The influence of global climate change on growth and population dynamics of zooplanktivorous whitefish (Coregonus sp.)
Final Report Abstract
We analysed the influence of climate variability on year-class strength of whitefish in Lake Constance and found evidence that warmer temperatures will most likely result in stronger year-classes. Whereas for several decades the notion prevailed that growth of lake whitefish depends mainly on lake phosphorous content, we could show that standing stock biomass controls whitefish growth much stronger than nutrient content. Therefore, stronger year-classes will lead to slower growth of whitefish through increased intraspecific competition for food. As a response to increased competition for food, whitefish tended to distribute to deeper and hence colder water during summer and autumn in recent years when standing stock biomass was high and food supply was low after the lake had returned to oligotrophic conditions. Furthermore, we found evidence that the strong size-selective harvest of the stock during several decades elicited an evolutionary response, i.e. fish with slower growth contributed disproportionately to future generations and consequently somatic growth rate declined. The whitefish stock in Lake Constance is supported by massive stocking with hatchery-bred larvae. The spawners which are used to supply the hatcheries with fertilized eggs are fished with gill nets during spawning time. This practice tends to select females with higher investment into reproduction, which is achieved at the cost of somatic growth. Changes in female fecundity during the last decades indeed suggest that this may be another mechanism how size-selective harvest selects for slower somatic growth. A definitive proof for genetic changes in the whitefish stock is still pending, but comparing the growth of whitefish larvae produced by females with a different growth history suggests a genetic component to the growth potential of lake whitefish.
Publications
- (2007). Influence of climate variability on whitefish (Coregonus lavaretus) year-class strength in a deep, warm monomictic lake. Oecologia 151: 521-529
Straile, D., Eckmann, R., Jüngling, T., Thomas, G. & Löffler, H.
- (2007). The influence of eutrophication and population biomass on common whitefish (Coregonus lavaretus) growth - the Lake Constance example revisited. Canadian Journal of Fisheries and Aquatic Sciences 64, 402-410
Thomas, G. & Eckmann, R.
- (2009). Human-induced changes in the reproductive traits of Lake Constance common whitefish (Coregonus lavaretus). Journal of Evolutionary Biology 22: 88-96
Thomas, G., Quoß, H., Hartmann, J. & R. Eckmann
- (2009). Long-term anthropogenic impacts on the whitefish (Coregonus lavaretus L.) stock of Lake Constance. Dissertation, Univ. Konstanz, 97 pp.
Thomas, G.
