Laboratory studies on the effects of thermal change on the behaviour and distribution of juvenile chum salmon in sea water

✍ Scribed by I. K. Birtwell; J. S. Korstrom; A. E. Brotherston

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 251 KB
• Volume: 62
• Category: Article
• ISSN: 0022-1112
• DOI: 10.1046/j.1095-8649.2003.00008.x

✦ Synopsis

Schooling chum salmon Oncorhynchus keta were biased towards the water surface (median position <1 m) under isothermal conditions (10° C) in a water column simulator (WCS). Thermal stratification (24/10° C) inhibited upward movement with fish congregating at the thermocline and displaying a clear avoidance of potentially lethal surface waters. A tri‐phase model based on piece‐wise nonlinear regression was used to describe the distribution shifts of chum salmon during a change from isothermal to thermally stratified conditions. Fish distribution was consistent with thermoregulatory behaviour and exhibited ‘attraction’, ‘preference’ and ‘avoidance’ phases. The thermal preference of 50% of the fish lay between 12·2 and 20·2° C, however, >83·5% of the fish occupied a ‘preferred’ temperature range of 13·7–17·9° C. The mean temperature at which 50% of chum salmon avoided rising temperature by shifting deeper in the water column and using the cooler thermocline was 20·2° C, and 90% avoidance occurred at 22·9° C. Behavioural responses to thermal stratification were consistent amongst underyearling fish of differing size and age.