Mysis diluviana population and cohort dynamics in Lake Ontario before and after the establishment of Dreissena spp., Cercopagis pengoi, and Bythotrephes longimanus

• Published in: Canadian journal of fisheries and aquatic sciences Vol. 68; no. 5; pp. 795 - 811
• Main Authors: JOHANNSSON, Ora E, BOWEN, Kelly L, HOLECK, Kristen T, WALSH, Maureen G
• Format: Journal Article
• Language: English
• Published: Ottawa, ON NRC Research Press 01.05.2011; National Research Council of Canada; Canadian Science Publishing NRC Research Press
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Aquatic ecological zones; Aquatic ecosystems; Aquatic sciences; Biological and medical sciences; Biological productivity; Biomass; Bythotrephes longimanus; Cercopagis pengoi; Crustaceans; Demecology; Dreissena polymorpha; Dreissena rostriformis bugensis; Environmental changes; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Food resources; Freshwater; Fundamental and applied biological sciences. Psychology; General aspects; Lakes; Mortality; Mysis diluviana; Neogobius melanostomus; Plankton; Population decline; Predation; Reproduction; Summer; Zooplankton; Great Lakes of America; Lake Ontario; North America; America; United States; Canada, Ontario, Ontario L; Osmerus eperlanus; Productivity; Night; Egg; Abundance; Mysidacea; Biomass; Invasion; Crustacea; Freshwater environment; Vertebrata; Bivalvia; Arthropoda; Pisces; Ecosystem; Cohort study; Decay; Female; Hypolimnic zone; Population dynamics; Predator; Invertebrata; Mollusca; Zooplankton
• ISSN: 0706-652X; 1205-7533
• DOI: 10.1139/f2011-028

We investigated population responses of Mysis to ecosystem changes induced by invasion of dreissenids and predatory cladocerans, Cercopagis and Bythotrephes . Lake productivity declined as dreissenids invaded the offshore region. Whole-lake mysid biomass was compared before (early 1990s) and after (2002–2007) the invasion period; it declined 40%–45%. Abundance of young mysids and presence of a summer cohort increased with summer, epilmnetic, nighttime zooplankton biomass (i.e., food biomass index). Cercopagis + Bythotrephes biomass was negatively correlated with this index, implicating them in the mysid decline. Eggs per gravid female increased with autumn, total-water-column zooplankton biomass, reflecting the greater use of hypolimnetic waters by adults. Reproductive success was below replacement during the period 2002–2005. First-year mysid growth rate was maintained while population abundance declined, suggesting selection for individuals that feed effectively at low food concentrations. Mortality rates in the first and second years were dependent on cohort density, indicating that competition for food limited abundance in the first 2 years. Fish predation indices (smelt and alewife combined) were correlated positively with mortality rates and negatively with abundance in the third year. Thus, mysids cannot support as many fish in invaded compared with non-invaded lakes. They may also not be a stable food resource; unusual cohort losses occurred in some years.