摘要:

A total of 206 river‐spawning whitefishCoregonus lavaretus(L.) from the Bothnian Bay was investigated for food objects and acanthocephalans in the years 1975–78. The only acanthocephalan species found wasMetechinorhynchus salmonis(Müller 1780), the total number of which was 1295.The whitefish is shown to be highly susceptible to infection byM. salmonis, with as many as 88·9% of specimens infected in a sample in June 1978, although the mean intensity was only 8·9 parasites per host. The river‐spawning whitefish does not favour the intermediate host,Pontoporeia affinis, in its summer diet in the Bothnian Bay preferring to feed on eggs and molluscs, so that the incidence ofM. salmonisinfection decreases to 33·3% by the middle of summer. This is further reduced in the late summer by the fast associated with the migration to their upriver spawning grounds. The fact that the other acanthocephalan inhabiting the river‐spawning whitefish in the southern Gulf of Bothnia,Echinorhynchus gadiMüller, 1776 is not to be found in the Bothnian Bay population suggests that the fish captured in spring have remained in the Bothnian Bay throughou

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb02736.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Fifteen steelhead trout,Salmo gairdneri, were assayed for selective blood parameters. The trout were reared under flow‐through conditions at the salmonid aquaculture facility at the University of Rhode Island. The means of the measured haematological parameters were: pH, 7·59 ± 0·05; pCO2, 8·5 ± 1·05 mmHg; HCO3‐, 11·9 ± 1·9 meq/1; Ferri‐Hb, 21·7 ± 2·0%; C1‐, 147 ± 17·8 me

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb02737.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Development of bimodality in the length frequency distributions of sibling juvenile Atlantic salmon,Salmo salarL., was observed in three experiments, using eight families in 25 tank populations. Divergence between the groups became evident in late summer or early autumn. The time of divergence, and the size offish at which this change took place differed between families.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb02738.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Rainbow trout,Salmo gairdneri, were experimentally infected withCryptobia salmositica. The parasitaemia was associated with increases in the size of the spleen, liver and heart (% body weight). The splenomegaly was pronounced and was often 600‐fold larger. The amounts of blood lactic acid and lactic dehydrogenase in the infected and control fish were similar. However, glycogen levels of the liver, heart and epaxial muscle declined. Liver glycogen levels were most affected and decreased to values which represented 20% of the control values. The pattern of the glycogen levels of the liver, heart and epaxial muscle declined to rise to normal values by day 56 post‐inoculation. Thus, the glycogen levels both paralleled the acute parasitaemia and the subsequent partial recovery of the infected fish as they tolerated a low chronic parasitae

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb02739.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Both red and white muscle were removed from juvenile and adult Atlantic mackerel,Scomber scombrusL., for histochemical characterization of the muscle fibre types. Staining of white muscle for myosin ATPase, SDH, NADH diaphorase, GPDH and LDH revealed that these fibres are homogeneous. Red muscle was shown to be heterogeneous, of at least two fibre types recognizable on the basis of myosin ATPase staining with preincubation at a pH of 9·8. These two red types are dispersed throughout the red muscle and are present in both juveniles and adults. Red muscle is located both deep within the myotomes and as a superficial layer of muscle fibres. A third group of muscle fibres, intermediate in nature, was distinguished at the apex of the red muscle ‘triangle,’ between the epaxial and hypaxial muscle, using NADH diaphorase and myosin ATPase stains. This paper discusses the possibility that functionally different muscle fibres occur in the red swimming muscle of the Atlantic mack

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb02740.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Layers of cells limiting the deep face of the dermis and lining the scale pockets can be described as endothelial, using the term in the broad sense. A dermal endothelium has been found in lampreys and in teleosts of diverse form and habits; it consists of a single layer of modified fibrocytes joined by desmosomal and other junctions and having hemidesmosomes and numerouscaveolae intracellulares. A fibrous zone interpreted as elastic tissue intervenes between the dermal endothelium and the collagen of thestratum compactum. The scale pocket lining consists of cells with caveolae, desmosomes, hemidesmosomes and usually with basement membrane. The lining may be one or two cells thick and may occur on both aspects of the scale pocket or only on the deeper side, depending on the species. The fine structure of these endothelial layers is compared with that of the vascular and lymphatic endothelia, the scale‐forming cells, the perineurium and the peritoneal linin

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb02741.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

The migratory behaviour of coho salmon was studied in the field. Coho salmon,Oncorhynchus kisutch, exposed to synthetic odours in a hatchery and released into Lake Michigan as juveniles, were recaptured as migrating adults 18 months later. The movements of 43 individuals were followed in experiments examining the role of imprinted chemical cues in the homing migration. Movements in relation to controlled distributions of the imprinting odours revealed that chemical cues are used by the salmon in their upstream migration. Acting with the rheotactic response, fish were guided upstream by imprinting odours simulating their home stream. Coho salmon, in the absence of their imprinting odour, respond negatively to the current. Differential responses to current appear to serve in segregating fish imprinted to odours of different home streams.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb02742.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Peripheral blood of trout contained two populations of red cells: those with polyribosomes located in the cytoplasm, and those without polyribosomes. Starvation of trout for 30 days was accompanied by a proportional decline of the polyribosomal‐containing (PRC) red cells. One week after a 15% bleeding of both fed and starved animals fed individuals showed a proportional decline of PRC red cells whilst starved fish showed a proportional increase of the same cell population. In fed individuals the bleeding response was accompanied by the appearance of many red cells with senescence‐related characteristics. PRC cells in both groups of animals were arbitrarily subdivided into three subgroups according to the density of polyribosomes present. No statistically demonstrable differences were evident between the means of the three PRC cell groups of control animals and those subjected to starvation and bleeding. However, there was an apparent rise in the proportion of red cells with the highest density of polyribosomes as a result of both treatme

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb02743.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

A direct comparison of plasma cortisol levels and mean nuclear diameter of adrenocortical cells in the same fish was carried out, to determine whether nuclear diameter could be used as a valid criterion of adrenocortical activity inCoregonus lavaretus(L.). Specimens were caught and killed by a variety of methods and at different seasons, providing a range of plasma cortisol concentrations, which were measured by gas‐liquid chromatography. The head‐kidneys of the same fish were immediately fixed and the diameters of 20 adrenocortical cell nuclei measured in 7 μm sections of each, prepared by strictly standardized methods. The correlation coefficient was 0·54, so that nuclear diameter cannot be regarded as an accurate criterion of adrenocortical act

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb02744.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

The biology of pike,Esox luciusL., in a southern productive lowland lake is described. Scales and opercular bones were difficult to read and interpret, and growth estimated had perforce to be based on scale readings. Growth of Slapton pike is average and intermediate between recorded extremes. Both male and female pike reached maximum condition in February, just prior to spawning. The population of pike of over 450 mm fork length in the lake was estimated at 870·6 ± 389·3 in 1975, and 950·4 ± 143.3 in 1976/77. This leads to the conclusion that the pike population has one of the highest biomasses per surface area of water ever recorded. Number of pike per unit area of surface was also high, despite the fact that a significant proportion of the population (fish under 450 mm) could not be adequately sampled. Mean instantaneous mortality rate was 0·53, and mean instantaneous survival rate was 0·59. The roach provided the main item of diet of the pike, with perch taken less readily. Immature pike ate a significant proportion of invertebrates, but roach was again a common feature of the diet of even small fish. Two spawning migrations were identified; at other times of the year, pike were non territorial. The majority of pike spawned in March. Fecundity of a sample of females was assessed. Overall sex ratio w

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb02745.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY