A generalized stock production model

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Food conversion efficiency and the von Bertalanffy growth function. Part II and conclusion: Extension of the new model to the generalized von Bertalanffy growth function

The simple model relating food conversion efficiency (K sub(1)) to body weight derived from the theoretical concepts behind von Bertalanffy's growth model, is extended here in the context of Pauly's generalization of that model. The exponent, which was fixed to 1/3 in the simple model, is in the extended model equivalent to 1-d, with d being the weight exponent of the anabolism term in Pauly's growth model. This makes the model applicable to fish for which the assumptions of the original (special) version of von Bertalanffy's growth model are violated.

A rapid procedure for the approximation of bacterial load in fishery products

The production of colour by homogenised fish material in a simplified sugar medium containing and acid indicator has been made use of for the rapid approximation of bacterial load in such products. The medium thus developed contains poptone, tryptone, yeast extract, sodium chloride and beef extract besides dextrose. The time of colour production is influenced to some extent by the level of sodium chloride in the medium and is almost always inversely proportional to the bacterial load in the homogenate.

Factors influencing colour production from the sugar medium used for the rapid approximation of bacterial counts in fishery products

Results of the studies carried out to elucidate the factors influencing colour production from the sugar medium used for the rapid approximation of bacterial counts in fishery products are reported. The effect of particle size, trace elements, salt soluble protein and non-protein fractions, rate of multiplication of bacteria, in the medium, surface bacteria and the rate of colour production by individual strains of bacteria were studied. It is observed that the best results are obtained when a sea-water homogenate is used.

On the response of Catla catla (Ham) and Cirrhinus mrigala (Ham) to the voltage gradient of electrical field

The threshold body voltage (voltage gradient between head and tail) required for first reaction, electro-taxis and electro-narcosis depended upon species, conductivity of the fish body, nature of current and wave shape. Larger fishes showed first reaction at a lower body voltage than smaller ones. All the three reactions were dependent on the accommodation of nerves to the electrical field and subsequent fatigue of the fishes. No significant change was observed in the period of narcosis and recovery after repeated stimulation.