Diet analysis indicates seasonal fluctuation in trophic overlap and separation between a native and an introduced shrimp species (Decapoda, Palaemonidae) in the tidal river Thames (U.K.)

Abstract

The diets of Palaemon longirostris and the non-native P. macrodactylus were investigated to explore their competitive interactions. Both species are largely carnivorous with amphipods being the dominant prey. Chironomid larvae were consumed in large numbers by both species in summer. Vacuity coefficients were higher for both species in winter than summer. A high degree of dietary overlap occurs in winter, with less overlap in summer suggesting that the two species compete for food on a seasonal basis, which may be partly attributed to the absence of chironomid larvae, and generally reduced prey availability, in the winter. If summer prey also become limited then competition for food may increase and P. macrodactylus may then have an adverse effect on P. longirostris. An introduction of P. macrodactylus in the summer, when there is less competition for food, may be more likely to lead to a successful colonisation than one in the winter.