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The feeding ecology of broadbill swordfish (Xiphias gladius) in the California Current was described based on analysis of stomach contents collected by fishery observers aboard commercial drift gillnet boats from 2007 to 2014. Prey were identified to the lowest taxonomic level and diet composition was analyzed using univariate and multivariate methods. Of 299 swordfish sampled (74 to 245 cm eye-to-fork length), 292 non-empty stomachs contained remains from 60 prey taxa. Genetic analyses were used to identify prey that could not be identified visually. Diet consisted mainly of cephalopods but also included epipelagic and mesopelagic teleosts. Jumbo squid (Dosidicus gigas) and Gonatopsis borealis were the most important prey based on the geometric index of importance. Swordfish diet varied with body size, location and year. 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, Gonatus spp. and market squid (Doryteuthis opalescens) were more important in inshore waters, while G. borealis and Pacific hake predominated offshore. Jumbo squid was more important in 2007–2010 than in 2011–2014, with Pacific hake being the most important prey item in the latter period. Diet variation by area and year probably reflects differences in swordfish preference, prey availability, prey distribution, and prey abundance. The range expansion of jumbo squid that occurred during the first decade of this century may particularly explain their prominence in swordfish diet during 2007–2010. Some factors (swordfish size, area, time period, sea surface temperature) that may influence dietary variation in swordfish were identified. Standardizing methods could make future studies more comparable for conservation monitoring purposes

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