674 



Abstract— Two commercial shrimp spe- 

 cies {Penaeus californiensis and P. styl- 

 irostris) were sampled along the Gulf 

 of California and crude extracts were 

 assayed electrophoretically to assess all- 

 ozyme variation and population gen- 

 etic structure. Penaeus califoniiensis, a 

 more oceanic species, displayed a V2.5'?i 

 polymorphism (Pg.) and a 0.023-0.037 

 expected heterozygosity {HJ in three 

 sampled populations, whereas P. styl- 

 irostris, a more coastal species, showed 

 a north-south clinelike pattern in its 

 genetic variability parameters: P^r^ from 

 15.63% to 31.25% and H, from 0.038 

 to 0.086. Differences between species in 

 levels of genetic variation and genotype 

 distribution may be related to differ- 

 ences in habitat during important life 

 cycles stages which reflect the remark- 

 able changes of environmental condi- 

 tions of coastal lagoons in the Gulf 

 of California. Penaeus stylirostris sub- 

 populations appeared more structured 

 (Fj,=0.372) than those of P. californi- 

 ensis {F^,=0.182). A number of private 

 alleles and alternation of the most 

 common allele in several loci account for 

 the outstanding high results of both spe- 

 cies. Nei's genetic similarities were com- 

 puted within species tP californiensis 

 subpopulations, 7=0.988-0.997; P. styl- 

 irostris subpopulations, 7=0.929-0.954) 

 and between species iP californiensis x 

 7^ stylirostris, 7=0.674). A dendrogram 

 generated from Nei's genetic similari- 

 ties segregated the upper Gulf popula- 

 tions of both species from the other two 

 populations (middle Gulf and mouth of 

 the Gulf). This segregation may be the 

 result of the "Island Barrier" hypothe- 

 sized as segregating other decapods 

 inhabiting the Gulf of California. 



Genetic structure of two commercial penaeids 

 (Penaeus californiensis and P. stylirostris) 

 from the Gulf of California, 

 as revealed by ailozyme variation 



Jorge de la Rosa-Velez 



Facultad de Ciencias Mannas 

 Universidad Autdnoma de Baia California 

 Km. 106 carretera Ti|uana-Ensenada 

 Ensenada, Baia Calllornia 22800, Mexico 

 E mail address, idrosambahiaensuabcmx 



Roberto Escobar-Fernandez 



Francisco Correa 



Institute de Investigaciones Oceanologicas 

 Universidad Autdnoma de Baia California 

 Km. 106 carretera Ti|uana-Ensenada, 

 Ensenada, Baja California 22800, Mexico 



Mercedes Maqueda-Cornejo 



Javier de ia Torre-Cueto 



Facultad de Ciencias Marinas 

 Universidad Autdnoma de Baia California 

 Km 106 carretera Ti|uana-Ensenada 

 Ensenada, Baia California 22800, Mexico 



Manuscript accepted 12 July 2000. 

 Fish. Bull. 98:674-683 (2000). 



Penaeid shrimp fisheries and hatcheries 

 have undergone an accelerated devel- 

 opment during the past three decades 

 (Rosenberry, 1996). Yields of such pro- 

 ductive activities are highly appreci- 

 ated worldwide and have resulted in 

 the economic development of prawn 

 farming in several eastern (e.g. Thai- 

 land, Indonesia, Vietnam, China, India, 

 etc.) and Latin American (e.g. Ecuador, 

 Mexico, Colombia. Peru, Panama, etc. ) 

 countries. 



Business based on penaeid shrimp 

 trading may be considered as having 

 two components: 1 ) heavy producers, 

 countries, such as those mentioned 

 above, which are mainly exporters, and 

 2) heavy importers, countries such as 

 those of Europe and the United States 

 of America, where the consumption of 

 imported shrimp has long exceeded 

 landings from their domestic fisheries 

 (Lightner et al., 1997). Moreover, in 

 the way of production (fishing on wild 



populations vs. rearing in hatcheries), 

 three kinds of producer countries can 

 be recognized: 1) countries that base 

 their shrimp production mainly on their 

 fishery yields (for example, the United 

 States, where farmed shrimps make 

 up only 1% of its production); 2) coun- 

 tries that have focused their shrimp 

 production efforts almost exclusively 

 on hatcheries (for example. Ecuador, 

 where farmed shrimps make up 9.5'^f 

 of its shrimp production); and 3) coun- 

 tries that produce shrimps in similar 

 percentages from both wild stocks and 

 hatcheries (for example. Mexico. China, 

 India, and Indonesia) (Lightner et a!., 

 1997). 



Shrimp-producing countries, no matter 

 their main way of production, need in- 

 creasingly to take into account the 

 resource's genetic structure and the 

 variability of fisheries or hatcheries 

 management (Allendorf et al., 1987). 

 Two key questions must be outlined 



