Beaked Redfish Research Articles

The Evolution of Redfishes of the Genus <i>Sebastes</i> (Perciformes: Sebastidae) of the Atlantic and the Arctic Oceans: Budding Speciation in the Species Flock

The evolutionary history of North Atlantic Sebastes redfishes was reconstructed as a result of studying the mitochondrial DNA D-loop sequences of Sebastes redfishes inhabiting the North Atlantic and the Arctic Oceans. It was shown, that speciation of these redfishes occurred in several stages. During the first stage, the ancestor of Norway redfish (S. viviparus) diverged from the common ancestor species in the process of allopatric speciation. Ancestor of Acadian redfish (S. fasciatus) diverged from the common ancestor as it evolved. Budding speciation in the species that would later evolve into golden redfish (S. norvegicus) resulted in emergence of beaked redfish (S. mentella). Paleoclimatic events seem to have played the key role in species divergence as they caused habitat fragmentation allowing the isolated groups to become genetically distinct in the meantime. The conducted analysis of Sebastes redfishes speciation brings into question the generality of widely accepted views on fish sympatric speciation. It also serves as an argument against the molecular clock hypothesis.

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 <i>Sebastes mentella</i> (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.

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.

Beaked redfish Sebastes mentella of the Irminger Sea – current view on the stock structure, its status and management measures

The paper aims at giving a brief review of the population structure, abundance and biomass dynamics of beaked redfish of the Irminger Sea obtained during the trawl acoustic surveys and analytical assessment. The adequacy of the current fisheries management measures for redfish in NEAFC is assessed. It was shown, that recent findings of the foreign genetic research apparently contradict to the relevant population structure for beaked redfish of the Irminger Sea applied in ICES, which specifies four stocks of the species. The ICES’ position of the depressed shallow pelagic and deep pelagic redfish stocks lacks substantial evidence from the results of the surveys in 2018–2021 and analytical assessment carried out by the Russian experts for the single redfish stock. The results allow assessing the current state of the stock as ‘good’. Thus, ICES/NEAFC recommendations that there shall be no directed fisheries neither for the shallow pelagic redfish stock nor the deep pelagic redfish stock in the Irminger Sea and adjacent waters until 2024 are insufficiently substantiated and need to be revised.

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.

Age-dependent patterns of spatial autocorrelation in fish populations.

The degree of spatial autocorrelation in population fluctuations increases with dispersal and geographical covariation in the environment, and decreases with strength of density dependence. Because the effects of these processes can vary throughout an individual's lifespan, we studied how spatial autocorrelation in abundance changed with age in three marine fish species in the Barents Sea. We found large interspecific differences in age-dependent patterns of spatial autocorrelation in density. Spatial autocorrelation increased with age in cod, the reverse trend was found in beaked redfish, while it remained constant among age classes in haddock. We also accounted for the average effect of local cohort dynamics, i.e. the expected local density of an age class given last year's local density of the cohort, with the goal of disentangling spatial autocorrelation patterns acting on an age class from those formed during younger age classes and being carried over. We found that the spatial autocorrelation pattern of older age classes became increasingly determined by the distribution of the cohort during the previous year. Lastly, we found high degrees of autocorrelation over long distances for the three species, suggesting the presence of far-reaching autocorrelating processes on these populations. We discuss how differences in the species' life history strategies could cause the observed differences in age-specific variation in spatial autocorrelation. As spatial autocorrelation can differ among age classes, our study indicates that fluctuations in age structure can influence the spatio-temporal variation in abundance of marine fish populations.

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.

Ecological and Population Features of Beaked Redfish Sebastes mentella (Sebastidae) in the Northwest Atlantic Based on the Analysis of Its Parasite Fauna

The results of studying the composition and features of the ecology, zoogeography, and formation of the parasite fauna of beaked redfish Sebastes mentella in the waters of four areas of the bathyal Northwest Atlantic zone and the Labrador Sea pelagic zone are given. A high level of similarity is revealed between the composition of the parasite fauna of this host from areas of the Hamilton Bank and northern and southern slopes of the Grand Bank. The composition and features of the age-related dynamics of the formation diversity of the parasite fauna show a significant isolation of the grouping of beaked redfish on the Flemish Cap Bank from its aggregations in other areas of the Canadian coast and the Labrador Sea pelagic zone. These factors, in combination with the presented ecological and population characteristics, indicate the population status of the grouping of beaked redfish on the Flemish Cap Bank.

Parasites and Maturation Rate as Indicators of Population Structure in the Beaked Redfish Sebastes mentella (Sebastidae)

The direction of phylogenesis of beaked redfish Sebastes mentella is considered based on a comparative analysis of the parasite fauna and maturation rate of individuals in the pelagic and near-bottom groups in the North Atlantic and the Norwegian-Barents sea populations. The individuals of the beaked redfish inhabiting the pelagic and bathyal zones of the Norwegian Sea’s northern part are characterized by a significantly higher similarity of the parasite fauna and lesser differences in the length and maturation age than that living in the pelagic and bathyal zones of the North Atlantic seas. This may indicate that the pelagic group of beaked redfish in the Norwegian Sea is at an earlier stage of formation than the pelagic group in the Irminger and Labrador seas, and the Norwegian-Barents sea population is phylogenetically younger than the North Atlantic one. The occurrence of mass migration of beaked redfish individuals from the pelagic zone of the Irminger Sea to the Norwegian Sea indicates a probable source of origin of its Norwegian-Barents sea population.

Growth Properties in Redfishes of the Genus Sebastes on the Flemish Cap Bank

This article analyzes the dynamics of the linear growth rate for three redfish species of the genus Sebastes on the Flemish Cap bank: beaked redfish S. mentella, golden redfish S. marinus, and Acadian redfish S. fasciatus. Sexual differences in the linear growth rate are revealed for each of the three redfish species. The actual estimates of the average length by age are approximated by the Bertalanffy linear growth curve. Integrated size–age keys for 1989–2016 are calculated, and the features and differences of changes in the average length of individuals by age are shown. It is concluded that it is necessary to take into account the linear growth features of each redfish species during the recalculation of the total catch by size groups into the total catch by age.

Perfluoroalkyl substances (PFAS) in beaked redfish (Sebastes mentella) and cod (Gadus morhua) from arctic fishing grounds of Svalbard

ABSTRACTThe present study gives an overview about the concentration of PFAS in liver, fillet and belly flap of beaked redfish (Sebastes mentella) and cod (Gadus morhua) caught in pristine arctic fishing grounds of Svalbard. Out of 17 analysed substances, only six perfluoroalkyl acids (PFAAs) could be detected in the fish. The most frequently quantified substances were PFOS and perfluoroundecanoic acid (PFUnA) in liver (100%) and fillet (at least 40% and 70%, respectively) of beaked redfish and cod, and in belly flap of beaked redfish (100%). Compared to cod, beaked redfish showed significant higher PFAA concentrations with highest levels in liver. Multiple comparisons of group differences for PFAA concentrations among fish species and matrices were independent of the evaluation method, but not for the PFAA-pattern analysis. The risk assessment of PFOS indicated that beaked redfish and cod caught in the Barents Sea can be a relevant exposure source for consumers.

Mesopelagic Sound Scattering Layers of the High Arctic: Seasonal Variations in Biomass, Species Assemblage, and Trophic Relationships

Mesopelagic sound scattering layers (SSL) are ubiquitous in all oceans. Pelagic organisms within the SSL play important roles as prey for higher trophic levels and in climate regulation through the biological carbon pump. Yet, the biomass and species composition of SSL in the Arctic Ocean remain poorly documented, particularly in winter. A multifrequency echosounder detected a SSL north of Svalbard, from 79.8°N to 81.4°N, in January 2016, August 2016, and January 2017. Midwater trawl sampling confirmed that the SSL comprised zooplankton and pelagic fish of boreal and Arctic origins. Juvenile beaked redfish dominated the fish assemblage in January and Arctic cod in August. The macrozooplankton community mainly comprised the medusa Cyanea capillata, the amphipod Themisto libellula, and the euphausiids Meganyctiphanes norvegica in August and Thysanoessa inermis in January. The SSL was located in the Atlantic Water mass, between 200-700 m in August and between 50-500 m in January. In January, the SSL was shallower and weaker above the deeper basin, where less Atlantic Water penetrated. The energy content available in the form of lipids within the SSL was significantly higher in summer than winter. The biomass within the SSL was >12-fold higher in summer, and the diversity of fish was slightly higher than in winter (12 vs. 9 species). We suggest that these differences are mainly related to life history and ontogenetic changes resulting in a descent towards the seafloor, outside the mesopelagic layer, in winter. In addition, some fish species of boreal origin, such as the spotted barracudina, did not seem to survive the polar night when advected from the Atlantic into the Arctic. Others, mainly juvenile beaked redfish, were abundant in both summer and winter, implying that the species can survive the polar night and possibly extend its range into the high Arctic. Fatty-acid trophic markers revealed that Arctic cod mainly fed on calanoid copepods while juvenile beaked redfish targeted krill (Thysanoessa spp.). The relatively high biomass of Arctic cod in August and of redfish in January thus suggests a shift within the SSL, from a Calanus-based food web in summer to a krill-based food web during winter.

Studies on the influence of sampling on the levels of dioxins and PCB in fish

Beaked redfish (Sebastes mentella) and Greenland halibut (Reinhardtius hippoglossoides) were collected in waters around Svalbard (Barents Sea) to study the influence of different muscle separation/filleting techniques at small and medium fishes on the dioxin/PCB content. Sampling of both species included preparation techniques such as fillets with or without belly flaps, commercially trimmed fillets and cutting into anterior and posterior cutlets. In case of Greenland halibut also the whole edible muscle part and middle cutlets were studied. All samples analysed were far below the maximum level of 6.5 pg/g wet weight (ww) WHO-PCDD/F-PCB-TEQ and 75 ng/g ww ndl-PCB. Trimmed fillets of beaked redfish had the lowest fat content and the lowest level of dioxins and PCB (1.70%, WHO-PCDD/F-PCB-TEQ = 0.320 pg/g ww). The respective posterior cutlets showed the highest fat content and highest levels of dioxins and PCB (2.66%, WHO-PCDD/F-PCB-TEQ = 0.729 pg/g ww). Levels of dioxins and PCB in Greenland halibut samples were generally higher and ranged between WHO-PCDD/F-PCB-TEQ = 0.784 pg/g ww (fillets without bells flaps, fat content = 8.83%) and WHO-PCDD/F-PCB-TEQ = 2.022 pg/g ww (edible part whole muscle, fat content = 8.62%). The results show a considerable influence of the different sampling methods on the dioxin and PCB levels of the species analysed.

Variability of fat, water and protein content in the flesh of beaked redfish (Sebastes mentella) and Greenland halibut (Reinhardtius hippoglossoides) from artic fishing grounds

Beaked redfish (Sebastes mentella) and Greenland halibut (Reinhardtius hippoglossoides) were collected from fishing grounds of the Barents Sea to study the composition and lipid distribution of the muscle tissue. The belly flaps of beaked redfish showed higher lipid contents (mean 4.6%) compared to anterior dorsal muscle. The protein content was relatively constant in all parts (18–19%). The variation in the muscle lipid composition among individual redfish was greater than the variation among different anatomical locations of the fillets. No significant differences were found in the composition of Greenland halibut muscle parts. The protein content was generally low and ranged between 12.2–13.9%. The lipid content varied considerably between approximately 6 and 17%, displaying large variations of the lipid contents between different Greenland halibut individuals from one catch. The variability of lipid content should be considered in the risk assessment and management of lipophilic contaminants in fish fillets. A correlation between water and lipid content was found for both species (r = −0.8750, beaked redfish; r = −0.8732, Greenland halibut).

Эколого-популяционные особенности окуня-клювача Sebastes mentella (Scorpaenidae) Норвежского моря на основе анализа его паразитофауны

Эколого-популяционные особенности окуня-клювача Sebastes mentella (Scorpaenidae) Норвежского моря на основе анализа его паразитофауны

Long-term stability of Sphyrion lumpi abundance in beaked redfish Sebastes mentella of the Irminger Sea and its use as biological marker.

The main commercial fish species in the Irminger Sea, the beaked redfish Sebastes mentella, is commonly infected with the copepod Sphyrion lumpi. This ectoparasite is often used as a biological marker for stock discrimination to evaluate the still-debated metapopulation structure of beaked redfish. Nevertheless, it is still not understood whether parasite abundances and communities vary over longer time periods. In the present study, we investigated the abundance of S. lumpi in S. mentella of the pelagic zone of the Irminger Sea and adjacent waters. Our analyses revealed that live S. lumpi abundance remained constant during summer over a sampling period from 2001 to 2015, which confirms its validity as a biomarker. As S. mentella forms dense aggregations during mating, our results suggest that host densities are, regardless of a fishery-induced decrease in host biomass, large enough to facilitate the direct transmission of S. lumpi. After correcting for covariate effects, two stock units could be differentiated, which supports a continuation of the current fishery management strategy.

Features of the reproductive cycle in females of the beaked redfish Sebastes mentella (Sebastidae)

The reproductive status of some categories of females of the beaked redfish Sebastes mentella has been determined as a result of the histological analysis. The histological characteristic of gonads of large nonreproductive females of redfish is presented for the first time. Gonads of mature females that skip spawning are studied. The cytomorphological characteristic of ovaries after larvae extrusion is specified. A broadened maturity scale for gonads of females of S. mentella supplemented with stages that characterize fish that skip spawning and large nonreproductive females is proposed.