Monthly random samplings (n = 25) were taken from May 1995 to April 1996 in Matarani port, Arequipa (10°59'40" South and 72° 06'13" West). They were shown to be gonochoric and to have sexual dimorphism (the male has an arm for copulation). The sex proportion was 2,1:1,0 (male: female); eight stages of the oocyte development were also found during oogenesis. According to their reproductive behavior, the following maturity gonadic scale was established: a) undifferentiated, b) immature, c) maturation beginning, d) developing, e) mature, f) copula, g) postcopula, autofecundation and evacuation, h) postevacuation. Mature females were preferentially found in spring and summer; mature males at the end of the spring and summer; copulation occurred during summer; autofecundation and evacuationof the eggs were evident in August (50%), October (50%), November (71,4%), December (33%) and January ...

The El Niño 1992-93 phenomena incremented the number of matures males and females, and induced the spawning of Tagelus dombeii, due to the rise of the sea water temperature. The sex proportion was 1.2:1.0, (female:male). In the accelerated gametogenesis, we differentiated : oogonias and oocytes (previtelogenesis), ovocytes I (primary vitelogenesis) and ovocytes II (secondary vitelogenesis). The maturity scale, with high percentage of matures specimens and in spawning, and scarce immaturity and in development, were classificated in : non differentiated, immaturity, mature and spawn.

Monthly random samplings (n = 25) were taken from May 1995 to April 1996 in Matarani port, Arequipa (10°59'40" South and 72° 06'13" West). They were shown to be gonochoric and to have sexual dimorphism (the male has an arm for copulation). The sex proportion was 2,1:1,0 (male: female); eight stages of the oocyte development were also found during oogenesis. According to their reproductive behavior, the following maturity gonadic scale was established: a) undifferentiated, b) immature, c) maturation beginning, d) developing, e) mature, f) copula, g) postcopula, autofecundation and evacuation, h) postevacuation. Mature females were preferentially found in spring and summer; mature males at the end of the spring and summer; copulation occurred during summer; autofecundation and evacuationof the eggs were evident in August (50%), October (50%), November (71,4%), December (33%) and January ...

El fenómeno El Niño 1992-93, indujo un incremento en la cantidad de ejemplares maduros y en desove de gametos de Tagelus dombeii, debido al aumento de la temperatura superficial del mar. La proporción de sexos fue de 1,2:1,0 a favor de las hembras. En la gametogénesis acelerada, sediferenció: ovogonias y ovocitos (en previtelogénesis) ovocitos I (en vitelogénesis primario) y ovocitos II (en vitelogénesis secundario). La escala de madurez gonadal, con altos porcentajes de ejemplares maduros y en desove ve, y pocos inmaduros y en desarrollo, se clasificó en: Indiferenciados, inmaduros, en desarrollo, maduros y desovados.

6 p.