Male smallmouth bass (Micropterus dolomieu) and largemouth bass (Micropterus salmoides) care for their offspring from fertilization until the offspring disperse after becoming capable of avoiding predators. We used activity transmitters to monitor round-the-clock parental activity of both species throughout the nesting period, coupled with direct observational data collected while snorkeling, to determine whether nocturnal behaviour varied similarly to diurnal behaviour. In general, nesting males of both species were equally active during day and night, developmental-stage-specific patterns being evident during both periods. Consistent with theory, parental males of both species exhibited elevated levels of burst swimming (indicative of chasing nest predators) early in the nesting period. Unlike male smallmouth bass, however, male largemouth bass showed no decline in overall activity and energy expenditure in the later nesting stages as predicted from the greater mobility and dispersion of their broods, although burst-swimming activity decreased. Activity of nesting fish was approximately double that of non-nesting conspecifics, causing an increase in respiration rates of fish, estimated using a bioenergetics model. The results of our study suggest that physiological telemetry devices which provide both behavioural and energetic information enhance the study of parental care activity in centrarchid fishes, and may be equally useful in a variety of other taxa.
Snorkelling used to examine nests and activity transmitters for monitoring parental movement