Feeding patterns of the black-striped pipefish Syngnathus abaster in an invaded freshwater habitat.
Syngnathus abaster is an euryhaline species, which has penetrated freshwaters in Europe and its range is expanding. The goal was to investigate the feeding patterns of this species in an invaded freshwater habitat, where it first appeared at the beginning of 1990s, with implications for assessing its possible effects on invaded ecosystems. In total, 36 prey items were identified in the diet of S. abaster. The most important prey were zooplanktonic organisms, among which copepods predominated significantly. The second most important prey were cladocerans, represented by 20 species/genera. The diet composition of this species showed clear seasonal dynamics but copepods remained the predominant prey item throughout the year. Significant positive relationships between the abundance of zooplanktonic organisms in the gut contents of S. abaster and their abundance in zooplankton samples were found for copepods and Ceriodaphnia sp. S. abaster showed a significant positive electivity for copepods throughout all months. It also positively selected some large cladocerans, which probably shared the same habitat. S. abaster also consumed fish items including gobiid larvae and its own juveniles, when they were abundant in May and especially in June. The possible effect of S. abaster on native ecosystems may include the shaping of zooplanktonic communities through selective predation on copepods. This species is unlikely to be a serious food competitor for native fish inhabiting European freshwaters, the majority of which are cyprinids. Nevertheless, it can have effects on some native fish through predation on their juveniles, which might share the same habitats.