Biologia reprodutiva do peixe-rei Odontesthes argentinensis (Valenciennes) (Atherinopsidae) da região marinha costeira do sul do Brasil Reproductive biology of silverside Odontesthes argentinensis (Valenciennes) (Atherinopsidae) of coastal sea region of the south of Brazil

O peixe-rei Odontesthes argentinensis (Valenciennes, 1835) distribui-se na região costeira do Atlântico Sul desde o sul do Brasil até a Argentina. Esta espécie apresenta duas populações, uma população residente no estuário da Lagoa dos Patos e outra na região marinha costeira. Este trabalho teve como objetivo determinar a biologia reprodutiva da população marinha costeira. A proporção sexual indicou predomínio de fêmeas. O tamanho de primeira maturação (L50) foi estimado em 13,8 cm CT para os machos e 16,1 cm CT para as fêmeas e o comprimento em que todos estão aptos para desovar (L100), foi estimado em 16,3 e 19,3 cm CT para machos e fêmeas, respectivamente. A relação gonadossomática indicou período reprodutivo entre final de agosto e início dezembro, período em que a temperatura da água se manteve abaixo dos 20ºC. Os fatores de condição total (KT) e somático (KS) apresentaram grandes variações ao longo do ciclo. Houve uma queda nos valores de K coincidindo com o início da desova estabelecendo uma relação com este período. Na análise do diâmetro dos ovócitos há evidências de três lotes caracterizando desova parcelada. A fecundidade total (FT) e por lote (FL) são proporcionais ao comprimento total. A média de ovócitos foi de 10.014 para FT e 3.651 para FL.<br>The silverside Odontesthes argentinensis (Valenciennes, 1835) is distributed in the coastal region of the South Atlantic since the south of Brazil until Argentina. This species presents two populations, a population resident in the Patos Lagoon estuary and another one in the coastal sea region. This work had as objective to determine the reproductive biology of the populations of coastal sea region. The sex ratio indicated predominance of females. The size of first maturation (L50) was estimated in 13.8 cm LT for the males and 16.1 cm LT for the females and the length where all were apt to spawn (L100) was estimated in 16.3 and 19.3cm LT for males and females, respectively. The gonadossomatic relation indicated reproductive period between ends of August and beginning of December, period where the temperature of the water is below 20ºC. The factors of total condition (KT) and somatic (KS) had presented great variations during the cycle. A fall in the values of K coincided with the beginning of the spawning, establishing a relation this fall of K represented the energy that was directed for the development of the gonads. In the analysis of the diameter of the oocytes evidence was found allowing state that the spawning don't occur at once. The total fecundity (TF) and the lot fecundity (LF) are proportional to the total length. The average of oocytes was of 10,014 for FT and 3,651 for FL

Diversificação fisiológica e morfológica de Micropogon furnieri (Desmarest, 1822) ao sul de Cabo Frio, Brasil

This paper deals with some aspects of faunistic diversification and refers to part of the distribution area of a sciaenid fish Micropogon furnieri (Desmarest, 1822) Jordan & Evermann 1884, widely distributed. Such species is characteristic of the tropical area and occurs along the Brazilian coast with highest abundance south of Cabo Frio. The analysis of variations of six meristic characters and eight body proportions and of some reproduction and growth features has shown that along the coast between latitudes 23ºS and 33ºS diversifi cation occurs within the species; such diversification implies in the existence of two populations, one occupying the area between 23ºS and 29ºS (area I) and the other between 29ºS and 33ºS (area II). The eco logical differences between the two mentioned areas according to our point of view is the reason for the species diversification in the whole area under observation. The differences recorded as the characteristics studied were suf ficient enough to illustrate the existence of two populations reproductively isolated suggesting that some gene exchange, if any, between both populations occurs in a very low rate. Our results show that abundance estimates of M. furnieri in this area must be made for each population as a whole until further studies on genetic characters are developed which may confirm the existence of gene exchange and if so, the gene flow rate. As the present study does not cover the total area of occurrence of Micropogon furnieri no hypothesis is extended to the general pattern of diversification (eventual presence of sub-species) and no systematic "status" and names are given to the populations identified