FACTORS INFLUENCING RECAPTURE PATTERNS OF TAGGED 

 PENAEID SHRIMP IN THE WESTERN GULF OF MEXICO 



Peter F. Sheridan/ Refugio G. Castro M.,^ Frank J. Patella, Jr.,' 

 AND Gilbert Zamora, Jr.' 



ABSTRACT 



Movements of brown shrimp, Penams aztecus, and pink shrimp, P. duorarum, off the adjacent states 

 of Texas (USA) and Tamaulipas (Mexico) in the western Gulf of Mexico were examined by releasing tagged 

 shrimp within 150 l<m of each side of the border during May-July 1986. Analysis of recaptures during 

 June-August 1986 indicated that species and release location (state) significantly influenced recapture 

 patterns. Distances travelled prior to recapture, days at large, and movement speeds were greater for 

 shrimp released off Tamaulipas than for shrimp released off Texas. Brown shrimp were recaptured in 

 deeper waters than pink shrimp even though all releases were made at the same depth. Within each 

 species, shrimp released off Tamaulipas were recaptured in deeper waters than shrimp from Texas 

 releases. Relative to shoreline, directional movement of brown shrimp tended to be offshore while that 

 of pink shrimp tended to be alongshore. During the recapture period, fishing effort off Tamaulipas was 

 13% of that expended off Texas and was expended in deeper waters. Consequently, the fishing mortal- 

 ity was lower off Tamaulipas and tagged shrimp in Tamaulipas waters generally experienced a lower 

 recapture rate, longer times at large, greater distances travelled, and greater depths at recapture. Catch 

 rates off Tamaulipas were also lower than off Texas, even though both fleets used similar fishing gear. 

 The integration of all components of movement (distance, days at large, direction, recapture depth) 

 was examined by standardizing recaptures north and south of release sites by fishing effort. Paired com- 

 parisons of north versus south recaptures per unit effort (R/f) for each of 22 releases indicated no signifi- 

 cant differences in brown shrimp movements off Texas or Tamaulipas or in pink shrimp movements off 

 Texas. A significant northward movement of pink shrimp released off Tamaulipas was found. 



Brown shrimp, Penaeus aztecus, and pink shrimp, 

 P. duorarum, are the dominant species caught by 

 commercial shrimp fisheries of the western Gulf of 

 Mexico. Annual landings in the adjoining states of 

 Texas (USA) and Tamaulipas (Mexico) at present 

 average 15,250 t (metric tons) (Klima et al. 1987b; 

 Castro et al. 1986), of which brown shrimp are 

 thought to comprise at least 90% (Slater^). In 1981, 

 the United States National Marine Fisheries Ser- 

 vice (NMFS) implemented a 45-60 day closure of 

 the Texas shrimp fishery during May-July to in- 

 crease yield per recruit of brown shrimp (Klima et 

 al. 1982). Mexico has investigated the potential for 

 a similar closure but has not enacted one (Castro 

 y Santiago 1976). 

 As movement of shrimp out of U.S. waters would 



iSoutheast Fisheries Center Galveston Laboratory, National 

 Marine Fisheries Service. NOAA, 4700 Avenue U, Galveston, TX 

 77551-5997. 



^Instituto Nacional de la Pesca, Centro Regional de Investiga- 

 ciones Pesqueras, Apartado Postal #197, Tampico, Tamaulipas, 

 Mexico C.P. 89240. 



'Slater, B. M. Report on misclassification of commercial pink 

 shrimp as brown shrimp, July 16, 1982 to September 30, 1982. 

 Unpubl. manuscr., 36 p. Southeast Fisheries Center Miami Lab- 

 oratory, National Marine Fisheries Service, NOAA, 75 Virginia 

 Beach Drive, Miami, FL 33149. 



Manuscript accepted January 1989. 

 Fishery Bulletin. U.S. 87:296-311. 



reduce the effectiveness of such a closure, shrimp 

 movement patterns were assessed in a general sense 

 by a large-scale, cooperative mark-recapture pro- 

 gram in 1978-80 involving NMFS, Texas Parks and 

 Wildlife Department, and Mexico's Instituto Na- 

 cional de la Pesca (INP). Tagged brown shrimp and 

 pink shrimp were released between Galveston, TX 

 (lat. 29°15'N, long. 94°45'W) and Tampico, Tamau- 

 lipas (lat. 22°15'N, long. 97°50'W) at various depths. 

 Releases were made in estuaries and offshore at 

 various times during March-November 1978-80. 

 Long-distance movements by brown shrimp (up to 

 620 km) and pink shrimp (up to 428 km), some 

 degree of transborder stock exchange, and a trend 

 for southward movement by both species were found 

 (Castro et al. 1985; Cody and Fuls 1981; Klima et 

 al. 1987a; Sheridan et al. 1987). However, the pro- 

 gram did not analyze tag recovery patterns as in- 

 fluenced by fishing effort that is not uniform in time 

 or space. 



To assess more precisely the short-term shrimp 

 movements across the U.S.-Mexico border, NMFS 

 and INP conducted a cooperative mark-recapture 

 experiment off southern Texas and northern 

 Tamaulipas during the summer of 1986. The objec- 



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