摘要:

Oxygen uptake by plaice,Pleuronectes platessa L., was measured using both ‘closed’ and ‘flow‐through’ respirometers. Oxygen consumption was found to be influenced by oxygen concentrations below a critical level of 45–60 mmHg. Rates of oxygen uptake were also affected by fish size, temperature and nutritional status. The problems involved in using values of oxygen consumption, determined in the laboratory, for estimating energy requirements of wild fish ar

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03951.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Multi‐mesh gill nets set at Rawlinson's Nab in the south basin of Windermere for 24 months from 1979 to 1981 caught predominantly charr and perch. Nets set parallel to the shore caught significantly fewer fish than those set perpendicular to the shore. Variability in the mean catches of perch increased from winter to summer when the size of the catches also increased. Charr were mostly caught from November until February. Estimates of variance associated with the geometric mean catch of a single net (set perpendicular to the shore) were calculated for the periods winter for the charr and winter, summer, spring and autumn for the perch. These variances were used to calculate 95 and 99% C.L. of the geometric mean. For limits to be below half or twice the geometric mean, 12 nets would have to be used for charr during winter. For perch the number of nets needed would be six in winter, 20 in spring and autumn and 40 in summer. It is concluded that the nets are of little value in assessing changes in stock abundanc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03952.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Water and protein contents of muscle and gonad index of sexually mature and immature cod of the same size were studied throughout a one‐year cycle. In mature cod, the gonad was found to increase isometrically with fish weight suggesting that the relative energy demand for gonadal growth is independent of fish size. Spawning took place in late March or early April. Similar seasonal variations of water and protein contents of the muscle occurred in both mature and immature cod. In December to February, the protein content reached a maximum and water content a minimum, and in March to April, protein content was low, whereas the water content of the muscle was at a maximum. Since mature and immature cod showed the same variations in body composition, it is suggested that little of the seasonal variations of mature cod can be explained by reproductive processe

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03953.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The literature on the blood chemistry of rainbow trout,Salmo gairdneriRich., is reviewed from the aspects of experimental methods, electrophoresis, normal values, environmental and endogenous factors including toxic substances and diseases.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03954.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Schaefer's and exponential models are used to predict the maximum sustainable yields (MSY) of the Nigerian inshore fish and shrimp resources. The MSY values for fish caught down to 40 and 50 m were 11684·09 and 13742·35 metric tonnes (t), respectively. For shrimp, the MSY estimated was 2008·02 t. It appeared that the inshore fishery still had room for expansion, but the shrimp resources seemed to be fully exploited under the prevailing circumstanc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03955.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The distribution of various age classes of salmon and trout was assessed in upland streams by electrofishing. Water depths and site gradients were measured and correlated to fish densities. The fry of both species were significantly more abundant in shallow water; up to 75·3% of salmon fry and 72·2% of trout fry were captured in sites of mean depth<20 cm. Older trout were found mainly in the deeper areas, with a maximum of 7·4% captured in sites<20 cm mean depth. Yearling fish were found in all the depth‐ranges sampled, but with a tendency for higher numbers in mid‐range depths. There were similar correlations in the abundance of each age class with the actual areas of shallow, mid‐range and deep water habitat available within sites. Correlations of fish density with gradient indicated that trout were limited in their distribution to areas of lower flow, whereas salmon were not. Since depth and gradient were significantly negatively correlated, there was an apparent preference of trout for slightly deeper habitats than the equivalent year classes of salmon. The observed habitat segregation is discussed in terms of competition and s

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03956.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The allocreadiid digeneanSphaerostoma bramae(Müller) was found in three of 602 eels,Anguilla anguilla(L.), caught over a period of 25 months from drains and rivers in the lower River Trent drainage area. Eleven, 15 and 32 specimens ofS. bramaewere found in the posterior 40% of the respective host's intestine. Concurrent infestations withProteocephalus macrocephalus, Acanthocephalus clavulaandRhaphidascaris acuswere observed. The results are discussed in relation to the helminthology and ecology of the eel

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03957.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The effect of feeding isocaloric test diets containing 35, 45 and 55% protein, with and without inclusion of the anabolic steroid hormone, ethylestrenol, was studied in rainbow trout,Salmo gairdneri, in relation to blood chemistry. The control (no hormone) and experimental diets (hormone‐supplemented), were fed for a total of 60 days, after which time all groups of fish were fed an identical commercial diet with no hormone for a further 30 days (withdrawal period). After 60 days, the body weights offish fed the 35 and 45% experimental diets were significantly greater than their respective controls, and after hormone withdrawal, increased growth was still apparent in the 35% experimental group.No significant changes in serum amino acid nitrogen (AAN), protein, or glucose in relation to the dietary protein level, or inclusion of steroid, were observed after 30 days. Serum creatinine, however, increased with an increase in dietary protein, and was significantly higher in the 35% experimental group than the respective control. After 60 days, the most significant observation was the marked increase in serum glucose with an increase in dietary protein, but respective control and experimental values were not significantly different at this time. Following a 30‐day withdrawal period, serum AAN in the 55% experimental group was significantly higher than the control, whereas serum protein, creatinine, and glucose stabilized to similar concentrations in all groups. Over the 90‐day period of feeding, in both control and experimental groups, serum AAN and protein tended to increase, serum creatinine and glucose to decrease, whilst haematocrit remained constant. It is concluded that addition of ethylestrenol to trout diets has apparently little effect on serum metabolite concentrations and haematocrit, the most significant variations being related more to diet composition and duration of

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03958.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03959.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The development of the retina of perch,Perca fluviatilisL., was studied for all developmental stages. The density of cones 100 μm‐1was found to decrease with age, although their actual numbers increased. All premetamorphosed perch had pure‐cone retinae, the rods developing at, or after metamorphosis. Retinomotor responses were found to commence after metamorphosis when the rods developed. Visual acuity, measured as the minimum separable angle (α), was observed to improve exponentially with age, and its value was found to depend more on the focal length of the lens, than on the number of cones in the retina. The cones in the unspecialized part of the retina were predominantly of the twin type and were related to single cones in a ratio of

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1982.tb03960.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY