Reproductive biology of whitespotted bamboo shark Chiloscyllium plagiosum in northern waters off Taiwan

Abstract

In total, 491 whitespotted bamboo sharks were collected from northern Taiwanese waters from February 2002 to February 2003. The sex ratio of the specimens was 0.65, total length (TL) ranged from 35.3-85 cm, and weight ranged 124-2580 g. The mean size at first maturity was estimated to be 64.9 and 65.6 cm TL for females and males, respectively, based on the relationship between mature percentage and TL. The ovulation season was estimated as March to May based on gonadosomatic index (GSI) variations and captive observation. The monthly changes in GSI of males suggested that the mating season was from December to January. The inconsistency between mating and ovulation seasons suggested that females have sperm storage and delayed fertilization. One or two eggs were deposited every 6 or 7 days on average. Deposition of eggs extended for 2 months, and fecundity was 8 ± 3.8 eggs. Thirteen of 48 eggs deposited in 2003 were hatched and the hatching rate was 0.27. The hatching period was 107 ± 9.3 days with accumulated water temperature ranging from 2372-2835 ° C.

Comparative rates of growth of the Port Jackson shark throughout its southern Australian range

“…This discrepancy between these two growth models has been observed in other species of elasmobranchs, e.g. Chiloscyllium plagiosum (Chen et al 2007), Carcharhinus plumbeus (Romine et al 2006) and Isurus oxyrinchus (Natanson et al 2006). The Gompertz models fit the data well for both sexes, but provided a biologically unreasonable underestimate of maximum asymptotic length, subsequently overestimating the rate at which the asymptotic length of the species is attained (Romine et al 2006).…”

Size compositions and reproductive biology of an important bycatch shark species (Heterodontus portusjacksoni) in south-western Australian waters

“…However, the males and females of the oviparous hemiscylliid Chiloscyllium plagiosum attain a similar length (Chen & Liu, 2006). Thus, among oviparous species, there is no consistent tendency for one sex to grow larger than the other.…”

“…However, the L 50 at maturity is typically greatest in the sex with the greatest maximum length and, in the case of Chiloscyllium plagiosum in which the maximum lengths of the males and females were similar, the L 50 s at maturity of the two sexes, are also similar (e.g. Chen & Liu, 2006). The marked differences between the maximum sizes attained by the females and males in south-western and southeastern Australia are paralleled by differences in the L 50 s at maturity.…”

“…This conclusion regarding the timing of ovulation is consistent with the fact that the five females found with egg cases in utero were all caught between August and December. The fact that the GSIs of females peaked in August, rather than in May as with males, suggests that the females store sperm for a period prior to fertilization, as occurs in a number of chondrichthyans (Smith et al, 2004;Walker, 2005;Chen & Liu, 2006).…”

Spatial, seasonal, and ontogenetic variations in the significance of detrital pathways and terrestrial carbon for a benthic shark, Chiloscyllium plagiosum (Hemiscylliidae), in a tropical estuary

“…Of these, the white-spotted bamboo shark Chiloscyllium plagiosum (Hemiscylliidae) is common over soft seabeds at depths of , 20 m in the Pearl River estuary and adjacent waters. Recent studies of the biology of this shark (Chen and Liu 2006;Chen et al 2007;Cornish et al 2007) have focused on its growth, reproduction, and body-tissue contaminants, but little is known of its trophic ecology nor how this is related to the habitat use of this shark. To address this, we described the major prey of this small, benthic shark using stomach-content analyses.…”