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Simonin, P.W., L.G. Rudstam, P.J. Sullivan, D.L. Parrish, and B. Pientka. 2019. Early mortality and freshwater forage fish recruitment: nonnative alewife and native rainbow smelt interactions in Lake Champlain. Canadian Journal of Fisheries and Aquatic Sciences 76(5): 806-814. doi: 10.1139/cjfas-2017-0571.
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July 2018
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Simonin, P.W., L.G. Rudstam, D.L. Parrish, B. Pientka, and P.J. Sullivan. 2018. Piscivore diet shifts and trophic level change after Alewife establishment in Lake Champlain. Transactions of the American Fisheries Society 147: 937-947. doi: 10.1002/tafs.10080.
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Abstract
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May 2018
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Invasions and deliberate introductions of new prey species are likely to affect prey choice and trophic level of resident predators. Rainbow Smelt (Osmerus mordax) and Alewife (Alosa pseudoharengus) are common prey fish species in lakes throughout North America either as native or non-native species. The establishment of Alewife in the 2000s in a lake with a native Rainbow Smelt population (Lake Champlain) presented an opportunity to study changes in the diet and trophic level of fish already established in the system. Using stable isotope analysis, we found that Alewife became a major component of predator diets, in particular of the diets of Atlantic Salmon (Salmo salar) and Walleye (Sander vitreus). Lake Trout (Salvelinus namaycush) consumed relatively few Alewives. For Walleye (the predator with both pre- and post-Alewife isotope ratios available), the δ15N values decreased significantly from the pre-Alewife period of the late 1990s, indicating that Walleye feed at lower trophic levels when Alewife are present. Predation on Alewife was correlated with the amount of spatial overlap of predators and prey. Our results show that the introduction of Alewife has altered the predator-prey linkages in Lake Champlain; alterations that can have major effects on food web structure and trophic cascades.
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Simonin, P.W., D.L. Parrish, L.G. Rudstam, P.J. Sullivan, B. Pientka. 2012. Native rainbow smelt and nonnative alewife distribution related to temperature and light gradients in Lake Champlain. Journal of Great Lakes Research 38 (Supplement 1): 115-122.
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March 2012
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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
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Abstract
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April 2016
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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.
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Rudstam, L. G., S. L. Parker, Einhouse, D. W., L. D. Witzel, D. M. Warner, J. L. Stritzel, D. L. Parrish, P. J. Sullivan. 2003. Application of in situ target strength estimations in lakes--examples from rainbow smelt surveys in Lakes Erie and Champlain. ICES Journal of Marine Science 60: 500-507.
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June 2003
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Hyrcik, A.E., P.W. Simonin, L.G. Rudstam, D.L. Parrish, B. Pientka, and T.B. Michuc. 2015. Mysis zooplanktivory in Lake Champlain: a bioenergetics analysis. Journal of Great Lakes Research 41: 492-501. doi:10.1016/j.jglr.2015.03.011
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Abstract
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Publisher Website
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April 2015
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Mysid shrimp are important as both predators on zooplankton and as prey for a variety of fish species across most of the Laurentian Great Lakes. In Lake Champlain, where little is known about mysids, this may also be true. We evaluated the role of Mysis diluviana as a planktivore in Lake Champlain using hydroacoustics, gut content analysis, stable isotopes, cohort analysis, and bioenergetics models to estimate Mysis density, diets, growth rates, and prey consumption rates. Density of Mysis in the water column of the deeper Main Lake was lower in July-August of 2008-2011 (38, 38, 21, and 74 Mysis /m2, respectively) than historical values from the 1970s. Mysis selectively foraged for cladocerans, but also consumed cyclopoid and calanoid copepods in 2011. Stable isotope data suggest a mostly carnivorous diet, although agreement between isotope mixing models and observed diets varied. Cohort analyses revealed growth rates ranging from 2.7 mm/month in late spring to 1.3 mm/month in late summer. In contrast to the offshore areas of Lake Ontario and Lake Huron, zooplankton consumption by the Mysis population was low relative to zooplankton density and production indicating that Mysis are not currently a major zooplanktivore in Lake Champlain.
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