Stock structure and resource management of hairtail <Emphasis Type="Italic">Trichiurus japonicus</Emphasis> based on seasonal broods around the Bungo Channel,Japan

Declines in landings of the hairtail Trichiurus japonicas indicate the need for more effective management of this species. Hairtail spawning peaks occur twice yearly in the Bungo Channel, in spring and autumn. Relationships between hairtail stock and brood seasonality were examined to determine if an association between either and a decline in landings existed. Stock assessments show that the biomass of both spring and autumn hairtail broods from within and around the Bungo Channel are decreasing, with a rapid reduction in spring-brood stock abundance after 2007 largely responsible for decreased landings. Yield and spawning per recruitment analyses indicate current fishing pressure to be higher than several reference points. We suggest that fishing pressure needs to be reduced by at least 20% of the current level for this fishery to remain sustainable, as the projected stock abundance and catch demonstrate that the current fishing pressure is unsustainable. Analysis of time-series data of recruits per spawning revealed spring-brood recruitment to have been strong in year classes 2003 and 2005. Of various options available for improved management of this fishery, we propose that fishing pressure should be reduced in the years following the appearance of strong year classes to increase future biomasses and landings.     

金枪鱼曳绳拟饵研制与海上试验结果

报道了金枪鱼曳绳钓拟饵的设计制作以及海上试验结果。与传统拖毛钓作业相比，上钩率按尾数计提高了48．5％，按重量计提高了106．5％。该拟饵使用效果上钩率达到日本进口拟饵水平。并且具有易于操作，使用寿命长等特点。     

A transdisciplinary research of coastal fisheries co-management: the case of the hairtail <Emphasis Type="Italic">Trichiurus japonicus</Emphasis> trolling line fishery around the Bungo Channel,Japan

Under the coastal fisheries co-management regime in Japan, local fishers play important roles in deciding on and implementing local management measures. Therefore, using the case study of a hairtail trolling line fishery, we conducted a transdisciplinary research with fishers, processors, government officers, etc. Taking social and biological factors into account, we defined management criteria and targets (resource, economic, human community, and local food culture) in collaboration with local fishers. We chartered local fishing vessels to determine parameters that were easily understood by local fishers. We established a local consultative committee comprising fishers, processors, and distributors, and developed a fish distribution strategy to nurture the local hairtail food culture. The integrated effects of various management scenarios were evaluated by the operating model. We found that co-ordinated management by both the trolling line fishery and purse seiners in the neighbouring prefecture was required to achieve targets. Two realistic scenarios are recommended: a conservative scenario that could achieve targets even with few strong year classes, and an adaptive scenario that protects strong year classes, but relies on a higher frequency of these. We shared these results with the local fishers and government officers, which led to actual improvements in management measures.     

Evaluation of artificial and natural baits for the pot fishery of the sand crab Ovalipes punctatus (De Haan, 1833)

We compared the luring effectiveness of artificial bait made from fish waste with natural baits in pots targeting the sand crab Ovalipes punctatus in the East China Sea. Bait types used were fish (mackerel), minced fish (heads of greenling) and two artificial baits made mostly from fish waste and starch. The first two need frozen storage but artificial bait does not. Three fishing operations were conducted in May 2010 and in each forty pots (10/treatment) were fastened along a bottom line. Results for the three operations had catch data for 30 pots/treatment. The number of crabs captured was 496, of which 206 (41.5%) were caught in pots containing fish, 116 (23.4%) in those with minced bait, and 93 (18.8%) and 81(16.3%) in pots baited with the two artificial baits, respectively. Fish was significantly more attractive than minced bait and artificial baits, but no differences were detected between the other baits. Natural baits disappeared almost entirely by the time of hauling, with only 1% of the fish and 5.3% of the minced bait remaining; artificial bait remained almost intact (96.3–100%). The artificial bait catch was approximately half of that of fish bait, but it only contained 30% fish waste. Furthermore, if catch returns are calculated according to the bait's fish content their efficiency seemed higher, ranging from 88 to 100 crabs/kg of fish waste vs only 69 crabs/kg of fish.     

延长拖网伏季休渔期的渔业资源养护效应

海洋伏季休渔制度是当前中国最主要的渔业资源管理制度之一,并在实践中得到不断调整与完善,新的海洋伏季休渔制度已于2017年发布实施。为论证新制度延长拖网休渔期的渔业资源养护效应,本研究依据2015—2017年每年5月东海区拖网大面定点调查资料,利用Ricker动态综合模型,从拖网的渔获结构特征和带鱼(Trichiurus japonicus)的种群动力学过程视角开展了相应的量化分析研究。研究结果表明, 5月拖网利用主体为带鱼和小黄鱼(Larimichthys polyactis),带鱼和小黄鱼的性成熟比例分别为92.04%～95.57%和13.82%～29.55%,幼鱼比例分别为74.94%～88.90%和0.03%～4.19%;带鱼种群经过4.5个月的休渔,其单位补充量资源量、单位补充量渔获量和平均渔获质量与3.5个月休渔期相比较,分别增加了7.04%、8.96%和20.78%。以上结果表明,提前并延长拖网休渔期,东、黄海主要经济渔业资源带鱼与小黄鱼的产卵群体和幼鱼得到进一步保护,资源增殖效果随着休渔期的不断延长而增加,新制度的休渔时间设置更趋合理。但由于开捕后的带鱼与小黄鱼渔获仍主要以当龄鱼为主,有必要同时配套执行现已颁布的最小网目尺寸和开捕标准等其他渔业资源管理措施,以确保伏季休渔制度主导下的渔业资源养护效果能真正得到巩固,渔业资源的种群结构能够得到切实好转与不断合理化。     

Evaluation of large-scale stocking of early stages of brown trout, Salmo trutta, to angler catches in the French–Swiss part of the River Doubs

Around 500 000 brown trout, Salmo trutta L., alevins are stocked annually in the 24‐km section of the River Doubs under study. All the alevins stocked in the period 1994–1996 were identifiable by fluoromarking their otoliths with tetracycline chlorhydrate. Anglers' catches, between June 1997 and September 1998, comprised trout aged 1+ to 7+ , but most (90% +) were 2+ to 3+ or 4+ , with the majority at 2+ and 3+. There was no significant difference in the size for a given age between marked and unmarked angled trout. The contribution of stocked fish in anglers' catches was around 22% for the 1995 cohort. The contribution of stocking (cohorts 1994 to 1995–1996) to the 1998 catches was around 23% (95% confidence limits: 19–27%). The estimated recapture rate was three to four trout per 1000 alevins stocked for the 1995 cohort. The major contribution (78%) of natural recruitment to anglers' catches suggests that the fishery management based on natural recruitment is still realistic in this part of River Doubs.     

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.

     

Development and comparative test of squid liver artificial bait for tuna longline

ABSTRACT:   We have been developing an artificial bait for longline tuna fishing using the liver of the Japanese common squid Todarodes pacificus , a waste product of the squid fisheries industry, as the primary component. Three control test operations using the artificial bait and natural squid were conducted during January 1998, 1999 and 2000. During these operations, we compared the angling performance of the artificial bait with that of the natural squid. Some tuna was caught using the artificial bait; however, the hooking ratio for the artificial bait was less than that for the natural baits. Despite this, there was no significant difference between the hooking ratio by artificial bait and natural squid. In addition, species selectivity in the by-catch, a characteristic particular to this artificial bait, was observed. In the present paper, we discuss the hooking ratio and the reduction in by-catch of the artificial bait compared with natural bait.     

Explaining recreational angling catch rates of Eurasian perch,Perca fluviatilis: the role of natural and fishing‐related environmental factors

Angling catch records are frequently used to reveal fish population developments. It is therefore important to understand the determinants of angling catches. This study focused on angler‐related, biotic and abiotic factors influencing catchability of Eurasian perch, Perca fluviatilis L. A multi‐lake (21 lakes) study based on angling diaries collected in Mecklenburg‐Vorpommern, Germany (2006/2007), found that angler‐related factors such as fishing experience, species preference and bait/lure type had a large impact on perch catch rates. Additionally, environmental conditions (nutritional status and water transparency) affected either the size or the number of perch caught by anglers. Catch rates varied seasonally, which was confirmed by an experimental fishery on a gravel pit (2008). This portion of the study showed that altered food availabilities in the course of the year caused food limitation in perch, which in turn facilitated high catch rates and female‐biased exploitation in autumn. It is concluded that both angler‐related and abiotic factors interact affecting perch catch rates and size of perch captured in recreational angling.     

Analysis of Fishery Records from Cow Green Reservoir, Upper Teesdale, 1971–1980

Apart from some irregularities reflecting changes in permit costs (1975) and the effects of drought (1976), there were increases in angler-visits, catch per angler-visit and number of fish caught during the first 5 years of the fishery. Thereafter, there were about 1000–1500 angler-visits per season, a mean catch of 1.0–1.2 trout per angler-visit and an annual catch of 1200–1800 trout. Between 1971 and 1980 the mean weight of the fish caught fell from 472 to 349 g. During the period 1976–1980 the mean catch per angler-visit was 1.2 fish. This compares favourably with results from a selection of upland and lowland British reservoirs. The mean weight of individual trout caught was 362 kg and this value is typical of both stocked and unstocked upland reservoirs. The mean annual catch during 1976–1980 was about 2 kg ha^?1. This is similar to the values observed in other unstocked upland reservoirs. The gross yield from such reservoirs can be increased by stocking but the limited data available suggest that at stocking rates above about 5 kg ha^?1 the net yield (i.e. weight caught — weight stocked) becomes negative.     

海州湾秋季坛子网网目选择性研究

2018年秋季,利用囊网内径网目为25、35、45、55 mm的坛子网在黄海海州湾渔场N 35°02.335′,E 119°24.842′附近海域进行了11网次试验。从Logistic选择性模型、坛子网不同网目对主要渔获物小黄鱼的选择性曲线、渔获物组成、幼鱼比例及选择性分析等方面,研究坛子网网囊的选择性。试验结果显示,坛子网九月主要渔获物为小黄鱼、带鱼和三疣梭子蟹;随网囊网目尺寸的增加,渔获物质量逃逸率及尾数逃逸率均迅速增加,网目尺寸为55 mm时其值均超过80%,且质量逃逸率及尾数逃逸率的值比较接近;渔获物组成中,小黄鱼、银鲳和三疣梭子蟹幼体比例非常高,基本全为幼体,带鱼幼鱼比例也超过70%;根据小黄鱼的可捕体长,获得坛子网针对小黄鱼的最适网囊网目尺寸,为(40.59±3.19)mm。研究结果可为我国海州湾渔具管理以及渔业资源的可持续发展与管理提供科技支撑。     

黄、东海渔业资源群落结构变化研究

为了解黄海和东海渔业资源群落结构的变化,基于2013年6月(夏季)和9月(秋季)黄、东海渔业资源底拖网调查数据,对渔业资源种类组成、优势种、渔获量空间分布、群落多样性和群落结构进行了研究。结果显示,共鉴定渔业种类185种,其中底层鱼类93种、中上层鱼类31种、甲壳类48种、头足类12种和贝类1种。在鱼类中,鲈形目种类最多,27科47属56种,占鱼类总种类数的45.2%。夏季优势种为鳀(Engraulis japonicus)、脊腹褐虾(Crangon affinis)、带鱼(Trichiurus lepturus)和小黄鱼(Larimichthys polyactis),秋季优势种为三疣梭子蟹(Portunus trituberculatus)、小黄鱼、鳀和带鱼,优势种季节波动不大。秋季平均单位时间渔获量为46.60 kg/h,高于夏季(39.35 kg/h)。秋季航次调查中渔业资源较夏季更为集中,主要分布在长江口和吕泗渔场附近,其他断面渔获量较低。夏季航次群落多样性指数高于秋季航次。CLUSTER聚类分析表明,黄、东海渔业生物群落可分为2组,夏、秋季2组界线变动不大,2组聚类的形成可能受水温和长江径流影响。     

Vital population statistics of the exploited eel stock on the Swedish west coast

The population dynamics and exploitation of the yellow eel (Anguilla anguilla (L.)) stock on the Swedish west coast were studied. In contrast to a generally observed reduction in the recruitment of glass eels in Europe, including in Swedish waters, there was no indication of a decline in the total eel fishery yields along the Swedish west coast. Long-term records of daily catches as well as by test fishing results also shown that this stability in eel fishery yields has not been maintained by an increase in fishery effort, as the catch-per-unit-efforts in the past 20 years have been more or less unchanged. These findings implied that the number of recruits to the fishery has been rather stable, possibly indicating that density-dependent factors at the elver and yellow eel stages may moderate variations in glass eel recruitment. Total instantaneous rate of mortality was estimated from records on eel length distribution in the professional fyke-net fishery. The estimated total mortality rate in an isolated archipelago population on the west coast was chosen as an approximation of the instantaneous rate of natural mortality and net emigration in the west coast eel stock. The differences between these two estimates could, thus be regarded as the mortality that occurred due to fishing. It was found that the eel fishery was very intense and most fish were caught in small sizes, resulting in a low escapement rate of maturing fish.     

拖网囊网网目及其对东海带鱼选择性的研究

本文介绍了东、黄海拖网囊网网目的套网系列试验结果，指出当带鱼的刺鱼体周相当于网目内周时，其体长一般大于这种网目对带鱼的50％选择体长。文中比较了按照刺鱼体周求算网目内径同用50％选择体长决定网目内径的不同之处。根据网目内径与刺鱼体长的相关式，提出保护东海带鱼资源的拖网囊网最小网目内径为56毫米，并依据网目的选择性及带鱼的生物学资料，讨论了采用这一网目尺寸的可行性。     

The 1993 collapse of the Lake Kinneret bleak fishery

Bleak, Acanthobrama terraesanctae Steinitz, constituted an important fishery in Lake Kinneret, Israel, accounting for ≈ 60% of the total commercial harvest, but less than 10% of the total fisheries income for the entire lake. The market demand of 900–1000 t annually has maintained relatively constant harvest pressure since the 1970s. The fishing season of 1992/93 was the last time bleak were harvested commercially. In 1993/94 the fishery collapsed; less than 10% of previous harvests was caught, and most fish were below commercial size. An overview of the bleak fishery during the past 60 years is presented, with evidence indicating that the collapse was the result of two interdependent events relating to harvest-induced stress: (i) a long-term shift in harvested fish size (age) that began in 1982; and (ii) two consecutive seasons of overharvest that led to the depletion of 2–3 year classes and the excessive recruitment of young-of-year of a single year class.     

A preliminary appraisal of the contribution of recreational fishing to the fisheries sector in north-west Trinidad

Abstract An assessment of the recreational fishery in north-west Trinidad was made by questioning participants about the principal fishing methods used, location of activities, catches, effort and cost of fishing. Surface handline methods (live baiting [à la vive] and trolling) and rod and line (banking) were the most common methods used and were pursued mainly in the summer months (April to August). Total fish landings from the fishery were estimated at 1000 t year^-1, equivalent to about 10% of commercial catches for Trinidad. The principal species caught were kingfish, Scomberomorus cavalla (Cuv.), carite, Scomberomorus brasiliensis (Cuv.), cavalli, Caranx hippos (L.), snappers, Lutjanus spp., and groupers, Epinephelus spp. Many of the fishermen sold their catch to offset the costs of the fishing trip and thus competed with commercial fishermen. Recommendations for monitoring and possibly regulating the fishery through a licensing scheme are made.     

Relationships between Stocking and Anglers' Catches in Draycote Water Trout Fishery

The trout fishery at Draycote Water was investigated during the 1980 fishing season. Fish stocked were batch-marked according to the date of introduction by freeze branding, and catch data were obtained by the cooperation of anglers. Population estimates were made at the end of the fishing season using gill nets and mark-recapture techniques. Of the 32,960 marked brown and rainbow trout stocked, 69.8% were caught and declared by anglers. Returns of rainbow trout were better (78.1%) than those of brown trout (44.2%). Over 90% of all fish caught were taken within 45 days of stocking. Catch per unit effort fluctuated widely but was closely associated with stockings of fish. Catchability (Q) of stocked fish was found to diminish rapidly with time after stocking. At the end of the fishing season the estimated population of marked trout was 4045 (2 × SE = 250), compared with a theoretical number (stock less total catch) of 10,802, giving a mean daily apparent natural mortality, made up of the true natural mortality plus the undeclared catch, of 1.36%.     

人工鱼礁物品经济学特性

人工鱼礁是21世纪中国兴起的渔业生态修复工程之一。在社会主义市场经济下，物品的特性及其经济特点决定了人工鱼礁产品、服务的多样性。本文以现代公共物品经济学分析了我国正在进行的人工鱼礁建设，初步分析认为人工鱼礁物品划分为公共性人工鱼礁、私人性人工鱼礁、俱乐部性人工鱼礁和拥挤性人工鱼礁等4类，其物品各自特性表征出的投资主体、决策程序、管理模式、经营方式和渔业修复功能等不同。本文在讨论分类人工鱼礁经济学基础上，初步提出当前我国人工鱼礁建设的5个建议：分类指导建设；区域规划先行；资源增殖为主；注意投入导向；规范建设程序。     

Potential bycatch of seabirds and turtles in hook-and-line fisheries of the Itaipava Fleet, Brazil

The decline of populations of certain seabirds and sea turtles around the world is partly related to their incidental capture in large-scale fisheries. However, the impacts of small-scale fisheries on endangered seabirds and sea turtles, being carried out in many places around the world, have been largely neglected by scientists and governments. We monitored 178 fishing days and described a range of poorly known hook-and-line commercial fisheries carried out by the Itaipava fleet, southeastern Brazil, composed by 497 vessels and deploying hooks from 18°S to 35°S. Seven fisheries were defined: fast trolling for tuna and tuna-like species, slow trolling for Bigeye tuna, handlining, surface longline for Dolphinfish, pelagic longline for Swordfish, bottom dropline, and pole-and-line with live bait. We observed bycatch of 47 seabirds of six species and 45 turtles of four species. Capture rates were higher for the surface longline for Dolphinfish (0.15 birds/1000 hooks and 1.08 turtles/1000 hooks), slow trolling for Bigeye tuna (0.41 birds/day) and handlining targeting Yellowfin tuna (0.61 birds/day). Endangered Spectacled petrel (Procellaria conspicillata), Atlantic Yellow-nosed (Thalassarche chlororhynchos), and Black-browed (T. melanophris) albatrosses were the main seabirds caught. Immature Loggerhead turtles (Caretta caretta) and immature or adult Leatherback turtles (Dermochelys coriacea) were the main sea turtles affected by the surface longline for Dolphinfish. Monitoring the fleet and bycatch levels, development of mitigation measures, establishment of educational programs, government control over the fleet, and enforcement, are urgently required for the hook-and-line fisheries described in the present study.     

金枪鱼延绳钓渔获性能研究进展

金枪鱼延绳钓渔获性能主要按目标鱼种和兼捕物种渔获效率进行评价。对其研究有助于改进延绳钓渔具渔法, 提高目标鱼种捕捞效率和减少兼捕。本文以时间顺序为主对国内外关于金枪鱼延绳钓渔获性能研究的文献进行梳理, 从钓具选择性、钓钩深度、饵料选择性、环境因素以及钓具浸泡时长等方面概括了金枪鱼延绳钓渔获性能的研究进展, 并提出存在的不足和建议, 为金枪鱼延绳钓渔获性能的研究提供参考。前人研究取得的成果有: (1)不同鱼种最佳作业深度和钓具浸泡时长不同; (2)较大尺寸的圆形钩能减少兼捕; (3)拟饵也具有选择性, 鱼类饵料和蓝色染色饵料有利于减少兼捕; (4)具体水层的环境因素对延绳钓渔获性能影响较大。建议今后金枪鱼延绳钓渔获性能研究应: (1)确定钓钩最佳沉降速度和深度; (2)分水层建立不同物种渔获性能预测模型; (3)针对不同的目标鱼种探索最佳尺寸和钩形; (4)研究不同气味和颜色的饵料或拟饵对物种选择性的影响; (5)考虑诱饵、钓钩类型和尺寸和钓具浸泡时长对渔获率、死亡率、兼捕率和兼捕物种释放后存活率的潜在协同效应。