摘要:

One hundred femaleRaja naevusfrom the South Celtic Sea were examined every month for 14 consecutive months, for the characteristics of their ovarian cycle. Egg‐laying occupied more than half of the cycle. All females followed the same genital cycle but independently of each other. On the average 56% of adult females were at egg‐laying stage at any time throughout the year. Fecundity is estimated at 90 eggs a y

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb03943.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Livers of 38 channel catfish were studied by light and electron microscopy and the morphology of hepatocytes, endothelial cells, Kupffer cells, fat‐storing cells, macrophages, exocrine pancreatic cells, and epithelium of bile pre‐ductules and ducts was described, Hepatocytes contained large peri‐canalicular bodies which showed acid hydrolase activity. A comparison between catfish liver and that of other teleosts was made. The applicability of the findings to pathobiological studies of teleost liver is desc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb03944.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

The calorific value of the three‐spined stickleback,Gasterosteus aculeatus, varied with its size, sex and the season. Fish of 16 mg dry weight had a value of 1950 cal/g while for fish of 313 mg the value was 470 cal/g. The califoric value of gravid females was 23% above that of males of comparable size. The califoric value of a tropical cichlid,Tilapia nilotica, with a dry weight of 11 g was 4300 cal/g, the calorific values of the tissues ranged from 2500 cal/g for bone to 5190 cal/g for muscl

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb03945.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Hydrogen ion concentrations (pH) of the digestive tracts of channel catfish were determined for fish of two sizes (892 and 134 g average weight) at two environmental temperatures (28 and 23°C). Acidic conditions (pH 2–4) were present in the stomach contents of all catfish with slightly higher pH values in stomachs of fish at 28°C. The pH increased to slightly alkaline values (pH 7–9) in the duodenum and reached a maximum level (pH 8.6) in the upper intestinal region and then decreased in the lower segments to approach neutrality in the colon. The pH of the bile ranged from 6.1 to 7.5 and was higher in fish maintained at 28°C. Higher environmental temperatures (28°C) resulted in a slightly lower pH throughout the intestinal and colon segments. The larger catfish had lower intestinal length/body weight ratios than smaller catfish. As the result of distension due to increased food consumption, catfish maintained at 28°C had shorter intestinal tracts than catfish maintained

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb03946.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

The rate and level of arsenic accumulation in the liver of green sunfish is greater than that in the other organs examined. The level to which arsenic is concentrated is positively associated with the concentration of arsenic, in solution in the immediate environment of a fish, the duration of exposure to arsenic, and water temperature, Since it was found that accumulation causes histopathological changes, a study was made to examine the appearance of and rate of change in hepatocyte ultrastructure morphology following exposure to arsenic concentrations of 0, 30, or 60 ppm and after exposure times of one, two, or three weeks at 20°C. As arsenic concentration and exposure time increased, electron dense particles were observed, and the numbers of intranuclear and cytoplasmic electron dense particles and aberrant mitochondria increased. Also, lysosomes and smooth endoplasmic reticulum increased in number, while the number of myelin figures decreased

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb03947.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Most age and growth studies on brown trout in British lakes have been restricted to highland or moorland areas. In the unusual environment of a coastal dune lake (Loch of Strath‐beg, Aberdeenshire) the trout population was short‐lived with few fish surviving longer than three years. Growth was rapid compared with other naturally‐stocked lakes. Growth in length and weight differed between 1–and 2–migrants. Faster growth in the burn was the factor causing early migration by 1–migrants (71% of population), but both groups grew at the same rate on entering the loch. The effect of gill‐net selection on the estimation of the length‐weight relationship was demonstrated. A small difference was found in the length‐weight relationship among the mature stages. Factors responsible for rapid growth and small age‐range of the popul

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb03948.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

The host specificity ofLepeophtheirus pectoralis(Müller) was examined experimentally by exposing different fish species to infection by artificially reared copepodid larvae. Copepodids which were hatched from eggs of adults parasitic on plaice (platessaecopepodids) preferred plaice to all other fishes tested, whereas copepodids which were hatched from eggs of adults parasitic on flounder (flesicopepodids) preferred flounder to all other fish species. These behavioural differences suggest that two strains ofL. pectoralisexist, one (platessae) adapted to plaice as its host and the other (flesi) to flounder. Comparison of an experimentally derived order of host preference with a table of occurrence obtained from the literature, suggests that a third strain ofL. pectoralis, adapted to dab as its host, might also occur.The process of infection byL. pectoraliscopepodids is also described. It comprises a host location phase, during which the copepodid enters the habitat of its flatfish hosts and locates a host individual, and an attachment phase. The host location phase appears to be governed by changes in the activity of the copepodid and by its positively rheotactic response to water currents produced by the host. The attachment phase is probably based on the response of the copepodid to chemical factors produced by the host

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb03949.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Opercular bones from 399 chub from the River Stour, Dorset were used for age and backcalculated growth measurements. Scales were only used to aid the interpretation of difficult operculars. Annuli were laid down through the period mid‐April to mid‐June. Growth in length was minimal between October and March. Growth rates were similar to those published for chub in other European waters, but the Stour chub were longer‐lived and attained a greater ultimate size. Female chub grew faster than the males. Spawning occurred from late May into June and elaboration of the gonads took place between September and May. Immature chub had an annual cycle of condition; the 0 group having a maximum in August and older immature fish reaching their maximum in June. Both categories had a minimum condition in early spring. The cycle of gonad development affected the condition of mature fish. The numbers of eggs in chub of lengths 359–467 mm ranged from 27 000–65 000. Some females attained sexual maturity at age V or VI, but most by age VII. The majority of males matured at age V, though some at ages III or IV. Growth rates and year‐class strengths varied from year to year but independently of one another. Thirty‐one per cent of chub aged II and over belonged to the 1959 year class. Young chub ate insect larvae and small crustacea, but the occurrence of fish and macrophytes was greater in the diet

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1976.tb03950.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY