Experiment on the functional response of Hemigrapsus takanoi towards a native and non-native gammarid species

We conducted two experiments to assess the predation of female H. takanoi (a non-native species in the Baltic) on a native gammarid (Gammarus duebeni) and a non-native analogous gammarid (Gammarus tigrinus). In the first experiment, we examined the functional response of female H. takanoi to G. duebeni and G. tigrinus. The experiments were conducted at the GEOMAR Helmholtz Centre for Ocean Research Kiel. Crabs were sampled in the innermost part of the Kiel Fjord, Germany (59°19'44N, 10°08'55.5E) during the summer of 2021. The experimental design utilized a fully factorial approach. One temperature (16°C) and one salinity (10) across five prey densities (1, 2, 4, 8, 16) were used. Each combination was replicated three times, alongside three replicates of predator-free controls at each prey density to quantify background prey mortality. The crabs were starved for 48 hours ahead of the experiment and were exposed to the respective number of gammarids for a 6-hour feeding period. The number of gammarids consumed was recorded.