Salmonid fish and warming of shallow Lake Ellioavatn in Southwest Iceland

摘要

Fish are ectotherms, and hence their biological performance is dependent on the ambient water temperature. Because of climatically induced increases in water temperature, stenothermic, coldwater fish species are expected to be subject to various negative problems, including reduced growth, survival, and distributional range (REIST et al. 2006a, 2006b, CUSHING 1997). Few empirical studies have demonstrated how coldwater fish respond to recent climate change and warming, with some exceptions (e.g., KRISTENSEN et al. 2006), partly due to the complexity of Arctic ecosystems and biological variability of organisms, along with paucity of long-term, integrated hydro-ecological monitoring data (WRONA et al. 2006). Lake Ellioavatn, Southwest Iceland, is inhabited by Arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta), both coldwater fish species of the salmonid family ( REIST et al. 2006a). Catch statistics and biology of these fishes have been monitored by the Institute of Freshwater Fisheries for the past 2 decades (ANTONSSON & GUDBERGSSON 2000, ANTONSSON et al. 2005). Recent studies on physico-chemical variables in the lake showing high values of temperature, alkalinity, and aluminium concentrations have raised concerns for negative impacts on the Arctic charr. The population has been declining for the past 20 years and is currently very small (ANTONSSON & GUDBERGSSON 2000, GISLASON & EIKEIKSDOTTIR 2001, MALMQUIST et al. 2004). Recently, long-term data on lake temperature became available, with hourly recordings dating back to August 1988. The newly available temperature data provided us with an excellent opportunity to examine development of the lake temperature over the past 2 decades, and how population development and biology of the salmonids in the lake relate to temperature.