博士 / 國立臺灣大學 / 海洋研究所 / 99 / Spiny lobsters are highly prized species for the small-scale fisheries in the coastal waters of Taiwan, however the information of the fisheries and the status of stocks are limited and unclear in the past. According to these concerns, the objective of this study is to develop a simulation testing and stock assessment framework for spiny lobster fisheries in Taiwan using the pronghorn spiny lobster (Panulirus peniciliatus) in the waters of eastern coast off Taiwan (Taitung) as an example. Because growth is one of the most important life history processes to study the population dynamics, I widely review the current approaches for modelling the growth of the crustaceans. A comparative study by adapting various methods were applied to different taxa of crustaceans.
Lobsters’ fishery assessments are often subject to large uncertainty in input data and natural variability in life history, I evaluated the natural mortality of P.peniciliatus and used a Monte Carlo approach to incorporate life history parameters’ uncertainty into the estimation of the biological reference points (BRPs). The commonly used BRPs derived from the per recruit model (F0.1 and F40%) was suggested to be influenced by uncertainties associated with lobster life history and fishery parameters. A large uncertainty in the current fishing mortality rate and estimates of BRPs increased the uncertainty in determining the risk of overexploitation.
To mimic the complex life history and fishing processes for P.peniciliatus, I further developed an individual-based model (IBM). The developed IBM was used to perform stock assessment, as the model was fitted to the catch and length-frequency of data collected from whole seller. The results indicated that the current spawning stock biomass remains at 23 % of its unfished level (SSB0). Decision analysis based on samples from a Bayesian posterior distribution indicated that there is a negligible risk of the stock dropping below 40% of SSB0 if fishing intensity remains at the current level. However, there is a high risk of overexploitation based on the reference level of 20% of SSB0. Using the developed IBM, I also examined the possible role of various key variable/parameters in characterizing the lobster population dynamics and lobster fishery. The result suggested that the size regulation is more effective compared to other technical measures.
To include the environmental change into the population dynamics model, I applied the proposed IBM to evaluate potential impacts of increased ocean temperature on the estimation of mortality-based BRPs for fisheries management. A warming temperature would increase the stock productivity and consequently reduce the risk of overexploitation. However, there is likely a high risk of overexploitation in the long term if higher temperatures induce extra-high natural mortality. The evaluation of effectiveness of size regulations suggests that increasing minimum legal size is proposed as a good candidate measure to reduce the risk of overexploitation for pessimistically unfavorable environmental conditions. Finally, I recommended that using IBM to perform stock assessment in the current data-limited stage. An explicit incorporation of the relationships between environmental variables and biological processes can greatly improve the accuracy of stock assessment.
| Identifer | oai:union.ndltd.org:TW/099NTU05279038 |
| Date | January 2011 |
| Creators | Yi-Jay Chang, 張以杰 |
| Contributors | 孫志陸 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 226 |
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