ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb05111.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

A new speciesof Dermocystidiumis reported to be the causative agent of three outbreaks of gill disease in carp observed in recent years in Czechoslovakia. No other parasites or influences could be held responsible for the disease. It is suggested that at least some of gill disease of unknown aetiology in carp is due to dermocystidia, and the disease might be distributed in many regions of Europe. A description of a greater part of the developmental cycle of the speciesD. cyprinin.sp. Červinka et Lom, is presented, supplemented by a discussion of other species of the genus. A summary of known facts on the host‐parasite relation in these parasites is also giv

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb05112.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The scales ofTilapia mossambicaPeters*from Lake Sibaya show clear rings formed by broken, widely‐spaced circuli in the anterior field. In order to determine the rate and time of scale ring formation, the number of circuli in the marginal increment was determined. Five scales from the pectoral region of 2223 fishes caught at regular intervals over two years were examined. When plotted as histograms, the number of circuli in the marginal increment showed a sharp movement to the left in September–October and again in January, indicating that the rings were formed during these months in the majority of fish examined. Pre‐ and postbreeding feeding migrations, and increases in condition factor, were associated with scale ring formation. Otoliths and opercula were also examined for age determination. Annual length increments were calculated for 450T. mossambicacollected throughout the year, and growth curves plotted.T. mossambicafrom Sibaya reach maturity after one year at a standard length of about 8 cm in females, and after two years at 10 cm in males. The breeding population had a standard length mode of 11–12 cm in females and 17 cm in males. The maximum final size was abou

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb05113.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Two‐hundred and nine fish of 13 species from Laurel Creek, Ontario, were examined for parasites between May and October 1973. Eighty‐four species of parasites (22 of Protozoa, 24 of Monogenea, 17 of Digenea, 11 of Cestoda, 4 of Nematoda, 1 of Hirudinea, 1 of glochidia, and 4 of Crustacea) were collected and are listed and discus

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb05114.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Data on the migratory behaviour of salmonids were collected at a gauging weir by means of a restivity fish‐counter which triggered a motor‐driven 35 mm still camera to provide photographic records of passing fish. A clear bimodal seasonal pattern of movement was observed in three consecutive years with peaks during June–August and October–December. Daily variations in the rate of movement could not be correlated with changes in discharge or temperature. Salmonids tended to move at discharges lower than those generally available. This contrasts with other published work and was attributed to the more equitable flow‐pattern of chalk rivers. There was no optimal temperature associated with movements. Some evidence suggested that the largest fish moved earlier in the year but this was not marked. In clear water most movement occurred during the hours of darkness but during floods, when the river was turbid, the diurnal pattern tended to be reversed with greatest movement during the hours of daylight. Most fish negotiated the weir close to the bottom, well below mean velocity, and took a central path through the flume. Although analysis of upstream migratory behaviour was hindered by the lack of data on the numbers of fish available below the counting point it was concluded that the basic pattern of migration is established by time (season). Changes in discharge, light intensity and other parameters may then play a secondary role in modifying the details of the pattern but attention is drawn to records of movements in regulated flows where a remarkably constant pattern is shown from yea

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb05115.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Gonad development was studied in young carp of the European and Chinese (big‐belly) races. The effects of age and body weight on gonad and egg size were partitioned and the following findings were made: (i) Gonad weight was correlated, in both males and females, with body weight, but proportional gonad weight, i.e. the ratio gonad weight divided by body weight, was independent of body weight, (ii) Proportional gonad weight had reached its maximum value in one year old males, but it more than doubled in two year old females, (iii) Egg size of two year old females was more than twice the size of eggs of one year old females, (iv) The European and Chinese races of carp differed in several aspects of gonad development. In particular, the Chinese matured earlier and their relative gonad sizes were considerably larger, (v) Genetic variation in gonad development was also found within the European race, where faster rate of development is dominant over slower rate. The evolutionary implications of the above differences were discusse

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb05116.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Encapsulated fish hooks were found free in the stomachsof Plectropomus maculatus(Bloch). The tissue surrounded only the ferrous part of the hooks which in each case was badly corroded, the brass swivel and plastic sleeve were undamaged. Histological examination showed that the hooks were first surrounded by dense collagen and then by vascularized smooth muscle.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb05117.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Changes in haematocrit values under lowered oxygen tension and aerobically treated blood samples of rainbow troutSalmo gairdneri(Richardson), landlocked Baltic salmonS. salar(L.), brown troutS. trutta lacustris(L.) and lake troutSalvelinus namaycush(Walbaum) have been studiedin vitro. The mean haematocrit value increased during 2 h incubation under lowered oxygen tension by 32.7 ± 3.1% in rainbow trout, 28.2 ± 2.8% in landlocked Baltic salmon, 29.2 ± 5.6% in brown trout and 25.2 ± 2.8% in lake trout. During corresponding incubation with oxygen the mean haematocrit value decreased below the starting level by 18.1 ± 1.9% in rainbow trout, 18.3 ± 4.8% in landlocked Baltic salmon, 22.4 ± 0.7% in brown trout and 11.8 ± 1.7% in lake trout. Consequently, the changes in the haematocrit values were greater in the species belonging to the genusSalmothan in that of the genusSalvelinus. The increase in the haematocrit values seems to have resulted from swelling of the erythrocytes and their decrease is similarly attributable to shrinking of the cells. The reasons for this swelling, which may be complicated, and its apparent significance for haematocrit determinations are di

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb05118.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Wild plaice and flounders with lymphocystis were sampled and their lesion distribution noted. Regression of the lymphocystis cells was seen by histology and a host response including macrophages and immune cells occurred. Antibodies were detectable by a double diffusion precipitin test. The epidemiology is discussed with reference to these findings and to the life histories of the two species.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb05119.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The stomachs of 148 elasmobranch and teleost fishes representing 35 families and 62 species were examined by viscometry for cellulase activity. Sixteen species of Georgia estuarine fish and the freshwater fish,Ictalurus punctatus(Rafinesque) showed some cellulase activity. Elasmobranchs and teleosts captured in Florida Bay, Florida, and over the continental shelf off Georgia lacked cellulase activity. Cellulase activity in fishes is probably produced by microflora of the alimentary tract.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1974.tb05120.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY