Ecology and Management of Pallid Sturgeon and Sturgeon Chub in the Lower Platte River, Nebrasks

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OBJECTIVE 2: APPROACH: We are using the occurrence of fish eggs and larvae drifting in the Platte River to accomplish this objective. Larval fish are being sampled at four sites in the lower Platte River (near Two Rivers SRA, Ashland, Louisville, and Plattsmouth) to describe the spatial distribution and chronology of reproduction and hatching of all species in the lower Platte River. Sampling commences in May and continues into August of each year to encompass the potential time when sturgeon and sturgeon chub reproduction occurs. Larval fish are being sampled using standard 0.6 mm mesh drift nets. Each net is equipped with a current meter which enables us to determine the water volume sampled. A sample at a site consists of four net sets for up to 15 minutes each. Time of sampling begins at either midnight (0000 hours); 0300 hours; 0600hours; 0900 hours; noon (1200 hours); 1500 hours; 1800 hours; or 2100 hours. Times of regular sampling are chosen at random and each site is sampled once per month starting with the first week in May and continuing until the end of August. In addition, the site near Ashland is being sampled every three hours for a 24 -hour period on weeks alternating with the regular sampling to determine diel periodicity of larval drift. In addition, samples from the Missouri River, upstream and downstream from the mouth of the Platte are being collected by Nebraska Game and Parks Commission personnel. These samples are analyzed by Platte River project staff, using support provided by Nebraska Game and Parks Commission, to document the relative contributions of the Platte River and Missouri River to sturgeon recruitment downstream. Our initial objective is to determine the spawning time for sturgeon and sturgeon chub in the Platte River. Samples are preserved in 10% formalin in the field and transported to the lab for analysis. In the laboratory, 11