MEPS 499:157-175 (2014)  -  DOI: https://doi.org/10.3354/meps10632

ABSTRACT: This study presents the longest uninterrupted acoustic monitoring record available to date for the leopard shark Triakis semifasciata, providing novel insight into the fine-scale and long-term movement patterns of this species, and demonstrating that both sexes exhibit site-specific aggregation behavior and seasonal philopatry. Twenty females and 13 males were surgically fitted with coded acoustic transmitters and tracked for over 3 yr by underwater acoustic receivers spanning 120 km of coastline from San Clemente, CA, USA to the USA-Mexico border, with 2 receivers positioned at known aggregation sites in La Jolla and Del Mar, CA. Whereas females appeared to be particularly attracted to the La Jolla site, males exhibited strong site fidelity to Del Mar. Shark abundance at both sites was higher during the day than at night, particularly in late afternoon when water temperature was highest. Female abundance in La Jolla was highest in late June through early December, and was strongly positively correlated with sea surface temperature, consistent with the hypothesis that females aggregate in warm water to accelerate gestation. In addition, seasonal arrival of females to and departure from La Jolla were highly synchronous and coincided with the summer and winter solstices, respectively. In contrast, male abundance in Del Mar was highest in late April through early October and was positively correlated with both sea surface temperature and photoperiod. Lastly, both sexes exhibited strong seasonal philopatry, with 50.0% of females and 60.0% of males returning every year to their respective aggregation sites during the 3 yr study period.

KEY WORDS: Site fidelity · Acoustic telemetry · Sexual segregation · Marine reserve · Passive acoustic tracking · Diel behavior · Water temperature · Photoperiod · Fish aggregation