Assessment of Lake Ontario Alewife reproduction

Session: Exploring Predator-Prey Dynamics and Feeding Ecology in the Great Lakes (2)

Thomas Bianchi, The College at Brockport, [email protected]
Jacques Rinchard, The College at Brockport, State University of New York, [email protected]
Matthew Futia, The University of Vermont, [email protected]
Michael Connerton, SUNY ESF, [email protected]
Brian Weidel, U.S. Geological Survey, Great Lakes Science Center, [email protected]

Abstract

Since their introduction in Lake Ontario, Alewife (Alosa pseudoharengus) have dominated the forage fish community, making them the primary food source for the lake’s salmonines. Therefore, population dynamics of Alewife directly impact the success of these economically valuable predatory fish. Recently observed variability in Alewife year class strength has identified a need to understand the maturation and reproductive dynamics of Alewife. The objective of this study was to document the maturation and reproductive dynamics of Alewife based on age using gonadosomatic index (GSI) analysis and histomorphometic changes (distribution of oocyte size and relative proportion of the various oocyte stages). Changes in GSI of age 2 female Alewife (106-145 mm) were similar to those observed in older alewife (146+ mm). Average GSI remained low (<3.5%) until June, then peaked in July prior to a sharp drop in August. In July, GSI of age 2 Alewife averaged 7.3 ± 2.3% and were like those observed in older Alewife (7.4 ± 2.6%). In addition, ovaries of fish age 2 and older collected in July contained oocytes at different stages of maturity. These data confirm that Alewife are multiple-spawner fish and that age 2 Alewife have the potential to contribute to the spawning stock.