REPORT OF THE BUREAU OF COMMERCIAL FISHERIES 

 BIOLOGICAL LABORATORY, GALVESTON, TEXAS 



Fiscal Year 1967 



ABSTRACT 



Progress of research is reported. Emphasis is on shrimp, and the research 

 involves the fields of biology, population dynamics, ecology, and oceanography. 



REPORT OF THE DIRECTOR 



GENERAL 



This Laboratory has five research pro- 

 grams--Shrimp Biology, Shrimp Dynamics, 

 Estuarine, Experimental Biology, and Gulf 

 Oceanography. Although seemingly different, 

 each progrann is designed, either directly 

 or indirectly, to provide information that 

 will permit optinnum use of stocks of com- 

 mercial shrimp in the Gulf of Mexico. More 

 specifically, our research is designed to 

 define the entire life histories of the species; 

 to detern-iine the response of the species to 

 fishing and to their environment; and to 

 describe in time and space the environ- 

 mental variations. 



Each of the five programs has a nunnber 

 of individual projects. Progress made in 

 these projects during fiscal year 1967 con- 

 stitutes the bulk of this report, but 1 sum- 

 nnarized here some of the highlights of our 

 research. 



The refining of our techniques for rearing 

 larval shrimp spawned in the laboratory en- 

 abled us to culture successfully tens of thou- 

 sands of postlarvae. Our major problenn has 

 been to grow algal foods in quantities suf- 

 ficient to sustain larval growth and survival. 

 In one rearing experiment, however, enough 

 postlarval white shrinnp were reared to stock 

 one of the experinnental ponds in which we 

 are studying the feasibility of rearing shrimp 

 under seminatural conditions. 



After being placed in the experimental 

 pond, the shrimp grew rapidly for 35 days, 

 but then growth virtually ceased. When the 

 shrimp were harvested, 84 percent of the 

 original stock had survived and the projected 



yield of whole shrimp was 575 pounds per 

 acre (645 kg. per hectare). 



A nnajor breakthrough toward management 

 of a fishery was realized from nnark- 

 recapture studies on the pink shrimp of the 

 Tortugas grounds. From these studies, we 

 determined that natural mortality was con- 

 siderably lower than had been previously 

 reported. Of even greater significance, we 

 also determined the optimum size at which 

 to begin fishing for pink shrimp on the Tor- 

 tugas grounds. The success of these studies 

 has led to renewed efforts to establish similar 

 criteria for the brown and white shrimp 

 fisheries. 



Although the importance of estuaries as 

 nursery grounds for many commercial ma- 

 rine species is well documented, modifica- 

 tion of these waters along the Gulf coast 

 by residential, industrial, and agricultural 

 expansion is increasing at a tremendous rate. 

 Our ecological studies in Galveston Bay have 

 shown that the shore and submerged plants, 

 particularly in shallow water, provide nursery 

 habitats for the young of shrinnp and other 

 species. Destruction of these plants, by what- 

 ever means, makes the estuaries useless as 

 nursery grounds. 



Field observations on the occurrence of 

 white, brown, and pink shrimps indicate that 

 environmental factors affect the distribution 

 of the species. The extreme conditions of 

 tolerance by the three species were, how- 

 ever, unknown. In the laboratory, tests made 

 under controlled conditions showed that the 

 ability of shrimp to tolerate extremes of 

 temperature and salinity varied with the 

 species and age (or size) of the shrimp. 



