CISNEROS-MATA ET AL.: RISE AND FALL OF PACIFIC SARDINE IN GULF OF CALIF. CalCOFl Rep., Vol. 36, 1995

THE RISE AND FALL OF THE PACIFIC SARDINE, SARDlNOPS SAGAX CAfRULfUS GIRARD, IN THE , MIGUEL A. CISFROS-MATA, M. GREGORY HAh4MANN* MANUEL 0.NEVAREZ-MART~NEZ Cenao de Investigacidn Cientifica y de Instituto Nacional de la Pesca Educacidn Superior de Ensenada (CICESE) Centro Regional de Investigaciones Pesqueras (INP-CRIP) Apartado Postal 2732 Guaymas, , 85400 Km. 107 Cam. Tijuana-Ensenada Mkxico Ensenada, Baja California, 22800 Mkxico

*Address all correspondence to M. Gregory Hammann, CICESE, P.O. Box 434844, San Ysidro, CA 92143. Fax (011+526) 174-51-54.

ABSTRACT tors such as circulation patterns (Parrish et al. 1983) and The Pacific sardme has been the most important species temperature received increased emphasis in the study of in the wetfish fishery in the Gulf of California, Mexico, the causes of population variability of these pelagic fishes, for the past 20 years. In recent years, the sardine popu- whereas a dominant role of the fisheries was questioned. lation has rapidly declined while the population of the Nevertheless, fisheries exploitation cannot be dis- northern anchovy, a newcomer to the gulf, has been in- counted as a contributor to the collapses of pelagic fish- creasing. The history of the sardine fishery, and popu- eries around the world. Excess removal by fishing may lation trends from 1969 to 1990 were examined with provide available niche space for food competitors virtual population analysis (VPA) based on length fre- (MacCall 1986), and the fisheries may increase the am- quencies converted to age. Schaefer’s model was used to plitude of natural variations and drive a population to characterize catch and effort data from Guaymas, Sonora extremely low levels from which it may not recover (Mexico). A time series of population biomass estimates (Lluch-Belda et al. 1989). was constructed fi-om the results of the VPA and weight- In this paper we analyze the early increase and later at-age data. These results are discussed in light of the rel- decline in the population and fishery of the Pacific sar- ative roles that fishing pressure and competition with the dine in the Gulf of California, Mexico, and we discuss increasing population of northern anchovy may play in the possible relationship to the recent arrival and pop- the observed changes of the sardine population. ulation increase of the northern anchovy. Our objectives are to (1) show two decades of sardine population growth INTRODUCTION followed by the current decline, (2) demonstrate a den- High interannual variability in populations of small sity-dependent relationship between the adult sardine pelagic fish (e.g., anchovy and sardines) is common and offspring, and (3) propose an ecological mechanism (Csirke 1988). Beverton (1983) classified these species to explain the sardine/anchovy relationship in the Gulf of fishes as highly unpredictable, vulnerable to exploita- of California. tion, and difficult to manage. Classic examples can be found in the collapse of the Peruvian anchoveta (Engrutrlis HISTORY OF THE FISHERIES ringens) in the early 1970s (Pauly et al. 1987); the col- The sardine fishery in Mexico began during the fall lapse of the Pacific sardine (Surdinopssugux cuemletrs) dur- of the sardine fishery in California, USA, during the ing the 1950s and the subsequent increase of northern 1940s. At that time, the fishery was between Ensenada anchovy (Engrutrlis mordux) in the California Current; and Cedros Island, but during the 1950s, fishing ex- and the collapse of the Japanese sardme (Surdinopsmelunos- tended southward into Magdalena Bay (figure 1). During tictu) population during the 1940s and its recovery dur- the late 1960s Pacific landings of sardine decreased, and ing the 1970s (Kondo 1980). fishmeal plants and canneries were installed in Guaymas With the d