博士 / 國立臺灣大學 / 動物學系 / 86 / The area 24.5-27 oN and 120-123 oE off northeastern
Taiwan was selected for ichthyoplankton study. It
included the three watermasses--southern East China Sea (SECS),
mixing zone (MIX) and Kuroshio (KUR) and thus three hydrographic
ecotopes were identified. The seasonal variation of the fish
fauna based on ichthyoplankton was analyzed. This study also
applied the biological parameters of Japanese anchovy larvae,
which hatch in early spring, to interpret the effects of the
hydrographic dynamic on the recruitment of the population off
northeastern Taiwan. The major purpose of this study were to
explore the effects of water masses on the distribution, growth
and nutritional condition of ichthyoplankton, and to clarify the
variation of year stock in coastal fishery. A total of
327 ichthyoplankton samples were taken during 14 cruises from
June 1989 to September 1992 in the waters off northeastern
Taiwan. The density of ichthyoplankton was lowest in winter,
increased in spring, reached the maximum in summer, and declined
in autumn. Average densities of the ichthyoplankton in the 3
hydrographic ecotopes were highest in the SECS, moderate in the
KUR, and lowest in the MIX. In total, 59 789 individuals of
ichthyoplankton belonging to at least 124 families and 547
species were collected.The major ichthyoplankton species,
comprising about 60% of the total catch, were distinctive in
different seasons and waters. Decapterus spp. (14.0%) and
Auxis spp. (6.2%) were abundant in spring; Auxis spp. (6.9%) and
Benthosema pterotum (5.8%) in summer; B. pterotum (55.2%),
gobiids (4.1%), and Synagrops sp. (3.2%) in autumn; and B.
pterotum (15.4%) and Gonostoma gracile (7.5%) in winter. B.
pterotum (23.0%) and Auxis spp. (5.1%) were abundanct in SECS;
Decapterus spp. (28.6%) and Auxis spp. (7.1%) in MIX; and B.
pterotum (5.6%) and Vinciguerria nimbaria (4.4%) in KUR. The
dendrogram of these major ichthyoplankton species exhibits 7
species-associated groups. The survival of Japanese anchovy
larvae is affected by water masses off northeastern Taiwan.
Three conclusions were drawn from this study: 1. The RNA/DNA
ratio of the larvae were different significantly among the
hydrographic ecotopes. Based on the RNA/DNA ratios, the
nutritional condition of Japanese anchovy larvae from the KUR
was poorer than that from the SECS and MIX. The starvation
probability was higher (27.9﹪) in the KUR than in the SECS
(2.8﹪) and MIX (5.0﹪). 2. Indices of the fluctuating
asymmetry (FA) were calculated for 3 otolith traits, i.e., mean
absolute asymmetry (differences between right and left) maximum
radius (MOR), perimeter (OP) and surface area (OA)). Mean
absolute asymmetry in MOR and OP were not significantly
different among the hydrographic ecotopes. Mean absolute
asymmetry in OA was significantly different among the
hydrographic ecotopes, greater in KUR than in the SECS and MIX.
3. According to the growth equation, the daily somatic and
otolith growth of larval anchovy was faster in the KUR than in
the MIX. The relative growth between the MOR and standard
length was not significantly different among the hydrographic
ecotopes. The length frequency distribution of the larval
Japanese anchovy exhibited significant differences between year
classes and among the hydrographic ecotopes.
| Identifer | oai:union.ndltd.org:TW/086NTU00312003 |
| Date | January 1998 |
| Creators | Huang, Jiunn-Bin, 黃俊邠 |
| Contributors | Chiu Tai-Sheng, 丘臺生 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 121 |
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