|Document Type:||Journal Article|
|Title:||Differential growth in estuarine and freshwater habitats indicated by plasma IGF1 concentrations and otolith chemistry in Dolly Varden charr Salvelinus malma|
|Author:||Morgan H. Bond, Brian R. Beckman, Larissa Rohrbach, T. P. Quinn|
|Journal:||Journal of Fish Biology|
Many anadromous fishes rear in freshwater lakes and streams, consuming primarily terrestrial and aquatic invertebrates before leaving those habitats for estuarine and eventually marine habitats where feeding opportunities are generally increased. However, the timing and duration of migration trades off the relative safety of freshwater for the increased growth potential of estuarine and marine habitats. The use of estuarine habitats varies among species and life history types, from use as a migration corridor to oceanic habitats, to extensive use of estuarine areas during seaward migration or exclusive use of estuaries for marine feeding. Facultatively anadromous species are informative for comparisons of growth between similar age classes in freshwater and estuarine habitats. A combination of otolith microchemistry to indicate each fish’s recent habitat use, and plasma concentrations of insulin-like growth factor 1 (IGF1) as an index of recent growth to demonstrate differences in growth and habitat use by Dolly Varden charr Salvelinus malma occupying both freshwater and estuarine habitats in southwest Alaska. Extensive sampling in all habitats revealed that fish had higher IGF1 levels in estuarine habitats than in Chignik Lake throughout the summer, and that the growth rates in different habitats within the estuary varied seasonally. In addition, otolith microchemistry indicated differentiation in estuarine habitat use among individual S. malma throughout summer months. Although growth in the estuary was higher than in freshwater in nearly all sites and months, the benefits and use of the estuarine habitats varied on finer spatial scales. Therefore, this study further illustrates the diverse life histories of S. malma and indicates an evaluation of the benefits of marine waters needs to include sub-estuary scale habitat use.