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Bycatches of the Greenland shark Somnioss microcephalus in the bottom trawl catches by the fishery boats and the total catch of the cod Gadus morhua in the fishing areas of the Barents Sea in July-December of 1981-1990.
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The present paper report unusual and additional records of sharpnose seven-gill shark Heptranchias perlo (Bonnaterre, 1788) from the northeastern Tuni-sian waters. Four specimens were collected in the Gulf of Tunis and two specimens off Bizerte. The specimens were measured for total length and weighed. The specimens from Bizerte were described in t...
Citations
... The Greenland shark has attracted increased attention from researchers in recent years for a number of reasons. This is the most northern cold-water-tolerant species, is an apex predator in Arctic ecosystems, experiences a high impact from fishing, and has a vulnerable conservation status throughout its range (Rusyaev and Orlov 2013;Santaquiteria et al. 2017;Nielsen et al. 2016Nielsen et al. , 2020Christensen 2022;Dyldin et al. 2022;Orlov et al. 2022). Moreover, the biology of this species has not been fully elucidated (Murray et al. 2008;Santaquiteria Gil 2016;Nielsen et al. 2020;Christensen 2022), and the taxonomic status of Somniosus species has not been fully clarified (Yano et al. 2004(Yano et al. , 2007Hsu et al. 2020;Christensen 2022;Timm et al. 2022). ...
... Several authors have noted the influence of climate change on the distribution and migration of Greenland sharks (Rusyaev and Orlov 2013;Edwards et al. 2019). Until recently, this species was known in the Siberian Arctic from a single record in the Baydaratskaya Bay of the Kara Sea in 1932 (Probatov 1934), which occurred during the warming period . ...
The Greenland shark Somniosus microcephalus is the most northern and cold-water shark, longest-lived vertebrate, and species at risk. A single specimen of this species, 210 cm in length and 71 kg in weight, was captured for the second time in the Laptev Sea (Siberian Arctic, Russia). Species identification was confirmed by examination of the main morphometric characters and DNA barcoding using the COI mtDNA gene. This species is widely distributed in the North Atlantic, but records in the Arctic Ocean were limited to the Canadian and Greenland coasts, White, Barents, and Kara seas. In the Laptev Sea, the Greenland shark was previously known from a single record, which was not confirmed genetically. Recent records in the Siberian Arctic are likely associated with the eastward extension of warmer waters of the North Atlantic current to this area due to recent climate change and warming in the region.
... 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. ...
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.
... This shark inhabits the continental and island shelves and the upper part of the continental slope. In the Arctic, it is known from Canadian (Resolute Bay to Baffin Bay) and Russian waters (White, Kara and Laptev seas) (Rusyaev and Orlov, 2013;Mecklenburg et al., 2018;Borodavkina et al., 2019). ...
... The optimal temperatures are probably from 2 C to 10 C (Chernova et al., 2015). Most specimens in the Barents Sea caught by bottom trawls were recorded in the range of 3-7 C (Rusyaev and Orlov, 2013). Usually, this species prefers waters with oceanic salinity but may rarely occur in waters with lower salinity, for example, in bays of the White Sea (Zhilinsky, 1915). ...
... Bycatch in the trawl fishery includes sharks ranging in size from 1.0 m to 3.5 m. The average size of sharks from trawl catches in the Russian waters of the Barents Sea is 2.2 m (Rusyaev and Orlov, 2013). ...
The endangered species, Greenland shark Somniosus microcephalus is the northernmost and most cold-water shark that is widely distributed in the north Atlantic and Arctic. It inhabits depths from the surface to almost 3000 m. It can attain a length of over 7 m, weigh up to 1.5 t and live several hundred years. As with many shark species, the Greenland shark demonstrates slow growth, long lifespan, late maturity, and small litter size that makes this species vulnerable to fisheries. There is a decline in abundance of Greenland shark since the early 1600s with the steepest decreasing since the early 1800s through the 1940s that is associated with target fishery in the past. During recent years, the major threat for this species relates to large-scale bottom trawl and longline fisheries where bycatch of this species occurs. The main conservation measures for this species should include prohibition of directed fishing and minimization of the incidental catch and mortality.
... Assuming the two parts are independent, parameters for each can be estimated separately. We argue that the independence assumption is appropriate in this scenario because factors that affect incidence of bycatch (e.g., wide distribution and long distance migration; Campana et al. 2015;Nielsen et al. 2014) and weight (e.g., variability in size and density; MacNeil et al. 2012;Rusyaev and Orlov 2013) can be very different. If this is not the case, the correlated two parts can be modelled jointly (Cantoni et al. 2017). ...
Excess bycatch of marine species during commercial fishing trips is a challenging problem in fishery management worldwide. The aims of this paper are twofold: to introduce methods and provide a practical guide for spatio-temporal modelling of bycatch data, as well as to apply these methods and present a thorough examination of Greenland shark bycatch weight in a Canadian Arctic fishery. We introduce the spatially explicit two-part model and offer a step by step guide for applying the model to any form of bycatch data, from data cleaning, exploratory data analysis, variable and model selection, model checking, to results interpretation. We address various problems encountered in decision making and suggest that researchers proceed cautiously and always keep in mind the aims of the analysis when fitting a spatio-temporal model. Results identified spatio-temporal hotspots and indicated month and gear type were key drivers of high bycatch. The importance of onboard observers in providing robust bycatch data was also evident. These findings will help to inform conservation strategies and management decisions, such as limiting access to spatial hotspots, seasonal closures and gear restrictions.
... 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 are limited, as most of these species are discarded from commercial fisheries and landing data are incomplete(ICES, 2017;Rodríguez-Cabello, Pérez, & Sánchez, 2013;Rusyaev & Orlov, 2013). Hence, in agreement to ...
Current methods for monitoring marine fish (including bony fishes and elasmobranchs) diversity mostly rely on trawling surveys, which are invasive, costly, and time‐consuming. Moreover, these methods are selective, targeting a subset of species at the time, and can be inaccessible to certain areas. Here, we used environmental DNA (eDNA), the DNA present in the water column as part of shed cells, tissues, or mucus, to provide comprehensive information about fish diversity in a large marine area. Further, eDNA results were compared to the fish diversity obtained in pelagic trawls. A total of 44 5 L‐water samples were collected onboard a wide‐scale oceanographic survey covering about 120,000 square kilometers in Northeast Atlantic Ocean. A short region of the 12S rRNA gene was amplified and sequenced through metabarcoding generating almost 3.5 million quality‐filtered reads. Trawl and eDNA samples resulted in the same most abundant species (European anchovy, European pilchard, Atlantic mackerel, and blue whiting), but eDNA metabarcoding resulted in more detected bony fish and elasmobranch species (116) than trawling (16). Although an overall correlation between fishes biomass and number of reads was observed, some species deviated from the common trend, which could be explained by inherent biases of each of the methods. Species distribution patterns inferred from eDNA metabarcoding data coincided with current ecological knowledge of the species, suggesting that eDNA has the potential to draw sound ecological conclusions that can contribute to fish surveillance programs. Our results support eDNA metabarcoding for broad‐scale marine fish diversity monitoring in the context of Directives such as the Common Fisheries Policy or the Marine Strategy Framework Directive.
... In the Barents Sea, in addition to invertebrates, birds, and seals, sharks consume such fish species as skates Raja sp., cod Gadus morhua, haddock Melanogrammus aeglefinus, wolffish Anarhichas sp., lumpfish Cyclopterus lumpus, and the European plaice Pleuronectes platessa (Knipovich, 1902). According to the survey data of PINRO, this species can constitute up to 50% of the shark diet in the areas of the Atlantic cod schooling (Rusyaev and Orlov, 2013). In western Greenland, in the areas inhabited by the Greenland halibut Reinhardtius hippoglossoides, it is the species that prevails in the shark diet (Yano et al., 2007). ...
... Most of the cases of shark registration occurred in August (the period of the greatest warming up of the waters in the Kara Sea) and one case was in September. This corresponds to the concepts of the temperature preferendum of the Greenland shark, which is often noted in waters with low temperatures exceeding zero Celsius (0-3°С) (Rusyaev and Orlov, 2013;Campana et al., 2013). ...
... cies. However, this is not the case: in the Arctic regions (the Barents Sea, Greenland), the Greenland shark was also observed at a negative temperature of -1.0°С (Rusyaev and Orlov, 2013) and -1. 8°С (MacNeil et al., 2012). ...
Visual observation data of the Greenland shark Somniosus microcephalus in August–September 2017 in the Kara Sea specifying the species range in this Arctic region are presented. Six cases of species registration in the surface waters were recorded. The factors limiting the distribution of sharks on the Arctic shelf are discussed.
... Greenland sharks have also been reported from offshore Newfoundland and Gulf of St Lawrence in southern Canada and from Gulf of Maine and Cape Cod in northeastern USA , Templeman 1963Campana et al. 2015a). Greenland sharks are also distributed throughout Iceland shelf waters and further across the northern North Atlantic throughout the Barents Sea including Svalbard coastal and offshore waters , Rusyaev & Orlov 2013. The northernmost report of a Greenland shark is from 82 o N . ...
... Arctic (Davis et al. 2013, Rusyaev & Orlov 2013, DFO 2016, and exposure to heavy fishing pressure in the 46 past , many aspects of the basic biology of the Greenland shark remain poorly 47 elucidated. This includes, in particular, the breeding part of the population (i.e. the effective population) of 48 which knowledge on size and distribution is extremely limited, as well as most aspects of their reproductive 49 biology (see review on Greenland shark biology in . ...
This PhD project has aimed at investigating longevity of the Greenland shark. The largest
Greenland sharks measure at least 550 cm, and ever since Poul Marinus Hansen in 1963
presented that a recaptured medium-sized Greenland shark had grown 8 cm in 16 year, longevity of the species has been subject for speculation. Conventional age determination techniques for teleost or elasmobranchs are not applicable on the Greenland shark and its longevity has thus remained a mystery for decades.
Inspired by alternative age estimation techniques applied on other sharks and whales, I have used bomb radiocarbon dating and a Bayesian calibration model to estimate longevity of the Greenland shark. The analyzed tissue stems from the eye lens nucleus – unique material which presumably reflects age 0 of the shark, as it has not undergone metabolic changes during the animal’s life. By studying 28 Greenland shark females between 81 cm and 502 cm, I estimate the oldest shark to be between 272 years and 512 years. With an estimated lifespan of at least 272 years, the Greenland shark is the longest living vertebrate animal in the world.
In order to produce these age estimates, it has been necessary to study the carbon source of the eye lens nucleus in more detail. The center of the nucleus consists of proteins and the analyzed tissue stems from the diet of the shark’s mother. From feeding ecology and satellite tracking, I have therefore investigated adult females. Sharks of this life stage mainly occupied continental shelf waters in southern Greenland at depths between 200 and 550 m and fed primarily on cod, redfish and seals. From previous investigations of predatory sharks and whales in the north Atlantic, bomb radiocarbon has been widely applied, and I argue that a similar calibration approach is valid to use on the Greenland shark.
The main aim of this thesis is to clarify the biological assumptions behind the radiocarbon dating leading to the age estimates of the Greenland shark. These age estimates rest on classical biological feeding ecology studies, chemical isotope analysis and advanced mathematical modelling. This interdisciplinary approach has been crucial for the success of the project. The thesis also illustrates how a novel cross-combination of techniques can be applied on other marine species difficult to age determine, and how the Greenland shark is unique to the arctic ecosystem. Many aspects of the basic biology of the Greenland shark remain mysterious.
... 5). This species reaches the northern Svalbard (81°18′ N) along the continental slope (Rusyaev and Orlov, 2013). It was recorded in deep inlets of the Murmansk coast: in Tyuva guba and Teriberka at depths of 310 and 169 m, respectively (Knipowitsch, 1902), and in Motovsky and Kola Bays at the depth of 260-280 and 311 m, respectively (Breitfuss 1903(Breitfuss , 1906. ...
... (our data), 1.01°C (Thielemann, 1922), 1.8-4.4°C (Knipow itsch, 1902;Breitfuss, 1912), and from -1 to 3°C with 1902, 1904Breitfuss, 1903Breitfuss, , 1906Breitfuss, , 1908Breitfuss, , 1912Breitfuss, , 1915Probatov, 1934;Andriashev, 1954 preference for positive temperatures (Rusyaev and Orlov, 2013). Similar temperatures have been reported for the Greenland population of this species, namely the range of 0-6°C with an average value of 2.7°C (Campana et al., 2013). ...
... An analogous pattern is observed in the European north. This shark in the Barents Sea is observed at a depth from 50 m (Thielemann, 1922) to 600 m (Rusyaev and Orlov, 2013), with most of the cases within the depth range of 150-450 m. The indi vidual of the Laptev Sea was caught closer to the upper limit of the habitat (240 m). ...
The first record of the Greenland shark Somniosus microcephalus (Somniosidae) at the northern boundary of the Laptev Sea (78°04.3 N, 133°24.4 E) is described; this site is 1500 km eastward of any earlier records for this species in the Barents Sea and adjacent regions of the Kara Sea. A young male with an total length of 260 cm was caught in September 2014 by a bottom trawl at a depth of 240 m. Maps of the capture sites for S. microcephalus individuals in the Barents Sea and adjacent waterbody are presented. It is assumed that this shark came to the continental slope of the Arctic Ocean with a relatively warm flow of Atlantic origin, running along the northern Arctic shelf edge.
... Nielsen et al. (2014) reported the capture of only four sharks B200 cm around Greenland from scientific surveys and commercial fisheries catches since 1998, with these all occurring in a relatively defined region on the west coast (Fig. 1). 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. ...
... 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). ...
Life-stage-based management of marine fishes requires information on juvenile habitat preferences to ensure sustainable population demographics. This is espe-cially 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 fisher-ies is increasing as the ice extent decreases. Through scien-tific 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 con-secutive 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) mito-chondrial 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 occur-rence of juvenile Greenland sharks in a fjord and their pre-sence 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 inshore– offshore movements.
... Currently, the targeted AOAS fishes count 59 species (~ 9%) in 14 families (~ 13%) (Appendix 6.2). They all belong to the bony fishes, although cartilaginous fishes, e.g. the sleeper sharks Somniosus spp., constitute a significant but largely unreported bycatch (Rusyaev & Orlov 2013). There are huge regional differences in the AOAS. ...
