376 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



efficient system of "freighting" (or transshipping), 

 wherein vessels stagger their departures to and 

 from the distant Campeche grounds, greatly 

 enhances the quality of shrimp arriving at United 

 States ports, but renders difficult the problem of 

 assigning effort and catches to individual trawlers. 

 Fortunately, most of the Campeche fleet operates 

 out of a few Florida and Texas ports where 

 statistical agents, with the full cooperation of the 

 fishing industry, have devised effort and catch 

 accounting methods so effective that statistics 

 of United States fleet operations in the Gulf of 

 Campeche may be included among the most 

 accurate of all statistics describing the Gulf 

 shrimp fishery. Such statistics, condensed from 

 more extensive tables, are given in appendix 

 tables 1 and 3. 



Commercial yield.- Aiter reaching a high of 

 about 33 million pounds in 1953, annual landings 

 of Campeche pink shrimp by United States fisher- 

 men stabilized at 24-25 million pounds over the 

 period 1954-56 (Idyfl, 1957, table 4). Thereafter 

 (1957-59), they steadily declined to a low of 13.4 

 million pounds in 1958 but then began to climb 

 again, reacliing 16.4 million pounds in 1959 and 

 about 18 million pounds in 1960. The lowest 

 annual take recorded prior to 1958 was 8-9 million 

 pounds in 1951, early in the fishery's development. 



a COMMEBCIflL riELD (millions of pounds, ri»ad»-Ool 



J\. 



A/ 



^"-"N /' 



i/V 



/"■ 



r'" 



y 



^^" 



d lo- dofnlnon' modal 

 D-a-»-w~ 



7 



Fi GUKE 25. — Yield (to United States fishermen only) and 

 structure of the pink .shrimp population off the Mexican 

 Gulf coast, Obregon-Campeche area, 1956-59. 



In contrast to seasonal catch patterns in most 

 shrimp producing areas, the 1956-59 pattern for 

 pink shrimp on the Campeche flats showed rela- 

 tively steady year-round production (fig. 25 A). 

 Greatest month-to-month variation occurred 

 durmg midwinter with the highest monthly pro- 

 duction in December and (until fall catches 

 dropped below "normal" in 1958 and 1959) the 

 lowest in January. This sharp drop is believed 

 to reflect intensification of adverse fishing condi- 

 tions rather than marked seasonal changes in 

 shrimp abundance. 



Fishable biomass. — Here, as in the case of the 

 Texas brown shrimp fishery, the definition given 

 "fishable biomass" does not hold. This is due to 

 the rather rigid restrictions concerning the sizes 

 of shrimp landed that the fishery imposes upon 

 itself. The United States fleet fishing the Cam- 

 peche pink shrimp population is, perhaps, the most 

 selective of any comparable unit operating in 

 Gulf waters. Rarely are Campeche landings com- 

 posed of a predominance of shrimp smaller than 

 19-24 heads-on count size. And only in recent 

 years has the average size landed fallen below 

 16-18 whole shrimp to the pound. The task of 

 maintaining quality control, i.e., sorting the de- 

 creasing numbers of large shrimp from increasing 

 catches of small shrimp, is reportedly becoming 

 more and more difficult. The consequence of 

 such practices is that landings are not representa- 

 tive of that portion of the population ordinarily 

 vulnerable to the gear employed, and interpreta- 

 tions given analyses of associated statistics apply 

 only to members occupying the upper size or age 

 strata. 



Involving only the population phases cona- 

 prising shrimp equivalent to 19-24 count size 

 (heads-on) and larger, a plot of monthly biomass 

 indices for the period 1956-59 yields the seasonal 

 abundance curve typical of Gulf shrimp popu- 

 lations (fig. 25B). Its amphtude of relatively 

 low order can be attributed to the fact that 

 landing statistics pertained solely to older popu- 

 lation segments, the curve itself in no way reflect- 

 ing actual status of the greater part of pink 

 shrimp aggregations occupying the grounds. 

 Thus the most useful conclusions that can be 

 drawn from figure 25B are that available quan- 

 tities of premium pink shrimp on the Campeche 

 flats reach a seasonal peak during the faU, and. 



