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Vol. 50 No. 3, 2011
Age and Growth Estimates of the Blacktip Sawtail Catshark Galeus sauteri in Northeastern Waters of
Taiwan
Kwang-Ming
Liu1 , Chia-Ping Lin1 , Shoou-Jeng Joung2 , and Shyh-Bin Wang1,*
1Institute
of Marine Affairs and Resource Management, National Taiwan Ocean Univ.,
2 Pei-Ning Road, Keelung 202, Taiwan
2Department of Environmental Biology and Fisheries
Science, National Taiwan Ocean Univ., 2 Pei-Ning Road, Keelung 202,
Taiwan
Kwang-Ming Liu,
Chia-Ping Lin, Shoou-Jeng Joung, and Shyh-Bin Wang (2011) The blacktip sawtail catshark Galeus
sauteri is a small, demersal species that inhabits tropical and
subtropical coastal waters of the western Pacific region. It is one of
the most important small shark species in terms of catch biomass for
the trawl fishery in Taiwanese waters, but its stock status is poorly
known. In this study, age and growth of this species were described
from 739 specimens (388 females and 351 males, 8.5- 49.8 cm in total
length; TL) collected from Nov. 2007 to Oct. 2008 in waters off
northeastern Taiwan by demersal or shrimp trawlers. Sex-specific
relationships between the weight (TW) and TL significantly differed and
could be expressed as: TW =
2.09 × 10-3TL3.10
(n = 1052, p < 0.05) for females and TW = 3.45 × 10-3TL2.94 (n = 884, p < 0.05) for males. Age was
determined using band-pair reading of sectioned vertebrae. A single
growth band pair (comprising translucent and opaque bands) is formed
each year, and up to 14 and 12 band pairs were respectively observed
for females and males. An edge analysis indicated that the translucent
bands formed from July to Aug. Four growth functions, the traditional
von Bertalanffy (VBGF), VBGF with a fixed size-atbirth (L0),
Gompertz, and Robertson (logistic) were used to model the observed
length-at-age data. The sexspecific growth equations significantly
differed. The logistic function had the best fit for both sexes, and
the growth parameters including the 95% confidence intervals with a
bootstrap method were estimated as follows: asymptotic length L∞ = 48.30 (47.16-49.47)
cm TL, and growth coefficient k
= 0.374 (0.344-0.402) yr-1 for females, L∞ = 44.29 (42.91-45.88)
cm TL and k = 0.392
(0.356-0.429) yr-1 for males. The ages at maturity were
respectively estimated to be 9.14 and 7.57 yr for females and males, by
substituting the mean sizes at maturity into the Robertson growth
equation. Longevities of females and males were respectively estimated
to be 20.9 and 12.4 yr.
Key words: Life
history parameters, Vertebra, Robertson function, Bootstrap method,
Longevity.
*Correspondence: Tel: 886-2-24622192 ext. 5602. Fax:
886-2-24635859. E-mail:sbwang@mail.ntou.edu.tw
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