| Summary: | 碩士 === 國立中山大學 === 海洋生物研究所 === 93 === Several species of fishes have been used for cage culture in Taiwan, including cobia, brown croaker, red drum, grouper, red seabream, emperor and snapper. Roughly speaking, the main factors determining the choice of the target species are mainly the selling price deleting the production cost. Different species have different biological characteristics that affect the economical performance. Included were specific growth rates, death or survival within cultural period, and efficiency in food conversion, etc..
By employing and modified the so-called Biomass model used in fishery biology (Kings, 1995), this research integrates the above factors into one single spreadsheet for each individual species, allowing for systematic observation of the continuous change in level of production (in terms of biomass). Through the culturing period, degrade in number was gradually offset by the gain in averaged body weights until a maximum value is reached before going downhill. This gives rise to the optimal solution of yield with the respective culturing period thus required. The results for different species were further compared in terms of expected investment and return by the end of the production. Results from this study showed that cobia has more advantage (in terms of biomass, biovalue and return on investment) than others as the prior choice under the current situation.
Basic information for this study included the value of natural mortality, length-and-weigh relationship and the growth equation of the target species. The system was programmed under the EXCEL-Spreadsheet system of the Microsoft Inc. In the future other species of fishes may also be tested as possible candidates for cage culture. The program could also expected to serve as an auxiliary tool in education and fishery extension services.
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