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6/05/2017 | 3:00 PM - 3:15 PM | LARVAL FISH IN A TIME OF UNCERTAINTY: DENSITIES AND GROWTH RATES ACROSS LAKE MICHIGAN | 306C

LARVAL FISH IN A TIME OF UNCERTAINTY: DENSITIES AND GROWTH RATES ACROSS LAKE MICHIGAN

Changing ecosystem dynamics in Lake Michigan due to quagga and zebra mussel invasion have contributed to declines in nutrient availability, reduced primary production, and altered zooplankton community composition. Long-term declines in forage fish densities may be a result of reductions in growth and survival of larval fishes from this altered food web. We hypothesize that locations closer to tributaries with high phosphorus loads will have higher larval fish densities and faster growth rates, owing to greater prey resources. In July 2015, we sampled larval fish at nine nearshore-to-offshore transects throughout Lake Michigan near tributaries with a range of phosphorous loads. We collected larval fish using surface/oblique tows and extracted otoliths from a subset of alewife and bloater to determine age and estimate growth rate. Larval alewife growth rates were significantly slower than ten years ago. Results also indicate highest densities and fastest growth rates of larval alewife were found at the St. Joseph transect, which is adjacent to the highest phosphorous-loading tributary in southern Lake Michigan. This has geographic implications for prey fish survival, which can inform predator stocking strategies.

C25 Food Webs
C15 Population Ecology
C02 Fish and Other Aquatic Vertebrates

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Presenters/Authors

Drew Eppehimer (), University of Arizona, deppehimer@gmail.com;