| 英文摘要 |
This project include two parts: (I) the cetacean survey on the coastal waters of Taiwan, (II) the ecology of Chinese white dolphins. For the first part, we have collected 32 data sets from the past reference or unpublished works. In total, there are 1907 sightings of 23 cetacean species recorded in the past, and their spatial distributions were mapped. The species composition was quite different between the east and west coastal waters. The species diversity as well as the sighting per unit of effort was the highest for the cetaceans off Hualien. We executed 11 line transect surveys (10 effective surveys) at the coastal waters of Ilan during July to September 2007. In total, we covered 888.4 km with 683.7km on effort. The sighting probability is 80% of cruises, and SPUE is 2.9 groups/100km. We found 20 groups of 6 species, Stenella longirostris , Pseudorca crasidens, Tursiops truncates, Stenella attenuata, Feresa attenuata and Kogia sp. The dominant species was Stenella longirostris. The cetacean density was 5.4groups/100km at northern waters, and was significantly higher than 1.0 groups/100km of the southern waters.
????The survey of Chinese white dolphin (Sousa chinensis) selected the populations waters off Taichung and Yu-Chia as study area. Our methods include boat survey, and fishermen interviewing and reporting. Twenty-five fixed line surveys were executed during July to October 2007, with 20 effective ones, and covered 632 nautical miles with 125 hour on effort. We had 27 sightings on 14 surveys. The probability of sighting was 70% cruises. The dolphin densities were 0.26!O0.07 and 0.07!O0.03 individuals per nautical mile. We recorded 92 individual counts, the average group size was 3.4!O0.39 (SE) (range 1-8). We identified 45 different individuals (36 in the Taichung population and 9 in the Yu-Chia population) and found no overlap between them. The population size of Taichung waters was estimated as 36-99 dolphins, but it requests more data from other water area before estimation can be done. The age structure include all 6 stages, and matured ones occupied 44%. Two newborn calves were sighted at Taiching waters and make Taichung another potential breeding ground besides Yu-Chia where was claimed last year. According to the long tracking of 4 groups, we found two moving paths at Yu-Chia, and Taichung seperately, and confirm they can cross over the deeper waters of Taichung harbor with depth of 20-25 meters.
In the aspect of Fishery impact, 16% fishermen of 40 questionnair replied that they had heard of bycatch of Chinese white dolphins, and we found 11% of the photo identified individuals with wounds on their trunk or back, which seems related with fishing gear. This potential impact calls for further attention and resear |
