THE PHYSIOLOGICAL STATUS OF ATLANTIC COD, GADUS-MORHUA, IN THE WILD AND THE LABORATORY - ESTIMATES OF GROWTH-RATES UNDER FIELD CONDITIONS

We compared the physiological status of Atlantic cod, Gadus morhua, st arved or fed at high rations with those of cod sampled in late spring (June 15) and early fall (October 3) in the Gulf of St. Lawrence. The white muscle of starved cod had lower lactate dehydrogenase activity, buffering capacity, and sarcoplasmic, myofibrillar, and total protein levels than did that of fed cod. Intestinal cytochrome C oxidase activ ity was also lower in starved than fed cod. Wild October cod had highe r condition factors, hepatosomatic indices, white muscle lactate dehyd rogenase activities, sarcoplasmic protein concentrations, and bufferin g capacities than June cod. The gonadosomatic index and myofibrillar p rotein concentrations were higher in June than October cod. The intest inal cytochrome C oxidase activity did not differ between cod captured in June and those captured in October. The growth rates predicted for the experimental cod from the established relationship between growth rate and white muscle lactate dehydrogenase activity agreed well with their actual rates. Estimation of growth rates of the wild cod sugges ts that in June the cod were losing mass (-0.18% body mass/day), where as in early October they were growing as quickly as the fed cod (0.83% body mass/day).