Determining the Movements and Distribution of Anadromous Bering Ciscoes by Use of Otolith Strontium Isotopes

Abstract

AbstractMethods for tracking the movements and distribution of fishes have often involved expensive field logistics, which is compounded in remote regions such as Alaska. An alternative approach is to use the chemical signatures preserved in the otoliths of teleost fish to track their movement history. We used the strontium isotope signature (87Sr/86Sr) preserved in the freshwater portion of otoliths taken from Bering Ciscoes Coregonus laurettae to identify their natal river of origin and their movements. Bering Ciscoes spawn in freshwater rivers and rear in coastal marine waters. Just three spawning rivers are known for this species worldwide: the Yukon, Kuskokwim, and Susitna rivers. Rearing commonly occurs in coastal estuaries and lagoons along the Arctic coast of Alaska, the Yukon–Kuskokwim (Y–K) delta, and (rarely) the Alaska Peninsula. We compiled a set (n = 127) of Bering Cisco otoliths from fish caught in coastal marine habitats within each of these rearing areas. We measured the 87Sr/86Sr values from the freshwater portions of the otoliths and compared them to an established baseline of signatures for Bering Ciscoes sampled from the known spawning rivers. We found that 96% of the unknown‐origin specimens from the three rearing groups (Alaska Arctic coast, Y–K delta, and Alaska Peninsula) had 87Sr/86Sr values that were consistent with a Yukon River origin. The dominance of Yukon River‐origin fish in all rearing groups suggests that this population is considerably larger than the Kuskokwim River or Susitna River population. These data also indicate a widespread coastal distribution of Bering Ciscoes, with some individuals estimated to have traveled over 4,900 km between coastal rearing locations and the spawning habitat. Our approach illustrates that strontium isotopes can be used to determine the natal river and migration behavior for anadromous Bering Ciscoes of unknown origin.Received April 4, 2016; accepted August 12, 2016 Published online October 14, 2016