The Evolutionary Ecology of Arctic Fishes

Abstract

... The general focus of my research is to identify genetic, ecological, and life history adaptations among Arctic marine fishes. The research can be divided into two main sections. The first concerns the life history and general biology of noncommercial Arctic marine species. The second examines the populations of Atlantic cod that persist in Arctic lakes well to the north of their current distribution in Canadian marine waters. ... In general, my research concerns the adaptations of Arctic fishes for survival in their unique environment, with a particular focus on life history traits. ... In my research, I will examine how these [life history trait] trade-offs relate to the demands and limitations of Arctic aquatic environments. ... I have not yet obtained specimens of noncommercial Arctic marine species at the time of this writing. However, an opportunity to work aboard a research trawler fishing for turbot in Davis Strait in the fall of 2003 promises to provide a great diversity of specimens for future study. ... Landlocked populations of Atlantic cod (Gadus morhua) are known from three coastal lakes in Frobisher Bay (Ogac Lake) and Cumberland Sound (Qasigialiminiq and Tariujarusiq Lakes). ... The objectives of this part of my research include the study of (i) basic physical, chemical, and biotic characteristics of Arctic lakes in which Atlantic cod occur, and (ii) aspects of these populations' biology, life history, and genetics. ... Field camps were established for about two weeks at each of Ogac, Qasigialiminiq, and Tariujarusiq Lakes during July and August 2003. Data on the length, weight, sex, maturity, liver weight, gonad weight, and stomach contents were collected from 100 cod from each lake. Tissue samples and otoliths were also collected for genetic and age/growth analysis, respectively. Underwater video was used to qualify benthic macrofauna and to observe cod behaviour and movement in all three lakes. Plankton tows were made ... to compare micro-invertebrate populations of the three lakes and compare the present population of Ogac Lake to that described ... for 1957-65. Bathymetric measurements by sonar were taken across a number of transects in both Qasigialiminiq and Tariujarusiq Lakes to compare them to Ogac Lake .... Salinity, temperature, and dissolved oxygen strata were measured in each basin of each lake, again to compare abiotic limnology across lakes and over time at Ogac Lake. Temperature data loggers were deployed near the outflow of each lake to measure the timing and frequency of tidal inflow during high spring tides. ... some preliminary results have been compiled. Like Ogac Lake, Qasigialiminiq and Tariujarusiq Lakes are salt meromictic lakes, although they are warmer than Ogac Lake at all depths, and surface salinity is higher at Tariujarusiq (7 per mil) than at the other two lakes (< 1 per mil). ... Cod in all three lakes mature at a large size, as previously reported for Ogac Lake .... Preliminary microsatellite DNA analysis at eight loci has revealed that cod in Ogac Lake exhibit remarkably low genetic variation compared to other Northwest Atlantic cod populations .... Genetic analyses of samples from Qasigialiminiq and Tariujarusiq Lakes are ongoing, but they are expected to reveal similar results. ... The completion of microsatellite DNA analysis for all three populations will conclude our comparisons of genetic variability and divergence, both among these landlocked populations and between these populations and marine cod stocks. We will then explore how long these populations have been isolated and from what marine stock they derive. ... Once age and growth data have been obtained from otolith analysis, we will attempt to relate variability in these features within and among the populations to biotic and abiotic differences among lakes. ...