Understanding the co-occurrence of large whales and commercial fixed gear fisheries off the west coast of the United States


Title: Understanding the co-occurrence of large whales and commercial fixed gear fisheries off the west coast of the United States
Publication Date:
September 30, 2013
Document Number: NOAA-TM-NMFS-SWR-044
Pages: 102
Technology Type:

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Saez, L.; Lawson, D.; DeAngelis, M.; Petras, E.; Wilkin, S.; Fahy, C. (2013). Understanding the co-occurrence of large whales and commercial fixed gear fisheries off the west coast of the United States. Report by National Oceanic and Atmospheric Administration (NOAA). pp 102.

Large whale entanglement in commercial fishing gear off the U.S. west coast has been identified as an issue of concern by NOAA’s National Marine Fisheries Service (NMFS) because of the potential impacts to both large whales (individually and at a stock/population level) and the commercial fishing industry.  Large whales entangled in gear may be injured and/or impared which could affect the ability of individuals to survive and a population’s ability to recover. Blue whales (Balaenoptera musculus), fin whales (Balaenoptera physalus), gray whales (Eschrichtius robustus), humpback whales (Megaptera novaeangliae) and sperm whales (Physeter macrocephalus) were included in this study based on their distribution and density associated with habitat, as modeled through multi-year ship-based surveys or migration studies and/or historic entanglement records.  Along the U.S. west coast, an average of 10 large whales have been reported entangled between 2000 and 2012.  Little information has been confirmed from entanglement reports about the origin of the entangling fishing gear; therefore NMFS has developed analytical tools to assess the potential entanglement risk associated with various fixed gear fisheries relative to their co-occurrence with large whale species.  A primary tool includes the development of a model to represent the spatial and temporal distributions of commercial fishing effort, focusing on fixed gear fisheries with gear that has been confirmed as entangling whales through sightings and strandings of entangled animals and or has the potential for causing entanglement based on similarities in the general configuration of gear across the fisheries. Fishing effort represented in this study, both state and federally managed, was derived from landings data obtained through the Pacific Fisheries Information Network (PacFIN).  The relative density of fishing effort throughout the calendar year was overlaid with species-specific whale distribution patterns, modeled from systematically-collected marine mammal survey data, to help identify spatial and temporal overlap between whales and fisheries.  The other tool developed, a co-occurrence model, identified potential species-specific elevated risk areas where and when large whales are more likely to encounter fishing gear, which is the first step in assessment of whale entanglement risk associated with fixed-gear fisheries on the U.S. west coast. Co-occurrence “scores” were calculated based on correlated area, time, and density of overlap between fixed gear fisheries and whale distribution. Overall, the Dungeness crab trap fishery had the highest co-occurrence scores, and associated entanglement risk, with all whale species included in the model. Confirmed entanglement reports were compared with model results.  Alignment of known entanglement locations with areas of higher co-occurrence scores supported the use of the co-occurrence model for assessment of whale entanglement risk off the U.S. west coast.  Research on the identified elevated risk areas, combined with the ability to trace gear continued gear research, and strengthened outreach to improve reporting, should improve the ability to minimize or mitigate the risk of large whale entanglements.  

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