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ABSTRACT. A retrospeciive anaiysis oi zooplankton volumes (1951 to 1996) was performed for the area between Punta Baja (30°N) and Punta Abreojos (26 ?ON) in relatlon to the warming anomaly that has taken place in the California Current System during the last 2 decades. The seasonal cycle of median standing stock of zooplankton In this area showed a moderate alternation between h~g h values from June to October (median monthly volumes between 86 and 108 m1/1000 m") and low values from Kovember to May (58 to 77 m1/1000 m3). The quarterly long-term means of zooplankton volumes were the lowest in winter, as were wind speeds. The standard deviations associated with the long-term means indicated interannual variability was higher than seasonal variability. The time series showed an interval of high zooplankton volume between 1952 and 1957. Following the strong ENSO (El Nifio Southern Oscillation) of 1957-1958, a period of low values occurred which extended into the early 1960s. There was a slow recovery of zooplankton biomass through the rest of the 1960s, but it did not reach the earlier high values. Available data suggest the increasing trend reached a peak in 1975. Subsequently, from 1976 to the ENSO of 1982ENSO of -1983, the biomass decreased. For the remainder of the 1980s, the few existing data showed an erratic behavior of the biomass. In the 1990s, there has been a decrease to values even lower than those observed durlng the 1957-1958 ENSO. Nonseasonal anomalles for zoop1.ankton and environmental variables were significantly different (p < 0.001) anlong decades but not between the northern (30" to 28" N ) and southern (28" to 26" N ) areas. The decrease in zooplankton volume in this region over the last 2 decades is less than that reported for the Southern California Bight. This may be partly caused by seasonal northward movements of tropical zooplankton species along the Baja California coast, Mexico.

Surplus production models were used to assess the fishery condition of red seaweed Gelidium robustum off the west coast of the Baja California Peninsula from 1985 to 1997. The maximum sustainable yield and optimum effort estimated by the Schaefer model were 705 tn and 457 teams, while the Fox model estimated 670 tn and 510 teams. The determination coefficients were r2=0·62 for the Fox and r2=0·58 for the Schaefer model. These results suggest that the resource is not overexploited. Fitting the data to Hilborn & Walters' dynamic model was not satisfactory.

Annual von Bertalanffy growth parameters of the Caribbean spiny lobster (Panulirus argus) in Cuban waters were estimated from a long term study (40 years) by length-based methods ELEFAN and the new version of SLCA. Data of around 800 000 lobsters (with carapace length ranging 14 to 199mm) were randomly sampled in artificial shelters (a non selective fishing gear very common in the lobster fishery), through the field monitory program established for this species since 1963 in 14 localities of southwestern Cuban shelf. The software ELEFAN showed problems to converge in an optimal combination of the instantaneous growth coefficient (K) and the asymptotic length (L ∞) of the von Bertalanffy equation, whereas the new SLCA software produced value estimates of K between 0.20 and 0.27 year-1 and values of L ∞ between 177 and 190 mm carapace length, all within the range reported in the literature. The standardized anomalies of both parameters showed the presence of cycles along the analyzed time series. Decadal variability in growth parameters was revealed through the spectral analysis indicating cycles of 16 and 20 years for K and of 16 years for L ∞. The incidence of some factors such as biomass and temperature that modulate growth in this crustacean was explored, using a nonlinear multiple regression model. These combined factors explained 33% and 69% of the variability of K and L ∞ respectively. The growth coefficient appeared to be maximum with annual mean sea surface temperature of 28.1º C and the largest L ∞ is reached at a annual men biomass level of 23 000 t. These results should be the basis to understand the Cuban lobster population dynamics.

Interannual changes in the reproductive pattern of the brown shrimp, Farfantepenaeus californiensis, a commercially important marine crustacean, were analysed as a function of sea water temperature. Daily samples of gravid females from 1979 through 1994 and monthly sea water temperatures were examined. The results show a high interannual variability of the reproductive period with two patterns; one in which spawning occurs throughout the year, the other with two peaks of mass spawning. The rst of the two peaks is the more intense, occurring from March to May; the other is in October and November and is less intense. The extended spawning period occurs under warmer conditions and is probably associated with El Niño events. The pattern with two peaks is associated with average sea water temperatures. Occurrence of one pattern or the other may have signi cant consequences for managing this shery. RESUMENLos cambios interanuales en el patrón reproductivo del camarón café Farfantepenaeus californiensis, un crustáceo escencialmente marino, fueron analizados en función de la temperatura del agua de mar. Se analizaron muestreos diarios de hembras ovígeras y temperatura promedio mensual del agua de mar desde 1979 a 1994. Los resultados muestran, una alta variabilidad interanual del periodo reproductivo con dos patrones: uno en el que el desove se efectua a todo lo largo del año 6 / To whom all correspondence should be sent. Fax