Reproductive biology of female bigeye tunaThunnus obesusin the western Pacific Ocean

Abstract

The reproductive biology of female bigeye tuna Thunnus obesus was assessed by examining 888 fish (ranging from 84·9 to 174·4 cm fork length, LF ) caught by Taiwanese offshore longliners in the western Pacific Ocean from November 1997 to November 1998 and November to December 1999 and 258 gonad samples from these fish. The overall sex ratio of the catch during the sampling differed significantly from 0·5, but males were predominant in sizes >140 cm LF . Reproductive activity (assessed by histology), a gonado-somatic index, and the size-frequency distributions of whole oocytes indicated that spawning occurred throughout the year and the major spawning season appeared to be from February to September. The estimated sizes at 50% maturity (LF50 ) of females was 102·85 cm (95% c.i.: 90·79-110·21 cm) and the smallest mature female was 99·7 cm LF . They are multiple spawners and oocytes develop asynchronously. The proportion of mature (0·63) and reproductively active (0·70) females with ovaries containing postovulatory follicles indicated that they spawn almost daily. Batch fecundity for 15 females with the most advanced oocytes (>730 µm) ranged from 0·84 to 8·56 million eggs (mean ± s.d. = 3·06 ± 2·09). The relationships between batch fecundity (FB , in millions of eggs) and LF (cm) and round mass (MR , kg) were FB=9·91×10-14LF6·38 (r(2) = 0·84) and FB=8·89×10-4MR2·05 (r(2) = 0·80), respectively. The parameters estimated in this study are key information for stock assessments of T. obesus in the western Pacific Ocean and will contribute to the conservation and sustainable yield of this species.

The key role of the Northern Mozambique Channel for Indian Ocean tropical tuna fisheries

“…Spawning frequency for the 3 species could not be determined in the Indian Ocean due to the absence of postovulatory follicles in most tunas sampled while data from the Pacific indicate a frequency close to daily, i.e. 1.1-1.2 days in skipjack (Hunter et al 1986), 1.1-2 days in yellowfin, and 1.4-1.6 in bigeye tuna (McPherson 1991;Schaefer 1996;Itano 2000;Sun et al 2013) Recent studies based on lipid classes and profiles of fatty acids that focused on the mechanisms of energy allocation in yellowfin and skipjack showed the tight linkage between environmental conditions and egg production (Zudaire et al 2014(Zudaire et al , 2015Grande et al 2016). Skipjack are described by an income breeding strategy, i.e.…”

Reproductive biology of female striped marlin Kajikia audax in the western Pacific Ocean

“…larger females are likely to have a shorter spawning interval than smaller females. No significant difference was found however, in spawning frequency between different size groups for Thunnus obesus (Lowe 1839) (Sun et al., ). More evidence is needed to support this assumption.…”

“…Ovaries were weighed to the nearest 0·1 g and sub-samples of ovaries were preserved in 10% neutral buffered formalin (Cuellar et al, 1996) for later histological examination. Three of the most advanced ovaries containing hydrated oocytes were selected from samples (oocyte diameters ranged from 905·5-1395·5, 915·1-1316·5 and 650·2-864·3 μm for the three fish) collected April to September 2009 for evaluating the synchronicity of oocyte development within and between ovaries (Arocha, 2002;Sun et al, 2009Sun et al, , 2013. The maturity and development of ovaries were assessed mainly based on the development of the most advanced group of oocytes (MAGO), so the number and size of MAGO were counted and measured for each of the three samples.…”

Komposisi Jenis Dan Distribusi Ukuran Ikanpelagis Besar Hasiltangkapanpancingulurdi Sendangbiru, Jawatimur

“…Untuk ikan tuna mata besar, kisaran ukuran panjang yang sudah dapat dianggap dewasa adalah 91-100 cm dan setara dengan umur 2 tahun (Kikawa, 1953in Miyabe, 1994dalam Lehodey et al, 1999Sun et al, 2006). Untuk ikan madidihang berada pada kisaran panjang yang sama namun setara dengan umur 1.6 tahun (Lehodey et al, 1999).…”