| 英文摘要 |
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￠XE-121.5￠XE in longitude and 25￠XN-25.5￠XN 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!O3.8 egg cases and the spawning interval was about 6 to 7 days lasting two months. The incubation period was 107!O9.3 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￠XE-121.3￠XE in longitude and 21.4￠XN-23￠XN 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 |