Feeding of a larval clinid fish in a microtidal estuary from southern Chile

摘要

The utilization of estuaries as nursery zones for fish and invertebrates is widely known, but differences in the success of resource exploitation vary between resident and opportunistic estuarine species. The distribution and diet of larval Myxodes viridis (Pisces, Clinidae) were studied at 2 locations (up-estuary and down-estuary) in the Corral Bay estuary, one of the largest estuaries in southern Chile, during the austral spring 2009 at 3 depths (surface, pycnocline, deep) during the flood and ebb of 4 tidal cycles. Larvae were collected mostly at the down-estuary station during the ebb phase. Feeding incidence was also greater during the ebb phase; larvae changed from omnivory to carnivory as they developed, predating mainly on nauplii and calanoid copepodites. Although the feeding success was similar for each developmental stage along the water column, diet of preflexion and flexion larvae was different in the first 3-4 m depth (surface and pycnocline) in relation to deeper waters (7-10 m depth, near to the bottom). This suggests that the pycnocline may affect the composition of the diet of small, larval M. viridis but not the size, number or volume of ingested prey. Additionally, because foraging is predominantly based on the different life stages of copepods, larvae emerging during the ebb tide may increase the off-estuary advection into nearby shelf waters, indicating that this species is not a user of the estuary during its early development.