Use of inshore benthic cages for storage and on-growing of adult lobsters Homarus americanus

Wang, Guoqiang (2014) Use of inshore benthic cages for storage and on-growing of adult lobsters Homarus americanus. Masters thesis, Memorial University of Newfoundland.

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Abstract

The goals of this research project were to determine if it is feasible to hold adult lobsters Homarus americanus in inshore benthic cages for extended periods. The underlying premise is that they would survive and grow. This larger product could then be sold outside of the regular season for a higher price. In the first experimental chapter, I investigated the use of the serum protein concentration (determined from the refractive index) as an indicator of the quality and physiological condition of adult lobsters. Serum protein concentration increased linearly with hepatopancreas mass, heart mass and edible meat content. There was a concomitant decrease in serum protein concentration with increasing moisture content of the hepatopancreas and muscle tissue. The serum protein concentration also changed over the molt cycle reaching its highest levels in the premolt stage followed by a sharp drop after the lobsters had molted. This rapid and non-invasive method is a valuable tool for determining quality and physiological status of commercially important decapod crustaceans. In the second series of experiments, I recorded the survival, molting, growth rates and serum protein concentrations in cage-held adult lobsters over a six month period. Laboratory experiments allowed parameters, such as water temperature, feed type, feeding frequency and cage size, to be manipulated to determine optimal conditions for survival and growth, while field experiments tested the feasibility of the storage and on-growing protocol. Temperature had a significant effect on molting rates, with a greater percentage of lobsters molting at higher temperatures. Feeding frequency influenced growth rates of both molted and non-molted animals. Animals with limited access to food had lower serum protein concentrations and were of poorer quality. This project showed that benthic cages provide a viable method to store lobsters for up to six months allowing harvesters to sell them locally, outside the regular season.

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