Aggregation site fidelity and movement patterns of the protected marine predator giant sea bass (Stereolepis gigas)

Abstract

Giant sea bass (Stereolepis gigas, Polyprionidae) are the largest reef-associated teleost in the northeastern Pacific, considered an important predator in Macrocystis kelp forest and rocky reef ecosystems. Because of the predictability of annual aggregations, giant sea bass (GSB) were fished throughout the twentieth century until they were nearly extirpated from southern California and Baja California, Mexico. To assess population recovery, acoustic telemetry was used to quantify spatiotemporal rhythmicity of GSB aggregations at Santa Catalina Island, California, USA. Thirty-two individuals were tracked for 498\xa0days over two consecutive spawning seasons in 2017–2018 and visual surveys were conducted monthly to estimate aggregation sizes. Aggregation behavior was documented from June–October and spawning most likely occurred at a pinnacle promontory from July–September. GSB exhibited residency to specific sites throughout the year and individuals showed fidelity to suspected spawning aggregation sites during the summer months. Ten (31%) GSB were detected at Santa Catalina Island year-round and 11 (34%) exhibited suspected annual spawning site fidelity. Four individuals (12%) were documented leaving the island during late fall/winter 2017 and returning in spring/early summer 2018, indicating partial seasonal migration and year-round fidelity to specific sites at Santa Catalina Island. This study provides a baseline of spatiotemporal movements and behavioral patterns that can be used to improve our understanding of GSB and enhance management for these and other large-bodied predatory fish species.