摘要:

Yellowfin bream,Acanthopagrus australis, support an important angling fishery in Moreton Bay, a large estuarine system on the east coast of Australia. An analysis of the records of catches by anglers indicates that abundance and mean size of yellowfin bream have changed little in Moreton Bay during the period 1945 to 1980. Over the past 5 years substantial increases have occurred in the total angling effort for yellowfin bream at surf bar spawning areas in Moreton Bay. This has resulted in a decrease in mean catch per unit effort but no apparent decrease in total yield. Reclamation and development projects which cause degradation of the surf bar spawning areas have the greatest potential to cause reduction in abundance of yellowfin bream in Moreton Bay.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb04732.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The tambaqui,Colossoma macropomum, is the most important fish landed at Manaus by the fishery in the Amazonas State, Brazil. Population parameters have been estimated for this stock, which are: L∞= 107·3 cm (t.l.), W∞=32 kg, AT=0·227 year‐1, M=0·45 year‐1. A yield per recruit analysis shows that the stock is underexploited for values of M bigger than 0

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb04733.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The anatomy and enzyme histœhemistry of the œsophagus of a freshwater teleost perch (Perca fluviatilisL.) has been studied. The mucosa is composed of an undifferentiated layer of basal epithelial cells, mucous cells and surface epithelial cells. The submucosa is compact and contains blood vessels, nerves and bundles of striated longitudinal muscles. The outer circular muscular layer contains both striated and smooth muscle fibres. Electron microscopy shows that the surface epithelial cells are degenerative and that they surround and support pores of the mucous cells. Undifferentiated epithelial cells undergo cytoplasmic changes and eventually become surface epithelial cells. Mucous cells arise from the undifferentiated epithelial cells and their droplets contain acid and neutral mucosubstances. Alkaline phosphatase, non‐specific carboxylic esterases and aminopeptidase activity is absent in the mucosa. However, acid phosphatase activity is localized in the surface epithelial ce

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb04734.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The relationship between growth rate and fish size is described by the equation logeGw=a—0·4 logeW, where Gwis the specific growth rate and W is fish weight. Since the intercept (a) represents the logeGwof a fish unit size, the relationship presents a method allowing comparison of data from experiments involving fish of different sizes. The application of the method is demonstrated by examining the effects of environmental temperature on growth rates of cod,Gadus morhua, and it is suggested that the optimum temperature for growth of cod is 13–1

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb04735.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The cryopreservation methods for whitefish,Coregonus muksun, spermatozoa were studied using six different extenders with ‐40°C and ‐196°C as storing temperatures. In 1980, the spermatozoa of individual fishes were frozen in dry ice, in vials containing three different media based on glycerol as cryoprotectant. The pure glycerol media resulted in a 20% average rate of fertilization when samples were stored at — 40°C. The thawing procedure did not affect fertilization. In 1981, the sperm of individual fishes was frozen in pellets and stored in liquid nitrogen. Cryopreserved semen thawed in 0·119M NaHCO3produced 29·6–87·7% eyed eggs. The differences were caused mainly by the type of extender. The highest rate of fertility was obtained using an extender consisting of 0·3 M glucose with 20% glycerol (87·7% eyed eggs; 98·6% eyed eggs when compared to the corresponding control). The same values, using the modified extender of Stoss (Stoss&Refstie, in press), were 38·7–82·4% and, on the average, 90% eye

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb04736.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Free nucleotides, RNA, and DNA were extracted from fish white muscle and analysed by a two‐wavelength ultraviolet (UV) absorbance technique to determine their relation to growth rates in brook trout,Salvelinus fontinalis, and Atlantic salmon,Salmo salar. In the laboratory, fish given ample feed had higher growth rates than fish on restricted rations, and these growth rates were significantly correlated with RNA‐DNA ratios. Wild brook trout from natural streams had higher average RNA‐DNA ratios than those in the laboratory. Exposure of brook trout in one of the streams to low levels of the insecticide carbaryl (Sevin) that drifted from the spraying of nearby forests did not reduce RNA‐DNA

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb04737.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The occurrence and abundance of 17 species of Carangidae in Natal estuaries are described. The following six species are of significance in the estuarine community:Caranx ignobilis, C. melampygus, C. papuensis, C. sexfasciatus, Lichia amiaandScomberoides lysan. Only juveniles and subadults utilize estuaries. The time of recruitment, growth rates and feeding biology of the six species were investigated. Among the juveniles,C. ignobilisandC. sexfasciatusare mainly piscivorous on a variety of small estuarine fishes and estuarine dependent juveniles of marine species, whileC. melampygus, C. papuensisandS. lysanfilter feed on mysids and juvenile penaeids. Subadults of all species are piscivorous, althoughC. papuensisand S.lysanretain a suitable gill raker structure for filter feeding and a proportion of their diet consists of mysids and penaeids. The salinity and turbidity preferences of each species were investigated. All are euryhaline butC. melampygus, C. papuensisand 5.lysanare only found in clear water. It is suggested that the more widespread estuarine distribution of juvenileC. sexfasciatusandC. ignobilismay be related to their turbidity tolerances. The role of carangids in Natal estuaries is discussed in relation to their ecological significance in estuaries as predators and their degree of estuarine dependence.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb04738.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Trout fitted with dorsal aortic cannulae were subjected to 6 min of intensive exercise and monitored over the following 12 h recovery period. Delayed mortality was 40%; the majority of deaths occurred 4–8 h post‐exercise. Surviving fish exhibited a short‐lived haemoconcentration reflected in increased haematocrit, haemoglobin, plasma protein, Na+and Ch‐levels; an extended rise in plasma [K+]; a quickly corrected respiratory acidosis; and a more prolonged metabolic acidosis in concert with a rise in blood lactate. Dying fish exhibited very similar trends except for a significantly greater metabolic acidosis, lower plasma [Cl‐], and the apparent accumulation of an unknown anion in the blood prior to death. Cardiac failure did not occur. Blood metabolic acid levels, while elevated, were only ∼ 50% of peak lactate anion levels and well within the normal range of tolerance, as were all other changes observed in the blood of non‐survivors. The hypothesis that post‐exercise mortality is due to excessive ‘lactic acid’ accumulation in the blood is discounted. It is suggested that intracellular acidosis may be the proxi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb04739.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Samples of a wild population of the AnabantidTrichogaster pectoralis(Regan) were taken during and after one of the two main breeding periods of the year. Carcasses of both sexes and female gonads were analysed for fat, protein and carbohydrate. Carbohydrates were present in insignificant amounts in all tissues. The fat content of the ovary proved to be high (over 30% of wet weight) and, as a result, ovarian energy in a ripe female formed a substantial proportion of the total energy content of the fish. However, it did appear possible for females to develop large ovaries without depleting the carcass fat stores.Although protein levels in the carcass were significantly higher in 1 month, relative to fat levels, protein levels remained fairly constant during the period of study. Conversely fat levels showed marked fluctuations throughout the breeding period, being high at the start of the breeding period, low towards the end, finally rising again 1 month after most fish had terminated breeding. The range of fat levels appeared to be independent of the gonadal state of the fish at capture and seemed more closely related to month of capture. Two explanations are suggested; (1) changes in food availability over the period in question and/or (2) if repeated spawnings occur this could deplete fat reserves in the carcass.In this species fat is stored largely in the muscle but some is stored around the coiled intestine. A visual scoring system was used to assess the extent of this fat deposition and it was found that the fat score was correlated with the level of fat in the carcass. Thus the level of fat around the intestine, although insignificant relative to carcass fat, could be used as a method of assessing the fatness of a fish.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb04740.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The survival of Atlantic salmon smolts on exposure to constant concentrations of cyanide and ammonia, singly and together, has been measured under laboratory conditions at a concentration of 5 mgl‐1of carbon dioxide. The 24‐h LC50 values of cyanide and of un‐ionised ammonia, in fresh water, were 0·073 mg HCN l‐1and 0·20 mg NH3l‐1respectively at a concentration of dissolved oxygen of 10 mg l‐1, and 0·024 mg HCN l‐1and 0·08 mgNH3l‐1respectively at a concentration of dissolved oxygen of 3·5 mg l‐1. In 30% sea water the corresponding values were similar for cyanide but markedly higher for ammonioa. In 80% sea water the values were intermediate between those of fresh water and 30% sea water. Prior acclimation of the fish to the respective toxicant increased the resistance of the fish only slightly to cyanide, but with ammonia the 24‐h LC50 was increased between 1·4 and 2‐fold after acclimation for 1–3 days to between 0·2 and 0·5 of the 24‐h LC50 value. Mixtures of cyanide and ammonia were between 0·6 and 1·25 times as toxic as expected, ass

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb04741.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY