Growth and reproductive characteristics of rarely observed resident female Dolly Varden (Salvelinus malma malma) in North America

Abstract

Among North American populations of northern form Dolly Varden (Salvelinus malma malma) exhibiting partial migration, the resident female life history is rarely encountered. Between 2012 and 2016, three sexually mature females confirmed as residents using otolith strontium analysis were captured from three rivers in the western Canadian Arctic (< 1% of residents sampled). Size-at-capture and size-at-age, estimated using otolith back-calculation, were compared to resident males and anadromous females. Fecundity, egg diameter, and gonadosomatic index (GSI) were compared to anadromous female current-year spawners. Resident females (fork length range 220–360 mm) tended to be among the largest-sized residents (two were > 90th percentile). Early size-at-age of resident females either exceeded or were among the largest sizes compared to resident males and pre-smolt anadromous females. Residents had similar fecundity predicted for length and egg size (range 3.5–4.2 mm) compared to anadromous, although GSI (range 13.2–17.4%) was inconsistent among populations. Interestingly, one resident female attained a greater size-at-capture and fecundity than the smallest anadromous current-year spawner. Our results suggest that conditional mating tactics of Dolly Varden can be expressed by both sexes in multiple populations, and increases understanding of Dolly Varden life history diversity and bet-hedging strategies in partially migratory populations.