During the breeding season, seabird foraging trips are constrained by nest attendance schedule and are necessarily colony centred. Oceanographic cues play a major role in the choice of foraging areas to minimize the time spent away from the nest. Here, we analysed the foraging tracks of Black‐vented Shearwaters Puffinus opisthomelas during the incubation and chick‐rearing periods of 2016 and 2017 at Isla Natividad (Mexico). We applied expectation‐maximization binary clustering to track data to clusterize different behaviour patterns during foraging flights. We then applied binary generalized linear mixed models to characterize of foraging areas based on of environmental variables. We finally used kernel estimation techniques to describe main foraging areas. In 2016, breeding shearwaters used two core areas for foraging and resting on the water; the core area delineated by males was located northward from the colony in the Vizcaino Bay and the core area for females was located southward from the colony at the entrance of San Ignacio Lagoon. In 2017, males and females used the same areas with no evident segregation. Our study provided the first information on Black‐vented Shearwater foraging areas during the breeding season and indicated that sexual segregation within coastal waters off the central Baja California Peninsula might be a foraging strategy during years of warmer ocean, likely less productive regimes. Factors including ocean‐climate‐mediated sexual segregation at sea, leading to interannual variation in foraging areas, should be considered when evaluating management actions intended to protect critical foraging habitats for Black‐vented Shearwaters.

We analyzed the response of fish larvae assemblages to environmental variables and to physical macro- and mesoscale processes in the Gulf of California, during four oceanographic cruises (winter and summer 2005 and 2007). Physical data of the water column obtained through CTD casts, sea surface temperature, and chlorophyllasatellite imagery were used to detect mesoscale structures. Zooplankton samples were collected with standard Bongo net tows. Fish larvae assemblages responded to latitudinal and coastal-ocean gradients, related to inflow of water to the gulf, and to biological production. The 19°C and 21°C isotherms during winter, and 29°C and 31°C during summer, limited the distribution of fish larvae at the macroscale. Between types of eddy, the cyclonic (January) registered high abundance, species richness, and zooplankton volume compared to the other anticyclonic (March) and cyclonic (September). Thermal fronts (Big Islands) of January and July affected the species distribution establishing strong differences between sides. At the mesoscale, eddy and fronts coincided with the isotherms mentioned previously, playing an important role in emphasizing the differences among species assemblages. The multivariate analysis indicated that larvae abundance was highly correlated with temperature and salinity and with chlorophyllaand zooplankton volume during winter and summer, respectively.

The sailfish Istiophorus platypterus is one of the most common billfish species in the Mexican Pacific. Information about its feeding habits in the coastal region of Acapulco, Guerrero is extremely limited. In the present study we quantified the diet of sailfish, based on captures made from March 2008 to December 2009 by the sport fishing fleet of Acapulco. We analysed a total of 561 stomachs, of which 254 contained food (45%). The size interval of examined specimens was between 101 and 212 cm postorbital length and between 15 and 47 kg total weight. In general, teleosts were the most important prey, followed by cephalopods. According to index of relative importance, the most important species in the diet were the fish Auxis thazard (63.04%) and Fistularia commersonii (6.62%), followed by the cephalopod Octopus spp. (4.58%). There were no significant differences in the diet by sex (males and females), sexual maturity (immature and mature), or by season (warm and cold seasons). In all cases the most important prey species was A. thazard. We conclude that the sailfish I. platypterus off Acapulco behaves as a specialist predator because, despite the consumption of a high number of prey items, it feeds preferentially on a reduced number of prey species that form schools, and are available and abundant in the ocean.

The Gulf of Ulloa, a highly productive area off the western coast of Baja California Peninsula, is examined for five successive years (2003–2007) by using satellite data and seasonal net primary productivity estimates obtained by a vertical generalized production model. The results clearly identify a seasonal signal of coastal upwelling in productivity estimates. Highest values occur from May to June and sometimes July. We also find influence of an equatorward coastal current able of transporting water from neighboring north upwelling areas to the Gulf of Ulloa in winter–spring. This flow contributes to increase the seasonal net primary productivity. The opposite occurs in summer, when a warm poleward current of tropical characteristics arrives to the region. Our findings reveal that such warm coastal current suppressed the productivity in the whole

The Guadalupe fur seal (GFS) currently is recovering from near extinction and prey availability is an important factor. Scat and stable isotope analyses (SIA) were used to assess GFS foraging on Guadalupe Island during 2013-2016. This period was characterized by normal (2013) ocean temperatures followed by warm conditions (2014-2016). Scat samples (~40/year) were collected for prey identification. Additionally, lanugo samples from 1-month-old pups (50/year) were processed for SIA (δ 13 C/δ 15 N). Interannual prey preferences were identified (ANOSIM, p < .05), including significant differences between 2013 and the anomalous years. The most important prey species among these years was the jumbo squid; followed by the neon flying squid (2014-2016). The GFS diet was more specialized in 2013-2015 and more generalized in 2016. Prey from higher trophic levels (determined by scat analysis) were