Genetic management guidelines for captive propagation of freshwater mussels

Journal of Shellfisheries Research, August, 2006 by Jess W. Jones, Eric M. Hallerman, Richard J. Neves

The possibility of releasing host fish infested with glochidia would allow natural dispersal and colonization of habitats otherwise excluded by only releasing hatchery-reared juveniles, spread risk of mortality at localized stream reaches, and may minimize future inbreeding. However, this practice risks loss of juveniles after settlement into unfavorable areas, and makes monitoring of survival success difficult. Under some circumstances, such as in small streams, this strategy may be more effective than site specific releases of cultured juveniles.

Guideline 9: Release an appropriate number of juvenile mussels from an appropriate number of parents at release sites to maximize effective population size ([N.sub.e]), and at an early life stage to maximize survival in the wild, and to minimize the effects of domestication selection.

Monitoring and Adaptive Management

Captive propagation of mussels is a new recovery option, and is as much an art as a well-established science at this time. Success must be measured not in terms of how many juveniles are out-planted, but rather in terms of how many juveniles recruited into or established a spawning population. Furthermore, data on (1) number of gravid females used to produce juveniles; (2) locations where females were collected; (3) number of juveniles released per site and river location; (4) juvenile characteristics (e.g., age, size and condition) and (5) river conditions at the time of release, should be recorded and submitted to the responsible natural resource agency. Standard data sheets should be prepared and used for all releases. It is critical that protocols to monitor survival and recruitment of artificially propagated juveniles are established and implemented, and project data are collected in an appropriate agency database. Ultimately, success will be measured in terms of the establishment of self-sustaining populations. Hence, monitoring should be regarded as an integral part of any captive propagation and release program.

Because of the many unknowns in mussel biology and uncertainties in long-term effects, hatchery programs may be experimental in nature, but should be integrated into an adaptive management program, with careful attention to monitoring and reevaluation of goals and protocols. Under the adaptive management paradigm, results of monitoring are used, as appropriate, to modify management goals and operations procedures so that, over time, learning occurs and the overall program becomes more effective (Holling 1978). Adaptive management has proven useful for management of Pacific salmonids (Hilborn & Winton 1993, Walters et al. 1993), and we acknowledge that it is essential for captive propagation and outplanting of imperiled mollusks.

Guideline 10: Monitoring, evaluation, and database management should be regarded as an integral part of any augmentation or restoration program, followed as appropriate with modification of program goals and operations procedures to promote program effectiveness.