摘要:

Both red and white muscle fibre numbers in juvenile Atlantic salmon increased gradually with fish length throughout the freshwater growth period. Mean fibre area increased as fish grew to 6.5 cmf.l., but thereafter was unrelated to fish length. Hyperplasia was most obvious when fish were growing fastest, and was the dominant growth process in fish over 6.5 cmf.l.Hypertrophy was most important when growth was slow, as in autumn and winter.Mean white fibre area was significantly smaller in deep muscle than at medial and superficial sites. Total cross‐sectional area of red, white and total trunk muscle increased with fish length. The ratio of red: white cross‐sectional area increased with fish length to a plateau at about 10% after 6.5 cm

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05884.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

In fry, 1‐ and 2‐year old juvenile Atlantic salmon, relatively small superficial red muscle fibres staining well for glycogen and succinic dehydrogenase (SDH) but with little myofibrillar ATPase, were evident on either side of the lateral line, in June. Well differentiated relatively large white fibres contained lower concentrations of glycogen than the red fibres, higher ATPase and no SDH, except traces in the larger 1‐ and 2‐year‐olds. Intermediate size pink fibres, which were also intermediate between red and white fibres in their staining properties, occurred in a thin diffuse layer along the red‐white boundary, thickest at the apex near the vertebral column, and most evident in the y

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05885.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The genomic DNAs of 1 1 species of percid fishes representing the five recognized North American genera are characterized using data from thermal denaturation assays. Base compositions were estimated from the transitional melting temperature of native and sonicated DNA and expressed as per cent guanine‐cytosine (%GC) values. Among genera, %GC values for native DNAs (c, 23,000 base pairs in length) range between 38.3% GC for yellow perch,Perca flavescens(Mitchill), to 43.2% GC for sauger,Stizostedion cunadense(Smith). Significant variation in %GC values was observed among surveyed genera of the subfamily Percinae, which includePerca, Percinu, Etheostoma and Ammocrypfa. Melting profiles were generated for each species, and distinct GC rich regions were identified within the genomes of walleye, Sfizostcdion virreum (Mitchill) and Etheostoma spp. Compositional heterogeneity (CH) and asymmetry values were calculated from melting profile data. Patterns of variation in genomic characters differed among the genera surveyed. Members of the speciose genusEtheostomushowed relatively little variation in genomic characters, whereasStizosredionexhibited significant interspecific variatio

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05886.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Populations of the estuarine glass fish,Ambassis vachelliRichardson, were used to study the relationship between somatic growth and widths of daily increments in the sagittal otoliths. Variations in the somatic growth ofA. vachelliwere induced by a series of experimental feeding regimes which included feeding to satiation with two food sources and a starvation treatment. After 33 days of exposure to the experimental feeding regimes significant differences in the mean wet weight of individuals amongst the feeding treatments were recorded. Fishes subject to a starvation treatment showed a significant reduction in wet weight compared to the pretreatment population and the two experimental feeding regimes. No changes in lengths of fishes were recorded.Validation techniques revealed that daily increments were laid down in the sagittal and asteriscal otoliths. Estimates of ring widths from samples of sagittal otoliths revealed significant treatment effects. The increments of fishes from the starvation treatment showed a significant decline in mean increment width relative to the feeding treatments. This difference was detected only after a 15 day period of experimental feeding. It is suggested that the gradual decline in increment width reflects the exhaustion of readily mobilized energy reserves.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05887.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A new method for the preparation of fish chromosomes from abdominal cavity fluid has been developed. Cells were collected from fish abdominal cavity fluid after an in vivo PHA treatment, and cultured for a short time in medium with colchicine. After 30 min hypotonic treatment for marine fish and 35 min for freshwater fish, slides were prepared by the conventional air‐drying method. The advantages ofthe method are: (1) it is technically simple; (2) it produces a reasonably high mitotic index; (3) chromosome spreading is good (4) there is very little cell breakage. Using this method, the chromosomes ofrainbow trout (2n=62); cod (2n=4546) and plaice (2n=46,47 and 48) were investigate

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05888.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Improved methods for obtaining, preparing, and staining fish chromosomes are described. Included are procedures for resolving serial or G‐type bands. A brief review of various metaphase banding procedures and their use in fishes is also presente

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05889.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The susceptibility and resistance of hatchery‐reared salmon parr, native to the rivers Neva (U.S.S.R. Baltic Sea), Alta (northern Norway) and Lone (western Norway) (both eastern Atlantic Ocean), toGyrodactylus salarisfrom Norway, was examined. The level of resistance to the parasite was assessed from counts, made on anaesthetized salmon, ofthe numbers of G.salarisafter an initial experimental exposure (2 weeks) to G. salaris‐infected salmon. Three experiments, all in water at c. 12° C, were carried out: (1) 50 Alta and 50 Neva salmon, initial mean parasite intensity c. 12; (2) 50 Lone and 50 Neva salmon, initial mean parasite intensity c. 60; (3) 10 Lone and 10 Neva salmon individually isolated, initial intensity one gravid G.salaris. In both the Norwegian salmon stocks, the G. salaris infrapopulations steadily increased during the experimental period of 5 weeks, in contrast to a prominent decline in the Neva salmon stock, after, respectively: (Exp. 1) week 3, average peak intensity 32.6; (Exp. 2) week 2, average peak intensity 58.7; and (Exp. 3) week 3, average peak intensity 6.3. The hatchery‐reared Baltic Neva stock demonstrated both an innate and an acquired resistance towards G.salaris, in contrast to the highly susceptible, Norwegian Alta and Lone salmon

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05890.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Lunar synchronization of spawning was investigated for eight substrate brooding cichlid fishes belonging to the tribe Lamprologini. Their spawning activities all peaked during the second quarter of the lunar cycle. Comparison between their breeding styles and the degrees of spawning synchronization suggested that the nocturnal guarding‐efficiency of eggs, especially exposed ones, is improved by the maximal amount of moonlight during full moon and, in species whose young leave the breeding sites about 2 weeks after spawning, the survival of dispersing young is enhanced by the darkness of moonless night

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05891.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Fry ofOncorliynclius mykisswere experimentally infected with the ectoparasites Gyroducrylus rolenirmensis andGyroducrylus salnionis(Monogenea) and changes in mucous cell density in the epidermis covering the caudal fin were monitored during an ensuing 42 day epidemic. At 10° C, infections of G.colemanensisrose to a recorded peak of 90 to 1 15 worms on day 27 post‐infection and then declined toward extinction. Intensity of G.salmonisremained low throughout the experiment. Infection produced no clinical signs of disease and did not influence fry growth or survival. However, infected fish did have a 50% reduction in the number of mucous cells in the epidermis of the fin. The changes were first detected on day 24 post‐infection and became increasingly pronounced during the subsequent 1 day period when parasite numbers declined drastically. The study hypothesizes that parasite activity on the surface indirectly leads to reduction in mucous cells through disruption of cell dynamics within the epide

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05892.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A ten‐year study of the population dynamics of the sea‐snail,Liparis lipuris, in the Bristol Channel, England is reported. This small fish which only lives for 1 year undertakes a regular seasonal migration from birth in marine waters into the estuary from which it retreats during the winter to return to the spawning grounds by early spring. At Hinkley Point, Somerset (salinity 22–3O%), abundance has been shown to be negatively correlated with water temperature presumably because of the avoidance of warmer inshore waters during mild winters. When the temperature effect is removed from the data the peak winter abundance of the population was found to have a coefficient of variation of only 27%. For a population which only comprises of age group individuals, this shows a remarkable stability. No statistically significant relationship was found between the abundance of sea‐snail and either their predators or prey. However, there were indications of a negative relationship with the abundance of whiting,Merlangius merlangus, which was the most abundant predator. We conclude that the population of a short‐lived marine fish living within a physically variable marine environment can be constrained within tight limits. Further. sea‐snail reproductive success has been independent of variation in local physical

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1990.tb05893.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY