Age and growth of Indo-Pacific sailfish, Istiophorus platypterus

Дата канвертавання22.04.2016
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Age and growth of Indo-Pacific sailfish, Istiophorus platypterus,from the Arabian Gulf

M97310002 林圻鴻


Dorsal and anal fin spines were collected from 85 sailfish from the Gulf and used to estimate age from putative annular growth bands

observed in thin transverse sections. A total of 84 (98.8%) of these were successfully read with an average percent error in precision of 4.8%. Nine year classes (0+ to 8) were estimated from spines examined. Spines lacking a pair of translucent and opaque rings were placed in the 0+ year class; however the somatic size of these individuals suggested they were between 6 and 10 months in age. Estimated age classes for females (n = 50) ranged from 0+ to 8 years, while males (n = 34) ranged from 0+ to 6 years. Age class 1, followed by 0+ and 3 were the most abundant for both sexes, comprising 75% of all samples.

Females exhibited the maximum sizes for lower jaw-fork length (LJFL) and weight within 101 sampled sailfish. The LJFL for females

(n = 65) ranged in size from 129 to 199 cm and weight ranged from 11.5 to 47.0 kg. For males (n = 36), LJFL ranged from 125 to 177 cm and weight ranged from 12.5 to 38.0 kg. The von Bertalanffy growth function fitted to the observed LJFL, weight and age data indicated a rapid growth rate during the first 2 years, after which length stabilized for males and females continued growing to a greater maximum mean length and weight.

The relationships of measured morphological traits to LJFL derived from the non-linear equation Y = a LJFLb and their regression coefficients showed a negative allometric growth for weight, head, and pelvic fin length. Most other measurements were effectively isometric, with the exception of the anal fin in males, which showed positive allometric growth. A comparison of allometric growth between females and males using a modified t-test against linear regressions indicated no significant differences between LJFL and other morphometric characters (P ranged 0.135–0.980).



由鰭條的檢定評估可將其區分為九個年級群 ( 0+ ~ 8 )。而在鰭條的判讀下缺乏0+時期的明暗帶判讀;然而可藉由其細胞體的大小可推估其大約是介於6個月至8個月。而評估雌性雨傘旗魚(n=50)的年齡範圍介於0+~8歲,而雄性雨傘旗魚(n=34)其年齡範圍介於0+~6歲.。0~3歲的樣本數佔了全部的75%。

在101個雨傘旗魚樣本中,雌性雨傘旗魚表現出其眼尾叉長與體重均具有較大值。雌性雨傘旗魚(n=65)其眼尾叉長大小介於129~199cm而體重介於11.2~47.0 kg。雄性雨傘旗魚(n=36)其眼尾叉長大小介於125~177cm而體重介於12.5~38.0 kg。由von Bertalanffy成長方程式的推估與實際觀測眼尾叉長、體重和年齡資料做比對指出在2歲以前其成長快速,在兩歲以後雄性的雨傘旗雨其體長大小維持穩定不變而雌性的雨傘旗魚則持續成長至最大體長及體重。

藉由非線性方程式 Y= aLJFLb 可取得其外觀與LJFL的相關性而他們的迴歸係數則顯示出其體重、頭和腹鰭長是負相關的異速成長。而大部分的測量值在等體積的情況下是有效地,除了雄性雨傘旗魚的臀鰭例外,此現象顯示其為正相關的異速成長。在雄性與雌性間異速成長的比較中使用線性迴歸的t檢定法指出在LJFL和其他的外觀型態上是非顯著性差異(P值介於0.135-0.980間)。

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