Will northern fish populations be in hot water because of climate change?

Abstract

Predicted increases in water temperature in response to climate change will have large implications for aquatic ecosystems, such as altering thermal habitat and potential range expansion of fish species. Warmwater fish species, such as smallmouth bass, Micropterus dolomieu, may have access to additional favourable thermal habitat under increased surface-water temperatures, thereby shifting the northern limit of the distribution of the species further north in Canada and potentially negatively impacting native fish communities. We assembled a database of summer surface-water temperatures for over 13 000 lakes across Canada. The database consists of lakes with a variety of physical, chemical and biological properties. We used general linear models to develop a nationwide maximum lake surface-water temperature model. The model was extended to predict surface-water temperatures suitable to smallmouth bass and under climatechange scenarios. Air temperature, latitude, longitude and sampling time were good predictors of present-day maximum surface-water temperature. We predicted lake surface-water temperatures for July 2100 using three climate-change scenarios. Water temperatures were predicted to increase by as much as 18 1C by 2100, with the greatest increase in northern Canada. Lakes with maximum surface-water temperatures suitable for smallmouth bass populations were spatially identified. Under several climate-change scenarios, we were able to identify lakes that will contain suitable thermal habitat and, therefore, are vulnerable to invasion by smallmouth bass in 2100. This included lakes in the Arctic that were predicted to have suitable thermal habitat by 2100.

Effects of differential habitat warming on complex communities

“…3B). Note that our findings do not discount the previous findings that competitors may act to decouple lake trout from near-shore fish production (22), nor that the distribution of bass is restricted by climate (26). In fact, bass are more likely to be present on average in our warmer study lakes (F = 4.393, n = 54, P = 0.041).…”

“…Smallmouth bass (Microterus dolomieu) and walleye (Sanders vitreus) are apex predators that inhabit the near-shore zone in several lake trout lakes in our study area. Because these species are expected to benefit from warmer summer temperatures over the climate range of our study (26), they may be an indirect cause of the overall decoupling effect observed across the climate gradient. In contrast to the prediction that warmwater predators are the primary driver of decoupling across a warming climatic gradient, our analysis of lakes without bass and walleye shows a similar if not stronger relationship between warming and the decoupling of lake habitats (Fig.…”

“…A key habitat feature of boreal lakes is thermal stratification, an effect of antagonistic physical forces of mixing by wind energy and resistance to mixing by solar heating that separates cold, more dense water (hypolimnion) from warmer, less dense surface water (epilimnion) (25). The stratification process creates a potential for temperature differentials between deeper offshore and shallower near-shore subhabitats within a lake, as temperatures remain relatively constant in deep habitats, whereas shallower near-shore temperatures are strongly influenced by air temperatures (26). Monitoring in the boreal region (27,28) has shown that rising air temperature warms surface waters, accelerates the stratification process, and extends the duration of stratification; thus, air temperature is a primary determinant of lake thermal heterogeneity.…”

Morphology, sexual dimorphism and size at maturation in topmouth gudgeon (Pseudorasbora parva) from the heated Lake Licheńskie (Poland)

“…Besides that, global climate change will probably cause warmer water temperatures in northern-latitude lakes. This may cause seasonally stressful conditions for coldwater-adapted fish species, but may provide suitable thermal conditions to allow non-native warmer fish species (as well as the other organisms) to thrive in these lakes (Sharma et al, 2007). From this point of view, the Lake Licheńskie gives us a unique option to imagine the composition of future fish communities in the present coldwater lakes.…”

Predicting distribution patterns and recent northward range shift of an invasive aquatic plant: Elodea canadensis in Europe

“…In this study we used the July temperature and the water defi cit in late summer as surrogates for direct measurements of the temperature in inland water bodies. Earlier studies have found especially the July air temperature to be a good predictor of maximum surface-water temperatures (Mohseni et al 2003, Sharma et al 2007). Water defi cit in late summer summarises the interactions between temperature and precipitation and thus also has the potentiality to indicate landscapes where the water levels in many lakes can become low, and consequently growing conditions can become more readily overly warm for Elodea canadensis.…”