博士 / 國立臺灣大學 / 海洋研究所 / 100 / Five years (2006–2010) fishery data coupled with multi-sensor satellite images was examined to determine the habitat characterization for Pacific saury (Cololabis saira) in the northwestern Pacific Ocean (NWP). Results showed that monthly average CPUEs (metric tons/boat/day) ranged from 10.8 in early fishing season (June to August) to 23.1 in October. The overall average CPUE was 15.3. The major fishing grounds located within 37–48oN latitude and 145–165oE longitude with a remarkable latitudinal movement of the monthly mean centers of gravities.
Pacific saury’s habitat preferences in the Taiwanese fishing grounds were determined using the empirical cumulative distribution function. The high CPUEs corresponded to areas where sea surface temperature (SST) ranged from 14–16 oC, Chlorophyll-a (Chl-a) concentrations ranged from 0.4–0.6 mg m-3 and net primary productions (NPP) ranged from 600–800 mg C m-2 day-1. Local areas within the NWP with these similar satellite-derived oceanographic parameters were assumed to be the potential habitat zones of Pacific saury.
Satellite SST data also were used to extract fronts in Pacific saury fishing grounds. The fronts were identified by the Cayula-Cornillon edge detection algorithm. The results show that low frequency of SST fronts is associated with lower saury’s CPUEs during the early fishing season (June to August). Conversely, high frequency of SST fronts is associated with higher saury’s CPUEs during the peak fishing season. Additionally, if the fishing locations of Pacific saury are close to the SST fronts, higher saury’s CPUEs are observed.
The spatial non-stationary geographically weighted regression (GWR), a local modeling technique, was applied to examine the influence of oceanographic variability on the distribution of Pacific saury. The results of the GWR were compared with those of a generalized additive model (GAM). Results indicated that the distribution of Pacific saury is positively related to SST and Chl-a, and the GWR models explained more variability than the GAMs.
Based on the SST preferences in concert with the corresponding fish distributions, monthly potential saury habitats were predicted. Possible changes in potential saury habitats were estimated under 4 scenarios: the present years and with 1, 2, and 4 °C rises in SST due to climate change. Results revealed an obvious poleward shift of potential saury habitats during the influence of increases in SSTs. The southernmost boundary of potential saury habitat located at 40.24°N latitude at the present time shifted to 46.15°N latitude under the scenario of a 4 °C rise in SSTs.
In summary, the results obtained from this study improve our understanding of the variability in the spatial distribution of saury habitats, and could form the basis for fishery management and fishing forecasts.
| Identifer | oai:union.ndltd.org:TW/100NTU05279028 |
| Date | January 2012 |
| Creators | Chen-Te Tseng, 曾振德 |
| 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 | 141 |
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