SEASONAL DISTRIBUTION AND RELATIVE ABUNDANCE OF PLANKTONIC-STAGE 

 SHRIMP (Peuaeus spp.) IN THE NORTHWESTERN GULF OF MEXICO, 1961' 



By Robert F. Temple and Clarence C. Fischer. Fishery Biologists 

 Bureau of Commercial Fisheries Biological Laboratory, Galveston, Texas 77550 



ABSTRACT 



Planktonic stages of shrimp (Penaeiis spp. ) were sampled 

 systematically in the Gulf of Mexico near Galveston, Tex., 

 during January-December 1961. The Gulf-V plankton net 

 was used every 3 weeks at stations established at water 

 depths of 14, 27, 46, and 82 m. The study area encom- 

 passed about 20,725 km.- 



Trends in seasonal abundance of larvae varied with 

 depth. At 14-m. stations a unimodal trend was ob- 

 served, and peak abundance was during May to Septem- 

 ber. In deeper waters a bimodal trend was apparent; 

 peak abundance extended from late summer through 

 fall. At all depths, trends in larval abundance increased 

 as bottom water temperatures increased. 



Postlarvae were taken in plankton tows during Janu- 

 ary to April but were most abundant during August to 



December. 



Distinct shifts in the areal distribution of larvae and 

 postlarvae were apparent. During January to March, 

 larvae were restricted to water deeper than 14 m. and 

 shallower than 82 m. whereas postlarvae occurred in 

 all depths. This situation was generally reversed in 

 April to August, when larvae were at all depths, but the 

 distribution of postlarvae was restricted. In September 

 to December, distribution patterns of larvae and post- 

 larvae were generally similar. 



On the basis of this study and laboratory experiments 

 on larval development and postlarval growth rates as 

 affected by temperature, support is given to the premise 

 that brown shrimp larvae or postlarvae, or both, over- 

 winter in waters over the Continental Shelf. 



The shrimp fishery in the Gulf of Mexico has 

 expanded rapidly within the past 20 years and 

 is now the most valuable fishery in the United 

 States. Since 1950 the yearly harvest has fluc- 

 tuated around 200 million pounds. Although 

 about six members of the family Penaeidae are 

 taken in the fishery, only three species — the 

 brown shrimp, Penaeus aztecus Ives; the pink 

 shrimp. P. duoranini Burkenroad; and the 

 white shrimp. P. setife)its (Linnaeus) — con- 

 tribute significantly to the catch. 



Before 1959, research designed to provide 

 management programs for optimum utiliza- 

 tion of these shrimp stocks did not increase at 

 the same rate as the value of this fishery. In 

 1959, however, the Bureau of Commercial Fish- 

 eries began a program of shrimp research that 

 has expanded considerably during the past 7 

 years. The general aims of the program were 

 stated by Kutkuhn (1963). The present study 

 of the seasonal distribution and abundance of 



Published September 1967. 



' Contribution Xo. 221. Bureau of Commercial Fisheries Biological 

 Laboratory. Galveston. Tex. 



planktonic-stage Penaeus spp. in the north- 

 western Gulf of Mexico is a part of this 

 research. 



Considerable information has been published 

 on the early life history of the white shrimp 

 (Weymouth, Lindner, and Anderson, 1933; 

 Burkenroad, 1934; Pearson, 1939; Anderson, 

 King, and Lindner, 1949). Brown and pink 

 shrimp have similar early life histories, al- 

 though bathymetric and geographic distribu- 

 tions of the adults are different. In general, 

 these shrimp spawn in waters over the Con- 

 tinental Shelf; brown shrimp spawn at least 

 as far as 198 km. (110 nautical miles) offshore 

 in depths as great as 110 m. The eggs are 

 slightly denser than sea water and settle to the 

 bottom when spawned. After hatching, the 

 young become planktonic and develop through 

 three larval (naupliar, protozoeal, and mysis) 

 and several postlarval stages. They enter the 

 estuaries as postlarvae, grow rapidly to sub- 

 adult size, and then migrate offshore to com- 

 plete their growth and spawn. 



The earlier work on white shrimp provides 



FISHERY BULLETIN: VOLUME 66, NO. 2 



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