engleski

Interactions between two invasive crayfish species - potential implcations for management activities

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 (NICS) on native crayfish fauna and their impacts on lower trophic levels have been well documented by both experimental studies and field observations. However, few studies have examined how newly established NICS affect each other and how such interactions will determine their joint effect on the environment. As many European countries suffer invasions by multiple NICS, our understanding of their interplay in invaded ecosystem and their combined impact on an ecosystem is of crucial importance for prioritization of management efforts. To evaluate such interspecific competition, we investigated interactions between two NICS, the signal crayfish (Pacifastacus leniusculus) and the spiny cheek crayfish (Orconectes limosus). In many European water bodies, both species either co-occur already or will come into contact in near future. Understanding which of these species will become a dominant NICS in those contact zones, and will therefore have a larger potential for long-term impact on invaded freshwater ecosystems, is essential for development of action plans aimed at their control. To this end, we investigated the interactions of these NICS in both pairwise and group-scale settings. Agonistic interactions between pairs of conspecifics were compared to the characteristics and relative success in heterospecific dyads to test the ability of one species to dominate the other either outright or in a direct competition over a shelter resource. In both contexts, P. leniusculus was able to dominate O. limosus, being more likely to win heterospecific agonistic encounters and to acquire shelters at a higher rate. To determine whether dyadic dominance translates to a broader social context, relative survival and injury rate in conspecific and heterospecific populations were recorded in large outdoor tanks. While the highest rate of injuries was recorded in the monospecific P. leniusculus populations, O. limosus suffered more injuries in the heterospecific groups. Aggressiveness of P. leniusculus could therefore account both for its higher relative injury rate and its pairwise domination over O. limosus. We conclude that P. leniusculus has the potential to outcompete O. limosus, and could accordingly become a dominant NICS in contact zones throughout the water bodies of Europe. The health of native ecosystems is critically affected by the outcome of such competitions between highly successful invasive species, and should therefore figure prominently in decisions concerning conservation policy and resource allocation in future management activities.

interactions; invasive crayfish species; management

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