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Characterizing patterns of opah (Lampris spp.) catch-per-unit-effort in the eastern North Pacific Ocean

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Abstract

This project examines opah catch in the North Pacific. The goal is to visually characterize temporal and spatial patterns in fishing effort, catch, and aggregate nominal catch-per-unit-effort (CPUE) for the Hawaii and California based deep-set pelagic longline fishery to see if it is possible to differentiate the spatial distributions of both opah species known to be in the North Pacific. It should be noted that the two species are not differentiated in the data and are recorded simply as generic “opah”. To examine patterns, analyses were performed using logbook data from 1996 to 2018 to summarize catch and effort information into 5O x 5O spatial blocks to form a grid across the fishery range. Average annual number of sets, catch, and aggregate nominal CPUE were visualized for the entire time series. The fishery has expanded significantly over the last 23 years from just around the Hawaiian Islands to encompassing most of the ocean between Hawaii and continental North America, outside the U.S. exclusive economic zone. Opah CPUE is highest in the northeastern extent of the fishery range, east of 150O W, with catch and CPUE steadily increasing from west to east. Prior DNA studies indicate that most smalleye opah (Lampris incognitus) are found near the California coastline and most bigeye opah (Lampris megalopsis) are found near Hawaii, which suggests that the North Pacific areas with high opah CPUE are likely dominated by smalleye opah.

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This item is under embargo until August 8, 2020.