A gastric evacuation model for three predatory gadoids and implications of using pooled field data of stomach contents to estimate food rations

The general applicability of the square root model to describe gastric evacuation in predatory gadoids independently of meal size was verified through experiments on whiting Merlangius Merlangus, saithe Pollachius virens and cod Gadus morhua fed different fish and crustacean prey. Gastric evacuation rate was related by a negative power function to energy density of fish prey,) er an extended range from 3(.)4 to 11(.)5 kJ g (1) of the effector variable. Gastric evacuation of crustacean prey seemed to depend on the characteristics of their exoskeleton, Gastric evacuation of mixed meal, composed of fish prey with different energy densities could be described as a function or the overall cncrg density. The evacuation rate of each of the prey could be described directly by their share of the stomach content. A full gastric evacuation model including predator size. temperature and prey energy density was established for whiting, saithe and cod. It was demonstrated that estimates of food rations might be severely biased by use of mean values for prey composition and total mass of stomach contents. The Fisheries Society of the British Isles