Habitat characteristics and diel patterns of sand lance (Ammodytes spp) in coastal Newfoundland

Abstract

Fish select habitat based on many abiotic and biotic factors, with some species having narrow habitat requirements due to morphological traits. Fish of the genus Ammodytes (sand lance) are small schooling pelagic forage fish that lack a swim bladder and burrow into sandy substrate when not actively feeding to avoid predation and reduce energy expenditure. Sand lance species in the Pacific and Northeast Atlantic show diel shifts in feeding in the water column and burrowing, but diel patterns for species in the Northwest Atlantic remain unclear. The objectives of this study were to investigate sand lance habitat characteristics and diel behaviour during July–August 2013–2021 on the northeast Newfoundland coast. Integrating underwater camera surveys, sediment grabs, and hydroacoustics, sand lance were found associated with fine sediment (0.5–4 mm) that were < 11˚C (typically ~ 2˚C). Acoustic sand lance biomass in the water column tended to decline between the morning (09:00 Newfoundland Daylight Time, NDT) and late evening (23:00 NDT), while fish densities in sediment grabs peaked during the evening (~ 19:00 NDT) when buried fish more commonly had non-empty stomachs. Findings suggest that sand lance primarily fed in the water column during the day and burrowed in the evening once stomachs were full. Diel patterns were size-dependent, with a higher proportion of larger sand lance (≥ 150 mm) caught in sediments throughout the night, when smaller sand lance (< 150 mm) were absent from sediments. Overall, sand lance species in the Northwest Atlantic appear to exhibit similar habitat requirements and diel patterns to those in other regions.