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- About Bycatch
Researchers at the New England Aquarium (NEAq) work with
the Consortium to assess the survivability of bycatch animals.
It is extremely stressful for a marine creature to be caught,
hauled onto a boat, sorted and then released back into the
ocean. Yet, despite a vulnerability to rapid overexploitation, only in recent years has greater research attention been devoted to the physical and physiological implications of the fishing capture/handing process, factors influencing delayed mortality when discarded as bycatch. Such research can aid fishery management and conservation initiatives by determining population status and species resiliency, and informing best practices to attenuate the most detrimental aspects of capture associated with a given gear type and species.
Western North Atlantic Skate
The New England Aquarium is working in conjunction with the University of New England to assess how select North Atlantic skate species respond to and survive accidental capture in the trawl and gillnet fisheries. A cooperative effort with commercial fishermen, this ongoing study seeks to establish a comparative estimate of immediate and delayed post-capture/handling mortality in four skate species that will aid in the development of more precise bycatch mortality rates for management purposes. While most of this work has occurred in the field, other aspects of fishing capture are being simulated in the lab for a more controlled set of study conditions. Of the species assessed, two (the smooth skate, Malacoraja senta, and the thorny skate, Amblyraja radiate) have been designated by NOAA as species of concern, and received international conservation attention.
The spiny dogfish, Squalus acanthias, is commonly captured unintentionally as bycatch in both recreational and commercial fisheries in the western North Atlantic. Because of the high number of dogfish caught and released as bycatch after capture, the estimated rates of post-release mortality are important for creating accurate dogfish population models.
A study was conducted to assess the physiological status and post-release survival in spiny dogfish after otter trawl capture and handling. Researcher collaborated with commercial fishing vessels to ensure authentic fishing practices were followed. The results of this study suggest that post-release survival of spiny dogfish in trawls is high, despite significant physiological disruptions evident at the time of capture. This infers that dogfish can recover from the considerable physiological stress caused by trawl capture, although physical trauma can prove lethal, especially in a trawl that lands a very high catch biomass.
Researchers have worked in collaboration with scientists at the University of New England, Massachusetts Division of Marine Fisheries, UMass Amherst, the Cape Eleuthera Institute, and several other institutions to assess the physiological status of several coastal sharks caught as bycatch by longline fisheries and catch-and-release angling. These studies have helped establish an initial blueprint for which wide disparity by species in the ability to cope with and survive these types of fishing capture.
Elasmobranchs are not the only group of fishes that have received attention in this area from the NEAq research operations. Past studies worked with New England commercial longline fishermen to determine the impact of bottom longline capture on undersized Atlantic cod and their subsequent chance of survival post-release. Cod captured by these means are either removed by hand or mechanically. Removal of the hook by hand leaves a small hole in the fishes' jaw, while mechanical removal often results in either one or both jaws breaking. It was discovered that subsequent to capture by longline, which in itself elicits a far more pronounced physiological disturbance than hook-and-line capture, gently hand-removed cod were twice and likely to survive 72 hours than mechanically unhooked fish. NEAq researchers worked with participating fishermen to develop a less damaging hook removal method to improve the survival of sub-legal sized bycatch.