Life in the ice lane: the winter ecology of stream salmonids

Abstract

Despite the common view that conditions in winter strongly influence survival and population size of fish, the ecology of salmonids has not been as extensively studied in winter as in other seasons. In this paper, we review the latest studies on salmonid winter survival, habitat use, movement and biotic interactions as they relate to the prevailing physical and habitat conditions in rivers and streams. The majority of research conducted on the winter ecology of salmonids has been carried out in small rivers and streams, where temperatures are above zero and where there is no ice. Investigations in large rivers, regulated and dredged rivers, and under conditions of different ice formations are almost totally lacking, presumably related to sampling difficulties with these systems. The studies-at-hand indicate that a multitude of physical and biological factors affect the survival, behavior, and habitat use of salmonids in winter. The general concept that winter functions as a critical period for the survival of young salmonids is not well supported by the literature. Instead, overwinter survival of juvenile fish appears to be context-dependent, related to specific habitat characteristics and ice regimes of streams. In general, over wintering salmonids prefer sheltered, low velocity microhabitats, are mainly nocturnal, and interact relatively little with conspecifics or interspecifics. Specific descriptions of microhabitat preferences of salmonids are difficult to make due to highly disparate results from the literature. We suggest that future research should be directed towards (1) being able to predict the dynamics of freezing and ice processes at different scales, especially at the local scale, (2) studying fish behavior, habitat use and preference under partial and full ice cover, (3) evaluating the impacts of man-induced environmental modifications (e. g. flow regulation, land-use activities) on the ecology of salmonids in winter, and (4) identifying methods to model and assess winter habitat conditions for salmonids.

Winter Disturbances and Riverine Fish in Temperate and Cold Regions

“…We concentrate on natural events but consider selected anthropogenic disturbances where that is relevant for the discussion. The present study adds to five earlier reviews on the winter ecology of riverine fish (Power et al 1993, Cunjak 1996, Hurst 2007, Huusko et al 2007, Brown RS et al 2011 by placing the existing knowledge in a broader context of disturbance research.…”

“…However, this finding may be biased by the fact that mainly short-term pulses, requiring only limited periods of refuge use, have been documented in the literature. Coverrich, deep habitats, which are less susceptible to dewatering and which provide protection from predation, might be more relevant during long-lasting ramp disturbances, such as winter droughts (Huusko et al 2007). For example, cutthroat and brown trout preferred cover-rich pools in a field experiment in which discharge had been successively reduced by a total of 400% over a 3-month period from December to February (Dare et al 2002).…”

“…We list questions to be addressed by future research in box 3. Third, hydraulic and population models-crucial tools for prediction and ecosystem understanding-should increasingly incorporate winter-and disturbance-specific aspects, such as various causes of winter mortality (Hurst 2007, Huusko et al 2007 or dynamic ice formation and its effects on the residential and refugial habitats of riverine fish (Alfredsen and Tesaker 2002). Fourth, management for sustainability requires that river managers and conservationists work proactively by including anticipated future alterations in the design of restoration and conservation activities.…”

Effects of Changes in Arctic Lake and River Ice

“…Through the modifications of ice regimes, climate change will have a profound influence on the behavior and biological response of stream biota (Huusko et al 2007) and, therefore, will play a central role in their growth, survival and reproduction. Surface ice creates shelter habitats for fish in areas that are too exposed for use during open-water periods Linnansaari et al 2009).…”

“…Moreover, winter and related ice formation could act as a 'bottleneck' for survival of fish and invertebrates. Results reported by Huusko et al (2007) suggest that the variability in creating such bottlenecks among rivers is highly context dependent and controlled by the life stage of the fish, local habitat, and the related type of ice regime. Overall, the large and complex scope of potential changes in future river-ice regimes will make predictions of future biological responses difficult, particularly considering the current rather limited knowledge of high-latitude lotic systems.…”