Condition of Atlantic cod Gadus morhua larvae after the transition to exogenous feeding: morphometries, buoyancy and predator avoidance

Abstract

The condition of Atlantic cod Gadus morhua L. larvae reared in densities of 0, 2 , 5 and 10 zooplankton ml-l was examined after the transition to exogenous feeding. Fulton's K (weight/length3) was not correlated with prey density in which larvae were reared, indicating that this index of condition is inappropriate for larvae immediately after yolk sac absorption. Fulton's K was also not positively correlated with the ability to avoid a simulated predator. However, predation avoidance was positively correlated with higher prey density. A second measure of condition, body height standardized for length, appeared to be a more sensitive indicator of condition but also did not correlate with the ability of larvae to avoid predation. The results of a buoyancy experiment indicated that poorly fed larvae may occur higher in the water column, and thus may be more vulnerable to predation or cause a sampling bias in ichthyoplankton studies.