Spatiotemporal Variation in Oyster Fecundity and Reproductive Output in a Network of No-Take Reserves

Abstract

Adult fecundity and reproductive potential can be critical determinants of subsequent larval supply and juvenile recruitment, and important determinants of placed-based management, especially when selecting sites for marine reserves where larval export is an expected outcome. We quantified spatiotemporal variation in fecundity and reproductive potential of female oysters (Crassostrea virginica) within a network of no-take oyster broodstock reserves by sampling over 3 y at 3 spatial scales: (1) per capita, (2) per square meter, and (3) per reserve. A total of 2,596 oysters were collected using scuba from six reserves in Pamlico Sound, NC, during 2006 to 2008 and processed in the laboratory for fecundity. Per-capita fecundity ranged from 0–340,500 eggs, and increased exponentially with oyster size, peaking in May of all years. In general, per-capita fecundity was highest at more inland mesohaline reserves, whereas reproductive potential per square meter and reserve reproductive potential were highest at more seaward polyhaline reserves as a result of a combination of relatively high density, and large oyster size and reserve areas. All 3 reproductive metrics increased in general over time. These results suggest that inland broodstock reserves should be prioritized for stock enhancement/seeding—and more seaward reserves for reserve expansion—and highlight the need to consider spatiotemporal variation and the scale at which a key demographic rate (fecundity and reproductive potential) is expressed when assessing the efficacy and conservation/restoration targets of marine reserves.