Reproductive biology of striped bonito, Sarda orientalis, in the waters off eastern Taiwan
Date Issued
2015
Date
2015
Author(s)
Huang, Jun Chun
Abstract
The reproductive biology of striped bonito (Sarda orientalis) was assessed by examining 323 specimens sampled from the catches of set-net, troll line, longline and danish seine fisheries in the waters off eastern Taiwan during December 2013 to November 2014. Body sizes of the specimens ranged from 30.8 to 80.2 cm in fork length (FL) and 0.42 to 7.69 kg in round weight. The overall sex ratio (number of females to the total number of fish) was 0.46 which did not differ significantly from 0.5 based on the Chi-square test. The monthly sex ratios were homogeneous among months in 2014. However, the sex ratios at different length classes were significantly different, females were predominant in sizes > 60 cm FL. Gonadosomatic index (GSI), monthly variation in mean diameters of oocytes and the gonadal development stages were used to assess the reproductive activity of striped bonito. Results showed that the spawning season of striped bonito occurred from January to June, with a peak between March and May. Based on histological examination and oocyte diameter frequency distribution, striped bonito are batch spawners and the oocytes developed asynchronously. The estimated size-at-50 % maturity was 47.8 cm FL for females, and 43.8 cm FL for males. The smallest sizes for sexually mature females and males were 44.9 and 43.0 cm FL, respectively. Females and males were estimated to spawn once every 2 days on average during the spawning season. Batch fecundity estimated from six females of 49.0 to 77.9 cm FL ranged from 11.4 to 77.9 ten thousand hydrated oocytes. The estimated relative fecundity was from 63.2 to 115.3 hydrated oocytes per gram of body weight. The parameters estimated in this study are key information for stock assessment of striped bonito in the waters off eastern Taiwan, and will contribute to the conservation and sustainable yield of this species.
Subjects
sex ratio
spawning season
size at 50 % maturity
spawning frequency
batch fecundity
SDGs
Type
thesis
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