Standardization of the swordfish Xiphias gladius catch per unit effort data caught by the Hawaii-based longline fishery from 1994-2016 using generalized linear models

The swordfish (Xiphias gladius) catch per unit effort for the Hawaii-based longline fishery was standardized from the Pacific Islands Regional Observer data set. The fishery was divided into the tuna-targeting deep-set sector and the swordfish-targeting shallow-set sector. Additionally, the shallow-set sector was standardized in two time periods: an early period (1995-2000) and a late period (2005-2016) because the shallow-set fishery was closed from 2001 to 2004, and regulations caused changes in the fleet operations thereafter. Four different models were evaluated to standardize the CPUE for each time series: the delta-lognormal model, the negative binomial model, the zero-inflated negative binomial model, and the Poisson model. The delta-lognormal model provided the best model fits and explained the most percent deviance of those evaluated. The models explained between 26 and 65% of the deviance in the shallow-set sector and 35% of the deviance in the positive catches for the deep-set sector, but only 4% of the proportion of positive catches in the deep-set sector. The shallow-set standardized annual CPUE values show an increase in catch rates in the early period followed by a peak in 2006 after the closure. CPUE values increased again from 2010 to the present. The CPUE values for the deep-set sector were relatively flat and had high variability. Michelle Sculley, Annie Yau, Maia Kapur. "Issued 18 May 2018." Includes bibliographical references (pages 8-10). 2018 NMFS (National Marine Fisheries Service) PIFSC (Pacific Islands Fisheries Science Center) Library http://doi.org/10.7289/V5/WP-PIFSC-18-001 Public Domain 1862