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1 March 2007 CONSERVATION STRATEGIES SUPPORTED BY NON-LETHAL LIFE HISTORY SAMPLING OF THE U.S. FEDERALLY LISTED ILLINOIS CAVE AMPHIPOD, GAMMARUS ACHERONDYTES
Michael P. Venarsky, Frank M. Wilhelm, Frank E. Anderson
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Abstract

Many cave species exhibit k-selected life history characteristics, i.e., long life span, slow growth, and low reproductive effort, which can reduce their ability to survive rapid changes in environmental conditions and their potential for recovery from events that reduce their densities. In this study, we examined aspects of the life history, growth rate, and reproductive timing of the U.S. federally listed Illinois cave amphipod, Gammarus acherondytes, to assess its potential for recovery. Sampling between October 2003 to March 2005 with non-lethal techniques in Reverse Stream Cave, Illinois, U.S.A. showed that pre-juveniles and juveniles generally constituted > 50% of the population and thus strongly influenced fluctuations in population density. Except in September 2004, ovigerous females were collected every month, indicating that reproduction occurred year-round. Distinct peaks of pre-juveniles were observed from February to May and August to October. The seasonal recruitment of young appeared to be correlated with incubation time and flood events. Because it was difficult to track individual cohorts, the exact time to maturity or the life span could not be determined empirically. However, the minimum time to maturity was estimated at 14 to 16 months using a modeled growth curve. Our results suggest that G. acherondytes should recovery rapidly from perturbations if left undisturbed. A management strategy to aid recovery could be to reduce cave visitation during the major phases of recruitment. Additionally, our results indicate that establishing a laboratory population for use in future studies or to propagate individuals for reintroduction should require only one-and-a-half to two years. Our study shows how basic life history information obtained via non-lethal sampling can provide managers with vital information to develop conservation strategies for endangered species.

Michael P. Venarsky, Frank M. Wilhelm, and Frank E. Anderson "CONSERVATION STRATEGIES SUPPORTED BY NON-LETHAL LIFE HISTORY SAMPLING OF THE U.S. FEDERALLY LISTED ILLINOIS CAVE AMPHIPOD, GAMMARUS ACHERONDYTES," Journal of Crustacean Biology 27(2), 202-211, (1 March 2007). https://doi.org/10.1651/S-2782.1
Received: 21 July 2006; Accepted: 1 October 2006; Published: 1 March 2007
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