GENETIC UNCERTANTIES IN RESTORING FISH POPULATIONS

Reisenbichler, R.R., F. M. Utter, and C.C. Krueger. 2003. Genetic concepts and uncertainties in restoring fish populations and species. In Strategies for Restoring River Ecosystems: Sources of Variability and Uncertainty in Natural and Managed Systems. American Fisheries Society. 149-183.

“Where native populations persist in the stream system to be restored, the most important management goal will be to ensure that these populations are not lost.” (page 168)

Determine the ancestral lineage, establish a bench mark for genetic and phenotypic characteristics. (page 168)

“The goal of such intervention should be to stabilize or increase population size and genetic diversity while preserving genetic adaptiveness.” (page 168)

“Hatchery programs often genetically advance the time of spawning in steelhead and coho salmon by four weeks or more.” (page 169)

“If fish are introduced, the numbers should be small-perhaps 1-10 per generation to avoid swamping the indigenous population and to minimize outbreeding depression.” (page 170)

“Immigration of one or more individuals per generation from other populations mitigates problems arising from small population size.” (page 170)

“Managers should strive to use the progeny from at least 25 pairs of adults per generation” in hatchery programs. (page 171)

“Rapidly achieving an effective population size of 500 or greater should be the primary objective… An effective size of 500 may translate to approximately 1,000 breeders per generation…” (page 171)

“Continued release of larger numbers of translocated or hatchery fish can numerically swamp naturally spawned fish and thereby reverse one or more generations of naturalization and delay self-sustainability.” (page 171)

“Introductions, if continued after the first generation (e.g. 3 years for coho salmon), should be restricted to avoid competition with naturalized individuals…” (page 171)

“…introduced fry or juvenile fish should not be larger than naturally spawned fish of the same cohort.” (page 171)

“Releases of fish should be terminated as soon as possible to allow selection and adaptation to occur unimpeded.” (page 171)

“We recommend either translocating wild adults or juveniles or releasing embryos or fry, preferably those conceived from the gametes of wild fish…Naturalization is least affected by domestication from hatchery rearing under the recommended options.” (page 173)

“Restoration should aim to re-establish the original genetic lineage and diversity of each species so that populations are genetically compatible with their…neighbors and are able to adapt and persist.” (page 173)

“Any population under restoration should be provided relief from fishing and interactions with hatchery fish so it can rapidly increase in viability through adaptation to its environment.” (page 173)