Detection of potential fishing zones for neon flying squid based on remote-sensing data in the Northwest Pacific Ocean using an artificial neural network

Ommastrephes bartramii is a short-lived species of squid and reacts rapidly to changes in the regional environmental conditions of the fishing ground. Understanding the preferred range of key environmental variables and predicting potential resource distributions are critical to conserve and manage its resources. Commercial fishery data for the western winter–spring cohort of O. bartramii from Chinese squid-jigging vessels during 2003–2013 were used to evaluate a suitable range of three key environmental variables, sea surface temperature (SST), sea surface height (SSH), and chlorophyll-a (chl-a) concentration, and to explore potential fishing zones (PFZs) using an artificial neural network. The neural interpretation diagram and independent variable relevance analysis indicate that month, latitude, and SST had significant influences on the PFZ distribution of O. bartramii, yielding 21.78%, 23.91%, and 26.04% of contribution rates, respectively. Based on the sensitivity analyses, a high abundance of O. bartramii mainly occurred in the waters between 150°–165° E and 37°–42° N during July to August. Suitable ranges of environmental variables for O. bartramii were 11–18°C for SST, ?10 to 60 cm for SSH, and 0.1–1.7 mg/m³ for chl-a concentration, respectively. The back-propagation network model was well developed and could be used to predict the PFZ with 80% accuracy. The actual fishing grounds coincided with the predicted PFZ, suggesting that the established model of PFZ is effective in forecasting the potential habitat of O. bartramii in the Northwest Pacific Ocean.     

Synergistic application of oceanographic variables from multi-satellite sensors for forecasting potential fishing zones: methodology and validation results

This study uses synergistic application of satellite-derived chlorophyll concentration (CC), sea surface temperature (SST) and sea surface wind (SSW) for forecasting potential fishing zones (PFZs). PFZs are validated in near-real time through fishing operations and detailed statistical analysis of fishing operation data. CC and SST images were derived from Indian Remote Sensing Satellite-Ocean Colour Monitor (IRS-OCM) and NOAA-AVHRR, respectively, to delineate the oceanographic features exhibiting different oceanic processes. QuikSCAT/SeaWinds derived sea surface wind vectors were used to understand, quantify and demonstrate the variability of wind-induced water mass flow as well as their impacts on features/oceanographic process. Oceanographic features such as eddies, rings and fronts were found to be shifted according to the speed and direction of the wind. An algorithm was developed to compute water mass transport and feature shift. An improved methodology was developed and demonstrated using these prime variables, which are responsible for fishery resources distribution. PFZ forecasts were generated and validated through near-real-time fishing operations. The fishing operations data were taken from the logbooks of fishing vessels for detailed statistical analysis. On average, 80% of observations were recorded with more yield than monthly mean catch in the respective areas. A paired t-test showed statistically significant results.     

Quantifying light-fishing for Dosidicus gigas in the eastern Pacific using satellite remote sensing

The distribution and abundance of the fleet targeting Jumbo flying squid (Dosidicus gigas) in the Eastern Pacific is examined during the 1999 fishery season. The commercial fishery consists of a multinational jigging fleet, which fish at night using powerful lights to attract squid. The emission of light from these vessels can be observed using satellite-derived imagery obtained by the United States Defence Meteorological Satellite Program-Operational Linescan System (DMSP-OLS). In order to quantify fishing effort using lights, data on the distribution and abundance of vessels were obtained via satellite tracking using the ARGOS system. The distribution of the fishery as derived from light signatures was found to closely resemble that derived from ship location data. By using ARGOS data to calibrate DMSP-OLS images, we are able to estimate fishing effort in terms of the ‘area illuminated’ by the fishing fleet. Light signatures derived from DMSP-OLS were successfully used to quantify fishing effort, estimating the number of vessels fishing to within ±2 in 85 out of 103 satellite images (83%). High seas fishing was also quantified, with light signatures corresponding to a single fishing vessel observed in 11 out of 103 satellite passes during the fishery season (July-December 1999). This study examines how much light (in terms of area) is emitted by a single squid fishing vessel, and may prove to be a valuable tool in assessing and policing fisheries using satellite remote sensing.     

The influence of mesoscale eddies on a commercial fishery in the coastal waters of the Andaman and Nicobar Islands,India

Mesoscale eddies enhance the productivity in a stratified coastal environment by upwelling. The seas around the Andaman and Nicobar Islands have been found to have frequent mesoscale eddy activity. Commercial fishing grounds coincide with upwelling areas associated with cyclonic and anticyclonic eddies and also with areas between two adjacent eddies. There are different eddy zones supporting different types of fishing gears and fish. The current study aims at identifying the different zones of mesoscale eddies in the Andaman Sea and compares the productivity and fishing activity in each of them. Data collected from 454 commercial fishing trips in the Andaman Sea along with maps of sea level anomaly and Moderate Resolution Imaging Spectroradiometer (MODIS) global level 3 mapped thermal infrared (IR) daytime sea surface temperature (SST) from the Aqua and Terra satellites were used for the study. Known upwelling areas such as the periphery of anticyclonic and the core of cyclonic eddies showed higher catches in longlines, ring seines among the fishing gears, and among all the fish species groups. Downwelling areas such as the periphery of cyclonic and the core of anticyclonic eddies showed lower catches with ring seines and the fish species groups. Areas in between adjacent eddies were explored in this study and the fish captures in such areas were found to be different with types of fishing and the target fish group. The study shows results that link eddy activity with the performance of a fishery.     

Distribution of hotspots of chub mackerel based on remote-sensing data in coastal waters of China

Sustainable use of fishery resources requires the effective monitoring and managing of fish stocks and fish habitats. Chub mackerel (Scomber japonicus), distributed in the East China Sea and Yellow Sea, are mainly caught by purse seine fishing fleets from China, Japan, and South Korea. This study used fishery data from Chinese large lighting–purse seine fleets and environmental data including sea surface height (SSH), sea surface temperature (SST) from remote sensing, and temperature gradient derived from SST (GSST) during 1998–2010 to develop habitat suitability index (HSI) models. The HSI models were then used to identify hotspots for chub mackerel for each month. HSI models were developed separately for each of the three distribution areas defined for chub mackerel. According to the frequency distribution of the fishing effort with respect to three environmental variables, suitability index (SI) values were calculated and SI models for each environmental variable were established. The three SI models were combined into two different empirical HSI models: the arithmetic mean model (AMM) and the geometric mean model (GMM). The results showed that the AMM was more suitable than the GMM to estimate the HSI for chub mackerel. The monthly latitudinal variation trend of hotspots was consistent with that of the gravity centres of fishing effort in almost all months. Hotspot maps based on the predicted HSI values were validated by fishery data in 2011. This result indicates that the HSI model based on the AMM can reliably predict hotspots for chub mackerel in the coastal waters of China.     

Development of a spatial Decision Support System (DSS) for the Spencer Gulf penaeid prawn fishery,South Australia

The Spencer Gulf penaeid prawn fishery in South Australia has undergone a substantial increase in fishing efficiency (and profitability) mainly due to the implementation of adaptive harvest strategies requiring rapid response for change to harvesting plans. This paper describes the management background and the decision-making process leading to the development of a basic Decision Support System (DSS) that uses spatial information techniques and near real-time fishery-independent survey data. The system is implemented through linking an Oracle database to ArcGIS, Genstat and Splus. Two examples show the application of the DSS for optimal harvest timing and assessment of fishery sustainability. Fishery-independent survey data are used to assess stock and model population growth. The first example shows the information flow leading to a dynamic stock model and the estimate of value change as a function of harvest time. The second example shows how the DSS is used to validate and refine existing biological reference limits by evaluating long-term detailed data sets of the prawn population structure and catch dynamics. We conclude that it is important for the economic benefit and sustainability of the fishery to maintain and improve the collection of long-term data sets that are independent of commercial fishery statistics.     

Geometric correction and radiometric normalisation of NOAA AVHRR data for fisheries applications

Sea surface temperature (SST) has been found useful for locating potential fishing grounds (PFGs). Thermal data of the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) was acquired using a microcomputer (PC/AT 486) based Direct Reception and Processing Terminal (DRPT) developed in-house to map surface thermal fronts. Geometric correction using orbital ephemeris and ground control points (GCPs) resulted in locational accuracy of 1·73 km by 2·1 km. Besides, the corrections for artificially lowering SST in case of passes with large satellite zenith angles (LSZA) through a radiance normalization based on the mean vectors and dispersion matrices to make it comparable with small satellite zenith angle (SSZA) pass is presented in this letter.     

Dynamics of fisheries with prey reserve and harvesting

A model for two fish species and one predator in a patchy environment is formulated using a deterministic model to study the dynamics of fishery in two homogeneous patches, a free fishing zone and a refuge for prey reserve in which fishing is prohibited. The system is analysed around steady states; the criteria for local and global stabilities are established. The existence of bionomic equilibrium of the system is determined and the conditions for their existence are derived. The optimal harvesting policy is studied by using Pontryagin's maximal principle. Sensitivity analysis is carried out and it is observed that the populations are more sensitive to growth, dispersal and predation rates, least sensitive to the catchability coefficient. Statistical analysis is employed to estimate the parameters and to assess both the uncertainty in the model parameters and in the model-based predictions. Graphical representations of the model are provided.     

Habitat suitability analysis and identification of potential fishing grounds for swordfish,Xiphias gladius,in the South Atlantic Ocean

Swordfish, Xiphias gladius, is a highly migratory species of important commercial value and widely distributed in three oceans. Recently, the South Atlantic swordfish captured as by-catch in longline fisheries targeting tunas has contributed greatly to the overall Atlantic swordfish's landing. In this study, we have developed a habitat suitability index (HSI) model to examine the relationships between their spatio-temporal distribution and environmental factors and to identify potential fishing grounds for the swordfish in the South Atlantic Ocean using the Taiwanese distant-water longline fishery data and remote-sensing oceanographic data for 1998–2007. All the environmental factors considered – sea surface temperature (SST), mixed layer depth (MLD), sea surface height anomaly (SSHA), chlorophyll-a concentration (CHA) and ocean bathymetry (BAH) – were highly significant with most of the catch-per-unit-effort (CPUE) variation explained by SST. The most optimum habitat (i.e. hotspot) was found in the areas with SSTs of 27–28°C, SSHAs of??0.05 to 0.05 m, CHAs of 0.1–0.2 mg m^?3 and BAHs of??4000 to??4500 m. The arithmetic mean model with five environmental variables was found to be the most appropriate according to the information theory based on the evaluation of different empirical HSI models in combination with different environmental factors. The bimonthly geographic information system maps of the predicted HSI values were cross-validated by the observed CPUE, suggesting that the model can be used as a tool for reliable prediction of potential fishing grounds. Because the distribution and relative abundance of swordfish are sufficiently heterogeneous in space and time, the output of this study could provide a scientific basis for time–area closures based management of this species.     

Evaluation of sediment yield by using remote sensing and GIS: A case study from the Phulang Vagu watershed,Nizamabad District (AP), India

The primary objective of this paper is to identify soil erosion zones and to suggest appropriate measures for control of soil erosion using remote sensing, GIS and conventional technique in the Phulang Vagu watershed in the Sriramsagar catchment area of Andhra Pradesh. The digital imagery data of the study area is obtained from the IRS-IC (LISS-III) satellite whereas the toposheets and rainfall data of the study area were obtained from the Survey of India. Satellite images were interpreted to prepare land use/land cover maps by using ERDAS image processing system. Out of 725.983 km 2 of the study area, about 301.435 km 2 is wasteland which is identified as susceptible for soil erosion. Toposheets of the study area were used to prepare drainage and slope maps. Drainage pattern is mainly dendritic with a density of 1.26 km -1 and the stream slope is 0.00614. The arithmetric average method is used to find average annual rainfall. The above parameters were used to calculate the amount of soil erosion from the catchment area. It was found that 882.389 m 3 km -2 year -1 of soil is being eroded from the catchment area which is more than the value adopted in the design of Sriramsagar reservoir. Therefore soil conservation measures such as vegetative cover in the waste land are needed and 12 check dam sites have been proposed by superimposing drainage map and slope map in conjunction with land use/land cover map. With these soil conservation measures, the soil erosion could be kept within the design value of Sriramsagar reservoir.     

一种新的面向渔情预测的智能数据处理模型研究*

结合印度洋大眼金枪鱼渔业应用背景,提出一种新的面向渔情预测的智能数据处理模型。首先利用支持向量机（SVM）对样本数据进行训练,并运用模糊分类器对支持向量进行规则提取;然后对条件和结论分别进行可拓变换和传导变换,获得渔场动态知识。实验结果表明,获得的动态知识具有更强的解释性,对丰富渔情预测方法、解释渔场形成机制具有重要意义。     

Musculo-skeletal symptoms as related to working conditions among Swedish professional fisherman

The present study has confirmed the concern of previous investigators that professional fishing is a strenuous occupation. We have been able to show that complaints of symptoms from the musculo-skeletal system are common, and that they follow a logical pattern in terms of the influence of a few key parameters, such as age, number of years in the fishing trade, type of fishing and type of working tasks on board. There is reason to believe that these findings provide a sound basis for action-oriented research and a development programme focusing on reducing the risk of fishermen acquiring chronic chronic disorders of the musculo-skeletal system. In a subsequent article we shall present such a programme, which has been carried out for the Swedish fishery.     

基于多源参数的海洋数据合并技术研究

精准的高分辨率海洋环境数据,尤其是在低密度海面测量装置的海域中,对于渔业资源的规划和管理至关重要,并且可以提高渔情模拟预测的精度。在这项研究中,我们使用了两种经典方法：最优插值法（IO）和逐次矫正法（SCM）,用于合并卫星遥感和海洋浮标所测得的海洋环境数据。通过使用四种不同的算法来评估遥感海洋环境数据中的偏差矫正：（1）平均偏差矫正,（2）回归方程,（3）分布变换,以及（4）空间变换。海洋环境数据由NMSDC（国家海洋科学数据中心,National Marine Scientific Data center）提供,覆盖南海海域。将自2009年1月至2010年12月收集的海表温度(Sea surface temperature, SST)数据进行统计分析,将两种数据合并技术的性能通过比较,统计分析的计算表明,采用SCM可得到更好的结果。     

降雨空间不均匀性与雷达测雨空间平滑误差

用X波段气象雷达对降雨精细结构观测,获得了125 m高距离分辨率的降雨反射率数据。用此数据模拟计算了在与地基、空基的雷达分辨尺寸相当的模拟雷达空间平滑窗口内的不均匀性强度、基于Z-R关系的雷达测雨空间平滑误差等参数,并分析了这些参数间可能的相关关系。结果表明,降雨的小尺度不均匀性非常显著,甚至在1 km的雷达分辨尺寸内反射率不均匀度超过10 dB以上并不罕见,由此产生的雨强平滑误差不可忽略,甚至对于与地基雷达分辨率相近的0.5 km模拟雷达分辨率,其相对相误差可达30%以上。结果比较显示,用通常的1 km低分辨率雷达数据模拟计算会低估测雨平滑误差,其中对于4 km和3 km分辨率约低估25%,对于2 km以下分辨率约低估40%以上。     

中西太平洋金枪鱼围网渔场专题图服务

中西太平洋渔场是世界金枪鱼捕捞产量最高的渔场之一,由于金枪鱼属于中上层高度洄游鱼类,渔场变动较大,借助遥感产品辅助渔场中心判断是一种有效的手段。上海开创远洋渔业有限公司金枪鱼围网主要集中在中西太平洋,生产过程中利用海表温度、叶绿素、海面流场等海况产品辅助捕捞决策。文章基于地理信息和遥感技术,开发了后台数据自动处理软件,完成数据获取、解码、投影转换、专题图制图等流程,完成渔场专题图自动制图,并通过微信、FTP和网站提供服务,可以很好的为渔业分析与管理。     

The effects of sensor spatial resolution and changing grain size on fragmentation indices in urban landscape

Satellite images are now used as the primary source of spatial information for landscape pattern analysis. Choosing data of proper resolution has always been a big problem for landscape pattern analysis using satellite images. However, the effects of remote sensor spatial resolution on urban landscape fragmentation have never been reported. In this study, landscape fragmentation of Shanghai was analysed using land use maps produced from TM and IRS‐PAN images, attempting to discover the effects of remote sensor spatial resolution on urban landscape fragmentation. Four landscape fragmentation indices were computed along a 51 km long and 9 km wide transect cutting across Shanghai with a moving window to detect the behaviour of landscape indices along the gradient of land use zones. The results showed that fragmentation indices were sensitive to varied spatial resolution and grain size, indicating that fine resolution data and small grain size of about 7.5 m might be optimal for urban fragmentation analysis. The behaviour of landscape indices along the gradient of land use zones suggests that urban fragmentation can be distinguished as occurring in two phases: dissection introduced by roads and shrinkage caused primarily by urban sprawl.     

Gravity measurements and terrain corrections using a digital terrain model in the NW Himalaya

Areas recently gravity surveyed in the NW Himalaya are characterized by high-elevation and high-amplitude topographic undulations. A new method of applying combined Bouguer and terrain corrections using a digital terrain model is highly accurate and offers advantages over conventional techniques by saving efforts and being more flexible. Partitioning parameters for station-dependent inner-zone compartments and station-independent outer zones can be optimally selected for the desired accuracy requirements. A digital terrain database is used to obtain the outer-zone corrections. In the situation of the NW Himalaya surveys, a 1.2 km inner zone is divided into 112 compartments for each station and a digital terrain database containing nearly 16 000 data points for 30″×30″ compartments was applied using the computer program EFFECT.FOR, to compute combined Bouguer and terrain corrections for a 20 km range. The terrain corrections between 20 and 170 km were computed using National Geophysical Data Centre (NGDC) 5′×5′ gridded global elevation database. The magnitude of the terrain correction varies between 3 and 50 mGal. The effects of the 20 km range terrain correction are more pronounced on short-medium wavelength anomalies. The Swarghat gravity high is further enhanced while several high-frequency pseudo-anomalies disappear after applying the terrain corrections. The refined Bouguer anomaly varies from −160 mGal at the southern end of the section, to −310 mGal at the northern end, suggesting a Moho depth variation from 45 to nearly 60 km. The steepness of the northward negative gravity gradient, typical for the Himalaya, is considerably reduced after applying a terrain correction for the 170 km range.     

基于SPOT-VGT可见光/短波红外波段数据对AMSR-E土壤湿度的降尺度研究

基于SPOT-VGT数据,由短波红外、红和蓝波段反射率计算了表征地表土壤湿度的可见光—短波红外干旱指数(VSDI),通过对1km空间分辨率的VSDI影像进行空间升尺度处理,采用多种函数建立了25km空间分辨率AMSR-E土壤湿度数据与VSDI指数的关系,发现二者关系最符合S型曲线模型,拟合残差在空间上呈现随机分布的特征。基于S曲线函数关系下的1km预测土壤湿度和残差值,对AMSR-E土壤湿度进行降尺度模拟,得到1km空间分辨率的土壤湿度。将原始AMSR-E土壤湿度和实测数据对降尺度结果分别比较验证后,表明基于该方法获得的土壤湿度模拟精度较高。     

A composite DOP approach to excluding bottom reflectance in mapping water parameters of shallow coastal zones from TM imagery

In this paper we proposed a composite depth of penetration (DOP) approach to excluding bottom reflectance in mapping water quality parameters from Landsat thematic mapper (TM) data in the shallow coastal zone of Moreton Bay, Queensland, Australia. Three DOPs were calculated from TM1, TM2 and TM3, in conjunction with bathymetric data, at an accuracy ranging from ±5% to ±23%. These depths were used to segment the image into four DOP zones. Sixteen in situ water samples were collected concurrently with the recording of the satellite image. These samples were used to establish regression models for total suspended sediment (TSS) concentration and Secchi depth with respect to a particular DOP zone. Containing identical bands and their transformations for both parameters, the models are linear for TSS concentration, logarithmic for Secchi depth. Based on these models, TSS concentration and Secchi depth were mapped from the satellite image in respective DOP zones. Their mapped patterns are consistent with the in situ observed ones. Spatially, overestimation and underestimation of the parameters are restricted to localised areas but related to the absolute value of the parameters. The mapping was accomplished more accurately using multiple DOP zones than using a single zone in shallower areas. The composite DOP approach enables the mapping to be extended to areas as shallow as <3 m.