Stock structure and connectivity of capelin ( Mallotus villosus ) in Greenland: Otolith microchemistry used to track past whereabouts of a small, pelagic fish

• Main Author: Fink-Jensen, Peter
• Format: Book
• Language: English
• Published: DTU Aqua 2021
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; SDG 14 - Life Below Water; Arctic; Greenland
• Online Access: https://orbit.dtu.dk/en/publications/34f860f5-891e-4c5a-a53e-69e05fb43410; https://backend.orbit.dtu.dk/ws/files/262056727/Peter_Fink_Jensen_thesis.pdf

The overall aim of the research presented in this PhD thesis is to provide information on inshore stock structure, connectivity, and spatial dynamics of the small, pelagic fish species capelin ( Mallotus villosus ) in Greenland. Capelin is one of the most abundant species in the Arctic and has a central role in Arctic food webs. In Greenland, large schools of capelin appear at shallow water spawning sites in late spring and early summer. Their whereabouts the rest of the year are largely unknown. This study applies otolith (earstone) chemistry to investigate past whereabouts of capelin that spawn inshore in Greenland. Otoliths may serve as chronological records of ambient water chemistry exposure, and can therefore be used to distinguish between residence in environments that are chemically distinct. Chemical patterns of 14 different elements are examined for capelin otoliths collected from 19 different spawning localities along Greenland east and west coast. The project is divided into three studies that combine to address the projects main objectives. The first study identifies large-scale, regional differences in otolith chemistry, particularly for elements Li and Ba, which can be attributed to oceanographic differences in salinity along the coastline. This is used to form distinct chemical baselines for two west coast regions. In the second study, these baselines form the basis for examination of capelin whereabouts in the past. Multivariate classifications at high temporal resolution are used to evaluate if individual capelin have resided in one region or the other in the past. The results indicate that capelin have generally resided in the region where they were eventually caught, although seasonal variations in Li concentrations complicate the use of the baselines. Significant ambient Pb contrasts allow for comparison of otolith Pb between adjacent localities. The second study therefore progressed by zooming in on the use of otolith Pb as a tracer of ambient Pb. Differences in Pb concentrations for fish ...