Bait loss and its potential effects on fishing power in pelagic longline fisheries

We analyzed 1950s survey data with generalized estimating equations (GEEs) to quantify factors that influence the rate that bait is lost from pelagic longlines. Hook depth, bait species, local tuna abundance, and the timing of longline operations strongly influenced loss rates. Loss rates increased with tuna abundance and soak time. They declined with hook depth and were low for firm-bodied bait, such as squid. Many longliners began targeting bigeye tuna with deep longlines in the mid 1970s and have used squid bait since the 1980s. This may have resulted in increased fishing power, with important implications for the estimation of abundance from catch and fishing effort data.