摘要:

Although the ferox of Scottish Highland lochs (lakes) have long captured the interest of both laymen and scientists, no previous investigation of their biology or ecology has been undertaken. This paper is based on 141 ferox from 22 lochs collected during the last 22 years and the results from a recent investigation into their status and distribution. When the features of their environment and the distribution of what is apparently their main food source, the arctic charr, were investigated, two essential conditions governing the occurrence of ferox emerged and a third appeared to be important: (i) oligotrophic waters; (ii) the presence of charr and (iii) a large loch (over 100 ha in extent). Typically, ferox grow slowly during the first third of life but on reaching what may be a critical length enter into a phase of rapid growth and may eventually reach a size and age very much greater than that of the individuals in the normal trout population from which they arise. This pattern of growth contrasts markedy with that of large, fast growing brown trout from eutrophic waters in Scotland which do not reach the same extremes of age or size.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1979.tb03491.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Immune channel catfish lymphocytes were recovered from peripheral blood on an isotonic (250 mOsm) separation medium consisting of Ficoll‐Hypaque adjusted to a specific gravity of 1·065–1·070 g ml−1. At least two types of cells similar to T and B lymphocytes of higher vertebrates were observed. One type of lymphocyte, referred to as “small lymphocyte” possessed surface erythrocyte receptors and appeared to be analogous to mammalian T cells. A second type of lymphocyte analogous to mammalian B cell possessed surface immunoglobulins and was capable of cytoadherence withAeromonas hydr

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1979.tb03492.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

A population ofSolea vulgariswas transplanted in 1938 from the Mediterranean to a land locked brackish lake. In 1977, the morphology of these fishes was investigated and a number of measurements made and compared with those of fish caught in the Mediterranean. Among these variations was less vertebrae and fewer dorsal fin rays in the lake soles.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1979.tb03493.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Allocreadium fasciatusiis a common trematode occurring in the intestine of the fishAplocheilus melastigma. The distribution of this fluke inside the fish host has been studied for a period of one year. The fluke occurred throughout the year, the incidence ranged from 20 to 88, and the number of parasites per infected host varied from 1 to 58. The fluke exhibited a seasonal cycle of occurrence with a peak both in incidence and intensity in the month of September. For the rest of the year the population remained constant and there was a balance between recruitment and loss from the trematode populations. The maturation cycle ofA. fasciatusialso followed a seasonal pattern. Although the flukes were recruited in all the months, the peak invasion occurred in September. The large numbers of immature flukes received during this month became gravid by January. The availability of infective larvae was considered to be important in influencing the seasonal cycles.The incidence and intensity of infection were found to be independent of the size of the fish but female fish were noted to be the more heavily infected.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1979.tb03494.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Studies were conducted on the effect of clomiphene on ovulation and spawning in matureC. carpiopre‐treated with indomethacin. It was demonstrated that indomethacin caused a block to ovulation and spawning at two dose levels (5 and 10 μg−1g). This blockade could be overcome by two (10 μg−1g each) successive dosages of clomiphene given 7 and 31 h after the indomethacin treatment. When indomethacin and clomiphene treatments were given concomittantly, the inhibitory effects of indomethacin remained more pro

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1979.tb03495.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Haematocrit values, haemoglobin concentration, erythrocyte counts, leucocyte counts, erythrocyte sedimentation rate and clotting time ofLabeo rohitawere determined. The variations in haematological parameters in relation to the size and weight of the fish were also examined. Males had higher haematological values than the females. Seasonal and variations due to maturation of gonads were also apparent.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1979.tb03496.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

In an investigation into changes in the growth and biology of a stunted roach population, details are given of the methods of sampling and examination of the material. Studies on the growth of scales and opercula indicate that roach in all year classes formed a distinct annulus on both structures during May/June each year and fish in their second year of life also formed an additional check in the late summer/autumn of both 1969 and 1970. Reference is made to previously published descriptions of the particular difficulties, and their solutions, involved in aging stunted roach and evidence is cited for the validity of the methods used. Data on age distribution in the samples suggests that the 1966 year class was absent from the lake involved by late 1969 and that the 1965 and 1967 year classes were also very weak. Comparison is made with the results of other authors and the significance of the weak year classes is briefly discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1979.tb03497.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The head and jaw movements involved in capture, buccal manipulation, ingestion and rejection of prey were investigated using sequential photography of juvenile Atlantic salmon feeding in a simulated stream environment. The results are described and discussed and mouth breadth and gill raker spacing are proposed as morphometric limitations to the range of prey sizes available which remains constant at 0·06 · fish fork length (PFR).A recirculatory flume tank was used to study prey size selectivity behavior. Simplified downstream‐drifting prey items elicited a variety of responses depending on their physical size. One hundred percent of offered prey ofPFR0·025 were ingested, while 90 % of prey at PFR 0·051 and 100% of prey atPFR0·105 were rejected. It is demonstrated that fish show negative selection for prey sizes smaller thanPFR0·025 and that prey of this size elicits maximum growth response.The validity of the proposed morphometric limitations on the available prey sizes is demonstrated by reference to selectivity behaviour and prey size related differential

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1979.tb03498.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The acute effects of a herbicide based on 2,4‐D on embryos and larvae of bleak,Alburnus alburnusL. exposed to concentrations of 25–3200 mg 1−1for 12–48 hours were investigated. The 2,4‐D delayed or stopped the development of embryos in their early stages, caused behavioural changes and morphological alterations. The L.C.50values for embryos varied between 12–9 and 15·9–4mg 1−1and for larvae from 51·6 to 111·2mg 1−1according to the time of exposure. The level of 2,4‐D in Lake Balaton, or similar shallow lakes, without substantial injury of the littoral fish fauna should not

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1979.tb03499.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Eggs of the blue whiting,Micromesistius poutassouwere artificially fertilised and incubated at a range of temperatures; larvae were reared for 8½ days after hatching. The development of the eggs and early larvae is described and contrasted with previously published descriptions. The relationship between incubation temperature,t, and development time,dt, is described by the Bělehrádek equationdt=a(t‐a)b. The rate of embryonic development increased with increasing temperature, the time from fertilisation to hatching decreasing from 205 h at 6° C to 70 h at 15° C. No eggs survived to hatch at incubation temperatures above 14·5° C while at 6·2° C and below embryonic development was still proceeding when the experiment was terminated. The optimal survival rate (about 70%) was achieved between 6° and 10° C. Lengths of larvae at hatching were between 2·29 and 3·17 mm, those incubated at the higher temperatures being at a more advanced stage of ontogenetic development. The growth rate of yolk‐sac larvae declined from 10% per day immediately after hatching, to less than 1 % per day 7 days later when the yolk‐sac was fully absorbed. Egg diameter varied between 0·99 mm and 1·15 mm when fresh. During development eggs were initially bu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1979.tb03500.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY