GLOBEC: Growth and Survival of Juvenile Salmon

自20世纪80年代以来，加州洋流系统（CCS）的鲑鱼数量，尤其是鳕鱼的数量急剧下降，与1977年的政权转变相吻合，与阿拉斯加湾创纪录的生产力形成鲜明对比。海洋学变化与海洋中鲑鱼生存之间的具体联系。对环境的了解还不够充分。GLOBEC选择比较由俄勒冈州布兰科角（北纬43度）划分的北加州洋流的两个区域，在那里有一股“上升流射流”从大陆架上移动。布兰科角北部和南部地区在上升流的强度和稳定性、温度和海上运输方面存在差异。有证据表明，由于自然条件的原因，布兰科角北部和南部的生物群分布和生产可能有所不同，这为比较和对比特定海洋过程与生物生产力之间的关系提供了机会。调查人员将使用过程导向研究来检查与生境质量有关的物理和生物过程之间的机制联系，生境质量对幼鲑鱼的招募至关重要。在2000年5 / 6月和2002年9月期间，我们将在加州尤里卡至俄勒冈州纽波特之间的横断面上采集幼鱼（Oncorhynchus kisutch）和奇努克鲑鱼（Oncorhynchus tshawytscha）。抽样工作将与其他GLOBEC研究人员在同一区域内进行的中尺度和精细尺度的物理（例如，漩涡、锋面、上升流、近海运输进口的位置；混合层深度、海面温度、混合层深度）和生物（主要和次要生产力的面积和密度）特征调查同时进行。鲑鱼研究人员将测量幼鲑鱼的生长速度、大小变异性、生物能量状况、病原体流行率和强度，作为生存条件。通过将北部CCS的指数与营养关系研究相关联，他们将检验这样一种假设：通过“自下而上”的力量，导致低营养水平的高生产力的海洋学特征转化为更高的生长速度、条件和更多的鲑鱼繁殖。此外，这些指标与幼鱼体内同位素天然丰度（14C, 13C, 15N）变化的相关程度将用于直接检验饮食特异性和垂直海洋平流影响幼鱼健康和状况的假设。研究人员还将比较东北太平洋不同地区（如阿拉斯加、不列颠哥伦比亚省、华盛顿和俄勒冈州北部）的幼鱼和奇努克鲑鱼的生长和状况，并在可用和适用的情况下与历史记录（上次政权转变之前）进行比较。这些结果将在时间（年代际）和空间（流域、中尺度和局地）尺度上提供海洋变异与鲑鱼幼鱼存活之间关系的信息。

RauSalmon populations in the California Current System (CCS), and coho salmon in particular, have been in severe decline since the 1980s, coinciding with the 1977 regime shift, and in contrast to record productivity in the Gulf of Alaska. The specific linkages between oceanographic changes and salmon survival in the marine.enviromnent are not well understood. GLOBEC has chosen to compare two regions of the Northern California Current divided by Cape Blanco, Oregon (43 degrees N) where an "upwelling jet" moves off the shelf. The regions north and south of Cape Blanco differ in intensity and stability of upwelling, temperature, and offshore transport. Evidence indicates that due to the physical conditions, the distribution and production of biota may differ north and south of Cape Blanco, providing the opportunity to compare and contrast the relationship between specific oceanographic processes and biological productivity. The investigators will use process oriented studies to examine mechanistic linkages between the physical and biological processes that are associated with habitat quality critical to recruitment of juvenile salmon. Juvenile coho (Oncorhynchus kisutch) and chinook (Oncorhynchus tshawytscha) salmon will be collected along transects between Eureka, CA to Newport, OR during May/June and September of 2000 and 2002. Sampling efforts will coincide with mesoscale and fine-scale surveys of physical (e.g., location of eddies, fronts, upwelling, offshore transport import; mixed layer depth, sea surface temperature, mixed layer depth) and biological (areas and density of primary and secondary productivity) features within the same regions conducted by other GLOBEC researchers. The salmon investigators will measure the growth rate, size variability, bioenergetic condition, pathogen prevalence and intensity in juvenile salmon as conditions of survival. By correlating indices in the Northern CCS with the trophic relationship studies, they will test the hypotheses that oceanographic features leading to high productivity of lower trophic levels translates to higher growth rates, condition and greater salmon recruitment through "bottom-up" forces. Also, the degree of correlation between these indices and variations in isotope natural abundances (14C, 13C, 15N) in juvenile salmon will be used to directly test the hypothesis that diet specificity and vertical ocean advection affect juvenile salmon health and condition. The investigators also will compare juvenile coho and chinook slamon growth and condition from different regions of the Northeast Pacific (e.g., Alaska, British Columbia, Washington and northern Oregon) and to the historical record (prior to the last regime shift) where available and applicable. These results will provide information on the relationships between ocean variability and juvenile salmon survival on temporal (interdecadal) and spatial (basin-wide, mesoscale, and local) scales.