157 National Marine Fisheries Service Fishery Bulletin First U.S. Commissioner established in 1881 of Fisheries and founder NOAA of Fishery Bulletin Abstract—Yellowtail jack (Seriola Revisiting the life history of yellowtail jack dorsalis) are highly prized game fish within the Southern California Bight (Seriola dorsalis) in the Southern California Bight: (SCB). Despite the popularity of this species, life history and demographic new evidence for ontogenetic habitat shifts and information for it is scant, with one regional differences in a changing environment previous biological examination and no population assessments. For the study described here, we used modern ana- Noah Ben- Aderet (contact author) lytical techniques, updating historical Erin M. Johnston analyses, applied stable isotope anal- Richard Cravey ysis to investigate ontogenetic habitat Stuart A. Sandin shifts, and established a novel relation- ship of opercular length to fork length. We sampled 256 yellowtail jack across Email address for contact author: [email protected] the SCB and Baja California, Mexico, during 2014–2016. Sizes ranged from Center for Marine Biodiversity and Conservation 22.7 to 162.7 cm fork length with esti- Scripps Institution of Oceanography mated ages of 1–22 years. Body size University of California, San Diego affected diet, with larger fish consum- 9500 Gilman Drive ing a greater diversity of prey. Across La Jolla, California 92083- 0202 all samples, we recorded 19 prey spe- Present address for contact author: Fisheries Resources Division cies; the pelagic red crab (Pleuroncodes Southwest Fisheries Science Center planipes), found in 23% of stomachs, National Marine Fisheries Service, NOAA was most prevalent. Coastal pelagic 8901 La Jolla Shores Drive fish species, detected in 62% of stom- La Jolla, California 92037 achs, made up the most common group. Larger yellowtail jack were more δ15N enriched, indicating increasing tro- phic position, and δ13C levels signify an inshore–offshore habitat transition after maturity. Our results define yel- lowtail jack from the SCB and Baja Across their global distribution, caran- Total yearly recreational catch of yel- California as one contiguous population gid fish species are highly prized as lowtail jack in California is often at least with consistent ontogenetic variation both game and food fish. Prominent one order of magnitude greater than the in diet, trophic position, and growth among this group are the several entire commercial take for the same rate. However, fish from remote areas species in the genus Seriola, whose year (National Marine Fisheries Service, were older and larger, perhaps indicat- members are known commonly as annual commercial landings statistics, ing de facto fishing refuges. yellowtail, amberjack, rock salmon, or release 3.0.4.0, available from website, sailor’s choice. These species are large, accessed March 2019; Recreational highly mobile, and predatory, in most Fisheries Information Network, total subtropical and temperate boundary mortality by state, available from current ecosystems (Vergani et al., website, accessed March 2019). This 2008; Miller et al., 2011). Along the discrepancy is evident in angler enthu- western coast of North America, the siasm as well, as indicated by signifi- yellowtail jack (S. dorsalis) (formerly cant increases in the number of anglers S. lalandi; see Martinez- Takeshita venturing out to target yellowtail jack et al., 2015) ranges from Cabo San immediately after increased recre- Manuscript submitted 11 July 2019. Lucas in Baja California Sur, Mexico, ational catches are reported (Dotson and Manuscript accepted 19 May 2020. north to Point Conception, California Charter, 2003). This increase in angling Fish. Bull. 118:157–170 (2020). Online publication date: 3 June 2020. (Baxter, 1960). Within U.S. territorial pressure also has residual effects on doi: 10.7755/FB.118.2.5 waters, yellowtail jack are most abun- other, co- occurring species (Sutton and dant in the U.S. portion of the Southern Ditton, 2005). The views and opinions expressed or California Bight (SCB), a term used to Although yellowtail jack captivate implied in this article are those of the denote the coastline stretching from the angling public, aside from a small author (or authors) and do not necessarily reflect the position of the National Point Conception south to Cabo Colo- study sampling fewer than 50 individu- Marine Fisheries Service, NOAA. net in Baja California, Mexico. als for stable isotope analysis (Madigan 158 Fishery Bulletin 118(2) et al., 2018), there has been no research on their life his- in the SCB and establish a baseline for more targeted tory, movement patterns, or population structure along the investigation into the biology and ecology of the yellowtail California coast since the mid-1950s (Baxter, 1960). Improv- jack at the current northern extent of its range. ing our understanding of the biology of yellowtail jack along the western coasts of the United States and Mexico is a crit- ical foundation for managing this taxon for fisheries value Materials and methods (both for sport and as food), ecosystem benefits, and poten- tial in aquaculture (Sicuro and Luzzana, 2016). Study species Responding to the prominence of yellowtail jack in landings of nearshore fisheries in southern California This study focuses on the coastal population of yellowtail and Baja California after World War II, the California jack in the northeastern Pacific Ocean. This species was Department of Fish and Game (now the Department of originally named S. dorsalis by Theodore Gill in 1863, then Fish and Wildlife) completed a detailed study on the biol- grouped together with S. lalandi in 1990 by Smith-V aniz ogy and demography of yellowtail jack, as well as on their et al. (Smith- Vaniz, 1986; Smith- Vaniz et al., 1990). There movements along the California and Mexico coastlines is currently some disagreement as to the name of species (Baxter, 1960). This work was a comprehensive descrip- of yellowtail jack in the eastern Pacific Ocean, with con- tion of the fish population during 1952–1957, with large tradictory molecular findings from Premachandra et al. sample sizes linked to the output of the prodigious fish- (2017) and Martinez- Takeshita et al. (2015). Although we eries yield at the time. However, the work lacked spatial acknowledge the controversy, we proceed here as per rec- resolution, for example, with no designation among fish ommendations in Martinez- Takeshita et al. (2015) and use caught in offshore versus inshore habitats. Furthermore, S. dorsalis as the scientific name for this species. practically all fish were sampled or tagged along central Baja California, as opposed to within the SCB. Although Sample collection central Baja California is the center of abundance for yel- lowtail jack and oceanographically similar to southern A total of 271 yellowtail jack, ranging in fork length (FL) California (Jackson, 1986; Bograd and Lynn, 2003), the from 22.7 to 162.7 cm (mean: 79.8 cm; Suppl. Table), were human population of southern California has been, and collected aboard CPFVs and private fishing vessels by hook remains, higher than that of Baja California, with distinct and line between July 2014 and September 2016, a period anthropogenic pressures, including relatively higher rec- of time that encompassed an anomalous warmwater event reational fishing pressure and nearshore eutrophication and a strong El Niño–Southern Oscillation (ENSO) (NOAA from urban and agricultural runoff (Schiff et al., 2000). Climate Prediction Center, Oceanic Niño Index cold and Yellowtail jack are believed to migrate seasonally into warm episodes by season, available from website , accessed the SCB, moving northward as the water warms during January 2019). We conducted sampling at 10 locations the summer (rarely traveling north of Point Conception, within the SCB and along the Baja California coastline in except in highly anomalous warm years; Pearcy, 2002) an attempt to collect samples from as much of the range and retreating south along the Baja California coastline of the yellowtail jack as possible. We grouped those loca- during the winter and spring (Baxter, 1960). Along the tions into 3 regions: inshore, offshore, and island (Fig. 1). route of their cross- border migrations, these fish encoun- It is important to note that yellowtail jack routinely move ter a diverse array of anthropogenic pressures, including between these assigned regions. the world’s largest fleet of commercial passenger fishing Straight FL and opercular length (OL) were recorded vessels (CPFVs) operating in the SCB (Love, 2006). and used to calculate an OL- to- FL scaling relationship The combination of increased human interactions and (number of samples [n]=151). This relationship enabled other anthropogenic effects with changed marine condi- estimation of FL for samples taken from heads or partial tions within the SCB in the past 60 years necessitated frames of yellowtail jack obtained after processing aboard a revisiting of the life history of yellowtail jack. Further, CPFV or as donations by anglers. These samples were often despite technical advances in fisheries research methods, easier to obtain and reduced the amount of fish sacrificed Baxter’s (1960) findings for age, growth, and diet are still only for sampling purposes. In addition to measurements, used by fisheries managers in the United States today. sagital otoliths were extracted for age estimation, a plug of Investigating the life history