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GLERL 2004 Milestone Reports
< GLERL 2004 Milestone main page
GOAL: Protect, Restore and Manage Use of Ocean and Coastal Resources Through Ecosystem Management Approaches
Scientist: Dr. Henry Vanderploeg (GLERL)
NOAA Performance Measure: Increased number of invasive species under control
OAR / ISP Performance Measure: Increase number of invasive species under control
Milestone: Finding a niche in the Great Lakes: the story of the invasion of the non-indigenous predatory cladoceran, Cercopagis pengoi. (Vanderploeg, GLERL)
Purpose: Understanding factors that allow non-indigenous species to invade new environments is important for predicting what species may invade and their subsequent impacts. Of particular interest are interactions of a new invader with an established invader. Are previously invaded systems more resistant to invasion than un-invaded systems or do previous invaders facilitate invasion? The particular case in point is the invasion dynamics and impacts of Cercopagis pengoi, which invaded the Great Lakes in 1998, as affected by a closely related and ecologically similar species, Bythotrephes longimanus, which invaded the Great Lakes in the 1980s (Fig. 1). The concern of both of these species is that they prey on the same food that small fish eat, but that small fish cannot eat them because of their long tail spines (Fig. 1). We wondered why Cercopagis is found in Great Lakes where Bythotrephes is not abundant, and is abundant in lakes where Bythotrephes is rare. Also, why was Bythotrephes found in some Great Lakes but not others?
Efforts and Results (to date): To answer these questions we did a number of studies on the prey preferences of these invaders as well as large fishes that might eat them. First, we showed that Cercopagis was a preferred prey of Bythotrephes (Fig. 1). Thus, Bythotrephes controlled Cercopagis distribution. Second, we showed that adult alewives, the dominant planktivorous fish in some Great Lakes preferred Bythotrephes but avoided Cercopagis as food. Lakes with high alewife abundance had low Bythotrephes abundance, but high Cercopagis abundance. Thus fish mediated invasion dynamics and interactions between these two invaders in the Great Lakes and explains why some Great Lakes have Bythotrephes and others Cercopagis. Future work will focus on the effects of these invaders on the food web.
Figure 1. Non-indigenous predatory (cercopagid) cladocerans, Bythotrephes longimanus (top) and Cercopagis pengoi (middle) and typical cladoceran prey, Bosmina longirostris (lower left) and Daphnia galeata mendotae (lower right), from Lake Michigan. The cercopagids are both third instar females with eggs, and the prey are females with eggs. These same prey are favored food of small fishes. Species size relative to each other is to scale.
Customer(s): Regulators and scientists working on preventing invasions of new exotic species and those evaluating their impacts.
Cause Factors (if milestone not met): N/A
Revised Completion Date (if milestone not met): N/A
Last updated: 2004-09-15 js