Fishes, Volume 9, Issue 12 (December 2024) – 5 articles

Live transportation is a critical component of fish farming and hatchery release. To optimize hatchery-release techniques and improve the survival rate of marbled rockfish (Sebastiscus marmoratus, Cuvier 1829) juveniles, the effects of varying transport durations (2, 4, 6, and 8 h) and densities (60, 90, 120, and 150 kg m⁻³) on the physiological indicators of the fish and water quality were investigated under controlled laboratory conditions. We found that as transport duration and density increased, water quality significantly deteriorated, with ammonia nitrogen levels rising and dissolved oxygen content and pH levels decreasing. Physiological indicators including levels of lactate, cortisol, and malondialdehyde and activities of superoxide dismutase, alkaline phosphatase, and glutamate oxaloacetate transaminase notably increased, indicating that the fish experienced heightened stress during transport. Additionally, the mortality rate of juveniles increased significantly with increasing density and transport duration. The high mortality rate might be associated with sustained elevated cortisol levels and liver damage. Our results are helpful for determining the optimal transport conditions for S. marmoratus juveniles and also provide valuable insights for improving transport techniques for other aquatic animal species. Full article

In this study, to investigate the quality of wild and farmed frozen southern bluefin tuna, physicochemical analyses and sensory evaluations were conducted. Principal component analysis was then performed using the results obtained to examine the correlation between the bluefin tuna’s taste characteristics and physicochemical properties. The sensory evaluation suggested differences in texture and acidity between wild and farmed fish, whereas the principal component analysis indicated differences in fatty acid and amino acid composition. Wild fish contained higher levels of docosahexaenoic acid and monounsaturated fatty acids, while farmed fish had higher levels of saturated fatty acids. Regarding free amino acids and dipeptides, wild fish had higher levels of anserine and alanine, whereas farmed fish showed higher levels of glutamine and histidine, and acidity was observed in farmed fish. Furthermore, based on the results of the principal component analysis, it was inferred that the content of inosinic acid, which is considered an umami component in fish, may have a low impact on palatability. These factors were suggested to influence the differences between wild and farmed tuna. Full article

According to EuroStat data, the recorded landings of fisheries products from European waters were estimated at about 6 million tons in 2001, down to 3.2 million tons in 2022. This gradual decline slowed after the entering into force of the reform of the European Common Fisheries Policy (CFP) at the end of 2013, but was followed by a steeper decline after 2018. This is reflected in the last assessment of the Scientific Technical and Economic Committee for Fisheries (STEPF), noting that despite progress in the NE Atlantic management, 41% of the assessed stocks in 2022 were outside safe biological limits, down from 80% in 2003. Improvements in the Mediterranean are significantly slower. A warming ocean provokes the measurable poleward migration of species and adds stress to predator–prey relations in all European seas. Within this general picture, the broad-brush landscape is influenced by policy applications more in favour of industrial exploitation and regulatory and market environments, making it very hard for many small-scale fishers (SSFs) to remain in business, let alone attract younger successors for generational transition. In crowded marine spaces, it is a challenge to allocate access rights fairly between fisheries, exclusion zones for resource and habitat protection and much-needed ecosystem recovery, platforms for fossil exploitation, wind farms, underwater cables and recreational uses. Two examples of local initiatives with faunal recovery potential in the Mediterranean are briefly presented as a bottom-up complement to more top-down management approaches. They are spearheaded by artisanal fishers, who seek to restore spawning grounds and other coastal habitats as a way to procure enough fish and other complementary activities to secure their livelihoods in the future. They are supported by local scientists and nature conservation organisations. While promising, this is still rather the exception. Here, it is argued that trust-building between artisanal fishers, conservationists and scientists, and greater systemic support to SSFs by governments, increase chances for the urgently needed structural shifts that deliver the reversal in the ongoing decline in biodiversity and ocean productivity that all aspire to, to ensure sustained social and economic benefits. Full article

Portuguese oyster (Magallana angulata) is one of the most important shellfish species worldwide. Although significant improvements in growth have been achieved through artificial selection breeding, the genetic basis underlying these traits remains unclear. Thus, this study aimed to (i) estimate variation and heritability for growth-related traits and (ii) identify SNPs and candidate genes associated with growth traits in Portuguese oyster. Five growth-related traits, including shell height (SH), shell length (SL), shell width (SW), whole weight (WW), and soft tissue weight (STW), were measured and analyzed in 114 one-year-old individuals from a cultivated population in Fujian Province, China. Through whole-genome sequencing and genotyping, we obtained 8,183,713 high-quality SNPs. Based on the genomic relationship matrix, heritability for the five traits was estimated, ranging from 0.071 to 0.695. Through genome-wide association analysis (GWAS), a total of nine SNPs were identified as significantly or suggestively associated with one of the growth-related traits, each explaining phenotypic variation ranging from 14.13% to 18.56%. Differentially expressed genes (DEGs) between individuals with extreme phenotypes were identified using comparative transcriptome analysis, ranging from 868 to 2274 for each trait. By combining GWAS and comparative transcriptome analysis, a total of seven candidate genes were identified, with biological functions related to growth inhibition, stress response, cell cycle regulation, and immune defense. The associations between the candidate genes and the growth-related traits were validated by using single-marker association analysis in other populations. Based on SNPs in these candidate genes, 16 haplotypes associated with growth-related traits were obtained. This study contributes to a deeper understanding of the genetic mechanisms of growth traits, and provides a theoretical basis and genetic markers for the breeding of fast-growing strains of the Portuguese oyster. Full article