摘要:

Principal components analysis revealed two main groups among 163Vibrio anguillarumcultures from diseased fish from Norwegian waters. Nearly all isolates from farmed salmonids fell in group I (arabinose positive) but those from wild fish, particularly saitheGadus virens, more commonly appeared in group II (arabinose negative).

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04099.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Starting with the second day after fertilization, largemouth bass embryos and larvae became increasingly sensitive to oxygen deficiency until the sixth day of life. On this day few survived exposure to 1 mg O2/l for 3 h at 20°C; many were damaged at 2 mg/1, but not at 2.5. Death was by asphyxiation or by starvation resulting from an apparent inability to close the lower jaw. On the seventh day the larvae became more resistant again, possibly because opercular movement began on that day. At 25°C the effects of reduced oxygen concentration were intensified, and even a concentration of 2.5 mg/1 became lethal in 3 h. At 3 mg O2/l and 20° the normally quiescent yolk‐sac larvae became very active and swam vertically to at least 5 or 6 cm above the substrate; 4 and 5 mg/1 had this effect at 23–24°. This behaviour could result in losses by predation and displacement from t

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04100.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The effects of temperature and ration size on the growth rate and gross efficiency of food conversion of juvenile rainbow troutSalmo gairdneriwere evaluated during 25‐day seasonal experiments. Rations ranged from near‐starvation to repletion levels. Test temperatures were 3 and 6°C higher than the controls which fluctuated dielly and seasonally. At rations near maintenance, elevated temperatures decreased trout growth. As the feeding rate increased the detrimental effect of temperature on growth was ameliorated. At repletion feeding levels, elevated temperature up to 17°C improved trout growth by increasing the maximum food consumption rate. With a temperature increase from 6.9 to 22.5°C maintenance rations increased from 2.2 to 7.5 % body weight per day. Gross efficiency was dependent upon ration level and temperature. As the food consumption rate increased, efficiency increased to a maximum, then generally declined at repletion levels. Elevated temperatures resulted in reduced efficiencies at low consumption rates but temperatures had little effect at high ration levels. A field study provided estimates of the food consumption relationships established in the laboratory, suggested any substantial increase of stream temperature without a concomitant increase of food abundance would result in decreased trout prod

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04101.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The growth rates of rainbow trout,Salmo gairdneri, which ranged in size from 0.6 to 5.2 g and were provided rations of three different sizes, were measured during a 15‐day study. The relative maintenance rations (food/gram of fish at zero growth rate) decreased with increases of fish size. Consequently when fish were kept at low ration levels the growth rates and gross efficiencies of food conversion of ‘large’ fish were greater than those of ‘small’ fish. However, as ration level increased, the effects of fish size grew at the same rates or slower than small fish. With increases of ration to the highest levels (9–12%/day) gross efficiency values for large fish began to decline while those for small fish continued

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04102.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

A study of the age, growth and feeding of the protogynous wrasseLabrus bergylta(Teleostei: Labridae) was made on 25 male and 316 female specimens taken from the southern coasts of the Isle of Man from October 1972 to October 1974. Age determination and back‐calculations for length were made from the opercular bones. The oldest male and female specimens were 29 and 25 years old respectively. The growth curves showed only a slight increase in growth rate after sexual inversion, and a pattern of slow irregular increase, with no pronounced levelling off in old fish. The time of sexual inversion varied widely: intersexual specimens of 5 and 14 years were found. The youngest functional male was 6 years old. The weight/length relationships of males and females were very similar and the following equation, derived from all individuals, was used to calculate weights for age utilizing the back‐calculated lengths:The mouth, pharyngeal teeth and gut length to fish length ratio (0.622) suggested an omnivorous diet. Analysis of gut contents confirmed this, with decapod Crustacea, isopods and molluscs the dominant food items. There were seasonal changes in feeding intensity and composition of the diet, related to temperature changes, onshore‐offshore migration patterns, availability of food items, and changes in habitat associated with matur

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04103.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

This paper records the unusual occurrence of the blue whiting (Micromesistius poutassou) from inshore waters of the west coast of Scotland from 1971 to 1974. The fish were O and I‐group and appeared to migrate into the area during the autumn and winter months. Data on growth, length for weight relationships and feeding are describe

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04104.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Roach, rudd and bream and hybrids between roach x rudd and roach x bream have been examined morphologically and by electrophoretic separation of their serum proteins. Identification by both methods agree and it is suggested biochemical methods of identification may be of value in cases of difficulty when distinguishing hybrids by morphological methods.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04105.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The effects of high environmental carbon dioxide tension (PCO2) on buffering status, pH, haematocrit, red blood cell (RBC) count, mean corpuscle volume (MCV), and chloride (Cl–) distribution in the blood of young salmon were investigated after 30 min and 24 h. An increase in blood buffering capacity was observed after 24 h. As compared to the preacclimation situation, haematocrit, RBC, MCV and Cl–content of the erythrocytes increased after 30 min but decreased if hypercapnia was sustained for 24 h. However the plasma bicarbonate (HCO3) content increased over the whole experimental period. Plasma Cl–content was decreased after 24 h, but the ratio of Cl–between erythrocytes and plasma increased at the onset of hypercapnia, then remained unchanged during the rest of the investigation

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04106.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Good correlations exist between condition and the amount of fat, protein and water present in youngTilapia rendalli, but extreme care must be exercised when determining the nature of these relationships. The use of percentages when expressing the amounts of each component should be avoided because such analyses can lead to erroneous results. Similarly the often used fat‐water relationship for predicting the fat content in fish should not be used as this also leads to erroneous results. The reasons for the poor relationships are discussed and methods for overcoming these problems are give

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04107.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

A technique is described for studying small scale distributional patterns of fish larvae in the pelagic region. A plankton net is mounted beneath the bows of a small boat, the contents of the net are emptied continually by a suction pump. This system has advantages over previous techniques as it allows a large number of small discrete samples to be taken over a wide area in a short space of time. Preliminary results showed the population of perch larvae in Llyn Tegid is extremely clumped and the overall abundance of the larvae decreases as samples are taken progressively further away from the south‐west end of the lak

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1977.tb04108.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY