Oyster population trends in Galveston Bay, 1973-1978
Severe flooding on the Trinity River in 1973 destroyed oyster (Crassostrea virginica) populations in Trinity Bay and damaged those in the major harvest area in central Galveston Bay. Recovery was slow. Poor reproduction during 1975, 1976 and 1977 caused near depletion of oyster populations by spring 1978. However, abundant spat setting during 1978 resulted in an increase in small (seed) oysters in fall. Because market size oysters were scarce and seed oysters vulnerable to damage from oyster dredging, oystering in Galveston Bay was prohibited by proclamation of the Texas Parks and Wildlife Department (TPWD) effect 15 December 1978. Seasonal oyster harvests from public reefs in Galveston Bay ranged from 1.1 million kg (2.4 million lb) during 1976-77 to 8.7 thousand kg (19.2 thousand lb) during the abbreviated (45 day) 1978-79 seasons. As market oysters became scarce in Galveston Bay, oystering increased in mid-central bays. During the 1978-79 season, San Antonio Bay became the leading oyster producing area. The harvest of 359.5 thousand kg (792.7 thousand lb) established a record for that bay system. Private oyster lease production (confined to Galveston Bay) set a new record of 5861 meters cubed (7666.2 yards cubed). During 1976 only to be broken in 1977 when 7261 meters cubed (9497.4 yards cubed) were reported. Over a 23-year period, a decline in sample abundance of spat and small oysters has been observed although market oyster stocks remained relatively constant. A relationship between spring salinity values and spat setting was noted. Best spat sets usually occurred when salinity ranged 17-24 parts per thousand during spring. When salinity fell below 8 parts per thousand substantial spat sets did not occur.