ANDERSON and LINDNER; BIOLOGY OF ROVAL RED SHRIMP 



formed into a myriad of shallow depressions and 

 mounds, pitted with holes. Claws protruding 

 from many of these holes indicated the richness 

 of the crustacean bottom fauna. Some fishes 

 were also observed in holes, but these were not 

 nearly so numerous. From the bottom port it 

 was possible to see directly into some of the 

 holes, and we observed animals that would have 

 been invisible at an angle." 



These fishing grounds are directly under the 

 Gulf Stream. 



DATA AND METHODS 



The data were obtained from operations of 

 several vessels either owned or leased by the 

 BCF — M/ V Combat, a 30-m converted mine- 

 sweeper; M/V Silver Bay. a 29-m New England- 

 type trawler; and the R/V Oregon, a 30-m 

 trawler. Bullis (1956) and Bullis and Rathjen 

 (1959) have given details of vessels, gear, and 

 operating procedures. 



The data consist of length measurements and 

 observations on ovarian development taken from 

 random samples (100 specimens, if this number 

 or more were caught; the total catch if fewer 

 wei'e caught) at irregular intervals from 1957 

 to 1967 (Table 1). They also consist of one set 



Table 1. — Cruise dates, number of stations, and number 

 of H. robustiis in samples. 



of total length-carapace length measurements 

 from nonrandom samples taken during July 



1957. Date, location, depth (with two excep- 

 tions) , and duration of haul are known for each 

 trawling station from which the samples were 

 taken. Data on bottom temperatures are not 

 available. The location of each trawling station 

 was obtained by sonar fixes and the depth, in 

 fathoms, from sonic depth recordings. The 

 depths have been converted to the nearest meter. 



Throughout almost every cruise during which 

 length measurements were taken, the operation 

 simulated commercial fishing; consequently the 

 shrimp measured were caught by several types 

 of trawls in a wide range of sizes. Mesh sizes, 

 however, probably did not vary much. The 

 most commonly used trawl was constructed of 

 "commercial" nylon webbing with 2-inch (50.8- 

 mm) stretched mesh in the body and li/>-inch 

 (38.1-mm) stretched mesh in the cod end. These 

 sizes of mesh are generally used by commercial 

 shrimp fishermen. As shown by Berry and 

 Hervey (1965), the greatest inside dimensions 

 usually are somewhat less than 50.8 mm and 38.1 

 mm, respectively. Measurements we made on 

 the greatest inside mesh dimensions of the 

 shrimp trawls used by the exploratory vessels 

 for capturing H. robustus indicate a range be- 

 tween 43 and 48 mm (mean 45.7 mm or 1.8 

 inches) for the "commercial" 50.8-mm mesh and 

 between 30 and 34 mm (mean 31.7 mm of I14 

 inches) for the "commercial" 38.1-mm mesh. 



Mesh selectivity studies have not been made 

 on H. robustus, but we doubt that the variabiHty 

 in types and sizes of trawls appreciably aflfected 

 the lengths of shrimp caught. We assume that 

 mesh selectivity would be about the same as that 

 shown by Berry and Hervey (1965) for Penaeus 

 aztecus for 2-hr tows. Most of our tows lasted 

 2 to 4 hr, with 3-hr tows predominating. The 

 50 C^ escapement length for 31.7-mm mesh would 

 thus be about 70 mm total length and specimens 

 of H. robustus less than 50 mm total length, if 

 present, would have been represented in the 

 catches. We can expect, however, that speci- 

 mens less than about 100 mm total length prob- 

 ably were not represented in their true per- 

 spective in the random samples. 



Total length measurements (tip of rostrum 

 to end of telson — all length measurements are 



315 



