Spatial and Temporal Patterns and the Influence of Abiotic Factors on Larval Fish Catches in the Lower Niobrara River, Nebraska

摘要

The Niobrara River has a natural hydrograph and temperature regime with the lower 32 km protected under the National Wild and Scenic River system managed by the National Park Service. The largest threat to this river is decreased instream flows due to water withdrawals for agriculture. The Niobrara River a large tributary to the Missouri River may positively influence fish production. However, no information exists regarding phenology of fish spawning or what abiotic factors may influence spawning. Our objectives were to examine the taxonomic composition and the spatial and temporal patterns of the larval fish assemblage in relation to environmental variables in the lower Niobrara River. Larval fish sampling occurred weekly from April to August in 2008 and May to August 2009 with drift nets set in the Niobrara River at two sites: the mouth and 63 kilometers upstream. Each year, larval fish first appeared in the drift during the second week of May and were collected until the third week of August. Larval river carpsuckers Carpiodes carpio were the most abundant species in the drift during early-June, followed by red shiners Notropis lutrensis and sand shiners Notropis stramineus in late-June to mid-August, with Lepomis spp. appearing during late-June to late-July.