Sardine and anchovy spawning as related to temperature and upwelling in the California current system

Abstract

Sardine and anchovy spawning was analyzed regarding its relation to sea-surface temperature and upwelling, using CalCOFI cruise data and Bakun's upwelling indices. Previous reports of temperature ranges for sardine and anchovy spawning have not taken into account the distribution of SST and have mostly referenced the cooler spawning area of the species. By obtaining the proportion of positive stations to total sampled stations for each tenth of a degree Celsius in the SST distribution, we were able to discriminate the ranges of preferred temperatures of spawning for both species. Sardines spawn in a much wider temperature range (13-25°C) than anchovy (11.516.5C). Two maxima of spawning occur in the California Current: at 15°C and 23°C. An additional peak is present in the Gulf of California at about 19°C. Only one maximum is evident for anchovy spawning, at about 14°C. The distribution of spawning as a function of upwelling was also analyzed for both species. There is a maximum for sardines at intermediate values of upwelling. There are two maxima for anchovy: a minor one at low levels of upwelling and a major one at the maximum values of upwelling. We conclude that sardines are eurythermic as compared to anchovies, but spawn only at intermediate values of upwelling, whereas anchovies are stenothermic but spawn at much wider ranges of upwelling, particularly at low and high values. The differences suggest exclusive competition, but more detailed analyses are needed. RESUMEN Se analiz6 el desove de sardina y anchoveta con respecto a su relaci6n con la temperatura superficial del mar y las surgencias, utilizando 10s datos de 10s cruceros CalCOFI y 10s indices de surgencia desarrollados por Bakun. Los intervalos de temperaturas de desove de sardina y anchoveta que se habian sefialado anterior