SGER: Nursery areas, natal origin, and natural elemental signatures: implications for connectivity and conservation of shark and ray populations

SGER：育苗区、出生起源和自然元素特征：对鲨鱼和鳐鱼种群的连通性和保护的影响

• 批准号: 0840860
• 负责人: Selina Heppell
• 金额: $ 14.99万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-15 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0840860&HistoricalAwards=false
• 关键词: SGER; Nursery; areas; natal; origin

The use of nursery areas is widespread among elasmobranchs (sharks and rays). The segregation of juvenile and adult habitat creates the potential for distinctive elemental compositions to be incorporated into the calcified structures of growing individuals as a result of the differing physical and chemical characteristics of these nursery areas. Distinctive ratios and combinations of elements may serve as naturally occurring markers, commonly referred to as elemental signatures, providing insight into natal origins, habitat use, dispersal, connectivity, and the extent of population mixing. However, these tools have not yet been applied to cartilaginous fishes. The objective of this investigation is to determine if elemental signatures incorporated into the vertebrae of young-of-the-year elasmobranchs reflect discrete, site-specific markers. This investigation may establish a powerful, alternative approach for research into the life history and population dynamics of this group of fishes. Elasmobranchs lack the calcified structures, known as otoliths, which are typically used for studies of dispersal and natal origin in bony fishes based on distinctive elemental signatures. The potential for metabolic activity within calcified vertebrae has raised questions about the chemical stability of these structures. Resorption or physiological reworking of this cellular matrix may alter vertebral chemical composition during the course of a lifetime and limit their usefulness as records of past physiochemical environments in which the organism lived. Before broader ecological questions may be considered based on differences in the chemical composition within cartilaginous vertebrae, key assumptions underlying the application of these techniques must be addressed.Complementary field and captive laboratory investigations will be applied to assess spatial and temporal variability of vertebral elemental signatures, relationships between water and vertebral chemical composition, and stability of these signatures through time. Specimens will be obtained from fishery landings from nursery areas along the Pacific coast of Mexico (including the Gulf of California) and Costa Rica during August-November 2008 and 2009. The distribution of the sampling locations will enable an assessment of spatial variability in elemental and isotopic signatures on the scale of 10s, 100s, and 1000s of kms across contrasting environmental and geological gradients. Study species will be opportunistically targeted to represent different life history strategies and ecomorphotypes (e.g. benthic, pelagic), but an emphasis will be focused on the collection of the commonly landed, circumglobally distributed scalloped hammerhead shark (Sphyrna lewini). The extent to which elements are discriminated against or selected for within vertebrae will be described by partition coefficients, thus enabling comparisons of vertebral chemical composition with ambient environmental concentrations.Relationships between water and vertebral chemistry and temporal stability of elemental signatures will be assessed through manipulative experiments with captive juvenile sharks or rays. Experimental treatments will include a control, and replicated conditions of three constant salinity-temperature levels. Following a period of approximately nine months, salinity-temperature treatments will be altered in each tank to simulate change into a new, contrasting environment. At the time of transfer, one tank will be assigned reduced food rations. This will provide a means of determining if physiological stress, such as an irregular or insufficient food supply, drives reworking of elements within the vertebral matrix. After nine additional months have passed, experimental specimens will be sacrificed in accordance with Institutional Animal Care and Use Committee protocol. Elemental and isotopic analyses will be conducted using Laser Ablation Inductively Coupled Plasma Mass Spectrometry for vertebral samples and a combination of Inductively Coupled Plasma Optical Emission Spectroscopy and High Resolution Inductively Coupled Plasma Mass Spectrometry for water samples. This project represents the first inquiry into the potential application of multi-elemental analysis of cartilaginous vertebrae to studies of natal origin and population connectivity. If the technique is successful, this study will propel and direct future research and provide critical details for improved management and conservation of this historically vulnerable group of fishes.

软骨鱼类（鲨鱼和鳐鱼）普遍使用育苗区。由于这些育苗区的物理和化学特性不同，幼年和成体栖息地的隔离创造了将独特的元素成分纳入生长个体的钙化结构的潜力。元素的独特比例和组合可以作为自然发生的标记，通常称为元素特征，提供对出生起源、栖息地利用、扩散、连通性和人口混合程度的深入了解。然而，这些工具尚未应用于软骨鱼类。这项研究的目的是确定纳入当年幼软骨鱼椎骨中的元素特征是否反映了离散的、特定位点的标记。这项研究可能会为研究该类鱼类的生活史和种群动态建立一种强大的替代方法。软骨鱼缺乏被称为耳石的钙化结构，耳石通常用于根据独特的元素特征研究硬骨鱼的扩散和出生起源。钙化椎骨内代谢活动的潜力引发了有关这些结构的化学稳定性的问题。这种细胞基质的吸收或生理再加工可能会在一生中改变椎骨的化学成分，并限制它们作为生物体过去生活的生理化学环境的记录的有用性。在根据软骨椎骨内化学成分的差异考虑更广泛的生态问题之前，必须解决这些技术应用背后的关键假设。将应用补充现场和实验室调查来评估椎骨元素特征的空间和时间变异性、水和椎骨化学成分之间的关​​系以及这些特征随时间的稳定性。样本将于 2008 年 8 月至 11 月和 2009 年期间从墨西哥（包括加利福尼亚湾）和哥斯达黎加太平洋沿岸的苗圃区的渔场上岸获得。采样地点的分布将能够在对比环境和地质梯度下以数十、数百和数千公里的尺度上评估元素和同位素特征的空间变异性。研究物种将有机会代表不同的生活史策略和生态形态类型（例如底栖、中上层），但重点将集中在常见陆地、全球分布的扇贝双髻鲨（Sphyrna lewini）的收集上。椎骨内元​​素被歧视或选择的程度将通过分配系数来描述，从而能够将椎骨化学成分与周围环境浓度进行比较。水和椎骨化学成分之间的关​​系以及元素特征的时间稳定性将通过对圈养的幼年鲨鱼或鳐鱼进行操作实验来评估。实验处理将包括三个恒定盐度-温度水平的对照和复制条件。经过大约九个月的时间，每个水箱中的盐度-温度处理将发生变化，以模拟进入新的、对比鲜明的环境的变化。转移时，一辆坦克的配给量将减少。这将提供一种方法来确定生理压力（例如食物供应不规律或不足）是否会驱动椎骨基质内的元素重新加工。再过九个月后，将根据机构动物护理和使用委员会的协议处死实验标本。将使用激光烧蚀电感耦合等离子体质谱法对椎骨样品进行元素和同位素分析，并结合电感耦合等离子体发射光谱法和高分辨率感应耦合等离子体质谱法对水样品进行元素和同位素分析。该项目首次探讨了软骨椎骨多元素分析在出生起源和人口连通性研究中的潜在应用。如果该技术成功，这项研究将推动和指导未来的研究，并为改善这一历史上脆弱鱼类群体的管理和保护提供关键细节。