Intraspecific variability in life-history patterns is well documented in elasmobranchs, and defining regionally specific parameters is essential for proper management and sustainability of species. Studies on the reproductive biology of finetooth sharks (Carcharhinus isodon) have noted a potential disparity in periodicity within North American waters. To better define regional variability, the current study collected 1490 finetooth sharks (831 female, 659 male) from the northern Gulf of Mexico. The size-at-maturity was determined to be 995- and 961-mm fork length for females and males respectively. In males, the peak gonadosomatic index (GSI) in March and presence of semen in the seminal vesicles in April suggested spermatogenesis occurs from March to April. In females, ovulation occurred from May to June, with a peak GSI occurring in May and maximum vitellogenic follicle diameter occurring in May and June. Gestation was found to be 11–12 months, with parturition occurring in May and June and a mean brood size was 3.8±0.1 embryos. Of the 50 females examined during the ovulatory period, 32 exhibited annual and 18 exhibited biennial reproductive periodicity. The results from this study will be impactful, because regionally distinct reproductive parameters can now be considered for future assessments.

中文翻译：

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墨西哥湾北部细齿鲨（Carcharhinus isodon）的生殖生物学，有一年和两年繁殖的证据

生活史模式的种内变异在 elasmobranchs 中有很好的记录，并且定义区域特定参数对于物种的适当管理和可持续性至关重要。对细齿鲨（Carcharhinus isodon）生殖生物学的研究发现，北美水域的周期性存在潜在差异。为了更好地定义区域变异性，目前的研究从墨西哥湾北部收集了 1490 条细齿鲨（831 条雌性，659 条雄性）。雌性和雄性的成熟尺寸分别确定为 995 和 961 毫米的叉长。在男性中，3 月的性腺体指数 (GSI) 峰值和 4 月精囊中的精液表明精子发生发生在 3 月至 4 月。在女性中，排卵发生在 5 月至 6 月，GSI 峰值出现在 5 月，卵黄卵泡直径最大出现在 5 月和 6 月。发现妊娠期为 11-12 个月，分娩发生在 5 月和 6 月，平均育雏大小为 3.8±0.1 个胚胎。在排卵期检查的 50 只雌性中，32 只表现出一年一次的生殖周期，18 只表现出两年一次的生殖周期。这项研究的结果将具有影响力，因为现在可以在未来的评估中考虑区域不同的生殖参数。