Feeding Ecology of Pacific Sand Lance in the San Juan Archipelago

Abstract

Forage fishes such as Pacific Sand Lance Ammodytes personatus are a crucial link between lower and upper elements in marine food webs, as they transfer energy from plankton to higher trophic levels. Despite their importance to marine food webs, little is known about the population structure and feeding ecology of Pacific Sand Lance. In this study, we examined the population density and diet composition of Pacific Sand Lance as well as feeding patterns and movement in response to tidal, diel, and seasonal cycles in a prominent sand wave field in the San Juan Channel, Washington. A generalized linear model was applied to account for the corresponding effects of tidal, diel, and seasonal trends as well as habitat affinity related to substrate type. We showed that fish distributions were predominantly driven by sediment type and that time of day had a significant influence on foraging behavior with distinct crepuscular feeding patterns. Our results also provide evidence for the cessation of feeding over the fall transition and the onset of a winter dormant period, as observed by increased densities of fish within the sand wave field (177%), a marked increase in the number of empty stomachs (511%), and a significant decrease in condition factor. These trends correspond with the expectations that Pacific Sand Lances exhibit a winter dormant phase and burrow in sediments throughout the winter months to conserve energy and reduce predation risk during periods of low productivity. We anticipate our study to be a starting point for understanding the foraging ecology of the Pacific Sand Lance, particularly in the San Juan Archipelago and Salish Sea. The results of this study may improve the understanding of Pacific Sand Lance habitat and availability to pelagic predators, inform fisheries management, and increase the resolution of marine food web models.The transfer of energy between primary and higher trophic levels in marine ecosystems often occurs through a few species of highly abundant, small forage fishes (Cury et al. 2000). As such, forage fishes are a crucial link between lower and upper elements in the food chain as they transfer energy from primary producers (e.g., phytoplankton) and secondary consumers (e.g., zooplankton) to higher trophic levels (e.g., piscivorous fishes, seabirds, and marine mammals) (Robards et al. 1998;Harvey et al. 2010). These fishes may also channel energy flow between various marine habitats, as many forage fish species occupy intertidal and subtidal communities . Variation in the abundance of forage fish populations can significantly impact marine ecosystems (Bargmann 1998). Thus, despite relatively few focused studies on these taxa, planktivorous fishes are an important component driving trophic dynamics in many marine and coastal ecosystems (Pikitch et al. 2012).

Intertidal beach habitat suitability model for Pacific sand lance (Ammodytes personatus) in the Salish Sea, Canada

“…Pacific sand lance, Ammodytes personatus (sand lance), are small (<25 cm fork length), short-lived forage fish that play a key role in coastal marine ecosystems (Sisson and Baker 2017;Staudinger 2020). Sand lance support trophic structures of several culturally and ecologically important species such as salmon, seabirds, and whales, and are known prey for more than 100 predators Zamon 2000).…”