Size matters: predation of fish eggs and larvae by native and invasive amphipods

What is it about?

Alien species are big problem in the modern world. These are animals and plants that have been moved by humans to parts of the world where they don't naturally belong. It is important that we understand the impacts these alien species are having: how might natural systems change when alien species are introduced? This paper provides evidence of the impact of alien killer shrimp relative to the native freshwater shrimp in Great Britain, using laboratory feeding experiments. We looked at impacts on fish eggs and larvae, because fish are an important ecological and economic resource. We found that the 'killer shrimp' is likely to have a greater impact than native British shrimp on coarse fish, through predation of eggs and larvae. However, this is driven mostly by differences in body size (killer shrimp are larger, and therefore eat more) rather than any intrinsic difference between the species. We also found that shrimp, even the alien, pose little threat to salmonids - probably because their eggs and larvae are too large and develop in cold water.

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Why is it important?

Prior to this work, predation of fish eggs and larvae by killer shrimp was speculated about, but without much hard evidence. In particular, we had no information on predation of coarse fish eggs and impacts relative to native shrimp. This paper adds to our understanding of how invasions by killer shrimp might change aquatic communities, and informs decisions about which alien species to manage.