摘要:

Abstract.LarvalMacrobrachium nipponense(de Haan) were subjected to a range of salinity between 0 and 15‰. The maximum survival and metamorphosis rate to post‐larvae was between 7·5 and 12·5‰, although some survival was observed even in fresh water. The implications of these findings in relation to aquaculture and the evolutionary process of this genus is briefly di

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1987.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.Three feeding trials, involving pre‐pupal larvae of soldier fly,Hermetia illucens L., grown on poultry manure, were conducted to assess: (1) channel catfish,Ictalurus punctatus(Rafinesque), response to substitution of dried meal larvae for the fish meal component of the catfish diet and (2) if feeding 100% whole or chopped larvae to channel catfish or blue tilapia,Oreochromis aureus(Steindachner), will support normal growth comparable to those fed a commercial diet. Effects on fish quality were also evaluated. Replacement of 10% fish meal with 10% soldier fly larvae resulted in slower growth over a 15‐week period for subadult channel catfish grown in cages (trial 1). However, the replacement did not reduce growth rate significantly when channel catfish were grown in culture tanks at a slower growth rate (trial 2). Feeding 100% larvae did not provide sufficient dry matter or protein intake for good growth for either species grown in tanks (trials 2 and 3). Chopping of the larvae improved weight gain and efficiency of the utilizat

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1987.tb00141.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.Four feed trials were carried out to assess whether a vitamin premix was required in feeds for the intensive tilapia farm of the Zambia Sugar Company. Although inclusion of a vitamin premix did not result in improved fish growth rates or food conversions, in one of the trials a significantly higher degree of haemorrhaging was noted in the fish fed a feed without the premix. The results suggested that vitamin A was likely to be the most deficient vitamin in the feeds, but this can be readily supplied by lucerne. The conclusion was that it was not economically justifiable to include an imported vitamin premix in the feeds. Information is urgently required on how the vitamin requirements of different species and sizes of tilapias vary in practical diet formulations.

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1987.tb00142.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.The fish fauna of the Sepik River system, Papua New Guinea is described. The fish species diversity in this large river is low, even by comparison to other overs in the south of the island. There are particular biological constraints to increasing the yield of the fishery based on native fish stocks. The yield of the Sepik River fishery is low by comparison to rivers in other zoogeographie regions. People in the Sepik also suffer from protein malnourishment. The introduction of appropriate fish species would significantly improve the stocks upon which the fishery is based. The economic cost of stocking is not an issue. Yield estimates suggest that the long‐term benefits of improved stocks could be considerable. The indigenous freshwater fish fauna is unique and arguments against stocking relate to the conservation of that fauna and the existing fisheries. Alternatives to stocking are discussed. If stocking does not occur then a permanently disadvantaged fishery must be accepted. Decisions rest with the government and will be based on further research and consideration. Considerations must relate to the particular inland fisheries development problems in the country. The approach being taken is to appraise fish introductions properly before they occur. A cautious approach is recommended and suggestions about particular species that might be suitable for introduction are premature at presen

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1987.tb00143.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.The stomach contents of 256 Atlantic salmon,Salmo salarL., of fork lengths 53–66cm, caught in bag nets on the Scottish west coast near Ullapool, were examined between June 1983 and July 1986. A total of 61 fish contained fish in the stomach or had faecal pellets containing fish bones in the gut. All recognizable whole fish were sandeels,Ammodytes marinusRaitt, ranging in size from 4.5 to 15cm. No evidence for crustacean or other non‐fish prey items was found. Results indicate that feeding salmon were caught up to a certain cut‐off point in June or early July, after which all salmon sampled were not feeding. It is suggested that either there is a local feeding stock of salmon or that fish feed during migration from the Faroe Isles or other possible distant water or

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1987.tb00144.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.Overexploitation and pollution has led to the decline of Scotland's traditional smelt fisheries. The one remaining commercial fishery is on the River Cree in south‐west Scotland and the characteristics of the spawning runs of the smelt,Osmerus eperlanus(L.), on which this fishery is based have been studied with a view to conservation and re‐establishment of the species elsewhere in Scotland.The spawning‐runs which started in early March when water temperatures were greater than 5°C were characterized by marked temporal changes in size, age and sex ratio. The fish enter the spawning stock at 1+ years of age and, in common with other estuarine smelt populations, are highly fecund. The spawning stock was composed mainly of two age‐classes (1+ and 2+ years) and fish of the 1978 year‐class dominated the spawning stock in 1980 and 1981. Spawning, which was interrupted during periods of high flow, lasted about 1 week. Male fish tended to remain on the spawning grounds after females had vacated the area. Recommendations for management and re‐establishing smelt stocks a

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1987.tb00145.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.A sharp rise in the concentration of soluble reactive phosphorus antl a marked decrease in the level of nitrate were associated with intermittent thermal stratification and localized de‐oxygenation in Coldingham Loch (Berwickshire, Scotland) in summer. These conditions apparently favoured plunktonic blue‐green ‘algae’ (Cyanobacteria) such asAphani‐zomenon, which grew to bloom proportions and threatened the trout angling fishery for which the loch is managed. Various measures for ameliorating the situation are discussed and two bubble‐gun units were installed in the deepest part of the loch (ca12m), to distribute compressed air and mix the column. The installation was operated continuously during the periods May‐September of 1984 and 1985. Temperature and chlorophyll measurements indicated good vertical and horizontal mixing.In spite of virtually no effect on rates of release of phosphorus from the sediments, mixing prevented surface bloom formations ofAphanizomenonand reduced its biomass; maxima of 17 and 52m filament 1−1in 1984 and 1985 respectively contrast markedly with peaks of 130 and 630m 1−1recorded in 1983. Total phytoplankton abundance was also lower. In 1984, the main difference occurred at the ‘critical’ late‐summer period with chlorophyll concentrations ofca20 μg 1−1being only one‐half of those measured at the same time in 1983, and Secchi disc transparencies ofca3·0 m compared to values of ≤ l·5min 1983. An even greater response was recorded in 1985; throughout May to September, chlorophyll levels rarely exceeded 13μg 1−1while water

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1987.tb00146.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.Conventional methods of scale characterization commonly used lo discriminate between stocks of Atlantic salmon,Salmo salarL., though shown to be effective in continental distinction present obvious disadvantages and limitations. Therefore, a more powerful analytical technique is required, especially in the identification of regional or specific stocks. The objective of this work has been to test the potential usefulness of scale‐shape analysis for stock identification purposes. Numerical analysis of scale morphology has been performed on 690 scales of adult Atlantic salmon originating from eight European and North American stocks. The shape features examined (shape factors, moment invariants and elliptic Fourier descriptors) have been found to provide useful information since they resulted in high levels of discrimination in pairs, except for the two stocks originating from Iceland. The appropriateness of those measurements for stock identification purposes and the necessity of a previous sampling and statistical treatment strategy are discusse

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1987.tb00147.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract.An assessment of the angling performance of a small put‐and‐take/or release fishery slocked with rainbow trout,Salmo gairdneriRichardson, at a density in the range 345–565 fish/hectare (140–230/acre) showed that the correlations of mean daily and weekly catch per unit effort with population of fish were low and of uncertain significance at the 5% level.A pilot comparison with other fisheries indicates that the annual mean catch per full day and the annual mean population density may be related by the equationCatch/full day = 0·74 Fish/hectare0·33The roles of catch per unit effort and frequency distributions in the estimation of fish abundance are

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1987.tb00148.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY