Inter-population differences in temperature effects on Engraulis ringens yolk-sac larvae

Abstract

Early life stages of Engraulis ringens were reared from hatch until yolk exhaustion. We evaluated the effect of temperature on characteristics such as larval length and yolk volume at hatch, larval length at yolk absorption, duration of yolk-sac stage, yolk consumption rate and larval growth rate. Further, we determined the potential differences in these traits between populations located 13° of latitude apart (Antofagasta 23° S, Talcahuano 36° S). The results showed that egg size had an effect on the larval length at hatch, initial yolk volume and larval length at yolk absorption, since the values obtained were always larger in larvae hatched from Talcahuano (from larger eggs) than from Antofagasta (smaller eggs). These characteristics were also modified by the rearing temperature. Duration of yolk-sac phase, yolk consumption rate and larval growth rate until yolk exhaustion showed high thermic dependence in both populations. However, these traits showed no difference between populations when larvae were reared at the same temperature in the range between 12 and 20°C, despite their initial difference in egg size. When extrapolated from the environmental conditions in each nursery area (i.e. 15°C Antofagasta and 12°C Talcahuano), our results suggest that the anchoveta populations from Talcahuano compensate for their lower larval growth rates by increasing their initial egg and hatch sizes, as they are larger than Antofagasta larvae at the end of the yolk-sac stage. This increased larval length should enhance their chances of survival under adverse environmental conditions, such as high turbulence, lower temperature and lower food availability during winter, which is typical of the anchoveta southern spawning area. © Inter-Research 2006.