Kotterba, Paul (2015) Estuarine stickleback predation on the eggs of inshore-spawning Atlantic herring in the Baltic Sea. [Talk] In: 23. Biennial CERF Conference. , 08.-12.11.2015, Portland, Oregon, USA .

Abstract

Alike Pacific herring, important subpopulations of their counterparts in the Atlantic Ocean and adjacent waters migrate into coastal areas and estuaries for spawning. Particularly spring-spawning herring in the Baltic Sea preferably attaches its adhesive eggs on submerged aquatic vegetation in shallow inshore systems thus committing the offspring's fate to a unique set of local drivers and stressors. Within these systems, egg predation is considered to be an important factor structuring the reproduction success, but studies quantifying the actual effect of the resident predator community are still rare. Due to the lack of any significant tidal amplitudes in the Baltic Sea inshore waters, this community is rather represented by fish and diving water fowl than by sea gulls and other non-diving egg predators known to be important in other regions such as the Pacific coastline. Assuming piscine predation to be most important, we examined the effects of the resident small fish community on herring egg survival in an important spawning area in the Baltic Sea. Considering fluctuating predator abundances, egg concentrations and water temperatures, predator exclusion experiments with naturally and artificially-spawned substrates concordantly showed egg predation rates of about 40%. Continuous sampling during the experimental period showed that the local fish community was dominated by threespine sticklebacks. We combined laboratory feeding experiments with field investigations on stickleback abundances, their stomach contents and herring spawn occurrence to extrapolate the predation effect of this particular species. Results indicate a significant predation effect particularly on those spawning peaks which are considered to be essential for the annual herring reproduction. Our results demonstrate an important link between ocean-going herring and a resident estuarine fish community which needs to be considered in future integrated fish resource management approaches.

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