Meeting Abstract
Climate projections predict temperature increases for many freshwaters and also flow regimes that are seasonally increased and more stochastic. Predicting the future of fishes that inhabit these waters will require knowing how they deal with changes of both temperature and flow. Presently, predictions of species’ responses to climate change do not incorporate this knowledge. Fortunately, some species have already experienced the same changes predicted for climate disruption and we can learn from them. Impervious surface cover in cities causes greater surface run-off so that stream flows and temperatures are both greater and more stochastic. Urban fishes have been increasingly exposed to these changes over the past 200 years. The blacknose dace is found in some of the most urbanized streams, yet this fish is also abundant in nearby, rural streams. This sets up an intraspecific comparative experiment wherein one can test hypotheses concerning how the urban changes of temperature and flow have changed this species. Similarly, as the glaciers retreated from the island of Iceland over the past 10,000 years, they created a mosaic of freshwater habitats that vary substantially in both temperature and flow. A species indigenous to most of these waters is the Arctic charr, a fish known for its phenotypic plasticity which allows us to compare metabolism, performance and thermal tolerance of wild charr from waters of variant flow and temperature with cultured charr raised under a matrix of flow and temperature conditions in the laboratory for a single generation. Results to date have uncovered improved swimming performances and tolerance of thermal shock in urban dace populations, while wild charr from warm Icelandic streams have a temperature tolerance not inducible by a single generation of acclimation.
