Larval fish abundance and habitat associations in backwaters and main channel borders of the Kanawha River

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Abstract

Larval fish distributions were determined in the lower Winfield Pool, Kanawha River, West
85, Virginia, using a 0.5-m plankton net and a 1-m2 dropbox. Five habitats were sampled with the
plankton net, 3 habitats with the dropbox. The 5 deep water water habitats, greater than 1.5-m
in depth, sampled by the plankton net included surface tows in Billâ s Creek backwater, main
channel border upstream and downstream of Little Guano backwater, and Little Guano Creek
backwater, where deep tows (1.5 m deep) were also taken. The 3 shallow water habitats, less
than 1 m in depth, sampled by the dropbox included open water over silt substrate, open water over a sand substrate, and emergent vegetation. Lepomis species, emerald shiners (Notropis atherinoides), and gizzard shad (Dorosoma cepedianum) were the dominant taxa. The emerald shiner taxa could also have included some larvae of Notropis species which are also
present in the Kanawha River but whose larvae have not been described. Overall, the mean
total larval density did not differ between the backwater or the main channel borders but the
species associated with each habitat differed greatly. The Lepomis larvae were found
predominantly in backwater areas. These areas provide suitable spawning sites for many
centrarchids of this river. Upon leaving the nest, the Lepomis larvae moved into the deeper
open water areas within the backwater. After reaching the juvenile stage, these same larvae
returned to the shallow water habitats where they inhabited vegetated areas. Emerald shiner larvae, while present in both backwater and main channel habitats, were most abundant in the
main channel borders. This is probably a result of their parentâ s pelagic spawning strategy. In all habitats, emerald shiner larvae predominated in the upper 1 m of water. Upon becoming
larger, the emerald shiner larvae appeared in the backwaters. This increase in numbers
could be due to movement, differential mortality, or higher growth rates. Other cyprinids
(excluding emerald shiners and carp) were equally abundant in both backwater and main
channel areas. These other cyprinid larvae were also distributed equally, Gizzard shad
larvae were found predominantly in the main channel borders. Presumably, these higher
densities were the result of main channel spawning. The gizzard shad larvae present in the
backwater areas were distributed evenly throughout the water column. Overall, the
backwaters were important for the nest-building species found in the river and also for the
larger larvae of the pelagic species, and thus acts as a nursery area for these species.
Therefore, the backwaters do seem to be important for the fishery of the Kanawha River.