5. Large Fisheries Harvest — The popularity of redfish and spotted sea trout effected a decline in 
these fish species so commercial harvests were banned in 1981. Sport fishermen still catch an 
estimated 3.2 million pounds of these organisms while commercial catches primarily rely on 
flounder, sand trout and sheephead. Oyster harvests fluctuate greatly from year to year 
depending on freshwater inflow and diseases, but the average output has remained a dominant 
product of Galveston Bay. Shrimp harvest both for human consumption and fish bait has 
continued to be a major product of Galveston Bay, which produces about 30 percent of the total 
Texas catch. Waterfowl hunting for geese and ducks is an important industry for the agricultural 
regions around Trinity and East Bays. 
6. Changing Habitats — The loss of habitat may be the most profound alteration occurring in 
Galveston Bay because that is a direct change in the ecosystem. The saltwater marshes have 
diminished in size as a result of subsidence of land, water level rises, diversion of freshwater, 
holding of freshwater by dams and landfills and bulkheading for developments. Seagrass bed 
losses as high as 90 percent also mean a loss of habitat for larval and juvenile forms of important 
fishery species. Another important habitat change concerns the deep channels that have been 
dug for commercial boat traffic that allow high salinity water to enter and transit across the 
shallow bay. The dredge spoils from channelization produced emergent islands and dikes in 
Galveston Bay, which has both good and bad aspects. Finally, freshwater diversion has changed 
the salinity gradient in the bay system, which has a marked effect on key organisms such as 
oysters that need freshwater inflow to avoid marine predators and diseases. The diversion of 
freshwater also alters the input locations to a more urban area where biological populations are 
less able to cope with a multitude of insults. 
Special Characteristics 
Galveston Bay and other Texas estuaries have some special characteristics that contribute to their 
vulnerability and are partially responsible for our current lack of understanding of some of the 
important processes. These prominent features include: 
1. Shallow Depths—The mean depth of Galveston Bay is 2.1 meters (6.5 feet). The main navigation 
channel is 50 miles long with a depth of 45 feet and a width of 100 feet. The undisturbed bay 
bottoms are very shallow with numerous reef areas. 
2. High Water Temperature — The waters of Galveston Bay reach temperatures in the vicinity of 
30 °C in the summer months. 
3. High Wind Speeds—The weather patterns produce high winds at all times of the year while the 
predominate direction changes from the southeast in the summer to the north in the winter. 
4. Large Evaporation/Precipitation Ratio — The high summer temperatures and wind speeds 
combine to produce a large evaporation/precipitation ratio. In south Texas, this process makes 
Laguna Madre hypersaline. As the precipitation increases from west to east in Texas, Galveston 
Bay has nearly equal precipitation and evaporation. This factor greatly influences the salinity 
distribution of Galveston Bay. 
5. Small Freshwater Inflow — Although Galveston Bay is located near the wettest region of the 
state, freshwater is a valuable resource and there is competition for that resource. Overall, about 
75 percent of freshwater is used for agricultural purposes and 20 percent is allocated for 
industrial and domestic uses. This leaves about 5 percent for the bays and estuaries. More dams 
and other freshwater uses are being planned so the flow of freshwater needed to maintain the 
estuaries' ecosystem is in jeopardy. 
6. Small Physical Circulation — The influence of tides on currents is relatively small in Texas bays. 
The mean tidal fluctuation is about 2 feet inside Galveston Bay while maximum range is about 
2.6 feet. The wind becomes very important in both the horizontal movement and vertical mixing 
of bay waters. Normal tidal predictions without wind factors are not very accurate when 
compared to actual water heights in Galveston Bay. 
7. Large Biological Production — In good years, as much as 10 to 15 percent of oyster landings in 
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