MEPS 586:181-192 (2018)  -  DOI: https://doi.org/10.3354/meps12400

ABSTRACT: The roundnose grenadier Coryphaenoides rupestris is a benthopelagic fish distributed along the continental, island, and seamount slopes in the North Atlantic and along the Mid-Atlantic Ridge. Previous studies have indicated that C. rupestris consists of sub-populations across its distribution range, but no study has addressed small-scale population structuring at the scale of fjords. Here we study the population genetic structure of C. rupestris from fjords and coastal sites in south-western Norway using 8 microsatellite DNA markers. Genetic patterns were contrasted with environmental variables (geographic distance, bottom depth, sill depth, bottom salinity, bottom oxygen, and bottom temperature) and fish condition indices (length-weight, gonadosomatic index, and hepatosomatic index). We observed significant genetic heterogeneity across the study area (F_ST = 0.0297, p < 0.001), suggesting several populations occur at the scale of fjords or finer. The Skagerrak samples (2001, 2008, and 2016) did not differentiate and suggest that this area constitutes a temporally stable population unit. Population structuring in C. rupestris along the Norwegian coast seems to be influenced by geographic distance and Norway’s complex bathymetry, such as fjord sills, appear to limit its dispersal and migration. We found a strong positive correlation between genetic distance and geographic distance (Mantel test, r = 0.702, p = 0.001), bottom depth (r = 0.555, p = 0.014), and a trend with bottom temperature (r = 0.639, p = 0.070). C. rupestris is an overfished species that has been Red-Listed as Critically Endangered. Our findings have important management implications for the species.

KEY WORDS: Fjords · Roundnose grenadier · Connectivity · Population genetics