摘要:

The first annual check appears on the scales of Thames dace as the fish begin their third year of life. Counting of annuli does not give the true age of the fish. Data from 4 other habitats are re‐examined and on one occasion it is evident that ageing has been incorrec

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1972.tb05685.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

An autumn planting of 4000 tagged yearling brown troutSalmo trutta(L.) in 1969 resulted in an over‐winter survival of 26%, an angler recovery the following year of 8·1 % and made up 22 % of the March, 1970 standing population of the species. August standing populations of brown trout increased from 142 trout/ha (17·6 kg/ha) in 1969 to 360 trout/ha (39·3 kg/ha in 1970 while angler harvest of the species increased from 61 trout/ha (12·7 kg/ha) at a rate of 0·26 fish/h to 89 trout/ha (18·5 kg/ha) at a rate of 0·34/h. Using angler recovery and standing population as criteria the planting contributed substantially to the fishery. Actual contribution of stocked trout however, is questioned after detailed analysis of resident population structure and the potential of natural recruitment. It is suggested that the true benefit of stocked trout may be measured by the presence of those stocked fish in excess of the number of resident trout of that size predictable from a normal length distribution curve in waters with self‐sustaining populations. Complexities in evaluating the merits of supplemental plantings of hatchery‐reared brown trout to existing stream fisheries

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1972.tb05686.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The littoral fauna of Llyn Tegid, North Wales, in 1968/9 is compared with the results of similar faunal investigations made by Rothwell(née Dunn) in 1951/2 (Dunn, 1953) and Hynes in 1957 and 1959 (Hynes, 1961). The results show the long term effects upon the littoral fauna of the change in mean water level and the increased water level fluctuations produced for a time by the controlled outflow scheme, which came into operation in 1955. In 1961 Hynes recorded big reductions in numbers and variety of invertebrates living in the littoral zone. The reduced water level fluctuations in recent years has resulted in a re‐establishment of some of the fau

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1972.tb05687.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

An account is given of the survival and contribution to sport fishing of stocked trout and natural river trout in the impounded reservoir, Llyn Alaw, in Anglesey, North Wales. Scales from 2143 trout caught by angling and netting during the first four years after impoundment were used to determine the age and origin of Llyn Alaw fish. The success and future of Llyn Alaw as a trout fishery are discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1972.tb05688.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The annual and seasonal growth, length/weight relationship, changes in seasonal condition and specific growth rates of 17 types of trout in the newly flooded reservoir, Llyn Alaw, in Anglesey, North Wales, were investigated. Scales and length‐weight data from 2076 trout caught by angling and netting during the first 4 years after impoundment were analysed to show the age, origins and growth of all fish both before and after floodin

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1972.tb05689.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

Data on some aspects of the biology of gudgeon were obtained during a programme of research on Irish coarse fishes. Eggs of gudgeon, were collected on 3 occasions—on June 8 and again on June 29, 1965 in a small rivulet entering a hydro‐electric reservoir in Co. Cork; and on June 2, 1966 in a millstream on the Grand Canal in Co. Dublin. The eggs were greyish‐white in colour, opaque, and 1·375–1·625 mm diam. Newly‐hatched larvae from eggs from Co. Cork measured 5·45 mm and were distinguished by the presence of black pigment largely confined to the ventral aspect of the yolk sac and tail. They began to feed after 3 days; in 5–6 days the yolk was fully absorbed, the fish then measuring 6·2 mm. Following the creation of 2 hydro‐electric reservoirs on the River Lee in Co. Cork, large populations of gudgeon developed in them for a time. It was found that, in the reservoirs, gudgeon less than 7·5 cm were feeding mainly on Cladocera, especially Chydoridae. The larger reservoir gudgeon and gudgeon in rivers and streams in Co. Cork fed mainly on molluscs,Gammarus, chironomid larvae, caddis larvae and ephemeropteran nymphs. Some gudgeon held a good deal of filamentous algae. Gudgeon were aged by means of scale reading, the results of which were confirmed by length‐frequency distribution analysis in the case of the reservoirs. In the Lee system, gudgeon grew relatively rapidly at first, attaining a mean fork‐length at 3 years old of 9·5–10·8 cm according to year‐class. In the River Allow, a Cork Blackwater tributary, early growth was slower than in the Lee, but the length increments in the third and subsequent seasons were bigger than in the Lee reservoirs. In the Lee, most gudgeon of both sexes spawned for the first time when 2 years old, at a minimum fork‐length of 6·9 cm in the case of males and 7·9 cm in the case of females. The trematode parasiteParacoenogonimus ovatuswas of frequent occurrence in Irish

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1972.tb05690.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

The pathology and bacteriology of an aeromonad epidemic in the spawning population of brown trout (Salmo truttaL.) of the freshwater Loch Leven, Kinross, Scotland, is described, together with estimates of its quantitative effect on the stock of trout.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1972.tb05691.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1972.tb05692.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

CURRENT TOPICS IN COMPARATIVE PATHOBIOLOGYOCEANOGRAPHY‐AN INTRODUCTION TO THE MARINE ENVIRONMENT. Peter K. Weyl.REGIONAL VARIATION IN INDIAN OCEAN CORAL REEFS. Edited by D. R. Stoddart and Sir Maurice Yonge.BRITISH PROSOBRANCH AND OTHER OPERCULATE GASTROPOD MOLLUSCS: KEYS AND NOTES FOR THE IDENTIFICATION OF THE SPECIES (shortened to ‘BRITISH PROSO‐BRANCHS’ on the cover), by Alistair Graham. Linnean Society Synopsis of the British Fauna (New Series) number two.CHECK LIST OF THE HELMINTH PARASITES OF AFRICAN FRESHWATER FISHES by L. F. Khalil. Technical CommunicationBIOLOGY AND WATER POLLUTION CONTROL by Charles E. Warren. Philadelphia, London, Toronto: W. B. S

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1972.tb05693.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1972.tb05694.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY