Luis Alonso Zapata Padilla

National Institute of Fisheries and Aquaculture -INPA-
P. O. Box 10742. Buenaventura, Colombia,
E-mail: luchozapata2000@yahoo.com

In spite of the knowledge about "the Niño EN and the Niña LN" on the Eastern Tropical Pacific fisheries it is still unclear what effects these events have on the Colombian Pacific fisheries. Consequently, the aim of this study was to determine the environmental influence of this climate phenomenon on the fisheries, especially during the last decade.

Between 1991-1992 and 1997-1998 the surface temperature showed average ranges between 29.4 and 30.5 ¥C with marked positive anomalies of +2 ¥C (Zapata et al. 1999), compared to a maximum temperature of 31.5 ¥C reported during Niño 1982-1983 (Balguerias and Rodriguez 1983). Salinity ranged between 28.5 and 33psu, increasing the mixed layer and the depth of the thermocline. During the Niña the temperature values averaged around 26 ¥C, with anomalies of -1.5 ¥C, and salinities between 28.3 and 32.7psu. Dring this event there was a reduction of the mixed layer depth and a shallower thermocline. The most dramatic effect during this period was the significant oxygen reduction in the subsurface layer with direct effects on the fisheries resource.

The first reports of EN effects on Colombian fisheries date from 1983, especially for the abundance of shallow shrimp populations in the southern portion of the Pacific coast of Tumaco area, reported for the specie Xiphopenaeus riveti, locally named as Titi. During this period the rains magnified the river flows and increased nutrient concentration, and this behaviour was correlated with higher catches between September 1982 and a maximum in March 1983. Similar results were observed in deep shrimp populations of Penaeus californiensis (brown shrimp), P. brevirostris (red shrimp) and Solenocera agassizi (Coliflor shrimp) with higher catches during March, April and May 1983 (Mora et al. 1983).

The behaviour of the small pelagic fish Cetengraulis mysticetus (Carduma), showed a distribution close to the shore line, increasing the diversity of bycatch and presenting a small deep migration. This population showed a correlation with partition spawning after positive or negative temperature anomalies, in a specie considered as a total spawner. Opisthonema sp. (plumuda), also showed a higher vertical distribution and a significant migration toward the northern coast which experienced higher salinities during EN.

The seasonality of the catches for Dolphin fish stock Coryphaena hippurus in the Panama Bight showed the highest catches during the first three months of the year, which was correlated with changes in distribution (migration) and spawning activity (Zapata 1993). During the occurrence of the EN event the specie migrated south and was more available in northern Peru, where its local name is Perico (Lasso & Zapata 1999). In contrast, during LN this resource disappeared totally, apparently in the absence of its normal migratory route.

This study concludes that both climate events have direct effects on the behaviour and catches of the main Colombian fisheries resources. Likewise, LN event may have a strong effect on metabolic features of the populations, especially due to a significant decrease in temperature, and similarly the oxygen levels apparently have direct consequences for the distribution and abundance of these resources. As a result, 1999 represents the year with the minimum landings in the area.