Historical translocations and stocking alter the genetic structure of a Mediterranean lobster fishery

Stocking is often used to supplement wild populations that are
overexploited or have collapsed, yet it is unclear how this affects the
genetic diversity of marine invertebrate populations. During the 1970s, a
lobster stock enhancement programme was carried out around the island of
Corsica in the Mediterranean using individuals translocated from the
Atlantic coast of France. This included the release of thousands of
hatchery-reared post-larval lobsters and several adult individuals, but no
monitoring plan was established to assess whether these animals survived
and recruited to the population. In this study, we sampled European
lobster (Homarus gammarus) individuals caught around Corsica and tested
whether they showed Atlantic ancestry. Due to a natural marked
phylogeographic break between Atlantic and Mediterranean lobsters, we
hypothesised that lobsters with dominant (>0.50) Atlantic ancestry
were descended from historical stocking releases. Twenty Corsican lobsters
were genotyped at 79 single nucleotide polymorphisms and assignment
analysis showed that the majority (13) had dominant Atlantic ancestry.
This suggests that the hatchery stocking programme carried out in Corsica
during the 1970s, using individuals translocated from the Atlantic coast
of France, has likely augmented local recruitment but at a cost of
altering the genetic structure of the Corsican lobster population.