摘要:

The validity of the use of the weight of dried eye lenses as an indicator of age in the common carp,Cyprinus carpioL., is tested. There is a significant difference between males and females for fish of two and three years old. Otherwise no significant difference is noted between sexes. The linear relationship between the dry weight of eye lenses and age + 1 are: InY+ 1= 0.5202 + 16.4928X(r= 0.93) for female and lnY+ 1=0.4276 + 16.7364X(r= 0.94) for male.The method for determining age is valuable for fish until three years old. However for older fish, in spite of a correlation coefficient between lens weight and age and even with a significant difference between annual groups, the age determination may be misleading due to the overlap in lens weights. In conclusion therefore this method may not be useful for back calculation of growth, for production estimates or studies in which accurate estimates of age are needed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03726.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

The seasonal development of the testes in European pike was examined using wild fish and biopsies from pike housed in tanks. The size of the tubules and the different cell types were measured and their histological appearance described. Four stages of development can be distinguished during the annual cycle. They are: (I) the stage of rest from June to August; (II) the stage of development from September to November with intensive spermatogenesis; (III) the stage of maturity from December to March/April with spermatogenesis completed; and (IV) the post‐spawning stage from March to Ma

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03727.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Samples of perch,Perca fluviatilis, were examined for the contents of their gastrointestinal tract and for the intestinal nematodeCamallanus lacustris(Zoega). The seasonal dynamics, dispersal pattern and site preference of the nematode were studied. Both larvae and adult worms were present in the perch throughout the year. The abundance ofC. lacustriswas non‐seasonal, but seasonal cycles were found in the numbers of larvae and of gravid females.C. lacustrisshowed a tendency to an increase in mean intensity with the size of perch. The frequency distribution of the nematode followed the negative binomial at different times of the year and in different length groups of perch.C. lacustrisshowed a seasonal site preference in the perch gu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03728.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

A detailed study was made of the seasonal changes in energy reserves in adult female plaice,Pleuronectes platessaL. The weights of lipid, protein, glycogen and ash in the carcass, liver and ovaries were measured in females approximately 35 cm long on ten occasions during one year. These data were converted to data for a‘real’growing female by using a growth curve to take account of increasing length during the year. Growth of the whole body and of the body components was assumed to be isometric.Plaice show a marked seasonal cycle of body weight and energy content. A six year old female plaice of 330 g, 32.6 cm long and with an energy content of 406 kcal in May, assimilates 560 kcal before December when it ceases to feed. Of this, 234 kcal is used to produce eggs, 159 kcal is used for metabolism during starvation, and the remainder 167 kcal, is used in growth. There is an increase in length to 35.9 cm and in weight to 462 g over the year. From December until March, when plaice do not feed but grow large ovaries, 40% of the protein in the body is utilised, 33% is devoted to egg production and 7% is metabolised to provide energy; 64% of the lipid is used, only 14% being used for egg production but 50% is metabolised for energy. Lipid supplies 75% of the energy for metabolism and so forms the major reserve; 42% of the energy assimilated during the year is devoted to reproduction. The main source of lipid and protein reserves is the carc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03729.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

This paper presents data on the reproductive biology ofLiza subviridis, a little studied mullet species. The fish is heterosexual, exhibiting external fertilization. Six maturity stages can be macroscopically identified in the testes and seven in the ovaries. The macroscopic changes in the gonads are manifestations of histological changes occurring in the development of sperm cells and oocytes. First sexual maturity is attained in the length ranges of 9.5–11.5 cm and 10.5–11.5 cm in male and female fish respectively. The fecundity for fish measuring 10.3–13.9 cm in standard length ranged from 40 000–145 000 eggs. The relationship between fecundity (F) and length (L) can be represented as:F= 1.9044L4.2998. The spawning duration inL. subviridisis restricted to a short and definite period, with all ripe ova being released within a single spawning act. A pronounced spawning season can be detected to extend from June to November. However, during off‐seasons, some spawning also occurs. The correlations between spawning, rainfall and air temperature is

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03730.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

The Kafue Floodplain fishery produces an annual fish yield of about 5000 tonnes. The 1971 closure of the Kafue Gorge Dam downstream from the floodplain modified flooding patterns. Pre‐impoundment studies predicted this modification would increase fish stocks. Experimental gillnets set in 1975 and 1976 caught 18 species on a regular basis, nine of which were abundant enough for comparison with catches in similar gillnet samples taken prior to completion of the Kafue Gorge Dam. Of these nine species, experimental gillnet catches of three predator species were smaller in 1975–76 than in 1969–70. Catches of only one species increased significantly. Whether this change is due to the modified flooding pattern is unclear; unusually dry flood conditions in 1973 and increased fishing effort may have contri

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03731.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

A progressive fall in serum thyroid hormone levels was found in Lake Ontario coho salmon,Oncorhynchus kisutch, between May 1978 and January 1979 concomitant with an increase in goitre frequency and thyroid hyperplasia. Despite marked differences in overt goitre frequency in sexually mature adult salmon collected from Lakes Ontario (43.7%), Erie (93.5%), or Michigan (0%), serum thyroid hormone levels and thyroid histology were similar in fish from the three lakes. Two gonadotrop‐like basophil cells (‘globular’and‘vacuolar’) were found in the pituitary, particularly in sexually maturing and mature adults and‘jacks’. Whereas in salmon from Lakes Ontario or Michigan, the globular cells were vacuolated in Lake Erie salmon they were not; this observation may be correlated with the absence of obvious secondary sexual characteristics in Lake Erie salmon. Serum free fatty acids serum, triglycerides and cholesterol concentrations in Lake Ontario salmon fell progressively from the condition in fish collected from the Lake in May 1978, to that of fish collected during their potamodrous migration in November 1978 and

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03732.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

This is the first report of a specimen of the family Lutjanidae,L. argentiventris(Peters), in which the pelvic fins are abnormally absent.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03733.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Salmon eggs and unfed fry were planted in reaches (total length 2.8 km, mean width 4 m) of a Scottish stream between 1971 and 1977 and their subsequent progress was studied by sampling 16 sections (areas 38–126 m2) of the stream. Brown trout are the only fish which spawn in the stream, waterfalls and a dam near its mouth preventing adult salmon and sea‐trout passing upstream. There were no restraints on the downstream movement of fish except in 1977, when a fry trap was operated. In 1971 and 1974 boxes each containing 300 eggs were buried in groups of 3–6. In other years fry were evenly distributed at 3.6–29.3 m−2. At the end of the first growing season, salmon occurred at decreasing population densities for a distance of 600 m below the plantings, but after two growing seasons there was little remaining indication of their pattern of dispersion when planted. Rates of survival between planting and the end of the growing season were 9.4–31%. Survival when eggs were planted (11.1–14.8%) was not affected by the numbers planted together at one point (900–1800) or the distance apart of groups of boxes (10–85 m). When fry were planted the instantaneous mortality rate (M) of the 0+salmon during their first growing season was related to the initial stocking density (Dp) by the formulaM= 0.00637 + 0.00444 log10Dp. Twenty‐two to 88% of 0+salmon present at the end of the growing season were still surviving in the stream as 1+fish one year later. In 1973–1976 only a small number of 2+salmon occurred, the majority having migrated between the end of the second growing season and the following spring. There were more 2+salmon in 1977 and 1978 resulting from higher stocking densities in 1975 and 1976 and slower growth. Trout of several age classes were present but their population densities were never high (<0.6 m−2). Salmon reached a greater size than trout by the end of the first growing season. Their mean weight (Wo, g) at this time was inversely related to their population density (DoNo. m−2) and the biomass (B1, g m−2) of 1+salmon present, giving the relationship log10wo= 0.6584–0.0558 D0‐0.0352B1. The mean weight of 1+salmon tended to be highest in sections where the 0+salmon had reached a relatively large size the previous year. When a reach of the stream was planted twice (11 and 30 May 1977) with salmon fry (total 13.9 m−2) at the same stage of development,Mduring the first growing season was 0.0099 per day. This was less than that of fry in a control (M= 0.0107) where the stocking density was lower (6.8 m−2) and also less than in previous years when single planting rates of approximately 14 m−2were used (M=0.0115). The double planting resulted in a wide range of lengths of 0+salmon in September and the highest biomass valu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03734.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY

摘要:

Fish toxicity of etho‐nonylphenol and of two non‐ionic antifoam agents was tested using rainbow trout,Sulmo guirdneri, in 24 h tests. The surface tension of these three compounds was found to depend on concentration and ageing time of the test solutions. The toxicity of the surfactant was about twice as high as known values, with a LC50of 8.5 mg/1 at 15°C. The addition of antifoam agents to the surfactant solutions further lowered the surface tension but did not alter substantially the fish toxicity of the surfactant. Contrary to expectation, the fish survived in concentrated antifoam solutions at surface tensions as low as 31 dyn/cm for more than 24 h without any apparent damage. The relevance of the surface tension regarding the fish toxicity of detergents in general is critically discu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1980.tb03735.x

出版商:Blackwell Publishing Ltd    

年代:1980

数据来源: WILEY