Invasive predators trigger long-term changes

Posted on March 26, 2010

Introduced predators can have negative  impacts on aquatic communities because prey are vulnerable to attack by unfamiliar species.   Although there have been many studies of the responses of zooplankton to introduced predators, most have been short term  before-and-after comparisons.  A Norwegian study tracked changes in the zooplankton community in LakeRuskebuktaover a relatively long period (12-years: 1991-2002) that coincided with the invasion and establishment of vendace (Coregonus albula) in the system.  Over this time, the density and diversity of zooplankton fell, and smaller species became more abundant, due to the preference of vendace for larger prey items.  Large-bodied water fleas (Daphnia species and Bosmina longispina) showed the sharpest declines, and the largest Daphnia species (D. longispina) was eliminated entirely.  Water flea species also showed a decrease in their size at first reproduction, and an increase in clutch size, seemingly in response to the presence of vendace.  These changes in body size and reproduction showed a steady, continuous progression through the whole study period, during which time some 30-40 generations of prey experienced directional selection pressure from the invading predators.

Reference:  Amundsen, P-A., Siwertsson, A., Primicerio, R. & Bohn, T.  2009.  Long-term responses of zooplankton to invasion by a planktivorous fish in a subarctic watercourse.  Freshwater Biology 54, 24–34.