| 英文摘要 |
In February, 2008, massive marine fishes were killed due to the passage of cold front at northern Penghu Island. The bodies of dead fish spread out on coastlines and beaches of many islets and the incidence became the most serious event in Penghu over the last few decades. The satellite-derived sea surface temperature (SST) data in the winters of 1996-2009 were used to examine the exceptional intrusion of China Coastal Current into the Taiwan Strait. The monthly SST differences in January and February 2008 were about 5°C higher and 7°C lower than those of the 12-year average, respectively. The satellite data showed that the China Coastal Current intruded from the north of Chang-Yuen Ridge into the waters surrounding the Peng-Hu Islands, while wind speed of more than 6.7 m/s was lasting for 30 days in the same period.?
We set a referring point at the central of PHI to calculate the distance between the referring point and 20oC isobath and to compare with the day of strong wind. It is clear to see that the longer time of strong wind blowing, the shorter distance between 20oC isobath to PHI. As the 12-year data shows, it is suggested that the strong wind blew for 13 days with the distance of of 20oC isobath could be the significant indicators of cold water intrusion. Although it is quite simple and rough to be as a forecasting method, the modeling simulation with high spatial resolution can be a better way to establish more scientific method.
In order to understand the effects of continuous cold current on fishery resource and ecological environment of Penghu, we chose five sampling areas to investigate the biota from March to June at the same year. This year, the investigation was made in the same sampling areas which were Wukan in Magong, Longmen in Husi, Houliao in Baisha, Hejie in Siyu, and Jibei. From March to June, we found 4 divisions, 36 families, and 83 species in algae. Among them, 57 species were found in Wakun which was the most followed by 51 species found in Longmen.? There were 5 divisions, 42 families, 51 genera, and 68 species in invertebrate. Mollusca were the most with 35 species followed by Arthropoda with 18 species. For fish, there were 3 orders, 20 families, 25 genera, and 30 species. There were 7 species for Pomacentridae which was the most followed by Acanthuridae, Blenniidae, and Chaetodontidae with 2 species separately. Compared with two previous years, the species found in five areas were less than the ones in 2008.? Besides, the Ecology Index had changed slightly. Although the amount of fish increased, the species decreased in some areas. We presumed that the cold current had the short-term impacts on organism in intertidal zones which made the amount of economic species decline sharply. Furthermore, we found the lower economic value species had become the new target of fishing activities. Therefore, the biota appearance was less than the one in 2008. In the investigation, we continued the survey from July and found the species in less interference increased lightly. This indicated that recovery from the cold current damage could be faster without artificial effects. Therefore, the habitats needed more protection and less interference to revive the original ecology. Moreover, the monitoring should be continued to trace the follow-up effects caused by cold current.? The intertidal zone environment and species movement needed to be understood in order to carry out the ecological conservation and resource management. When the ecology reaches the new balance, the productive intertidal zones could be utilized in sustainable way.
About survey for the variation of Penghu intertidal seeweed biomass, localities under investigation are Leejengjiao, Ansan, Wukan, and Herjie from the main island and Sikansan from Jibei’s northern island. The growth of Sargassum spp. was particularly observed. The ocean temperature was higher than last year compared to this year; this phenomenon resulted in shortened growth season and less biomass.? In addition, we found out that the trading market for Monostroma is only thirty or forty percentage compared to last year while the farmed and wild Pophyra harvest consists of only forty percent. The five samplings on the tidal flat within 2 months were observed to yield biomass of only three percentage of last year, and the brown and blue green algae were more than last year. The dominant species of five samplings showed fluctuation at the same time, Monostroma nitididum, Ulva lactuca, Lyngbya majuscule, Brachytrichia quoyi were recorded at Leejenhgjiao, M. nitidum and Enteromorpha intestinalis at Ansan, Colpomenia sinuosa, Hydroclathrus clathratus and L. majuscule and Padina minor at Wukan, and M. nitididum, U. lactuca, Colpomenia sinuosa and Turbinaria ornate and Padina minor growing on tidal pool at Sikansan. The three species of Sargassum found at Wukan was measured for their growth rates during the sampling period. S. crassifolium and S. glaucescens growing on the subtidal area were longest on the last two weeks of April, but S. polycystum on the tidal pool grew slowly until the last two weeks of May. In addition, surface topography was measured this year. Both the tidal flat in Wukan and Sikansan were shorter and steeper, resulting in less biomass than in other sampling areas. Following other researches, it supported the relationship of the seaweed yield with the temperature change. It is recommended that survey should be continued to find the relationship of the fluctuating algae growth of algae.
There were 20 sampling sites selected for the transect survey of benthic invertebrate fauna and recorded the coral coverage in 2009. The result of SCUBA diving survey found 117 species of 55 families in the echinoderms, mollusks, and crustaceans. This is not the first time of the chilling injury in the Penghu, and such event may more frequently occur because the degree of global warming is more serious, and the amplitude of global temperature is larger. To synthesize the results after two years, it is commented that it is necessary to establish the marine protected area in the south Penghu which is slightly affected by this chilling injury, and it may have the ability to maintain high biodiversity in the Penghu. The establishment of marine protected area could be helpful to the sustainable use of the marine resources.
? In the northern and inner sea, fish communities have been recovered significantly after one year of serious damage. The best recovery families were Labriidae, Pomacentridae, and Chaetodontidae. Overall speaking, the fastest recovery is at Mu-Tou-Yu, then northern and inner areas. The species number at slightly affected southern region is also recover but gradually, as to the east region, species resilience there was quite slow compare to the northern waters. The results showed us that the resilience is inconsistent among different islets. This phenomenon should be related to whether the habitat has been recovery, whether the amount of larval fish recruit is enough, and the local ocean current and marine environmental changes.
In order to know the variation of fishery resource, we collected fisheries-based data from April to November in 2009 in Penghu. The CPUE of Long Line fishery in north region from Apr. to Oct. was 18.8~44.7 kg per day per household and the Labridae, Mullidae and Serranidae fishes were dominant usually. In south region, the CPUE of Long Line fishery in Apr. and Nov. was 52.9 and 58.3, respectively. From Apr. to Nov., the CPUE of Pole and Lines Boote fishery near Hujing isle and Wangan isle was 10.1~30.6 and 14.0~28.4 kg per day per household with most dominant families, Monacanthidae and Caesionidae, respectively. The CPUE of Gill Net fishery from south to middle water of Penghu was 11.2~67.8 kg per day per household from Apr. to Nov. and dominant with Gerreidae, Terapontidae, Lethrinidae and Haemulidae. The CPUE of Gill Net fishery near Wangan isle was 8.0~31.1 kg per day per household. The common dominant families were Carangidae, Siganidae, and Sparidae. The CPUE of Drag Net fishery was 48.3~133.0 kg per day per household from Jun. to Nov. and dominant with Loliginidae, Red tail shrimp, Priacanthidae and Monacanthidae. The CPUE of Set Net fishery from Jan. to Jun. was 671.7, 290.0, 324.4, 527.0, 216.6 and 175.9 kg per day per household, respectively. The most dominant catch of Set Net fishery was Scombridae except Mar. and Apr. which was dominated with Siganidae and Carangidae, respectively. |