California sea lions interfere with striped marlin hunting behaviour in multi-species predator aggregations

Abstract

The open ocean offers a suite of ecological conditions promoting the occurrence of multi-species predator aggregations. These mixed predator aggregations typically hunt large groups of relatively small and highly cohesive prey. However, the mechanisms and functions of these mixed predator aggregations are largely unknown. Even basic knowledge of whether the predator species' interactions are mutualistic, commensal or parasitic is typically missing. Moreover, recordings of attack and capture rates of marine multi-species predator aggregations, which are critical in understanding how and why these interactions have evolved, are almost completely non-existent owing to logistical challenges. Using underwater video, we quantified the attack and capture rates of two high-trophic level marine predators, California sea lions ( Zalophus californianus ) and striped marlin ( Kajikia audax ) attacking schools of fishes in the Southern California Current System, offshore the Baja California Peninsula. Recording over 5000 individual attacks across 13 fish schools, which varied in species, size and predator composition, we found that sea lions kleptoparasitized striped marlin hunts and reduced the frequency of marlin attacks and captures via interference competition. We discuss our results in the context of the phenotypic differences between the predator species and implications for a better understanding of multi-species predator aggregations. This article is part of the theme issue ‘Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes’.

Sailfish generate foraging opportunities for seabirds in multi-species predator aggregations

“…Classification of species as 'producers' or 'scroungers' has largely relied on the arrival time of the interaction partners and anecdotal observations from above and below the surface [12,40,41]. Two studies that quantified detailed data on attack and capture rates of one or two predator species, proposed a mutualistic and a kleptoparasitic relationship, respectively [3,4]…”

“…Thousands of predators of different species can gather in the same location and simultaneously predate upon large schools of prey [2]. Despite the ecological relevance of these multi-species predator aggregations and extensive literature documenting the co-occurrence of particular combinations of predator species, their synergistic or antagonistic nature is rarely assessed (but see [3,4]). This is likely due to difficulties quantifying predator behaviours such as attack and capture rates as well as the spatio-temporal positions of predators and prey in the wild.…”

“…This is likely due to difficulties quantifying predator behaviours such as attack and capture rates as well as the spatio-temporal positions of predators and prey in the wild. This means that the mechanisms that underlie the antagonistic or synergistic nature of predator interactions are also poorly understood [4].…”

“…Various marine predators are known to associate with each other, including for example: dolphins and tuna [5][6][7], seals and billfishes [4], humans and dolphins [8], sharks and trevally [9,10], dolphins and baleen whales [11,12]. However, most commonly studied are associations of large subsurface predators (e.g.…”