NOTES 



EQUIPMENT FOR HOLDING AND 



RELEASING PENAEID SHRIMP 



DURING MARKING EXPERIMENTS' 



Personnel of the National Marine Fisheries 

 Service Biological Laboratory at Galveston, 

 Texas, have conducted numerous mark-recap- 

 ture ex]3eriments to obtain information on the 

 movement, growth, and mortality of penaeid 

 shrimp. These experiments were carried out 

 under a variety of conditions at sea and in coastal 

 bays. Several types of specialized equipment 

 were developed to overcome problems of holding, 

 handling, and releasing shrimp during the mark- 

 ing phase of these experiments. Some of this 

 equipment has been described previously by 

 Costello (1964). Holding tanks, a cooling unit, 

 and two devices used to transport shrimp to the 

 sea floor are described here. 



Holding Facilities 



A number of factors were considered in the 

 design of tanks for holding shrimp. Construc- 

 tion materials had to be relatively light in weight, 

 require little maintenance, and be nontoxic to 

 shrimp. Provisions also were needed to permit 

 lapid water exchange, minimize water turbu- 

 lence within tanks, and control water temper- 

 ature. The tank design in Figure 1 meets these 

 needs and has proved successful for both sea- 

 and land-based operations. It is constructed of 

 light gray fiberglass with wood reinforcement 

 and weighs about 114 kg (250 lb.) . Advantages 

 of the light color are that it reflects heat and 

 makes shrim]) easily visible in the tank. To 

 permit rapid drainage or water exchange, a 

 polyvinyl chloride (PVC) pipe, 7.6 cm (3 inch- 

 es) in diameter, is molded into each end of the 

 tank near the bottom. Filter .screens, used to 



' Contribution No. 304, National Marine Fisheries 

 Service Biological Laboratory, Galveston, Texas. 



prevent loss of shrimp in outflowing water, have 

 a large surface area to minimize clogging. A 

 one-quarter section of PVC pipe, 7.6 cm (3 

 inches) in diameter, is molded to the top of the 

 tank at each end as a splash rail to reduce 

 spillage. 



Five sets of guides in the tank support baffles 

 that reduce water turbulence at sea and are used 

 to separate groups of shrimp in a tank (Fig. 1). 

 The baffles have a frame of aluminum flashing 

 covered with sheets of patterned aluminum 

 0.063 cm (0.025 inch) thick. 



During field use, a series of two to four tanks 

 are linked to provide either recirculating water 

 or continually flowing new water. The pump 

 used depends on the volume of water required. 

 Normally, we use a cast-iron pump powered by 

 a 0.5-hp electric motor (110-220 v) that dis- 

 charged 114 to 132 liters (30 to 35 gal) per min. 

 As the water is discharged into the tanks, it 

 passes through siphon filler-drain nozzles (Cos- 

 tello, 1964) which draw air into the circulation 

 system and aerate the water. The aeration unit 

 (Fig. 2), made of 1.9-cm (0.75-inch) pipe, may 

 be attached temporarily at any convenient place 

 on the tank. The amount of air that enters the 

 water is regulated by valves in each air line. 



Because it is difficult to keep shrimp alive 

 when water temperatures exceed about 27° C 

 (80° F), cooling units are used to lower and 

 maintain temperatures in holding tanks. A 

 cooling unit of our own design is shown in Fig- 

 ures 3 and 4. The casing consists of a PVC 

 pipe, 25.4 cm (10 inches) inside diameter, 45.7 

 cm (18 inches) long, and 0.9 cm (0.37 inch), 

 thick, and top and bottom pieces of PVC flat 

 stock, 30.5 by 30.5 by 1.3 cm (12 by 12 inches 

 by 0.5 inch) with circular grooves 0.6 cm (0.25 

 inch) deep. 0-ring gaskets that fit the grooves 

 prevent leakage of water. The refrigerant coil 

 is made from 0.9-cm (0.37-inch) diameter stain- 

 less steel tubing, 9 m (30 ft) long. A thei-mo- 

 stat sensor receptacle, inserted through the top 



247 



