The Effect of Predation of Threespine Stickleback (Gasterosteus aculeatus) on the Eggs of Atlantic Herring (Clupea harengus) in a Baltic Spawning Site

The predation of threespine stickleback on the spawn of Atlantic herring was investigated in a lagoon of the Baltic Sea. We hypothesized that a significant predation of the estuarine stickleback on the recruitment of herring occurs. To test this, a predator exclusion field experiment was conducted using artificial substrates. These substrates were combined with tank feeding experiments to estimate the effects of temperature and prey density on the herring egg consumption by stickleback. A predator exclusion experiment and its controls showed a significant mortality of herring eggs by predatory fish species, mainly stickleback and young perch. A strong increase in the consumption of herring eggs by sticklebacks was observed between 11 and 15°C (Q₁₀ = 3.15). In addition, a significant positive correlation between egg concentration per area and predation intensity was found. Nearly all eggs were consumed at concentrations ≥ 25 eggs cm^-2. The highest M_PS (11.4%) was in the second half of the spawning season. It is concluded that stickleback predation on herring eggs is in an order of magnitude to potentially affect the local herring year class strength.