| 英文摘要 |
The jumbo (or Humboldt) squid, Dosidicus gigas, is a large pelagic ommastrephid squid which distributed in the Eastern Pacific Ocean. The jumbo squid is the target species of squid fishing and is an important component of its ecosystem in the EPO. The central challenge for fisheries ecology is to understand the abundance variations of resources under fishing pressure, and its synergistic effects to the ecosystems. The stock assessment from historical data could serve as useful information in tracking the abundance variation in studies stock. The characteristic of life history of squid makes the application of traditional stock assessment models difficult. In this study, we applied a deletion model to the Taiwanese squid jigging fishery data to estimate the abundance of jumbo squid in the EPO during 2002-2009. The biological data sampled from precious study was used to convert catch in weigh to catch in number. Effects of using different residual assumptions and natural mortality (M) were evaluated in fitting the depletion model. Based on sensitivity analyses, the log-normal residual model was found to be preferred for the squid assessment. The assessment results indicated that the annual initial population abundance ranged from 4.02 to 20.56 million squid with M = 0.03 during 2002-2009. The proportional escapement (M = 0.03) ranged from 9.5% (in 2002) to 61.7% (in 2009), with an average of 43.2% during 2002-2009. The estimated proportional escapement is higher than suggested management target of 40%, which suggest that the jumbo squid stock exploited by Taiwanese squid jigging vessel can be considered to be sustainable. This study suggests that the application of the depletion model to estimate squid stock is available. However, the reality of assumptions made in modelling and effects of selection of values for demographic parameters on assessment results should be considered deliberately during application of stock assessment. |
