Marked subadult white shrimp were released in Galveston Bay in Aug. 1963. Recoveries indicated that there was no emigration from the bay between Aug. and mid-Oct. Shrimp increased rapidly in size during the warm summer months. Reliable estimates of natural and fishing mortality could not be obtained. Several techniques were used to obtain estimates but they varied to such a degree that results were questionable. Probable causes of these inaccurate estimates are nonrandom distribution of the marked population, fishing effort, or a combination of both.