Abundance and Distribution of Pink Shrimp in and around the Tortugas Sanctuary, 1981-1983

Abstract

Size and abundance of pink shrimp (Penaeus duorarum) in and around the Tortugas sanctuary in the Gulf of Mexico were surveyed monthly from September 1981 through July 1983. Samples were not taken in April and June 1983. Shrimp size varied widely at most stations and abundance varied between stations, but the average size increased with increasing depth and abundance decreased with increasing depth. A large proportion of small shrimp (<103 mm total length) in all samples combined monthly were caught inside the sanctuary, but their abundance varied monthly and annually. Small pink shrimp dominated the catch from fewer than half the stations inside the sanctuary in September-December 1981 but increased in abundance and dominated half or more of the stations inside the sanctuary in January-December 1982 and February-May 1983. January and July were the only months in which catches from at least half the stations inside the sanctuary were composed mostly of shrimp at least 103 mm long in 1983. Recruitment was continuous but uneven throughout the survey. Peak months of recruitment varied annually, occurring in January and July-September 1982 and in January and March 1983. Small shrimp were less abundant outside the sanctuary but peaks in abundance at some stations outside the sanctuary, indicating strong recruitment, occurred in January and July-August 1982 and in March 1983. Conservative population estimates (±95% confidence intervals) for the Tortugas fishing ground for September 1982-July 1983 varied from 11.8 (±5.3) x 10 6 pink shrimp in July to 52.7 (±12.8) x 10 6 pink shrimp in March. Although the trawlable area inside the southwestern sanctuary accounted for only 6% of the total trawlable area covered by the survey, the sanctuary contained an average of 36% of the total estimated pink shrimp population.