Feeding, growth and bioenergetics of the chain dogfish, Scyliorhinus retifer
The purpose of this study was to determine the type and amount of prey taken by chain dogfish, to examine how they utilize energy from their food, and to compare these results with those for other elasmobranchs and for teleosts. Most of this work was done with captive sharks, and the application of laboratory derived data to wild populations is discussed. ^ Growth and food consumption were monitored for captive sharks to determine the size at maturity, ration levels, food preferences, growth rate, and gross conversion efficiency. Both female and male sharks reached maturity at 280 g (40.4 cm), or 8.5 years. Juveniles consumed more squid and less fish than adults. The diet shift occurred in sharks between 150 and 200 g. Ration levels and maintenance rations were higher for juveniles than for adults. Both growth rate and ration decreased exponentially with increasing body weight. ^ To determine parameters of the bioenergetic equation, respirometry was used to measure metabolism, calorimetry was used to measure energy content of food and feces, and nutrient analysis of water was used to measure excretion. Standard metabolism was dependent on weight and was lower than that of teleosts. Active metabolism was dependent on weight and activity level, and introduced great variability into the equation. The SDA, fecal losses and excretion loss rates were similar to those found for carnivorous teleosts. All parameters of the equation represented similar proportions of ingested energy as those found for teleosts. A model was developed to allow prediction of growth at different levels of ration and activity. ^ No difference in diet was found between juveniles and adults or between different seasons for wild-caught sharks. The gastric evacuation, found by gastric lavage at intervals after a meal, was exponential for meals of fish, and followed a Gompertz curve for meals of squid. The exponential rate was used in conjunction with stomach contents of wild-caught sharks to determine the ration level of wild sharks, which was twice that of captives. It was determined that for wild-caught sharks to have a similar growth rate to captives, their activity level must be much higher. ^
Biology, Oceanography|Biology, Animal Physiology|Biology, Zoology
Kathleen Ann Duffy,
"Feeding, growth and bioenergetics of the chain dogfish, Scyliorhinus retifer"
Dissertations and Master's Theses (Campus Access).