FISHERY BULLETIN: VOL 77. NO, 4 



factors affecting maturation and spawning of 

 adults and survival of larvae, juveniles, and sub- 

 adults apparently have pronounced influences on 

 recruitment. While some maturation and spawn- 

 ing takes place year around, peaks occur in 

 spring and fall. 



The size composition of the reported annual 

 catches of brown and white shrimp greatly affects 

 the value of these catches. For the years 1959-75, 

 Caillouet and Patella (1978) estimated that the 

 ex-vessel value (expressed in dollar units based 

 upon 1975) of reported annual catches of brown 

 shrimp in Texas was 1.6 times greater than that 

 in Louisiana, for a given weight of catch. For 

 white shrimp, it was 1.2 times greater in Texas 

 than in Louisiana. They attributed these differ- 

 ences in value of the catches to differences in size 

 composition of the catches because larger shrimp 

 command higher prices than do smaller shrimp 

 on the market. In addition, they were impressed 

 that the size composition of reported catches of 

 brown and white shrimp had remained remarka- 

 bly constant within each State despite wide vari- 

 ations in weight of the annual catch from year to 

 year in response to fluctuations in recruitment. 



DESCRIPTION OF DATA 



This paper deals with combined inshore and 

 offshore reported annual catches of brown shrimp 

 and white shrimp from the Texas coast (statistical 

 areas 18-21) and Mississippi River to Texas 

 (statistical areas 13-17), representing the Texas 

 coast and that part of the Louisiana coast west of 

 the Mississippi River, respectively (Figure 1 ), and 



from 1959-76 (U.S. Fish and Wildlife Service 

 1960-69; National Marine Fisheries Service 

 1970-78). 



The annual catches reported in the Gulf Coast 

 Shrimp Data (U.S. Fish and Wildlife Service 

 1960-69; National Marine Fisheries Service 

 1970-78) represent only a portion of the total an- 

 nual catches; those landed by United States craft 

 at U.S. ports along the coast of the Gulf of Mexico. 

 Portions not reported include some of the commer- 

 cial landings (including those of foreign fishing 

 craft), undersized shrimp that are discarded, and 

 landings by domestic sport fishermen. The propor- 

 tion of the total annual catch that is not reported is 

 unknown, and we do not know what effect its in- 

 clusion would have on size composition of the an- 

 nual catch. However, we believe that the reported 

 catch represents the bulk of the total catch and 

 that the reported catch is a reasonably good reflec- 

 tion of the combined effects of shrimp population 

 characteristics (growth and natural mortality) 

 and removals by fishing (or fishing mortality). 



Size composition of the reported catches was 

 examined in units of pounds (as reported in catch 

 statistics) caught in eight "count" or size 

 categories representing number of shrimp per 

 pound, heads-off ( 5=68, 51-67, 41-50, 31-40, 26-30, 

 21-25, 15-20, and <15). These categories are ap- 

 proximately equivalent to the following number of 

 shrimp per kilogram (heads-off), respectively: 

 3=150, 112-148, 90-110, 68-88, 57-66, 46-55, 33-44, 

 and <33. The use of count (number per pound) as a 

 measure of shrimp size amounts to a reciprocal 

 transformation of the weight (W) per shrimp (in 

 pound): 



Count = 



Figure l. — Statistical areas used in reporting Gulf Coast 

 Shrimp Data for Mississippi River to Texas and Texas coast. 



w 



The same would be true if count and weight per 

 shrimp were expressed in metric units. Kutkuhn 

 (1962) described biases associated with determi- 

 nation of size composition of reported shrimp 

 catches, including those resulting from interview 

 sampling methods, from prevailing practices of 

 catch culling, grading or sorting, and from catch 

 sampling practices. Because the methods used to 

 determine size composition of catches have re- 

 mained essentially unchanged from 1959 to 1976 

 (Farley^), we believe that the biases would have 



"Orman Farley, National Marine Fisheries Service, NOAA, 

 Galveston, Tex. pers, commun. December 1978. 



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