摘要:

Vulnerability to predation, resistance to high temperature, weight‐length relationships, and fecundity were compared for fish with and without or with light and heavy infestations of three ectoparasites. The fish and parasites were fathead minnow (Pimephales promelas) with anchor worm (Lernaea cyprinaceae);brook trout (Salvelinus fontinalis) with gill lice (Salmincola edwardsii);and yellow perch (Perca flavescens) with black‐spot (NeascusofCrassiphiala bulboglossa).The only sublethal effect found was that of gill lice, which reduced resistance of brook trout to high temperature. None of the three ectoparasites increased vulnerability offish to predation by piscivorous f

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04601.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The proportion of the mytomal muscle that comprises red or slow muscle fibres was assessed histologically for 84 species of marine fish. The results are discussed in relation to their mode of life.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04602.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

An epizootic in imported carp (Cyprinus carpioL.) was examined by bacteriological, viro‐logical and histological methods. The microbiological investigations did not reveal the aetiology of the disease, but the histological description of the lesions is similar to that for carp erythrodermatitis ‘

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04603.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Juvenile coho salmonOncorhynchus kisutch(Walbaum) received a diet of Oregon Moist Pellets supplemented with either 10, 1, 0.2 or 0 ppm of 17α‐methyltestosterone for 72 weeks. The fish were held in fresh water during the first 57 weeks and in salt water during the remaining time of the study. At the end of the fresh water residency, the fish receiving 10 and 1 ppm of steroid showed a net increase in weight of 125 and 71 % respectively over the controls. Both test groups also gained in length, but the 10 ppm group gained proportionately less, which resulted in a thicker body. After transfer to salt water at the normal time of smolting, there was a decrease in the rate of growth in weight and length of the two groups receiving the high doses of steroid. The decrease was most noticeable in the 10 ppm group and a number of mortalities occurred in this group.Testes of fish receiving 10 ppm of the steroid became hypertrophied and later degenerated with loss of spertnatogonia; the ovaries were not affected. 17α‐methyltestosterone fed at 10 ppm for 49 weeks increased the lipid content of the flesh from 2.4 to 3.5 % and decreased the amount of flesh from 35.0 to 28.5 % of body weight. No change in the moisture content was found. External changes noted in the 10 ppm group included loss of silvering, deepening of the body, particularly in the region of the anal fin, and widening of the lowe

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04604.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

This is a review of some of the literature on the use of chromosome techniques with fish. There is a need for developing methods which leave the animal alive. Such a test is the leukocyte culture method used in human medicine. Once a reliable test has been developed the results should show more consistent karyotypes and better morphology thus providing information of use in cytotaxonomy, fish‐breeding and in studying the effects of sub‐lethal levels of water pollutants on f

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04605.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The eyes of more than 24 000 northern North Sea whiting were examined for infection withGilquinia squaliplerocercoids. Infection, which is apparently non‐seasonal, begins when the fish are aged 1 +, builds up to a peak at 2+ to 4+, and decreases thereafter. The intensity of infection ranged from 1–18 plerocercoids per fish. Evidence is presented of the development of immunity in whiting toG. squali, and observations on the parasite's eggs suggests that they are not randomly distributed but tend to aggregate. One or both of these features could give rise to the negative binomial type of frequency distribution observed. The frequency of left eye infection was consistently greater than that of right

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04606.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Adult Atlantic salmon were captured in the Miramichi esturary, tagged with ultrasonic transmitters, and released. Nine fish were tracked for a total of 425 h, spanning 71 flood and ebb tides. There was drifting with the tidal currents, and holding of position relative to land. Fish that achieved overall upstream progress did so by drifting with flood tidal currents and by stemming the ebb currents. Fish which did not achieve upstream progress also drifted with flood tidal currents, but these fish did not stem the ebb currents and dropped back downstream during ebb tides. No differences in movement patterns were apparent for different times of day or wind conditions.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04607.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

During 1972 the downstream movement of anadromous artic char,Salvelinus alpinusL., from two rivers flowing into Cumberland Sound, Baffin Island, began during the middle of May and was completed within 2 weeks. This movement took place during both the day and night. Upon reaching saltwater, many char older than 9 years (longer than 20 cm) began to migrate along the shore of the Sound at a rate of 0–6–0‐9 km/day with the result that the average maximum distance travelled from the natal river was 40–50 km. Char 6–9 years old, 10–20 cm in length, remained much closer to the rivers while those younger than 5 years never entered saltwater. During the period of saltwater residence, the fish frequently moved into the intertidal zone and freshwater. Maturing fish of both sexes were occasionally found in saltwater. The upstream migration to the lakes began during the second week of August and was completed within 5–6 weeks. Females tended to ascend the rivers before males, although fish of all different size and age migrated upstream simultaneously. Migration occurred during both the day and night. The maximum distance anadromous char moved from saltwater was 40 km. The char were found only in freshwater between May and September and were normally located near the bottom of lakes at a depth of 15–40 m. During this period, large scale movements were probably very limited. Average annual mortality was estimated at 16.0% per year with the highest rates (25–30%) occurring at ages 10 and 15–17 years. Many fish probably died of old age but physical deterioration during and after spawning was also an impor

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04608.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Experiments show that the first of a series of replicate electric fishings can cause a decrease in catchability so that the second and subsequent catches are made from what is, effectively, a reduced population. Depletion (DeLury) estimates can be thus seriously low. Species affected are roachRutilus rutilus(L.), gudgeonGobio gobio(L.), ruddScardinius erythophthalmus(L.) and, from other published data, probably rainbow troutSalmo gairdneriRichardson and eelsAnguilla anguilla(L.). Being caught does not, apparently, cause fish to become less catchable. The reason why an electric field causes a proportion of a population to become uncatchable is obscure but it may be that refractory behaviour is involved; the effect lasts for between 3 and 24 h. A method is given for adjusting DeLury estimates for decreased catchability.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04609.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Two distinct types ofRenicolametacercariae were found in herring,Clupea harengusL., from Scottish waters, and one in anchovies,Engraulis encrasicholus(L.), from the central North Sea. Both constitute new host records. These parasites may prove to be of value as biological tags for herring and other clupeoid fish.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04610.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY