Energy expenditures during reproduction by sockeye salmon (Oncorhynchus nerka)

Abstract

From 1994 to 1996, behaviour and energy use by sockeye salmon spawning in Gluskie Creek, British Columbia, was investigated by a combination of behavioural observation and electromyogram (EMG) telemetry. The spawning life was 7.6 days for males and 10.6 days for females. Both sexes held in pools for a few days, with an average cost of 7.9 kcal/day, before starting to spawn. During spawning, dominant males performed 6 behavioural acts per 10 min, charging being the most frequent followed by quivering, chasing, digging, lateral and posture displays. Spawning females performed 4.4 behavioural acts per 10 min, digging being the most frequent followed by charges and chases. Following egg deposition, females entered a nest guarding phase and, in the latter stages of spawning, males adopted subordinate behaviour. Guarding females and subordinate males performed 1.1 and 1.6 behaviours per 10 min respectively. Lateral and posture displays by males lasted 6.3 s and 11 s respectively but all other behaviours lasted less than 2 seconds. Holding behaviour and posture displays required the most energy in males and holding and digging in females. Dominant males and spawning females expended 23.9 kcal/day whereas guarding females and subordinate males expended 11.0 kcal/day. Frequency of behaviours during active spawning was similar to other populations. Length of spawning life was shorter, however, and total energy expended was less than estimates for other populations based on body constituent analysis. Although EMG telemetry may underestimate total energy expenditure, other recent measures of gross energy expenditure by Stuart River sockeye also indicate that energy available for reproduction was low in this population due to declining average size and low energy reserves in fish arriving at the spawning grounds.