Otolith chemistry as a fisheries management tool after flooding: The case of Missouri River gizzard shad

摘要

Reduced river-floodplain connectivity can decrease fisheries production and cause ecological and socioeconomic consequences. In 2011, the largest flood on record in the Missouri River since 1898 nearly eliminated connectivity between an embayment (Hipple Lake) and Lake Sharpe, impeding movement of walleye (Sander vitreus) and a forage fish, gizzard shad (Dorosoma cepedianum). Thus, we used otolith chemistry to quantify Hipple Lake's natal contribution to Lake Sharpe's gizzard shad population and forecast effects of connectivity loss on the reservoir's socioeconomically important walleye fishery. Fish were classified to natal habitats with 79-89% accuracy, with most gizzard shad (64%) hatching in floodplain habitats (i.e., embayments, tributaries, canals, and stilling basins). Hipple Lake contributed 12% of gizzard shad to Lake Sharpe, more than a tributary (4%) and embayment (0%) but less than a canal (27%) and stilling basin (21%). Hipple Lake (178acres) covers 0.31% of Lake Sharpe (56,884acres), so its natal contribution is 38 times what would be expected if contribution was linearly related to area. Sediment and water management to maintain connectivity between Lake Sharpe and Hipple Lake and other floodplain habitats is important for continued gizzard shad production and prey supply for the walleye fishery. Otolith chemistry facilitates assessment of gizzard shad natal contributions in different habitats, serving as a fisheries management tool to inform floodplain habitat protection and rehabilitation after floods.