Spawning, daily egg production, and spawning stock biomass estimation for common sardine (Strangomera bentincki) and anchovy (Engraulis ringens) off central southern Chile in 2002

In this paper, the first daily egg production method (DEPM) parameters were estimated for anchovy and common sardine stocks distributed in the central-south area off Chile (33–40°S). The study area was stratified according to the topography, shape and orientation of the coastal line, and the survey was carried out on the continental shelf during the main spawning peak (August–September, 2002). The bulk of the spawning of both species was successfully covered, which was characterized by a coastal distribution within the first 20 nautical miles, and following the inner zone associated with the 100m bottom depth. The coastal distribution of the spawning can be related to the oceanographic conditions occurring during the transition from winter to spring (southern Hemisphere), which are characterized by the alternation between northerly and southerly winds. Probably, these factors are interacting to produce enrichment, concentration and retention of egg in coastal zones in the study area. The daily egg production rate (P0) was estimated for two geographic strata, and was different in each region. Also, the length frequency and adult reproductive parameters were different between geographic strata, specially the daily spawning fraction. For anchovy, the P0 was lower in comparison with available estimates for the same species in Peru and in the north area off Chile. Also, the relative fecundity of anchovy was lower, probably because anchovy in the study area have bigger eggs as compared with the anchovy in Northern Chile. The DEPM parameters estimated for common sardine in the investigated area were similar to the range of existing values for the Engraulis genus in other upwelling areas. The stratified spawning stock biomass estimate was 133,031t (CV=44%) for anchovy and 706,792t (CV=68%) for common sardine. Probably, daily egg production and adult reproductive parameters of both species are highly variables and further research is suggested for improvements future DEPM application for the species.