Multidisciplinary perspectives on Atlantic halibut spawning behavior and vulnerability in the Gulf of St. Lawrence

Marshall, Rachel C. (2020) Multidisciplinary perspectives on Atlantic halibut spawning behavior and vulnerability in the Gulf of St. Lawrence. Masters thesis, Memorial University of Newfoundland.

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Abstract

Marine species’ distribution and reproduction is valuable information for fisheries management and conservation. In this thesis, spawning of Atlantic halibut, a commercially important flatfish showing increasing abundance in the Gulf of St. Lawrence, is characterized using pop-up satellite archival tags, and potential ocean industry impacts to the halibut population are identified with fish harvesters’ knowledge. Halibut displayed extreme rises off the seafloor, interpreted as spawning behavior, from January to late April. The date of the first spawning rise was negatively correlated with December to mid-January water temperatures. The number of female spawning rises, assumed to represent egg batches, was independent of fish length. Halibut harvesters presented with findings of halibut spawning and migration identified industries that could impact the halibut population, at the forefront being a developing redfish trawl fishery. Harvesters participating in semi-structured interviews expressed concern that halibut bycatch in a redfish fishery would reduce the current halibut abundance, which they attributed to the reduction of Gulf trawling and halibut bycatch since the 1990s. The integration of electronic tagging and fish harvesters’ knowledge highlights these halibut population vulnerabilities for ocean managers to incorporate into future spatial planning and management of the Gulf of St. Lawrence.

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