Overexploitation of marine species invariably results in population decline but can also
have indirect effects on ecological processes such as larval dispersal and recruitment that
ultimately affect genetic diversity and population resilience. We compared microsatellite
DNA variation among depleted and healthy populations of the black-lip abalone Haliotis
rubra from Tasmania, Australia, to determine if over-fishing had affected genetic diversity.
We also used genetic data to assess whether variation in the scale and frequency of larval
dispersal was linked to greater population decline in some regions than in others, and if larval
dispersal was sufficient to facilitate natural recovery of depleted populations. Surprisingly,
allelic diversity was higher in depleted populations than in healthy populations (P < 0.05).
Significant subdivision across hundreds of metres among our sampling sites (FST = 0.026,
P < 0.01), coupled with assignment tests, indicated that larval dispersal is restricted in all
regions studied, and that abalone populations across Tasmania are largely self-recruiting.
Low levels of larval exchange appear to occur at the meso-scale (720 km), but age estimates
based on shell size indicated that successful migration of larvae between any two sites may
happen only once every few years. We suggest that genetic diversity may be higher in
depleted populations due to the higher relative ratio of migrant to self-recruiting larvae. In
addition, we expect that recovery of depleted abalone populations will be reliant on sources
of larvae at the meso-scale (tens of km), but that natural recovery is only likely to occur on
a timescale unacceptable to fishers and resource managers.