臺灣東部海域雨傘旗魚族群動態及資源評估

Population dynamics and stock assessment of sailfish (Istiophorus platypterus)in waters off eastern Taiwan

江偉全(Wei-Chuan Chiang)

指導教授 ： 孫志陸

國立臺灣大學/理學院/海洋研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.01994

摘要

本研究以台灣東部海域雨傘旗魚為對象，探討其年齡與成長及生殖生物學，並將所得結果應用於單位加入生產量（Y/R）及單位加入產卵親魚量（SSB/R）模式分析，以評估台灣東部海域雨傘旗魚之資源現況。
自1998年7月至2002年12月止，每月於台東新港魚市場收集雨傘旗魚生物資料，總計測量得6,279尾體長（雌魚1,927尾，雄魚4,352尾），樣本下顎尾叉長（LJFL）範圍為78∼239 cm，全重（RW）為1∼60 kg，LJFL大於227 cm或RW大於46 kg以上全為雌魚。
以第一背鰭第四硬棘為年齡形質進行年齡與成長研究，計採獲1,166枚硬棘樣本，其中1,135（97 %）枚硬棘樣本（雌魚436枚，雄魚699枚）成扒i行年齡查定，結果發現雌雄間年齡別之體長及各項成長參數皆具顯著差異，雌魚成長較雄魚快且可成長至較大體型，推估Generalized von Bertalanffy成長方程式之各項成長參數雌魚為︰極限體長（L∞）= 343.8 cm、成長係數（K）= 0.011 yr-1、體長為零時之理論年齡（t0）= –0.468 yr及參數（m）= –1.639。雄魚之成長參數為：極限體長（L∞）= 294.0 cm、成長係數（K）= 0.023 yr-1、體長為零時之理論年齡（t0）= –0.704 yr及參數（m）= –1.288。
利用生殖腺成熟指數（528尾）及生殖腺樣本（391尾）性成熟階段之月別變化，推測台灣東部雨傘旗魚生殖季節為4∼9月。50 %性成熟LJFL雌魚為166.376 cm，雄魚151.556 cm。雨傘旗魚為多次產卵魚種，估算產卵頻率為1.89天，單次產卵數（BF）為0.2∼2.48百萬粒，BF與RW及LJFL之關係為：BF = 2.03×10-3 RW1.936（r 2 = 0.714；n = 18）；BF = 5.46×10-15 LJFL6.283（r 2 = 0.667）。
經由年齡與體長關係將樣本LJFL組成資料轉換成漁獲年齡組成，進一步由漁獲曲線分析，估計得全死亡率雌魚為0.56 yr-1，雄魚為0.58 yr-1；利用Pauly經驗式估算得自然死亡率（M）雌魚為0.26 yr-1，雄魚為0.27 yr-1。假設在不同組合情況下，評估各種自然死亡率（雌魚：0.20, 0.26, 0.30, 0.35 yr-1，雄魚：0.20, 0.27, 0.30, 0.35 yr-1）、漁獲死亡率（F, 0∼1 yr-1）及初捕年齡（tc, 1∼10 yr）對Y/R及SSB/R之影響，結果得知在目前（即初捕年齡tc = 5歲，雌魚自然死亡率為0.26 yr-1，雄魚自然死亡率為0.27 yr-1）的情況下，雌雄之漁獲死亡率（FCUR）皆低於F0.1；另估得目前雌魚SSB/R為14.90 kg，生殖潛能比例（SPR）為38.6 %。這些結果顯示此資源目前屬於適度開發階段，惟此漁業近年開發頗速，為保有此魚種資源之永續利用，其資源動態及漁業發展必須持續加以評估及監視。

關鍵字

年齡與成長 ； 雨傘旗魚 ； 台灣東部海域 ； 單位加入生產量 ； 生殖生物學 ； 單位加入產卵親魚量 ； 資源評估

並列摘要

Age-growth and reproductive biology of sailfish were studied and the results were applied to yield per recruit (Y/R) and spawning stock biomass per recruit (SSB/R) analysis to assess the current stock of sailfish in the waters off eastern Taiwan.
Length and weight data were collected monthly from a total of 6,279 sailfish (1,927 females and 4,352 males) landed in Shinkang Fish Market during July 1998 to December 2002. The fish sizes ranged from 78 to 239 cm LJFL (lower jaw fork length) or 1 to 60 kg RW (round weight). The proportion of females increased with fish size and reached 100% at fish size larger than 227 cm or 46 kg.
Age and growth were examined by counting growth rings on cross sections of the fourth spine of the first dorsal fin of 1,135 (436 female and 699 male) sailfish. Significant differences were found in length-at-age and estimated growth parameters between sexes. Females grew faster and reached larger sizes than males. The generalized von Bertalanffy growth parameters estimated for females were the following: asymptotic length (L∞) = 343.8 cm, growth coefficient (K) = 0.011 yr-1, age at zero length (t0) = –0.468yr, and the fitted fourth parameter (m) = –1.639. The growth parameters estimated for males were the following: asymptotic length (L∞) = 294.0 cm, growth coefficient (K) = 0.023 yr-1, age at zero length (t0) = –0.704 yr, and the fitted fourth parameter (m) = –1.288.
Monthly variations in gonadosomatic index of 528 sailfish and histological examination on the 391 gonad tissue provided the basis to define the different stages of maturity. This information indicated that the sailfish spawned from April to September. Length at 50% maturity was 166.376 cm and 151.556 cm, respectively for females and males. Sailfish are a multiple spawning species, the spawning frequency was 1.89 days, batch fecundity equaled 0.2–2.48 million eggs. The relationship between batch fecundity in millions (BF) and weight (kg) or length (cm) was: BF = 2.03×10-3 RW1.936 (r 2 = 0.714; n = 18) and BF = 5.46×10-15 LJFL6.283 (r 2 = 0.667).
Via age-length transformation and catch curve analysis, total mortality rate (Z) was estimated as 0.56 and 0.58 yr-1, and the natural mortality rate (M) was 0.26 and 0.27 yr-1 respectively for females and males as obtained using Pauly’s empirical equation. The effects of different levels of M (0.20, 0.26, 0.30, 0.35 yr-1 for females and 0.20, 0.27, 0.30, 0.35 yr-1 for males), fishing mortality (F, 0–1.0 yr-1) and age at first capture (tc, 1–10 yr) on Y/R and SSB/R of sailfish were evaluated. The results showed that at the current tc of 5 yr and the current M of 0.26 yr-1 for females and 0.27 yr-1 for males, the current F values were below F0.1 for both sexes. SSB/R was 14.90 kg and spawning potential ratio (SPR) was 38.6 %. The sailfish in the waters off eastern Taiwan appear to be moderately exploited. However, in view of the recent rapid increase in fishing effort, it is evident that the stock condition and developments in the fishery still need to be monitored.

並列關鍵字

age and growth ； eastern Taiwan waters ； spawning stock biomass per recruit ； yield per recruit ； reproductive biology ； sailfish ； stock assessment.

參考文獻

Akaike, H., 1969. Fitting autoregressive models for prediction. Ann. Inst. Stat. Math. 21, 243–247.

Arocha, F., 2002. Oocyte development and maturity classification of swordfish from the north-western Atlantic. J. Fish Biol. 60, 13–27.

Bancroft, J.D., Stevens, A., 1996. Theory and practice of histological techniques. 4th ed., Churchill Livingstone, New York, 766 pp.

Beamish, R.J., Fournier, D.A., 1981. A method for comparing the precision of a set of age determinations. Can. J. Fish. Aquat. Sci. 38, 982–983.

Beebe, W., 1941. Young sailfish. Science 94, 300-301.