Physioecology of the grass shrimp, Palaemonetes pugio, in the Galveston Bay estuarine system.

The seasonal distribution, growth rate, and reproductive potential of the grass shrimp, Palaemonetes pugio, as affected by temperature and salinity were studied in the Galveston Bay estuarine system, by means of a field survey of 13 stations from March, 1963 to February, 1964, and a controlled laboratory experiment. Grass shrimp appeared throughout the year with greatest abundance in July and October. Abundance was greatest in waters of 10-20 ppt salinity and least in <1.0 ppt salinity. The abundance of the sexes (males, ovigerous females, and non-ovigerous females) of grass shrimp is related to temperature with the sex ratio (males to all females) approximately 1:1. Growth to maturity (20-24 mm) takes two to three months during June-September, and four to six months during the remainder of the year. No appreciable increase in length or weight could be attributed to salinity. Greatest increase in length and weight could be attributed to salinity. Greatest increase in lngth and weight attributed to temperature occurred in waters of >30C and least in waters of 11 C to 14 C. There is a size difference between males (23.5 mm), non-ovigerous females (26.2 mm), and ovigerous females (30.0 mm). Longevity of grass shrimp is about one year. P. pugio can survive over a wide range of salinities and temperatures with best survival in waters of 4-16 ppt salinity and 18 C to 25 C. Ovigerous females were collected from March to October with two peak spawning seasons, one in early summer (July) and the other in early fall (October). Water temperatures of approximately 18-20 C are required for reproduction to occur. The largest females (28-42 mm) produce egg masses in the first spawning peak with gradual replacement by smaller individuals in the second peak. The number of eggs carried by ovigerous females increased in a geometric progression related to length. Number of eggs in an egg mass is a linear function of the female's length.