Non-parametric analysis of the spatio-temporal variability in the fatty-acid profiles among Greenland sharks

Shifting prey distributions due to global warming are expected to generate dramatic ecosystem-wide changes in trophic structure within Arctic marine ecosystems. Yet a relatively poor understanding of contemporary Arctic food webs makes it difficult to predict the consequences of such changes for Arctic predators. Doing so requires quantitative approaches that can track contemporary changes in predator diets through time, using accurate, well-defined methods. Here we use fatty acids (FA) to quantify differences in consumer diet using permutational multivariate analysis of variance tests that characterize spatial and temporal changes in consumer FA signatures. Specifically we explore differences in Greenland shark (Somniosus microcephalus) FA to differentiate their potential trophic role between Svalbard, Norway and Cumberland Sound, Canada. Greenland shark FA signatures revealed significant inter-annual differences, probably driven by varying seal and Greenland halibut responses to environmental conditions such as the NAO, bottom temperature, and annual sea-ice extent. Uncommon FA were also found to play an important role in driving spatial and temporal differences in Greenland shark FA profiles. Our statistical approach should facilitate quantification of changing consumer diets across a range of marine ecosystems.

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Greenland shark (Somniosus microcephalus) feeding behavior on static fishing gear, effect of SMART (Selective Magnetic and Repellent-Treated) hook deterrent technology, and factors influencing entanglement in bottom longlines

PeerJ ◽

10.7717/peerj.4751 ◽

2018 ◽

Vol 6 ◽

pp. e4751 ◽

Cited By ~ 3

Author(s):

Scott M. Grant ◽

Rennie Sullivan ◽

Kevin J. Hedges

Keyword(s):

Feeding Behavior ◽

Fishing Gear ◽

Magnetic Alloy ◽

Greenland Shark ◽

Greenland Halibut ◽

Winter Storms ◽

Ice Conditions ◽

In Situ Observations ◽

Somniosus Microcephalus

The Greenland Shark (Somniosus microcephalus) is the most common bycatch in the Greenland halibut (Reinhardtius hippoglossoides) bottom longline fishery in Cumberland Sound, Canada. Historically, this inshore fishery has been prosecuted through the ice during winter but winter storms and unpredictable landfast ice conditions since the mid-1990s have led to interest in developing a summer fishery during the ice-free season. However, bycatch of Greenland shark was found to increase substantially with 570 sharks captured during an experimental Greenland halibut summer fishery (i.e., mean of 6.3 sharks per 1,000 hooks set) and mortality was reported to be about 50% due in part to fishers killing sharks that were severely entangled in longline gear. This study investigated whether the SMART (Selective Magnetic and Repellent-Treated) hook technology is a practical deterrent to Greenland shark predation and subsequent bycatch on bottom longlines. Greenland shark feeding behavior, feeding kinematics, and variables affecting entanglement/disentanglement and release are also described. The SMART hook failed to deter Greenland shark predation, i.e., all sharks were captured on SMART hooks, some with more than one SMART hook in their jaw. Moreover, recently captured Greenland sharks did not exhibit a behavioral response to SMART hooks. In situ observations of Greenland shark feeding show that this species uses a powerful inertial suction mode of feeding and was able to draw bait into the mouth from a distance of 25–35 cm. This method of feeding is suggested to negate the potential deterrent effects of electropositive metal and magnetic alloy substitutions to the SMART hook technology. The number of hooks entangled by a Greenland shark and time to disentangle and live-release a shark was found to increase with body length.

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A feasibility study to determine the use of baited pots in Greenland halibut (Reinhardtius hippoglossoides) fisheries, supported by the use of underwater video observations

PeerJ ◽

10.7717/peerj.10536 ◽

2021 ◽

Vol 9 ◽

pp. e10536

Author(s):

Margaret H. Folkins ◽

Scott M. Grant ◽

Philip Walsh

Keyword(s):

Underwater Video ◽

Greenland Shark ◽

Greenland Halibut ◽

Future Studies ◽

Video Observations ◽

Greenland Halibut Reinhardtius Hippoglossoides ◽

Reinhardtius Hippoglossoides ◽

Somniosus Microcephalus ◽

Catch Rates ◽

Upper Chamber

High incidental catches of Greenland shark (Somniosus microcephalus) in Nunavut’s Greenland halibut (Reinhardtius hippoglossoides) fishery has led to studies on the feasibility of capturing Greenland halibut with baited pots. In this study, catch rates among six experimental pots are compared. In addition to this, underwater video observations of Greenland halibut interacting with two of these experimental pot types are quantified in order to help provide recommendations on future pot designs. Catch rates of Greenland halibut differed among pots with different entrance mesh types, and none of the pots produced substantial amounts of bycatch. Strings of pots were deployed within a narrow corridor between baited gillnets targeting Greenland halibut, which may have affected catch results. Video observations revealed Greenland halibut entangled by their teeth significantly more often in entrance funnels constructed with 50 mm than with 19 mm clear monofilament netting and the entrance rate was 45% higher with the 19 mm netting. Greenland halibut that successfully entered a pot repeatedly became entangled by their teeth in 58 mm netting used in the side and end panels and in a horizontal panel used to separate the pot into a lower and upper chamber. The majority (80%) of Greenland halibut were observed to approach a pot against the current. The downstream entrance was aligned with the current in 52% of the observed Greenland halibut approaches. Seventy percent of entry attempts and 67% of successful entries occurred when fish approached against the current and when the entrance was aligned with the current. These observations lead to recommendations that future studies consider developing a four entrance pot to ensure an entrance is always aligned with bottom currents. Based on these observations of entanglements, it is recommended to use 19 mm clear monofilament netting in the entrance funnel, 100 mm polyethylene netting in the exterior panels, and 19 mm polypropylene netting in the horizontal panel when targeting Greenland halibut. Three Greenland sharks were observed interacting with the pots in the video sets, but none were captured or damaged the pots during the potting experiments, providing validity to the use of pots to mitigate the capture of Greenland shark in Nunavut territorial waters.

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Greenland shark (Somniosus microcephalus) feeding behavior on static fishing gear, effect of SMART (Selective Magnetic and Repellent-Treated) hook deterrent technology, and factors influencing entanglement in bottom longlines

10.7287/peerj.preprints.26864 ◽

2018 ◽

Author(s):

Scott M Grant ◽

Rennie Sullivan ◽

Kevin J Hedges

Keyword(s):

Feeding Behavior ◽

Fishing Gear ◽

Magnetic Alloy ◽

Greenland Shark ◽

Greenland Halibut ◽

Winter Storms ◽

Ice Conditions ◽

In Situ Observations ◽

Somniosus Microcephalus

The Greenland Shark (Somniosus microcephalus) is the most common bycatch in the Greenland halibut (Reinhardtius hippoglossoides) bottom longline fishery in Cumberland Sound, Canada. Historically, this inshore fishery has been prosecuted through the ice during winter but winter storms and unpredictable landfast ice conditions since the mid-1990s have led to interest in developing a summer fishery during the ice-free season. However, bycatch of Greenland shark was found to increase substantially with 570 sharks captured during an experimental Greenland halibut summer fishery (i.e., mean of 6.3 sharks per 1,000 hooks set) and mortality was reported to be about 50% due to in part to fishers killing sharks that were severely entangled in longline gear. This study investigated whether the SMART (Selective Magnetic and Repellent-Treated) hook technology is a practical deterrent to Greenland shark predation and subsequent bycatch on bottom longlines. Greenland shark feeding behavior, feeding kinematics, and variables affecting entanglement/disentanglement and release are also described. The SMART hook failed to deter Greenland shark predation i.e., all sharks were captured on SMART hooks, some with more than one SMART hook in their jaw. Moreover, recently captured Greenland sharks did not exhibit a behavioral response to SMART hooks. In situ observations of Greenland shark feeding show that this species uses a powerful inertial suction mode of feeding and was able to draw bait into the mouth from a distance of 25-35 cm. This method of feeding is suggested to negate the potential deterrent effects of electropositive metal and magnetic alloy substitutions to the SMART hook technology. The number of hooks entangled by a Greenland shark and time to disentangle and live-release a shark was found to increase with body length.

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Applying Bayesian spatiotemporal models to fisheries bycatch in the Canadian Arctic

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2014-0159 ◽

2015 ◽

Vol 72 (2) ◽

pp. 186-197 ◽

Cited By ~ 65

Author(s):

Aurelie Cosandey-Godin ◽

Elias Teixeira Krainski ◽

Boris Worm ◽

Joanna Mills Flemming

Keyword(s):

Computational Cost ◽

Conservation Strategies ◽

Greenland Shark ◽

Greenland Halibut ◽

High Incidence ◽

Greenland Halibut Reinhardtius Hippoglossoides ◽

Fisheries Bycatch ◽

Somniosus Microcephalus ◽

Spatiotemporal Models ◽

Physical Features

Understanding and reducing the incidence of accidental bycatch, particularly for vulnerable species such as sharks, is a major challenge for contemporary fisheries management. Here we establish integrated nested Laplace approximations (INLA) and stochastic partial differential equations (SPDE) as two powerful tools for modelling patterns of bycatch through time and space. These novel, computationally fast approaches are applied to fit zero-inflated hierarchical spatiotemporal models to Greenland shark (Somniosus microcephalus) bycatch data from the Baffin Bay Greenland halibut (Reinhardtius hippoglossoides) gillnet fishery. Results indicate that Greenland shark bycatch is clustered in space and time, varies significantly from year to year, and there are both tractable factors (number of gillnet panels, total Greenland halibut catch) and physical features (bathymetry) leading to the high incidence of Greenland shark bycatch. Bycatch risk could be reduced by limiting access to spatiotemporal hotspots or by establishing a maximum number of panels per haul. Our method explicitly models the spatiotemporal correlation structure inherent in bycatch data at a very reasonable computational cost, such that the forecasting of bycatch patterns and simulating conservation strategies becomes more accessible.

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Greenland shark (Somniosus microcephalus) feeding behavior on static fishing gear, effect of SMART (Selective Magnetic and Repellent-Treated) hook deterrent technology, and factors influencing entanglement in bottom longlines

10.7287/peerj.preprints.26864v1 ◽

2018 ◽

Author(s):

Scott M Grant ◽

Rennie Sullivan ◽

Kevin J Hedges

Keyword(s):

Feeding Behavior ◽

Fishing Gear ◽

Magnetic Alloy ◽

Greenland Shark ◽

Greenland Halibut ◽

Winter Storms ◽

Ice Conditions ◽

In Situ Observations ◽

Somniosus Microcephalus

The Greenland Shark (Somniosus microcephalus) is the most common bycatch in the Greenland halibut (Reinhardtius hippoglossoides) bottom longline fishery in Cumberland Sound, Canada. Historically, this inshore fishery has been prosecuted through the ice during winter but winter storms and unpredictable landfast ice conditions since the mid-1990s have led to interest in developing a summer fishery during the ice-free season. However, bycatch of Greenland shark was found to increase substantially with 570 sharks captured during an experimental Greenland halibut summer fishery (i.e., mean of 6.3 sharks per 1,000 hooks set) and mortality was reported to be about 50% due to in part to fishers killing sharks that were severely entangled in longline gear. This study investigated whether the SMART (Selective Magnetic and Repellent-Treated) hook technology is a practical deterrent to Greenland shark predation and subsequent bycatch on bottom longlines. Greenland shark feeding behavior, feeding kinematics, and variables affecting entanglement/disentanglement and release are also described. The SMART hook failed to deter Greenland shark predation i.e., all sharks were captured on SMART hooks, some with more than one SMART hook in their jaw. Moreover, recently captured Greenland sharks did not exhibit a behavioral response to SMART hooks. In situ observations of Greenland shark feeding show that this species uses a powerful inertial suction mode of feeding and was able to draw bait into the mouth from a distance of 25-35 cm. This method of feeding is suggested to negate the potential deterrent effects of electropositive metal and magnetic alloy substitutions to the SMART hook technology. The number of hooks entangled by a Greenland shark and time to disentangle and live-release a shark was found to increase with body length.

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Influence of Environmental Variables on the Diel Movements of the Greenland Shark (Somniosus microcephalus) in the St. Lawrence Estuary

The Canadian Field-Naturalist ◽

10.22621/cfn.v130i1.1784 ◽

2016 ◽

Vol 130 (1) ◽

pp. 1 ◽

Cited By ~ 1

Author(s):

Jeffrey J. Gallant ◽

Marco A. Rodriguez ◽

Michael J.W. Stokesbury ◽

Chris Harvey-Clark

Keyword(s):

Shallow Water ◽

Environmental Variables ◽

Thermal Structure ◽

The Arctic ◽

Greenland Shark ◽

Greenland Halibut ◽

Vertical Movements ◽

Lawrence Estuary ◽

Somniosus Microcephalus ◽

St Lawrence Estuary

The geographic distribution of the Greenland Shark (Somniosus microcephalus) extends from the Arctic Ocean to the North Atlantic Ocean. However, little is known about the habitat of this species, as it is generally found at great depths or in the High Arctic. In the St. Lawrence Estuary, Greenland Sharks undertake diel vertical movements into shallow water (≤ 30 m), but the reasons for these movements are unknown. To test the hypothesis that environmental variables drive the movements of this shark in the St. Lawrence Estuary, eight Greenland Sharks were tagged with acoustic telemetry transmitters during the summer of 2005. Three environmental factors, temperature, light, and tides, were associated with their movements. Movement patterns indicate a preference for deep, cold water during daylight hours and shallow, warmer water during the night. Ascending into shallow water mostly coincided with darkness and high tide. This improved understanding of the spatio-temporal distributionof the Greenland Shark will allow for assessment of the risk to these sharks from commercial fisheries, as occurs in the Greenland Halibut (Reinhardtius hippoglossoides) longline fishery. In addition, temperature-driven behavioural patterns may change as the thermal structure of the water column shifts due to global warming.

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Effects of monofilament nylon versus braided multifilament nylon gangions on catch rates of Greenland shark (Somniosus microcephalus) in bottom set longlines

PeerJ ◽

10.7717/peerj.10407 ◽

2020 ◽

Vol 8 ◽

pp. e10407

Author(s):

Scott M. Grant ◽

Jenna G. Munden ◽

Kevin J. Hedges

Keyword(s):

Breaking Strength ◽

The Body ◽

Biological Information ◽

Fishing Gear ◽

Greenland Shark ◽

Greenland Halibut ◽

Somniosus Microcephalus ◽

Catch Rates ◽

Time Required ◽

Longline Fisheries

The Greenland shark (Somniosus microcephalus) is the main bycatch species in established and exploratory inshore longline fisheries for Greenland halibut (Reinhardtius hippoglossoides) on the east coast of Baffin Island, Canada. Bycatch and entanglement in longline gear has at times been substantial and post-release survival is questionable when Greenland sharks are released with trailing fishing gear. This study investigated the effect of the type of fishing line used in the gangion and gangion breaking strength on catch rates of Greenland shark and Greenland halibut in bottom set longlines. Circle (size 14/0, 0° offset) hooks were used throughout the study. Behavior of captured sharks, mode of capture (i.e., jaw hook and/or entanglement), level of entanglement in longline gear, time required to disentangle sharks and biological information (sex, body length and health status) were recorded. Catch rates of Greenland shark were independent of monofilament nylon gangion breaking strength and monofilament gangions captured significantly fewer Greenland sharks than the traditional braided multifilament nylon gangion. Catch rates and body size of Greenland halibut did not differ significantly between gangion treatments. Although most (84%) of the Greenland sharks were hooked by the jaw, a high percentage (76%) were entangled in the mainline. The mean length of mainline entangled around the body and/or caudal peduncle and caudal fin was 28.7 m. Greenland sharks exhibited cannibalistic behavior with 15% of captured sharks cannibalized. All remaining sharks were alive and survived the disentanglement process which can be attributed to their lethargic behavior and lack of resistance when hauled to the surface. Thus, as a conservation measure fishers should be encouraged to remove trailing fishing gear prior to release. Our results are used to demonstrate benefits to the fishing industry with regard to an overall reduction in the period of time to disentangle sharks and damage to fishing gear by switching from braided multifilament to monofilament gangions in Greenland halibut longline fisheries.

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