Effects of Acute Temperature Change Associated with Handling Practices on Metabolic Rate Stabilization in Two Centrarchids

Abstract

AbstractSportfishing and hatchery practices routinely subject fish to acute temperature changes through placement of fish in live wells and normal handling and transportation procedures. Acute temperature changes alter metabolic rate in ectotherms; however, the rapidity of the response to reach a new homeostatic state is not well known. Therefore, the response duration in metabolic rate after acute temperature change was measured in two centrarchid species, the Largemouth Bass Micropterus salmoides and Redear Sunfish Lepomis microlophus, which are representative of two different body shapes and are both commonly pursued in recreational fishing and reared in hatcheries. Largemouth Bass were acclimated to either 20°C or 30°C, and Redear Sunfish were acclimated to 24°C. Aerobic metabolic rate was measured immediately after acute temperature change (−4, +0, or +4°C) and was measured repeatedly in cycles of 5.5 or 10.0 min, respectively, until the metabolic rate stabilized. In Largemouth Bass, the metabolic rate stabilized similarly or more slowly following a moderate high‐temperature shock (+4°C; 44 min) compared to transfer to conditions with no temperature change (+0°C) or a moderate low‐temperature shock (−4°C; 16–48 min). In contrast, the metabolic rate in Redear Sunfish stabilized faster after transfer to +4°C (15 min) than after transfer to −4°C or +0°C (both 31 min), possibly because the elevated metabolic rate after transfer was sustained. Notably, for both species, metabolic rates stabilized at a generally lower level after transfer to −4°C than after transfer to +0°C or +4°C. Therefore, the duration until stabilization of metabolic rate after acute temperature change may depend upon species and acclimation temperature, although for both species examined, the energy savings in reduced metabolic rates after moderate cold shock may be beneficial for recovery from sportfishing or hatchery practices.