Incidental catch of large marine vertebrates in gillnet fisheries in Newfoundland and Labrador

Benjamins, Steven (2006) Incidental catch of large marine vertebrates in gillnet fisheries in Newfoundland and Labrador. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Small cetaceans, such as harbour porpoises, often become entangled in gillnets, and this anthropogenic mortality is a conservation concern. For years, harbour porpoises have been captured regularly in fisheries in waters of Newfoundland and Labrador (Canada), but defendable estimates have been lacking. Incidental catch of small cetaceans in nearshore and offshore gillnet fisheries in Newfoundland and Labrador waters was studied for the years 2001, 2002 and 2003, using datasets from Fisheries and Oceans Canada, reports from fishers, and Fishery Observer records. Fisheries studied included those targeting Atlantic cod, lumpfish, Atlantic herring, monkfish, white hake, Greenland halibut, redfish and winter flounder. -- A methodology was developed to estimate incidental catch, based on datasets currently available within the Department of Fisheries and Oceans. Confidence intervals were generated using resampling statistics, allowing an assessment of uncertainty surrounding these estimates. Despite reductions in fishing effort since 1992, an estimated average of 1,516 harbour porpoises were captured in various Newfoundland and Labrador gillnet fisheries annually between 2001 and 2003. Most captures occurred in nearshore fisheries for Atlantic cod and lumpfish. Several dolphin species were also captured in smaller numbers, mostly in the offshore monkfish fishery. The impact of this mortality on the population of harbour porpoise and other small cetaceans cannot be assessed until population estimates become available. -- Using the same methodology, incidental catch assessments were compiled for numerous species of pinnipeds, seabirds, sharks and bony fish that had been reported as incidental catch. For most species, insufficient information exists to assess the impact of this mortality. However, catch rates of harbour seals, murres. shearwaters, various shark species and sturgeons appear to warrant concern. -- In conclusion, Newfoundland and Labrador gillnet fisheries annually remove considerable numbers of non-target large marine vertebrates from the local marine ecosystem. The nearshore fisheries for Atlantic cod and lumpfish, and the offshore fishery for monkfish, appear to capture the greatest diversity of species, including small cetaceans, various seals, murres, shearwaters, schooling sharks and sturgeons. Various potential measures to mitigate this incidental catch in Newfoundland and Labrador are discussed. A framework for assessing the impacts of fisheries on marine environments is described.

Item Type: Thesis (Doctoral (PhD))
URI: http://research.library.mun.ca/id/eprint/10156
Item ID: 10156
Additional Information: Includes bibliographical references.
Department(s): Science, Faculty of > Cognitive and Behavioural Ecology
Date: 2006
Date Type: Submission
Geographic Location: Newfoundland and Labrador
Library of Congress Subject Heading: Bycatches (Fisheries)--Environmental aspects--Newfoundland and Labrador; Cetacea populations--Newfoundland and Labrador.

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