耳石結構及微化學應用在大肚溪河口日本海鰶的成長與洄游環境史之研究

Application of otolith structure and microchemistry to study growth and migratory environmental history of Japanese gizzard shad Nematalosa japonica in the Tatu creek estuary of Taiwan

李浩祥(Hao-Hsiang Lee)

指導教授 ： 曾萬年

國立臺灣大學/生命科學院/漁業科學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01362

摘要

日本海鰶 (Nematalosa japonica) 為大肚溪河口域魚類的優勢種，至今其洄游模式、年齡及成長等生活史資訊皆不清楚。本研究藉由耳石的特殊結構及微化學組成，來了解日本海鰶在大肚溪的初期生活史、年齡與成長，及其在海水與淡水之間的移動情形，以便釐清日本海鰶是否為溯河性魚類，以及其在台灣河川環境多變情況下的生活史多樣性。
由體長頻度分佈及生殖腺指數的月別變化得知大肚溪日本海鰶的產卵期為每年2 ~ 4月之間。耳石日周輪結構及鍶鈣比的時序列變化，顯示兩個特殊耳石標記：(1) 仔魚變態為稚魚時所形成的變態輪 (Metamorphosis check)，變態日齡為 27.7 ± 5.3天 (n = 40)；及 (2) 稚魚回到河口中上游時所形成的河口輪 (Estuary check)，其日齡為47.2 ± 9.2天 (n = 18)。根據耳石的年輪結構，所建立的日本海鰶成長方程式為：Lt = 218.3 (1- e - 0.31 ( t + 0.8 ) )。其極限體長 (L∞) 為218.3 mm，成長率 (K) 為0.31 yr-1。
日本海鰶耳石鍶鈣比與水體中的鹽度，呈顯著正相關關係 (p < 0.05)。鹹淡水的界線之鍶鈣比值為3.1 ‰。耳石鍶鈣比的時序列變化顯示，日本海鰶的初期生活史呈現多重的漂散模式，而幼魚皆於河口區哺育，成魚可能至上游淡水環境產卵。此外，隨著年齡的增加可明顯區分為兩種洄游模式：(1) 高鹽度型：耳石平均鍶鈣比值較鹹淡水界線高，其棲地利用偏向河口下段的海水區，此型佔所有分析樣本的36 % (n = 36)；及 (2) 低鹽度型：耳石平均鍶鈣比值較鹹淡水界線低，其棲地利用偏河口上段的淡水區，此型佔44 %。兩型的成長方程式有顯著性差異 (p < 0.05)，高鹽度型者成長較慢，但極限體長較大；而低鹽度型則成長較快，極限體長較小。日本海鰶棲地利用與成長策略的分歧現象，可能與環境條件變異性的適應策略有關。其應變策略是否為遺傳變異，或是一種逢機現象，則有待研究。

關鍵字

日本海鰶 ； 耳石 ； 日周輪 ； 年輪 ； 鍶鈣比 ； 年齡與成長 ； 棲地利用

並列摘要

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.

並列關鍵字

Japanese gizzard shad ； otolith ； daily growth increments ； annulus ； Sr:Ca ratios ； age and growth ； habitat utilization

參考文獻

許智傑 (2005). 烏魚仔稚魚期耳石微細構造與初期生活史事件的關係之研究。台灣大學動物學研究所碩士論文，台灣，台北

Arai, T., T. Otake and K. Tsukamoto (1997). Drastic changes in otolith microstructure and microchemistry accompanying the onset of metamorphosis in the Japanese eel Anguilla japonica. Marine Ecology Progress Series 161, 17-22

Beamish, R. J. and G. A. McFarlane (1983). The forgetten requirement for age validation in fisheries biology. Transaction of American Fisheries Society 112(6), 735-743

Brophy, D., T. E. Jeffries and B. S. Danilowicz (2004). Elevated manganese concentrations at cores of clupeid otoliths: possible environment, physiological, or tructural origins. Marine Biology 144, 779-786

Campana, S. E. (1983). Feeding periodicity and the production of daily growth increments in otoliths of steelhead trout (Salmo gairdneri) and starry flounder (Platichthys stellatus). Canadian Journal of Zoology 61, 1591-1597