considered Nile Blue Sulfate to be most promis- 

 ing owing to the low staining mortality and the 

 "long period" of stain retention. 



Since certain methods have been devel - 

 oped which show sufficient promise to warrant 

 large-scale field tests, the results of research 

 conducted at the University of Texas Institute 

 of Marine Science on the use of stains for mark- 

 ing shrimp are presented here. 



METHODS AND MATERIALS 



materially complicated by the burrowing habit 

 of shrimp. 



Salinity and temperature 



TTiree hundred and five daily observa- 

 tions of salinity and temperature were made 

 during the period from May lu, 1955, through 

 May 31, 1956. Mean monthly tank salinities 

 ranged from 25.9 o/oo to 38.7 o/oo and monthly 

 means of tank water temperature range from 

 14.3°C. to 29.3''C. 



Storage facilities 



All experiments were conducted on the 

 dock laboratory of the University of Marine 

 Science at Port Aransas, Texas . 



Seven storage tanks with capacities 

 ranging from 94 to 102 gallons were constructed 

 of 3/4-inch marine plywood. Each was covered 

 with 1/4 -inch hardware cloth and divided into 

 from two to four compartments by hardware - 

 cloth partitions. Five aquariums and four small 

 tanks with capacities of from 8 to 10 gallons 

 completed the storage facilities . 



Tanks and aquariums were provided 

 with continuously circulating sea water pumped 

 from a depth of approximately 6 feet below 

 mean low water in Aransas Pass. Water flow 

 averaged about 1 .8 gallons per minute to each 

 large tank and 1 gallon per minute to each aquar- 

 ium and small tank . Piping for the system 

 consisted of galvanized pipe and bronze valves . 

 Rubber hose, glass tubing, and one length of 

 lead pipe were used in distributing water from 

 the main lines to the various tanks . Although 

 the possibility of lethal contamination of the 

 water by copper and zinc from the piping caused 

 some initial concern, a flourishing growth of 

 coelenterates, annelids, moUusks, other Crusta- 

 cea, and an occasional young fish caused this 

 factor to be discounted. The rate of water ex- 

 change apparently precluded lethal concentration 

 of toxic metals within the tanks. 



The bottoms of several tanks were 

 covered with about 1-1/2 inches of mud and 

 sand in an effort to retard cannibalism . While 

 there is some evidence of reduced cannibalism, 

 problems of observation and counting were 



Shrimp - 



hi view of the fact that any tagging or 

 marking method should be applicable to all com- 

 mercial shrimp, no effort was made to separate 

 experimental animals by species. White shrimp 

 (Pen aeus setiferus ), brown shrimp (P. aztecus) , 

 and pink shrimp (P. duorarum) were used either 

 mixed or' separately, depending upon their avail- 

 ability. In experiments involving more than one 

 species, no indication of specific differences in 

 stain acceptance was apparent . 



Shrimp ranged in length from 30 mm . to 

 175 mm. and were, for experimental purposes, 

 divided into rough size groups of small (30 to 

 80 mm.), medium (80 to 120 mm.), and large 

 (120 to 175 mm.). In general, no regular 

 measurements were made of individual shrimp 

 either before or during any particular experi- 

 ment. Most of the shrimp fell within the medium 

 size classification and, unless specifically stated 

 to the contrary, medium shrimp were used in all 

 experiments . 



Shrimp were fed every other day with 

 mullet (Mugil cephalus). Trash fish were used 

 as food during the first 2 weeks of operations, 

 but this practice was discontinued following an 

 almost total mortality in one tank after feeding 

 with Synodus foetens . The mullet, either fresh 

 or frozen, was filleted and cut into pieces roughly 

 4 mm. square. These were dropped into each 

 tank or compartment on the basis of one piece 

 per shrimp. The size of the individual pieces 

 was modified when feeding predominately large 

 or small shrimp. Food supplied in this fashion 

 is readily eaten and allows for even distribution. 



Tanks were checked at least once a day 



