A pilot study to analyze effects of freshwater inflows and metabolic stresses for important fish species in Corpus Christi Bay, Texas
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The spotted seatrout, Cynoscion nebulosus, is an excellent fish for laboratory-field studies involving measurements of respiratory metabolism for the assessment of freshwater inflow effects on coastal brackish and marine waters. The scope for routine activity, i.e., the difference between metabolic rates at routine swimming rates and standard maintenance rates, is a good measure of the stress effects of salinity, over and above any sublethal stress from other causes. The scope for routine activity of the spotted seatrout indicates clearly that the optimal salinities at 28° C are about 20 ppt with a rapid decrease in scope both above and below 20 ppt. It is estimated that the scope below about 5 ppt and above 60 ppt would be so small that the fish would be stressed to the point where growth and possibly survival would be affected adversely, especially if additional slight, but normal, stresses occurred. The scope values for the two Nueces Bay salinity levels tested are not too different from those of the sea water, although the scope-salinity curve might be slightly different from the seawater curve due to somewhat different stress effects of Nueces Bay waters. ... A series of recommendations is made for the improvement of the techniques and increasing the acuity of the scope comparisons. It is also recommended that the rationale of continuing studies be broadened by making scope comparisons among at least three bay-estuary systems.
Final report to Texas Water Development Board for contract IAC-7475 1715
18 September 1975
18 September 1975