Observations on Age and Growth of the Eastern Oyster Crassostrea virginica in South Carolina Saltmarsh Tidal Creeks

Abstract

The eastern oyster Crassostrea virginica contributes important ecological and structural elements to estuarine ecosystems worldwide. Oyster reef persistence requires regular recruitment as well as growth by existing individuals. Saltmarsh tidal creek oyster population age structure and growth rates directly influence local benthic–pelagic coupling and biogenic habitat formation. Recruitment monitoring, substrate deployments (2017–2020), and field surveys (2018) were conducted in North Inlet Estuary, SC, to quantitatively describe oyster age–shell height relationships, population age structure, daily growth rates, and survivorship. Multiple recruitment events resulted in three to four cohorts each year. Oysters exhibited rapid shell growth but most died by the end of their second growth season after attaining shell heights of less than 100 mm. Daily growth rates immediately after recruitment (approximately 0.07–0.29 mm day–1) and within the first 2 y (0.1–0.4 mm day–1) allow maximum shell heights of 50–55 mm after to 6–8 mo, 80 mm within 1 y, and 140 mm within 1.6 y. Recruitment timing strongly influenced shell heights after 1 y, with July recruits approximately 33% larger than May recruits within the same year. The North Inlet oyster population age structure was dominated by oysters in their first (55%) or second (45%) growth season, with individuals less than 100 mm shell height composing approximately 99% of the population. Oyster survivorship beyond 2 y appears to be unusual. The opportunistic life history strategy used by North Inlet oysters incorporates multiple large recruitment events each year and rapid growth rates to offset short life spans so as to maintain reef populations and related ecosystem services.