摘要:

Abstract The fish fauna and habitat characteristics in five reaches of a small lowland stream were studied through the summer and winter of one year. All species densities, except Atlantic salmon,Salmo salarL., were correlated with either instream or outstream cover, reaffirming the importance of cover to maintain the local abundance of fish populations. There were significant differences between reaches in the density of all the fish species studied, with the exception of the larger size group of dace.Leuciscus leuciscus(L.), and between sampling times for salmon, dace and eel,Anguilla anguilla(L.). There were significant differences between reaches for all the measured habitat variables apart from instream cover, and between sampling times for velocity. instream cover, and substrate particle size, but not depth, width:depth ratio and outstream cover. The implications of these variations for fish stock assessment and predictive fish habitat models such as PHABSIM and habitat suitability indices are discusse

ISSN:0969-997X    

DOI:10.1111/j.1365-2400.1994.tb00157.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract Controlled temperature variation was used to induce marks on scales of silver perch,Bidyanus bidyanus(Mitchell), for stock identification. Genetically similar fish were held in tanks at three temperatures for a period of 4 weeks. Circulus spacing information was acquired using automated video digitizing equipment. Discriminant function analysis was used to classify fish into their respective rearing temperatures. Fish held at 30°C were classified with high accuracy (94–96%). Classification inaccuracies increased in fish held at the lower temperatures. Fish growth at each temperature was examined and classification accuracies were a reflection of growth differences. The use of temperature variables to induce marks on scales offers scope for batch‐marking pre‐stoc

ISSN:0969-997X    

DOI:10.1111/j.1365-2400.1994.tb00158.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract Water quality in tropical fish ponds is generally evaluated without the assistance of remote sensing because of cost, cloud cover, and other constraints, but certain parameters such as suspended solid concentrations, colour, chlorophyll and temperature can effectively be monitored by aerial photography and satellite imagery. This paper reviews applications of remote sensing to tropical inland fisheries and aquaculture and includes applications from related disciplines. A brief assessment of new platforms and sensors is also presented. Remote sensing images may help to inform researchers and planners about water quality trends that are occurring over a broad area in which fisheries and aquaculture activities occur. However, the operational use of remote sensing in aquaculture remains largely experimenta

ISSN:0969-997X    

DOI:10.1111/j.1365-2400.1994.tb00159.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract Following a sea trout stock collapse in 1989 and 1990, wild sea trout kelts were successfully reconditioned in brackish water using semi‐moist pellets and a commercial broodstock diet. The on‐growing of wild sea trout smolts was not so successful. Natural mortality was 12.9%, and 36.1% of the fish failed to adapt to the artificial diets: 82% of these were smolts. Instantaneous growth was highest from June to August (0.74%), with an overall rate for April to September of 0.51%. At the end of the first year. 36 females and 26 males matured; 34 females, with a mean fork length of 33.2 cm, were stripped yielding 22860 ova at a mean rate of 682 ova per female or 1586 ova kg‐1body weight. The survival of green ova to eyed ova was 90–98%, and survival from green ova to hatched alevi

ISSN:0969-997X    

DOI:10.1111/j.1365-2400.1994.tb00160.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract Substantial alterations to the legal controls over fish movements have been necessary to implement the Single European Market which came into force on 1 January 1993. This seeks to liberalize trade in fish and fish products whilst avoiding ecological damage, the spread of disease and the commercial damage this may cause. The new regime governing fish movements into and within the European Union under Directive 91/67/EEC, as implemented in England and Wales, is described. Remaining national provisions based on ecological concerns (principally, section 30 of the Salmon and Freshwater Fisheries Act 1975) are examined. Derogations from the principle of freedom of trade within the European Union on environmental protection grounds are assessed, and the interaction between legal restrictions based on pathological and ecological grounds is discusse

ISSN:0969-997X    

DOI:10.1111/j.1365-2400.1994.tb00161.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Abstract Isomeric ratios of astaxanthin in eggs and alevins of Atlantic salmon,Salmo salarL., have proven useful in identifying female spawners of farmed origin, but the method underestimates the proportion of fish of farmed origin. The rate of underestimation was studied by analysing astaxanthin content in tissue of 55 farmed Atlantic salmon ascending two Norwegian rivers in the autumn of 1991. The astaxanthin content fell into two distinct classes. Fifty‐one per cent of the adult escaped salmon had isomeric ratios similar to salmon fed synthetic astaxanthin, whereas all the remaining fish had ratios similar to wild fish. Discriminant analysis classified 96.4% of the fish with known astaxanthin content into the correct astaxanthin class on basis of tail‐fin erosion, length, weight and gill‐cover damage. This discriminant function was used to estimate the astaxanthin classification of 1017 farmed salmon caught in nine rivers during 1989–1991. The classification success varied among years from 52 to 64%. Corresponding numbers for females and males were 45–48% and 54–70%, respectively. Thus, estimates of spawning rates of farmed female salmon via astaxanthin content in eggs or alevins from redds should be adjusted accordingly. The observed isomeric ratios of astaxanthin in the escaped farmed salmon and the relationship with morphology indicates that a significant proportion of the escapees ascending rivers have spent more than 1 year in the wild

ISSN:0969-997X    

DOI:10.1111/j.1365-2400.1994.tb00162.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Book reviewed in this article:Living Waters – How to Save Your Local Stream.By Owen D. Owe

ISSN:0969-997X    

DOI:10.1111/j.1365-2400.1994.tb00163.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0969-997X    

DOI:10.1111/j.1365-2400.1994.tb00164.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:0969-997X    

DOI:10.1111/j.1365-2400.1994.tb00165.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY