Reproductive Status of Callinectes sapidus as an Indicator of Spawning Habitat in the South Atlantic Bight, USA

Abstract

Stocks of estuarine migrant species can be challenging to assess due to a relative lack of abundance data in offshore areas and complex interactions between spawning behavior and estuarine geomorphology. The blue crab Callinectes sapidus in the South Atlantic Bight (SAB), USA, inhabits estuaries ranging from large semi-enclosed bays to narrow river mouths where estuarine conditions extend onto the continental shelf. Mature female reproductive status was used as an indicator to identify spawning habitat, and data from long-term fishery independent surveys were used to evaluate spatiotemporal trends in abundance of spawning females. Long-term data (1990–2011) were obtained from the Southeast Area Marine Assessment Program (SEAMAP) South Atlantic survey and the Georgia Ecological Monitoring Trawl Survey. Biological samples were obtained from estuarine and offshore areas of Georgia for a detailed analysis of habitat use. Reproductive status of mature female blue crabs (ovigery, ovary development, egg remnants) was indicative of a summer peak in spawning in Georgia that occurred primarily on the continental shelf as far as 13 km offshore. SEAMAP data provide strong evidence that blue crab females spawn on the continental shelf throughout the SAB, with substantial declines in spawner abundance over time. Empirical orthogonal function analysis of SEAMAP time series was indicative of regional spawning areas defined by biogeography which are poorly aligned with fishery management jurisdictions. Indicators of reproductive status provided a powerful method for identifying spawning habitats of an estuarine migrant species, especially when spawners may disperse over the continental shelf and occur at low density.