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1.
Two species of ling, Genypterus blacodes (Forster in Bloch & Schneider, 1801) and G. microstomus (Regan, 1903) have been recorded from New Zealand and Australian waters; a third species, G. tigerinus (Klunzinger, 1872) has been recorded from Australia. Specimens of ling collected from northern, central, and southern localities in the New Zealand Exclusive Economic Zone (EEZ), and specimens of G. blacodes from Australia were shown to be similar with respect to partial sequences of mitochondrial (mt)DNA, and morphometric and meristic characters. DNA sequences of part of the cytochrome b and control region showed that G. blacodes from Tasmania and New Zealand differed by 1/291 and 4/284 nucleotides respectively, but there was much greater genetic differentiation between G. blacodes and G. tigerinus (14/291 and 14/284 nucleotides), and between G. blacodes and G. capensis (23/291 and 8/284 nucleotides). MtDNA haplotypes within New Zealand show that G. blacodes is subdivided into northern and southern stocks. It is concluded that ling in New Zealand represent a single species referable to G. blacodes, and that G. microstomus Regan is a junior synonym.  相似文献   

2.
Mass occurrences of the terebratellid brachiopod Magellania venosa with more than 200 individuals·m?2 are reported from the fjords Comau and Reñihué in the northernmost region of the Chilean fjordland, whereas more southern fjords do not show these high numbers of the largest living brachiopod. This is an exception to earlier observations that the abundance of M. venosa on the Chilean shelf is positively correlated with increasing latitude. As the sympatric scleractinian coral Desmophyllum dianthus also occurs in unusually high numbers in the fjords Comau and Reñihué, the hydrographical regime and its associated environmental conditions in these fjords may be responsible for these mass occurrences.  相似文献   

3.
Seventeen demersal fish species collected during a commercial line fishing trip off northern New Zealand are listed together with data on abundance, location, and habitat. These are the first records for the area; 15 are the most northerly records for the species and major range extensions are recorded for Centroscymnus owstoni, Deania calcea, Etmopterus lucifer, Pseudophycis barbata, and Hyperoglyphe antarctica. A prespawning aggregation of ling, Genypterus blacodes, is recorded for the first time from this region.  相似文献   

4.
Monthly fishery survey data of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea from2003 and 2013 were employed to evaluate the variation in the resource distribution and biological characteristics(especially body length and sex ratio) in the population on a decadal scale.The results indicated that the small yellow croaker migrated from the Shawai fishing ground to the Dasha fishing ground in spring and was mainly distributed in the central and western parts of the Dasha fishing ground in April and May.Larimichthys polyactis in the Dasha fishing ground migrated eastward to offshore wintering grounds in autumn and reached the central Dasha fishing ground in October and November.The small yellow croaker entered the western waters of the Shawai fishing ground in winter.A large number of age 0+ fish occurred in the Shawai and Jiangwai fishing grounds in October of 2003 and 2013.The body lengths of the spawning stock and wintering stock in 2013 were larger than those in 2003,and the monthly sex ratios(female to male) were significantly less than 1 in both years.The monthly distribution of this fish in the southern Yellow Sea was consistent with a previous finding that "the stock migrated between the wintering grounds in the west of Jeju Island and the Lüsi spawning grounds" but tended to move more northward,with the spawning grounds extending outward.In the past decade,body length variation experienced a decline after an increase,rather than a steady decrease.The sex ratio in the single-stick stow net showed a tendency to increase over the decade,but was either less than or more than 1 depending on the fishing gear;therefore,further studies should be conducted to determine the sex structure.  相似文献   

5.
Nephrops norvegicus is an essentially sedentary species of lobster that forms the basis of valuable fisheries in the northwest Atlantic and western Mediterranean. Fishers exploiting a sedentary stock are likely to visit the most profitable (highest catch rate) areas first. Such spatial targeting of fishing effort is likely to have important consequences for stock monitoring and assessment. We used underwater television surveys of Nephrops burrow densities on the Farn Deeps grounds, northeast England, to describe changes in abundance and distribution between the beginning and end of a winter fishing season. Above a threshold of c. 0.6 burrows m–2, overwinter depletion increased with burrow density, consistent with fishing effort being targeted at the highest densities. A simple simulation model showed that this pattern of mortality is an expected consequence of spatially targeted fishing behaviour. The model also predicted that there is decreased spatial variability in density after fishing. An overall decrease in variability was not evident from the survey data, but geostatistical analysis indicated that there was “flattening” of the density profile along a north‐south axis, consistent with the dominant direction of commercial trawling. We concluded that Nephrops fishers are able to find and exploit the highest densities of their target species. A potential consequence is that catch per unit effort (CPUE) data used to monitor trends in this stock potentially could mask declines in stock abundance. CPUE might be more effective if analysed at finer spatial scales, but this is not currently possible. In the absence of these fine scale commercial data, fishery‐independent surveys (e.g., underwater television) are an important source of information on trends in stock abundance.  相似文献   

6.
The mean effective fishing area (EFA) of a Japanese-type crab trap fishing for Geryon maritae on the northern South West African red-crab grounds was calibrated as 2 160 m2. The commercial fishery uses traps covered with 90-mm mesh. In order to be able to use the density results obtained by this survey from traps covered with 60-mm mesh, a preliminary mesh selectivity study was carried out. The carapace width at 50-per-cent retention for 90-mm mesh was estimated as 72 mm. Based on the EFA results, it seems that most commercial fishing takes place in areas of crab density varying between 46 and 231 crabs·ha?1, but that densities can reach ～510 crabs·ha?1. It is suggested that crab traps would fish more efficiently on the northern South West African crab grounds if longlines were set across the depth contours rather than in a longshore direction.  相似文献   

7.
Jean-Noël Druon   《Marine Policy》2010,34(2):293-297
The feeding and spawning habitats of the overfished Atlantic bluefin tuna (BFT) are mapped in the Mediterranean Sea and used in the present proposal for selecting restricted fishing grounds. The feeding habitat is mainly traced by oceanic fronts of satellite-derived temperature and chlorophyll while the spawning habitat is mostly characterized by an important heating of surface waters. The proposal recommends opening the fishery in feeding areas in case the BFT stock is low (current situation). Only spawning areas at its latest stage could be opened once the stock has recovered to its optimum yield. Due to the possible concentration of fishing vessels if fishing areas are restricted (e.g. four-fold increase with a 1/16th restriction of the Mediterranean Sea) the inspection activities could be better targeted. Identified spawning grounds, opened or closed to fishing, could also be particularly monitored by control operations. Within the authorized areas, the habitat maps would guide fishermen to the favourable habitat reducing their costs. The habitat guided management could be able to adapt the spatial and temporal distribution of the effort to the requirements of both the fisheries’ control and the resource. Its implementation is likely to protect the stock (a) by apparently decreasing illegal fishing which accounts in the recent years for more than 1/3rd of total catches, (b) by protecting the spawners to ensure a suitable recruitment and (c) by distributing the effort to respect the population structure. The first species studied is the emblematic bluefin tuna which is at high risk of collapse due to overfishing. The approach is a priori transposable to other epipelagic species of commercial importance.  相似文献   

8.
Knysna Estuary supports an estimated 30 full-time and 200 part-time subsistence fishers involved in bait collection, mud crab harvesting, and fishing. The mud prawn Upogebia africana dominates the bait-fishery, with estimated catches amounting to about 3% of the standing stock, suggesting sustainable use. Harvest of Marphysa spp. and Gorgonorhynchus dayi is conducted in a destructive manner. Most of the value of fishing lies in the setline catches of spotted grunter Pomadasys commersonnii and white steenbras Lithognathus lithognathus, whereas small species and individuals, particularly Cape stumpnose Rhabdosargus holubi, are also caught with handlines. Indications are that the linefishery is also sustainable at present. The subsistence fishery is worth an estimated R0.7-R1.1 million per annum, with full-time fishers earning at least R11 000-R17 000 per annum from the estuary. Currently operating under recreational regulations, the fishery is poorly controlled and fails to reach its full potential. The main threat to the estuary from damaging harvests of bait species, such as Marphysa spp. and G. dayi, should be discouraged through heavy penalisation of buyers and traders. Sales of mud prawn could probably be legalised. If off-take rates are found to be sustainable, sales of certain fish species could be legalised if access to the fishery could be effectively controlled under a co-management arrangement.  相似文献   

9.
In order to avoid conflicts when spatially explicit rules are implemented, it is critical to understand the spatial distribution of fishing effort, the migration patterns of fishermen and the use of temporary fishing camps. The migration of fishermen is a process shaped by historical patterns of resource availability, in addition to economic and political factors. We present an example in which a temporary fishing camp used for extraction of benthic resources (Loco: Concholepas concholepas) changed into a permanent one during the study period. Throughout the study period fishing effort (trips) was closely related to the productivity of the different fishing grounds, with more trips directed to the most productive areas. The conversion from a temporary to a permanent fishing camp did not improve the efficiency of the loco fishery, but did allow better access to alternative resources (surf clams) on nearby fishing grounds. The succession from simple shelters to a permanent ‘caleta’ is a common situation along the Chilean coast, motivated originally by resource availability and more recently by the creation of the TURF system. In particular the TURF system converts temporary (resource driven) movements of fishermen into rigid stationary caletas, which creates a number of problems. Temporary fishing camps are common when fishing grounds are far from the base port, but they require specific administrative tools in order to achieve sustainable fisheries management.  相似文献   

10.
Bayesian methods are useful in fisheries stock assessment because they provide a conceptually elegant and statistically rigorous approach to making decisions under uncertainty. The application of Bayesian stock assessment methods in the management of Namibian orange roughy Hoplosthethus atlanticus within the 200 mile EEZ of Namibia is reviewed. Time-series of relative abundance are short and their reliability in indicating abundance trends is uncertain. The development of informative prior probability density functions (pdfs) for the constants of proportionality (q) for hydro-acoustic, commercial trawl swept area, and research trawl swept area indices produced statistically consistent prior estimates of absolute abundance for each of the three grounds where more than one index of abundance was available. The posterior pdfs for stock assessment model parameters were used to account for uncertainty in evaluations of the potential consequences of alternative harvesting policies under a stock reduction model in which catch removals were assumed to account for any declines. It appears that all orange roughy stocks off Namibia have been depleted below the limit reference point (50% of long-term unfished biomass). However, the stock reduction model could not easily account for the large declines in indices on the four fishing grounds over the period from 1995 until 1999 when the informative priors for q were applied. In the 2000 stock assessment, the Bayesian procedure was updated to account formally for uncertainty in model structures that could explain the decline in abundance. The possibility of very low stock abundance could still not be discounted when these uncertainties were accounted for. Although this most recent methodology applies more statistical rigour, its complexity has hindered its acceptance in Namibia. However, if it is worth quantifying risks and uncertainties in future stock assessments for the provision of precautionary management advice, it is proposed that the assessment protocols adopted be probabilistic to account for uncertainty in model parameters, that careful attention be given to subjective judgements about their inputs and the representation of uncertainty within them, and that, where appropriate, alternative hypotheses about stock abundance and mechanisms for catchability and stock decline be taken into account.  相似文献   

11.
Abstract

In September 1986, dense concentrations of freshly spawned hoki (Macruronus novaezelandiae) eggs were located in eastern Cook Strait. A follow‐up exploratory trawl survey of Cook Strait and the east coast of the South Island, in August and September 1987, located concentrations of spawning hoki in canyon features in Cook Strait, off the Kaikoura coast, and off Banks Peninsula. The largest concentration, 14 km long, 4 km wide, and up to 150 m thick occurred in Cook Strait Canyon, with catch rates of hoki up to 48 t h?1. Gonad conditions of male and female hoki showed they were actively spawning. Catch rates in Cook Strait Canyon were comparable to the main fishery on the west coast of the South Island but were much lower off Kaikoura and Banks Peninsula. Hoki associated with spawning concentrations were not feeding. Bycatch species were mostly ling (Genypterus blacodes) and spiny dogfish (Squalus acanthias), and both were preying on hoki. Spiny dogfish were also feeding on spawned fish eggs. The possible stock structure of hoki is discussed.  相似文献   

12.
Nursery grounds of the tarakihi Cheilodactylus macropterus (Bloch & Schneider) were discovered in 1963–72 mainly off the south‐western coast of the North Island, in Tasman Bay, along the entire eastern coast of the South Island, and around the Chatham Islands. They occurred at depths of 20–100 m, and mostly between 10 km and 30 km from shore. The tarakihi nurseries had a dense and varied invertebrate bemthic epifauna dominated by sponges and small corals. Few signs of nurseries were found in. other New Zealand waters, in spite of the existence of major spawning grounds there. It is not known with which spawning grounds the various nursery grounds are linked.

The Tasman Bay nursery ground is 18–33 km wide and about 75 km long, with a surface area of about 2000 km2. There is a rich demersal fish fauna (37 species were recorded) dominated by tarakihi, red gurnard Chelidonichthys kumu (Lesson & Garnot), snapper Chrysophrys auratus (Bloch & Schneider), and leathei'iacket Novodon convexirostris (Guenther). The young tarakihi occur at depths of 20–45 m and concentrate during winter in the warmer deeper water. They first appear in trawl catches in summer, towards the end of their first year (assumed birthdate is 1 March), and stay on the nursery until the age of 3 y. They occur in the deeper water off the nursery during their fourth and fifth year and depart during their sixth year, possibly for the spawning grounds off the west coast of the South Island. The mean lengths at the ages of 15, 27, and 39 months were 12.6, 18.0, and 24.0 cm respectively in 1970. There was some variation in growth rate within the nursery ground, but the age groups could nevertheless be recognised easily from, length frequency modes. Monthly modal lengths showed that growth slows down in winter. Evidence for fluctuations in year class strength was found; year classes 1966 and 1969 were weak and year class 1968 was strong.

The vulnerability of tarakihi less than 4y old to commercial New Zealand trawl gear is low, and the local fishing fleets do no serious damage to the habitat on the nursery grounds. However, a large part of the tarakihi nursery grounds off the east coast of the South Island lies outside the territorial fishing zone. Intensive fishing on these grounds by large foreign vessels using heavy trawl gear could have an adverse effect on the habitat of the young tarakihi in this region.  相似文献   

13.
The hottentot seabream Pachymetopon blochii is a small-sized (maximum 2.67 kg) sparid endemic to southern Africa. It is an important target in South Africa's Western Cape traditional linefishery, particularly in the absence of more valuable pelagic species (such as Thyrsites atun and Seriola lalandi). In 2000, South Africa's linefishery was declared to be in a state of emergency, and commercial fishing effort was consequently reduced by 70%. A subsequent increase in stock biomass and intraspecific competition, coupled with environmental changes, were hypothesised to have thereafter altered the growth rate of hottentot, from 2000 to 2010. This study aimed to revise outdated age–growth models for the hottentot by using modern techniques (sectioned otoliths), and to compare age–growth relationships before and after the declared linefish state of emergency. The maximum age observed was 19 years, with no difference in the growth rate between sexes (p = 0.39–0.43) or time-periods (p = 0.96). Although the growth rate did not change, there is evidence that the age structure of the stock changed between time-periods as a result of changes in fishing pressure between 2000 and 2010. The enhanced recent growth model for hottentot, described as Lt = 418.063 (1 – e?0.104(t – [?4.709])) (pooled sexes; n = 206), indicates a considerably slower growth rate for this species than was proposed previously using whole otoliths and has major implications for effective stock management.  相似文献   

14.
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.  相似文献   

15.
余为  陈新军  易倩 《海洋学报》2016,38(2):64-72
海洋初级生产力在海洋生态中扮演重要角色,其变化影响了海洋渔业的潜在产量。本文根据2004-2013年中国鱿钓组提供的西北太平洋柔鱼(Ommastrephes bartramii)捕捞数据和海洋遥感净初级生产力数据,研究了柔鱼冬春生西部群体资源量变动与净初级生产力的关系。结果发现,柔鱼渔场范围内净初级生产力在经度方向上呈明显的季节性变化,冬春季低,夏秋季高。捕捞月份7-11月对应的适宜净初级生产力范围分别为500~700 mg/(m2·d)(以碳计),500~800 mg/(m2·d),500~1000 mg/(m2·d),500~800 mg/(m2·d)和300~500 mg/(m2·d),最适净初级生产力分别为700 mg/(m2·d),600 mg/(m2·d),700 mg/(m2·d),600 mg/(m2·d)和400 mg/(m2·d)。7-11各月最适净初级生产力平均纬度与捕捞努力量纬度重心呈显著正相关关系(P<0.05),说明了捕捞努力量位置在渔场中不是随机分布,可能受最适净初级生产力的纬度分布的影响。柔鱼年间资源丰度与各年3月份净初级生产力以及7-11月份平均净初级生产力大小显著正相关(P<0.05)。推测每年柔鱼资源量大小可能是由3月份产卵场海域和7-11月捕捞月份渔场净初级生产力水平交互作用的结果。研究表明,异常环境条件(厄尔尼诺和拉尼娜事件)对柔鱼产卵场和渔场的净初级生产力具有显著影响,但调控机制不同。  相似文献   

16.
不同环境因子权重对东海鲐鱼栖息地模型的影响研究   总被引：4，自引：1，他引：3  
易炜  郭爱  陈新军 《海洋学报》2017,39(12):90-97
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。  相似文献   

17.
Canyons play a fundamental role in enhancing the abundance and diversity of marine organisms through the transport of organic matter and food resources, the presence of complex physical habitats and the absence of trawl fishing. During four baited lander deployments carried out in the Bari Canyon (Southern Adriatic Sea, Central Mediterranean), at depths of 443–788 m, about 43 h of video records were taken, for a total of 619,200 video frames. A total of 12 benthopelagic fish species (five chondrichthyes and seven osteichthyes) were identified. The blackspot seabream (Pagellus bogaraveo) was the most often observed fish species. The depth of 787 m represents a new depth record for this fish in the Adriatic Sea. Groups of up to 40 individuals of P. bogaraveo were attracted to the bait and were shown in single frames. The individuals were observed both exploring the area and feeding actively on the bait. The European conger (Conger conger) was recorded at each deployment. Clear scavenger behaviour was also observed in this teleost fish and in the shark Etmopterus spinax. The shark species Centrophorus granulosus and Hexanchus griseus, which are considered ‘vulnerable’ on the published IUCN Mediterranean Regional Red List, were also recorded but, although attracted by the bait, they were never seen feeding on it. Other fish species, harvested on fishing grounds, such as Merluccius merluccius, Helicolenus dactylopterus and Polyprion americanus, were also recorded. This study represents the first in situ documentation, at very low impact, of the fish fauna in the Bari Canyon, providing new insights into its small scale distribution and behaviour, the first in situ direct observation of the variable feeding behaviour of P. bogaraveo and its gregarious habits, as well as indicating that this canyon could act as a refuge area for species that are vulnerable to fishing on the open slope.  相似文献   

18.
2020年6月15日—7月15日,我国首次中国毛虾(Acetes chinensis)限额捕捞试点于江苏连云港实施。本研究提取62艘毛虾网船在限额捕捞期间的421700条北斗船位数据经纬度、航速、航向等信息,运用缓冲区叠加分析法、DBSCAN密度聚类算法、平均中心算法、核密度估计以及数据库查询对捕捞努力量等管控要素进行分析研究。结果显示,所有毛虾网船累计作业239个航次、1942个网次,捕捞过程分为航行、抛锚布网、等待渔获、收渔获、停航等5个状态,中国毛虾捕捞状态船位点呈直线分布,总捕捞时长为4413.73h,82.4%的单网次捕捞时长为1.5—3.5h,各网次捕捞产量呈现多核心空间分布模式,总捕捞努力量为108106343 m~2·h,计算62艘的捕捞总产量值约为2328 t,比上报产量高12.6%;本文通过北斗船位数据解译和提取捕捞努力量以计算中国毛虾捕捞产量及资源空间分布情况,有效应用于中国毛虾限额捕捞,为解决我国单品种限额捕捞难点积累了宝贵经验。  相似文献   

19.
Ｒｅｌａｔｉｏｎｓｈｉｐｂｅｔｗｅｅｎｄｅｅｐ－ｓｅａｆｉｓｈｄｉｓｔｒｉｂｕｔｉｏｎｓａｎｄｏｃｅａｎｉｃｃｏｎｄｉｔｉｏｎｓｏｆｔｈｅＥａｓｔＣｈｉｎａＳｅａ￥ＳｈｅｎＪｉｎ＇ａｏ（ＲｅｃｅｉｖｅｄＮｏｖｅｍｂｅｒ１７，１９９３；ａｃｃｅｐｔｅｄ...  相似文献   

20.
黄海西部渔业资源状况   总被引：1，自引：0，他引：1       下载免费PDF全文
杨纪明 《海洋科学》1988,12(4):70-71
黄海是中国大陆和朝鲜半岛之间的陆架浅海,北起鸭绿江口,南迄长江口北,西北部与渤海相通,南部和东海相连。这个海域位于暖温带,既有暖流的进入,又有沿岸流和冷水团终年存在。这样的环境条件,决定了海洋动物区系和渔业资源中以暖温性鱼类(小黄鱼、真鲷、蓝点鲅、青鳞鱼、皱唇鲨、孔鳐等)为主、同时兼有暖水性(鲐鱼、鳓鱼等)和冷温性(太平洋鲱、鳕鱼  相似文献   

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