ABSTRACT: Novel, non-lethal approaches are needed to improve our current understanding of the reproductive biology and ecology of the white shark Carcharodon carcharias. Previous studies have demonstrated that concentrations of reproductive hormones in muscle tissue can be used as reliable indicators of reproductive status for many vertebrate species, including elasmobranchs. Here, we applied this method to assess the concentrations of testosterone (T) and estradiol (E₂) in muscle biopsies from free-swimming white sharks at a known aggregation site off the coast of Cape Cod, Massachusetts (USA), in the Northwest Atlantic Ocean, to determine whether this technique could be used to evaluate the reproductive status of this species. A total of 14 muscle samples from 13 white sharks (7 males [1 sampled twice], 6 females), ranging in size from 3.3 to 4.2 m total length, were analyzed for this study. T and E₂ were present in sufficient amounts to be quantified in 7 of the 8 (87.5%) male and 1 of the 6 (16.7%) female samples, respectively. As expected, most samples collected from immature individuals were below minimum detection thresholds. Hormone concentrations in males presumed to be adults were also generally low, suggesting these individuals were not actively producing sperm at the time of sample collection. Overall, the results herein are similar to those found in other species and indicate that concentrations of hormones in the skeletal muscle of subadult and adult white sharks can provide information on the reproductive status of individuals. This technique could have wide-ranging applications for the study of white shark reproduction in the future.

中文翻译：

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利用白鲨Carcharodon carcharias肌肉中的生殖激素浓度评估西北大西洋的生殖状况

摘要：需要新颖，非致命的方法来增进我们目前对白鲨Carcharodon carcharias的生殖生物学和生态学的理解。先前的研究表明，肌肉组织中生殖激素的浓度可以用作许多脊椎动物物种（包括弹性分支）生殖状况的可靠指标。在这里，我们采用这种方法评估睾丸激素（T）和雌二醇（E ₂）在西北大西洋马萨诸塞州科德角（美国）沿海一个已知聚集地自由游动的白鲨的肌肉活组织检查中，以确定该技术是否可用于评估该物种的繁殖状况。这项研究共分析了来自13条白鲨的14份肌肉样本（7头雄性鱼（两次采样1次），6例雌鱼），大小从3.3到4.2 m不等。T和E ₂样品中的8种（分别为8种（87.5％）男性）和6种（16.7％）女性样本中的1种足以定量。不出所料，从未成熟个体收集的大多数样品都低于最低检测阈值。一般认为成年男性中的激素浓度也普遍较低，这表明这些人在采集样本时并未积极产生精子。总的来说，本文的结果与在其他物种中发现的结果相似，表明亚成年和成年白鲨的骨骼肌中激素的浓度可提供有关个体生殖状况的信息。这项技术将来可能在白鲨繁殖研究中有广泛的应用。