碩士 / 國立臺灣大學 / 漁業科學研究所 / 95 / Japanese gizzard shad (Nematalosa japonica) is a dominant clupeid fish in the Tatu creek estuaries. Its life history information such as migratory pattern, age and growth is not clear so far. In this study, otolith structure and microchemistry of Japanese gizzard shad were used to study their age, growth and migratory history.
Monthly variations of fish length frequency distribution and gonadosomatic index indicated that spawning season of this fish was from February to April. The chronological changes of otolith daily growth increment and Sr:Ca ratios patterns presented two otolith checks: (1) metamorphosis check which was assumed to be formed when the fish metamorphosed from larvae to juvenile stages. The aged at metamorphosis was estimated to be 27.7 ± 5.3 days (n = 40) after birth; and (2) estuarine check, which was formed when the juveniles returned to the upper reach of the estuary. The age of return was 47.2 ± 9.2 (n = 18) days after birth. The age-length data back calculated from otolith annulus were fitted with von Bertalanffy growth equation as Lt = 218.3 (1- e - 0.31 ( t + 0.8 ) ), where asymptotic length (L∞) was 218.3 mm and growth rate (K) was 0.31 yr-1.
The Sr:Ca ratios in otolith of Japanese gizzard shad was positively correlated to the salinity of ambient water. (p < 0.05) The regression of otolith Sr:Ca ratios on salinity was y = 0.05 x + 3.10, with an intercept, the saline-freshwater boundary at 3.1 ‰. The chronological patterns of otolith Sr:Ca ratios showed that multiple types of drift existed in early life history, and the fish used estuary as nursery ground. The migratory patterns of the fish in the estuary can be classified into two types: (1) high salinity type (H type), the mean Sr:Ca ratios were higher than the saline-freshwater boundary, indicating the fish lived in the lower reach of the estuary, which consisted of 36 % of the fish examined (n = 36); and (2) low salinity type (L type), the mean otolith Sr:Ca ratios were less than the saline-freshwater boundary, indicating that the fish lived in the freshwater environment of the upper reach of the estuary, which consisted of 44 % of the fish examined. The otolith Sr:Ca ratios also indicated that the adults might migrated annually to the freshwater to spawn. The growth performance was significantly different (p < 0.05) between two types, with lower growth rate and higher asymptotic length for H type; but higher growth rate and lower asymptotic length for L type. If the differentiating habitat utilization and growth strategy of Japanese gizzard shad between these two types is due to random adaptations to the variability of environmental conditions or genetic determined needed further study.
| Identifer | oai:union.ndltd.org:TW/095NTU05451011 |
| Date | January 2007 |
| Creators | Hao-Hsiang Lee, 李浩祥 |
| Contributors | 曾萬年 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 39 |
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