摘要:

The effects of season, stress, glucose loads and nutritional state on the plasma glucose (PG) and plasma fatty acids (PFA) ofLimanda limandawere examined. Plasma glucose levels showed no seasonal variation while PFA exhibited two peaks during May to August, and in December respectively. These peaks may be associated with resorption of gonadal material after spawning and the mobilization of lipid reserves for vitellogenesis.Limandashowed a hyperglycaemic response to a brief aerial emersion, followed by a hypoglycaemic condition. Infusion of a glucose load and the ingestion of a satiation meal ofMytilus edulistissue led to a reciprocal rise and fall of PG and PFA. Short‐term food deprivation had no effect upon PG although PFA rose significantl

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04910.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of a period of starvation and subsequent refeeding on the weight and length of rainbow trout at different times of the year has been investigated. Fish that have been starved for 3 weeks and then fed for 3 weeks show a weight gain equivalent to or greater than that of fish fed normally for the 6 week period, in four out of the five periods studied. The study provided evidence of the adaptation of the fish to starvation followed by what may be termed compensatory growth once feeding was resumed. The length changes of the fish indicate that the weight gains were due to growth rather than increases in gut fat deposits or increased water uptake.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04911.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

In five species of fish from the Family Sciaenidae, collected from marine, brackish and fresh‐water environments, the following parameters were studied: haemoglobin concentration, haematocrit, number of red blood cells, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, blood pH, oxygen affinity of blood and stripped haemolysate, Root effect, the number of haemoglobins separated by polyacrilamide electrophoresis, iron concentration and osmotic pressure of the serum.Plagioscion squamosissimus, the only freshwater species studied, clearly separated from the other four species; it exhibited the highest haemoglobin number, haemotocrit, number erythrocytes, of oxygen affinity of the haemolysate, and the lowest oxygen affinity of the blood, iron concentration, pH and osmotic pressur

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04912.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Changes in the size and composition of a population of the acanthocephalanAcanthocephalus clavulain eels,Anguilla anguilla, and flounders,Platichthys flesus, its definitive hosts, in a small river are described over a period of 4.5 years in the course of which the population underwent a steady and continuous decline. Parasite prevalence and abundance declined more rapidly initially and then more gradually, and during the period the frequency distribution changed from overdispersed to being close to random on most occasions. Throughout the whole period newly recruited parasites were found in eels, and adult females continued to mature and produce acanthors. Data on the distribution and occurrence of the intermediate hostAsellus meridianusin the river suggested that in the latter part of the decline it was no longer possible for the parasite to complete its life cycle in some parts of the river, and the cause of the parasite population decline is believed to be the decrease in abundance of the intermediate host as a result of interspecific competition with a congeneric species. During this latter period, immigration of infected eels from another river in the catchment may have contributed to the maintenance of the parasites in the locality, but it is considered that the decline in the river was representative of what was happening in other parts of the catchment and that the whole parasite population in the catchment was declining for the same reason.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04913.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The maturation development, spawning period, oogenesis, fecundity and sex ratio ofIlisha africanaoff the Lagos Coast, Nigeria were investigated. Six macroscopic and seven microscopic stages of gonad maturity were identified. Maturity was attained at 12.0 cm total length. Breeding occurred throughout the year with the peak spawning between May and December. Oogenesis consisted of seven stages and breeding marks were observed in the species. Fecundity ranged between 2098 and 11 687 eggs. There was a slightly higher correlation between fecundity and weight than between fecundity and length. The egg diameter varied from 0.77 to 1.35 mm. The overall sex ratio was 1 male to 0.97 female. The females however predominated over the males during most months in the peak breeding period.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04914.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Agglutinating antibodies to self spermatozoa were induced in mature male rainbow trout, whether immunised with autologous spermatozoa or allogeneic testis. Both sperm heads and flagellae appeared to be autoantigenic. These are the first results which show that fish can produce autoantibodies against spermatozoa. This is an important step towards the control of reproduction in fish using vaccines.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04915.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A new automated ultrasonic telemetry system for monitoring the swimming activity of adult rainbow trout,Salmo gairdneri, at liberty in the wild is described. The transmitter detects bioelectric potentials (i.e. electromyograms) associated with the contraction of the epaxial myomeres during swimming. Transmitter output is relayed to the signal processing system via submerged hydrophones. The incoming signals represent averaged electromyograms which have been shown in earlier studies to correlate well with swimming activity and concurrent oxygen consumption of rainbow trout in the laboratory.Electromyogram records obtained from rainbow trout released into a small lake and monitored for up to 4 weeks, indicate a fairly regular pattern of elevated midday activity contrasting with periods of relative quiescence during the evening and morning. This midday peak in locomotory activity is the result of an increased feeding activity which is evidently a response to a concomitant increase in the activity of the fish's prey.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04916.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effects of capture stress, exposure to a hypo‐osmotic environment and elevated water temperatures on the ascorbic acid (AsA) content of several mullet,Mugil cephalus, tissues were examined. All the treatments significantly altered tissue AsA levels, but the pattern of AsA fluctuations varied. Gill AsA concentrations increased two fold after exposure to a hypo‐osmotic medium (salinity changed from 30‰ to 5‰), whereas AsA content in this tissue declined after capture. Both treatments depleted AsA reserves in the kidney. AsA concentrations in the brain increased after exposure to low salinity and elevated water temperatures, but were unaffected by capture stress. None of the treatments caused long term alteration of hepatic AsA reserves. Ascorbic acid inhibited oubain‐sensitive Na+, K+‐ATPase activity of gill tissuein vitro. The results suggest an involvement of AsA in osmo‐ or ion‐regulatory functions of teleosts gills, salinity and thermal adaptation mechanisms in neural tissue, and the response of renal tissue to adverse enviro

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04917.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Fish were sampled by electrofishing at three contiguous sites 26 km from the source of Oued Sebaou, a seasonal river in North Algeria. River discharge ranges from 300 m3s−1in the peak of the rainy season to 0.1 m3s−1at the end of the dry season. Extensive gravel extraction from the river bed takes place during the dry season.Two species were recorded at each site:Barbus callensis, which is heavily fished locally, andAnguilla anguilla. The three sample maximum likelihood Zippin method was used to estimate mean density and standing crops, which were: barbel, 452 fish ha−1, 5.33 kg ha−1; eels, 149 fish ha−1, 3.04 kg ha−1. Estimated average biomass and production were: barbel, 2.31 kg ha−1, 4.27 kg ha−1year−1; eels, 1.51 kg ha−1,

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04918.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of food ration on larval lake whitefish,Coregonus clupeaformis, growth and survival was determined in the laboratory using brine shrimp as the test prey. In replicate experiments, larval whitefish were fed one of seven different rations of brine shrimp over a 25 day period. Statistically significant differences were found between larval growth and survival at each feeding level. Larvae fed to excess were 1.33 times as long and 2.80 times as heavy as those on the 1.8 zooplankton/fish (z/f) ration. No mortality was recorded until after day 15 of the experiment by which time all larvae had resorbed their yolk sac. Total mortality followed within 1 week for all feeding densities with the exception of the three highest (18 z/f, 32 z/f and excess rations) where total mortality equalled 90%, 12% and 0%, respectively.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04919.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY