Ecological niche of coastal Beaufort Sea fishes defined by stable isotopes and fatty acids

ABSTRACT: Little is known about the trophic ecology of freshwater, coastal and marine fish species that utilize coastal environments in the Beaufort Sea. In this study we use stable isotopes (SI) and fatty acid (FA) profiles to (1) characterize habitat and diet components of the ecological niche for 16 co-occurring fish species, (2) quantify niche overlap among these species and groups of species, and (3) identify resource partitioning and niche shift indicators for future monitoring. Ward’s cluster analysis of SI (δ13C, δ15N) results identified 3 representative isotopic groups that were consistent with known life-history groups: marine, freshwater-rearing and coastal fishes. Correspondence and Ward’s clustering analyses on FA profiles resulted in 5 FA groups that indicated feeding preferences and included: pelagic marine-feeding, benthic and pelagic brackish (both freshwater and marine)-feeding, benthic freshwater-feeding, benthic marine-feeding, and benthic brackish-feeding groups. Isotopic niche size and feeding preferences (FA) indicated generalist and specialist strategies that could be used as indicators for resource partitioning and niche shifts. Understanding the habitat use, diet, and trophic interactions among fish species is important in monitoring the Tarium Niryutait Marine Protected Area. Combining SI and FA tracers to quantify probability of niche overlap is a unique aspect of understanding species-specific niche interactions within the Beaufort Sea coastal environment, and our results contribute to understanding how these biotracers can contribute to current and future monitoring and management of this remote MPA.