Coping with the cold: energy storage strategies for surviving winter in freshwater fish

Abstract

For many ectothermic animals, the acquisition, storage and depletion of lipids is integral to successfully coping with reduced metabolic rates and activity levels associated with cold, winter periods. In fish, lipids are crucial for overwinter survival and successful reproduction. The timing and magnitude of seasonal lipid storage should therefore vary predictably among fish with different thermal preferences and spawn times. Small-and large-bodied fish should also face different constraints associated with season that influence lipid cycling. However, much work to date has been species-and location-specific and a general conceptual model for the seasonal energy budgets of freshwater fish is lacking. Here, we conducted a comprehensive literature review of seasonal lipid levels in freshwater fishes. We predicted that warm and cool water species would be more likely to demonstrate peak lipid levels during warm months than cold water species, and expected a larger magnitude of annual lipid cycling in warm and cool water compared to cold water fish. We also expected dampened lipid cycling in larger fish due to their lower mass-specific metabolic rates. Observed patterns in the timing and magnitude of lipid storage contradicted our prediction because lipid cycling was widespread across species, despite thermal guild, with peak lipid levels commonly occurring during warmer months, even in cold water fish. For body size effects, larger bodied fish species had dampened seasonal lipid cycling, as predicted. We developed a conceptual framework describing how the 'scope' for variation in annual lipid cycling changes with body size both among and within species in order to guide future work. Together, our findings suggest that energy acquired during warm months is broadly important for overwinter survival and reproduction in fishes, and provide a new perspective on the differential constraints and physiological responses to seasonality among freshwater fish. Improving our understanding of these dynamics is especially pressing given that a changing global climate is anticipated to alter existing seasonal signals.

Physiological mechanisms linking cold acclimation and the poleward distribution limit of a range-extending marine fish

“…Cold exposure is likely to affect fitness based on length of time at dormancy-promoting temperature versus those that favour increased energy throughput. Recent work on freshwater fishes demonstrates energy acquisition during warm months is critical for fitness and overwinter survival ( Fernandes and McMeans, 2019 ).…”

Species-specific preferences drive the differential effects of lake factors on fish production

“…Therefore, angling activity may not reflect which species were actually targeted on a given lake, and any effect on species-specific production could have been missed by the BRT analyses (Embke et al 2019). Our study also lacked winter data (e.g., lake water chemistry data are only sampled in the summer, time of ice on or off), so we might be missing over-wintering or other seasonal processes that could affect winter energy storage, spawning, young-of-year (age-0) fish survival, or fish body condition (body mass) during the sampling year (Fernandes and McMeans 2019). Therefore, measures such as degree days may not account for warm winter temperatures that are still below 5°C but are unfavourable for gonadal development and successful reproduction the following year.…”

The effect of seasonality on yellow perch ecology and ecotoxicology within Lake Manganese

“…Yellow perch lipid contents demonstrated a significant seasonal pattern with highest lipid levels occurring in the winter and prior to spring reproduction. This pattern agrees well with that described for yellow perch and other cool and cold-water fish species that spawn in the spring [16]. Due to the high caloric content of lipid tissues, it would be expected that energy density would follow a similar seasonal pattern as lipid content.…”

“…Stunting in fish populations is indicated by earlier sexual maturation, smaller sizes at age, longer lifespans, and exceedingly slow growth rates relative to those described for typical population [20-23, 27, 28]. This phenomenon can be attributed to a variety of factors including competition for limited food resources [21,23,28] [16]. The slow growth rates within Lake Manganese which, when combined with longer-lived individuals, could further increase resource limitation and also contribute to stunting in this yellow perch population.…”

“…Individuals then transition to a benthic diet within the littoral zone until they are large enough to make their final ontogenetic shift to include piscivory [13][14][15]. In order to compensate for reduced food availability during the winter, yellow perch tend to rely on lipid stores build up during the summer as an energy reserve [16]. During winter, yellow perch diets also shift to include larger proportions of benthic invertebrates and zooplankton relative to their summer diet [17,18].…”