摘要:

The diet of sea trout in some of the sea lochs of the west coast of Scotland was investigated. The contents of 986 sea trout stomachs from the Loch Etive area (1970–1973), and 291 stomachs from the Loch Eil area (1964–1973), were examined and the composition of the diet, seasonal changes and the effect of trout size were analysed using frequency of occurrence, dry weight and number of organisms methods. Benthic feeding (crustacea and annelids) was more important in winter while midwater and surface organisms (young fish and insects) were preferred in summer. Young fish (mainly clupeids and sand eels) featured more in the diet of larger trout (≤21 cm) than in the smaller size range (≥21 cm). Surveys of 24‐h were completed in June and September, 1972, and indicated that availability of food was the main factor influencing the presence or absence of trout. Bottom feeding was greatest during the day while the amount of midwater and surface feeding tended to increase between sunset an

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04673.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

The rate of expansion in volume of the bulbus arteriosus with increase in pressure is measured. From this it is calculated the elastic rebound of the bulbus can account for approximately 25 % of blood flow in the ventral aorta; this proportion decreases as cardiac output increases. The structure of the wall of the bulbus is shown to consist of a compact outer layer with a series of separate longitudinal elements on the inner surface. These elements are connected to the compact layer by numerous radial fibres. This structure equalizes strain in all the structural elements of the wall during large changes in volume. Evidence is discussed which shows that the bulbus arteriosus in teleosts is morphologically and biochemically distinct from the ventral aorta. The bulbus is probably of cardiac origin rather than an expansion of the posterior end of the aorta as generally supposed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04674.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

General morphology of the lateral line of juvenile steelhead trout,Salmo gairdneri,is described. Through electrophysiological monitoring of individual nerve fibres, control patterns for spontaneous activity and reaction to sensory receptor stimulation were established. Spontaneous activity has a positive correlation with temperature and number of receptors innervated. Presence of directional sensitivity and response to near field water displacement at different frequencies is similar to that found in other fishes and amphibians. Normal lateral line response to a standardized set of stimuli was compared with the response of fish affected by gas‐bubble disease. Results show that as gas emboli formed in the scale pockets of the trunk lateral line of stressed fish, the ability to respond to stimuli was either diminished or completely disappeared. Further testing demonstrated that this sensory loss was reversible and that upon return to equilibrated water gas emboli disappeared and normal function was regained. This sublethal effect of gas‐bubble disease on the lateral line sensory system may be an important element contributing to indirect mortal

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04675.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

ThreeLatesspecies,L. mariae(Stdr.),L. microlepis(Blgr.),L. angustifrons(Blgr.) andLuciolates stappersii(Blgr.) which belongs to a monotypic genus occur only in Lake Tanganyika. They are the principal predators in the pelagic and benthic fish communities. Data are presented on distribution, growth, length‐weight relationships, condition, reproduction and food in theLatesspp. After a post‐larval pelagic phase, eachLatessp, spends 1 year in littoral weed. Thereafter,L. mariaeadopts a benthic habitat moving into deep water,L. microlepisbecomes exclusively pelagic andL. angustifronsoccurs from the littoral to near the limit of the oxygenated zone. Cycles in breeding correspond with seasonal maxima in clupeid prey, and changes in growth rate within a year are probably related to physiological cycles rather than to variations in the physical environment. Salient morphological and ecological adaptations are discussed.Local abundance and vagility ofLatesstocks seem related to basin morphometry and depth of the oxygenated layer.L. microlepishas most vagility. TheLatesappear highly susceptible to intensive fishing by purse‐seines, and have been fished‐up in the southeast arm in Zambia and in the Burundi sector, where only small populations remain. With reduced predation, the clupeid biomass has increased. The change to dominance of small species may be accomplished rapidly in L. Tanganyika under such conditions of exploitation. However, the type of species successions well‐known in large temperate lakes are unlikely to occur because of the high degree of specialization in these fishes. A simplified pelagic community is foreseen, consisting almost entirely of clupeids andLuciolates, in which the total fish biomass will be determined above some intensive level of fishing and from year to year by the environmental factors controlling survival of young and plank‐tonic food supply. Quantitative equilibrium between the few species will be determined mainly by gear selectivity and total fishing stress, and the community may be sufficiently robust by reason of its rapid turn‐over rates to permit a largely empirical approach

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04676.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

A method is described whereby the efficiencies of two electric fishing machines may be compared by fishing a closed population on eight occasions at short intervals, the two fishing machines being used alternately. A practical example is given and the merits of the method are discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04677.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

A survey to determine presence of parasitic and disease organisms and their effect on estuarine populations of striped bass,Morone saxatilis(Walbaum), was conducted monthly from May 1972 to May 1973. A total of 514 fish over 1 year old and 140 young‐of‐the‐year were examined using standard necropsy and histological procedures. Other species of fishes were studied to determine the specificity of striped bass parasites and to determine if other fishes were reservoirs for striped bass pathogens. Forty‐five species of parasitic organisms from viruses to Metazoa were recognized from striped bass. Heavy infections by some were associated with definite pathological con

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04678.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Book review in this article:RIVER ECOLOGY–STUDIES IN ECOLOGY. Edited by B. A. Whitton.PRINCIPLES OF FISHERY SCIENCE By W. Harry Everhart, Alfred W. Eipper and William D. Youngs.THE NILE, BIOLOGY OF AN ANCIENT RIVER Edited by Julian Rzoska. Published by Dr W. JunkLIFE CYCLES OF FISH–PHYSIOLOGY AND BIOCHEMISTRY By Shul'man. Translated by N. KanerA BIOLOGICAL SURVEY OF THE AFON TAP By Welsh National Water Development Authority, November 1975.TECHNOLOGY OF MACKEREL FISHERY: BIBLIOGRAPHY AND SURVEY OF LITERATURE by J. R. Dingle.DEPTH CHARTS OF THE CUMBRIAN LAKES by A. E. Ramsbottom.LIVINGMARINE RESOURCES OF NEWFOUNDLAND–LABRADOR: STATUS AND POTENTIAL by A. T. Pinhorn.BETTER ANGLING WITH SIMPLE SCIENCE by Mary M.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04679.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY