Feeding Ecology of Broadbill Swordfish (Xiphias Gladius) in the California Current [Oral]

Diet data can be used to quantify trophic links across time and space, and they are critical for effective ecosystem-based and climate-ready fisheries management. Diet patterns, by year, associated with the corresponding oceanographic conditions, can offer a tool for predicting future prey abundance and feeding behaviors in similar conditions. The feeding ecology of broadbill swordfish (Xiphias gladius) in the California Current was described during a time period of 16 years (2007-2022). Stomachs were collected by fishery observers aboard commercial drift gillnet boats and deep-set buoy gear. Prey were identified to the lowest taxonomic level possible and diet composition was analyzed using univariate and multivariate methods. Of 664 swordfish sampled (74 to 245 cm eye-to-fork length), stomachs contained remains from 77 prey taxa. Genetic analyses were conducted to identify prey that could not be identified visually. Overall diet consisted of cephalopods, epipelagic and mesopelagic teleosts. Jumbo squid (Dosidicus gigas) was the most important prey based on the geometric index of importance during the years 2007-2014. The range expansion of jumbo squid that occurred during the first decade of this century may explain their prominence in swordfish diet. Jumbo squid disappeared from the diet starting in 2015 while Pacific hake started to gain importance in 2011 and it has become one of the most important prey items in recent years. Northern anchovy was a rare species during 2007 and 2008 and was not present in the diet until 2016 when it started to gain importance and it has become a prominent prey in recent years. Market squid importance fluctuated in the diet by year, but proportional abundance was very high in 2017 and 2018. Swordfish diet also varied with body size and location. Jumbo squid, Gonatus spp. and Pacific hake (Merluccius productus) were more important for larger swordfish, reflecting the ability of larger specimens to catch large prey. Jumbo squid, Gon