NOTE Galindo Beet et al ; Penaeid shrimp landings in the upper Gulf of California 



223 



Bureau of Reclamation, Yuma, Arizona (Wil- 

 liamsM. We assumed that this flow entered 

 the delta and the upper Gulf of California. 



Annual shrimp landings and landings 

 divided by numbers of trawlers { normal catch 

 per unit of effort, CPUE) were correlated 

 with river flow and number of trawlers. Our 

 normal CPUE was a crude approximation of 

 stock abundance or catchability. We lacked 

 actual fishing time (days, weeks, hours of net 

 deployment), size frequency of the legal ves- 

 sels, and number of small boats ( pangas ) fish- 

 ing. We made landings lag river discharge by 

 one year because the life cycle of shrimp from 

 hatching to capture is approximately one 

 year (Gracia-Pamanes^). Transformed river 

 flow (logjij) was tested for nonlinearity; then 

 we conducted a multiple regression analysis 

 to predict shrimp landings from variables that 

 were individually correlated (P<0.05) with 

 landings. 



Results 



Annual shrimp landings ranged from 701 

 metric tons (t) ( 1983-84) to 217 t ( 1992-93), 

 decreasing significantly from 1977 to 1996 

 (r=0.78, P<0.001, Fig. lA). The reported 

 number of trawlers legally fishing from San 

 Felipe ranged from a high of 59 in 1988 to a 

 low of 20 in 1995 (Fig. IB). Catch per unit of 

 effort (CPUE) increased from 1982 to 1984, 

 then markedly decreased back to the 1982-83 

 level in 1985, remaining low until 1993, after 

 which a positive trend was achieved and the 

 highest CPUE ever was recorded in 1995 

 (Fig. IC). There were substantial flows (>700 

 million cubic meters, Mm-^) in 8 of the 21 

 years from 1976 tol996 and varied over 

 10'*-fold, ranging from 1 Mm^ in 1990 and 

 1996 to 15,657 Mm'^ in 1984 (Fig. ID). High- 

 est volume occurred between 1980 and 1987 

 as a result of overflow from Lake Powell in 

 the United States (Glenn et al., 1996). The 

 flow spike in 1993 was due to releases from Painted 

 Rock Dam on the Gila River in Arizona. Periods 

 of significant river flow at the S.I.B. were closely 



z 



a! 2 



b 





l'^ 



1975 



1980 



1985 



1990 



1995 



2000 



80 



60 



40 



20 



B 



-^ 



1975 



1980 



1985 



1990 



1995 



2000 



20,000 



15,000 - 



10,000 - 



5,000 



1975 



1980 



1985 



1990 



1995 



2000 



Figure 1 



(A) Annual San Felipe shrimp landings (metric tons); (B) Number of 

 shrimp trawlers fishing annually in San Felipe; (C) CPUE (metric 

 tons/boat); (D) Colorado River freshwater discharge flow below the 

 Southerly International Border (million m-Vyrl. 



1 Williams, B. 1998. United States Bureau of Reclamation. 

 Yuma, Arizona. Personal commun. 



' Garcia-Pamanes, F. C. 1992. Biologia reproductiva y din- 

 amica poblacional del camaron azul Penaeus stylirostris en el 

 Alto Golfo de California. Instituto de Investigaciones Oceano- 

 logicas, Universidad Autonoma de Baja California, En.senada. 

 Unpubl. final report. 



matched to El Nino Southern Oscillation (ENSO) 

 events that occurred in 1983 and 1993. 



Shrimp landings were significantly (P<0.05) cor- 

 related with same year river discharge, but logj^- 

 transformed river discharge in the year prior to 

 shrimp harvest produced the highest correlation 

 coefficient (r=0.67, P<0.001) (Table 1). The number 

 of trawlers also significantly correlated with shrimp 

 landings (r=0.77, P<0.001), as expected. The best 

 correlation (r) of shrimp landings was the product 



