Facing an alarming continuing decline of wild sea cucumber resources,
management strategies were developed over the past three decades to sustainably
promote development, maintenance, or regeneration of wild sea cucumber
fisheries. In New Caledonia (South Pacific), dedicated management efforts via
restocking and sea ranching programs were implemented to cope with the
overharvesting of the sandfish Holothuria scabra and the recent loss of known
populations. In order to investigate genetic implications of a major H. scabra
restocking program, we assessed the genetic diversity and structure of wild
stocks and hatchery-produced sandfish and compared the genetic outcomes of
consecutive spawning and juvenile production events. For this, 1358 sandfish
collected at four sites along the northwestern coasts of New Caledonia, as well
as during five different restocking events in the Tiabet Bay, were genotyped
using nine polymorphic microsatellite markers. We found that wild H. scabra
populations from the northwestern coast of New Caledonia likely belonged to one
panmictic population with high level of gene flow observed along the study
scale. Further, this panmictic population displayed an effective size of
breeders large enough to ensure the feasibility of appropriate breeding
programs for restocking. In contrast, hatchery-produced samples did suffer from
an important reduction in the effective population size: the effective
population size were so small that genetic drift was detectable over one
generation, with the presence of inbred individuals, as well as more related
dyads than in wild populations. All these results suggest that dedicated
efforts in hatcheries are further needed to maintain genetic diversity of
hatchery-produced individuals in order to unbalance any negative impact during
this artificial selection