Fishery Biology and Population Dynamics of Hiant Venus (Katelysia hiantina) in the Tapon Bay, Southern Taiwan

• Main Author: 莊鈺光
• Other Authors: 鍾國仁
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/67087002258760832219

碩士 === 國立嘉義大學 === 生物資源學系研究所 === 96 === Abstract Tapon Bay locates in the Tungkang of Pingtung County in southern Taiwan, has area of about 530 hectares, and abounds in fishery resource, which contributes to a big part of incomes of many residents in the region. There were mass culture of oysters and many of cage-cultures in the Bay. Since 2001, any practice of aquaculture has been banned legally for developing the local tourism. After the inhibiting factors from, the mass culture of oysters and fish declined and benthic population of clams developed rapidly. Katelysia hiantina was one of the most important and valuable species in the bay because of its large size and the large potential of productivity. However, extraordinarily hard collection by the fishers and the pollution from the implementation of a civil engineering had put a huge impact on the resource. The aims of this thesis were to study the fishery biology, population dynamics, and the current status of hiant venus (K. hiantina) for designing an effective system to manage the resource. The sampling works were carried out in two sessions, the first one was between September 2004 and August 2005, the other one was between June and November 2007. The distribution of K. hiantina was limited to the west side of outlet of the Bay to the sea, and only occupied less 1/5 area of the bay. Few species of mollusks were collected, and there were 7 species of bivalve; Anomalocardia producta was most abundant, K. hiantina followed. The limited distribution of benthos might result from the low ratio of refreshing water and small influence by the tide because of narrow channel (20 meter)connecting the Bay and the coastal water. The lowest water temperature detected in the bay was about 20.6℃, the highest one was 32.1 ℃, and the average was 27.9 ℃. The coolest month was December.. The concentration of dissolved oxygen of the under water was very low at the hot months, the lowest detected was 2.38 ppm . There should be three cohorts in the year, a newborn cohort, recruiting cohort and senior cohort . The recruitment (shell length about 30 ㎜) entered around March, and lasted to September. The index of von Bertalanffy curve was L∞ ＝ 62.6 ㎜, k ＝ 0.083, and t0 = 2.4㎜, respective. The major annual production period was from June to October, which overlapped with reproduction season for about 4 months. Reproduction activity began in March, lasted to September, peaked in May and August respectively. The minimum size at maturity was 29.0 ㎜ shell length. The major spawning group was larger than 40 ㎜. The results of the sampling of the second session showed that the habitat had been destroyed seriously by the implementation of a civil engineering, which had made the amount of collected mollusks very small. Most of collected bivalves were newborn ones; it was also showed that larva had high ratio of natural mortality. The benthos was composed by few species and the dominant species had much larger amount than the minor ones, all of those showed that the Bay was a harsh environment for the most species of the habitants living in it. K. hiantina should be highly valued because that it was the only species that could live in the Bay well and posed commercial potential. The results of the studies showed that suitable size of recruitment should be above 40 ㎜, and the catching of the species should cease during the reproduction seasons. The enclosed environment of the bay was very vulnerable to disturbance, and any construction should be very carefully considered to avoid destroy these rare resources. Key Words: Tapon Bay, Katelysia hiantina, fishery biology, population dynamics, environmental factors, reproduction, resource protection