Americas Program Dissertation Enhancement: The Importance of Colorado River Flow to Endemic Fish of the Northern Gulf of California: Evidence from Stable Isotopes in Fish Otoliths

0323139flessa这个美洲项目论文增强项目将支持Kirsten Rowell在亚利桑那大学Karl Flessa博士的指导下进行论文研究。这项研究将与墨西哥恩塞纳达下加利福尼亚自治大学的Conal True博士合作，旨在通过研究在大多数鱼头部（耳石）中发现的小结构中的同位素变化，将水和食物中的氧和碳含量联系起来。在上游水坝和引水之前，科罗拉多河是加利福尼亚湾北部栖息地的主要影响因素。据推测，河流调节和蓄水改变了河口栖息地，对两种特有鱼类产生了负面影响。本研究的具体目标包括：1)对比研究由耳石中氧和碳稳定同位素记录的坝前和坝后环境条件；2)两种鱼类在筑坝前和筑坝后的生长速率比较；3)两种鱼类在坝前和坝后标本的栖息地、产卵时间和产卵频率的比较。通过使用储存在鱼石中以稳定的氧和碳同位素、生长增量和产卵频率形式的基线数据，本研究将大大加强女研究生的论文研究，启动与墨西哥同事的国际合作，并为渔业管理人员提供检测和测量食物网和栖息地长期历史变化的技术。本论文强化项目由美国国家科学基金会美洲项目和地理与区域科学项目共同资助。

0323139FlessaThis Americas Program thesis enhancement project will support thesis dissertation research by Kirsten Rowell under the supervision of Dr. Karl Flessa of the University of Arizona. The research, which will involve collaboration with Dr. Conal True of the Universidad Autonoma de Baja California, Ensenada, Mexico, aims to correlate oxygen and carbon content with water and food by studying their isotopic variation in small structures found in the head of most fish (otoliths). Before upstream dams and water diversion, the Colorado River was a major influence on northern Gulf of California habitats. River regulation and impoundment are hypothesized to have altered the estuarine habitat, negatively affecting two endemic fish types. Specific goals of this study include: 1) comparison of the pre-dam and post-dam environmental conditions recorded by the stable isotopes of oxygen and carbon in the otoliths; 2) comparison of growth rates in pre-dam and post-dam specimens of both fish species; and 3) comparison of the habitat, timing and frequency of spawning in pre-dam and post-dam specimens of the two species of fish. By using baseline data stored in fish otoliths in the forms of stable isotopes of oxygen and carbon, growth increments, and spawning frequencies, this study will significantly enhance the dissertation research of a female graduate student, initiate international collaboration with a Mexican colleague, and provide fisheries managers with techniques to detect and measure long-term historical changes in food webs and habitats. The Americas Program and the Geography and Regional Science Program of NSF are jointly supporting this thesis enhancement project.