Impact of oceanic upwelling on morphometric and molecular indices of an intertidal fish scartichthys viridis (Blenniidae)

Upwelling is a determinant factor for intertidal community structure on all coasts where it occurs. Most of the evidence has been obtained from sessile species or those with limited mobility and it is still unknown whether nutrients are transferred from primary producers to upper trophic levels in upwelling systems. We studied a fish species from two localities in Central Chile, Quintay, and Las Cruces, the former affected by upwelling and the latter not as evidenced by sea surface temperatures. Specimens of the herbivorous fish Scartichthys viridis, from the two sites were compared for weight-length relationships and RNA:DNA ratio in muscle tissue. The results showed that in the upwelling zone, fish increase their weight faster and have greater RNA:DNA ratios than those from the non-upwelling zone. This suggests that nutrient subsidies can alter the performance of key intertidal vertebrates such as S. viridis. The consequences of this effect on community structure and dynamics are not known.