THE STATUS AND LONG-TERM TRENDS OF OYSTER REEFS IN GALVESTON BAY, TEXAS

The oyster reefs of Galveston Bay were surveyed using a new acoustic t echnique which permitted conducting a detailed survey over a wide geog raphic area. The results of this survey were compared to a more limite d survey conducted circa 1970 and to earlier, less detailed accounts. Our survey approximately doubles the known area of reef and unconsolid ated shelly substrate in the bay system.Certain components of the Galv eston Bay reef system have persisted throughout recorded time; others have exhibited substantial malleability, changing position and shape i n response to natural and man-made changes in the bay system. Regional subsidence has resulted in an increase in water depth over the reefs, thus reducing the acreage intertidally and subaerially exposed, and a reas of high subsidence have suffered reef attrition due to siltation. Channelization, dike construction, and the disappearance of major bar rier reef have substantially changed bay circulation patterns. As a co nsequence, the equilibrium that once existed between the reefs and bay circulation has been modified, resulting in loss or attrition of a nu mber of reefs in areas of lowered salinity and the accretion of reefs parallel to the new isohaline structure of the bay. Thus, some reefs a re no longer optimally located for continued high productivity; many a reas of low reef coverage would now support productive reef if substra te became available. In optimal areas, reefs more than doubled in size in 20 yr. No evidence was found to suggest that the oyster fishery ha d contributed to reef attrition, however leasing may have encouraged r eef accretion. Artificial reefs did no worse or better than their natu ral nearby counterparts, indicating siting as the overriding concern f or successful artificial reef emplacement. The Houston Ship Channel ha s extended the isohalines upestuary to the great benefit of oyster pop ulations and the oyster fishery. Over 1000 hectares of reef have devel oped along this channel, a substantial fraction of which exists betwee n the channel edge and the crest of the parallel-trending spoil banks. Both a channel and a spoil bank are required for development of reef along channels. Channels in which spoil was placed on only one side al ways have reef development predominately or exclusively on that side.