A study of the life history of Brazilian sardine, Sardinella brasiliensis: IV. Distribution and abundance of sardine larvae

Data on distribution and abundance of larvae of the Brazilian sardine, Sardinella brasiliensis, are presented based on samples collected in waters off southern Brazil during 1969 to 1971. The distribution pattern and relative abundance of sardine larvae during three spawning seasons are discussed. Relative abundance, using regional census estimates, was calculated each year. In general, larval abundance in each subarea coincided with that of eggs, although the area of distribution of larvae was larger than the spawning area. Estimates of larval abundance showed that the 1970-71 spawning season was the poorest, both in larval and egg abundance, despite the enlarged size of the area surveyed. The average temperature at stations where sardine larvae occurred was 23.4º C, ranging from 14.6 to 27.4º C, and the average salinity was 35.6º /oo, ranging from 35.0 to 36.7º /oo. Distribution of the larvae in different depth zones was analysed. Larvae usually were most abundant in the 51-100 m depth zone. No tendency for a unidirectional transport of larvae was observed; apparently they move from the spawning ground in all possible directions, spreading over the continental shelf. An estimate of survival rate of larvae, based on length frequency data pooled from the three years, was calculated. Undersampling of larvae during daytime was observed. The mean night-day catch ratio, based on larvae from all length classes sampled, was 3.93.