Sebastes Mentella Research Articles

Drivers of growth in strong year classes of the deepwater redfish (Sebastes mentella) population from the Gulf of St. Lawrence derived from otolith increment-based growth chronologies.

The case of the deepwater redfish (Sebastes mentella) in the Gulf of St. Lawrence (GSL) is a compelling example of drastic fluctuations in annual recruitment strength, characteristic of spasmodic stocks. After three decades of low abundance, the emergence of three consecutive strong year classes in 2011-2013 resulted in an unprecedented increase in biomass. In spasmodic stocks such as GSL redfish, strong year classes sustain both the biomass and catch for decades. Therefore, understanding the growth dynamics of these cohorts is essential. In the present study, we reconstructed the annual growth rates of redfish using otolith increment-based annual chronology and investigated the drivers of growth variation in redfish strong year classes of the early 2010s and early 1980s. Stock biomass was identified as the main extrinsic driver of redfish growth, suggesting intense competition for food at high conspecific density. Warming of deep waters in the GSL, where adult redfish settle, positively correlated with individual growth. However, recent warming of the cold intermediate layer showed a negative correlation with redfish growth, likely related to the shrinking of the habitat this water mass provides for various redfish cold-water prey rather than to a direct effect of temperature. Reconstruction of redfish annual growth trajectories from birth to capture emphasized the importance of carryover effects in the growth potential of strong year classes. This work provided an important first outlook of the factors driving growth variation in GSL redfish spasmodic stock and explored midterm consequences of density-dependent pressures on biological parameters of the population.

Reduction in size-at-maturity in unprecedentedly strong cohorts of redfish (Sebastes mentella and S. fasciatus) in the Gulf of St. Lawrence and Laurentian Channel.

Life-history traits, such as size-at-maturity, are key parameters to model population dynamics used to inform fisheries management. Fishery-induced evolution, density-dependent effects, and global warming have been shown to affect size- and age-at-maturity, and resulting spawning stock biomass (SSB) in a wide range of commercial fish stocks. Marked changes in redfish biomass and environmental conditions in the Gulf of St. Lawrence and Laurentian Channel over the past decade called for a review and update of size-at-maturity for commercially important deepwater redfish Sebastes mentella and Acadian redfish Sebastes fasciatus stocks. Following a 25-year moratorium, local redfish biomass has recently reached unprecedented levels, co-occurring with an overall warming of bottom water temperatures. Our objectives were (1) to perform a histological assessment of redfish reproduction stages, including the validation and fine-tuning of a robust visual chart to facilitate monitoring of size-at-maturity and SSB in a transforming environment, and (2) to evaluate changes in size-at-maturity in unprecedentedly strong cohorts of redfish, and consequences for stock status assessment and fisheries management. Each specimen was genetically identified to species, and gonad reproduction stages were determined by histology and macroscopic appearances. The present study enabled a robust visual chart for continued and cost-effective monitoring of redfish reproduction stages to be refined and validated, and has shown a large decrease in redfish length when 50% of the individuals are considered mature that led to an increase in estimates of SSB during the 2011-2021 period for S. mentella and S. fasciatus. These changes modified the perception of stock status, thus having significant implications for fisheries management. Given that fishery-induced evolution and community structure changes along with global warming are affecting numerous stocks worldwide, the present study outlines a major and global challenge for scientists and resources managers. As shown by our results, the monitoring and frequent updates of life-history traits in transforming environments are needed to provide reliable science advice for sustainable fisheries.

Organic UV absorbents in the deepwater redfish (Sebastes mentella) from the St. Lawrence Estuary and Gulf: Distribution and human health risk assessment

UV absorbents (UVAs), such as organic UV filters (UVFs) and benzotriazole UV stabilizers (BZT-UVs), are used in a wide range of consumer and industrial products and they are contaminants of emerging concern in the environment. However, their occurrence and fate in the deep-sea environments are inadequately understood. This study investigated the occurrence and distribution of five UVFs and ten BZT-UVs in the muscle (n = 127) of 2019-collected deepwater redfish (Sebastes mentella) from the St. Lawrence Estuary and Gulf (SLEG) (Canada) to better understand the accumulation of these contaminants in deep-sea fish. Small redfish (<30 cm) tended to have higher concentrations of UVAs in the muscle than that of larger specimens (>30 cm). The UVF 2-hydroxy-4-methoxybenzophenone (BP3) was the most frequently detected (present in 34 % of all samples) target UVA, with concentrations as high as 413 ng/g (dry weight). According to the δ15N and δ13C data, pelagic-eating redfish, and individuals with lower trophic levels had higher lipid content and accumulated more BP3 in their muscles. Four BZT-UVs were detected in redfish muscle, but the detection frequency was lower than 30 %. The estimated hazard quotient for these contaminants was <2.3 × 10−2 for general Canadian populations, indicating that they are unlikely to pose health risks to humans through redfish consumption. Factors influencing UVAs bioaccumulation in redfish, as well as the effects UVAs may have on deep-sea species, should be researched further.

Spatial distribution and speciation of mercury in a recovering deepwater redfish (Sebastes mentella) population from St. Lawrence Estuary and Gulf, Canada

Mercury (Hg) pollution poses a significant threat to the environment, particularly in the form of methylmercury (MeHg). However, little is known about the distribution and influencing factors of Hg in deep-sea (>200m) fish, which is crucial for assessing potential health risks to fish and humans. In Canada, the deepwater redfish (Sebastes mentella) has been designated as an endangered species. After a 25-year fishing moratorium, the redfish population in the St. Lawrence Estuary and Gulf is recovering, and resuming of commercial fishing and human consumption are expected. This study aimed to investigate the distribution of MeHg and total Hg (THg) in the muscle of redfish, as well as the factors influencing its distribution, and to assess the potential human health risks associated with redfish consumption. The redfish samples (n = 123) were collected by Fisheries and Oceans Canada in 2019. The concentrations of THg and MeHg in redfish muscle were determined to be 93.3 ± 183 ng/g (mean ± SD, wet weight) and 78.2 ± 149 ng/g, respectively. Large redfish (>30 cm) accumulated 20 to 30 times more Hg than small redfish (17–30 cm). Small redfish from the Estuary-Western Gulf had higher levels of MeHg and THg than those from the Laurentian Channel and the Northeast Gulf, but the Hg availability to redfish among the three areas were similar. Significant predictors of MeHg concentrations in redfish muscle were determined to be fish length, muscle moisture, δ15N, and N%. MeHg consumption by the general population with an average fish consumption rate is not anticipated to have adverse effects. This study establishes a baseline for future Hg monitoring in the deep water environments in this region. Further research is required to elucidate the cause-effect relationships between various environmental/biological parameters and Hg accumulation in deep-sea biota.

The Barents and Norwegian Seas beaked redfish (Sebastes mentella): stock assessment and fishery management

An analytical review of the stock assessment and fishery regulation of the Barents and Norwegian Seas beaked redfish is presented. Model estimates of stock dynamics are characterized by uncertainty associated with incomplete coverage of the beaked redfish distribution in surveys, age determination problems, and assumptions made in the model. The regulation of fishing mortality is based on the precautionary approach, and the main management aim is achievement of the maximum sustainable yield. Technical measures include limiting the minimum mesh size in the trawl, establishing a minimum fish length for fishery, temporal fishery closures and limiting by-catch in multi-species fisheries. The unregulated fishery of the Norwegian-Barents Sea beaked redfish in the 1970s was one of the reasons for the decline in its stock and appearance of poor recruitment, which led to the ban on its targeted fishing in the Norwegian Economic Zone and in the fish protection area of the Svalbard. In 2014, the fishing was reopened. At present, the stock of beaked redfish of the Norwegian-Barents Sea population is in a safe state and further growth of the catch is expected.

Ecological-parasitological method in studies of population biology of beaked redfish &lt;i&gt;Sebastes mentella&lt;/i&gt; (Scorpaeniformes: Sebastidae) in the Irminger Sea

The results of the analysis of the data set obtained in course of long-term studies of the population biology of beaked redfish Sebastes mentella are used as an interdisciplinary approach in the study of its geographical, biotopic, ontogenetic and phylogenetic features, population structure in the pelagic zone of the Irminger Sea and the adjacent bathyal zone of Greenland and Iceland. The approach is based on the ecological-parasitological method, which involves the use of data on the composition of parasite communities and the occurrence of their individual species as biomarkers for understanding the features of the hydrobionts ecology. The results obtained, which include information on the spatial distribution, functional subdivision of the area, ontogenetic migrations, maturation and growth rate, underwater marking, phenetic, genetic and other features of beaked redfish, made it possible to identify the conditions for divergent formation and significant isolation of its pelagic and benthic groupings, constituting the North Atlantic population. The colonization by this species of great depths of the oceanic pelagial and the near-bottom layer of the bathyal, accompanied with an increase in the rate of sexual maturation and migratory activity in the pelagial, characterizes the direction of the current stage of its phylogenesis. The unity of the pelagic grouping of beaked redfish in the vast water area and throughout the depth of its distribution in the Irminger and Labrador seas is substantiated. It is shown that significant differences in infestation rate between males and females of beaked redfish, stable in time and space, with the only species-specific parasite (the copepod Sphyrion lumpi), serve as a phene of the pelagic grouping of the North Atlantic population of the host.

Contaminants reach everywhere: Fish dietary samples should be surface decontaminated prior to molecular diet analysis.

Knowledge of trophic interaction is necessary to understand the dynamics of ecosystems and develop ecosystem-based management. The key data to measure these interactions should come from large-scale diet analyses with good taxonomic resolution. To that end, molecular methods that analyze prey DNA from guts and feces provide high-resolution dietary taxonomic data. However, molecular diet analysis may also produce unreliable results if the samples are contaminated by external sources of DNA. Employing the freshwater European whitefish (Coregonus lavaretus) as a tracer for sample contamination, we studied the possible route of whitefish in beaked redfish (Sebastes mentella) guts sampled in the Barents Sea. We used whitefish-specific COI primers for diagnostic analysis, and fish-specific 12S and metazoa-specific COI primers for metabarcoding analyses of intestine and stomach contents of fish samples that were either not cleaned, water cleaned, or bleach cleaned after being in contact with whitefish. Both the diagnostic and COI metabarcoding revealed clear positive effects of cleaning samples as whitefish were detected in significantly higher numbers of uncleaned samples compared to water or bleach-cleaned samples. Stomachs were more susceptible to contamination than intestines and bleach cleaning reduced the frequency of whitefish contamination. Also, the metabarcoding approach detected significantly more reads of whitefish in the stomach than in intestine samples. The diagnostic analysis and COI metabarcoding detected contaminants in a higher and comparable number of gut samples than the 12S-based approach. Our study underlines thus the importance of surface decontamination of aquatic samples to obtain reliable diet information from molecular data.

Spatiotemporal variability in otolith elemental fingerprint and the potential to determine deepwater redfish (Sebastes mentella) origins and migrations in the Estuary and Gulf of St. Lawrence, Canada

Connectivity processes have major implications in defining the resiliency of fish populations to overexploitation. A preliminary estimate of population exchange rates can be done by identifying the natal origin of adult fish. In this study, otolith elemental fingerprints were used as natural marker of origins and movements of Deepwater redfish (Sebastes mentella) in the Gulf of St. Lawrence (GSL). We specifically targeted the strong 2011–2013 cohorts that supported the rapid recovery of the GSL stock after its collapse in the 1990s. Elemental fingerprints were extracted from the core (proxy for larval origin) and edge (proxy for capture location) of otoliths using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). We observed an East to West gradient in the multi-elemental fingerprint of the otolith edge in the GSL, as well as evidence of temporal variation between 2016 and 2018. Cluster analysis of the core fingerprint revealed the existence of two chemically distinct natal sources of variable contribution between the Saguenay Fjord, the western GSL and the eastern GSL. This new insight on the population structure of redfish in the GSL at an ecologically relevant scale constitutes important knowledge for the assessment and sustainable management of a key recovering resource.

Feeding ecology of redfish (Sebastes sp.) inferred from the integrated use of fatty acid profiles as complementary dietary tracers to stomach content analysis.

In the northern Gulf of St. Lawrence (nGSL), redfish (Sebastes mentella and Sebastes fasciatus combined) are at record levels of abundance following the strong recruitment of three consecutive cohorts in 2011-2013 and have become by far the most abundant demersal fish in the region. Understanding redfish trophic relationships is essential for the effective management and conservation of species in the nGSL ecosystem. To date, description and quantification of redfish diet in the region have been restricted to conventional stomach content analysis (SCA). Using analysis of fatty acid (FA) profiles as complementary dietary tracers, the authors conducted multivariate analyses on 350 livers of redfish which were collected in combination with stomach contents during a bottom-trawl scientific survey in August 2017. The predator FA profiles were compared to those of eight different redfish prey types identified as dietary important with SCA. Results suggested similitude between SCA and FA results, with zooplankton prey being more related to small (<20 cm) and medium (20-30 cm) redfish (16:1n7, 20:1n?, 22:1n9 and 20:5n3) than large (≥30 cm) ones, whereas shrimp prey seemed more related to large redfish size classes (18:2n6 and 22:6n3) relative to the small and medium ones. Although the SCA offers a glimpse in the diet only based on the most recently consumed prey, analysis of FA profiles provides a mid-term view indicating pelagic zooplankton consumption on calanoid copepod and confirming high predation pressure on shrimp. This study constitutes the first attempt of combining FA with SCA to assess the diet of redfish, highlights the benefits of FA as a qualitative tool and suggests improvements for future studies.

Natural mortality estimations for beaked redfish (Sebastes mentella) – A long-lived ovoviviparous species of the Northeast Arctic

Beaked redfish (Sebastes mentella) is one of the few commercially important fish species producing living offspring. Like many other deep-water fishes, it is slow growing, late maturing and long-lived, getting as old as 65 years or even 75 years in some populations. The stock in the Norwegian and Barents Seas is analytically assessed since 2012, assuming a natural mortality (M) of 0.05 yr−1 across all ages, based on Hoenig’s longevity related estimator. Since then, several reviews and new studies have been published, affording a re-evaluation of the natural mortality in the assessment model. We estimated natural mortality of beaked redfish using 48 different estimators in two categories, either estimating M across the population or dependent on age, length or weight. The obtained estimates were highly variable, ranging from 0.01 to 0.32 yr−1 for estimates across the population, and 0.05–0.62 yr−1 for age or size dependent median-M. These wide ranges demonstrate the sensitivity of SSB to the input parameters as well as the pitfalls of using estimators developed for distant taxa. Of the 48 estimates, 20 were considered as potential candidates for updating the stock assessment model, yet not all of these were realistic. The frequency distribution of the estimators showed a peak around a value of 0.07 yr−1, lowering the estimated spawning stock biomass in the last year by about 300 kt but keeping it above the precautionary reference point for the stock. Estimators across the life-history of beaked redfish indicate a potential underestimation of natural mortality for early and overestimation for late age classes. Age and size related estimators are promising for the older ages but tend to extreme estimates for the early ages, which deserves further investigation.

Some Features of the Blood Cellular Composition and Histology of Muscles of Female and Male Beaked Redfish (Sebastes mentella)

Some Features of the Blood Cellular Composition and Histology of Muscles of Female and Male Beaked Redfish (Sebastes mentella)

Diet composition of redfish (Sebastes sp.) during periods of population collapse and massive resurgence in the Gulf of St. Lawrence

Redfish (Sebastes mentella and S. fasciatus) are back at spectacular record high levels in the Gulf of St. Lawrence (GSL) and the effects of this massive resurgence on other components of the food web remain largely unknown. To better understand the trophic implications of the surging redfish biomass within the GSL ecosystem, 3,690 stomachs containing food were collected during two periods: one characterised by low redfish abundance (1993–1999) and the other during a period of record abundance (2015–2019). Taxonomical analysis of stomach contents from individuals of different sizes from three subareas of the GSL was carried out to determine diet composition during both periods. Zooplankton represented the main prey category for small redfish (&amp;lt; 20 cm), which was driven by a predation on amphipods, mostly Themisto sp. in North-East Gulf, in the 1990s and on copepods of the genus Calanus in the deep channels and euphausiids in North-West Gulf in the 2010s. Themisto sp. still dominated the diet of medium (20–30 cm) redfish in the 1990s while the copepods were predominant during the 2010s. Shrimp consumption increased with redfish size and two species were particularly important in large redfish diet (≥ 30 cm) during both periods: pink glass shrimp (Pasiphaea multidentata), mostly in the Laurentian Channel and northern shrimp (Pandalus borealis), especially in North-East Gulf. Redfish predation on shrimp represents a major concern for the dynamics of the northern shrimp which supports a valuable fishery in the GSL but has been declining in abundance since several years. Piscivory was observed in large redfish diet, with capelin (Mallotus villosus) being the major fish prey in the 1990s and redfish (cannibalism) in the 2010s, suggesting density-dependent control at high density of small redfish. By presenting a detailed overview into the redfish diet composition and its temporal variability, the present study offers a first look into the possible future trophic impacts of a resurging groundfish in the GSL ecosystem.

Warm and cold temperatures limit the maximum body length of teleost fishes across a latitudinal gradient in Norwegian waters

As the majority of marine organisms are water-breathing ectotherms, temperature and dissolved oxygen are key environmental variables that influence their fitness and geographic distribution. In line with the temperature-size rule (TSR), marine ectotherms in warmer temperatures will grow to a smaller maximum body size, yet the extent to which different species experience this temperature-size response varies. Here, we analysed the maximum body length of ten teleost fish species in line with temperature, dissolved oxygen concentration and geographic location (that encompasses multiple latent variables), across a broad (26°) latitudinal gradient throughout Norwegian waters. Our results showed that the two largest study species, spotted wolffish (Anarhichas minor) and cusk (Brosme brosme), display the strongest negative temperature-size response. We also observed smaller maximum body lengths for multiple species within the coldest extent of their temperature range, as well as parabolic relationships between maximum length and temperature for Atlantic wolffish (Anarhichas lupus) and beaked redfish (Sebastes mentella). The smaller maximum body lengths for high latitude species at both warm and cold temperature extremes of species’ thermal ranges corroborate the temperature-size mechanisms of the gill-oxygen limitation theory (GOLT), whereby spontaneous protein denaturation limits growth at both warm and cold temperatures.

Northwest Atlantic redfish science priorities for managing an enigmatic species complex

Redfish ( Sebastes spp.) in the Northwest Atlantic (NWA) extend from Baffin Island in the north to the Gulf of Maine in the south. The two most abundant species are Sebastes mentella and Sebastes fasciatus, which are morphometrically similar and difficult to visually distinguish. Redfish are long-lived, slow-growing, late-maturing, tend to produce large year classes episodically, and have complex population structure. Intraspecific genetic groups are abundant in the NWA. They are often semipelagic and patchily distributed, which makes them difficult to survey. These are all characteristics that cause difficulties for stock assessment and for sustainable fisheries management. This was the focus of The Ocean Frontier Institute Northwest Atlantic Redfish Symposium in 2018. In this paper, we synthesize the information known about NWA redfish. To improve the scientific basis for sustainable harvest strategies, key research recommendations involve (1) improved biological sampling including species and ecotype; (2) developing integrated stock assessment models; (3) developing harvest strategies with management reference points that are appropriate for redfish; (4) improving fishing technology and practices to avoid capture of small nonmarketable redfish and other species.

Using gene expression to identify the most suitable environmental conditions for growth and metabolism of juvenile deepwater redfish (Sebastes mentella) in the Estuary and the Gulf of St. Lawrence

Abstract Deepwater redfish Sebastes mentella will be among the most important resource-sustaining commercial bottom-fish fisheries in the years to come in the Estuary and Gulf of St. Lawrence (EGSL). In 2011, 2012, and 2013, three strong cohorts were recruited to the stock; their abundance in 2018 was 80 times higher than that of the 1993–2012 period. The main goal of this work was to deepen our knowledge of their growth regulation and metabolism in order to identify molecular indicators and determine how they are influenced by natural environmental conditions. Fish weight and water temperature explained 11% of the variation in relative mRNA levels of specific gene targets in liver and muscle among seven sites where deepwater redfish were captured in the EGSL. The relative expression of liver insulin-like growth factor-1 (igf-1) and white muscle A-chain lactate dehydrogenase (ldh-a) correlate positively with weight, whereas heavy chain muscle myosin (myo), heart citrate synthase (cs), and white muscle pyruvate kinase (pk) correlate negatively. The relative expression of heart cytochrome c oxidase subunit 1 (cox-1) and white muscle igf-1 receptor isoform a (igf-1ra) correlate negatively with temperature. Deepwater redfish from the estuary were smaller than those caught at other sites. Since the growth potential of deepwater redfish was strongly correlated with temperature (being enhanced by higher temperatures), this study suggests an ecological advantage for this species in a climate-warming context.

Comparative Analysis of Lipids and Fatty Acids in Beaked Redfish Sebastes mentella Travin, 1951 Collected in Wild and in Commercial Products

The lipid and fatty acid profile of muscles in beaked redfish, caught and fixed in the wild versus specimens from food supermarkets (“commercial”), were evaluated, as well as the health implications of this popular food for its consumers based on the calculation of nutritional quality indexes. The contents of the total lipids (TLs), total phospholipids (PLs), monoacylglycerols (MAGs), diacylglycerols (DAGs), triacylglycerols (TAGs), cholesterol (Chol), Chol esters, non-esterified fatty acids (NEFAs), and wax esters were determined by HPTLC; the phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC), and lysophosphatidylcholine (LysoPC) were determined by HPLC; and fatty acids of total lipids were determined using GC. The TL content was higher in commercial products due to DA and NEFAs, among PL fractions the content of LysoPC was also higher. The results indicated multidirectional processes of slight degradation of lipids in commercial products in comparison to wild. The flesh lipid quality index was lower due to EPA and DHA in commercial specimens while the index of thrombogenicity was significantly higher. The differences in the quantities of lipid classes between muscle biopsy regions in fish apparently corroborate the morphology and physiology of deep-water fish.

Hierarchical genetic structure in an evolving species complex: Insights from genome wide ddRAD data in Sebastes mentella.

The diverse biology and ecology of marine organisms may lead to complex patterns of intraspecific diversity for both neutral and adaptive genetic variation. Sebastes mentella displays a particular life-history as livebearers, for which existence of multiple ecotypes has been suspected to complicate the genetic population structure of the species. Double digest restriction-site associated DNA was used to investigate genetic population structure in S. mentella and to scan for evidence of selection. In total, 42,288 SNPs were detected in 277 fish, and 1,943 neutral and 97 tentatively adaptive loci were selected following stringent filtration. Unprecedented levels of genetic differentiation were found among the previously defined ‘shallow pelagic’, ‘deep pelagic’ and ‘demersal slope’ ecotypes, with overall mean FST = 0.05 and 0.24 in neutral and outlier SNPs, respectively. Bayesian computation estimated a concurrent and historical divergence among these three ecotypes and evidence of local adaptation was found in the S. mentella genome. Overall, these findings imply that the depth-defined habitat divergence of S. mentella has led to reproductive isolation and possibly adaptive radiation among these ecotypes. Additional sub-structuring was detected within the ‘shallow’ and ‘deep’ pelagic ecotypes. Population assignment of individual fish showed more than 94% agreement between results based on SNP and previously generated microsatellite data, but the SNP data provided a lower estimate of hybridization among the ecotypes than that by microsatellite data. We identified a SNP panel with only 21 loci to discriminate populations in mixed samples based on a machine-learning algorithm. This first SNP based investigation clarifies the population structure of S. mentella, and provides novel and high-resolution genomic tools for future investigations. The insights and tools provided here can readily be incorporated into the management of S. mentella and serve as a template for other exploited marine species exhibiting similar complex life history traits.

Into the Deep: New Data on the Lipid and Fatty Acid Profile of Redfish Sebastes mentella Inhabiting Different Depths in the Irminger Sea.

New data on lipid and fatty acid profiles are presented, and the dynamics of the studied components in muscles in the males and females of the beaked redfish, Sebastes mentella, in the depth gradient of the Irminger Sea (North Atlantic) is discussed. The contents of the total lipids (TLs), total phospholipids (PLs), monoacylglycerols (MAGs), diacylglycerols (DAGs), triacylglycerols (TAGs), cholesterol (Chol), Chol esters, non-esterified fatty acids (NEFAs), and wax esters were determined by HPTLC; the phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC), and lysophosphatidylcholine (LPC) were determined by HPLC; and fatty acids of total lipids were determined using GC. The Chol esters prevailed in muscles over the storage TAGs, and the wax ester content was high, which is a characteristic trait of vertically migrating species. Specific dynamics in certain PL in redfish were found to be depended on depth, suggesting that PLs are involved in the re-arrangement of the membrane physicochemical state and the maintenance of motor activity under high hydrostatic pressure. The high contents of DHA and EPA were observed in beaked redfish muscles is the species’ characteristic trait. The MUFAs in muscles include dietary markers of zooplankton (copepods)—20:1(n-9) and 22:1(n-11), whose content was found to be lower in fish sampled from greater depths.

New Data on the Distribution of Beaked Redfish Sebastes mentella (Sebastidae) in the Greenland Sea

The ichthyological studies carried out at the shelf of North-Eastern Greenland in 2002–2017 new regions of dwelling of beaked redfish Sebastes mentella were discovered. It is shown that the distribution of underyearlings is not limited to the European shelf, but extends much further to the west, to the deep-water part of the Fram Strait. Juvenile individuals of beaked redfish constantly occur off North-Eastern Greenland, where the branches of the Gulf Stream reach its shelf, and further south to the area of the formation of a circular current in the eastern part of the Greenland Sea and western the Norwegian Sea. It is likely, that this cyclonic system and the cold Greenland Current are an integral part of the feeding and migratory path of larvae, juvenile specimens and adult beaked redfish to the area of its reproduction on the European shelf, as well as in the Irminger Sea.

Population genomics and history of speciation reveal fishery management gaps in two related redfish species (Sebastes mentellaandSebastes fasciatus).

Understanding the processes shaping population structure and reproductive isolation of marine organisms can improve their management and conservation. Using genomic markers combined with estimation of individual ancestries, assignment tests, spatial ecology, and demographic modeling, we (i) characterized the contemporary population structure, (ii) assessed the influence of space, fishing depth, and sampling years on contemporary distribution, and (iii) reconstructed the speciation history of two cryptic redfish species, Sebastes mentella and S. fasciatus. We genotyped 860 individuals in the Northwest Atlantic Ocean using 24,603 filtered single nucleotide polymorphisms (SNPs). Our results confirmed the clear genetic distinctiveness of the two species and identified three ecotypes within S. mentella and five populations in S. fasciatus. Multivariate analyses highlighted the influence of spatial distribution and depth on the overall genomic variation, while demographic modeling revealed that secondary contact models best explained inter‐ and intragenomic divergence. These species, ecotypes, and populations can be considered as a rare and wide continuum of genomic divergence in the marine environment. This acquired knowledge pertaining to the evolutionary processes driving population divergence and reproductive isolation will help optimizing the assessment of demographic units and possibly to refine fishery management units.