Figure 2.7. Low elevation areas (0-1.6 meters, shaded) Figure 2.8. Low elevation areas (0-1/6 meters, shaded) 
where Galveston Bay wetlands werelocated in where future Galveston Bay wetlands could 
1979, barring development (15). exist, barring development, after a 1.6-meter 
rise in sea level by the year 2100 (15). 
Oyster survival and production are excellent indicators of the natural patterns of mixing of fresh 
and salt waters (19,20). Under ideal situations oysters survive and grow well at salinities of 10 to 35 
ppt. However, salinities of more than 20 ppt bring predators (such as oyster drills) and disease (such 
as "dermo") that decrease survival and production. Fresh water kills are also incurred if salinities 
drop below 10 ppt for extended periods or at the wrong time of year. The net result is the typical 
pattern of oyster reef formation primarily where waters are consistently 10 to 20 ppt. Major shifts in 
the seasonal timing or amounts of discharge from river systems could cause long-term changes in 
oyster reef distribution and production. 
To a constricted arm of the Galveston Bay system, such as West Bay, a freshet of unrestricted flow 
can be quite beneficial for oysters. West Bay had been a high salinity-low production bay until a July 
1979 tropical storm dropped 110 cm of rain in 24 hours (59). Salinities were dramatically lowered and, 
combined with subsequent high settlement of oyster spat, reported oyster harvest jumped from zero 
tol,225 metric tons in the November 1982 through April 1983 season and 907 metric tons the fol¬ 
lowing season (Figure 2.10) (60). Since then, salinities have increased and reported oyster harvest has 
tapered off. 
When fresh water inflow patterns are artificially altered, the results may not be so beneficial to 
white shrimp productivity. Sabine Lake is located between Galveston Bay and Lake Calcasieu, 
Louisiana. Dams were built on the Sabine and Neches Rivers in 1965-1966 that contained the natural 
peak river flows of January through May for later release in generating electricity in the normally low 
flow period of June through October (61). Portions of the surrounding marshes were also leveed off 
at the same time. These summer flood conditions negated recruitment of white shrimp to nursery 
areas by artificially lowering salinities to unacceptable levels. The Sabine Lake white shrimp fishery 
collapsed, while fisheries in Galveston Bay and Lake Calcasieu continue (Figure 2.11) (56). 
46 
