Document: KEN-3-71-2

Does a predator transition maintain the crayfish distributions in the South Fork of the New River, NC?

FORTINO, K.* and R.P.CREED JR.

Appalachian State University, Boone, NC 28608, USA ¹

Abstract:
Two crayfish species (Orconectes cristavarius and Cambarus chasmodactylus) occur sympatrically as adults in South Fork of the New River. However, the young-of-the-year (YOY) of the two species have a parapatric distribution. The YOY of O. cristavarius occur primarily in the New River while the YOY of C. chasmodactylus occur almost exclusively in the tributaries. We hypothesized that the rarity of C. chasmodactylus YOY in the New River could be explained by at least three processes; these included inability to tolerate the abiotic conditions, competitive exclusion by O. cristavarius YOY, and selective removal by a dominant predator. The results of a field experiment suggest that neither interspecific competition nor abiotic factors are responsible for the rarity of C. chasmodactylus YOY. The results of a laboratory experiment suggest that C. chasmodactylus YOY are significantly more vulnerable to rock bass (Ambloplities rupestris) predation than O. cristavarius. A subsequent laboratory experiment demonstrated that the two species differ in their escape behaviors, which may account for the difference in predation vulnerability. Rock bass, although common the mainstem of the New River, are very rare in the tributaries, suggesting that rock bass predation may be responsible for the virtual exclusion of C. chasmodactylus YOY from the South Fork. The anti - predator behavior of O. cristavarius may permit its coexistence with rock bass.

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This abstract is being presented at: 8:45 AM in session:
Oral Session #7: Aquatic Ecology: Shellfish to Snails.