Exempted Testing of Deep-set Buoy Gear and Concurrent Research Trials on Swordfish, Xiphias gladius, in the Southern California Bight

Abstract

Research and exempted fishery trials were performed off the U.S. west coast using deep-set buoy gear (DSBG), an artisanal gear type designed to target swordfish, Xiphias gladius, below the thermocline during the day. All trials were performed within the Southern California Bight (SCB) under an exempted fishery permit (EFP) recommended by the Pacific Fisheries Management Council (PFMC) and authorized by the National Marine Fisheries Service (NMFS). Six cooperative fishermen were outfitted with uniform gear sets and performed 344 standardized deployments (10 individual buoys deployed for 8 h) which produced 2,795 buoy soak hours. The collective catch resulted in a marketable catch rate of ~97%. Swordfish comprised >80% of the total catch, with 611 individuals harvested over the two seasons of the EFP. Bigeye thresher sharks, Alopias superciliosus, were the second most common species totaling ~16% of the EFP catch. The average daily swordfish catch rate was 1.75 swordfish/8-h set and varied by year and cooperative vessel. Catch rates and composition were similar to previous and erations, with the latter two fisheries only occurring in a few select locations (Hanan et al., 1993; Coan et al., 1998; Ward et al., 2000). Although swordfish are more accessible near the surface at night, this time and depth also results in high spatial overlap with nontarget species (Beverly and Robinson, 2004; Gilman et al., 2006; Sepulveda et al., 2014). In particular, shallow-set swordfish fisheries have been routinely scrutinized by conservation groups for their lack of selectivity and high incidence of interaction with species of special conservation concern (i.e., sea turtles, marine mammals, and sea birds; Gilman et al., 2007). Within the exclusive economic zone off California ( CA EEZ), the primary gear type used to harvest swordfish is the California drift gillnet (DGN), a technique that has received regulatory scrutiny over its lack of selectivity and past history of interactions with species of special concern (i.e., marine mammals and sea turtles; Carretta et al., 2004). Over the past three decades, the DGN fleet has declined to historic lows in participation, landings, and revenue, with recent interactions with protected species threatening further concurrent research findings and contrasted shallow-set nocturnal buoy gear experiments performed during the same seasons. Nocturnal shallow-set research trials performed adjacent to EFP activities revealed low target (~9% swordfish) and high (>80%) non-marketable catch. Juvenile blue sharks, Prionace glauca, made up >76% of the total nocturnal catch. Collective DSBG trials to date suggest that daytime deep-setting within the SCB may provide an additional opportunity for west coast fishermen to access a domestic resource.