Seasonal potential fishing ground prediction of neon flying squid (Ommastrephes bartramii) in the western and central North Pacific

We explored the seasonal potential fishing grounds of neon flying squid (Ommastrephes bartramii) in the western and central North Pacific using maximum entropy (MaxEnt) models fitted with squid fishery data as response and environmental factors from remotely sensed [sea surface temperature (SST), sea surface height (SSH), eddy kinetic energy (EKE), wind stress curl (WSC) and numerical model‐derived sea surface salinity (SSS)] covariates. The potential squid fishing grounds from January–February (winter) and June–July (summer) 2001–2004 were simulated separately and covered the near‐coast (winter) and offshore (summer) forage areas off the Kuroshio–Oyashio transition and subarctic frontal zones. The oceanographic conditions differed between regions and were regulated by the inherent seasonal variability and prevailing basin dynamics. The seasonal and spatial extents of potential squid fishing grounds were largely explained by SST (7–17°C in the winter and 11–18°C in the summer) and SSS (33.8–34.8 in the winter and 33.7–34.3 in the summer). These ocean properties are water mass tracers and define the boundaries of the North Pacific hydrographic provinces. Mesoscale variability in the upper ocean inferred from SSH and EKE were also influential to squid potential fishing grounds and are presumably linked to the augmented primary productivity from nutrient enhancement and entrainment of passive plankton. WSC, however, has the least model contribution to squid potential fishing habitat relative to the other environmental factors examined. Findings of this work underpin the importance of SST and SSS as robust predictors of the seasonal squid potential fishing grounds in the western and central North Pacific and highlight MaxEnt's potential for operational fishery application.     

我国东、黄海鲐鱼灯光围网渔业CPUE标准化研究

日本鲐是我国近海重要的中上层鱼类资源之一,评估其资源量需要对单位捕捞努力量渔获量（CPUE）进行标准化。影响CPUE标准化的因素很多,包括季节、区域和海洋环境等。本文利用广义线型模型（GLM）和广义加性模型（GAM）,结合时空、捕捞船、表温等因子,对1998-2006年东、黄海大型灯光围网渔业鲐鱼CPUE进行标准化,并评价各因子对CPUE的影响。首先应用GLM模型评价时间、空间、环境以及捕捞渔船参数对CPUE的影响,并确定显著性变量。其次,将显著性变量逐一加入GAM模型,根据Akaike信息法则（AIC）,选择最优的GAM模型。最后,利用最优的GAM模型对CPUE标准化,并定量分析时间、空间、环境以及捕捞渔船参数对鲐鱼CPUE的影响。GLM模型结果表明：8个变量对CPUE有重要影响,依次为年、船队、船队与年的交互效应、月、船队与月份的交换效应、经度、纬度和海表温。根据AIC,包含上述8个显著性变量的GAM模型为最优模型,对CPUE偏差的解释为27.78%。GAM模型结果表明：高CPUE分别出现在夏季海表温为28～31 ℃的东海中部和冬季海表温为12～16 ℃的黄海;1998-2006年,标准化后的CPUE呈逐年下降趋势,与持续增长的捕捞努力量有关。     

2015年超强厄尔尼诺事件对西北太平洋柔鱼渔场变动的影响

为研究超强厄尔尼诺事件对西北太平洋海域柔鱼（Ommastrephes bartarmii）资源量变动的影响,并分析柔鱼栖息地在极端气候条件下的变化规律,根据上海海洋大学鱿钓科学技术组提供的中国柔鱼生产捕捞数据,比较2008年正常气候年份与2015年超强厄尔尼诺年份的单位捕捞努力量渔获量（CPUE）、产量、捕捞努力量以及渔场纬度重心（LATG）的变化;利用栖息地适宜性指数模型对西北太平洋柔鱼栖息地的海表温度（SST）、光合有效辐射范围（PAR）和海表面高度距平（SSHA）3个关键环境因子进行分析。渔业数据时间为2008年和2015年9—11月,数据覆盖范围为36°N~48°N、150°E~170°E。结果发现,相对于2008年正常年份,2015年超强厄尔尼诺事件下的CPUE明显降低,且LATG向南偏移;此外,2015年适宜的SST和PAR范围均显著降低,导致适宜的栖息地面积与正常年份相比大幅减少;最适宜的SST和PAR等值线向南偏移,导致有利的栖息地纬度位置向南移动。研究认为,2015年超强厄尔尼诺事件发生时,柔鱼渔场环境不适于柔鱼生长,适宜栖息地面积减少且向南移动,导致该年份柔鱼资源丰度骤减,渔场向南偏移。     

西南大西洋阿根廷滑柔鱼渔业中国大陆鱿钓船CPUE标准化

阿根廷滑柔鱼是我国重要的头足类渔业之一,对其单位捕捞努力量渔获量( CPUE)进行标准化是对其资源评估的重要内容。本研究根据2000～2010年我国在西南大西洋的产量统计数据和卫星遥感获得的海洋环境数据（表温,表温水平梯度,海面高度,叶绿素浓度）,利用广义线性模型（GLM,general linear model）和广义加性模型（GAM,generalized additive model）对其CPUE进行标准化。GLM模型结果表明,年、纬度、表温以及交互项年与纬度对CPUE影响最大。GAM模型研究结果表明,年、月、经度、纬度、表温、海面高度以及交互项年与纬度、年与经度对CPUE影响较大。根据AIC数值,包含上述8个显著变量的GAM模型为最佳模型,对CPUE的解释率为49.20%。高CPUE出现在夏季表温为12～16°C、海面高为-20~20cm、46.5°～48.5°S海域。研究表明,GAM模型较GLM模型更适合用于西南大西洋阿根廷滑柔鱼CPUE标准化。     

阿根廷滑柔鱼渔场预报模型最适时空尺度和环境因子分析

根据2003―2011年主渔汛期间中国鱿钓船队在西南大西洋的鱿钓生产数据,结合海洋遥感获得的海表温度(SST)、海面高度(SSH)和叶绿素a浓度(CHL-a)数据,匹配组织成不同时空尺度和环境因子的样本集,使用人工神经网络(artificial neural network,ANN)作为中心渔场的预报模型,比较所匹配的样本集对阿根廷滑柔鱼中心渔场预报模型的影响。研究表明,样本的时间尺度为周时,1.0o×1.0o的空间尺度和环境因子为SST所建立的BP中心渔场预报模型,具有最高的预报精度和最小的平均相对变动值(average relative variance,ARV);样本时间尺度为月时,0.25o×0.25o的空间尺度和环境因子为SST所建立的BP中心渔场预报模型,具有最高的预报精度和最小的ARV值。对这两种最优样本集建立的BP中心渔场预报模型进行灵敏度分析发现,不同样本集建立的中心渔场预报模型表达的渔场栖息地适宜程度也不尽相同。研究认为,在建立中心渔场预报模型时,需要考虑海洋环境因子的时空尺度。     

基于空间相关性的西北太平洋柔鱼CPUE标准化研究

CPUE标准化方法通常都假设名义CPUE之间是相互独立且没有相关性,然而鱼类集群分布通常存在着空间相关性,为此本研究以西北太平洋柔鱼的CPUE标准化为例,采用1999-2012年6-11月中国鱿钓生产数据以及对应的海表面温度和叶绿素浓度的环境数据,将空间相关性加入广义线性模型(general linear model,GLM)中.在空间GLM模型中运用4个距离模型(指数模型、球面模型、线性模型和高斯模型),进行标准GLM模型和4种空间GLM模型的CPUE标准化结果比较.结果发现,4种空间GLM模型均比标准GLM模型的最小信息准则(akaike information criterion,AIC)更小,标准化结果更准确.同时,在4个距离模型中,指数模型的AIC值最小,其CPUE标准化结果最佳.研究表明,在CPUE标准化中,鉴于鱼类集群与分布特性,应该充分考虑空间相关性这一因素.     

Spatial correlation patterns in coastal environmental variables and survival rates of salmon in the north-east Pacific Ocean

We examined spatial correlations for three coastal variables [upwelling index, sea surface temperature (SST), and sea surface salinity (SSS)] that might affect juvenile salmon ( Oncorhynchus spp.) during their early marine life. Observed correlation patterns in environmental variables were compared with those in survival rates of pink ( O. gorbuscha ), chum ( O. keta ), and sockeye ( O. nerka ) salmon stocks to help identify appropriate variables to include in models of salmon productivity. Both the upwelling index and coastal SST were characterized by strong positive correlations at short distances, which declined slowly with distance in the winter months, but much more rapidly in the summer. The SSS had much weaker and more variable correlations at all distances throughout the year. The distance at which stations were no longer correlated (spatial decorrelation scale) was largest for the upwelling index (> 1000 km), intermediate for SST (400–800 km in summer), and shortest for SSS (< 400 km). Survival rate indices of salmon showed moderate positive correlations among adjacent stocks that decreased to zero at larger distances. Spatial decorrelation scales ranged from approximately 500 km for sockeye salmon to approximately 1000 km for chum salmon. We conclude that variability in the coastal marine environment during summer, as well as variability in salmon survival rates, are dominated by regional scale variability of several hundred to 1000 km. The correlation scale for SST in the summer most closely matched the observed correlation scales for survival rates of salmon, suggesting that regional-scale variations in coastal SST can help explain the observed regional-scale covariation in survival rates among salmon stocks.     

Impact of paralarvae and juveniles feeding environment on the neon flying squid (Ommastrephes bartramii) winter–spring cohort stock

In this study, we found that there were significant positive correlations between the catch per unit effort (CPUE, a squid abundance index) for the neon flying squid (Ommastrephes bartramii) winter–spring cohort and the satellite‐derived chlorophyll a concentrations in their spawning grounds located at 140–160°E where 21°C < sea surface temperature < 25°C from February to May. The spawning grounds of the winter–spring cohort are located in a quiet stream region, and a particle tracking experiment, based on the velocity field obtained from an ocean data assimilation system, showed that paralarvae and juveniles aged <90 days remained in their spawning grounds and the chlorophyll a concentration in their habitat had a significant positive correlation with the CPUE. A backward particle tracking experiment also showed that the chlorophyll a concentration in the spawning grounds had a significant positive correlation with the autumn–winter mixed layer depth. Based on these results, we hypothesize that the CPUE interannual variability is caused by variations in the feeding environment of the paralarvae and juveniles, which may be linked to autumn–winter mixed layer depth variations.     

Oceanographic factors affecting interannual recruitment variability of Pacific saury (Cololabis saira) in the central and western North Pacific

Pacific saury (Cololabis saira) has a short life span of 2 years and tends to exhibit marked population fluctuations. To examine the importance of sea surface temperature (SST) and mixed layer depth (MLD) as oceanographic factors for interannual variability of saury recruitment in early life history, we analyzed the relationship between abundance index (survey CPUE (catch per unit of effort)) of age‐1 fish and the oceanographic factors in the spawning and nursery grounds of the previous year when they were born, for the period of 1979–2006, in the central and western North Pacific. Applying the mixture of two linear regression models, the variability in the survey CPUE was positively correlated with previous year's winter SST in the Kuroshio Recirculation region (KR) throughout the survey period except 1994–2002. In contrast, the survey CPUE was positively correlated with the previous year's spring MLD (a proxy of spring chlorophyll a (Chl‐a) concentration) in the Kuroshio‐Oyashio Transition and Kuroshio Extension (TKE) during 1994–2002. This period is characterized by unusually deep spring MLD during 1994–1997 and anomalous climate conditions during 1998–2002. We suggest that saury recruitment variability was generally driven by the winter SST in the KR (winter spawning/nursery ground), or by the spring Chl‐a concentration (a proxy of prey for saury larvae) in the TKE (spring spawning/nursery ground). These oceanographic factors could be potentially useful to predict abundance trends of age‐1 saury in the future if the conditions leading to the switch between SST and MLD as the key input variable are elucidated further.     

If you build it,they will go: A case study of stream fish diversity loss in an urbanizing riverscape

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Wind‐induced stock variation of the neon flying squid (Ommastrephes bartramii) winter–spring cohort in the subtropical North Pacific Ocean

Our examination of the neon flying squid (Ommastrephes bartramii) winter–spring cohort catch per unit effort (CPUE, an index of stock) revealed significant positive correlations with the interannual variations of observed chlorophyll‐a (Chl‐a) concentration and autumn–winter mixed layer depth (MLD) in the winter–spring feeding grounds of paralarvae and juveniles (130–170°E, 20–27°N). These correlations suggest the importance of integrated bottom‐up effects by the autumn–winter MLD for the neon flying squid stocks. However, the influence of autumn–winter MLD interannual variation in the forage availability for paralarvae and juveniles, i.e., particulate organic matter and zooplankton, has still been unclear. In this study, we use the lower trophic ecosystem model NEMURO, which uses the physical environmental data from the ocean reanalysis dataset obtained by the four‐dimensional variational (4DVAR) data assimilation method. The model‐based investigation enables us to clarify how the autumn–winter MLD controls the particulate organic matter and zooplankton abundance in the feeding grounds. Further, our investigation of the autumn–winter MLD interannual variation demonstrates that the stronger autumn wind in the feeding grounds develops a deeper mixed layer. Therefore, the deep mixed layer entrains nutrient‐rich water and enhances photosynthesis, which results in good feeding conditions for paralarvae and juveniles. Our results underline that the wind system interannual variation has critical roles on the winter–spring cohort of the neon flying squid stock.     

基于不同模型研究环境因子对中西太平洋鲣资源丰度的影响

根据1998—2013年中西太平洋鲣(Katsuwonus pelamis)生产数据,选取时空因子(年、月、经纬度)和环境因子[海表面温度(SST)、海表面高度(SSH)、尼诺指数(ONI)和叶绿素a浓度]Chl-a)],通过两种不同的模型(广义加性模型GAM和提升回归树模型BRT)研究各因子对鲣资源丰度(以CPUE表示)的影响。研究结果认为,GAM模型中,经度对CPUE的影响最大,累计解释偏差超过50%,其次为纬度、年和月;在环境因子中,SSH最为重要,其次为ONI,而SST和Chl-a的影响相对较低。BRT模型分析结果与GAM分析结果类似,时空因子相对占据了重要的地位,其中经度的影响最大,其次为年、纬度和月;而在环境因子中,ONI的重要性相对更高,其次为SSH,SST和Chl-a同样影响较低。研究认为,两种模型均能较好地反映出因子对CPUE的影响。由于厄尔尼诺/拉尼娜现象引起的海洋环境变化会使鲣资源分布产生差异,因此在后续的渔情预报研究中,应该更多地考虑将ONI因子纳入渔情预报模型中,以提高预测精度。     

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。     

Linking watershed and microhabitat characteristics: effects on production of Atlantic salmonids (Salmo salar and Salmo trutta)

The spatial scale of environmental factors influencing population dynamics ranges from microhabitat to continental or even global scales. Integration of multiple spatial scales is important in order to understand links between environmental variation and population processes. In the present study, we investigate how multiscale drivers influence the production of stream‐rearing Atlantic salmonids (Atlantic salmon, Salmo salar L. and brown trout, Salmo trutta L.) measured in terms of abundance. Variation in juvenile production was studied using data from single‐pass electrofishing surveys (measured as biomass per m²) from nine rivers. These data were combined with habitat data ranging from an important in‐stream microhabitat variable (shelter availability) to properties of the catchment. Variation in productivity within and among rivers was affected by both properties of in‐stream habitat and catchment properties. Shelter availability and the proportion of the catchment consisting of cultivated land and lakes influenced biomass positively, while catchment area had the opposite effect. For a different set of rivers (N = 20), river gradient and catchment area were shown to positively affect the amount of shelter. Finally, the variables identified in the two preceding analysis were included in the analysis of population productivity using catch statistics from 160 rivers. The proportion of cultivated land and lakes, estimated shelter availability were found to have positive effects. In addition, temperature had a positive effect, while river width had a negative effect. This study shows that combining multiple‐scale environmental factors can explain a substantial proportion of variation in population productivity among and within the populations of Atlantic salmonids.     

The effects of climate variability on zooplankton and basking shark (Cetorhinus maximus) relative abundance off southwest Britain

At small spatial scales basking sharks (Cetorhinus maximus) forage selectively on zooplankton along thermal fronts, but the factors influencing broader scale patterns in their abundance and distribution remain largely unknown. Using long‐term sightings data collected off southwest Britain between 1988 and 2001, we show that the number of basking sharks recorded was highly correlated with abiotic factors, principally sea surface temperature (SST) and the lagged effect of SST in the previous month, but only very weakly to zooplankton density. This suggests that the changes in number of basking sharks recorded over large spatio‐temporal scales are more closely related to the availability of climate‐driven thermal resources than prey availability, whereas the converse is supported by previous studies at local scales. Taken together, these results imply scale‐dependent behavioural responses in basking sharks, with small‐scale foraging movements linked by broad scale responses to temperature variation.     

Detection of density‐dependent growth at two spatial scales in marble trout (Salmo marmoratus) populations

Vincenzi S, Crivelli AJ, Jesensek D, De Leo GA. Detection of density‐dependent growth at two spatial scales in marble trout (Salmo marmoratus) populations.
Ecology of Freshwater Fish 2010: 19: 338–347. © 2010 John Wiley & Sons A/S Abstract – Density‐dependent body growth has often been observed in freshwater salmonid populations. Several studies suggest this compensatory pattern as a potential mechanism of population regulation. The choice of the spatial scale is important for the detection of density‐dependent growth, as study areas need to be of the appropriate size to capture the density of conspecifics actually experienced by individuals over the preceding growth period. Here, we used four marble trout (Salmo marmoratus) populations (Gatsnik, Gorska, Huda and Zakojska) living in Slovenian stream to study the relationships between early density of marble trout and subsequent body growth. As streams are divided in sectors delimited by natural barriers that prevent or strongly limit movement of individuals, we tested the relationship between early density and body size through the lifetime at two spatial scales, that is, sector level (for Gatsnik and Zakojska) and whole stream level (the four populations were pooled). Sector length in Gatsnik and Zakojska ranged from 113 to 516 m. At both sector and whole stream level, temporal data were pooled. Growth declined significantly with increasing density both at the sector and whole stream levels, and the density‐dependent relationship was described by negative power curves. However, at the sector level the density‐dependent pattern was stronger in Gatsnik, a stream in which fish could move across sectors, than in Zakojska, where upstream movement across sectors is prevented by waterfalls.     

Modeling environmental,temporal and spatial effects on twaite shad (Alosa fallax) by‐catches in the central Mediterranean Sea

Modeling the relationships between environmental factors and the distribution at sea of species of conservation interest can be useful in predicting their occurrence from a local to a regional scale. This information is essential for planning management and conservation initiatives. In this study, generalized additive models (GAMs) were applied to investigate the influence of environmental, temporal and spatial variables on the catch rates of the twaite shad Alosa fallax (Lacepède) by the pelagic trawl fishery in the north‐central Adriatic Sea. Presence/absence and abundance [catch per unit effort (CPUE)] data between 2006 and 2012 were separately modeled, and the two models were then validated using a test data set. The most important factor influencing the presence and abundance of adult twaite shads was the spatial predictor (latitude × longitude). Two areas of major shads aggregations were observed, the most important of which being located near the estuaries of three main river systems of northern Italy. The twaite shad presence was also significantly affected by season, the largest and lowest occurrences being observed in autumn and spring, respectively. Among the environmental variables tested, only sea surface temperature was included in both models. Alosa fallax showed a wide thermal tolerance (6–27°C) with preference for temperature around 23°C. The model developed from the abundance data showed a moderate predictive power, whereas the accuracy of the presence/absence model was rather low. Some conclusions on the ecological requirements of A. fallax at sea arising from this study are useful to orient future monitoring and research programs and to develop effective conservation actions.     

Prey and non‐native fish predict the distribution of Colorado pikeminnow (Ptychocheilus lucius) in a south‐western river in North America

Colorado pikeminnow (Ptychocheilus lucius) has been extirpated from a large portion of its historical range in the Colorado River basin, USA. A repatriation effort via stocking of juvenile P. lucius in the San Juan River, NM, CO and UT has resulted in limited recruitment of individuals into an adult population. Understanding biotic and abiotic factors that limit their persistence in the Colorado River basin will be a critical step in providing for their recovery. To elucidate potential recruitment barriers in the San Juan River, we assessed relationships between the numbers of two age classes of P. lucius and prey, competitors and predators collected at a 1.6 km reach scale between 2003 and 2012. We used an information theoretical approach to rank candidate models testing the relative importance of these biotic conditions in predicting the spatial distribution of P. lucius. We found positive relationships between the numbers of P. lucius ≤200 mm total length (TL) collected and catch per unit effort (CPUE) of native prey among reaches. For P. lucius >200 mm TL (individuals that are likely completely piscivorous), we found positive associations between the numbers of P. lucius collected and CPUE of total prey and CPUE of potential non‐native competitors in each reach. Our data suggest size‐specific affinities of P. lucius for native and non‐native prey as well as the potential for negative interactions between P. lucius and non‐native competitors may contribute to limited recruitment of juvenile P. lucius into an adult population in the San Juan River.     

Predicting the current and future suitable habitat distributions of the anchovy (Engraulis ringens) using the Maxent model in the coastal areas off central‐northern Chile

An assessment of climate change impacts on the habitat suitability of fish species is an important tool to improve the understanding and decision‐making needed to reduce potential climate change effects based on the observed relationships of biological responses and environmental conditions. In this study, we use historical (2010–2015) environmental sea surface temperature (SST), upwelling index (UI), chlorophyll‐a (Chl‐a) and biological (i.e., anchovy adults acoustic presence) data (i.e., Maxent) to determine anchovy habitat suitability in the coastal areas off central‐northern (25°S–32°S) Chile. Using geographic information systems (GIS), the model was forced by changes in regionalized SST, UI and Chl‐a as projected by IPCC models under the RPC (i.e., RCP2.6, RCP4.5, RCP6.0 and RCP8.5) emissions scenarios for the simulation period 2015–2050. The model simulates, for all RCP scenarios, negative responses in anchovy presence, reflecting the predicted changes in environmental variables, dominated by a future positive (warming) change in SST and UI, and a decrease in chlorophyll‐a (i.e., phytoplankton biomass). The model predicts negative changes in habitat suitability in coastal areas from north of Taltal (25°S) to south of Caldera (27°45′S) and in Coquimbo littoral zone (29°–30°12′S). The habitat suitability models and climate change predictions identified in this study may provide a scientific basis for the development of management measures for anchovy fisheries in the coastal areas of the South American coast and other parts of the world.     

Comparing the effects of offset and non‐offset circle hooks on catch rates of fish and sea turtles in a shallow longline fishery

• 1. This study compared the catch rates of targeted dolphinfish or mahimahi (Coryphaena hippurus), and sea turtles and other fish bycatch in a shallow‐set Costa Rican longline fishery using 14/0 circle hooks with and without a 10° offset. The effect of hook offset on hooking location and injury in captured sea turtles, specifically if the hooking was external, in the mouth, or in the esophagus was also evaluated.
• 2. Results were compared from six trips totalling 33 876 hooks with squid (Dosidicus gigas) used as bait. In total, mahimahi catch‐per‐unit‐effort (CPUE, expressed as number caught per 1000 hooks) was similar between hook types (CPUE～52).
• 3. Olive ridley sea turtles (Lepidochelys olivacea) were caught on all 42 sets. In total, 640 olive ridley turtles were caught and released alive. There were no significant differences in the number of sea turtles caught between hooks with and without an offset (CPUE～19) nor between hook type and anatomical hooking location, suggesting similar levels of injury for turtles caught on each hook type.
• 4. These data suggest that a 10° offset on 14/0 circle hooks does not confer any selective advantages over hooks with no offset with respect to capture rates of mahimahi, sea turtles, sharks, or pelagic stingrays in a shallow set pelagic longline fishery. Copyright © 2010 John Wiley & Sons, Ltd.