Evaluation of the Effects on Fin-Fish Populations Resulting from Opening the Port Mansfield Pass in the Lower Laguna Madre - Analysis of Populations of Sports and Commercial Fin-Fish and of Factors Which Affect These Populations in the Coastal Bays of Texas

Port Mansfield Pass, between the Gulf of Mexico and the lower Laguna Madre, was open twice between 1954 and 1962. Juvenile trout, pin fish and shrimp were found to be most abundant in the bay during the summer. The first time the pass was opened, the number of juvenile trout increased and then remained fairly constant for the remainder of the period. Pin fish doubled in number the first time the pass was opened and were found in the upper bay two months earlier than before the pass was open. Grooved shrimp also doubled in number when the pass was opened the first time and became abundant throughout the bay two months earlier than before the pass was open. No samples were taken during the spring and summer when the pass was closed. The pass has been reopened only seven months. Attempts to compare these last two periods with each other and with the first two periods as far as numbers of pin fish and shrimp are concerned were unsuccessful. One new species was recorded in the bay in the Port Mansfield area. The dog snapper, Lutianus jocu Block & Schneider, was collected November 1, 1962 at Stations 22a and 22b, which are one mile due east of Port Mansfield and about seven miles from the Gulf of Mexico. The opening, closing and reopening of Port Mansfield Pass had little apparent effect on salinities in the lower Laguna Madre.