Size‐Dependent Consequences of Exogenous Cortisol Manipulation on Overwinter Survival and Condition of Largemouth Bass

Abstract

Little is known about the size-dependent consequences of stressors on wild animals, which is particularly relevant during winter where size-specific trends in survival are common. Here, exogenous cortisol manipulation was used to investigate the effect of a physiological challenge on overwinter mortality and spring condition of largemouth bass (Micropterus salmoides) across a range of body sizes. Fish were wild-caught in the fall, assigned into either control or cortisol manipulated treatments, and held in replicated experimental ponds. For bass that survived the winter, length, mass, and health metrics (e.g., gonadosomatic index [GSI], hepatosomatic index [HSI], and water content) were determined in the spring. Winter survival was marginally lower for cortisol treated bass; however, there was no influence of initial length, mass, or condition on overwinter survival. When bass were grouped by size, survival was significantly higher for bass 300-350 mm in length compared to those <200 mm. The treatment did not strongly influence spring health metrics, suggesting that largemouth bass that survived the winter were able to recover from the effects of the cortisol elevation. Initial size and sex were linked to some spring health metrics, with large females having the highest GSI and HSI scores. Overall, results from this study do not support the notion that there are size-dependent responses to cortisol manipulation

The Postrelease Survival of Walleyes Following Ice‐Angling on Lake Nipissing, Ontario

“…; Midwood et al. ). Unlike summer fisheries for the Walleye Sander vitreus , ice‐angled Walleyes are exposed to additional stressors, including freezing air temperatures upon removal from the water and more severe barotrauma resulting from short fight times and rapid ascension.…”

Space use and residency patterns of largemouth bass relative to a freshwater protected area

“…More speci cally, a larger body size enables a higher storage capacity for endogenous energy reserves (i.e., lipids; Cargnelli and Gross 1997) coupled with a lower size-speci c metabolic rate (Norin and Clark 2015). This would enable larger sh to exit the overwintering period in better condition and make seasonal movements into the shallow littoral FPA habitat sooner relative to smaller individuals (Hanson et al 2008;Midwood et al 2017). Furthermore, the residency-body size relationship may also be related to the reproductive life-history of largemouth bass.…”