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E.R. Larson

Publications and source records attributed to E.R. Larson.

2 recordsLinked to original sources

Life-history notes on Cambarus hubbsi creaser (Hubbs crayfish) from the South Fork Spring River, Arkansas

Many crayfish species native to the southeastern United States are imperiled due to small range sizes and anthropogenic impacts such as habitat loss and introduction of non-native species. Furthermore, effective management of crayfish is limited by the scarcity of life-history and ecological data for many of these species. We report results of the first life-history study of the crayfish Cambarus hubbsi (Hubbs Crayfish). We collected 466 Hubbs Crayfish from the South Fork Spring River, AR throughout 2006 and recorded carapace lengths, wet weights, indicators of reproductive activity, and number of eggs on ovigerous females. Using length-frequency distributions, we identified four Hubbs Crayfish age classes and evaluated growth rates by plotting size by season (winter, spring, summer, autumn). Male Hubbs Crayfish were more common than females in all seasons except autumn, and males weighed more at equivalent lengths than females. Reproductive activity in Hubbs Crayfish peaked in late winter and spring, and ovigerous females were collected in March, April, and June. Ovigerous females were age II or III and carried few eggs relative to co-occurring crayfish of the genus Orconectes. Compared to these Orconectes species, Hubbs Crayfish is comparatively slow growing, long lived, with low reproductive potential, and as a result may be categorized as a K life-history strategist. Based on this species' life-history strategy and previously documented habitat specificity and taxonomic distinctiveness, Hubbs Crayfish may require monitoring and management attention normally reserved for species with smaller ranges.

Southeastern Naturalist↗

Does juvenile competition explain displacement of a native crayfish by an introduced crayfish?

The coldwater crayfish Orconectes eupunctus is endemic to the Spring and Eleven Point Rivers of Arkansas and Missouri, and appears to have been displaced from a portion of its range by the recently introduced ringed crayfish Orconectes neglectus. We examined competition among juveniles as a potential mechanism for this crayfish species displacement through laboratory and field experiments. Orconectes eupunctus juveniles survived and grew in stream cages in their former range, implicating biotic interactions rather than habitat degradation in the displacement. Laboratory experiments revealed O. neglectus juveniles were dominant in the presence of limited food, whereas size rather than species determined occupancy of limited shelter. In a field competition experiment using stream cages, O. neglectus juveniles did not inhibit growth or reduce survival of O. eupunctus juveniles. Consequently, laboratory evidence of O. neglectus dominance did not correspond with competition under field conditions. Combined with previous studies examining the effects of O. neglectus on O. eupunctus, these results suggest that competition may not be a factor in this crayfish species displacement. Alternate mechanisms for the apparent displacement of O. eupunctus by O. neglectus, such as differential predation or reproductive interference, should be investigated. ?? 2008 Springer Science+Business Media B.V.

Biological Invasions↗