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1.
Abstract Immigration of catadromous anguillid eels into fresh water can be impeded by barriers such as barrages, weirs and dams. The uses of passes and trap-and-transport systems to enhance recruitment are reviewed. Pre-construction studies of the needs for passes and traps are discussed in relation to key biological and hydraulic management criteria. Recommendations for pass and trap designs and placement are made in the context of site-specific biotic and abiotic factors. Reference is made to experience gained from eel passes and trapping systems in use throughout the world, and to experimental and pre-and post-construction monitoring studies. Practical recommendations are made for the design and use of eel passes and traps for monitoring studies and for trap-and-transport stocking. 相似文献
2.
1. A classification is described based on an indicator species analysis of the vegetation of 1124 fresh and brackish standing water sites in Great Britain. 2. Ten Site Types are recognizable by their assemblages of plants, and these groupings are related to the alkalinity, pH and conductivity of the water. One Type consists of extremely acid water bodies on peat. There are two other nutrient-poor Types, distinguishable from each other largely by size and substrate, as well as by vegetation. These sites lie mostly in the north and west of Britain. There are four distinct Site Types with nutrient-rich water, one characteristic of Scotland, the rest more typical of the lowlands of southern and eastern Britain. A further Site Type is regarded as mesotrophic and is found mainly in northern England and Scotland. Of the remaining two Site Types, one shows an unusual combination of base-poor and base-rich characteristics and the other comprises brackish sites in Scotland. 3. The use of the classification for producing Trophic Ranking Scores, both for individual species and for sites, and the application of these scores for monitoring the nutrient status of fresh waters are explained. 4. The application of the classification to the selection of sites important for nature conservation is discussed, with special reference to north west Scotland. 5. This classification is compared with other classifications of aquatic vegetation in Great Britain. 相似文献
3.
D. Scott 《水产资源保护:海洋与淡水生态系统》1993,3(1):53-65
- 1. This paper describes New Zealand's Resource Management Act in relation to freshwater management and conservation.
- 2. The development of the Act is described with reference to the consolidation and integration of earlier legislation. The central concept of sustainable management is more limited than the related concept of sustainable development, and places constraints on activities which have environmental impacts.
- 3. The specific provisions relating to fresh water are noted, and the resource consents required for taking water, damming or diverting watercourses, and discharging into water, or onto land where the discharge may reach water, are described. The relation of riparian management to the requirement for protection of fish habitat is noted, and water conservation orders are described. Attention is given to the likely implications for managers.
- 4. An attempt is made to anticipate difficulties that may arise in implementing the Act; in particular, the possible balancing between socio-economic and ecological considerations. The specific features of the freshwater environment are considered from the viewpoint of management, and the problems involved in tradeability are noted. Attention is drawn to the scope of the Act in the attempted integration of most, but not all, environmental considerations, and a final evaluation suggests that economic growth is likely to present a substantial challenge to the purpose of the Act.
4.
Albert G. J. Tacon 《Journal of the World Aquaculture Society》2017,48(3):381-392
For the purposes of this paper, biosecure shrimp feeds and on‐farm feeding strategies refer to the “feed, whether live, fresh, or formulated, and the management of the feed on the farm, should not be an entry point of potential pathogens to the shrimp and/or to the culture system.” The paper reviews the different feeds commonly used for the production of farmed shrimp and discusses their potential risks from a disease perspective, including the use of live hatchery and nursery feeds, the use of live and/or fresh food organisms for the production of broodstock, and the use of dry formulated shrimp feeds for shrimp growout operations. In addition, the paper discusses the critical role played by feed‐processing techniques for the pasteurization and destruction of pathogens within shrimp feeds and the need for nutritionists to formulate feeds for optimal nutrition and health, and not just for optimal growth. The importance of the development and implementation of good on‐farm feed management practices by farmers is discussed, including the prohibition of the top‐dressing of pelleted feeds on farm by farmers with unapproved feed additives such as antibiotics. Finally, the paper discusses the responsibilities of farmers, feed manufacturers, and traders regarding the development and use of recommended biosecure shrimp feeds and feeding practices. 相似文献
5.
漠斑牙鲆仔鱼、稚鱼和幼鱼对低盐度的耐受力和淡水驯化技术的研究 总被引：3，自引：0，他引：3
研究了漠斑牙鲆仔鱼、稚鱼和幼鱼对低盐度的耐受力和漠斑牙鲆的淡水驯化技术。初孵仔鱼在盐度为5的水中最多存活5d,5d以后全部死亡。30日龄稚鱼在4h10min淡水组全部死亡,对淡水的耐受力较低,而盐度为5～25的各组72h的存活率都在95.00%以上。90日龄幼鱼经缓慢淡水驯化9d后存活率可达98%以上,对漠斑牙鲆幼鱼进行淡水驯化的最佳年龄为90日龄。淡水驯化影响幼鱼初期的摄食,以后则逐渐趋于正常;急性淡水驯化对幼鱼的伤害比缓慢淡水驯化大;漠斑牙鲆对低盐的耐受力随生长和发育逐渐增加,年龄是影响幼鱼对低盐度耐受力的主要因素。 相似文献
6.
Juraj Hol&#;ik 《Ecology of Freshwater Fish》1995,4(4):175-179
Abstract– In the anadromous cyprinid kutum, Rutilus frisii (Nordmann, 1840) from the Anzali Lagoon, Iran, the following hitherto unrecorded characters were found. The complex life-style of juvenile kutum is reflected directly in their body size and preferred habitat, and indirectly in their growth rate and the formation of scale annuli. The early juveniles did not move downstream to the feeding grounds in the sea as they are supposed to do in populations inhabiting the Caucasian coast of the Caspian sea, but most of them spend one or two years in fresh or brackish water. Moreover, most kutum scales carried one or two juvenile marks. It appears that the time spent in fresh water is inversely proportional to the age of the kutum. On average about 43% of fish 2 years old and older, spent their first year in fresh or brackish water, while 57% spent two years there. The rate of growth in length is substantially different in both groups. Fish that enter the sea in their second year of life grew faster but their life span seems to be shorter than those which spent two years in fresh or brackish water. 相似文献
7.
Developing co-management in an artisanal gill net fishery of a deep hydro-electric reservoir in Sri Lanka 总被引：1，自引：0，他引：1
Abstract Victoria, is a recently (1984) impounded, deep, hydro-electric reservoir in Sri Lanka with an established commercial fishery. Participatory appraisal of the fishing community revealed decreasing reliance on fishing income with many fishermen moving away to supplementary occupations because of declining fish catches. Illegal fishing and theft of fishing gear resulting from open access, difficulties encountered in enforcing fisheries regulations and the need for fishermen to find alternative sources of income during low water levels are the major management problems. The top–down centralized management approach previously practised was ineffective in addressing any of these issues. Therefore, the possibilities and limitations for introducing co-management as an alternative management strategy were discussed. Financial hardship coupled with perceived benefits through state sponsored welfare schemes caused a positive attitude change among fishermen, making them respond favourably to fishery management. Establishing a licensing system for controlled access, ensuring greater user-group participation through equitable distribution of state sponsored benefits among members, attempting to enforce penalties for illegal fishing linked with surprise checks to enforce management regulations, and obtaining stakeholder perceptions regarding management issues are some of the recent steps taken by the Fishermen's Co-operative Society which would positively contribute towards developing effective co-management in this reservoir. 相似文献
8.
V.A. Tsihrintzis G.K. Sylaios M. Sidiropoulou E.T. Koutrakis 《Aquacultural Engineering》2007,36(3):310-324
Model development is described, related to the restoration efforts of Vassova Lagoon, a small and shallow, fishery exploited coastal lagoon, located in the region of eastern Macedonia, N. Greece. This lagoon has been configured and is used for fisheries, by having dredged through tidal channels and installed fish entrapment devices. Decreases in fish production have been related to poor seawater circulation, limited water renewal and related water quality problems. The aim of this study is to evaluate the current situation of the lagoon and propose alternative management scenarios for improvement of water flow and lagoon ecosystem. The SWMM-EXTRAN mathematical model has been adapted, calibrated, verified, and applied to describe the current situation of the lagoon, and evaluate alternative scenarios for increasing tidal flushing and water residence time. Data necessary for model validation have been collected in the field. Among the tested restoration alternatives were the following: widening and/or deepening the lagoon inlet; constructing a second inlet; widening and/or deepening the tidal channels inside the lagoon. The combined influence of opening the existing communication channel of Vassova Lagoon with the adjacent Eratino Lagoon was also considered for each scenario. The implications of the various scenarios on lagoon's fisheries management are discussed. The alternative of constructing a second tidal inlet channel, 5 m wide, and keeping the Eratino Lagoon channel open provided most tidal flushing and increased internal and inlet flow that favors recruitment of juvenile fish. This alternative was proposed for implementation. 相似文献
9.
Jerom R. Stocks Sam Davis Marti J. Anderson Martin W. Asmus Katherine J.M. Cheshire Dylan E. van der Meulen Chris T. Walsh Dean M. Gilligan 《水产资源保护:海洋与淡水生态系统》2021,31(11):3228-3247
- Fish assemblages in dryland rivers have life-history strategies that have evolved in response to environmental conditions and triggers, particularly water temperatures and flow regimes. The regulation of rivers through the construction of dams, weirs and other water diversion structures has altered natural flow regimes and the associated ecological processes of river systems worldwide.
- Over a 3-year period, using standardized fish sampling and daily otolith ageing, the recruitment of eight freshwater fish species was monitored in response to various abiotic drivers, including hydrology and water temperatures, throughout the Macquarie River, a large regulated river system of the Australian Murray-Darling Basin.
- A data-driven statistical classification system is provided that groups species into reproductive guilds, based on their recruitment response to hydrology and water temperature, specifically designed for use in environmental flow management.
- The eight species were grouped into three distinct reproductive guilds that showed similar recruitment responses to the abiotic drivers. Murray-Darling rainbowfish, Murray cod, and eel-tailed catfish were considered as a single guild, characterized by seasonal recruitment during a relatively narrow thermal window under low to moderate stable discharges. The second group included common carp, bony herring, and golden perch, which recruited primarily in association with larger flow events. Un-specked hardyhead and Australian smelt formed a more differentiated guild, recruiting over a broad range of temperatures and discharges. Limitations associated with using a reproductive guild approach to simplify water management are discussed.
- This study highlighted important relationships among hydrology, water temperatures, and successful recruitment that can, in turn, be used to inform development of adaptive flow management plans and effective use of environmental water for the conservation management of native fish communities. Important considerations in the design of studies that aim to examine relationships between recruitment and abiotic drivers are also discussed.
10.
Conservation of freshwater fish in the British Isles: the status of fish in national nature reserves
1. To consider fully the conservation management of freshwater fish, it was important to know which fish were already in the protected environment of National Nature Reserves (NNRs) — the principal sites for nature conservation in Great Britain. For this reason, 235 NNRs declared by the Nature Conservancy Council (NCC) were surveyed for freshwater fish between 1987 and 1990 by questionnaires to the wardens, by compiling data from other sources, and, where necessary, by field sampling. The presence of fresh waters (as lakes, ponds, rivers and streams) was also recorded. The survey was organized to follow the country and regional structure by which nature conservation was administered by the NCC so that the results could be considered accordingly. 2. Seventy five percent of NNRs contain fresh waters and, of these, just over 20% have no fish. Of the 51 fish species available 37 (73%) were recorded in NNRs. NCC regions with most fish species are: SW Scotland, West Midlands and East Anglia, but NW Scotland has the highest total of species occurrences in NNRs. In terms of both the numbers of species and their frequency of occurrence, NW and NE England are notably the lowest. The most common fish in NNRs are Eels, Brown Trout and Three-spined Sticklebacks. 3. The results for species and for sites (NNRs) are discussed from the viewpoint of fish conservation. The majority of fish in NNRs are those most common in Great Britain. Two of the species recorded (Powan and Smelt) are currently important for conservation, but several of those most threatened do not occur in NNRs. A number of NNRs have diverse fish communities, but only six have significant fish conservation value, of which Loch Lomond NNR is outstanding. 4. There is considerable scope through NNR management to improve fish conservation and it is suggested that the acquisition of new reserves for threatened species should be considered. 相似文献
11.
On amphidromy, a distinct form of diadromy in aquatic organisms 总被引：3，自引：0，他引：3
R M McDowall 《Fish and Fisheries》2007,8(1):1-13
Amphidromy is a distinctive form of diadromy that involves some fish, decapod crustaceans and gastropod molluscs. Characteristic elements in amphidromy are: reproduction in fresh water, passage to sea by newly hatched larvae, a period of feeding and growing at sea usually a few months long, return to fresh water of well‐grown juveniles, a further period of feeding and growing in fresh water, followed by reproduction there. This life‐history strategy is observed in numerous fish species, primarily in islands of the tropics and subtropics (probably more than 75 species, especially sicydiine gobies), and extends to temperate countries as far as Japan in the north and New Zealand in the south. There has been considerable confusion about the nature of amphidromy and its distinctiveness from anadromy, another category of diadromy. The return to freshwater of small juveniles of amphidromous fishes is functionally and strategically different from the return of large mature adults, as happens in anadromy. The strategy is recognized as distinctive by numerous fish biologists who work with amphidromous fishes, although it has tended to be rejected or ignored by others, typically those who have no personal experience with them. 相似文献
12.
Effects of modified pond management on limnological parameters in small‐scale aquaculture ponds in mountainous Northern Vietnam 
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下载免费PDF全文 Johannes Pucher Richard Mayrhofer Mansour El‐Matbouli Ulfert Focken 《Aquaculture Research》2016,47(1):56-70
In mountainous Northern Vietnam, traditional pond aquaculture is part of the integrated farming activity contributing to food safety and to income generation for small‐scale farmers of ethnic minorities. Traditional pond management consists of a polyculture of macro‐herbivorous grass carp with 3–5 other fish species that are cultured in small ponds with constant water flow through. The main limitations to production are species‐specific mass mortalities of grass carp, a poor feed base especially for all species but grass carp, and poor water quality. In this study, we compared the traditional pond management to a semi‐intensive pond management that was based on the traditional management system but included changes designed by researchers to increase fish production. The modifications consisted of water inflow control, supplemental fertilization and feeding, and a polyculture dominated by common carp. The changes in management significantly reduced the turbidity and increased oxygen supply, as well as the natural food base within the pond. These changes in pond management provide farmers with the possibility to improve their pond aquaculture scheme and overcome previous limitations. 相似文献
13.
Somatolactin (SL) is a novel pituitary hormone recently characterized in several fish species. Structural analyses have shown that SL belongs to the growth hormone/prolactin family, and that it is a highly conserved protein. SL is synthesized by the periodic acid/Schiff-positive cells in the pars intermedia, but has an as yet unidentified function(s). We have recently developed a homologous radioimmunoassay for coho salmon SL and measured plasma levels of SL during two stages of the coho salmon life cycle, smoltification and sexual maturation. During smoltification, plasma levels of SL changed almost in parallel with plasma levels of thyroxine; levels increased as morphological indices of smoltification appeared and decreased as smoltification was completed. Following this period, SL levels remained low until the spring prior to spawning. In a separate study, plasma levels of SL were measured in sexually maturing coho salmon that remained in fresh water throughout their life cycle. During the year of sexual maturation, plasma levels of SL gradually increased from the spring onward, reaching peak levels at the time of spawning in November and December. These data are similar to those previously reported for sexually maturing coho salmon that were maintained in seawater prior to spawning (Rand-Weaver et al. 1992). Therefore, increases in plasma SL levels occurred in sexually maturing fish irrespective of whether they were maintained in fresh water or seawater. Peak levels at spawning were higher than those observed during smoltification. Possible roles for SL in metabolism and reproduction are discussed. 相似文献
14.
Three cryoprotectants (dimethyl sulphoxide, propylene glycol and glycerol) and two diluents (sucrose based and saline based) were mixed (9 parts diluent–1 part cryoprotectant) factorially to produce six extenders that were tested to develop an effective sperm cryopreservation protocol for winter flounder Pseudopleuronectes americanus (Walbaum). Sperm were diluted 1:3 with each extender and frozen by flotation on liquid nitrogen before being submerged and stored for 30 days. Sperm left unfrozen in each extender for 20 min showed no toxic effects on motility. Extenders containing propylene glycol (PG) as cryoprotectant yielded higher post‐thaw sperm motilities than those containing dimethyl sulphoxide (DMSO) or glycerol. The sucrose‐based diluent performed better than the saline‐based diluent when DMSO was used as cryoprotectant, but there were no differences in post‐thaw motility between diluents for the other cryoprotectants. Activating sperm with ovarian fluid and sea water instead of sea water alone had no effect on post‐thaw motility. In fertilization trials, no differences were observed between any of the extenders and fresh milt when milt, eggs and sea water were left in contact for 1 h. When sperm were forced to compete for eggs by reducing contact time to 20 s, fertilization results followed those of sperm motility rates. Percentage hatch and morphology of larvae at hatching did not differ for eggs fertilized by cryopreserved and fresh sperm. This study represents the first reported successful attempt at cryopreserving winter flounder sperm and should improve gamete and broodstock management protocols for this species. 相似文献
15.
A Fontaínhas-Fernandes M Monteiro E Gomes M A Reis-Henriques & J Coimbra 《Aquaculture Research》2000,31(6):507-517
This trial was conducted in order to test the effect of supplemental dietary sodium chloride on growth and plasma thyroid hormone levels of male and female monosex groups of tilapia Oreochromis niloticus (L.) reared in fresh water and 10‰ brackish water. At the end of the experiment. the gonadal development of females was observed. A high‐salt diet (8% NaCl) was fed to female and male tilapia for a period of 3 weeks. After this time. both groups were transferred directly to fresh water and 10‰ brackish water, and a growth trial was conducted over 90 days. The results indicate that dietary supplementation with NaCl improved the growth of females and males at 30 days, except for females maintained in fresh water. Females reared in 10‰ brackish water showed an increase in growth rates that was accompanied by the highest plasma T3 levels. In contrast, males did not exhibit the same relationship in 10‰ brackish water, showing lower plasma T3 levels than in fresh water. Histological sections of O. niloticus ovaries revealed that female groups contained oocytes at different stages of development. At 90 days, females reared in 10‰ brackish water showed oocytes in maturation, while in fresh water, they showed the highest proportion of vitellogenic oocytes and no mature oocytes. The highest proportion of mature oocytes observed in brackish water was associated with the better growth rate in relation to fresh water. These results confirm that tilapia breed freely in low‐salinity brackish water as well as in fresh water. 相似文献
16.
Osmoregulatory ability of anadromous Arctic char, Salvelinus alpinus (L.), migrating towards the sea
Abstract. Hypoosmoregulatory capacity was examined in anadromous Arctic char, Salvelinus alpinus (L.), caught whilst migrating towards the sea in the river Å-elva, northern Norway (69°04′N and 17°00′E). Metacercariae of the marine digenean Cryptocotyle lingua (Creplin) were found on 47% of the fish investigated, demonstrating that they had been in brackish or sea water on at least one previous occasion. The fish were randomly divided into three groups, and exposed to sea water (35 ppt salinity at 5–6°C) for 7 days- one group immediately after capture, and the other two groups after 16 days of acclimation in fresh water and brackish water (15–17ppt), respectively. Blood plasma osmolality, Na+ and Mg2+ levels showed only a small and transient rise during seawater exposure, and there were only minor changes in muscle water content, irrespective of prior treatment. A slight, but insignificant, reduction in hypoosmoregulatory capacity appeared to occur in the groups retained in fresh water or brackish water for 16 days prior to seawater exposure. The results did not indicate that the fish show any improvement of hypoosmoregulatory capacity following a period of acclimation in brackish water. The hypoosmoregulatory capacity of seaward-migrating Arctic char is well developed before they enter the sea, and may be comparable to that seen in salmonids which undergo a parr-smolt transformation. There was a negative correlation between blood plasma electrolyte levels and both body length and weight, indicating that hypoosmoregulatory capacity was affected by the size of the fish. The effects of body size upon the development of hypoosmoregulatory capacity are discussed with respect to estuarine residence and the constraints placed upon the survival of small fish in full-strength sea water. 相似文献
17.
18.
《联合国海洋法公约》生效对公海渔业的影响 总被引：1，自引：0，他引：1
在归纳世界大多数沿海国家执行联合国海洋法公约，主要实施公海制度的实践，以及分析公约有关条款的基础上，指出今后渔业管理制度将朝着有利于沿海国的方向发展，远洋渔业国只有与沿海国密切合作，承担公约所规定的养护生物资源的义务，才能确保远洋渔业生产的持续稳定发展。根据我国渔业的实际状况，分析了海洋法公约生效对我国公海渔业生产产生的一些不利影响，并提出对海洋渔业发展的一些看法 相似文献
19.
Vibrio vulnificus biotype 2 is subdivided into two main serovars, serovar E, able to infect fish and humans, and serovar A, only virulent for fish. Serovar E emerged in 1976 as the causative agent of a haemorrhagic septicaemia (warm‐water vibriosis) affecting eels cultured in brackish water. Serovar A emerged in 2000 in freshwater‐cultured eels vaccinated against serovar E, causing warm‐water vibriosis with fish showing a haemorrhagic intestine as the main differential sign. The aim of the present work was to compare the disease caused by both serovars in terms of transmission routes, portals of entry and host range. Results of bath, patch‐contact and oral‐anal challenges demonstrated that both serovars spread through water and infect healthy eels, serovar A entering mainly by the anus and serovar E by the gills. The course of the disease under laboratory conditions was similar for both serovars in terms of transmission and dependence of degree of virulence on water parameters (temperature and salinity). However, the decrease in degree of virulence in fresh water was significantly greater in serovar E than in serovar A. Finally, both serovars proved pathogenic for tilapia, sea bass and rainbow trout, but not for sea bream, with significant differences in degree of virulence only in rainbow trout. In conclusion, serovar A seems to represent a new antigenic form of V. vulnificus biotype 2 with an unusual portal of entry and is better adapted to fresh water than serovar E. 相似文献
20.
Do Eurasian minnows (Phoxinus phoxinus L.) inhabiting brackish water enter fresh water to reproduce: Evidence from a study on otolith microchemistry 下载免费PDF全文
下载免费PDF全文 Roland Svirgsden Mehis Rohtla Anu Albert Imre Taal Lauri Saks Aare Verliin Markus Vetemaa 《Ecology of Freshwater Fish》2018,27(1):89-97
Dynamics of coastal fish assemblages in the Baltic Sea are still rather poorly understood. In particular, little information is available on migrations and movements of the small‐bodied littoral fish species like Eurasian minnow (Phoxinus phoxinus L.). Minnow is considered typically as a river and lake species, but it also inhabits brackish coastal waters of the Baltic Sea. In this study, we investigated movement patterns of brackish water inhabiting minnows using otolith microchemistry. Fish were collected from four different sites (from two bays and two stream mouths) around Saaremaa Island. The results indicated that at least three distinct migration patterns exist: (i) seawater residency, (ii) fast springtime migrations to fresh water or to bays with lower salinities (areas near stream mouths) and (iii) prolonged migrations to fresh water (some cases overwintering in streams). Migration patterns listed above were not evenly distributed among sites, and some individuals did not migrate to fresh water in every year. None of the analysed fish were freshwater residents. Additionally, potentially ontogenetic effects on Mn and Sr concentrations were observed in the otolith core regions, which may have important implications for the interpretation of otolith chemistry data. The overall findings of this study demonstrate that much more complex migration patterns exists in brackish water inhabiting minnow populations than previously thought and at least some individuals do enter freshwater to reproduce. 相似文献