On-line version ISSN 0717-7178
Investig. mar. vol.30 no.1 suppl.Symp Valparaíso Aug. 2002
Changes in the Ichthyoplankton along
the Peruvian Coast during El Niño
Patricia Ayón Dejo, Katia Aronés Flores
This paper shows changes observed in the icthyoplankton composition during El Niño events and presents an association between anchoveta (Engraulis ringens) and light fish (Vinciguerria lucetia) eggs and larvae in the Peruvian upwelling ecosystem.
Under normal environmental conditions, ichthyoplankton off the Peruvian coast show a marked distribution pattern, where we can see three main groups; the first one with anchoveta distributed between 06° and 18° S within 60 miles of the coast, the second with a high richness of species without any dominance, between 03°30 and 06°00 S; and the last one located 60 miles off the coast with mesopelagic species like light fish and some lantern fish dominating.
During El Niño events this distribution is modified, showing lower abundances of anchoveta, sometimes located in the very near coastal zone, and sometimes with southward migration of this specie. During El Niño 82-83, mainly in 1982, there was also no evidence of anchoveta spawning along the Peruvian coast.
The invasion of warm waters produced by El Niño events modified the ichthyoplankton community structure along the coast. That is why, in the northern part, there are species coming from the biogeographical Panamanian province, while in the southern-centre part, mainly in the central zone, there is an increase of species from the oceanic waters, some of them with mesopelagic behaviour. There is an increase in abundance and frequency of Sardine and Jack mackerel larvae and eggs, both in the oceanic waters and in the northern part.
During El Niño 1972-1973, sardine, light fish, jack mackerel, flat fish and cutlassfish (Sandoval de Castillo, 1985) were the main species, while during El Niño 1982-1983 species including anchovy, sardine, mackerel (e.g. jack and bullet), flat fish, eels and snake mackerel were more frequent.
During El Niño 1997-1998, ichthyoplankton was composed of a high number of species such as blacksmelts, jacks, lantern fish, flatfish (Paralichthyidae), mackerel, rockfish, snake mackerel and gobies, among others (Ayon et al.1998).
Under normal conditions, abundance and spatial presence of larvae and eggs of anchoveta and light fish are negatively correlated (a = 0.01), meaning that these species represent complementary distributions. On the other hand, when we correlated these variables with sea surface temperature and salinity, it was determined that the correlation between these variables and light fish was positive (a = 0.01) while with anchoveta the correlation was negative.
However, during El Niño events there is a positive correlation between light fish eggs and ancho veta larvae, which means that both life stages occupy the same areas. At the same time, the correlation between light fish eggs and larvae and temperature is negative.
It is hypothesized that, under normal conditions, the high abundance of anchoveta restricts the spatial distribution of light fish; however, during El Niño events, the low abundance of anchoveta allows the light fish to occupy a greater area, because eggs and larvae of this species seem to be more tolerant to both temperature and salinity. In order to confirm this hypothesis more studies need to be performed