Effects of Salinity on Eastern Oysters: Locating Lower-Salinity Tolerant Populations and Defining Resource Zones Suitable to Restoration, Fisheries, and Aquaculture.

Abstract

Eastern oysters (Crassostrea virginica) provide valuable ecosystem services and support a productive commercial industry in the northern Gulf of Mexico. Declining abundance from water quality changes and other factors drives development of management and restoration strategies focused on a comprehensive, metapopulation approach. Identifying oyster resource zones based on water quality combined with selective breeding of oysters adapted to specific conditions provides strategies to support aquaculture development and ensure resilient oyster populations and high production. Using 2015-2019 satellite-derived continuous salinity and temperature data for coastal Louisiana, this work created maps defining oyster resource zones supportive of (1) broodstock sanctuary reefs, (2) productive reefs during dry and (3) wet years, and (4) off-bottom aquaculture development. Unique salinity regimes occurred across estuaries, with high salinity variation critically limiting broodstock sanctuary areas. Further, these maps suggest consideration of offshore areas for aquaculture development and identify a need to shift restoration areas down-estuary due to up-estuary freshening. Accounting for variable water quality conditions over time acknowledges temporally variable reef success as individual populations in different zones will thrive in different years, thus promoting overall oyster persistence and production long-term. Reef persistence and oyster production would also benefit from ensuring oyster populations within zones or identified for use in aquaculture are uniquely adapted to decreasing salinities. A second study assessed unique Louisiana oyster populations from assumed low-salinity areas for population-specific low salinity tolerance. Progeny of these populations were grown at an intermediate (10-20) and low salinity (