The role of winter phenology in shaping the ecology of freshwater fish and their sensitivities to climate change

Abstract

Thermal preference and performance provide the physiological frame within which fish species seek strategies to cope with the challenges raised by the low temperatures and low levels of oxygen and food that characterize winter. There are two common coping strategies: active utilization of winter conditions or simple toleration of winter conditions. The former is typical of winter specialist species with low preferred temperatures, and the latter is typical of species with higher preferred temperatures. Reproductive strategies are embodied in the phenology of spawning: the approach of winter conditions cues reproductive activity in many coldwater fish species, while the departure of winter conditions cues reproduction in many cool and warmwater fish species. This cuing system promotes temporal partitioning of the food resources available to young-of-year fish and thus supports high diversity in freshwater fish communities. If the zoogeographic distribution of a species covers a broad range of winter conditions, local populations may exhibit differences in their winter survival strategies that reflect adaptation to local conditions. Extreme winter specialists are found in shallow eutrophic lakes where long periods of ice cover cause winter oxygen levels to drop to levels that are lethal to many fish. The fish communities of these lakes are simple and composed of species that exhibit specialized adaptations for extended tolerance of very low temperatures and oxygen levels. Zoogeographic boundaries for some species may be positioned at points on the landscape where the severity of winter overwhelms the species' repertoire of winter survival strategies. Freshwater fish communities are vulnerable to many of the shifts in environmental conditions expected with climate change. Temperate and northern communities are particularly vulnerable since the repertoires of physiological and behavioural strategies that characterize many of their members have been shaped by the adverse environmental conditions (e.g. cool short summers, long cold winters) that climate change is expected to mitigate. The responses of these strategies to the rapid relaxation of the adversities that shaped them will play a significant role in the overall responses of these fish populations and their communities to climate change.

Annual Changes in Seasonal River Water Temperatures in the Eastern and Western United States

“…For example, spring spawning fishes could spawn earlier with shorter, warmer winters [32]. In fact, it is increasingly recognized that understanding the seasonal variability in climate change effects may be important when attempting to understand current dynamics and for predicting effects under future scenarios, particularly in fish and wildlife populations [33]. For example, Kanno et al [34] found that seasonal patterns in air temperature and precipitation, both of which are predicted to change under climate warming, were important drivers of survival and reproduction of eastern brook trout.…”

Historical Trends, Drivers, and Future Projections of Ice Phenology in Small North Temperate Lakes in the Laurentian Great Lakes Region

“…As many species rely on a combination of photoperiod and thermal cues as triggers for critical life history events (e.g., spawning, larval emergence), changes in ice cover phenology may produce detrimental ecological mismatches [65]. For example, fall spawning fish species may be vulnerable to a warmer incubation period, promoting earlier spring hatching and potential starvation if the spring production pulse is not similarly responsive [67]. During warmer, longer summers, cold-water species will be increasingly squeezed between warming surface waters and deep anoxic habitats [67].…”

“…For example, fall spawning fish species may be vulnerable to a warmer incubation period, promoting earlier spring hatching and potential starvation if the spring production pulse is not similarly responsive [67]. During warmer, longer summers, cold-water species will be increasingly squeezed between warming surface waters and deep anoxic habitats [67]. As winter conditions become less severe, aquatic communities will shift from being dominated by winter specialists to species that thrive in warmer, brighter, and more productive environments [4,67].…”

“…During warmer, longer summers, cold-water species will be increasingly squeezed between warming surface waters and deep anoxic habitats [67]. As winter conditions become less severe, aquatic communities will shift from being dominated by winter specialists to species that thrive in warmer, brighter, and more productive environments [4,67].…”

Ecological impacts of winter water level drawdowns on lake littoral zones: a review

“…The loss of vegetated littoral habitat and/or the increased availability of prey during winter drawdown can cause increased daily movement of largemouth bass (Rogers and Bergersen 1995), which are normally quiescent during the winter (Shuter et al 2012). In contrast, reduced winter water levels show negligible effects on movement behavior in Esox lucius (northern pike), an active winter species (Rogers and Bergersen 1995).…”