Abstract
Animals that do not provide parental care have to secure the survival of their offspring by ensuring a safe reproductive environment or smart timing tactics. Nocturnal spawning behaviour of many fish species is an example of the latter behaviour in the animal kingdom and is hypothesized to provide a survival advantage to the eggs spawned during the night. In order to test the efficiency of the smart timing tactics in a freshwater fish, a study was carried out of the interaction of the rheophilic spawner (asp Leuciscus aspius) and the predator of its drifting eggs (bleak Alburnus alburnus) using passive telemetry. According to a model based on acquired data, asp laid 63% of its eggs at night, while vision-oriented bleak was present in 92% of the time during the day. This study gives support to the predator avoidance hypothesis, which expects animals to reproduce in a period when the probability of offspring predation is at its lowest.
Highlights
The threat of predation is a driving force in many behavioural decisions in the animal kingdom
The aim of this study was to discriminate between the above-mentioned three hypotheses that might be exhibited by fish to reduce mortality of the eggs spawned. This phenomenon was studied in two sympatric freshwater fish species, namely, asp Leuciscus aspius and bleak Alburnus alburnus[17]
The number of eggs was significantly dependent on the period of the day (63.07% ± 23.06 at night), day of the year, temperature and their presence in any given day was correlated with bleak presence (Table 1, Fig. 2)
Summary
The threat of predation is a driving force in many behavioural decisions in the animal kingdom. In the case of fish, only one quarter of fish families have evolved some sort of parental care, while no species from remaining families protect their eggs In the latter case, fish are hypothesized to use three different strategies to reduce egg mortality[9]. Bleak forage on prey such as zooplankton, water insects and drifting fish eggs in the asp spawning season, and do not utilize benthic food sources including eggs attached to the substrate[18,22,23,24] Both species are visually-oriented daytime active species during the summer season with little or no nocturnal activity[24,25,26]
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