摘要:

This paper is based on the investigation of 173 lochs in Scotland from which a total of over 4700 brown trout were examined. Twenty‐four of the lochs, all in northern Scotland, and their trout populations, were selected for detailed comparison in an attempt to identify environmental factors that might affect the growth rate of trout. The lochs probably represented the full range of main standing water habitats in the region‐ranging from a saline loch in the Outer Hebrides to one in a sub‐arctic environment high on the Cairngorm plateau in the Central Highlands. The study indicates that for practical purposes the growth rate of trout is negatively correlated with population density. Some suggestions for improving brown trout lochs, based on the findings of this paper, are inc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb05902.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

A volumetric method in which the stomach contents are squashed to a uniform depth and the volume is derived from the area of the squash has been evaluated. The apparatus is simple in constiuction and the method applicable to a wide range of fish sizes. The overall error of the method may be as low as 3.5 % for well macerated material, though for hard bodied food animals the coefficient of variation may be up to 8 %. These volumetric determinations are not directly proportional to gravimetric measurements but logarithmic conversion curves are readily derived.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb05903.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

This study is concerned with the age and growth of perch (Perca fluviatilis L.) in two contrasting Scottish lochs‐the Dubh Lochan and Loch Lomond. Age and back‐calculated growth were determined from annual rings in the opercular bones, and during the 2‐year project 470 perch from the Dubh Lochan and 796 from Loch Lomond were examined. Growth in length in the two lochs, though similar for the first 2 years, differed thereafter, the average length at 8 years in the Dubh Lochan being less than 15 cm, that in Loch Lomond more than 23 cm at the same age. In neither locality did the growth of perch follow the Von Bertalanffy growth formula. Reasons for differential growth rates are discussed and comparisons made with the growth of perch in other waters in Europe and North Am

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb05904.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The systematic history of the Mediterranean centracanthid fishes is reviewed and the past and present nomenclatural confusion in this group, most of which appears to have been due to the occurrence of colour polymorphism coupled with sex inversion, is discussed. The question of the probable systematic status of Spicara chryselis is raised, and in particular whether it should be regarded as a separate species or merely a colour form of one of the other two Mediterranean species (S. smaris and S. maena) belonging to this genus. The results of both electrophoretic studies of their eye‐lens proteins and morphological studies of these three forms are discussed, and the conclusion is drawn that S. chryselis is but a chromatic ecophenotype of the polymorphic species S. maena. The occurrence of such habitat‐associated colour polymorphism coupled with sex inversion is compared with a similar phenomenon previously observed in the labrid Corisjulis. The potential value of electrophoretic studies of eye lens proteins in the solution of such complicated intra‐ and inter‐specific systematic problems is emp

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb05905.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The basic principles of a new technique for counting fish moving up or down stream are given. The counter is based on the ability to detect the presence of fish in an acoustic beam directed across the river. The counter is capable of counting several fish moving up or down stream simultaneously and is designed for use in wide open channels. The results of field trials with the equipment at two different sites are discussed together with the problems encountered. The results obtained are in good agreement with other methods of counting fish but the totals obtained were insufficient to put confidence limits on the counter.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb05906.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Records from salmon counters at hydro‐electric dams, and of angling results, in the Tay‐Tummel‐Garry river system are analysed. Spring runs of ascending salmon have decreased since at least 1950, but summer and autumn runs have increased since 1959. Hydro‐electric developments are not responsible for these changes, nor for the decrease in the average weight of salmon in the system. Possible environmental factors are discussed, and a method suggested whereby the ratio of sizes of salmon populations in branches of a river system may be estimated. The numbers of descending kelts have recently increased, but the times of downstream migration have not

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb05907.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The seasonaliy of temperature tolerance using thiourea‐treated, normal and thyroxine treated white perch was determined after laboratory acclimation and LD50 values calculated by normit analysis. Treatment effects, reflected in slight shifts in LD50 values were evident. However, these did not fit a consistent pattern of thyroidal involvement in temperature tolerance.When specimens of known thyroidal functional state were used in tolerance tests, results, similar to the seasonal tolerance tests, were obtained. Thus, although the white perch has a functioning thyroid capable of forming radiohormone and this capability was experimentally varied in these tests, no tolerance shifts were noted.Data obtained in tolerance testing were statistically adjusted to partition out variation due to differences in acclimation temperatures (season) and to test for treatment (thyroidal functional state) effects. Treatment difference was not significant while that due to season was significant (P<0.01). Thyroidal functional state was thus unrelated to toleranc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb05908.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Books reviewed in this article.FISH IN RESEARCH edited by Otto W. Neuhaus&John E. Halver.HANDBOOK ON BREEDING OF INDIAN MAJOR CARPS BY PITUITARY HORMONE INJECTION by S. L. Chondar.FISH PHYSIOLOGY VOL. 1. EXCRETION, IONIC REGULATION AND METABOLISM edited by W. S. Hoar&D. J Randall.THE OCEAN, a Scientific American Book.FISH PHYSIOLOGY Vol. II. THE ENDOCRINE SYSTEM edited by W. S. Hoar and D. J. Randall.ANTARCTIC ECOLOGY edited by M. W. Holdgate.COMPARATIVE FUNCTIONAL ANATOMY OF THE NANDIDAE (PISCES: TELEOSTEI) by Karel F. Liem.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1971.tb05909.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY