Obtaining food following the transition from endogenous to exogenous feeding and during the first year of life is a critical event that strongly influences growth and survival of youngof-year fishes. For shovelnose sturgeon Scaphirhynchus platorynchus, limited information is available on food habits during the first year of life. The objective of this study was to quantify diet components of shovelnose sturgeon during the transition from endogenous to exogenous feeding and during the youngof-year life stage in the North Dakota and Montana portions of the Missouri River. Young-of-year shovelnose sturgeon were sampled between early August and early September 2003. Shovelnose sturgeon initiated exogenous feeding by 16 mm, and individuals 16-140 mm fed exclusively on two macroinvertebrate orders (Diptera and Ephemeroptera). Youngof-year shovelnose sturgeon exhibited an apparently high feeding success as 99 of 100 individuals contained food in the gut. The number of organisms in the gut increased exponentially with fish length for larval Diptera (r 2 ¼ 0.73, P < 0.0001) and linearly (r 2 ¼ 0.12, P ¼ 0.0006) for larval Ephemeroptera, but the number of Diptera pupae in the gut was not significantly related (P ¼ 0.55) to length of young-ofyear shovelnose sturgeon. The length of ingested prey was linearly related to fish length for Diptera larvae (r 2 ¼ 0.20, P ¼ 0.002), whereas the relationship between lengths of ingested Ephemeroptera larvae and lengths of young-of-year shovelnose sturgeon was best described by a power function (r 2 ¼ 0.50, P < 0.0001). These results provide the first quantification of feeding dynamics for young-of-year shovelnose sturgeon in a natural river environment.
Turtle populations are imperiled worldwide, but limited ecological information from unaltered systems hampers science-based management and conservation of some species, especially riverine turtles such as the spiny softshell (Apalone spinifera). We therefore investigated movements and spatial habitat selection of 54 A. spinifera in 633 river kilometres (rkm) of the least-altered river in the conterminous United States-the Yellowstone River in Montana-from 2005 to 2009. Movement rates and home ranges were smaller than in fragmented, altered river systems because nesting and overwintering habitats were common and in close proximity. Habitat selection also differed. A. spinifera in the Yellowstone River overwintered in unaltered bluff pools and summered in complex reaches with side channels, islands, and diverse habitats. However, those in the highly altered Missouri River used deep alluvial pools for overwintering and flooded, inundated, or backwatered tributary mouths in spring and summer. Importantly, selected habitats in both rivers were functionally similar, including complex river reaches (with multiple channels, islands, and diverse habitats) and natural pool types. Unfortunately, these are the very habitats that are limited in rivers affected by dams, bank stabilization, and channelization. Therefore, preservation of natural and diverse riverine habitats-and the fluvial dynamics that maintain them-may enhance conservation of A. spinifera in large rivers.
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