River discharge drives survival of larval walleye

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survival, walleye, Recruitment, food, spawning, production, Otolith, larvae, migration, sediment, mortality, wildlife, juvenile, watershed

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Ecological Applications


Walleye (Stizostedion vitreum) in Lake Erie have historically experienced largefluctuations in recruitment success, which have important implications for walleye populationdynamics as well as food web interactions. Because walleye year class strength in Lake Erielikely is set during the larval life stage, we explored factors underlying larval survival during outmigrationin the Maumee and Sandusky rivers, Ohio's primary walleye spawning tributaries. Toevaluate our expectation that survival of larval walleye would be positively related to discharge,we estimated daily larval production and used otoliths to estimate hatch dates of larvae survivingout migration. Comparing daily larval production and survival distributions demonstrated strongtemporal patterns of larval survival that were unrelated to daily larval production patterns. Dailysurvival varied greatly during the larval hatch (~4 wk), with short, discrete periods (4-7 d) of highsurvival accounting for 75-84% of total survivors. Contrary to our original expectations, larvalsurvival was inversely related to river discharge (P < 0.05). As river discharge increased, theamount of suspended sediments increased (r 2> 0.6, P < 0.001), likely directly increasing larvalmortality. Post-out-migration densities of larval walleye in Maumee and Sandusky bays werecorrelated strongly (Maumee Bay: r 2= 0.99, Sandusky Bay: r 2= 0.94) with Ohio Division ofWildlife estimates of late summer juvenile abundance of Lake Erie walleye (which historicallyhave been correlated strongly with year class strength). Because high discharge events duringthe larval hatch likely reduce survival, variability in river discharge underlies variability of walleyeyear class strength. Managers could mitigate these effects by reducing exploitation of spawningwalleye and improving watershed characteristics to reduce discharge fluctuations and suspended sediments. http://dx.doi.org/10.1890/1051-0761(1998)008[0088:RDDSOL]2.0.CO;2







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