Life history differences between 2 anadromous populations of the northern form of the Dolly Varden (Salvelinus malma malma) in Bristol Bay in southwestern Alaska

Abstract

The Dolly Varden (Salvelinus malma), an iteroparous, facultatively anadromous Pacific salmonid, displays diverse life history and migration patterns. Using otolith microchemistry, we inferred that individuals sampled in the Nushagak Commercial Salmon Fishery Management District, Alaska (sample size [n]=30; mean fork length=597 mm), had entered saltwater at ages 4-7 and were in their first (26%) or second (74%) summer at sea. Most (88%) of the fish that had spent 2 summers at sea migrated in consecutive years, but 2 of them skipped a migration to marine waters, remaining in fresh water for an additional year after migrating to sea in their first year. Only 15% of the individuals with 2 summers at sea had anadromous mothers. In contrast, conspecifics sampled on the other side of Bristol Bay in the Egegik Commercial Salmon Fishery Management District started migrating at an earlier age, migrated more often, and more often had anadromous mothers. Together, these results highlight the differences in life history among Dolly Varden and indicate that freshwater rather than marine conditions influence life history patterns, at least for fish within the Nushagak District.