engleski

Interactions between two invasive crayfish species, the signal crayfish (Pacifastacus leniusculus) and the spiny cheek crayfish (Orconectes limosus) : outdoor experiment and laboratory study

Crayfish are key ecosystem engineers and important components of freshwater food webs, both in terms of biomass and ecosystem functioning, due to their large body size, long life span, omnivorous feeding habit, and aggressiveness. Individual effects of non-indigenous crayfish species on native crayfish fauna are well documented as well as their impacts on lower trophic levels through both experimental studies and field observations. However, very few studies have examined the effects of interactions between established non-indigenous species. The aim of this work was to examine interactions between two non-indigenous crayfish species, the signal crayfish (Pacifastacus leniusculus) and the spiny cheek crayfish (Orconectes limosus). Both species are present in Croatia and The Netherlands. While in Croatia they are present in the same river system, in The Nethalands they are present in separated waterbodies but are destined to encounters in the near future. Our main question is: ”Which species will become dominant in contact zones, and therefore has a larger potential to dominate invaded freshwater ecosystems in future”. Interactions were examined using an outdoor and laboratory experiments. In October 2009, the outdoor experiment was conducted in tanks with monospecific (control) and mixed species populations at densities of 6 crayfish m-1. Experiments lasted one month, and survival and injuries in mixed species populations were assessed and compared to the controls. The laboratory experiments included behavioral observations of aggressiveness between individual specimens of the two species under controlled conditions. In the outdoor experiment the highest rate of injuries was recorded in the monospecific P. leniusculus populations, followed by the mixed species populations. In the mixed species populations all injuries were of lower intensity (antenna clipping) and were exhibited only on O. limosus. Laboratrory experiments have shown a clear dominance of P. leniusculus over O. limosus during aggressive interactions. Both experiments demonstrated that the signal crayfish has a potential to outcompete the spiny cheek crayfish, and could therefore become a dominant non-indigenous crayfish species in waterbodies of both Croatia and one of the most dominant NICS in the Netherlands.

interaction; non-indigenous crayfish species

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