摘要:

Dietary sodium intake for freshwater salmonids feeding in the wild (invertebrate diet) or in captivity (pellet diet) was calculated and compared with published branchial sodium influx values. Dietary sodium intake (mmol kg−1per month) increases from winter minimum values of 5 and 30‐40 to reach maximum values in summer of 175 and 240 for invertebrate and pellet diet, respectively. In summer, dietary sodium intake for fish feeding in the wild was of the same magnitude as branchial sodium influx. The implications of dietary sodium intake for sodium balance in freshwater fish are discus

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03026.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The sand goby,Pomatoschistus minutus, was used in aquarium experiments to study the importance of body size for the ability of males to gain access to nest sites and mates. When several male and femaleP. minutuswere allowed to reproduce together, on average, half of the males built nests, and half of those males obtained eggs in their nests. Males with nests were significantly larger than males without nests, and nests with eggs belonged to males larger than the males with empty nests. In another experiment, when two males were competing for one nest, the largest male occupied the nest when both fish were put into the aquarium simultaneously. However, when the smaller male had been allowed to establish a nest before the larger male was introduced, the small male could usually retain the nest. Males with a body length<50 mm did not build nests at all in the early part of the breeding season. In female choice experiments, no preference for larger males was found. Thus, male‐male competition for nest sites and behavioural differences between different sized males seem to be the main factors influencing the non‐random mating success in maleP. minu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03027.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Year‐class strength in northern populations of smallmouth bass is strongly influenced by winter starvation of young‐of‐the‐year. We examined starvation among young bass under both winter and summer light and temperature conditions. During starvation, body condition declines to a specific level and then the fish dies. Body condition at death is a well defined function of body size that remains relatively constant over a wide range of environmental conditions. Starvation rate varies systematically with body size, temperature, pH and water hardness. Available stored energy increases more rapidly with body size than starvation rate. Therefore, lifetime under starvation conditions tends to increase with increasing body size. The Q10for starvation rate over the temperature range 2.5‐8° C is 2.2. Starvation rate increases as pH declines from 7.0‐4.9: the rate at pH 4.9 is ∼ 1.25 times the rate at pH 7 Starvation rate decreases as Ca concentration increases from 1 mgl−1to 80mgl−1: the rate at 80 mg Ca 1−1is ∼0.80 tim

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03028.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Natural infections of rainbow trout with two species ofDiphyllobothriumresult in a host inflammatory response encapsulating the plerocercoid. The encapsulating cyst, observed by light and electron microscopy, comprises leucocytes, fibroblasts and collagenous connective tissue and is infiltrated with a blood vascular network. An indirect immunofluorescence technique and enzyme‐linked immunosorbant assay (ELISA) have shown that specific antibodies are elicited by the fish host to theseDiphyllobothriumspp. These antibodies have been semi‐quantitatively measured by ELISA and correlated with worm burdens in individual f

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03029.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The effects of grouping on the growth and some components of the energy budget of the minnow,Phoxinus phoxinus(L.), were tested in the laboratory. No effects of grouping were detected on absorption efficiency, the proportion of food energy lost in nitrogenous excretion, maximum rate of food consumption and conversion efficiency. Grouping had no significant effect on either specific growth rate or the dry matter content of individual fish.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03030.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

With the aim of reliably distinguishing these commercially important species on the basis of external characteristics alone, morphometric techniques were employed on a sample of the four species ofOreochromis(Nyasalapia) described from Lake Malawi:O. karongae, O. lidole, O. sakaandO. squamipinnis. Univariate analysis of variance on the ratios of 23 variables to standard length indicated many differences among all species, but there was considerable individual variation, and consequent overlap. Residuals from a regression of each variable on length were employed for multivariate analysis. Cluster analysis on the means of the residuals was used to construct a phenogram which formed the basis for denning a series of dichotomous discriminant analyses. In each discriminant analysis, variables were successively eliminated in the reverse order of the magnitude of their correlation with the discriminant function. The combination of variables producing 95% accuracy of classification was selected, and the discriminant function equations for each step calculated. Some further variables were eliminated by checking for redundancy through analysis of correlations. The resulting equations enableO. karongaeto be separated using eight measurements,O. lidoleusing 10, andO. sakaandO. squamipinnisto be distinguished by a combination of 13 measurements.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03031.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

To examine otolith resorption induced by anaerobic stress,45Ca‐prelabelled goldfish,Carassius auratus, were kept in oxygen‐deficient ambient water (O2<0.5 .1 1−1, 26° C) for 2 days and otoliths (asterisci) were analysed for45Ca retention. In a second experiment, fish were anaerobically stressed for 2 days, and then received a single intraperitoneal injection of45Ca. They were maintained under stress for one more day and killed to examine45Ca deposition in otoliths. Plasma was analysed for total and radioactive calcium. Otoliths (lapilli) were examined for stress‐induced check formation by scanning electron microscopy (SEM).Stress significantly reduced plasma calcium levels and the rate of calcium retention in otoliths, which was calculated from the45Ca specific activity of the plasma. On the other hand, the rate of calcium deposition in otoliths was the same in the stressed as in the control fish. SEM observation revealed that the applied stress resulted in a check formation in otoliths. These results indicate that a 48‐h stress of oxygen deficiency induces calcium resorption i

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03032.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The karyotypes of bester (the hybrid between great sturgeon and sterlet) in three generations do not differ in diploid chromosome number from parental species and are displaced towards the sterlet in numbers of bi‐ and uni‐armed chromosomes and chromosome arms. The variability of quantitative karyotypic parameters other than number of bi‐armed chromosomes increases considerably (double, on average) in F1and F2and declines to the level characteristic of the parental species in F3. The variability results mainly from aneuploidy in microchromosomes and the karyotypic variabilities of 3 to 6‐week‐old and 4 to 5‐month‐old fish are the same. The stabilization of the hybrid karyotype in the third generation is rather rapid and may reflect the formation of a breed. The degree of individual karyotypic variability estimated on the basis of the coefficient of variation is 2‐3 % for parameters other than the number of microchromosomes, for w

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03033.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Ripe unfertilized eggs derived from fish landed at two Icelandic ports were predominantly red and yellow‐red, but a small proportion were red‐purple. There was a significant difference between the frequencies of hues of eggs from the two landing places. During the phase of blastula formation, fertilized red‐purple eggs showed no discernible change in either hue or chroma. However, as the gastrula formed and covered the yolk, the chroma declined dramatically, although the hue remained unaltered. When the embryo formed, the chroma continued to decrease and the hue also began to change as the red‐purple pigment disappeared from the yolk and the orange‐yellow oil of the yolk became more visible.The most common plasma colouration in male fish collected at Hafnarfjordur and Husavik was red, but the observed hues covered 60% of the visible spectrum, ranging from green to purple. No significant differences between Hafnarfjordur and Husavik males in terms of hue or value were discerned, but there was a significant difference in chroma score. Female plasma hues were almost as variable as the males (spanning 45% of the visible spectrum) but centred in the green‐yellow zone. Plasma, subcutaneous jelly and skin colours were closely linked.Fish from the oceanic feeding grounds were all green in skin colour, whatever their age or sex; it is suggested that this colouration has a cryptic function in the near surface waters inhabited by

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03034.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Two stocks of brown trout employed in repopulating the rivers of Asturias (northern Spain) were morphologically and karyotypically analysed. Both stocks were significantly different. The foreign stock was less adequate for repopulation than the autochthonous stock.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1989.tb03035.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY