ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1982.tb00042.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTAttempts to relate the impacts of an experimental weed‐cutting programme, involving the partial and total clearance of aquatic and bankside vegetation, to the abundance of fish stocks in a small lowland river were made difficult by large inherent fluctuations in population levels within the fish community. However, mapping studies showed fish distribution in uncut and partially cut sections to be strongly associated with weed cover, particularly that provided by overhanging backside vegetation. It is suggested that a partial‐cut strategy, in which marginal weed beds and bankside vegetation are left undisturbed, is more beneficial to fisheries than traditional programmes of weed clearance. Increased fish movements during the operation of a weed‐cutting launch suggest that this form of control may result in more disturbance to the fish community than does manual weed control. Weed‐cutting and other weed management practices are discussed in relation to fisheries ecology and conse

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1982.tb00043.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTInvestigations were carried out in 1979 and 1980 into the location of spawning grounds of perch in Loch Leven, the comparative intensity of their use and the duration of the spawning period. Spawning was found to take place in depths of 1–5 m and there was an indication that depths around 3 m are preferred. Silt and mud apparently inhibit spawning on exposed shores down to 2.5 m although natural shelter probably ameliorates this. Macrophytic vegetation is rarely present at the preferred depths, therefore, artefacts and artificial substrates must be most frequently used.Spawning started about 25 April in a ‘mild’ spring and about 9 May in a ‘cold’ spring. The duration of the spawning period was 4–5 weeks.A double peak in spawning intensity was found in 1979 and, if valid, could indicate a division of spawning fish into two groups, possibly by age as the peaks were not associated with the location of spawning sites. Although spawning tended to be more intense on the southern shore and around one of the islands almost any part of the loch down to 5 m

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1982.tb00044.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTA description is given of an alternating current electric fishing unit designed for use from a boat. Safe control of power to the electrodes is achieved by the operators standing on compressible rubber bulbs linked by plastic tubing to air‐operated mains switches in a control bo

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1982.tb00045.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTThe importance of obtaining reliable estimates of the sea age composition of reported salmon catches are discussed. The use of length frequency distributions to determine the sea age of salmon in samples taken from the North Esk commercial catch are described. The results obtained using this technique are compared to those obtained from scale reading on a 4 weekly basis over a 16‐year period. The use of length frequencies is shown to provide a reliable estimate of the sea age composition of catch samples. The adoption of this technique in catch sampling programmes is labour saving and facilitates rapid samplin

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1982.tb00046.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1982.tb00047.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Book reviewed in this articleResource Management and Environmental Uncertainty: Lessons from Coastal Upwelling Fisheries Edited by M. H. GLANTZ and J. D. THOMPSON.Marine Fish Larvae: Morphology, Ecology and Relation to Fisheries. Edited by REUBEN LASKER

ISSN:1355-557X    

DOI:10.1111/j.1365-2109.1982.tb00048.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY