Identifying subtidal burying habitat of Pacific sand lance (Ammodytes hexapterus) in the Strait of Georgia, British Columbia, Canada

Abstract

Pacific sand lance (Ammodytes hexapterus), an important prey species for many vertebrate predators in the northeast Pacific, lacks a swim bladder and relies on coarse sand substrates to bury in overnight and during the winter. Surprisingly little information is available describing the spatial distribution and extent of its burying habitat along the British Columbia coast. Thus, a habitat suitability model was developed for Pacific sand lance in the Strait of Georgia that considered information on shallow depths (<80m), high bottom current speeds (25–63cms−1) and coarse sand (0.25–2.0mm grain diameter). Overall, the model identified 6% of the study domain as suitable burying habitat, with the southern Strait containing the largest burying areas. By-catch data from mid-water trawl and purse seine sets was also used to map the location of pelagic schools of foraging sand lance. The persistent location of large Pacific sand lance by-catches over many years identified key foraging areas adjacent to several burying habitats. The median distance of 88 sand lance schools to coarse sand patches was 2km; 75% of the schools were found within 4.9km of coarse sand. The mapping of suitable burying and foraging areas in the Strait of Georgia will assist managers in guarding against anthropogenic activities that might impact the relatively uncommon and patchy habitats of a key coastal food-web species.