222 



Penaeid shrimp landings in the upper 

 Gulf of California in relation to 

 Colorado River freshwater discharge 



Manuel S. Galindo-Bect 



Institute de Investigaciones Oceanologicas 

 Universidad Autonoma de Baia California 

 Km 103 carretera Ti|uana-Ensenada 

 Ensenada, Baia California, Mexico 



Edward P. Glenn 



Environmental Research! Laboratory 



2601 East Airport Drive 



Tucson, Anzona 85706 



E-mail address (for E- P Glenn, contact author) eglennidag anzona edu 



Henry M. Page' 



Kevin Fitzsimmons^ 



Luis A. Galindo-Bect^ 



Jose M. Hernandez-Ayon^ 



Robert L. Petty' 



Jaqueline Garcia-Hernandez^ 



David Moore^ 



A commercial trawl fishery in the 

 upper Gulf of California provides 

 the principle source of income for 

 the coastal communities of the 

 region, but catches of estuarine- 

 dependent crustaceans and fish 

 have declined in recent years (Her- 

 nan, 1997; Cudney-Bueno and Turk- 

 Boyer, 1998). Declines in shrimp 

 landings, mainly Litopenaeus styl- 

 irostris (formerly classified as Pen- 

 aeus stylirostris ) i Perez-Farfante 

 and Kinsley, 1997 ) have been attrib- 

 uted primarily to over-exploitation 

 of the resource and to viral diseases 

 (Rosas-Cota et al., 1996; Hernan, 

 1997). 



The Biosphere Reserve of the 

 upper Gulf of California and Col- 

 orado River Delta was created in 

 1993 to address some fisheries man- 

 agement problems. A more funda- 

 mental problem, however, may be the 

 lack of river flow after construction 

 of upstream dams. Historic reduct 



tions in river discharge have caused 

 dramatic increases in salinity in the 

 estuary and changes in the distri- 

 bution of nutrients ( Alvarez-Borrego 

 et al., 1975; Hemandez-Ayon et al, 

 1993). Since 1979, occasional flood 

 releases have entered the upper Gulf 

 of California by means of the Colo- 

 rado River when upstream impound- 

 ments are filled (Glenn et al., 1996). 

 Effects of freshwater on penaeid 

 shrimp population development are 

 controversial (Garcia and Le Reste, 

 1981; Day et al., 1989), but recruit- 

 ment of spawning stocks of white 

 shrimp (Penaeus setiferus ) has been 

 positively correlated with river dis- 

 charge in the southwestern Gulf of 

 Mexico and has been attributed to 

 an expansion in estuarine nursery 

 habitat for white shrimp (Garcia, 

 1991). River discharge also can 

 stimulate the migration of sub- 

 adults from estuaries (Deben et 

 al., 1990; Vance et al., 1998). Fish- 



ermen have a strong perception 

 that shrimp and fish catches in 

 the northern Gulf of California 

 are related to freshwater discharge 

 from the Colorado River (Cudney- 

 Bueno and Turk-Boyer, 1998). To 

 evaluate their perception we con- 

 ducted a correlation analysis of 

 shrimp landings at San Felipe Baja 

 California (nearest shrimping sta- 

 tion to the delta) with freshwater 

 discharges from the Colorado River 

 to the northern Gulf of California. 



Materials and methods 



Data on annual shrimp landings and 

 number of trawlers legally fishing 

 from San Felipe were obtained ft-om 

 the Secretary of Environment, Nat- 

 ural Resources and Fish (SEMAR- 

 NAP), San Felipe, Mexico. Landings 

 were available from 1977 and 

 number of trawlers from 1982. The 

 artisanal catches by small boats 

 (pangas) or the significant illegal 

 shrimp fishery are not accounted 

 for in reported shrimp landings. 

 Annual shrimp landings serve as 

 indicators of the variability in the 

 total landings and are reported 

 for all species of shrimp, even 

 though landings are >90% L. styl- 

 irostris in San Felipe (Rosas-Cota 

 et al., 1996). Data on freshwater 

 discharge of the Colorado River 

 were from the Southerly Inter- 

 national Border (S.I.B.) gauging 

 station which is below the last 

 diversion on the river and were 

 obtained from the United States 



' Mainne Science Institute 

 University of California 

 Santa Barbara. California 93106 



- Environmental Research Laboratory 

 2601 Ea.st Airport Drive 

 Tucson, Arizona 85706 



' Institute de Investigaciones Oceanologicas 

 Universidad Autonoma de Baja California 

 Km 103 carretera Tijuana-Ensenada 

 Ensenada, Baja California, Mexico 



Manuscript accepted 2.5 August 1999. 

 Fi.sh. Bull. 98:222-22.5 (20001. 



