摘要:

Bovine growth hormone (GH) given daily to rainbow trout,Sulmo gairdnerifor 4 or 7 days at either 10.00 or 14.00 hours, significantly increased plasma free fatty acid (FFA) levels but had not effect on plasma cholesterol levels. Liver lipid content of the GH‐injected trout after seven injections was significantly lower than comparable controls in groups injected at both 10.00 and 14.00 hours. There were no apparent effects of GH on carcass or muscle lipid content although in fish injected and sampled at 14.00 hours there was a significant correlation between the number of injections and carcass lipid content.Changes in hepatosomatic index (HSI), liver, muscle and carcass lipid content, plasma FFA and cholesterol concentrations and somatotrop activity during food‐deprivation for up to 60 days are described. Despite significant decreases in liver and muscle lipid content and increases in plasma FFA levels in food‐deprived fish, there was no concomitant change in apparent somatotrop activity.The data are interpreted to indicate that although exogenous GH, in the doses used here, appears to stimulate mobilization of lipid reserves, particularly from the liver, there is no evidence that enforced changes in lipid reserves elicits a response of the endogenous somatotrop

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03817.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The gonads of immature female triploid plaice (Pleuronectes plafcssa) and plaice × flounder (Platichthys flesus) hybrids produced from cold‐shocked eggs were examined. They were less than half the size of those in diploids of similar age and contained only small numbers of developing oocytes. These were similar both in size and cytological appearance to those in the controls. The bulk of the ovarian tissue was composed of nests of small undifferentiated cells resembling the oogonia in the ovaries of diploid fish. Mature, 5 year old triploid hybrids which had not produced eggs over the previous two spawning seasons were killed in January when the diploid controls were nearing spawning condition. The ovaries of these fish were smaller than those of the controls and contained degenerating oocytes at maturation stage V. The advantage of sterile female triploid fish for fish‐cultivation is discu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03818.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The effect of increased available dietary carbohydrate on the tolerance of waterborne copper by rainbow trout was investigated. Trout were reared for six to eight weeks on one of four isocaloric and isonitrogenous diets which varied in available carbohydrate content due to either processing (extrusion v. steam‐pelleting) or supplementation with cerelose (0 or 21%). The incipient lethal level (ILL) of copper for trout reared on the low‐available‐carbohydrate steam‐pelleted diet was 350 μg I−1, significantly higher than the 276 μg I−1shown for trout reared on the high‐available‐carbohydrate extruded diet. The ILL of copper for the low‐carbohydrate group (0% cerelose) was 408 μg I−1, significantly higher than the ILL of 246 μg I−1of trout reared on the high‐carbohydrate diet (21% cerelose). Increased available dietary carbohydrate resulted in increased liver glycogen content and liver‐body weight ratios and decreased liver protein content. Significant correlations were evident between waterborne copper tolerance and liver glycogen, liver‐body weight ratios and liver protein. Relative to those on high carbohydrate diets, livers of fish on low‐carbohydrate diets contained higher concentrations of copper after seven days of exposure to 0 or 196 μg I−1of copper. The elevated liver glycogen levels, resulting from increased dietary carbohydrate, are thought to have impaired liver func

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03819.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Twenty‐two salmon smolts,Salmo salarL., carrying miniature sonic tags were tracked individually for periods of up to 175 h in Loch Voil, Scotland, during May 1979 and 1980. Activity was predominantly nocturnal, 80% occurring between 21.00 and 06.00 hours, and was apparently undirected. Average velocities during this active interval were 0.6 body lengths per second (bl s−1), with 98 and 93% of the time spent moving at less than 2 and less than 1 bl s−1, respectively. The rates of downstream displacement were 0.04 bl s−1in 1979 and 0.01 bl s−1in 1980. The direction of displacement of smolts and of movement of water at a depth of 1 m was positively correlated (P<0.001) and smolt displacement was biassed slightly ahead of water movement. Mean step lengths were 141 and 200 m in 1979 and 1980, respectively. Rates of downstream passage of 327 ICES plate‐tagged smolts released 16.8 km upstream of the fish trap at Clunie dam, Loch Tummel, during the spring migrations of 1975 and 1976 averaged 0.13 bl s−1in each year: net surface water movement was about 3.7 times this rate during the same intervals. These data are consistent with the model of passive smolt migration postulated by Tytleret al.(1978) and suggest that the active component required to ensure passage through a loch (Thorpe&Morgan, 1978)

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03820.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

During this study, anglers caught over 580 kg of fish, comprising over 29 500 individuals of 14 species. Nine times as many gudgeon,Gobio gobio, as roach,Rutilus rutilus, were caught. Gudgeon represented 35.94% of the total catch weight compared with 44.64% for roach. The mean total catch per man‐hour was 8.9 fish and the mean catch rate was 176 g per man‐hour. Population estimates for fish longer than 12 cm for all species other than gudgeon and bleak,Alburnus alburnus, gave fish densities of 0.21 fish m−2, the roach population was 0.15 m−2, and that for daceLeuciscus leuciscus, 0.02 m−2. The population density for all sizes of all species caught was estimated to be 2.25 fish m−2.The fish biomass available to the angler was 447 kg ha−2. The rate of exploitation of the fishery over the period of sampling was high at 17%, representing an annual exploitatio

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03821.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Mechanisms that might compensate for changes in mortality are well known but documentation of their operation and determination of their relative capacities is difficult. In this study the potential of lake whitefish to compensate for fishing mortality is quantified using a conventional fishery stock assessment model. The mechanisms examined are proportion of females, fecundity, survival of eggs and larvae, decrease in age at maturity and growth. The change in each of these parameters necessary to maintain constant recruitment with increasing fishing pressure is determined. Decrease in age of maturity and increased survival of larvae and eggs have the greatest potential for compensation. The total capacity for compensation appears large even when the mechanisms are considered alone. A review of several lake whitefish population studies indicates a large variation in the vital statistics. There is a close relation between total mortality and growth. There is also a close relation between growth and age at maturity. The analyses indicate that increased fishing results in increased growth which then results in a lower age at maturity. This feedback mechanism enables lake whitefish to respond to changes in environmental conditions and on average to maintain a birth rate in balance with mortality.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03822.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The ultrastructure and chemical reactivity of teleostean specific (‘atrial’) heart granules (SHG) are described. In atrial cells ofGlyptocephalus cynoglossusandGadus morhua, large aggregations of SHG occur in areas of the sacroplasm rich in glycogen and poor in myofibrils. The SHG often appear to be in a process of lysis. A number of heart granules were also noted in atrial cells ofCichlasoma meeki, Pistella riddleiandSebastes viviparus. although large aggregations were not seen. The mean diameters of SHG inG. cynoglossusandS. viviparusare 110 and 210 nm, respectively. SHG are regularly found in ventricular cells, although less frequently than in the atrium. Ultrahistochemical tests suggest that the teleostean SHG mainly contain prote

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03823.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Respiratory and gill ventilatory responses of Sacramento blackfish to three environmental temperatures (12, 20 and 28°C) and four environmental dissolved oxygen concentrations (130, 90, 65 and 40 torr PO2) were examined to determine physiological strategies of survival in eutrophic lakes and suitibility for culture conditions. Situated in van Dam‐type respirometers, experimental blackfish showed increased gill ventilatory flows from increased ventilatory frequencies and stroke volumes to meet higher respiratory oxygen demands at increased temperatures. Ventilation volumes also increased at reduced environmental dissolved oxygen levels by increased ventilatory stroke volumes alone, except at 28°C where frequency increases were also measured. Oxygen consumption rates remained essentially constant with declining dissolved oxygen, except at 28°C where excitement elevated respiratory metabolism at 65 and 40 torr. Percentage utilization of oxygen increased with temperature from 12°C, but levels at 20 and 28°C were insignificantly different. Contrary to most studies on other species, there was no change in percentage utilization under hypoxic conditions even with 4.7‐fold increases in ventilation volume in excited fish at 28°C. The ability of blackfish to survive in hypoxic waters is quantitatively compared with other species by calculation of a respiratory efficiency index (I), which includes the relationship between ventilation volume and percentage utilization of oxygen under normoxic and hypoxic conditions as well as the half‐saturation value (P50) of the species' blood

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03824.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

This paper describes the gravel type and structure of brown trout spawning gravels in Teesdale, the flow characteristics of the spawning sites and the size of redds. Factors influencing redd size are investigated and it is concluded that female size is a major factor. Relationships are established between various redd characteristics and the fork length of female fish. The findings are discussed in relation to the existing literature concerning salmonid spawning sites.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03825.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Book reviewed in this article:THE SALMON RIVERS OF SCOTLAND, by Derek Mills&Neil Graesser.THE BIBLIOGRAPHY OFANGUlLLASPP. (PISCES TELEOSTEI), by E. W. Liewes.FISH DISEASES. Third COPRAQ‐Session, edited by W. Ahn

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03826.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY