Taxonomical lists of different zoological groups have great value, since they constitute the basis for future zoogeographical and ecological studies. These lists are particularly important in countries of this part of the Pacific, where they are very rare. In Peru is recognized some list of mollusk and crustaceans, but none on polychaetes, which together with the aforementioned, are the most important groups of the marine ecosystem.

The characteristics of intensity, and untimely of "El Niño 1997-98" answer, manifested by superficial phytoplankton, rocky shore macroalgae, and soft bottom macrobenthos were analyzed from December 1996 to August 1998 in Ancon Bay (11 °46' LS and 77°11' LW). A significative increase of both, temperature since April (17,4°C), and oxygen (2,46 mLL-1)from May 1997 in the bottom of the study area, characterized this event. In superficial phytoplankton, the presence of indicator species of warm oceanic water, and an unusual increase of both dinoflagellate and microflagellate density at the beginning of April 1997 were recorded since January. The density of Chondracanthus chamissoi population reached 2684 ind.x32 m ' of shoreline in October 1997, and the proportion 01 gametophytes increased during 1998. The density and species number 01 soft bottom macrobenthos reached maximum values of 90...

La elaboración de listas de los diferentes grupos zoológicos posee gran valor, ya que constituyen la base para futuros estudios zoogeográficos y ecológicos. Tales listas tienen especial importancia en los países de esta parte del Pacífico, donde son muy escasas. En nuestro medio se han realizado algunos avances de este tipo con respecto a los moluscos y crustáceos, pero ninguno con respecto a poliquetos, que conjuntamente con los anteriores, constituyen los grupos más importantes del ecosistema marino.

The characteristics of intensity, and untimely of "El Niño 1997-98" answer, manifested by superficial phytoplankton, rocky shore macroalgae, and soft bottom macrobenthos were analyzed from December 1996 to August 1998 in Ancon Bay (11 °46' LS and 77°11' LW). A significative increase of both, temperature since April (17,4°C), and oxygen (2,46 mLL-1)from May 1997 in the bottom of the study area, characterized this event. In superficial phytoplankton, the presence of indicator species of warm oceanic water, and an unusual increase of both dinoflagellate and microflagellate density at the beginning of April 1997 were recorded since January. The density of Chondracanthus chamissoi population reached 2684 ind.x32 m ' of shoreline in October 1997, and the proportion 01 gametophytes increased during 1998. The density and species number 01 soft bottom macrobenthos reached maximum values of 90...