| 英文摘要 |
1. 「台灣沿近海小型鯊魚資源之調查及評估」：
The questionnaire survey and field investigation were carried out in this study to determine the distribution and catches of small shark species in the northern and southwestern waters off Taiwan. Meanwhile, the bamboo shark which had a higher value in northern Taiwan, its fisheries biology has also examined. The results indicated that the fishing ground for Jin-Shan and Fu-Chi fishing ports was ranged from 121°E-121.5°E in longitude and 25°N-25.5°N in latitude. The components of landed small sharks were spotless smooth-hound shark (19.44%), bamboo shark (13.89%), scalloped hammerhead shark (13.89%), sawtail catshark (1.5%), starspotted smooth-hound shark (1.39%) and others such as rays (18.63%), teleost (31.25%).
The VBGF for both sexes of bamboo shark in northern Taiwan waters were follows: female ; male . The results of marginal increments analysis showed that the growth zone for both sexes was the same as one year forming one annulus in the period of June to September. At least 7 annuli in vertebrae could be identified for both sexes of bamboo shark. The sizes of maturity for female and male bamboo shark were 64.9 cm and 65.6 cm, respectively. The spawning period was from March to May. The average fecundity was 8±3.8 egg cases and the spawning interval was about 6 to 7 days lasting two months. The incubation period was 107±9.3 days.
The major fishing methods for catching small shark species in Pingtung, Kaohsiung and Taitung areas were bottom trawl, bottom gill net, pole and line, torch light net, drift gill net, long lines and set net which were known from the results of pervious studies. The major fishing ground was between 119.4°E-121.3°E in longitude and 21.4°N-23°N in latitude. And the operation depth for catching these sharks was about from 70 m to 400m. Not only small shark species were caught in these areas but also other elasmobranches such as skates, rays and rabbit fish were captured. The main small shark species were splendid lantern shark, Japanese wobbegong sawtail catshark, latern shark, sixgilled shark and other rays including blackish stingray, Bennett's stingray and sharpnose stingray for these areas. The main fishing seasons for southwestern waters were summer and autumn, while the spring and winter were the major fishing seasons in eastern waters off Taiwan. The large landed shark species in these areas were silky shark, shortfin mako, scalloped hammerhead and bigeye thresher.
2. 「鯨鯊漁業生物學及洄游路徑研究Ⅱ」：
The aim of this project is try to investigate the catch data and some biological information to establish the database for the whale shark, Rhincodon typus. Meanwhile, the satellite telemetry technique is also introduced to study the movement and migration of the whale shark around Taiwan waters.
A total of 60 whale sharks were landed in Taiwan during January and July 2006. The majority of them were caught by set net that occupied 41.7% of all catches. Only 11.7% were caught by spears this year due to the arrival of the allowance capture in July, but the spear fishery prevails in colder seasons. By comparison with landed areas, east coast still had the highest landed amount of the whale shark that occupied 61.7% of whole amount this year. From analyzing body length of 60 individuals, the highest peak was still at the 4.0-4.5 m length interval (40.0%). However, there were 12 individuals shorter than 4.0 m TL, and not any mature specimen (8.0 m TL at least) was caught this year.
Two whale sharks were released with PAT4 tags in 2005, and the tags popped-off last September and this January, respectively. Both of them have successfully recorded vertical movement data. They often occupied the depth 5-10 m where the water temperature was between 23 and 26 °C and between 15 and 20 °C. In addition, the whale shark migrates to different depth intervals more frequently in fall and winter.
According to age and total length data, parameters of the VBGE (sex combined) were estimated as L∞=16.570 m, K=0.036 yr-1, and t0=-1.295 yr, respectively, suggest that whale shark is a slow-growth species.
3. 「台灣沿海鯨豚誤捕研究與中華白海豚生態調查」：
This project includes two parts. The purpose of the first part is to continue the investigation of cetacean bycatch of coastal driftnet fishery. Based on fishermen interview and captains’ daily logging, we found that the major bycatch of cetaceans occurred when big-mesh (mesh size 9.5~12 in) nets were operated on marlin fishing in the east coast, or when the 3-layer mullet driftnets were operated at the west coast during fall and winter seasons (sep~Feb). Based on our works at Shiti and ChengKung fishing ports, we calculate the bycatch rates of the southeast coast is 0.32~0.4 dolphins/boat.day. After checking the records of inbound and outbound of fishing ports from the coast guard agency, and standardizing the big-mesh fishing efforts, we estimate the number of dolphins bycaught is about 560 animals at Shiti port, and 2210 animals at Chenkung port. We collected 37 bycaught dolphins in the past 3 years, the major species was Grampus griseus (46%), the next was Lagenodelphis hosei (24%). The sex ratio leaned toward males. The age composition includes calves, and even mother-calf pairs. The potential impact on cetacean conservation request more attention.
The purpose of the second part is to execute preliminary surveys for Chinese white dolphin (Sousa chinensis) in the waters of western coast of Taiwan. During the period of May to September 2006, 18 trips of day-cruise were executed. In total, 13 groups of Chinese white dolphins were sighted on 7 trips along the coastal waters from Miao-Li to Chia-Yi counties except Hsin-Chu and Yun-Lin counties. The sighting rates of each counties with sightings ranged 40~50%. The dolphin group size usually ranged 1~5 individuals, with the largest group, composing 10.6 + 4.1(mean + SE, n=5, range= 3~23) animals occurred at Chia-Yi county. The distribution pattern of Chinese white dolphins was clumped, accumulated at estuaries, fishing ports and WaiSanDin Sand Bar. These areas could be hotspots for their habitats. Their physical environmental characters were 9.2±2.0 average water depth, 30.4±0.1ppt average salinity, 29.2±0.3℃average water temperature, and 100~3000m distance from the shore. The mtDNA analysis on 4 samples collected in Taiwan and compared with 5 samples off gene bank from the population of China, we found not obvious separation among populations except one sample showed an unique haplotype.
The potential threaten to Chinese white dolphins include tangling from fishing nets, and pollution from two big factories near coast. In addition, WaiSanDin Sand Bar,Chia-Yi county could serve as breeding ground for them based on the occurrence of 2~4 mother-calf pairs, and could be a good candidate for whale-watching development as well as marine protected area. |
