Juvenile salmon diet from F/V Great Pacific, R/V Miller Freeman GP0108, GP0207-01, MF0310 in the Coastal Gulf of Alaska, Northeast Pacific from 2001-2003 (NEP project)

<p><strong>GLOBEC 2000: Factors Affecting the Distribution of Juvenile Salmon in the Gulf of Alaska</strong><br /> <em>J. Helle (NMFS/AFSC, Auke Bay Laboratory)</em><br /> <em>E. D. Cokelet (Pacific Marine Environmentla Laboratory),<br /> E. V. Farley, Jr. (NMFS/AFSC, Auke Bay Laboratory),<br /> A. B. Hollowed (NMFS/AFSC),<br /> P. J. Stabeno (Pacific Marine Environmental Laboratory)</em></p> <p>\"Remarkable changes in atmospheric, oceanic and biological conditions have occurred in recent decades in the North Pacific Ocean including declines in the marine survival of some salmon stocks. Fishery scientists generally agree that in the first few months after leaving freshwater, salmon survival and growth are linked to oceanic variability. The purpose of this research is to focus National Marine Fisheries Service studies on the GLOBEC region, augment oceanographic measurements and determine what biological and physical factors influence the distribution of juvenile salmon. Three general hypotheses are explored in this proposal: (1) juvenile salmon prefer the buoyancy-driven Alaska Coastal Current (ACC) at the head of the Gulf of Alaska, (2) they associate with oceanic temperature, salinity, current and prey fields, and (3) they migrate landward of Kodiak Island in the ACC rather than seaward in the Alaskan Stream. Annual, summer cruises aboard a chartered fishing vessel will catch juvenile salmon on 10 transects between Yakutat Bay and Kodiak Island. The vessel will be outfitted with a thermosalinograph to measure sea-surface temperature and salinity, and with an Acoustic Doppler Current Profiler (ADCP) - each operating continuously for fine-scale resolution. Modeled tidal currents will be removed from ADCP measurements to reveal the mean flow fields. At each trawl site, temperature and salinity profiles will provide water-column properties, and bongo-net hauls will give zooplankton distributions. Stomach samples from juvenile salmonids will be analyzed in the laboratory for diet composition and compared with zooplankton distributions. Analysis of salmon otoliths for hatchery thermal marks and Genetic Stock Identification techniques will be used to determine the home stream of hatchery and wild stocks in the Gulf of Alaska and their distribution with respect to oceanographic regimes. Retrospective analysis of catch per unit effort versus oceanographic and prey factors will reveal what affects the distribution of pink, chum, coho and sockeye salmon in the study region. Proxies for bio-physical factors will be developed and compared with salmon-run size.\"<em>(project proposal)</em></p> <p><strong>Data Collection Details:</strong><br /> Types: CTD profiles, ADCP profiles of ocean current, juvenile salmonid catch statistics from trawls, salmonid stomach samples analyzed for diet composition, salmonid otolith analyses, Genetic Stock Identification, zooplankton distributions from bongo-net hauls<br /> Platform: Chartered fishing vessel<br /> Spatial extent: 10 transects perpendicular to the coast between Yakutat Bay and Kodiak Island<br /> Temporal extent: ~2 weeks each July-August of 2001-2004.</p>**GLOBEC 2000：阿拉斯加湾幼鲑分布的影响因子** *J. 赫勒（NMFS/AFSC，奥克湾实验室（Auke Bay Laboratory））* *E. D. 科克莱特（太平洋海洋环境实验室（Pacific Marine Environmental Laboratory）），<br>小E. V. 法利（NMFS/AFSC，奥克湾实验室（Auke Bay Laboratory）），<br>A. B. 霍洛德（NMFS/AFSC），<br>P. J. 斯坦本诺（太平洋海洋环境实验室（Pacific Marine Environmental Laboratory））* “近几十年来，北太平洋的大气、海洋与生物环境发生了显著变化，部分鲑鱼种群的海洋存活率出现下降。渔业科学家普遍认为，鲑鱼在脱离淡水后的最初数月内，其存活与生长与海洋环境变异密切相关。本研究旨在将美国国家海洋渔业局（NMFS）的研究聚焦于GLOBEC研究区域，扩充海洋学观测项目，并明确哪些生物与物理因子会影响幼鲑的分布。本提案将探讨三项核心假说：（1）幼鲑偏好栖息于阿拉斯加湾头部由浮力驱动的阿拉斯加沿岸流（Alaska Coastal Current, ACC）；（2）幼鲑的分布与海洋温度、盐度、海流及饵料场相关；（3）幼鲑会沿阿拉斯加沿岸流（ACC）向科迪亚克岛近岸洄游，而非沿阿拉斯加海流向外海迁移。 本研究将每年夏季租用捕捞渔船，在雅库塔特湾与科迪亚克岛之间的10条断面上采集幼鲑样本。作业船将配备温盐测量仪（thermosalinograph）以连续测量海表温度与盐度，同时搭载声学多普勒流速剖面仪（Acoustic Doppler Current Profiler, ADCP）以获取高分辨率的连续观测数据。研究人员将从ADCP观测数据中扣除模拟潮汐流，以得到平均流场。在每个拖网采样站点，将通过温盐剖面测量获取水柱环境参数，并使用邦戈网（bongo-net）采集浮游动物样本以得到其分布情况。实验室将分析幼鲑胃含物样本以确定其饮食组成，并将其与浮游动物分布进行比对。此外，将通过鲑鱼耳石（otoliths）的孵化场热标记分析与遗传种群鉴定技术（Genetic Stock Identification），确定阿拉斯加湾内孵化场繁育种群与野生种群的原产地溪流，并明确其与海洋环境格局的分布关联。通过回溯分析单位捕捞努力量渔获量与海洋环境及饵料因子的相关性，以明确研究区域内粉鲑、狗鲑、银鲑与红鲑的分布影响因子。本研究还将构建生物物理因子替代指标，并与鲑鱼洄游种群规模进行比对。”*(项目提案)* **数据采集详情：** *数据类型：* CTD剖面、海流ADCP剖面、拖网获取的幼鲑类渔获统计、用于饮食组成分析的鲑科鱼类胃样本、鲑鱼耳石分析、遗传种群鉴定、邦戈网采样获取的浮游动物分布数据 *作业平台：* 租赁捕捞渔船 *空间范围：* 雅库塔特湾与科迪亚克岛之间的10条垂直于海岸的断面 *时间范围：* 2001-2004年每年7-8月，每次作业时长约2周。