摘要:

The factors influencing the selection of food by eels,Anguilla anguilla, whiting,Merlanglus merlangius, sprat,Sprattus sprattus, and stickleback,Gasterosteus aculeatushave been investigated by analysing collections made in the Severn Estuary for 1 year. Non–migratory (yellow) eels measuring from 19–5–56–5 cm in length fed mainly on either the decapodCrangon vulgarisor on the mysidNeomysis integerduring the warmer months but ceased to feed in the winter. Whiting measuring between 2–5 and 15 cm fed almost exclusively onC. vulgaris, N.integerand the sand goby,Pomatoschistus minutus.Sprats fed chiefly on either the arnphipodGammarus salinusorN. integer.Sticklebacks seldom contained any food in their stomachs despite the presence of large quantities of suitable prey and the high level of hunting efficiency.Gammarus salinus, although normally abundant in the environment, was usually ingested in disproportionately small quantities by all fishes except sprats reflecting its concealment among floating weeds and a selection against small (less than 1 cm) organisms. Because of the limitations of size and the unusually efficient escape reaction of larger animals, only young representatives ofCrangon vulgariswere captured. The isopodEurydice pulchrawas rarely eaten by any of the fishes even though it was common in the environment. Burrowing polychaetes, mainlyNereis diversicolor, were never utilized possibly due to the difficulty involved in removing these organisms from the substrate.Neomysis integerwas the most frequently consumed organism. Although the average length of prey ingested by the whitings increased with the size of fish, this was not the case for the other species. The proportion of non–feeding eels and the dry weight of stomach contents of this species depended on the temperature of the water but were not related to the availability of prey and tidal conditions whereas the feeding of whiting could not be related to any environmenta

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04686.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Samples of cyprinid fishes from Esthwaite Water, Westmorland, have been examined and identified as roach (Rutilus rutilus), rudd (Scardinius erythrophthalmus), with a high degree (37%) of hybridization between these species. The distinguishing features of roach and rudd are discussed in the light of the difficulty of distinguishing the roach x rudd hybrid from the roach. It is concluded that the only reliable characters are the number and external morphology of the pharyngeal teeth.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04687.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

A total of 210 samples of haemoglobin ofTrachurus trachurus(L.) caught in the Gulf of Trieste in 1972–1973, were analysed in search of haemoglobin polymorphism. Genetic polymorphism may be used as a genetic marker to identify sub–populations on the basis of allele frequencies.All the samples analysed produced the same haemoglobinic pattern, composed of six bands. The quantitative differences noted between the various fractions were not sufficient to demonstrate the existence of different phenotypes.Denaturation tests carried out by treating erythrocytes with non–sterile physiological solutions or by keeping the haemolysate at room temperature before electrophoresis, resulted in new patterns. This result shows the importance of the careful treatment of blood samples to assure reliable re

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04688.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

An antigen abstract ofProleptus obtususan intestinal nematode of the common dogfish has been shown to precipitate with a serum component of plaice. As the parasite has never been shown to infect plaice it is suggested that perhaps the serum component might be C–reactive protein (CRP). However, characterization of the component revealed that it was specific immunoglobulin analagous to antibody of the IgM class. It is suggested the helminth antigen involved is cross–reacting with a common antigen to which the plaice is normally expo

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04689.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Observations on spawning and movements of trout over 7.5 km of chalkstream indicate five discrete stages of the life history with respect to migrations. (1) Downstream movements from area of hatching to nursery areas, to 6 months of age. (2) Downstream again from the nursery areas to areas of adult growth between 6 months and 15 months of age. (3) A stage of very limited movements by adults between 15 months old and spawning. (4) Upstream spawning migration. (5) Downstream movements following spawning. These movements are similar in principle to those in upland systems though are relatively more local, reflecting the juxtaposition of areas suitable for all stages.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04690.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Marine fishes caught in the Skagerrak, 27 different species representing various groups of fishes (Cyclostomi, Holocephali, Elasmobranchii and Teleostei), were examined for the following haematological and biochemical blood parameters: haematocrit, haemoglobin, mean corpuscle haemoglobin concentration, total plasma protein, blood glucose and blood lactate. Interspecies variations as well as variations within some species were observed. The haemoglobin values for all species showed a positive correlation to the corresponding haematocrit values. Relatively low values for haematocrit and haemoglobin were found in cyclostomes, holocephaleans and elasmobranchii compared to the majority of teleosts. Within the teleost group, the haematocrit and haemoglobin levels were positively correlated with the activity of the fish species. The cyclostomeMyxine glutimsaL. had a total plasma protein content in the same range as most teleosts, whereas holocephaleans, elasmobranchii and the deep‐water teleostCoryphaenoides rupestrisGunnerus showed comparatively low values. Among teleosts some relationship seemed to exist between the total plasma protein level and the activity of the fish species. In addition, a correlation between plasma protein content and levels of blood lipids were noted. Values for blood glucose and blood lactate were found to be lower in cyclostomes, holocephaleans and elasmobranchii than in most teleosts. Higher blood glucose levels were observed in the more active teleost specie

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04691.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

The pathological effects often lethal concentrations of the anionic detergent, sodium lauryl sulphate, on the gillsof Salmo truttaL. have been studied by light and electron microscopy. At concentrations to 120 mg/1 (medium survival times>1 h), epithelial cell death is associated with lysosome formation. Acute inflammation of the gill tissue, extensive detachment of the epithelium and, except at the lowest concentrations, collapse of the pillar cell system occur. At concentrations above 120 mg/1 (medium survival times<1 h) very rapid lysis of cells results in the complete disruption of cellular and tissue structure. Changes in the gross structure of the gills are explainable in terms of the rate and nature of toxic action at the cellular level. Review of the biomedical literature suggests the observed effects of sodium lauryl sulphate on gill cells correspond to the two mechanisms by which detergents cause death in isolated cells. These are autolysis, i.e. lysis by the action of the cell's own enzymes, induced by an initial lesion in the cell membrane whose precise nature is not known; and rapid lysis by the direct action of the detergent on the cell constituents.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04692.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

The haemoglobin patterns of adult and young larval stages of the fish speciesSarotherodon mossambicuswere determined by polyacrylamide–gel electrophoresis. Oxygen affinity determinations of the adult and larval haemolysates and of each haemoglobin component of the adult indicates that the affinity changes with the pH, temperature and osmotic pressure. The possible evolutionary significance of the multiple haemoglobins is discussed. The electrophoretic pattern of adultS. leucostictus, a species closely related toS. mossambicuswas also determined and used as a comparative stud

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb04693.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY