Distribution and migration of Japanese common squid, Todarodes pacificus, in the southwestern part of the East (Japan) Sea

Data on squid catches of Korean and Japan, water temperatures at depth of 100 m, and night-visible images of fishing boats collected in the East (Japan) Sea from 1970 to 1999 were analyzed to examine the distribution and migration of the Japanese common squid, Todarodes pacificus, in the southwestern part of the East (Japan) Sea. The main fishing grounds detected from squid catch in each grid (0.5° latitude × 0.5° longitude) by Korean squid fishery and night-visible images provided by the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) were situated in the southwestern part of the East (Japan) Sea. The distribution and migration route was illustrated from squid catch in each grid and DMSP OLS image. In years of high catches, the fishing grounds were situated mainly between Ulleung Island and the eastern coastal waters of Korea, while in years of low catches they were situated between Ulleung Island and the Yamato Bank in the central East (Japan) Sea. The center of fishing activity began moving northward from around the Korea/Tsushima strait to the northern boundary of the Tsushima Warm Current in March, reaching into the Yamato Bank in September, and then returning to the strait by February. The northward and southward migration routes differed; the northward migration route occurred closer to the mainland coast of Korea than the southward migration route did. This work suggests T. pacificus begin their northward migration almost 2 months earlier than previously suggested.     

Distribution, abundance and biological interactions of the cutlassfish Trichiurus lepturus in the southern Brazil subtropical convergence ecosystem

The distribution, abundance and biological interactions of the cutlassfish Trichiurus lepturus in the southern Brazil subtropical convergence ecosystem were studied from demersal trawl surveys conducted along the continental shelf and upper slope from Cape Santa Marta Grande (28 °36′S) to Chui (34 °45′S) between 1981 and 1987. Trichiurus lepturus was more abundant at bottom water temperatures of over 16 °C and in the 40–120 m depth range. From late spring to fall, juveniles of 5–30 cm total length (TL) were found in coastal waters, subadults (TL 30–70 cm) mainly in inner shelf waters and adults (TL > 70 cm) in coastal, inner and outer shelf waters. Higher catches of subadults and adults were found associated with thermal fronts in the western boundary of the Subtropical Convergence or with a shelf break upwelling observed in summer. The standing stock in a 58 000 km² shelf area estimated by the swept area method, ranged from 3066 t (±46% CI) in September 1981 to 37814 t (±22% CI) in January 1982. Correlation between occurrences of different size groups of cutlassfishes and other fishes caught in 250 bottom trawl hauls was analyzed. A positive correlation between cutlassfish and juvenile weakfish, Cynoscion guatucupa, was associated with similar spatial distribution but also indicated trophic competition.     

Catch rates, size structure and sex ratio of Melicertus kerathurus (Decapoda: Penaeidae) from an Aegean Sea trawl fishery

Otter-trawl catch rates and population structure of the prawn Melicertus kerathurus were studied at the fishing ground of Thermaikos Gulf (North Aegean Sea, Eastern Mediterranean), where the stock is exploited both by otter-trawlers and the artisanal local fleet. Sampling was conducted on board commercial trawlers on a monthly basis in two consequent open fishing seasons (October to May 2000–2001 and 2001–2002) resulting to a total of 70 hauls. Samples were also obtained through experimental trawling (24 hauls) during the closed season. The main trawling ground is located near the border between the outer and the inner gulf, and along the western and northeastern coasts of the outer gulf in depths ranging from 35 to 70 m (most frequently at 40–50 m). Catch per unit effort (CPUE) varied significantly with month but not with fishing season (mean CPUE 3.18 and 1.78 kg/h for the 2 successive years) or depth. Catches were at maximum (up to 7.5 kg/h) at the beginning of the open season in autumn and decreased sharply as the season proceeded (<2.5 kg/h), which is likely to be due to induced fishing mortality in the preceding months, to prawn dispersal and/or to its tendency for longer burrowing. Commercial fishing trips consisted of multiple, short efforts when catches were high, whereas low yields during winter–spring led to less hauls of longer duration: ln CPUE = 2.974 − 2.047 ln HD, r = −0.57. Prawn size ranged from 17 to 60 mm CL, showing a consistent difference in favor of females. A weak recruitment to the fishery was observed from autumn through winter, while, as shown by experimental trawling, the main recruitment pulse to the fishery occurs just prior to the season's opening. The delayed arrival of the prawns on the fishing ground during the second fishing season, accompanied by smaller prawn size and shallower exploitation depth, was possibly related to decreased autumn rainfall. In both years, sex ratio showed a temporal pattern, which seems to be the result of sex-related differences in fishing vulnerability, in timing of inshore migration and in mating mortality.     

An assessment of the west winter–spring cohort of neon flying squid (Ommastrephes bartramii) in the Northwest Pacific Ocean

In the Northwest Pacific, the squid jigging fisheries targeted the west winter–spring cohort of neon flying squid (Ommastrephes bartramii) from August to November. Total annual catch by the Chinese mainland squid jigging fleet during 2000–2005 ranged from 64,100 to 104,200 t. The unique life history of this squid species makes the use of traditional age- or length-structured models difficult in evaluating the effect of intensive commercial jigging on this stock. We fitted a modified depletion model to the Chinese jigging fisheries data to estimate the squid stock abundance during 2000–2005. Monthly biological data were randomly sampled from the five squid jigging vessels during the fishing seasons. Effects of using different natural mortality rates (M) and three different error assumptions were evaluated in fitting the depletion model. Based on sensitivity analyses, the log-normal error model was found to be preferred for the squid assessment. The assessment results indicated that the initial (pre-fishing season) annual population sizes ranged from 199 to 704 million squid with the M value of 0.03–0.10 during 2000–2005. The proportional escapement (M = 0.03–0.10) for different fishing seasons over the time period of 2000–2005 ranged from 15.3% (in 2000) to 69.9% (in 2001), with an average of 37.18%, which was close to the management target of 40%. Thus, the current fishing mortality of the squid jigging fishery was considered to be sustainable. We inferred its annual maximum allowable catch ranging from 80,000 to 100,000 t. This study suggests that the modified depletion model provides an alternative method for assessing short-lived species such as O. bartramii.     

Standardising the CPUE for the <Emphasis Type="Italic">Illex argentinus</Emphasis> fishery in the Southwest Atlantic

The catch per unit effort (CPUE) is a widely used index for assessing the abundance of exploited populations in fishery management. To obtain appropriate CPUE values, it is essential to standardise catch-effort data from fisheries. This task is particularly important for squid fisheries because squid generally have a short life-span and are vulnerable to environmental variability, and thus effective fishery management should take such factors into account. In this study, we analysed unit catches of paired vessels operating under similar fishing conditions to calculate their relative fishing power (RFP) in order to standardise the CPUE of the Taiwanese fleet jigging for Illex argentinus in the Southwest Atlantic. To evaluate the appropriateness of the method, we used a logbook dataset covering eleven years (1993–2003), in which 93.5% of the total catch during the period was included. The results indicate that 98.7% of the fishing effort can be standardised according to the estimated RFP. Compared to nominal CPUE, the standardised CPUE values projected an explainable temporal pattern, indicating an increasing trend in abundance from 1995 to 1999 and a subsequent sharp plunge from 1999 to 2003. However, the RFP was not related to apparent physical factors of the vessel, such as gross tonnage or vessel length. Our evaluations suggest that the RFP method is appropriate for standardising the CPUE, so that it can serve as an abundance index that reflects the annual recruitment size of the squid fishery, because the quality of the method can potentially take possible affecting factors into account in order to satisfy the general assumptions of standardisation criteria. However, the effects of varying the settings of parameters should be carefully examined prior to applying this standardisation method to other squid fisheries.     

中东大西洋中部海域中上层鱼类资源结构与渔场分布

为了解中东大西洋中部海域中上层鱼类资源结构与渔场分布,对2007-2014年入渔FAO34渔区3.11和1.32小区(毛里塔尼亚专属经济区)从事中上层鱼类捕捞的7艘国内渔船的生产数据进行了分析。结果表明,我国入渔船只数量、入渔渔船总产量和作业渔船平均日产量均呈现先增加、后减少的趋势,且在2011年入渔渔船总产量和作业渔船平均日产量到达最大值,2012年入渔船只数量到达最大值。渔获种类主要包括沙丁鱼(Sardina pilchardus)、短体小沙丁鱼(Sardinella maderensis)、金色小沙丁鱼(Sardinella aurita)、日本鲭(Scomber japonicus)和竹筴鱼(Trachurus trachurus),各渔获种类的渔获量年际间波动较为明显。月均产量在17.2~23.6 t/haul,最高值和最低值分别出现在12月和8月;月均总产量在1 279.0~2 414.2 t,最高值和最低值分别出现在1月和8月,12月至次年3月为渔汛旺期。渔场季节变化现象明显,夏秋季向北移动,冬春季向南移动,20.0°~20.8°N、17.4°~18.0°W区域为高产量海域。该海域中上层鱼类洄游现象明显,这可能主要与该海域的不同洋流在不同月份的强弱变化有关,该海域整体渔业资源呈现一定衰退现象。建议渔船入渔该海域从事中上层鱼类捕捞持谨慎态度,加强该海域渔业资源的研究与保护。     

Fishing grounds of bottom-liners on the continental shelf of south-east Brazil

Abstract The space and depth distribution of the bottom-line fisheries on the continental shelf of south-east Brazil were analysed, and an attempt was made to identify the areas and depths where fishing effort is concentrated to delimit the main fishing grounds. Four main fishing grounds were identified based on the effort and catches between 1975 and 1985. These were, in decreasing order of importance: north of Espírito Santo state, near the Abrolhos archipelago; adjacent to Rio de Janeiro state, under the influence of Cabo Frio upwelling; north of São Paulo state, encircling Alcatrazes archipelago; and the outer edge of the Rio de Janeiro and São Paulo state continental shelves, between the Guanabara and Sepetiba bays. The concentration of the fisheries, the greater catches and the best productivity indices were found in outer and deeper areas along the edge of the continental shelf. There was a concentration of fishing effort and higher catches in deeper grounds, from the north to the south of the regional fishing area. The bathymetric distribution of the fisheries showed that they intensified from 30 m depth to the outer edge of the continental shelf. The fishery productivity indices increased towards a depth of 50 m, but fell thereafter. Fishing activities were lowest during the winter season for the whole region, but intensified during the summer-autumn or spring-summer seasons.     

Temperature conditions in the Argentine chub mackerel (Scomber japonicus) fishing ground: implications for fishery management

We describe the seasonal migrations of Argentine chub mackerel ( Scomber japonicus ) into the fishing ground in relation to sea surface temperature conditions and analyse the temperature evolution during the fishing season on the basis of 1955–97 time-series. The upper temperature limit for the presence of schools was around 19°C. At higher values, most schools leave coastal waters (< 50 m) for the shelf. An inverse relationship was observed between catches per unit of effort (CPUE) of the inshore fishery and sea surface temperature. The highest standardized CPUE values corresponded to temperatures lower than 19°C. Above this temperature, the probability of obtaining a standardized CPUE higher than 1 was extremely low, and the standard deviations were minimal. The economic benefit from catches was also analysed through the different months of the fishing season. It was found that the mean benefit corresponding to temperatures lower than 19°C exceeded approximately 15 times that obtained at higher temperatures. A simple fishing strategy was proposed to the commercial fleet in order to improve the economic benefit of the catches. The migratory pattern followed by mackerel during the spawning period was also analysed in relationship to other environmental factors like food availability. Zooplankton composition, size structure and abundance in coastal and shelf waters are described, and their implications for feeding ecology of larvae and adults of the species are discussed.     

峰值法和数据包络分析法在中国远洋鱿钓渔业方面的应用与比较分析

概述了PTP和DEA法的基本理论，并将其应用于我国的远洋鱿钓渔业，结果表明，1999年我国北太平洋鱿钓渔业的“捕捞能力”尚未得到充分的发挥，仍有潜力可挖；影响西南大西洋鱿钓渔业“捕捞能力”的主要因素是制冷能力，钓机数，集鱼灯和水下灯，而船长，船舶总吨位，功率和舱容仅为次要因素。通过应用，本文分析比较了这两种方法的特点；PTP法长于在时间序列方面的一个纵向的分析，能够在一定程度上反映渔业技术和资源随时间的变化而发生的变化，而DEA法则擅于在捕捞单位间进行横向的“能力”比较，并能对影响“捕捞能力”的因素进行有效的灵敏度分析。     

浙江省单拖渔业现状分析与研究

利用2001~2006年浙江省单拖渔业典型性调查数据和2005~2008年的单拖作业监测资料,从浙江省单拖捕捞力量和产量分布、渔获对象和资源密度变化及经济效益、劳动力组成等几个方面进行了初步分析。结果表明,近几年浙江省单拖作业船数保持在2200艘左右,产量在40×104t左右,单船净利润存在年间波动,以2005年最高;单拖作业渔场分布较广,渔获物以头足类和中下层鱼类为主;近年来经济鱼类比例下降,而其它低值鱼类比例上升。文章最后提出了当前浙江单拖渔业存在的问题,并提出了相应管理建议以供参考。     

Loggerhead turtle (Caretta caretta) bycatch in Canadian pelagic longline fisheries: Relative importance in the western North Atlantic and opportunities for mitigation

Little is known about the ecology of loggerhead turtles, Caretta caretta, in Canadian waters. However, Canada's eastern waters off the Scotian Shelf, Georges Bank and Grand Banks appear to be seasonal foraging habitats based on dates and locations where they have been captured as fishery bycatch. Estimates derived from data recorded by the international observer program (IOP) and used for this study suggest that thousands of mostly immature loggerheads have been captured in the Canadian pelagic longline fishery (PLF) in the western North Atlantic since 1999. These data suggest that the PLFs for tuna and swordfish are among the most important causes of incidental capture. Although U.S. and Canadian bycatch estimation methods differ and uncertainty associated with the estimates is high, it is clear from the IOP data that bycatch in the Canadian PLF is substantial and roughly within the same magnitude as that reported for the entire U.S. fleet in the North Atlantic for the same period (1999–2005). Analysis of bycatch observer data from the Canadian PLF and other empirical data suggests that fishing at temperatures below 20 °C using fish rather than squid bait and size-18 circle hooks could reduce loggerhead bycatch and mortality. However, research is needed to identify the best options and their commercial viability. Loggerheads that use Canadian Maritime waters are one of the least studied groups of loggerheads in the world, so systematic long-term studies on the ecology of loggerheads in Canada would help fill important information gaps and assist in developing effective recovery plans for this species.     

The effect of LED lights on trap catches in Finnish inland fisheries

Trap fisheries can provide catches of high quality, and unwanted bycatch can be released with high survival. Light attraction could be an effective way of increasing trap catches, but research results are largely lacking. Experiments to test the effect of LED lights in trap-net fishing were conducted in two Finnish lakes where fishing targeted Eurasian perch Perca fluviatilis L. and roach Rutilus rutilus (L.). LED lights (white, green, red, blue and combinations) were attached inside the traps. The use of LED lights did not increase fish CPUE. Contrary to expectation, Eurasian perch catches were higher in traps without LED lights. Significant variation in CPUEs was observed, but without interaction with light treatments. The LED lights tested in this study do not increase the effectiveness of trap fishery targeting Eurasian perch and roach in Finnish lakes in the ice-free season.     

The effect of lunar cycle,tidal condition and wind direction on the catches and profitability of Japanese common squid Todarodes pacificus jigging and trap-net fishing

Jigging with artificial lights (squid jigging) and deploying of large scale trap-net (also known as a set-net in Japan), are the major methods to capture Japanese common squid Todarodes pacificus in western Japan. Squid jigging is a highly selective fishing method. However, it consumes large amount of energy for steaming to the fishing ground and for lighting. In contrast, trap-net fishing requires substantially less energy but its capture efficiency is strongly influenced by its stationary mode of capture. The primary objective of this study was to analyze how various environmental and biological factors such as the lunar cycle, tidal condition, wind direction and squid abundance affect the capture efficiency of squid jigging and trap-net fishing. We analyzed the effect of these factors on squid catch in five Fisheries Cooperative Associations located on four islands in Nagasaki Prefecture, western Japan. Our analysis shows that squid catch in jigging and trap-net fishing is mainly influenced by the lunar cycle but also tide and wind direction play a marked role. In addition, squid abundance significantly affects the catches in trap-net fishing. Recommendations are made to improve the overall profitability of squid fishing by proper choice of the capture method, location and season.     

基于栖息地指数的南海北部枪乌贼渔情预报模型构建

根据2009年~2014年南海捕捞信息网络获取的南海北部200 m等深线以内近海底拖网渔业数据,结合环境遥感数据,构建南海北部枪乌贼类(Uroteuthis sp.)栖息地指数(habitat suitability index,HSI)模型。选取海表水温(sea surface temperature,SST)、海面高度(sea surface height,SSH)和叶绿素a浓度(chlorophyll-a concentration,CHL)等环境因子,采用一元非线性回归建模,并分月份采用最小二乘法确定各环境因子的权重系数,从而建立南海北部枪乌贼类的栖息地指数综合模型。构建的模型能够有效解释渔场分布与环境要素之间的关系,并可从模型中推断各环境因子的最适范围和变化趋势;单位捕捞努力量渔获量(catch per unite effect,CPUE)高的渔场主要分布于HSI大于0.5的海域,其他HSI高的海域可能为潜在渔场。对不同因子权重系数的研究发现,叶绿素a浓度是影响渔场分布的重要因素。对模型的验证结果表明,其准确率达到75%以上。该研究表明,基于不同权重系数的HSI模型能够较好地预测南海北部枪乌贼渔场。     

基于灰色系统的北太平洋柔鱼渔汛特征分析及旺汛期预测

柔鱼(Ommastrephes bartramii)是大洋性经济头足类,是我国远洋鱿钓渔船重要的捕捞对象.分析柔鱼渔汛特征并预测旺汛期,有助于柔鱼资源的合理开发与利用.本研究根据2013-2017年北太平洋柔鱼渔业生产统计数据,以每日平均渔获量(CPUEday)作为资源丰度,利用分位数的方法划分旺汛期;结合灰色波形预测...     

Fisheries catches and the carrying capacity of marine ecosystems in southern Brazil

The carrying capacity of marine shelf ecosystems in southern Brazil for harvestable species is analyzed by (1) quantifying the amount of available primary production appropriated by fisheries catches, (2) evaluating the trend in the mean trophic level of fisheries, and (3) simulating the ecosystem effects of “fishing down the food web” in an intensively exploited shelf region. Fisheries utilize ca. 27 and 53% of total primary production in the southern and south-eastern shelf regions, respectively. Regional variation in the carrying capacity appropriated by fisheries results from differences in the primary production, catch volume and trophic transfer efficiencies. Overall, fisheries landings do not display a trend of decreasing trophic level with time due to the collapse of the sardine fishery and the recent increasing of offshore fishing for higher trophic level species, mainly tunas and sharks. However, the simulations show that fishing down the food web through fisheries that target small pelagic planktivorous fishes, while at first increasing catches in intensively exploited regions, has the potential of decreasing yields, by interrupting major energy pathways to exploited, high-trophic level species. The consequences of these results to the design of precautionary measures for future fishing policies are discussed.     

Results of a short study on by-catches and discards in pelagic fisheries in Scotland (UK)

Observers were placed on pelagic vessels in the Scottish fisheries for mackerel (Scomber scombrus), herring (Clupea harengus), “maatje” herring (herring caught just before their first spawning) and argentines (Argentina silus) to monitor by-catch composition and discarding practices. A total of 67 days was spent at sea, 11 on the argentine fleet, 28 on the herring fleet, 12 on the “maatje” herring fleet and 16 on the mackerel fleet. The level of by-catch generally ranged from <1% to around 2.5% of the total catch. The argentine fishery took a significant proportion of blue whiting (Micromesistius poutassou) (approx. 10% of the overall catch) but this was landed and sold in the market. The greatest range of by-catch species was found in the argentine fishery, including 11 species of fish and one species of squid. Discarding rates in the fisheries varied, with herring and argentine fisheries showing no discards, the mackerel fishery a discard rate of around 4% and the “maatje” herring fishery a discard rate of around 11%. By-catches included small numbers of gannets (Morus bassanus) but no marine mammals. If the sampled trips were representative, results indicate that marine mammal by-catch events typically occur during less than one in 20 hauls in the fisheries studied. A larger scale study is needed to confirm this. Cetaceans were sighted in the vicinity of the fishing boats during 4% of observed fishing activities.     

Fishing strategy choices of purse seines in the Mediterranean: implications for management

ABSTRACT:   An observer's sampling scheme, that employed fisheries scientists onboard fleet vessels was used to examine temporal fishing tactics and strategies affecting catches of the purse seine fishery in the Mediterranean. The month, water depth and the fishers' behavior were found to have an effect on total and Trachurus spp. retained catches, with fishers' behavior explaining the largest percentage of the data variation. The distance of the fishing ground from port and the market price modulated both the retained catches and the fishing location choice. Results confirmed that fishers while in a specific fishing ground developed strategies that would allow them to retain, and thus land, the best possible combination of landings × market value. The current findings also revealed that, when constrained by physical and economic conditions, fishers preferred to minimise risk rather than maximize landings. The observed major switches in fishing strategy were attributed to fishers' risk attitude response towards higher profitability. As the Mediterranean fishery system is mainly based on control effort and technical measures regimes, the current findings are discussed in the light of the need to consider additional information to management plans and decisions.     

A predator–prey model for evaluating the spatial behaviour of fishing fleets: a case study of the red grouper Epinephelus morio fishery of Yucatan,Mexico

A predator–prey model was applied to the red grouper Epinephelus morio fishery from Yucatan, Mexico, with the aim of understanding the spatial behaviour of a mid-sized fishing fleet. The heterogeneity of the environment was considered, and different habitat quality levels were determined to address environmental differences. The behaviour of the fleet was also evaluated based on a simulation of restricted fishing areas (RFA). The model was applied utilising 5 years of information on catch and fishing effort (1973–1977). Four levels of habitat quality were defined (low, medium, high and exceptional). The total costs and revenue for a fishing expedition in the areas of exceptional habitat quality were higher due to their location farthest from the base port. The fleet was most efficient during the winter at locations in the eastern continental shelf, with the number of these areas clearly decreasing in the autumn. The model simulation of the RFA showed a total revenue reduction of 7–27 % in scenarios of RFA for adult protection. When the RFA was implemented for the protection of juvenile fish, the total revenue was not reduced, indicating that this type of RFA might be a feasible management strategy for a sustainable fishery.     

闽南-台湾浅滩渔场单船拖网作业调查与分析

根据2009—2010年闽南-台湾浅滩渔场单船拖网作业监测调查资料和生产统计数据,阐明单船拖网作业的渔业地位、渔场分布、网具类型,着重分析该作业渔获种类组成及主要捕捞对象的资源动态。结果表明:单船拖网作业产量位居闽南-台湾浅滩渔场各种海洋捕捞作业的首位,大吨位、大功率渔船数量连续多年不断增长;渔具型式以有翼单囊网具为主;部分渔船使用的拖网网囊尺寸远远低于国家标准;带鱼、二长棘鲷幼鱼损害现象较为严重;秋季8—10月蓝圆鲹和鲐鱼群体绝大多数个体可达到最小可捕规格。调查研究结果还表明,2002年以来单船拖网渔业资源结构已发生较大变化,生命周期短、营养级较低的蟹类、枪乌贼类、乌贼类和虾类资源渔获比重显著增长;原优势种类绿布氏筋鱼资源已出现严重衰竭;二长棘鲷资源量逐年减少,渔获群体明显趋向小型化、低龄化。