28′344312845,467D
odas11 September 200320:4643°45′44789°08′134712844,715N
dyfamed12 September 200318:3043°26′86967°51′826112846,265N
92113 September 200309:5443°09′43277°44′801612745,326D
91813 September 200320:0042°50′41548°05′125413047,990N
41016 September 200318:0243°35′31698°54′401913047,252N
Table 2. List of mesopelagic fish species caught during the surveys, where n = total number, FO = frequency of occurrence (number of stations in which each species was found) and relative percentage (O%), CPUE = number of individuals of each species caught per 10,000 m3, and VOL = displaced mL for each species caught per 10,000 m3.
Table 2. List of mesopelagic fish species caught during the surveys, where n = total number, FO = frequency of occurrence (number of stations in which each species was found) and relative percentage (O%), CPUE = number of individuals of each species caught per 10,000 m3, and VOL = displaced mL for each species caught per 10,000 m3.
SpeciesnFOO%CPUEVOL
Cyclothone braueri Jespersen & Tåning, 1926 *31,49829100.040.761.01
Cyclothone pygmaea Jespersen & Tåning, 1926 *12,99529100.016.820.33
GONOSTOMATIDAE44,493--57.581.33
Lampanyctus crocodilus (Risso, 1810)47029100.00.610.89
Lampanyctus pusillus (Johnson, 1890)531965.50.070.01
Ceratoscopelus maderensis (Lowe, 1839)3802896.60.490.04
Hygophum benoiti (Cocco, 1838)2542482.80.330.01
Hygophum hygomii (Lütken, 1892)113.40.000.00
Benthosema glaciale (Reinhardt, 1837)19629100.00.250.06
Symbolophorus veranyi (Moreau, 1888)281344.80.040.01
Myctophum punctatum Rafinesque, 1810181448.30.020.01
Notoscopelus elongatus (Costa, 1844)171137.90.020.08
Diaphus rafinesquii (Cocco, 1838)6620.70.010.01
Diaphus holti Tåning, 19184413.80.010.00
Lobianchia dofleini (Zugmayer, 1911)226.90.000.00
Electrona risso (Cocco, 1829)113.40.000.00
MYCTOPHIDAE1430--1.851.11
Argyropelecus hemigymnus Cocco, 1829112429100.01.450.24
Maurolicus muelleri (Gmelin, 1789)313.40.000.00
Valenciennellus tripunctulatus (Esmark, 1871)226.90.000.00
STERNOPTYCHIDAE1129--1.460.24
Vinciguerria attenuata (Cocco, 1838)1042586.20.130.01
Vinciguerria poweriae (Cocco, 1838)226.90.000.00
Ichthyococcus ovatus (Cocco, 1838)3310.30.000.00
PHOSICHTHYDAE109--0.140.01
Chauliodus sloani Bloch & Schneider, 1801982793.10.131.00
Stomias boa (Risso, 1810)7620.70.010.01
Borostomias antarcticus (Lönnberg, 1905)113.40.000.01
Bathophilus nigerrimus Giglioli, 1882113.40.000.00
STOMIIDAE107--0.141.01
Arctozenus risso (Bonaparte, 1840)382482.80.050.02
Paralepis coregonoides Risso, 1820241448.30.030.00
Lestidiops sphyrenoides (Risso, 1820)6620.70.010.00
Paralepididae not identified371344.80.050.00
PARALEPIDIDAE105--0.140.02
Evermannella balbo (Risso, 1820)9724.10.010.02
EVERMANNELLIDAE9--0.010.02
Microstoma microstoma (Risso, 1810)326.90.000.00
MICROSTOMATIDAE3--0.000.00
Nemichthys scolopaceus Richardson, 1848226.90.000.07
NEMICHTHYDAE2--0.000.07
Leptocephali7413.80.010.00
Not identified fishes181034.50.020.00
Total47,412- 61.363.81
* Counted by subsamples.
Table 3. Similarity percentage (SIMPER) analysis within groups (80% similarity) identified by cluster and MDS and percentage contribution per species (cut-off level 90%).
Table 3. Similarity percentage (SIMPER) analysis within groups (80% similarity) identified by cluster and MDS and percentage contribution per species (cut-off level 90%).
Group b (Average Similarity: 84.13)
SpeciesAv.AbundAv.SimContrib%Cum.%
Cyclothone braueri5.3434.8541.4241.42
Cyclothone pygmaea3.8125.3230.171.52
Argyropelecus hemigymnus0.975.866.9678.48
Lampanyctus crocodilus0.694.295.183.58
Ceratoscopelus maderensis0.583.073.6587.24
Benthosema glaciale0.492.773.2990.53
Group c (Average Similarity: 84.78)
SpeciesAv.AbundAv.SimContrib%Cum.%
Cyclothone braueri8.7941.5649.0249.02
Cyclothone pygmaea5.3624.228.5477.56
Argyropelecus hemigymnus1.587.028.2885.84
Lampanyctus crocodilus0.83.474.0989.93
Ceratoscopelus maderensis0.461.892.2292.15
Group d (Average Similarity: 81.47)
SpeciesAv.AbundAv.SimContrib%Cum.%
Cyclothone braueri8.0936.6144.9444.94
Cyclothone pygmaea3.1515.2618.7363.66
Argyropelecus hemigymnus1.898.8110.8174.48
Ceratoscopelus maderensis1.494.235.1979.67
Lampanyctus crocodilus1.294.115.0584.72
Chauliodus sloani0.683.133.8588.57
Benthosema glaciale0.662.643.2491.81
Table 4. PERMANOVA analysis used to test the effect of the sampling period (September vs. October) and light (day vs. night samples) on mesopelagic fish assemblage.
Table 4. PERMANOVA analysis used to test the effect of the sampling period (September vs. October) and light (day vs. night samples) on mesopelagic fish assemblage.
SourceSum of SqrsdfMean SquareFp
Sampling period (S/O)0.661410.661414.58300.0001
Light (D/N)0.018910.01890.41750.5046
Residual1.1338250.0454
Total1.398628
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Lanteri, L.; Pinto, C.; Palandri, G.; Cima, C.; Dei, M.; Relini, G.; Orsi Relini, L.; Garibaldi, F. Mesopelagic Fish Biodiversity in the Ligurian Cetacean Sanctuary. Diversity 2025, 17, 97. https://doi.org/10.3390/d17020097

AMA Style

Lanteri L, Pinto C, Palandri G, Cima C, Dei M, Relini G, Orsi Relini L, Garibaldi F. Mesopelagic Fish Biodiversity in the Ligurian Cetacean Sanctuary. Diversity. 2025; 17(2):97. https://doi.org/10.3390/d17020097

Chicago/Turabian Style

Lanteri, Luca, Cecilia Pinto, Giovanni Palandri, Chantal Cima, Matteo Dei, Giulio Relini, Lidia Orsi Relini, and Fulvio Garibaldi. 2025. "Mesopelagic Fish Biodiversity in the Ligurian Cetacean Sanctuary" Diversity 17, no. 2: 97. https://doi.org/10.3390/d17020097

APA Style

Lanteri, L., Pinto, C., Palandri, G., Cima, C., Dei, M., Relini, G., Orsi Relini, L., & Garibaldi, F. (2025). Mesopelagic Fish Biodiversity in the Ligurian Cetacean Sanctuary. Diversity, 17(2), 97. https://doi.org/10.3390/d17020097

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop