Abstract
Characterizing habitat suitability for a marine predator requires an understanding of the environmental heterogeneity and variability over the range in which a population moves during a particular life cycle. Female California sea lions (Zalophus californianus) are central‐place foragers and are particularly constrained while provisioning their young. During this time, habitat selection is a function of prey availability and proximity to the rookery, which has important implications for reproductive and population success. We explore how lactating females may select habitat and respond to environmental variability over broad spatial and temporal scales within the California Current System. We combine near‐real‐time remotely sensed satellite oceanography, animal tracking data (n = 72) from November to February over multiple years (2003–2009) and Generalized Additive Mixed Models (GAMMs) to determine the probability of sea lion occurrence based on environmental covariates. Results indicate that sea lion presence is associated with cool (<14°C), productive waters, shallow depths, increased eddy activity, and positive sea‐level anomalies. Predictive habitat maps generated from these biophysical associations suggest winter foraging areas are spatially consistent in the nearshore and offshore environments, except during the 2004–2005 winter, which coincided with an El Niño event. Here, we show how a species distribution model can provide broadscale information on the distribution of female California sea lions during an important life history stage and its implications for population dynamics and spatial management.
Highlights
Understanding how highly mobile marine predators select and prioritize habitats can be challenging
Characterizing habitat associations for a mobile marine predator can be challenging for animals whose movement patterns change among life stages
Modeling habitat suitability for spatially constrained foragers is a complex exercise because the options to respond to their environment are limited (Kappes et al, 2010; Pinaud & Weimerskirch, 2005)
Summary
Understanding how highly mobile marine predators select and prioritize habitats can be challenging. A depletion of foraging resources near the colony can lead to increased spatial overlap with fisheries, leading to both direct competition and indirect biological interactions (NMFS, 1997; Weise & Harvey, 2005) Such conflicts include human-related injuries (Goldstein, Johnson, Phillips, Hanni, & Fauquier, 1999), depredation (loss of commercial and recreational fish), incidental capture in fisheries or bycatch, and entanglement in fishing gear (Beeson & Hanan, 1996; Carretta & Chivers, 2004; Stewart & Yochem, 1987). Aspects of at-sea habitat use have been explored (Kuhn & Costa, 2014), our ability to broadly identify suitable foraging habitat of this central- place forager has been limited This is in part because the importance of prey species in sea lion diet fluctuates seasonally and annually, making direct observations that coincide with prey distribution difficult (Lowry et al, 1991; Melin et al, 2012; Orr et al, 2011). Given the importance of habitat use of breeding and provisioning females on population-level processes, our model can be used to connect at-sea distribution shifts to changes in population trends, as well as inform species protection and fisheries bycatch management efforts
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