Intrinsic factors influence the timing of arrival of capelin (Mallotus villosus) to spawning grounds in coastal Newfoundland

Capelin (Mallotus villosus) is an important forage fish species in many northern marine ecosystems and, thus, is the primary prey species of many top predators. On the Newfoundland shelf, capelin undergo extensive inshore migrations (>350 km) from offshore areas to coastal spawning grounds in the spring, where the timing of inshore arrival is highly variable. We investigated the influence of intrinsic factors (i.e., length, age, spawning experience) and proxies for extrinsic factors (i.e., environmental conditions via otolith chemistry; diet via stable carbon and nitrogen isotope ratios) on the individual-level timing of arrival of capelin at spawning sites on the northeast coast of Newfoundland during July 2012 and 2013. Despite high inter-annual and sex-based variation in almost all factors examined, intrinsic factors varied with timing of arrival at spawning sites, with larger, older male and female capelin arriving first at coastal spawning sites followed by smaller, younger capelin. Alternately, proxies of extrinsic factors did not vary with timing of arrival. Our findings suggest that selectively exploiting early-arriving fish may impact the age/size structure of the population, potentially leading to increased variability in the timing of spawning at the population level and possibly recruitment.