Taylor S M, Harry A V, Bennett M B
Western Australia Fisheries and Marine Research Laboratories, Department of Fisheries Western Australia, 39 Northside Drive, Hillarys, P.O. Box 20, North Beach, WA, 6920, Australia.
Centre for Sustainable Tropical Fisheries & Aquaculture, College of Marine and Environmental Sciences, James Cook University, Townsville, QLD, 4811, Australia.
J Fish Biol. 2016 Nov;89(5):2399-2418. doi: 10.1111/jfb.13126. Epub 2016 Sep 15.
Differences in the reproductive biology of both the Australian weasel shark Hemigaleus australiensis and the Australian sharpnose shark Rhizoprionodon taylori were apparent between individuals from the southern-most extent of their range in eastern Australia (Moreton Bay) and those from northern Australia. For H. australiensis from Moreton Bay the total length (L ) at which 50% of individuals were mature (L ) was 759 mm for females and 756 mm for males, values that were respectively 17-26% larger than reported for the species in northern Australia. The relatively low percentage (63%) of pregnant mature females and presence of small, similar-sized, embryos in utero in both May and November suggested a semi-synchronous, annual reproductive cycle in Moreton Bay, whereas a synchronous, biannual reproductive cycle occurred in northern Australia. It is likely that H. australiensis has a resting phase between gestation cycles at the southern-most extent of its range. For R. taylori from Moreton Bay the L s were 588 and 579 mm for females and males, respectively, values 2-3% larger than for individuals from the mid-Queensland coast and 31-35% larger than for individuals from northern Australia. The length at which 50% of the females were maternal (611 mm L ) in Moreton Bay was greater than the L , indicating that not all sharks mate immediately after maturing. Rhizoprionodon taylori in the south had an annual reproductive cycle incorporating a 7-8 month embryonic diapause, with pups probably born in February. A mean fecundity of 7·5 was almost double that reported from northern Australia. Regional variations in the reproductive characteristics of H. australiensis and R. taylori may influence their resilience to fishing and other anthropogenic pressures. The substantial differences reported here highlight the importance of region-specific life-history parameters to successful management and conservation.
澳大利亚鼬鲨（Hemigaleus australiensis）和澳大利亚尖吻鲨（Rhizoprionodon taylori）的生殖生物学差异在澳大利亚东部其分布最南端（莫顿湾）的个体与澳大利亚北部个体之间表现明显。对于来自莫顿湾的澳大利亚鼬鲨，50%个体成熟时的全长（L₅₀），雌性为759毫米，雄性为756毫米，这些值分别比澳大利亚北部该物种的报告值大17% - 26%。怀孕成熟雌性的相对低比例（63%）以及5月和11月子宫内存在小的、大小相似的胚胎，表明莫顿湾存在半同步的年度生殖周期，而澳大利亚北部则是同步的两年一次生殖周期。很可能澳大利亚鼬鲨在其分布最南端的妊娠周期之间有一个休止期。对于来自莫顿湾的澳大利亚尖吻鲨，L₅₀雌性为588毫米，雄性为579毫米，这些值比昆士兰海岸中部个体大2% - 3%，比澳大利亚北部个体大31% - 35%。莫顿湾50%雌性达到产仔状态时的长度（L₅₀为611毫米）大于L₅₀，这表明并非所有鲨鱼成熟后立即交配。南部的澳大利亚尖吻鲨有一个年度生殖周期，包括7 - 8个月的胚胎滞育期，幼鲨可能在2月出生。平均繁殖力为7.5，几乎是澳大利亚北部报告值的两倍。澳大利亚鼬鲨和澳大利亚尖吻鲨生殖特征的区域差异可能会影响它们对捕捞和其他人为压力的恢复力。这里报告的显著差异凸显了特定区域生活史参数对成功管理和保护的重要性。
