A Critical Checklist of the Marine Fishes of Malta and Surrounding Waters

Abstract

A critical review of marine fishes from Malta (Central Mediterranean) recorded up to December 2022 in the technical and semi-popular literature, during the Mediterranean International Trawl Survey (MEDITS), and in commercial fisheries landings data, was undertaken with the main aim of producing a checklist of species whose occurrence in the seas around the Maltese Islands could be authenticated. This review also served to generate two other lists: one of the species whose occurrence around the islands is probable or possible but which require confirmation, and a second list of previously reported species whose occurrence was deemed highly unlikely and which were hence excluded; the reasons for such exclusion are given. A total of 412 species were confirmed as occurring in Maltese waters, 53 species were listed as requiring confirmation, and 78 species were excluded. Of the species whose occurrence around the Maltese Islands was confirmed, 370 were native; 17 were non-established aliens; seven were established aliens; three were non-established Atlantic immigrants; five were established Atlantic immigrants; nine were non-established cryptogenic; and one was an established cryptogenic. The 412 confirmed species from the Maltese Islands represent 54% of the Mediterranean fish species that have been recorded in recently published works. Therefore, considering the geographical location of the islands at the centre of the Mediterranean, they provide a presumed ideal siting for a good representation of the marine ichthyological fauna. The Maltese checklist appears to still be short of many fish species that probably occur locally and have yet to be added to the present confirmed list. Nevertheless, the present review serves as a good indication of the current situation of the Maltese fish fauna, also noting that checklists for the group from neighbouring countries are somewhat outdated and require review and updating.

1. Introduction

Fish, being mostly conspicuous, mobile animals familiar to sea users, coastal dwellers, and casual visitors and, for some species at least, having economic significance, are one of the best-known marine faunal groups. The vast literature on Mediterranean fishes, including those of the central region [1,2,3,4], means it is perhaps surprising that despite this good regional information, there is rather limited knowledge on the fishes that occur around the Maltese Islands. However, the available information suggests that the marine ichthyofauna of Maltese waters is very rich and diverse [5]. Very likely, this is partly due to the Islands’ geographical location at the centre of the Mediterranean, where there is both a transition in biogeographical characteristics from west to east and changes in these characteristics as a result of the ongoing modifications to Mediterranean hydrological conditions and to ecology resulting from global climate change [6]. The Maltese Islands also have an intermediate position in the latitudinal gradient between the European Mediterranean shores and the North African coast and are, therefore, strongly influenced by north–south biogeographical changes. Moreover, a high diversity of marine habitats characterizes Maltese marine waters, both inshore and offshore, which also contributes to the high species richness and diversity of the marine fish fauna. On the other hand, non-marine ichthyofauna is almost non-existent. As there are no lakes, rivers, streams, or lagoons on the islands, fish species associated with such habitats are absent, with a single exception, that of Aphanius fasciatus (Valenciennes), which occurs permanently in transitional waters with fluctuating salinities [7].

The bulk of the literature on Maltese fishes is popular and semi-popular in nature and, more often than not, deals with the larger inshore and epipelagic species, especially those of the fisheries importance. In some cases, the literature includes species whose occurrence is doubtful on biogeographical grounds or due to difficult taxonomy. There is some literature that approaches the subject more scientifically, focusing on taxonomy and faunistics (e.g., [8,9]) and on ecological aspects (e.g., [10,11,12]). However, cryptic and deep-water fishes have been mostly neglected. The inclusion of Malta in regional and global checklists and databases (e.g., [13]) is based on the few scientific and technical works that have been published but very often also list species whose area of distribution should include the Maltese Islands, whether they have been actually recorded or not. These and other difficulties are indicated in the brief overview of the published records for Malta that follows.

1.1. Brief Overview of Published Lists of Maltese Fish Fauna

Publications on the ichthyofauna of the Maltese Islands date back to the middle of the 18th Century when Pehr Forsskål produced the earliest known scientific list of Maltese fishes comprising 114 species [14]. During the 19th and 20th centuries, several works were published on the Maltese ichthyofauna, notably by Trapani [15], Gavino Gulia [16,17], Tagliaferro [18], Giovanni Gulia [19,20,21,22,23], and Despott [24,25].

More recently, a seminal work on Maltese ichthyology was the comprehensive illustrated catalogue of local fishes by Guido Lanfranco, published in 1958 and republished in several editions [26,27,28,29,30]; however, the 2009 edition [30] was a simplified version of the 1993 work [29] and did not include new records that were published since the previous edition. In 1996, Gerald H. Jennings published a guide to the fishes of Malta [31]; this volume, illustrated with line drawings, included many previously unrecorded species, which, however, are doubtful at best and are therefore of limited scientific value. Two books that were published at the turn of the last century were The Fishes of Malta [32] and Mediterranean Sea Fishes (Central Region) [33].

The 21st century saw the publication of a number of ichthyological papers in local and international journals, mostly focused on a particular species or groups of species (e.g., [11,34,35,36,37]). A paper on sharks and rays from Maltese waters, published in 2003 [9], was the first comprehensive critical checklist of the local elasmobranch fauna. These and other recent scientific contributions (e.g., [8,38]) comprise a valuable addition to the knowledge of the fishes which are found in Maltese waters, especially considering the recent appearance of a number of Red Sea and Atlantic immigrants, which are attributed to the warming of Mediterranean surface waters. Nevertheless, it is clear that the several doubtful records and other difficulties highlighted above necessitate an in-depth critical review of the Maltese ichthyofauna to screen out those species which do indeed occur from those whose occurrence is not authenticated.

1.2. Fisheries Data—A Valuable Source of Information on Maltese Fish Fauna

An additional source of valuable information on fish fauna is fisheries data, including both fisheries-independent and fisheries-dependent data sources. In the European Union (EU), fisheries resources are managed through the implementation of the Common Fisheries Policy (CFP; Regulation (EU) No 1380/2013). Malta has been collecting fisheries data in line with CFP requirements since joining the EU in 2004, most recently in line with the rules set out in Regulation (EU) 2017/1004 on the collection, management, and use of data in the fisheries sector and support for scientific advice regarding the CFP. Commercial fisheries data are submitted to the EU’s Joint Research Centre (JRC) on an annual basis and analysed by Expert Working Groups (EWGs) of the Scientific, Technical, and Economic Committee for Fisheries (STECF).

The Mediterranean International Trawl Survey (MEDITS) is a mandatory annual bottom trawl survey undertaken by all Mediterranean EU Member States, which collects data on the relative abundance of demersal and benthic species [39,40]. A useful reference that is routinely updated with MEDITS survey results is the ‘TM list’: a full taxonomic list of all Mediterranean species encountered in the various Geographic Sub-Areas (GSAs), including in waters surrounding the Maltese Islands (GSA 15).

In addition to the EU fisheries data collection provisions, Malta is also subject to the fisheries data collection requirements of the General Fisheries Commission for the Mediterranean (GFCM). Fisheries-related data are collected and transmitted in line with the GFCM Data Collection Reference Framework (DCRF) [41] and made publicly available on the United Nations Food and Agriculture Organisation (FAO) fisheries capture production database. GFCM expert working groups on stock assessment, marine environment, and small-scale and recreational fisheries analyse the data and provide advice to the GFCM Scientific Advisory Committee on Fisheries (SAC).

1.3. Aim of the Present Work

To address the several doubtful records and other difficulties highlighted above, the present work aimed to undertake an in-depth review of the Maltese ichthyofauna in order to screen out those species which do indeed occur around Malta from those whose occurrence is not authenticated. Specifically, the present work comprises a critical review of published records of fish from Maltese waters, from the scientific, technical, and semi-popular literature, as well as species recorded during MEDITS and in commercial fisheries landings data. The main output of the present work is a checklist of species that have been confirmed to occur in Maltese waters. In producing this list, two other lists were generated: one that provides species whose occurrence is probable or possible but for which there are no authenticated records, and a second that lists species whose occurrence is excluded based on presently available scientific knowledge. The most recent authoritative checklist remains that which was made in 1993 by Lanfranco [29]; therefore, the compilation of an updated critical checklist of fish found in Maltese waters is long overdue.

2. Methods

2.1. Study Area

The study area considered in the present review is the marine area around the Maltese archipelago, taken here to be GSA 15 as established by the GFCM in 2009 (Figure 1). Malta is located in the western Ionian Sea, more or less at the centre of the Mediterranean in the biogeographical transition zone between the western and eastern basins [42,43]. The Maltese islands present an obstacle to the general surface water exchange between the western and eastern basins of the Mediterranean, and consequently, the offshore hydrodynamic regime and other physical oceanographic characteristics are quite complex [44,45]. Inshore, there is a predominant southeast current flow that is reinforced by waves generated by the prevailing north-westerly winds [44,46]. As for most of the Mediterranean, Maltese shores are microtidal (maximum tidal range = 0.20 m), with fluctuations in the mean water level of less than 0.5 m and mainly arising from differences in atmospheric pressure [47].

Values of the sea surface temperature around the Maltese Islands typically range between 15 °C and 25 °C. However, the mean sea temperature increased by 1.9 °C during the period 1978–2020, with high values reaching 30 °C [48,49] (Malta International Airport Met Office, personal communication, 6 December 2022). Inshore salinity normally ranges between 37.1 and 37.8 ppt but may fluctuate widely in very sheltered bays and inlets and in semi-enclosed creeks [50]. Maltese coastal waters are generally oligotrophic, with levels of dissolved nitrate and phosphate not exceeding 20 µg at N/L and 0.3 µg at P/L, respectively [50].

To the north and northeast of Malta, the seabed between the Maltese Islands and southern Sicily is a vast shallow continental shelf whose depth does not exceed 200 m, with a few banks rising close to the surface, while to the southwest of Malta, bathyal depths are present relatively close to the coast since the islands are situated on the north-eastern flank of the Malta Graben: the deepest trough of the Pantelleria Rift system. The southwestern coast of the islands is characterised mainly by high cliffs, while the north-eastern coast is characterised by gently sloping shores [51].

The main habitat types in Maltese shallow (0–45 m) coastal areas are typical of the Mediterranean and include rocky shores and shallow (usually down to a depth of around 6 m) rocky infralittoral areas, which in places are covered with accumulations of boulders and/or of pebbles and cobbles, and sandy bottoms that in many places support extensive Posidonia oceanica seagrass beds down to a depth of around 45 m [52]. Extensive rocky reefs occur in several places at a depth of between 0 m and 100 m, some of which—particularly ones located several kilometres offshore—have a high ecological value in terms of habitats for fish, including species of commercial importance. Where rocky reefs are absent, the seabed within the 6–100 m depth range mainly comprises bare fine sands, which may support rhodolith beds that, in places, form a maerl bottom [53,54]. Remote operated vehicle (ROV) surveys of deep-sea (200–1000 m) areas around the Maltese Islands have indicated the presence of highly diverse habitats that include extensive rocky areas dominated by living cold-water scleractinian and gorgonian coral assemblages, a sub-fossil lithistid sponge reef, deep-water caves, and vast expanses of soft-bottoms that support a high species richness and abundance of echinoderms and crustaceans [55].

2.2. Review

A checklist of species that have been reported to occur in Maltese waters in December 2022 was compiled by critically reviewing the compilations by Lanfranco (1993), Jennings (1996), Falzon (1999), Farrugia Randon & Sammut (1999), Sammut (2001), Schembri et al. (2003), and Ragonese et al. (2013) [9,12,29,31,32,33,56]. Although the relevant pre-1950 literature [15,16,17,18,19,20,21,22,23,24,25,57] provides much useful information, the taxonomy used is outdated, not only because of changes in generic and specific allocation due to better phylogenetic knowledge and the rules of taxonomy, but also because of misidentifications and what are now known to be distinct species previously lumped together under one name. Guido Lanfranco resolved this old nomenclature to the extent possible and included records from the historical literature in his catalogues [26,27,28,29]. We, therefore, do not repeat historical records here and consider the fishes reported in Lanfranco’s earliest catalogue and subsequently.

The present authors also consulted the scientific literature dealing with records from GSA 15; data from the annual Mediterranean International Trawl Survey submitted by the Maltese fisheries authorities as required by EU fisheries data collection regulations [58,59]; and commercial fisheries landings data [60,61]. The online database ‘Fishbase’ [13] was consulted, especially on aspects of the distribution of species, and the FAO species catalogues and guides (available from the FAO FishFinder website) were consulted on aspects of species taxonomy and distribution. The nomenclature and classification of species follow the World Register of Marine Species (WORMS) (online at https://www.marinespecies.org/ (accessed on 19 December 2022)).

All species recorded from Maltese waters through these multiple data sources were then reviewed in order to classify the species into three categories: ones that are confirmed as occurring in Maltese waters, ones that may occur but whose presence requires confirmation, and those that should be excluded (Figure 2). Species records supported by actual specimens or authenticated in the scientific literature were accepted as ‘occurring’ and were included in the ‘confirmed’ list for Malta. Since Lanfranco (1993) personally verified most of the records listed in his work [29], his records were accepted as being authenticated by him except in cases where the author himself expressed doubt or in the case of species that were subsequently shown to present taxonomic problems. Where necessary, a brief explanatory note was included next to the species. For species that are historically known to have occurred but for which no recent records are available, the note ‘occurred historically but there are no recent records’ was included. For ones whose genus is known but where the species identity is doubtful, an explanatory note concerning this difficulty was included. Species commonly recorded during MEDITS in Maltese waters (GSA 15) as well as from neighbouring areas (namely, GSAs 13, 14, 16, 19, or 21; see Figure 1) were also included in the ‘confirmed’ list, even if no specimens or images were available.

Alien or other newcomer species with records from Maltese waters authenticated in the scientific literature were included as confirmed in the checklist (List A1 in Appendix A), together with an indication of their origin (Atlantic immigrant, cryptogenic, or alien) and current status (established or non-established). ‘Atlantic immigrants’ were taken to include vagrant or range-expanding species arriving in Malta autonomously; ‘alien’ species were taken as those whose presence in the Mediterranean was directly or indirectly attributable to human activities; the term ‘cryptogenic’ is used when there was doubt regarding the origin of a species, particularly for Eastern Atlantic species that are only known from single records. Species were assigned to these categories according to the criteria of Evans et al. [62].

Species were considered ‘unconfirmed’ if Malta lay within their distribution range, but their presence in Maltese waters was not authenticated through a photograph or specimen. Species that were only recorded in Maltese waters during MEDITS but not from neighbouring areas and which were not supported by actual specimens were also included in the ‘unconfirmed’ list (List A2 in Appendix A) if their presence in Malta was deemed possible based on their geographic distribution. All other species for which Malta was not in the area of occurrence and records of which were neither supported by actual specimens nor by reports in the scientific literature were considered not to be present and listed as ‘excluded’ in a separate list (List A3 in Appendix A). In all cases, justification notes for treating a species as ‘unconfirmed’ or ‘excluded’ were included in the respective lists.

Commercial fisheries landings data were also reviewed to identify any additional species recorded from Maltese waters that had not already been listed based on the scientific literature or MEDITS data. Two sources of data were used for this: (i) transversal fisheries data (i.e., data on fishing effort, weight, and value of landings) for the years 2008–2020 published by the 2021 STECF EWG on the Annual Economic Report on the EU fishing fleet [61], and (ii) the FAO GFCM (Mediterranean and Black Sea) Capture Production database for the years 1970–2019 [60]. Species with rare landings records (i.e., restricted to three years or less), with no preserved specimens, and with records lacking morphometric measurements or meristic counts were also assigned to the ‘excluded’ list.

3. Results

One species from the Petromyzonti, 62 species from the Elasmobranchii, and 349 species from the Actinopteri, were confirmed to occur or to have occurred in Maltese waters, such that the current total number of marine fish species recorded from Malta stands at 412 (see Figure 3 and List A1 in Appendix A). Of the Elasmobranchii, six species (see List A1 in Appendix A) are indicated as having occurred historically but for which no recent records are available, and one species (Squalus sp.) requires confirmation of identity and could possibly have been a new species. All the recorded Elasmobranchii species are native to the Mediterranean. Of the Actinopteri, the genus Sphyraena Artedi is present as two species, one of which is confirmed to be S. viridensis Cuvier but the other species requires confirmation of identity; the only occurring species of Elops Linnaeus requires confirmation of identity; Pagrus caeruleostictus (Valenciennes) is the confirmed species rather than Evynnis ehrenbergi (Valenciennes) which is reported as P. ehrenbergi in the literature [32,33]; a species from the genus Sargocentron Fowler requires confirmation of identity. Several of the Actinopteri are non-native species, 17 are non-established aliens, seven are established aliens, three are non-established Atlantic immigrants, five are established Atlantic immigrants, nine are non-established cryptogenic, and one is an established cryptogenic.

Seven species from the Elasmobranchii and 46 from the Actinopteri, i.e., a total of 53 fish, were assigned to the list of species whose occurrence around the Maltese Islands requires confirmation (List A2 in Appendix A). Brief justification notes for including these species in this list are given. The species requiring confirmation are mostly the Carcharinidae (5 species), Gobiidae (10 species), and Myctophidae (10 species).

Five species from the Elasmobranchii and 73 from the Actinopteri, i.e., a total of 78 fish, were assigned to the list of species whose occurrence around the Maltese Islands is excluded (List A3 in Appendix A). Brief explanatory notes that establish the fact that these species do not occur locally are given. The group with the greatest number of excluded species (20) is the family Gobiidae.

4. Discussion

The scientific, technical, and semi-popular literature and fisheries data include some 543 fish species occurring in Maltese waters; however, the present confirmed list comprises only 412 species. The critical analyses undertaken as part of the present work have removed 78 species as unlikely to occur. Some of these were recorded as a result of misidentification resulting from similarities with conspecifics, while others have been erroneously recorded without plausible justification, including some which are not even known to occur in the Mediterranean Sea. An appreciable number of species (53) may or may not occur, and their occurrence, therefore, requires confirmation or otherwise through future work. Undoubtedly, there will be a transfer of species from the ‘unconfirmed’ list to the confirmed one, thereby expanding the checklist of fishes from Maltese waters. Such additions to the Maltese checklist are predicted to result from new records of fishes from deep waters, species for which to date no specimen has yet been available for proper identification, and newly recorded non-native species, which up to 2021 have reached a total of 168 for the Mediterranean [63].

Lanfranco’s checklist of Maltese fish species [29], which the present authors deemed the most reliable of all the locally published lists, includes 288 species that are confirmed through the present work. The 124 species added to the confirmed list through the present work mostly comprise native Mediterranean fishes that were recorded from Malta subsequent to the publication of Lanfranco’s 1993 work, although 32 of them are non-native and cryptogenic species, and eight are recent Atlantic immigrants. Amongst the 42 newcomer species included in the present confirmed list, only Alepes djedaba Forsskål and Stephanolepis diaspros Fraser-Brunner were recorded by Lanfranco (1993) [29]; the rest are all more recent additions to the Maltese ichthyofauna.

In their evidence-based checklist, Kovačić et al. listed a total of 759 fish species from the Mediterranean Sea [63]. The 412 confirmed species from the present work represent 54% of the Mediterranean marine fish species recorded by Kovačić et al. [63]. The total number of fish species that were confirmed as occurring in Maltese waters was broadly similar to that recorded from other sub-regions of the Mediterranean in recent checklists: Albania—262 species, Libya—304, Egyptian Mediterranean—364, Lebanon—376, northern Tyrrhenian Sea—426, Turkish Levantine Sea—441, Adriatic Sea—444, southern Tyrrhenian Sea—447, Turkish Aegean Sea—449, Ligurian Sea—454, Israel—469, Spanish Mediterranean—498 [64,65,66,67,68,69,70,71,72].

The Mediterranean checklist by Kovačić et al. [63] indicates that the highest number of species among the Elasmobranchii are from the Carcharhinidae (44 species), Rajidae (19 species), and Dasyatidae (7 species). The number of species from the Carcharhinidae reported by these workers far exceeds that recorded by the present work (two species), but, on the other hand, the number of species recorded by the same authors for the Rajidae and Dasyatidae species is, arguably, close to those from the present checklist; fourteen and three species, respectively. For the Actinopteri, Kovačić et al. [63] indicated that the greatest number of species were from the Gobiidae (74 species), Sparidae (32 species), Blenniidae (24 species), Labridae (22 species), Carangidae (21 species) and Serranidae (21 species). For this Class, the number of species recorded from the present work is not much different for the Sparidae (24 species), Blenniidae (17 species), Labridae (17 species), Carangidae (15 species), and Serranidae (15 species). However, for the Maltese Gobiidae, the number of confirmed species from Malta is much lower (21 species). It appears, therefore, that the occurrence of species that are an important component of the local fisheries sector has been well reported, while information on species that are not landed by fishers, such as Carcharhinidae and Gobiidae, is lacking due to the unavailability of specimens. This reflects the difficulty of confirming the identity of species when actual specimens are unavailable; identification based on indirect information (imagery, observations made by third parties, etc.) often leads to erroneous identification. Even for species that are quite common in the fisheries sector, such as the barracudas, unavailability of specimens has resulted in uncertainty as to which species occur. The Blennidae are an exception to this, as it seems that most Mediterranean species from this group have been recorded from Malta; this can be attributed to the particular effort expended by Falzon [56] in surveying fishes from this family around the Maltese Islands.

The present critical review has resulted in the most extensive list of Maltese fishes published to date. An assessment of the Maltese fish fauna within the context of biogeographical affinities was beyond the scope of the present study, although the present authors intend to follow on this in separate future work. Three lists, one with 412 confirmed species, a second with 53 species that require confirmation, and a third comprising 78 species that are deemed not to occur in Maltese coastal waters, have been generated.

These lists are expected to be useful for local conservation and fishery management by contributing data on the distribution of fish at the Mediterranean regional level. The checklists are useful tools for fisheries scientists when compiling and checking data from fisheries surveys and catch monitoring, for instance, during the annual review of the MEDITS TM list. The lists also highlight gaps in knowledge that need to be addressed and, as such, can be used as a starting point for future research. For example, the collection of samples for some of the more commonly encountered unconfirmed species, such as Myctophidae and Sphyraenidae, during MEDITS surveys and fish market monitoring could be prioritized.