PARENT SESSION
Contributed Oral Session 25: Aquatic Trophic Systems II
Monday, August 8, 1:30 PM - 5:00 PM, Meeting Room 518 A, Level 5, Palais des congrès de Montréal
Ecological implications of life history differences in alewives, Alosa pseudoharengus.
Post, David *,1, Palkovacs, Eric1, Dodson, Stanley2, Skelly, David1, 3, Winkworth, Cynthia1, 1 Department of Ecology and Evolutionary Biology, New Haven, CT, USA2 Department of Zoology, Madison, WI, USA3 School of Forestry and Environmental Studies, New Haven, CT, USA
ABSTRACT- Landlocked alewives, Alosa pseudoharengus, are consummate size-selective predators that provide the archetypal example for the importance of fish predation in structuring zooplankton communities made famous by Brooks and Dodson (1965). The effects of landlocked alewives on food web structure are well documented in lakes throughout eastern North America, including the Laurentian Great Lakes. In contrast to the large literature on the effects of landlocked alewives, much less is known about the ecological role of anadromous alewives, including their role in regulating food web structure and water quality in inland lakes and ponds. Anadromous alewives were historically widespread along the Atlantic coast from the Carolinas to Labrador, but declined due to overharvesting and the loss of access to inland waters where they breed. The life history differences between anadromous and landlocked alewives are considerable, with striking differences in size and age of maturation, and some preliminary evidence exists for differences in gape and gillraker spacing. Restoration efforts throughout New England aimed at removing dams or adding fish ladders to existing dams will once again allow anadromous alewives to access lakes and ponds that have been isolated from the ocean for a century or more. This is an experiment of unprecedented scope and scale, with implications for ecological processes ranging from species conservation to water quality management. Here we report the results of mesocosm experiments designed to test for differences in food web impacts of landlocked and anadromous alewives in their first summer of life. At very high densities, we find little difference in the effects of landlocked and anadromous alewives on zooplankton community composition mean zooplankton size, and algal biomass. At lower densities, the effects are more pronounced. We also resampled the landlocked alewife lakes originally studied by Brooks and Dodson (1965), and sampled for the first time lakes containing only anadromous alewives, to provide evidence for food web effects that might emerge from differences in the phonology and life history of anadromous and landlocked alewives.
Key words: alewife, life history, food web, anadromous