Cooperative Fish and Wildlife Research Units Program: Vermont
Education, Research and Technical Assistance for Managing Our Natural Resources

Simonin, P.W., D. L. Parrish, L. G. Rudstam, P. J. Sullivan, and B. Pientka. 2016. Interactions between hatch dates, growth rates, and mortality of age-0 native Rainbow Smelt and nonnative Alewife in Lake Champlain. Transactions of the American Fisheries Society 145: 649-656. doi: 10.1080/00028487.2016.1143401


Timing of hatch in fish populations can be critical for first-year survival and, therefore, year-class strength and subsequent species interactions. We compared hatch timing, growth rates and subsequent mortality of age-0 Rainbow Smelt Osmerus mordax and Alewife Alosa pseudoharengus, two common open-water fish of northern North America. In our study site, Lake Champlain, Rainbow Smelt hatched almost a month earlier than Alewife (hatching began on 26 May for Rainbow Smelt and 20 June for Alewife). Abundance in the sampling area was highest in July for age-0 Rainbow Smelt and August for age-0 Alewife. Later-hatching individuals of both species grew faster than those hatching earlier (0.6 mm/d vs. 0.4 for Rainbow Smelt; 0.7 mm/d vs. 0.6 for Alewife). Mean mortality rate for age-0 Rainbow Smelt was 3.4%/d and for age-0 Alewife was 5.5%/d during the first 45 days of life. Alewife mortality rates did not differ with hatch timing but daily mortality rates of Rainbow Smelt were highest for earlier-hatching fish. Cannibalism is likely the primary mortality source for age-0 Rainbow Smelt in this lake. Therefore, hatching earlier may not be advantageous as the overlap of adult and age-0 Rainbow Smelt is highest earlier in the season. However, Alewife, first documented in Lake Champlain in 2003, may increase the mortality of age-0 Rainbow Smelt in the summer, which should favor selection for earlier hatching.