Identifying Lagrangian fronts with favourable fishery conditions

Lagrangian fronts (LFs) in the ocean are defined as boundaries between surface waters with strongly different Lagrangian properties. They can be accurately detected in a given velocity field by computing synoptic maps for displacements of synthetic tracers and other Lagrangian indicators. We use Pacific saury catch and location data for a number of commercial fishery seasons in the region of the northwest Pacific with one of the richest fishery in the world. It is shown statistically that the saury fishing grounds with maximal catches are not randomly distributed over the region but located mainly along the sharp LFs where productive cold waters of the Oyashio Current, warmer waters of the southern branch of the Soya Current, and waters of warm-core Kuroshio rings converge. Computation of those fronts in altimetric geostrophic velocity fields both in the years with the First and Second Oyashio Intrusions shows that in spite of different oceanographic conditions LF locations may serve as good indicators of potential fishing grounds. Possible biophysical reasons for saury aggregation near sharp LFs are discussed. We propose a mechanism for effective export of nutrient rich waters based on stretching of material lines in the vicinity of hyperbolic objects in the ocean. The developed method, based on identifying LFs in any velocity fields, is quite general and may be applied to find potential fishing grounds for the other pelagic fish.     

Effects of the Anticyclonic Eddies on Water Masses, Chemical Parameters and Chlorophyll Distributions in the Oyashio Current Region

Data from the R/V Mirai cruise (May–June 2000) have been examined to discover how mesoscale processes associated with eddy dynamics direct affect the water masses, the distributions and the vertical fluxes of the dissolved oxygen, nutrients and dissolved inorganic carbon in the western subarctic Pacific. Using maps of the temperature, salinity, dissolved oxygen, nutrients, chlorophyll and sea-air pCO₂ difference we show that the boundaries of the anticyclone eddies in the study region were composed of high productivity coastal Oyashio water. The coastal waters were wrapped around the anticyclone eddies (thus creating a high productivity belt) and intruded inside of them. Using SeaWifs data we demonstrate that temporal variations in the position and the strength of anticyclone eddies advected the Kuril island coastal high productivity waters to the pelagic part, resulting in temporal variations of the chlorophyll in the Oyashio region. Computed vertical fluxes of the dissolved oxygen (DO), inorganic carbon (DIC) and silicate show that the anticylonic eddies in the Kuroshio-Oyashio Zone are characterized by enhanced vertical fluxes of the DO and DIC between the upper (σ_θ = 26.7–27.0) and lower (σ_θ = 27.1–27.5) intermediate layer, probably due to the intrusions of the Oyashio waters into the eddies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hawaii Cyclonic Eddies and Blue Marlin Catches: The Case Study of the 1995 Hawaiian International Billfish Tournament

The combination of prevailing northeasterly tradewinds and island topography results in the formation of vigorous, westward propagating cyclonic eddies in the lee of the Hawaiian Islands on time scales of 50–70 days. These mesoscale (∼10² km) features are nowhere more conspicuous or spin up more frequently than in the Alenuihaha Channel between the Island of Maui and the Big Island of Hawaii. Cyclonic eddies in subtropical waters such as those around Hawaii vertically displace the underlying nutricline into the overlying, nutrient-depleted euphotic zone creating localized biologically enhanced patches. Insight into how these eddies may directly influence pelagic fish distribution is provided by examination of recreational fish catch data coinciding with the presence of eddies on the fishing grounds. We highlight the 1995 Hawaii International Billfish Tournament in which a cyclonic eddy dominated the ocean conditions during the weeklong event and the fish catch distribution differed significantly from the average historical tournament catch patterns. On the tournament fishing grounds, well-mixed surface layers and strong current flows induced by the eddy's presence characterized the inshore waters where the highest catches of the prized Pacific blue marlin (Makaira mazara) occurred, suggesting possible direct (e.g., physiological limitations) or indirect (e.g., prey availability) biological responses of blue marlin to the prevailing environment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Oceanographic Characteristics of a Multi-Specific Fishing Ground of the Central South Brazil Bight

In the Central South Brazil Bight, a multispecific demersal trawl fishery is conducted by trawlers licensed for the industrial pink shrimp (Penaeus paulensis and Penaeus brasiliensis) fishery. In addition to the pink shrimp, many by-catch species have become increasingly valued in the last two decades. In spite of the importance of this multispecific fishery, the oceanographic characteristics of the inner continental shelf, onshore the 100 m isobath, are poorly known. In this paper we present, for the fist time, monthly oceanographic records taken from December 1995 to May 1997 with the R/V ‘Diadorim’ at two of the main fishing grounds of this region. Water temperature data showed the formation of a strong thermocline during summer, from November to April. This thermal gradient, due to the South Atlantic central water (SACW) intrusion that reaches these shallow waters, disappeared with the homogenization of the water column during autumn and winter, from May to September. This cold and low salinity water does not originate from local river discharges, but also represents an advection of sub-Antartic water mass. After this and during spring, a new thermocline develops, reaching its maximal expression from February to March. A maximal gradient was registered in February 1997, when the temperature dropped from 26°C at 7 m to 16°C at 14 m depth. This result shows that the SACW intrusion is a large-scale phenomenon that regularly influences the whole inner continental shelf up to 20 m. Demersal fishing grounds located in this area were covered during summer by a cold and nutrient-rich mass of water that resulted in an unusual maximum of chlorophyll a values near the bottom (30 m). The homogenization of the water column and the presence of another cold water mass during winter resulted in a strong semi-annual thermal cycle on the bottom. The role of this important oceanographic process in fishery production and dynamics deserves further investigation, but the data presented here show evidence for the importance of this phenomenon.     

渔业资源分布图批处理算法Arcgis二次开发的实现

基于Arcgis内置的VBA语言平台,实现一种渔业资源分布图批处理算法。该方法的主要特点是实现了对海量渔获数据自动批处理制图,平均绘图速度达到2s／幅,与手工绘图相比大大提高了工作效率。绘图结果清晰易读,可用于分析渔获物的数量分布和季节变化特征,如有多年统计资料,还可用于中心渔场预报研究,并可为渔业资源开发、利用和保护提供决策支持。     

The biological oceanography of the East Australian Current and surrounding waters in relation to tuna and billfish catches off eastern Australia

The surface and sub-surface biological oceanography of tuna fishing grounds within the East Australian Current (EAC) was compared in 2004 with two other fishing areas further offshore. Our aim was to determine whether the biological oceanography of the region could explain the distribution and intensity of pelagic fishery catches inside and outside the EAC at that time. The EAC fishing area was noticeably warmer, less saline and lower in nutrients than waters in the other fishing areas. The EAC waters were dominated by large diatoms, the biomass of which was significantly higher than in the seamount and offshore areas, apparently the result of a cold core eddy beneath the EAC surface filament. Over the seamount and offshore more typical Tasman Sea waters prevailed, although the presence of a relatively deeper oxygen minimum layer over the seamount suggested topographically induced mixing in the area. Notably, sub-surface zooplankton and micronekton biomass was significantly higher around the seamount than in the two other areas. The offshore region was characterised by frontal activity associated with the Tasman front. Micronekton net biomass was generally highest in surface waters in this region. Examination of tuna catch records at that time showed yellowfin tuna (Thunnus albacares) dominated the catches of the EAC, whereas swordfish (Xiphias gladius) and bigeye tuna (Thunnus obesus) were the main species caught offshore. We suggest the yellowfin tuna concentrate in waters that are not only warmer but where prey species are concentrated near the surface. Offshore, deeper living species such as swordfish and bigeye tuna (T. obesus) can take advantage of prey species that are distributed deeper in the water column and along the flanks of the many seamounts in the region, or that are concentrated at fronts associated with the Tasman Front. Although only a snapshot of the region, relatively consistent catch data over time suggests the underlying biological oceanography may persist over longer time periods, particularly during the Austral spring.     

表层水温结构变化对东南太平洋秘鲁鳀渔场的影响

秘鲁鳀（Engraulis ringens）是栖息于东南太平洋沿岸的小型中上层鱼类,掌握其渔场变化及其与海洋环境因子的关系有利于企业把握该渔业的生产情况。研究结合2005-2014年渔汛期间秘鲁各港口出港的船数及其所获得的秘鲁鳀渔获量和表层水温数据（海表面温度,sea surface temperature,SST）,以单位捕捞努力量的渔获量（catch per unit effort,CPUE）和捕捞努力量（Effort）数据构建的渔场指数（fishing ground index,FGI）为渔场指标,对秘鲁鳀的渔场类型进行分类,探讨水温结构变化对秘鲁鳀渔场的影响。方差分析表明:渔场指数在不同渔汛阶段（渔汛前期、中期和末期,P<0.01）和不同捕捞区域（北部、中部和南部,P<0.01）都有着极显著的差异。以表层水温大于20℃的海水是否入侵到近岸为标志,可以将秘鲁鳀渔场分成两种类型:大于20℃的海水没有入侵到沿岸（A型渔场）和入侵到沿岸（B型渔场）。研究表明,在渔汛前期和中期阶段,A型渔场的出现有利于渔场的形成,其中渔汛前期沿岸19℃或20℃等温线的出现以及渔汛中期沿岸18℃或19℃等温线的出现可以作为中心渔场形成的指标。     

利用基于表温因子的栖息地模型预测西北太平洋柔鱼(Ommastrephes bartramii)渔场

根据1999—2004年8—10月主渔汛期间我国鱿钓船在150—165°E海域的鱿钓生产数据,结合其表温及表温梯度,分别将作业次数百分比和单位渔船日产量作为适应性指数,利用算术平均法(AM)和联乘法(GM)分别建立基于表温因子(表温和表温水平梯度)的综合栖息地指数模型。结果表明,AM栖息地指数模型和GM栖息地指数模型均拟合较好,在HSI大于0.6的海域,1999—2004年间其作业次数平均比重分别在70%以上,平均日产量均在2t/d以上。但AM模型稍优于GM模型。利用2005年8—10月生产数据及表温资料对AM模型进行验证,分析认为作业渔场主要分布在HSI大于0.6海域,其作业次数比重达到80%以上,各月平均CPUE均在3.0t/d以上。研究表明,基于表温和表温水平梯度的AM栖息地模型能获得较好预测西北太平洋柔鱼中心渔场。     

东海西北部水团分析及与渔场的关系

作者用聚类分析法划分浅海水团,目的在于克服大洋水团分析法进行分析所遇到的一些困难,它在根据不同海区特点确定临界值与检验值时有较大的灵活性。本文讨论了浅海变性水团与中心渔场的关系。结果表明,东海底层冷水、东海表层水和大陆沿岸水对渔业生产有重要影响。     

东太平洋赤道海域茎柔鱼小型群体资源分布及其渔场环境特征

茎柔鱼(Dosidicus gigas)是我国远洋渔业的重要捕捞对象。当前针对茎柔鱼渔场分布及其与环境关系的研究多集中于秘鲁海域,针对赤道海域茎柔鱼特定种群小型群体资源分布及其渔场环境特征研究较少。根据2019年12月至2020年2月茎柔鱼生物学数据,2019年12月至2020年4月生产和环境数据,运用胴长-体重关系拟合、地统计插值、广义可加模型(GAM)探究其资源分布及渔场环境状况。结果表明：东太平洋赤道海域茎柔鱼胴长范围为136~407 mm,体重范围为117~1557 g；2019年12月至2020年4月各月渔获量呈先增加后减小趋势,2月渔获量最高；CPUE曲线除2月增加外,总体呈下降趋势；渔场集中分布于0°~3°S、105°W~114°W海域,不同月份渔场重心经向变化明显；渔场最适SST范围是24.5~25.5 °C,最适Chl-a范围是0.16~0.20 mg/m3,月份是影响茎柔鱼CPUE的主要因子。研究表明：该海域茎柔鱼渔获主要为小型群体；小型群体生长发育期(2–3月)对渔场分布有重要影响,生长发育期前茎柔鱼集群度高,生长发育期后逐渐分散活动；单一影响因子与茎柔鱼CPUE相关性不显著,综合考虑其他环境因素及其交互影响是今后的研究方向。     

不同环境因子权重对东海鲐鱼栖息地模型的影响研究

鲐鱼（Scomber japonicus）是栖息在西太平洋沿岸的中上层鱼类,了解其栖息地分布及其与海洋环境因子的关系有助于合理开发和管理该资源。本文根据2003-2011年7-9月中国东海鲐鱼的生产数据,采用正态分布函数分别构建海表面温度（sea surface temperature,SST）、海表温梯度（gradient of sea surface temperature,GSST）和海表面高度（sea surface height,SSH）与作业次数的适应性指数（suitability index,SI）,基于不同权重的算术平均法（arithmetic weighted model,AWM）分别建立栖息地指数（habitat suitability index,HSI）模型,并用2012年7-9月生产数据进行验证。结果显示,7、8、9月各月最佳HSI模型的SST、STG和SSH的权重分别为0.5、0.25、0.25,0.8、0.1、0.1和0、1.0、0,利用2012年7-9月生产数据与环境数据对各月份最佳权重HSI模型进行验证,在HSI>0.6的海域,7、8、9月各月作业次数比重和产量比重分别为85.87%和92.55%,76.74%和86.69%,51.83%和56.11%。研究表明,不同月份的环境因子对鲐鱼渔场分布的影响程度不同,本研究为更好地预测鲐鱼栖息地奠定了基础。     

Analysis of bycatch in the South African midwater trawl fishery for horse mackerel Trachurus capensis based on observer data

The South African midwater trawl fishery targets adult horse mackerel Trachurus capensis. The bulk of the catch is taken by a single freezer-trawler, the biggest fishing vessel operating in South African waters. As fishing takes place off the south coast in ecologically sensitive areas, there are concerns about the potential impacts of this fishing operation on non-target species. Fishing behaviour and bycatch of this fishery from 2004 to 2014 were investigated by analysing observer records with regard to catch composition, volume and temporal and spatial patterns. The midwater trawl fishery was estimated to have caught 25 415 tonnes annually, with a bycatch of 6.9% of the total catch, by weight. There are species overlaps with various fisheries, namely the demersal trawl, small-pelagic, line, shark longline and squid fisheries, yet the total bycatch estimates from this fishery are generally small relative to catches taken in the target fisheries. Bycatch species with the highest average annual catches were chub mackerel Scomber japonicus, redeye roundherring Etrumeus whiteheadi, ribbonfish Lepidopus caudatus and hake Merluccius spp. Large-fauna bycatch species included sunfish Mola mola as well as a number of CITES II- and IUCN-listed species, such as Cape fur seal Arctocephalus pusillus, dusky shark Carcharhinus obscurus, smooth hammerhead shark Sphyrna zygaena and thresher sharks Alopias spp. The 97.9% observer coverage is high and the 6.9% bycatch rate low compared to other South African fisheries; however, due to the large size of the individual hauls (average of 46.3 t), the average sampling rate of 1.56% is low. Our analyses suggest that bycatch in the South African midwater trawl fishery has been lower than in other South African fisheries and similar fisheries elsewhere, but due to the combination of high catch volumes and low sampling rates, estimation errors for rare species are high and there is a substantial risk of incidental unmonitored bycatch of rare large fauna and aggregations of small fauna. This could be mitigated by spatio-temporal management of this fishery, to avoid fishing in high-risk areas, and the introduction of an electronic monitoring programme.     

基于个体模型的东海鲐鱼渔场形成机制研究

鲐鱼Scomber japonicus资源丰富,在我国近海渔业中占有重要地位。其渔场的形成受海洋环境的制约,本文确定鲐鱼运动和物理环境之间的响应关系,建立起了基于个体的东海鲐鱼生长洄游模型。结果显示,鲐鱼集群分布与捕捞生产渔场基本吻合,鲐鱼聚集主要受台湾暖流、大陆沿岸水、黑潮影响,往往集群在一定温度范围内并在冷暖交汇区温盐梯度大偏暖水一侧。在台湾暖流和沿岸水交汇的锋面附近、台湾暖流暖水舌前端、黑潮与中国大陆沿岸水形成的潮境区域均有大量的鲐鱼聚集,并形成渔场。产卵位置的变动使偏西产卵位置的鲐鱼由于受台湾暖流影响较大,鲐鱼会呈长带状大量聚集在台湾暖流和沿岸水的锋面附近,并使在台湾暖流暖水舌前端的聚集数量增多,而偏东的产卵的鲐鱼受黑潮影响较大,聚集分布范围较大,会使黑潮形成的锋面附近聚集数量增多,而使台湾暖水舌的前端的聚集量减少。正常产卵位置在生存率方面是最佳产卵位置。研究表明鲐鱼所处空间位置不同,会影响其集群的位置,用数值模型验证了物理环境会对鲐鱼的洄游和渔场的形成产生影响。     

基于空间自相关模型的西北太平洋日本鲭渔场时空变动研究

日本鲭(Scomber japonicus)是西北太平洋渔业捕捞的主要种类,了解其渔场变动对探究日本鲭种群分布、资源评估、开发利用和管理等意义重大.为获知其渔场的时空变动特征,本研究根据中国2014-2019年西北太平洋公海灯光围网渔业统计资料,运用全局莫兰指数、局部热点分析、重心迁移轨迹模型和标准差椭圆模型对西北太平...     

Impact of lunar cycle and swell on the daily catch rate of western rock lobster (Panulirus cygnus) using time series modelling

The western rock lobster fishery is one of the most valuable single‐species fisheries in Australia, valued at AU$300 million per year. The impact of environmental factors such as lunar cycle and swell on the daily catch rate of the western rock lobster (Panulirus cynus) is of particular interest in the stock assessment and management of the fishery. The variation in daily catch rates was examined for two periods (migrating period November‐January, non‐migrating period February‐June), at different depths in three management zones for three categories of lobster (undersize, legal size, and setose). Regression and transfer function models for relationships between catch rates and environmental data were considered and compared. The lunar cycle has a significant impact on the daily catch rates with c. 30% lower catch rate during the full moon and c. 20% higher catches near the new moon. This impact occurs mainly during the non‐migrating period both in deep water (40–100 m) and shallow water (<40 m). The swell on the day before fishing was also shown to be significantly related to the catch rate with an increase of c. 10–15% for an increase in swell from light to moderate or moderate to high. These environmental factors can be used to standardise catch rates to provide an improved abundance index for stock assessment. Also, management closures are being considered for 3–5 days over the low catch rate, full moon period to reduce fishing costs and lower fishing effort.     

长山群岛海洋渔业资源的平均营养级变化特征

根据长山群岛 1965-2016 年渔业统计资料,分析长山群岛海域主要捕捞渔获物产量、平均营养级 （Mean trophic level, MTL）、渔业均衡指数 （Fishing in balance index,FiB） 年际变化,探讨其海洋渔业资源利用状况,并利用小波分析方法研究52年来渔获物 MTL 周期变化特征。研究表明： （1） 长山群岛捕捞产量、MTL 和 FiB 指数呈阶段性变化; （2） 长山群岛渔业资源开发经历初期开发、扩张捕捞、过度捕捞、资源破坏等四个阶段,渔业资源环境正在逐渐恶化;（3） 受人类捕捞活动影响,MTL 在 15~19 年和 24~34 年两种时间尺度下呈周期波动,30 年为第一主周期,17 年为第二主周期。长山群岛渔业资源破坏日益严重,未来几年平均营养级将呈下降趋势。为防止渔业资源进一步衰退,应加强捕捞活动管理力度,落实海洋渔业资源保护制度;完善预警机制,构建海洋渔业资源监测系统;同时应积极调整长山群岛渔业产业结构,提高资源产出效率.     

胶州湾及其邻近水域渔业生物多样性的调查研究

根据2003年10月-2004年5月逐月采集胶州湾及其邻近水域作业的定置网和底拖网具渔获物的分析与测定，记述了该海区出现的106种渔业生物，并进行了定置网和底拖网的渔获物组成的比较，分析了种类组成特点及生物多样性的季节变化情况。结果表明，本调查区域渔获物以小型低值鱼类、经济无脊椎动物和经济幼鱼为主，渔获个体偏小。据此提出了保护近海生物多样性与合理利用近海渔业资源的一些建议。本次调查还首次记录了我国黄海沿岸罕见的蛇鳗科鱼类一长吻沙蛇鳗Ophisurusmacrorhynchus，为青岛近海的渔业生物多样性的研究增添了新的资料。     

Patterns in abundance,population structure and biology of knife prawn Haliporoides triarthrus on deep-water trawl grounds off eastern South Africa

The deep-water trawl fishery along the KwaZulu-Natal coast of South Africa targets several crustacean species, with the knife (or pink) prawn Haliporoides triarthrus contributing most of the catch. Logbook data of fishing effort and catch between 1988 and 2010 were used to assess the distribution and abundance of H. triarthrus on fishing grounds. Generalised linear models were used to quantify the effects of year, month and depth on catch rates. Standardised trends indicated a general decline in abundance between 1990 and 1998, followed by an increase between 2001 and 2008. Catch rates peaked in March, and they were highest between 200 and 499 m depth. Biological samples collected during commercial fishing were used to assess size and sex composition, growth rates and reproductive activity of H. triarthrus. Females became larger than males and mean carapace length (CL) varied by month. The youngest female cohort appeared in November (modal CL of 25 mm), and dissipated after two years (39 mm). Sex ratios were equal for all data combined, but fluctuated by month and CL. Few reproductively active females were recorded. Length-based methods and the standard von Bertalanffy growth function were used to estimate growth parameters (L_∞ and K) of females (40.6 mm CL and 1.06 y^–1) and males (35.2 mm and 1.27 y^–1) respectively. Our findings were compared with information on H. triarthrus from Mozambican waters.     

Using fine‐scale catch predictions to examine spatial variation in growth and catchability of Panulirus cygnus along the west coast of Australia

Puerulus settlement has been monitored throughout the western rock lobster Panulirus cygnus fishery for nearly 40 years. These data, in combination with indices of effort and water temperature, were used to produce recruitment‐catch relationships for each 1° transect of latitude in the coastal part of this fishery from Kalbarri to Cape Leeuwin, as well as at the offshore Abrolhos Islands (total of eight transects). The fine spatial scales of these models provided estimates of certain life history traits that are known to affect lobster catches between adjacent fishing ports. This catch modelling showed that the proportions of 3‐ and 4‐year‐old post‐settlement lobsters contributing to the catches varied markedly from the southern to northern transects, suggesting that juvenile lobsters grow substantially faster in the warmer northern and offshore waters of this fishery. These proportions provide accurate estimates of juvenile growth rates, which are vital in the construction of location‐specific growth algorithms required by the age‐structured models used in the management of this fishery. Model estimates of density‐dependent mortality were greater in the more densely populated centre of the fishery and markedly lower at the northern and southern limits of this species distribution. Annual increases in fishing efficiency were also found to be lowest at the northern and southern extremes of the fishery and greatest in the centre of the fishery, where technology advances and increased fleet mobility have enabled the fleet to increase efficiency by 1–3% each year. Catchability (q) was found to be most influenced by water temperatures in the cooler southern transects, whereas at the Abrolhos Islands, changes in water temperature produced almost no discernable change in q. The catch modelling was also used to quantify the impact of management changes introduced in the 1993/94 fishing season. Increased protection of female lobsters and an 18% pot reduction resulted in a 3–4% permanent reduction in the catch rates of lobsters throughout most of the coastal fishery, whereas at the offshore Abrolhos Islands, catch rates increased by c. 20%, presumably owing to a reduction in the level of pot saturation.     

A fifty-year production and economic assessment of common property-based management of marine living common resources: A case study for the women divers communities in Jeju,South Korea

We examined the conditions of successful common property-based management for coastal marine living resources, using a case of historically and anthropologically well established women divers communities on Jeju Island, South Korea, focusing on their decentralized work rules and production records. Due to their tight social network and work rule, the women divers have harvested coastal marine living resources with limited fishing pressure exclusively from their village fishing grounds for over 400 years. However, their harvest patterns have been mostly reactive to market prices, eventually requiring direct governmental regulations such as total allowable catch in some cases. Most recently, the communities have been experiencing multiple challenges: their aging population, water pollution in the coastal zone, competition with cultured products and imported seafood, and expanding barren grounds. These challenges demand a multi-scale/dimensional response if the women divers communities are to keep their village fishing grounds and communities sustainable.