A study of the Atlantic midshipmen, Porichthys porosissimus, in the vicinity of Port Aransas, Texas.

Life history information is presented for the Atlantic midshipman (Porichthys porosissimus (Valenciennes); Batrachoididae). Most data were obtained from fish caught by trawling in the bays and the shallow Gulf of Mexico around Port Aransas. Atlantic midshipmen occur from Virginia to Argentina and exhibit variation in color pattern and meristics throughout this range. They also show microgeographical meristic variation between the bays and the Gulf on the Texas coast. Homing, for spawning, is indicated. This species tolerates wide ranges in temperature and salinities, however it appears to be most common in waters where the salinity is between 20 and 36 ppt and where the temperature exceeds 25 C for at least one season of the year. Field observations and laboratory experiments indicate a preference for mud bottoms. The fish are nocturnal, burrowing during daylight, and the time of burrowing can be changed by artificial manipulation of day-length. Periods of submergence in excess of 24 hours occur and appear to be related to a combination of cold temperatures and short photoperiod or sudden cooling of the water temperature. Midshipmen are sensitive to low intensity light from at least far red to blue.