Spatial distribution of Greenland halibut Reinhardtius hippoglossoides in relation to abundance and hypoxia in the estuary and Gulf of St. Lawrence

Annual bottom‐trawl surveys (1990–2010) were used to examine associations between environmental conditions, spatial distribution, and size‐specific abundance of Greenland halibut Reinhardtius hippoglossoides in the estuary and Gulf of St. Lawrence (EGSL), and to test the influence of hypoxic conditions on habitat selection. Size classes representing juvenile, immature and adult fish were used for the analyses. The highest concentrations of fish were found in the St. Lawrence estuary at both high and low levels of stock abundance. The areas occupied by 50, 75, and 95% of juvenile fish expanded with higher population abundance. However, contrary to our predictions, densities in marginal habitats did not increase at a higher rate than in optimal habitats. Fish longer than 32 cm were distributed over a broader area than juvenile fish. Their abundance explained a limited proportion of the variability in spatial distribution. The spatial dynamics of Greenland halibut in the EGSL is best described by a proportional density model where the rate of increase in local density is associated with population abundance. Habitats selected by Greenland halibut were characterized by low dissolved oxygen (DO) levels. The strong association between high fish densities and low DO concentrations indicates a high tolerance of Greenland halibut to hypoxia. It also indicates that negative effects, if present, could be compensated by other factors such as food availability and/or refuge from predation. The results of this study also clearly define the St. Lawrence estuary as the major nursery area for the EGSL population.     

Habitat use of cownose rays (Rhinoptera bonasus) in a highly productive,hypoxic continental shelf ecosystem

Highly productive surface waters and hypoxic (dissolved oxygen, DO ≤ 2.0 mg L^?1) bottom waters develop seasonally on the northwestern Gulf of Mexico continental shelf due to nutrient and freshwater inputs from the Mississippi‐Atchafalaya River system. We investigated the spatial distribution of the cownose ray (Rhinoptera bonasus), a highly mobile, bentho‐pelagic species that is a seasonal resident of the shelf, in relation to surface chlorophyll, bottom‐water hypoxia, and other environmental variables (salinity, temperature, depth). We used synoptic trawl and aerial surveys to investigate ray distributions at both shelfwide (100–1000s km) and local (5–50 km) spatial scales. Shelfwide sampling indicated that rays were associated with regions of high surface chlorophyll and low bottom salinity and DO, conditions characterizing the Mississippi‐Atchafalaya plume region. Local sampling in and around the hypoxic zone indicated that rays preferred habitats where bottom waters were hypoxic but they primarily occupied normoxic (DO > 2.0 mg L^?1) waters above the bottom hypoxic layer. Stomach fullness and diet composition were similar between rays sampled in habitats with hypoxic versus normoxic bottom waters. These results indicate that cownose rays are strongly associated with riverine‐influenced regions of the shelf and preferentially use habitats with hypoxic bottom waters, perhaps for benthic foraging. Collectively, our results highlight the importance of considering the responses of mobile species to enhanced productivity and to hypoxia‐induced habitat degradation, which are both the products of coastal eutrophication.     

环境因子对东南太平洋智利竹䇲鱼渔场时空分布异质性影响

基于2012—2018 年4—8 月我国东南太平洋智利竹?鱼 (Trachurus murphyi) 渔捞日志数据,应用地理权重回归模型 (GWR) 探究智利竹?鱼渔场资源分布与环境因子的空间异质性关系.结果表明,环境因子海面温度基于GWR 模型回归的拟合优度为0.54,校正的拟合优度为0.34,赤池信息准则 (Aka...     

柘林湾网箱养殖海域溶解氧分布及其影响因素

根据１９９８年７月在南海东北部柘林湾的调查数据，探讨网箱养殖海域溶解氧的分布及其与其他环境因子间的关系，结果显示夏季海水溶解氧浓度为３.03-7.86mg/L( 平均５．３０）,退潮时（平均５.71)高于涨潮时（平均４.65)涨潮时网箱区内贫氧（ ＜０．mg/L).多元逐步回归分析表明，对溶解氧浓度有重要影响的水质因子为pH和水温，其次为盐度，ＣＯＤ和营养盐，它们的变化与ＤＯ的变化有较好的相关性，区域比较表明，海水溶解氧浓度与观测僧置到网箱区的距离呈正相关（Ｐ＜０．０２），与底质硫物，ＰＯ４－Ｐ含量呈负相关（Ｐ＜０．０５）,溶解氧浓度偏低与养殖环境的污染有直接关系。     

基于结构方程模型研究环境因子对毛里塔尼亚双拖鲣CPUE的影响

探索渔业资源丰度与环境因子的关系, 并掌握种群分布对环境变化的响应机制, 是养护资源、实现渔业可持续发展的基础。然而, 渔业资源的变化受多个环境因素的综合影响, 这些因素之间存在复杂且相关的关系。目前的研究主要集中于环境因子对种群分布和资源丰度等直接影响, 而忽视了环境因素之间的相互作用。为了探索不同环境因子及其相互关系对毛里塔尼亚双拖鲣种群资源量的影响机制与路径, 本研究基于 2017—2019 年毛里塔尼亚海域双拖渔业鲣(Katsuwonus pelamis)单位捕捞努力量渔获量(CPUE), 采用结构方程模型(SEM)构建海表面温度 (SST)、海表面盐度(SSS)、海面高度异常(SLA)、溶解氧(DO)和叶绿素 a 浓度(Chl-a) 5 个环境因子对鲣 CPUE 直接和间接影响。结果表明: SEM 模型具有良好的拟合效果; SST、SSS、SLA、DO 和 Chl-a 对鲣 CPUE 均有直接影响, 其中 DO 和 SLA 对 CPUE 有着显著正相关影响, 而 SST、SSS 和 Chl-a 对 CPUE 有显著负相关影响; SST 等环境因子还会通过多种路径对鲣 CPUE 产生间接影响。研究揭示了毛塔海域 SST 通过直接影响或通过影响其他环境因子而间接影响鲣种群资源变动的潜在机制。     

大鹏澳养殖水域溶解氧的变化及其与生态结构的关系

根据2001年6月至2002年6月大鹏澳网箱养殖水域周年的溶解氧(DO)水平监测数据,阐述网箱养殖区水体DO的水平、季节的变化、垂直变化和网箱养殖水体DO质量评价以及DO与水环境因子的相关性。结果表明,大鹏湾网箱养殖水域DO周年水平为3 86～8 01mg/L,氧饱和度为51 6%～103 6%,养殖水域DO水平低于非养殖水域的;冬、春季DO水平较高,均符合我国渔业水质标准要求。夏季DO水平普遍较低,超标率为95%;表层水DO水平略高于底层水,DO水平超标率分别为46%和66 7%;DO水平(全年)与pH值、盐度、叶绿素水平均呈显著性正相关(P<0 02,n=32),与水温、无机磷和无机氮水平呈显著性负相关(P<0 02,n=32)。其中,在春季相关最为明显。     

带鱼保护区春秋季鱼类群落特征及与环境因子的关系

基于2014年5月(春季)和11月(秋季)在带鱼保护区进行的渔业资源底拖网调查数据,采用非度量多维标度(NMDS)、典范对应分析(CCA)和分类回归树(CART)方法研究了带鱼保护区春、秋季鱼类群落空间结构和群落多样性,以及它们与环境因子的关系。结果显示,该水域春季共捕获鱼类75种,隶属14目49科63属;秋季捕获鱼类78种,隶属15目50科64属。春、秋两季鱼类空间结构均可划分为2个组群,经单因子相似性(ANOSIM)分析,不同季节的2个组群间均存在显著性差异。CCA分析表明,影响春、秋季鱼类群落分布的主要环境因子有温度、盐度、水深以及浮游动物。春季多样性指数平均值为1.65±0.60,丰富度指数为2.46±0.90,秋季多样性指数平均值为1.42±0.53,丰富度指数为1.89±0.60。CART分析表明,影响春季多样性和丰富度的主要因素有Chl.a、DO、水深、p H和浮游动物(磷虾类和浮游幼体);秋季多样性主要受温度、水深和盐度的影响,丰富度主要受水深和温度的影响。     

Climate effects and bottom‐up controls on growth and size‐at‐age of Pacific halibut (Hippoglossus stenolepis) in Alaska (USA)

Pacific halibut (Hippoglossus stenolepis) are an ecologically, commercially, and culturally important Alaskan groundfish species. Commercial harvest of halibut dates back to the late 19th century and has been managed by the International Pacific Halibut Commission (IPHC) since 1921. IPHC surveys have revealed declining trends in survey biomass in multiple regions and region‐specific declines in mean size‐at‐age (size‐at‐age) over the past two decades (>50% in some areas). Changes in size‐at‐age can arise from a variety of physical, ecological, sampling, and fishery effects, including size‐dependent fishery or predation mortality, alteration in growth from variability in prey quality or quantity, and changes in temperature‐dependent metabolic demands. Here, we develop and apply a bioenergetics model for halibut using survey‐based diet and temperature data for Alaska to evaluate potential environmental drivers of size‐at‐age. In general, juvenile (<40 cm fork length) foraging rates were highest in the Gulf of Alaska concomitant with higher potential growth and elevated basal metabolic demands during warm summer conditions. In contrast, adult (40–120 cm FL) potential growth was highest in the Eastern Bering Sea, potentially reflecting lower metabolic costs and higher rates of prey consumption in that region. We additionally find evidence for interannual variation in potential growth, with a higher frequency of reduced growth potential in the last decade, particularly in the Eastern Bering Sea in 2015 and 2016 for both juvenile and adult halibut. These results suggest the potential for patterns in size‐at‐age to arise from trophic and environmental constraints that collectively limit growth in some regions and years.     

以优化的BP神经网络模型为基础研究山东近海口虾蛄空间分布与环境因子的关系

BP神经网络模型作为一种常用的机器学习方法,被广泛应用于物种分布模型,以解析生物分布与环境因子的关系。与传统回归模型相比,该模型可以灵活处理变量间的非线性关系,但其结构复杂,在参数设置方面存在不确定性,从而影响模型的预测与应用。根据2016—2017年山东近海口虾蛄渔业资源调查与环境数据,利用BP神经网络模型构建口虾蛄资源分布模型,同时利用数据分组处理算法(group method of data handling, GMDH)、遗传算法(genetic algorithm, GA)和自适应算法(adaptive algorithm)分别对模型输入变量、初始权值和隐节点数目3方面进行优化,构建7种不同组合优化模型。结果显示,7种模型的优化效果存在明显差异,单方面和两方面组合优化模型预测性能基本保持一致;而三方面共同优化其均方根误差与残差平方和分别为0.35和1.94,较初始模型的0.52和2.40更小,且相关系数最大为0.45,表明模型优化效果最好。对比优化前后发现,口虾蛄资源密度随纬度和底层盐度变化趋势基本保持一致,而随底层温度的升高,口虾蛄资源密度存在较大差异。此外,最优模型较初始模型增加水深为关键环境因子,对口虾蛄的资源密度具有重要影响。本研究进一步开发了BP神经网络模型参数优化的方法,证明了参数优化对BP模型的预测性能具有重要影响,模型优化对于分析口虾蛄资源密度与环境因子的关系具有重要意义。     

杭州湾—舟山近海春季游泳动物群落结构及与环境因子的关系

杭州湾—舟山近海是许多经济鱼类的传统产卵地和栖息地,环境因子对鱼类群落结构的影响非常显著。本研究根据2016年春季在杭州湾—舟山近海的80个站位的底拖网调查数据,分析了鱼类及大型甲壳类群落数量和平均个体大小的空间分布,并根据典范对应分析法(CCA)研究了鱼类及大型甲壳类主要类群的特征(丰度和个体大小)与环境因子的关系。结果显示,游泳动物可分为5大类群(六丝钝尾虾虎鱼、底层鱼、中上层鱼、虾、蟹),每种类群的丰度平均分别为546、213、83、316和15个/h,平均个体大小分别为0.29、2.19、4.96、0.36和6.66 g/个。根据各类群的丰度、底温、底盐及表层浑浊度,将整个海域分为杭州湾内和舟山近海水域,绝大部分类群的丰度具有显著的区域差异性,而绝大部分类群的个体大小没有区域差异性。受到浑浊度、外海水团交汇的影响,绝大部分类群主要聚集在舟山近海的高生产力水域。CCA分析表明,2个轴的环境因子能解释丰度总变异的25%,而仅能解释个体大小总变异的11.7%,说明环境因子对于鱼类及甲壳类的类群的数量空间分布具有较大影响,而对于个体大小的分布影响较小。     

中西太平洋金枪鱼围网渔业鲣鱼资源的时空分布

鲣 (Katsuwonus pelamis) 是中西太平洋金枪鱼围网捕捞的重要资源,其资源分布受环境影响明显。为探索环境对鲣渔获率影响的空间异质性特征,利用中西太平洋渔业委员会 (Western and Central Pacific Fisheries Commission, WCPFC) 所公布的2005—2019年中西太平洋金枪鱼围网综合的1°×1°渔业及海洋环境数据,对标准化后的环境因子及渔获率选用多尺度地理加权回归 (Multi-scale Geographically Weighted Regression, MGWR) 方法进行研究。结果表明：1) 与传统广义加性模型 (Generalized Additive Model, GAM) 相比,考虑环境影响空间异质性问题的地理加权回归模型 (Geographically Weighted Regression, GWR) 和MGWR拟合优度 (R²) 有明显提升,校正后拟合优度 (Adjusted R²) 分别为0.273、0.846和0.871,且拟合结果的空间分布形态更符合真实情况。2) 各环境因子对鲣资源分布存在显著的空间非平稳性影响。各海洋环境因子对鲣渔获率分布影响的空间异质性程度 (各环境变量变异系数大小) 依次为水下55 m东西向海流速度 (Sea water X velocity at 55 m depth, U55)>海表面温度 (Sea surface temperature, SST)>净初级生产力 (Net primary productivity, NPP)>100 m盐度 (Sea water salinity at 100 m depth, S100)>55 m南北向海流速度 (Sea water Y velocity at 55 m depth, V55)。3) 各环境因子的影响存在明显尺度效应差异,NPP的作用尺度为44,其次为S100和U55 (均为48),SST的为54,V55为全局尺度。4) 总体上,S100、NPP、SST、V55和U55对鲣渔获率正向影响比例依次为73.5%、64.8%、66.8%、80.8%和32.3%;其中S100、NPP和SST对鲣渔获率空间分布的影响相似,具体表现为东西向差异,170°E以西主要为正向影响,170°E以东为负向影响;U55为负向影响为主的因子。

     

利用时空物种分布模型研究海州湾大泷六线鱼的时空分布

为了解海州湾大泷六线鱼时空分布特征及其影响因素，根据2013—2019年秋季在海州湾开展的底拖网渔业资源调查和环境观测数据，构建了时空物种分布模型(spatio-temporal species distribution models)，分析其分布与环境因子的关系，通过残差分析比较其与广义加性模型的残差独立性和异质性，运用交叉验证检验模型预测性能，最终结合delta方法对其分布进行预测并计算栖息地适宜性指数(habitat suitability index, HSI)和资源分布重心。时空模型的偏差解释率为65.50%，模型分析表明，影响大泷六线鱼资源分布最主要的环境因子为水深(22.11%)，其次为底层水温(12.98%)，底层盐度(0.09%)的影响较小，水深与其分布存在正向相关性，底层水温与其分布存在负向相关性，底层盐度与其分布存在弱正向线性关系。时空模型的残差独立性和异质性较GAM更强，其交叉验证回归线斜率为0.90±0.38。模型预测结果表明，大泷六线鱼主要分布在34.5°N以北，120.0°E以东的海域，其栖息地适宜性指数的高值区域呈现逐年收缩的趋势，资源分布重心呈现向东北...     

Dynamic changes in American lobster suitable habitat distribution on the Northeast U.S. Shelf linked to oceanographic conditions

American lobster (Homarus americanus) supports one of the most valuable regional fisheries in the United States, with its abundance and distribution profoundly influenced by environmental conditions. To explain how lobster distribution has changed over time and assess the role of environmental variables on these changes, we used random forest classification and regression tree models to estimate occupancy and biomass in two seasonal periods. The occupancy models were fit to static and dynamic variables, which yielded model fits with AUC scores of 0.80 and 0.78 for spring and fall, respectively. Biomass models were fit with the same data and resulted in models explaining 61% and 63% of the spring and fall biomass variance, respectively. Significant variables scored in the formation of the regression trees were secondary productivity (i.e., zooplankton), bathymetry characteristics, and temperature. American lobster suitable habitat has changed regionally; habitat has increased in the Gulf of Maine and declined in Southern New England. There is also evidence of declining habitat along the inshore margin of the Gulf of Maine, which has been accompanied by a shift in occupancy probability offshore. Habitat suitability results from the random forest models provide insights on the structure and function of lobster habitat and context to understand recent population trends.     

Habitat preferences of selected demersal fish species in the Bay of Biscay and Celtic Sea, North-East Atlantic

According to the Ideal Free Distribution theory, individual fish are distributed where environmental conditions are optimal, and the occupied area may vary with population abundance. Thus, observed distributions are a combination of habitat suitability and density-dependent effects. Data from an annual bottom trawl survey taking place in autumn were used to assess associations between the distributions of eight demersal fish species, separately for juveniles and adults, and habitat characteristics (depth, temperature and salinity) in the Bay of Biscay and Celtic Sea. Cumulative distribution functions were used to describe the general frequency distributions of environmental variables and their relationships with fish density. During the period 1992–2006, observed bottom temperatures fluctuated with no time trend (ΔT = 8°C in the first 80 m) and population abundances varied significantly. Juvenile hake, poor cod, blue whiting, adult red gurnard, adult megrim, and lesser-spotted dogfish were found to be significantly associated with specific depth ranges. Associations with bottom temperature and salinity were weaker. For some species, preferred environmental conditions changed over time, independently of variations in environmental conditions. In general, most species seemed to be able to cope with the experienced range of conditions. Habitat associations were not influenced by abundance variations. Fluctuating abundances had an impact on spatial occupation only for red gurnard adults, lesser-spotted dogfish and blue whiting juveniles, independent of absolute densities.     

海州湾双斑蟳栖息分布特征与环境因子的关系

为了解双斑蟳栖息分布规律,实验根据2011—2016年多个季度航次在海州湾进行的渔业资源和环境调查数据,采用广义线性模型(GLM)、广义可加模型(GAM)以及随机森林3种物种分布模型(SDMs)方法,结合AIC(akaike information criterion)准则、累积偏差解释率和交叉检验等评判指标筛选和构建了双斑蟳栖息分布模型,并分析了环境因子对双斑蟳分布的影响。结果显示,3种模型在解释因子与响应变量间的关系上基本一致;其中GAM在模型拟合上具有优势,而随机森林的预测性能明显高于传统的GLM和GAM。双斑蟳相对渔获量在年份和月份间的变异性最为显著,两个因子的解释率分别在18%和3.8%以上。水深和表层盐度对双斑蟳资源分布的影响较大,均与双斑蟳相对丰度呈正相关关系;双斑蟳分布总体呈现冬季相对较高,夏季东北部海域高、西南部低的特点,与海州湾水深分布特点基本一致。本研究还根据FVCOM(finite-volume coasta ocean model)模拟环境数据,利用随机森林分布模型估计了双斑蟳在海州湾海域2011年各个季节的空间分布,为渔业资源的开发和保护提供依据。     

Occurrence of demersal fishes in relation to near‐bottom oxygen levels within the California Current large marine ecosystem

Various ocean‐climate models driven by increased greenhouse gases and higher temperatures predict a decline in oceanic dissolved oxygen (DO) as a result of greater stratification, reduced ventilation below the thermocline, and decreased solubility at higher temperatures. Since spreading of low oxygen waters is underway and predicted to increase, understanding impacts on higher trophic levels is essential. Within the California Current System, shoaling of the oxygen minimum zone (OMZ) is expected to produce complex changes. Onshore movement of the OMZ could lead to habitat compression for species with higher oxygen requirements while allowing expansion of species tolerant of low bottom DO. As part of annual groundfish surveys, we sampled catch across a range of conditions from the upper to the lower limit of the OMZ and shoreward across the continental shelf of the US west coast. DO ranged from 0.02 to 4.25 mL L^?1 with 642 stations (of 1020 sampled) experiencing hypoxic conditions in 2008–2010. Catch and species richness exhibited significant and positive relationships with near‐bottom oxygen concentration. The probability of occurrence was estimated for four species (spotted ratfish, petrale sole, greenstriped rockfish and Dover sole) using a binomial Generalized Additive Model. The models for each species included terms for position, day of the year, salinity, near‐bottom temperature and the interaction term between depth and near‐bottom DO. Spotted ratfish and petrale sole were sensitive to changes in near‐bottom oxygen, while greenstriped rockfish and Dover sole show no changes in probability of occurrence in relation to changes in oxygen concentration.     

2017—2018年长江口海域夏季浮游动物群落的年际变化及影响因素

根据2017―2018年夏季长江口海域浮游动物连续站及断面站的数据,应用典范对应分析（CCA）研究了浮游动物的种类组成、主要类群数量年际变化、昼夜变化、空间变化及与环境因子的关系。结果显示,2017年和2018年夏季分别鉴定浮游动物49种和50种,两年共同优势种为中华哲水蚤（Calanus sinicus）、太平洋纺锤水蚤（Acartia pacifica）、精致真刺水蚤（Euchaeta concinna）、肥胖箭虫（Sagitta enflata）和肥胖三角溞（Evadne tergestina）。相似性百分比分析（SIMPER）分析表明,年间浮游动物群落差异的主要贡献种为肥胖三角溞、中华哲水蚤、海樽类（Thaliacea）,CCA分析表明,表层温度（T_S）、底层盐度（S_b）和表层叶绿素a （C_S）是影响年际间浮游动物类群差异的主要环境因子,解释了两年浮游动物类群变异的47.51%。根据2018年叶绿素a空间分布,将站位分为叶绿素a锋面区和非锋面区,L1~L2站为非叶绿素a锋面区,L3~L4站为叶绿素a锋面区。浮游动物群落在二者空间差异的主要贡献种为肥胖三角溞、背针胸刺水蚤（Centropages dorsispinatus）、精致真刺水蚤,CCA分析表明,底层盐度（S_b）、底层温度（T_b）和表层叶绿素a （C_S）是影响浮游动物类群空间变化的主要环境因子,解释了2018年浮游动物类群组成变异的56.31%。该结果表明,引起盐度和叶绿素a变化的长江冲淡水径流量对浮游动物群落结构年际变化造成了重要影响。     

2017年长江口海域夏季叶绿素a昼夜动态变化及影响因素

根据2017年夏季长江口海域的两个连续站位的温盐深仪剖面调查及24 h水样的采样数据,获得两个站位的温度、盐度、叶绿素a及营养盐剖面昼夜分布.利用回归分析法,研究各水层环境因子对叶绿素a的影响,建立不同水层叶绿素a变化与环境因子、浮游动物捕食效应的多元回归模型,并探讨长江口海域夏季叶绿素a昼夜动态变化机制.研究结果显示...     

海州湾大泷六线鱼摄食生态研究

为了解海州湾大泷六线鱼时空分布特征及其影响因素,根据2013—2019年秋季在海州湾开展的底拖网渔业资源调查和环境观测数据,构建了时空物种分布模型(spatio-temporal species distribution models),分析其分布与环境因子的关系,通过残差分析比较其与广义加性模型的残差独立性和异质性,运用交叉验证检验模型预测性能,最终结合delta方法对其分布进行预测并计算栖息地适宜性指数(habitat suitability index, HSI)和资源分布重心。时空模型的偏差解释率为65.50%,模型分析表明,影响大泷六线鱼资源分布最主要的环境因子为水深(22.11%),其次为底层水温(12.98%),底层盐度(0.09%)的影响较小,水深与其分布存在正向相关性,底层水温与其分布存在负向相关性,底层盐度与其分布存在弱正向线性关系。时空模型的残差独立性和异质性较GAM更强,其交叉验证回归线斜率为0.90±0.38。模型预测结果表明,大泷六线鱼主要分布在34.5°N以北,120.0°E以东的海域,其栖息地适宜性指数的高值区域呈现逐年收缩的趋势,资源分布重心呈现向东北海域转移的趋势,这可能是气候变迁以及捕捞压力共同作用的结果。本研究解析了大泷六线鱼在海州湾的时空分布,对于深入了解大泷六线鱼的分布动态和科学的渔业管理具有重要意义。     

Ichthyoplankton distribution and abundance in relation to nearshore dissolved oxygen levels and other environmental variables within the Northern California Current System

Nearshore hypoxia along the coast of Oregon and Washington is a seasonal phenomenon that has generated concern among scientists studying this temperate upwelling ecosystem. These waters are affected by coastal upwelling‐induced hypoxia mainly during late summer and fall, but the effects of low oxygen levels on fish and invertebrate communities, particularly during the early‐life history stages, are poorly known. We investigated the effects of hypoxia and other variables on the species composition, density, vertical and horizontal distribution of fish larvae along the Oregon and Washington coasts during the summers of 2008, 2009 and 2010. Bottom‐dissolved oxygen (DO) values ranged from 0.49 to 4.79 mL L^?1, but the overall water column DO values were only moderately hypoxic during the 3 yr of sampling compared with recent extreme years. In this study, DO was found to be an environmental parameter affecting the species composition, but other variables such as season, year and depth of capture were also important. Although the overall density of fish larvae increased with increasing bottom‐DO values, the effect on individual species density was limited. Slender sole (Lyopsetta exilis) and sand sole (Psettichthys melanostictus) were the only species to have a weak trend of density with DO, but both showed negative relationships and neither relationship was significant. Our results indicate that larval fish spatial distribution was only moderately affected within the range of observed oxygen values, but low DO may be an important factor under intense hypoxic conditions.