Bycatches of the greenland shark Somniosus microcephalus (Squaliformes, Chondrichthyes) in the barents sea and the adjacent waters under bottom trawling data

Rusyaev, S. M.; Орлов, А. М.

doi:10.1134/s0032945213010128

Cited by 13 publications

(4 citation statements)

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“…Rusyaev and Orlov (2013) reported 23 sharks B200 cm TL (30.7 % of total) with 13 individuals \150 cm TL. Most of these sharks were caught in the southeastern Barents Sea within the same latitudinal range as the juveniles caught in Scott Inlet/Sam Ford Trough and observed as bycatch in the gillnet fishery (Rusyaev and Orlov 2013;Fig. 1).…”

Section: Discussionmentioning

confidence: 97%

Juvenile Greenland sharks Somniosus microcephalus (Bloch & Schneider, 1801) in the Canadian Arctic

et al. 2014

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Life-stage-based management of marine fishes requires information on juvenile habitat preferences to ensure sustainable population demographics. This is especially important in the Arctic region given very little is known about the life histories of many native species, yet exploitation by developing commercial and artisanal fisheries is increasing as the ice extent decreases. Through scientific surveys and bycatch data from gillnet fisheries, we document captures of rarely reported juvenile Greenland sharks (Somniosus microcephalus; B200 cm total length [TL]) during the ice-free period in the Canadian Arctic. A total of 22 juvenile animals (42 % of total catch; n = 54), including the smallest reliably measured individual of 117 cm TL, were caught on scientific longlines and bottom trawls in Scott Inlet and Sam Ford Trough over three consecutive years. Molecular genetic nuclear markers confirmed species identity for 44 of these sharks sampled; however, two sharks including a juvenile of 150 cm TL were identified as carrying a Pacific sleeper shark (Somniosus pacificus) mitochondrial cytochrome b (cyt b) haplotype. This represents the first record of a Pacific sleeper shark genetic signature in Greenland sharks in Eastern Arctic waters. Juvenile sharks caught as bycatch in gillnet fisheries were only observed offshore in Baffin Bay surrounding a fishery closure area, while larger subadult and mature Greenland sharks ([200 cm TL) were caught in all fishing locations, including areas where juveniles were observed. The repeatable occurrence of juvenile Greenland sharks in a fjord and their presence at two offshore sites indicates that these smaller animals either reside in nurseries or have defined home ranges in both coastal and offshore regions or undertake large-scale inshoreoffshore movements.

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Section: Discussionmentioning

confidence: 97%

Juvenile Greenland sharks Somniosus microcephalus (Bloch & Schneider, 1801) in the Canadian Arctic

et al. 2014

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“…showed a distribution for this dataset in stations less than 90m depth, as our eDNA revealed. Available data on the diversity of elasmobranch species in the Bay of Biscay is limited, as most of these species are discarded from commercial fisheries and landing data is incomplete (ICES, 2017; Rodríguez-Cabello, Pérez, & Sánchez, 2013; Rusyaev & Orlov, 2013). Hence, in agreement to previous studies, our data supports eDNA as a potential mechanism for detecting and studying the distribution of elusive and deep-water species, which normally go undetected in fish trawl surveys, e.g., elasmobranchs, (Thomsen et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

Marine water environmental DNA metabarcoding provides a comprehensive fish diversity assessment and reveals spatial patterns in a large oceanic area

Fraija-Fernández

Bouquieaux

Rey

et al. 2019

Preprint

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“…So why and how has the ecosystem resisted the heavy exploitation of some FGs? The high fishing effort during the period 1965-1990 in the cod fishery in the BS have likely also increased fishing mortality of other fish FGs which were caught as bycatch (Denisenko, 2001;Rusyaev and Orlov, 2013). In the BS, there may have been few species that could take over for cod as major piscivore during the period of intense exploitation, and candidates, such as Greenland halibut, redfish and harp seals had been extensively targeted and reduced by harvesting prior and during the cold period.…”

Section: Effects Of Harvestingmentioning

confidence: 99%

Overexploitation, Recovery, and Warming of the Barents Sea Ecosystem During 1950–2013

et al. 2021

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The Barents Sea (BS) is a high-latitude shelf ecosystem with important fisheries, high and historically variable harvesting pressure, and ongoing high variability in climatic conditions. To quantify carbon flow pathways and assess if changes in harvesting intensity and climate variability have affected the BS ecosystem, we modeled the ecosystem for the period 1950–2013 using a highly trophically resolved mass-balanced food web model (Ecopath with Ecosim). Ecosim models were fitted to time series of biomasses and catches, and were forced by environmental variables and fisheries mortality. The effects on ecosystem dynamics by the drivers fishing mortality, primary production proxies related to open-water area and capelin-larvae mortality proxy, were evaluated. During the period 1970–1990, the ecosystem was in a phase of overexploitation with low top-predators’ biomasses and some trophic cascade effects and increases in prey stocks. Despite heavy exploitation of some groups, the basic ecosystem structure seems to have been preserved. After 1990, when the harvesting pressure was relaxed, most exploited boreal groups recovered with increased biomass, well-captured by the fitted Ecosim model. These biomass increases were likely driven by an increase in primary production resulting from warming and a decrease in ice-coverage. During the warm period that started about 1995, some unexploited Arctic groups decreased whereas krill and jellyfish groups increased. Only the latter trend was successfully predicted by the Ecosim model. The krill flow pathway was identified as especially important as it supplied both medium and high trophic level compartments, and this pathway became even more important after ca. 2000. The modeling results revealed complex interplay between fishery and variability of lower trophic level groups that differs between the boreal and arctic functional groups and has importance for ecosystem management.

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Bycatches of the greenland shark Somniosus microcephalus (Squaliformes, Chondrichthyes) in the barents sea and the adjacent waters under bottom trawling data

Cited by 13 publications

References 2 publications

Juvenile Greenland sharks Somniosus microcephalus (Bloch & Schneider, 1801) in the Canadian Arctic

Juvenile Greenland sharks Somniosus microcephalus (Bloch & Schneider, 1801) in the Canadian Arctic

Marine water environmental DNA metabarcoding provides a comprehensive fish diversity assessment and reveals spatial patterns in a large oceanic area

Overexploitation, Recovery, and Warming of the Barents Sea Ecosystem During 1950–2013

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