Effect of hypoxia on habitat quality of striped bass (Morone saxatilis) in Chesapeake Bay

Eutrophication- induced hypoxia may affect both benthic and pelagic organisms in coastal systems. To evaluate the effect of hypoxia on pelagic striped bass ( Morone saxatilis), we quantified the growth rate potential ( GRP) of age- 2 and age- 4 fish in Chesapeake Bay during 1996 and 2000 using observed temperature, dissolved oxygen, and prey abundance information in a spatially explicit bioenergetics modeling framework. Regions of the Bay with bottom hypoxia were generally areas with high quality habitat ( i. e., GRP > 0 g center dot g(-1) center dot day(-1)), primarily because prey fish were forced into warm, oxygenated surface waters suitable for striped bass foraging and growth. In turn, by concentrating fish prey above the oxycline and removing bottom waters as a refuge, hypoxia likely enhanced striped bass predation efficiency and contributed to the recovery of striped bass during the mid- 1990s, a time when the striped bass fishery also was closed. This short- term positive effect of hypoxia on striped bass, however, appears to have been counterbalanced by a long- term negative effect of hypoxia in recent years. Ultimately, hypoxia- enhanced predation efficiency, combined with an abundance of striped bass due to restricted harvest, appears to be causing overconsumption of prey fishes in Chesapeake Bay, thus helping to explain poor growth and health of striped bass in recent years.