摘要:

The amount of fat and protein used by youngTilapia rendalliduring starvation can be quantitatively assessed and correlated to the condition of the fish. It was shown that fish in good condition used fat in preference to protein during catabolism, irrespective of the time period of starvation, but this rapidly reversed as condition declined and fish in medium and poor condition utilised more protein than fat to maintain routine metabolism. The amount of energy required during routine metabolism was not affected by the ratio of fat to protein used and a mean energy requirement for these fish (varying between 40 and 60 g in mass) was estimated as 45.03 J g‐1d‐1at 23°C. This estimate of routine metabolic energy requirement can be equated to oxygen consumption using an oxy‐energy coefficient of 13.68 J m

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb03407.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Phenol (C6H5OH) at non‐lethal concentrations in hard water had no effect on the urine flow rate or haematocrit of rainbow trout for exposure times of 24 h. Phenol was detected in the urine in a non‐conjugated form and unchanged phenol was also extracted from muscle, blood and brain. Uptake of phenol into tissue was found to be rapid with an equilibrium concentration being reached in 3 h. Loss of phenol after exposure was as rapid. The equilibrium concentration for muscle was similar to the phenol concentration to which the fish were exposed. Blood and brain contained smaller amounts. Close to or above the lethal threshold concentration (48‐h lc509 mg 1‐l; 15°C) the fish had higher than ambient concentrations in their tissues most notably in the brain. Above the lethal threshold there is evidence of a large uptake of phenol by eryt

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb03408.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Infections of roach (Rutilis rutilus), and rudd (Scardinius erythrophthalmus), by the eyeflukesDiplostomun spathaceumandTylodelphys clavatawere studied in a lake over a three year period.T. clavatafirst appeared at the beginning of the study. Roach were heavily infected by both parasites, whereas the rudd contained very few specimens of either species. A small number of roach‐rudd hybrids were also examined, and appeared to have a susceptibility intermediate between the parental types.Levels ofT. clavatain roach increased throughout the study. This parasite had a life span of a year or less in the fish, and was continuously lost from the population. This loss was balanced by a minor infection period in April/May and a major one extending from August until January. The fish continued to accumulate infections until they reached a size of about 130 mm, but thereafter intensity fluctuated about the level reached.D. spathaceuminfections similarly increased throughout the period of study, and there was a suggestion of a wave of infection in the spring. This parasite has a much longer life span, and levels of infection increased with fish size, only falling in the largest, and therefore oldest, hosts.The major changes in the parasite populations in the roach were reflected, to a lesser extent, in the rudd. Both species were over‐dispersed, but the data from roach was too heterogeneous to fit to any theoretical models, whereas that from the rudd was found to conform to a Negative Binomial distribut

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb03409.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Comparisons based upon morphological features and cytochemical staining properties of chromatin, nucleoli, and the ooplasm were used in the present analysis of ovarian maturation in wild‐caughtPoecilia mexicanaand its related gynogenetic diploid and triploid' species'. Using an empirically derived ovarian maturation index, seasonal and collection site differences were found between the unisexual and bisexual forms. These fish seem equally suited to their environments. However, our data indicate that differences in microhabitat can have a profound influence on oocyte development. Although females ofPoeciliaspp. have asynchronous cycles of ovarian maturation, we could not detect any peculiar cytological events associated with the gynogenetic mode of reproduction. Sperm were found in ovaries of both unisexual and bisexual forms indicating that the unisexuals can compete effectively with females of P.mexicanafor matings with males of this species. The methods employed in this study provide a sensitive measure of reproductive potentials in sympatric specie

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb03410.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Tilapia mossambica (Sarotherodon mossambicus(Trewavas, 1973)) a female mouthbreeding cichlid, Fryer&Iles (1972), has recently been introduced to the Fish and Aquaculture Research Station, Dor, from South Africa. They were found to spawn freely in aquaria. Females carrying eggs in their mouth are routinely transferred to small containers, and when the fry are released they are separated from their mothers.In one batch of 209 fry we found two fry connected at their ventral part to the same yolk sack. These' Siamese‐twins' survived for 8 days in an aerated glass jar. During this period the yolk sack was absorbed and they became connected at their abdomens. (Plate I). Similar cases were previously noted in sharks, trout, Salmonidae spp., guppy, Poecilia sp. and Haplochromis sp. (Reichenbach‐Klinke&Elkan (1972) and Reichenbach‐Klinke (1

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb03411.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

A sex pheromone of the zebrafish,Bracliydanio rerio, previously shown to attract conspecifics is here shown to repel a closely related species,B. albolineatus. The repellent action is considered as a possible population isolating device in these geographically and taxonomically closely related cyprinid fishes.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb03412.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

A total of 654 char,Salvelinus alpinus(L.), from Lake Bjellojaure, Sweden, were examined for plerocercoids ofDiphyllobothrium dendriticum(Nitzsch, 1824) andD. ditremum(Creplin, 1825) from September 1969 to December 1974. Plankton samples showed that the dominating copepod species in the lake wereEudiaptomus graciloides(Lilljeborg),Cyclops scutiferSars andHeterocope appendiculataSars.E. graciloidespassed the winter as adults andC. scutiferas copepodids whileH. appendiculatawas restricted to a short period in the summer. Copepods occurred in the stomachs in September‐October and to a certain extent in April‐May, but only cyclopids andHeterocopesp. were found.C. scutiferis proposed to be the main first intermediate host of bothD. dendriticumandD. ditremum. The potential final hosts were thecommon gull,Larus canusL., forD. dendriticumand the black‐throated diver,Gavia arctica(L.), forD. ditremum. One common gull was experimentally successfully infected with plerocercoids ofD. dendriticum. The parasites showed no seasonal cycle in incidence of infe

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb03413.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The addition of up to 8.5 % sodium chloride to the diet of rainbow troutSalmo gairdnerihad no significant effect on either food intake or food conversion efficiency. Over a range of rations from 4 % to 38 % of dry weight per week, there was a rectilinear relationship between ration and growth rate. The weight maintenance requirement and rate of weight loss during fasting were estimated from this relationship. Food conversion efficiency (K) increased from 0.00 at 4% dry weight per week food intake (x) to 0.19 at 38%, according to the equationK=0.21‐0.77/

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb03414.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Zebra Danio (Brachydanio rerio, Hamilton‐Buchanan) tropical fish are easily maintained and bred under laboratory conditions; procedures for maintenance and breeding are described. Intensive inbreeding of this fish gave rise to a high incidence of spontaneous skeletal deformities which appear to reflect a genetic defect rather than an environmental stimulus. This finding casts doubt on the suitability of the Zebra Danio for fish toxicity testin

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb03415.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Individual haddock,Melanogrammus aeglefinus(L.) were maintained at different feeding levels in an aquarium from November until the completion of spawning. The mean duration of spawning was 33.2 days (range 19–59) during which an average of 16.6 (range 10–25) batches of eggs were produced. The size and dry weight of the eggs declined during the spawning period. Egg production and feeding level were correlated positively. There was some suggestion that when female haddock received low rations (13 kcal day‐1). The relation between daily growth in wet weight, g, and daily surplus energy intake, kcal, was:G=(0.295E)— 0.328. When food energy is restricted, haddock appear to achieve a balance between somatic growth and rep

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1978.tb03416.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY