bluuebunny/crossref_metadata_2025 huggingface dataset:
Haematological and haematopoietic responses to starvation in an air‐breathing fish Channapunctatus Bloch
Authors: Mahajan C. L. , Dheer T. R.
Published: January 2006

Changes in haematological values (RBC numbers, haemoglobin content, haematocrit value, MCV, MCH, MCHC, TLC and DLC) based on weekly samples from a group of starved fish were investigated. After 8 weeks of starvation, the effects of restoration to a normal diet was evaluated. Parallel studies on haematopoietic tissues were also made. Changes in some biochemical values such as blood glucose, liver and muscle glycogen were also examined to correlate biochemical effects with those of haematological changes. Erythrocytes, thrombocytes and neutrophils were found to be most sensitive to starvation. The initial response to deprivation of food was an increase in RBCs and related values and in total leukocyte population. However, from week 5 onwards a sharp decline in these cell populations was noted. The leukocytes and thrombocytes showed a change parallel to RBC and the total leukocyte counts. However, neutrophils were observed to show a consistent increase throughout the starvation period. A blood glucose level below SOmglOOmh1 appeared critical in relation to blood cell population. Haematopoietic studies revealed that reticulocytes and mesomyelocytes were unable to keep pace with the changing peripheral blood picture. Other stages in development responded to the changes in the peripheral blood.
Growth studies with fish—overcoming the problems of size variation
Authors: Jobling M.
Published: January 2006

The relationship between growth rate and fish size is described by the equation logeGw=a—0·4 loge W, where Gw is the specific growth rate and W is fish weight. Since the intercept (a) represents the loge Gw of 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 13–15° C.
RNA‐DNA ratio as an index to growth in salmonid fishes in the laboratory and in streams contaminated by carbaryl
Authors: Wilder I. B. , Stanley J. G.
Published: January 2006

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 ratios.
The occurrence of Montagu's Sea Snail, Liparis montagui (Osteichthyes‐Scorpaeniformes‐Cyclopteridae) in the Bay of Biscay (Spain)
Authors: Matallanas J.
Published: January 2006

The capture of a specimen of Liparis montagui off S. Ciprian (NW Spain; lat. 43°42 N, long. 7°33W) at a depth of between 6 and 10 m, in June 1976 is reported.
The relation between stock size and progeny of Atlantic salmon, Salmo salar L., in a Scottish stream
Authors: Buck R. J. G. , Hay D. W.
Published: January 2006

Large variations in the number of female adult salmon spawning in the Girnock Burn each year (range 28–127) produced smaller variations each year (range 2900–5600) in the number of juvenile migrants. The relative constancy of the parr migrations was achieved by changes in their age composition. There may be no advantage in allowing ova deposition to exceed a level around 200 000 (3.4 m−2) in the Girnock Burn, which would give rise to an average of about 4000 juvenile migrants (0.07 m−2) per season. Large numbers of ova (up to 12.5 m−2) did not decrease the number of juvenile migrants.
The influence of cellulose filler on feeding, growth and utilization of protein and energy in rainbow trout, Salmo gairdnerii Richardson
Authors: Bromley P. J. , Adkins T. C.
Published: January 2006

A nutrient source was diluted with indigestible filler in the form of α‐cellulose. The trout compensated for up to 30% cellulose by increasing the total weight of food eaten, thereby stabilizing both nutrient intake and growth rate. The fish failed to compensate for levels of 40–50% cellulose and, despite evidence for an increase in the size of the stomach, nutrient intake was approximately halved. There was a slight reduction in food conversion efficiency and the growth rate declined accordingly. By contrast, faecal output rose considerably.
The food of the pollan, Coregonus autumnalis pollan Thompson, in Lough Neagh, Northern Ireland
Authors: Wilson J. P. F.
Published: January 2006

Stomach contents of pollan caught monthly throughout the year were examined. Stomach fullness was significantly correlated with water temperature. Adult pollan fed on bottom fauna, mainly chironomid larvae, in October‐March, chironomid pupae in April and on Daphnia spp. in May‐September. Immature (0+ and 1 +) fish also ate other cladocerans and copepods. While there is no evidence for selection of any benthic prey species, adult pollan appear to be highly selective feeders on Daphnia spp. in summer.
Changes in tissue adenylates and water content of bluegill, Lepomis macrochirus, exposed to copper
Authors: Heath A. G.
Published: January 2006

Bluegill were exposed to copper (2–0 mg/1−1 unfiltered) for 24, 48, 72 or 96 h at 24° C. This concentration approximated the 96 h LC20. Water content of liver increased 4–8% after 24 h exposure and muscle 4–6% by 48 h. These changes persisted throughout the 96 h experiments. Copper exposed fish exhibited decreases in muscle ATP, ADP, total adenylates, and energy charge by 48 h. There was a trend toward recovery of ATP with further exposure. Liver ATP of exposed fish was lower than controls at all intervals with the greatest difference evident at 48 h. No significant changes in brain adenylates were observed. Muscle and liver lactic acid was unchanged at 48 h exposure, therefore tissue hypoxia was not the cause of the adenylate changes. It was concluded that copper causes decreases in muscle and liver ATP several days before probable death of copper exposed fish and the changes seen are the result of dilution by increased tissue water, and the copper acting on certain cellular enzymes involved in detoxification and energy metabolism.
The haematology of triploid landlocked Atlantic salmon, Salmo solar L.
Authors: Benfey T. J. , Sutterlin A. M.
Published: January 2006

Triploid landlocked Atlantic salmon had a larger mean erythrocyte volume but lower erythrocyte count than diploids; the haematocrit was the same in diploids and triploids. Although the total blood haemoglobin content and the mean corpuscular haemoglobin concentration were lower in triploids than in diploids, the actual mean corpuscular haemoglobin content of triploid erythrocytes was higher than that of diploids. The increase in triploid mean erythrocyte volume was mainly due to an increase in cell length; there was only a minor increase in cell width and no increase in cell height. The nucleus of triploid erythrocytes occupied a greater percentage of the corpuscular volume than did the diploid nucleus. Mean cytoplasmic haemoglobin concentration was found to be the same for diploids and triploids when this was taken into account
Reduction of genetic variability in a hatchery stock of brown trout, Salmo trutta L.
Authors: Vuorinen J.
Published: January 2006

Enzyme gene variability in a lake‐dwelling brown trout, Salmo Irulla, population was compared with its hatchery derivative by starch gel electrophoresis. A loss of genetic variability was detected in the hatchery stock founded 16 years ago in comparison to the present day wild stock; of seven originally polymorphic loci (Aat‐4, Ck‐l, Gpi‐3, G3p‐2, Ldh‐1, Mclh‐2 and Pgm‐l) two, Gpi‐3 and Ldh‐1, had become monomorphic. The overall hetero‐zygosity was reduced by a third from 6–2% to 4–2%. A comparison between three successive hatchery cohorts indicates a distinction between stock heterogeneity. The decrease in genetic variability is probably attributable to small population size in the founding event with subsequent genetic drift and inadvertent selection during hatchery procedures.
Distribution and function of digestive tract chitinolytic enzymes in fish
Authors: Lindsay G. J. H.
Published: January 2006

The activity of chitinolytic enzymes in the stomach or foregut of 29 North European marine and freshwater fish were determined. No correlation with a chitin‐eating feeding habit was observed but species that were able to mechanically disrupt prey had low activity while species that ingest prey whole had high activity. The primary function of gastric chitinase in fish may be to chemically disrupt the chitinous envelope of prey.
Seasonal variations in growth, condition and gonads of Dormitator latifrons (Richardson) in the Chone River Basin, Ecuador
Authors: Chang B. D. , Navas W.
Published: January 2006

Growth in length, condition, and gonads of a food fish, Dormitator latifrons, were studied in the Chone River basin, Ecuador, in 1981. The river was bordered by floodplains in the upstream freshwater zone, and by mangrove swamps and shrimp farms in the downstream estuarine zone. The climate was marked by wet (January to April) and dry (May to December) seasons. During the dry season, an earth dam in the river prevented movement of water and fish between upstream and downstream zones. At the end of the dry season, most of the upstream floodplains were dry, and the main fish refuges were in downstream areas in deep pools in the river upstream. During the floods, fish migrated from downstream areas towards upstream floodplains. Growth rates and condition increased when water levels were high or salinity was low and decreased when water levels were low or salinity was high. Seasonal changes in gonads and abundance of juveniles indicated that reproduction occurred during the floods, but there was some reproduction in the dry season. Reproduction occurred in upstream and downstream zones and appeared to be stimulated by a complex of factors, including water levels, currents and salinity. The yield in flood plain sites was estimated as c. 115 kg ha−1 in 1981.
Preliminary studies on trypanospmes from the dogfish, Scyliorhinus canicula L.
Authors: Pulsford A.
Published: January 2006

In a sample of 83 dogfish, Scyliorhinus canicula, 30% were found to be infected with trypanosomes during the summer of 1981 at Plymouth. Infected fish were over 53.0 cm total length and slightly anaemic, reflected in a 4.6% reduction in circulating erythrocytes with a small (0.6%) increase in leucocytes. Individual differences in serum proteins did not correlate with infection, although spleens from infected fish showed lymphoid aggregations around blood vessels. Parasitaemias were consistently low, ranging between 1.5×l03 and 6.O×103ml−1. No dividing forms were found in the peripheral blood or lymphomyeloid tissues, although two size forms were found in the peripheral blood. The trypanosome, Trypanosoma scyllii, is described from living and stained preparations and has been successfully maintained in laboratory culture.
The effects of starvation upon protein turnover in red and white myotomal muscle of rainbow trout, Salmo gairdneri Richardson
Authors: Loughna P. T. , Goldspink G.
Published: January 2006

Protein synthesis rates of both red and white muscle were measured using a constant infusion technique in fed and starved rainbow trout over a period of 2 months. In both tissues, rates of protein synthesis fell during starvation although the fall was more rapid in white than in red muscle. The reduced rates of protein synthesis were correlated to a reduced level of RNA in the tissues and a lower rate of translation of the RNA present. Estimated rates for protein degradation in white muscle showed a marked initial increase but with more prolonged starvation the degradation rate become only slightly greater than that in the fed fish.
A biochemical method for distinguishing between the sexes of fishes by the presence of yolk protein in the blood
Authors: Craik J. C. A. , Harvey S. M.
Published: January 2006

A method is described by which the adult females of marine and freshwater teleosts can be distinguished by a biochemical test performed on a blood sample. The test depends on the measurement in the blood plasma of alkali‐labile protein‐linked phosphorus, a specific measure of yolk protein (vitellogenin). In vitellogenic females, values of 20–100 μg protein phosphorus ml plasma−1 are usually found, while in males, non‐vitellogenic females and immature fish of both sexes the value is <7.5 and usually <5 μg ml−1. At the appropriate season, most females can be positively identified. Good results can be obtained 2–3 months before spawning, and in some species for an undefined period after spawning. The advantages of this method over immunological techniques for the determination of vitellogenin, such as radioimmunoassay and immunoelectrophoresis, are the wide range of vertebrate species to which it can be applied, and its low cost. Its disadvantages are its lower sensitivity and the larger volume of plasma (0.5 ml) which must be used.
Polyploidy induced by hydrostatic pressure in rainbow trout, Salmo gairdneri Richardson
Authors: Lou Y. D. , Purdom C. E.
Published: January 2006

Triploid rainbow trout were produced by hydrostatic pressure applied to eggs 40 min after fertilization. Treatment for 10 min with or without exposure to 2% ether produced high hatching rates. Nuclear measurements from serial section of 40‐day‐old fry and from blood smears of 5‐month‐old juveniles showed that the proportion of triploid individuals was 80–90%. Ether treatment alone did not induce triploidy. Attempts to produce tetraploids by hydrostatic pressure treatment of eggs at 8 h after fertilization failed. Parallel results were also obtained with heat shock.
Fish health assessment: a preliminary report on the use of impression smears of skin mucus
Authors: Wechsler S. J.
Published: January 2006

Preliminary results from this study suggest that impression smears of the skin mucus of fish can be used to aid in the evaluation of the fish's health status. Nonstressed Lagodon rhomboides and Carassius auratus have numerous superficial epithelial cells, occasional lymphocytes and other mononuclear cells in their cutaneous mucus. Smears of these fish 24 h post‐stress had more cellular debris, micro‐organisms and erythrocytes when compared to those made pre‐stress. Components in the mucus of fish which recovered gradually became normal. Smears of fish, which died, had increasing amounts of debris and micro‐organisms. The use of this relatively nontraumatic technique may be a useful adjunct in monitoring fish health.
The effects of a settled industrial domestic sewage works effluent from percolating filters on the embryo viability and hatching success of rainbow trout, Salmo gairdneri Richardson
Authors: Fraser J. A. L. , Clark E. R.
Published: January 2006

The mortalities of washed and unwashed rainbow trout embryos exposed to Birmingham tap water, 50% and 100% settled effluent from filter beds has been compared. Differences in the hatching success between washed and unwashed embryos in the three treatments were also compared and the effect of saprophytic microbial growths assessed. There was a significant difference in mortality between washed embryos exposed to tap water (5%) and 50% effluent (12%) and 100% effluent (12%) when dissolved oxygen levels were maintained near 100% air saturation value. Mortalities of unwashed embryos were 4%, 26%, and 26% respectively for the three treatments. Hatching success of washed embryos was similar in the three treatments but unwashed embryos were significantly affected by the effluent treatments because of Sphaerotilus growths.
Intraspecific differences in thermal tolerance of Etheostoma spectabile (Agassiz) in constant versus fluctuating environments
Authors: Feminella J. W. , Matthews W. J.
Published: January 2006

The critical thermal maximum (CTM) of Etheostoma spectabile differed significantly among four populations whose habitats ranged from thermally constant to highly fluctuating conditions. Mean CTM of the population at the most fluctuating location was highest, populations in intermediate thermal environments were intermediate in thermal tolerance, and a population in a constant temperature spring run had thelowest CTM. The results support the view that thermal physiology can be evolutionarily labile within a species, and that changes respond to directional selection.
Some aspects of the reproductive biology of Acanthopagrus spp. (Family: Sparidae)
Authors: Abu‐Hakima R.
Published: January 2006

Changes in the seasonal development of the gonads in Acanthopagrus latus and A. cuvieri over an annual reproductive cycle are described. There is one major spawning period from January to March. Hermaphrodite A. latus and A. cuvieri constituted 5.8% and 5.7% of the total sample respectively. The histological changes in the ovary, testis and ovo‐testis in both species are described. Fecundity estimates for A. latus, 27.5–31.8 cm, ranged from 1 362 137 to 2 152 993, and estimates for A. cuvieri, 47.1–63.5 cm, ranged from 308 273 to 1 693 365.
The age, growth and diet of a freshwater population of the flounder, Platichthys flesus (L.), in southern England
Authors: Beaumont W. R. C. , Mann R. H. K.
Published: January 2006

Otoliths from 640 flounders from the River Frome, a chalk river in southern England, were used for age and growth studies together with length‐frequency data. Mean lengths at ages I–V were 89, 151, 225, 304 and 323 mm respectively; these are higher than have been reported for marine populations. All flounders caught were immature and, on reaching the sea, both sexes probably became sexually mature a year older than did the marine populations. Flounder diets in freshwater comprised largely aquatic insects, Mollusca and Crustacea but there were differences between large and small fish; seasonal changes in diet largely reflected prey availability. It is suggested that competition for food and space in estuaries between 0 group flounders have given rise to the migration into fresh water.
Some aspects of the reproductive biology of the clupeid Ilisha africana (Bloch) off the Lagos Coast, Nigeria
Authors: Marcus O. , Kusemiju K.
Published: January 2006

The maturation development, spawning period, oogenesis, fecundity and sex ratio of Ilisha africana off 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.
Effect of food abundance on larval lake whitefish, Coregonus clupeaformis Mitchill, growth and survival
Authors: Taylor W. W. , Freeberg M. H.
Published: January 2006

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.
Correlations of allele frequencies with physical and environmental variables for populations of largemouth bass, Micropterus salmoides (Lacepede)
Authors: Philipp D. P. , Childers W. F. , Whitt G. S.
Published: January 2006

Differences in the biochemical genetic structure of each of 90 populations of largemouth bass, Micropterus salmoides (Lacepede), were detected by vertical starch gel electrophoresis. The allele frequencies at each of 28 enzyme loci were tested for correlation with 24 physical and environmental variables determined for each body of water from which the populations were sampled. The allele frequencies at several loci (malate dehydrogenase‐B, isocitrate dehydrogenase‐B, superoxide dismutase‐A, and aspartate aminotransferase‐B) were highly significantly correlated (P≤0.000l) with several physical and environmental variables (latitude, heating degree‐days, cooling degree‐days, and the length of the growing season). These correlations are consistent with the hypothesis that allelic differences at specific enzyme loci can confer different degrees of fitness in different thermal environments. Additional laboratory and field studies will be required to determine the extent to which allelic variants at a given enzyme locus contribute to thermal tolerance and thermal preference of largemouth bass.
Growth variability in individually confined elvers, Anguilla anguilla (L.)
Authors: Wickins J. F.
Published: January 2006

Newly caught elvers Anguilla anguilla (L.) were individually confined, induced to feed and their survival and growth variability compared to those of similar elvers held communally in lowdensity populations. Similar trials were conducted with fast‐growing and slow‐growing older elvers that had been induced to feed while cultured communally. It was not difficult to induce feeding in newly caught elvers, nor did it appear necessary for elvers to be stimulated to feed by the presence of others. Isolation seemed to enhance growth variability in newly caught elvers.

In older elvers growth was generally depressed by isolation. Following a period of stress, e.g. weighing, small fish tended to grow more slowly than larger fish in the individual groups. This suggested some permanency of stunting; however, some markedly stunted fish taken from large populations showed remarkable recovery when isolated and exhibited very high instantaneous growth rates, over 6.5% day−1.
Estimates of daily food intake by an inshore population of Pleuronectes platessa L. off eastern Anglesey, North Wales
Authors: Basimi R. A. , Grove D. J.
Published: January 2006

A sequence of trawl surveys showed that the diet of plaice off eastern Anglesey was dominated by Abra alba in spring and summer, and by Pectinaria koreni in early spring and autumn. Plaice ate little food in winter. Despite the relatively small stomach in this species, plaice were able to achieve high rates of daily food intake during bouts of heavy feeding by rapidly transferring newly‐ingested prey items into the anterior intestine without full gastric digestion. Seasonal daily feeding rates (percentage body weight) varied between 5 and 10% for small fish (15–20 cm total length), 3 and 12% for medium fish (20–25 cm) and 2.8 and 4.4% for large fish (30–35 cm).
Chromosome characterization in Acestrorhynchinae and Cynopotaminae (Pisces, Characidae)
Authors: das Neves Falcão J. , Bertollo L. A. C.
Published: January 2006

The karyotypes of six species of Acestrorhynchinae (Acestrorhynchus alus, A. lacustris, Oligosarcus hepsetus, O. jenynsii, O. macrolepis and O. pinloi) and of one species of Cynopotaminae (Galeocharax knerii) were studied. The six Acestrorhynchinae species have 2n= 50, while Galeocharax knerii has 2n= 52 chromosomes. Some chromosomal characteristics were detected which permit establishing some karyotypic relationships among the different species investigated. Thus, among the Acestrorhynchinae, the four Oligosarcus species are relatively more related to one another than the two Acestrorhynchus species, at least with respect to the cytogenetic data considered. On the basis of the methods used, no sex chromosome heteromorphism was detected in the species for which a comparative study between male and female specimens was possible.
Cortisol can increase the susceptibility of brown trout, Salmo trutta L., to disease without reducing the white blood cell count
Authors: Pickering A. D. , Pottinger T. G.
Published: January 2006

Chronic elevation of plasma cortisol levels in the brown trout by means of slow‐release, intraperitoneal implants increased the susceptibility of the fish to disease. Elevation from a mean basal level of 1–4ng ml−1 to ∼10ngml−1 for a period of 2–4 weeks was sufficient to increase the mortality rate due to furunculosis, Saprolegnia infection and bacterial fin‐rot. This level of plasma cortisol is well within that capable of being produced by the fish under conditions of chronic stress. The increase in susceptibility to disease was not accompanied by a reduction in the number of circulating lymphocytes and it is suggested that under certain conditions chronically‐elevated cortisol levels may be more sensitive, predictive indicators of reduced disease‐resistance than are changes in blood cell counts.
The biology of the Indo‐Pacific squirrelfish, Sargocentron rubrum (Forsskål), a Suez Canal migrant to the eastern Mediterranean
Authors: Golani D. , Ben‐Tuvia A.
Published: January 2006

A biological study of the adult population of the Suez Canal migrant, the squirrelfish, Sargocentron rubrum, in the Mediterranean coast of Israel, was carried out between October 1979 and October 1980. Sargocentron rubrum in the Mediterranean has a short spawning season lasting from July to August. The estimated fecundity varied from 108 000 to 646 000 oocytes per mature female. The largest ripe oocytes reach a diameter of 200 μm. The ratio of males to females was found to be 1:2. Hyaline rings on otoliths were used for aging. Growth rate was obtained by back calculation and by using von Bertalanffy's equation. The results obtained from both methods were close, 94mm S.L. after 16 months, 125–127 mm after 28 months, 143 144mm after 40 months and 155 mm after 52 months. Age groups older than 4 years were not found in the present study. The descriptions of early stages of development were based on samples collected by dip and neuston nets along the Mediterranean coast of Israel.
Histopathology of some fish tumours from British waters, including an olfactory glioma in coalfish, Pottachius virens L.
Authors: Bucke D. , Feist S. W.
Published: January 2006

A selection of neoplasias in feral fish is described. It includes olfactory glioma in coalfish, Pollachius virens L.; nephroblastoma with metastases and polycystic kidneys in crucian carp, Carassius carassius; lymphosarcoma in roach, Rutilus rutilus, and bream, Abramis bratna; and stomato‐papilloma in eel, Anguilla anguilla. The olfactory glioma is one of a few recordings of a central nervous system‐derived tumour in teleosts. Although nephroblastoma is relatively common in fish, rarely have metastases been observed. The lymphosarcomas in roach and bream have not been recorded before in the British Isles, but now stomato‐papillomas in eel appear to be established at a low level.
Evaluation of Hydrodictyon reticulatum as protein source in feeds for Oreochromis (Tilapia) niloticus and Tilapia zillii
Authors: Appler H. N.
Published: January 2006

The green filamentous alga Hydrodictyon reticulatum was evaluated as a protein source in fish‐meal substituted diets for Oreochromis niloticus and Tilapia zillii fingerlings. The fingerlings were fed in duplicate groups each of six different diets for 50 days. Five of the diets contained 30% crude protein supplied by varying proportions of fish meal and H. reticulatum meal. The five diets were formulated to supply fishmeal protein: H. reticulatum meal protein ratios of 30:0 (diet 1), 15:5 (diet 2), 20:10 (diet 3); 15:15 (diet 4), 10:20 (diet 5) respectively. A sixth diet containing only 25% crude protein supplied entirely by H. reticulatum meal was also fed. The best growth and protein utilization was obtained at lower levels of H. reticulatum substitution for both species of fish. Carcass analysis revealed a decrease in lipid contents of the fishes with increasing levels of the alga in the diet.
The fecundity of the walleye pollock, Theragra chalcogramma (Pallas), spawning in Canadian waters
Authors: Mason J. C.
Published: January 2006

The ovaries of 113 walleye pollock from a resident stock in the Strait of Georgia, British Columbia were examined for determination of fecundity. Oocytes were sized and counted in 20 μm intervals of diameter. Without exception, ovaries contained a pronounced bimodal distribution of oocyte diameters with peaks at 100 and 400–600 μm. Oocytes ≥ 180 μm diameter were undergoing trophoplasmic growth leading to hydration. ‘Apparent’ fecundity is defined as the estimated number of yolked oocytes ≥ 180 μm diameter, regardless of potential resorbtion. Previous workers have not shown that significant resorbtion takes place in the post‐spawned ovary. Total oocyte complement (≥40μm diameter) was best expressed by a linear model where Ft= 33004 f.l.– 869627, where f.l. = fork length in cm and r= 0.86. Estimates of Ft, ranged from 117700 to 1394 100 oocytes ≥40μm. Age was weakly related to fecundity, reflecting large individual differences in annual growth after age 4 years. Apparent fecundity best suited a linear model where Fa= 23522 f.l.– 599713 and r= 0.91. Estimates of Fa fell within the range 58 379–1 151 527. Relative fecundity (eggs g−1) decreased over most of the length range encountered in the sample. The average‐sized female in Georgia Strait is twice as fecund as her counterparts in the north‐western Pacific Ocean, containing some 390 000 to 420 000 oocytes 7ge;180 μm diameter compared to about 200 000 oocytes in a north‐western female of comparable length.
Hormonal sex reversal of wild‐spawned tilapia in India
Authors: Macintosh D. J. , Varghese T. J. , Rao Satyanarayana G. P.
Published: January 2006

The effectiveness of methyltestosterone (MT) for sex reversal and growth promotion in Oreochromis mossambicus was studied in culture experiments in India. Wild‐spawned fry were treated with 30 μg MT g−1 diet for 30 or 60 days at two feeding levels (initially 20% or 10% of body weight daily). The fish were grown on for 66–96 days after the hormone treatment period in fertilized cement ponds without supplementary feeding. Tilapia treated with MT for 60 days attained an average weight of 29.0 g compared to 18.8 g for untreated fish reared under similar conditions. The percentage of males among the untreated tilapia was 58%, MT treatment for 30 days significantly increased this percentage at the higher feeding level (79% male), but not at the lower feeding level (51%). More than 90% of the tilapia in both 60 day MT treatment groups were male; 3% of all the fish reared showed an intersex condition. The experiments demonstrated that the anabolic and sex reversal effects of MT on tilapia are proportional to the duration of treatment and quantity of hormone administered. The possible application of monosex tilapia culture in tropical countries is noted.
Histology of the pituitary gland of the grey mullet, Mugil cephalus L.
Authors: Narayan A. , George K. C. , Diwan A. D.
Published: January 2006

The present communication deals with a histological study of the pituitary gland of the teleost fish Mugil cephalus, found in the estuarine waters of Cochin area. Six different cell types were identified in the pituitary gland on the basis of their grouping, distribution and staining properties. The prolactin and the TSH cells (thyroid stimulating hormone producing cells or thyrotrops) were identified in the rostral pars distalis and the ACTH cells (adrenocorticotropic hormone producing cells or corticotrops) in the interphase between the neurohypophysis and the rostral pars distalis. The STH cells (somatotropic hormone producing cells or somatotrops) and the gonadotropic cells were distinguished in the proximal pars distalis and the MSH cells (melanin stimulating hormone producing cells or melanotrops) in the pars intermedia.
Gastric emptying rate in Pleuronectes platessa L.
Authors: Basimi R. A. , Grove D. J.
Published: January 2006

X‐ray studies of gastric emptying of Pleuronectes platessa force‐fed a moist, artificial diet give the relationship:

image

where GET is gastric emptying time (h), S is meal size (g), W is body weight (g) and T is temperature (°C).

The corresponding gastric emptying curve is predicted to be:

image

where stomach contents (g net weight) are S0 at start and St at time th. Direct observations of residual stomach contents using serial slaughter are in close agreement with the predicted curve, save for small plaice (below 50 g body weight) which empty at only 50–60% of the rate found in larger fish.

The small effects of body weight on gastric emptying rate may reflect the relatively small role of the stomach [Volume (ml) = 0.024 body weight (g)] in digestion when compared with other flatfish.

The emptying curve established here can be used in field studies to estimate feeding rate on natural food items, provided fish greater than 50 g body weight are used and the energy density of the food is greater than 0.5 kcal/g wet weight. Smaller fish will have emptying rates which are only 30–60% of those found in larger fish; the change appears to be abrupt and corresponds to the size at which young plaice move offshore from their nursery grounds.
Digestive processes during the development of the roach, Rutilus rutilus L.
Authors: Hofer R. , Uddin A. Nasir
Published: January 2006

During development of the roach from larvae to adults relative gut length increases from 44 to 104% of the body length. Gut passage rate correlates with gut length, ranging from 2.25 h in larvae to 6.2 h in adults (at 20 ± 1°C). In controlled experiments (20°C, feeding on carp diet) tryptic activity of the gut content increases with the age of the fish. In larvae artificial diet leads to considerable increase of tryptic activity, but to low growth rate and finally to total mortality. The reabsorption of digestive enzymes in the hindgut is efficient only in adults in which tryptic activity in the second half of the intestine is reduced to about 12% of total activity.
Changes in skin structure associated with elevated androgen levels in maturing male brown trout, Salmo trutta L.
Authors: Pottinger T. G. , Pickering A. D.
Published: January 2006

Increases in epidermal and dermal thickness, and a reduction in the number of superficial goblet cells, occur in the skin of maturing male brown trout. These changes are correlated with rising levels of plasma 11‐ketotestosterone and it is suggested that control of integumental structure in male fish is mediated by androgenic steroids during sexual maturation.
The effect of time from hatch on the yolk conversion efficiency of rainbow trout, Salmo gairdneri
Authors: Hodson P. V. , Blunt B. R.
Published: January 2006

The growth and development of rainbow trout, Salmo gairdneri, from hatch to first feeding depends upon the nutrients stored in the yolk sac. The efficiency (E) with which yolk can be converted to larval biomass is a useful measurement in chronic toxicity tests, and it can be simply estimated by comparing the gain in larval weight (L) to the loss in yolk weight (Y) at hatch (time 0) and at any time t after hatch: E=(L1−L0)/(Y0−Y1); E may be calculated on a wet or dry weight basis. Although the rates of weight change were constant for the first 15 days after hatch at 10.5° C, E was not. E increased from near 0 and approached a value of 2.1 on a wet weight basis or 0.70 on a dry weight basis after 5–8 days. The variability of E was also very high shortly after hatch, but declined and stabilized within 5–9 days. For toxicity testing, we recommend that E be measured 10–15 days post‐hatch to ensure precision with a minimum bias due to dissection error.
Similarities in feeding behaviour between some marine and freshwater fishes in two tropical communities
Authors: Sazima I.
Published: January 2006

The feeding behaviour and diets of fishes in two tropical habitats, a marine reef and a freshwater pond, were studied comparatively in Brazil. Similarities were found in the tactics employed to obtain food, the social patterns during foraging, and the general diet, notwithstanding lower‐level taxonomic differences between the food items. The feeding behaviours of about one‐third of the fish fauna from each community were approximately equivalent. The feeding categories of these fishes are briefly described. The similarities in the feeding modes probably reflect structural and functional properties shared by the two communities. Additional behavioural similarities of fishes in both habitats are presented and the lack of some particular foraging modes in each community is noted. The picture emerged that different, unrelated fish assemblages have the ability to evolve towards a similar behavioural and structural organization in response to comparable situations and constraints. The value of underwater observations and naturalistic studies on tropical freshwater fish assemblages is indicated.
Carbon, nitrogen and caloric content of eggs, larvae, and juveniles of the walleye pollock, Theragra chalcogramma
Authors: Harris R. K. , Nishiyama T. , Paul A. J.
Published: January 2006

Measurements of dry weight (wt), carbon (C), nitrogen (N) and calories were made on walleye pollock eggs (0.24 mg, 35.3% C, 8.3% N, and 4.6 kcal g−1 dry wt), larvae (0.16 g, 42.9% C, 11.1% N and 5.1 kcal g−1 dry wt) and juveniles (22.4 g, 47.2% C, 9.0% N and 5.6 kcal g−1 dry wt). For juvenile fish (9–360 g wet wt) the measured values were related to dry weight and Fulton's condition factor index (CFI) by regression models. The CFI was a better predictor of body composition than dry weight. As CFI improved from a minimum starvation level of 0.42 to a maximum of 1.16, body caloric content, percentage C, and the C/N ratio increased (kcal g−1 dry wt = 4.4 CFI + 1.7, percentage carbon = 49.7 CFI0.5, C/N ratio = 5.0 CFI + 0.9), while percentage N and percentage ash decreased (percentage N =−3.5 CFI + 12.1; percentage ash = 9.1 CFI−1.4). The results of this study suggest that seasonal C, N and caloric content of young pollock can be estimated from measurements of Fulton's condition factor index.
Changes in reproductive parameters during the spawning migration of pink salmon, Oncorhynchus gorbuscha (Walbaum)
Authors: Dye H. M. , Sumpter J. P. , Fagerlund U. H. M. , Donaldson E. M.
Published: January 2006

The hormones 17β‐estradiol, 17α‐hydroxy‐20β‐dihydroprogesterone(17α, 20β‐P), 11‐ketotestosterone, testosterone, gonadotropin and also vitellogenin, were determined during the spawning migration of wild pink salmon in the Fraser and Thompson Rivers in British Columbia. This stock of pink salmon takes approximately 2 weeks to migrate the 333 km upstream to the spawning grounds. Both sexes were at an advanced stage of sexual development when they entered fresh water. In females both the 17β‐estradiol and vitellogenin levels fell precipitously during the migration, to be very low at spawning, whereas the 17α,20β‐P level rose rapidly, to be highest at arrival on the spawning grounds. The gonadotropin level also rose rapidly during the migration, and was highest in spent fish. Testosterone was at a high level throughout, although this level decreased steadily during migration. In many respects similar endocrine changes were observed in the male. For example, in the case of androgen levels, both testosterone and 11‐ketotestosterone fell steadily during migration but were still relatively high at spawning, whereas both gonadotropin and 17α, 20β‐P levels rose markedly as migration progress. However, although the qualitative changes were often similar between the sexes, the levels of 17α, 20β‐P, testosterone, and gonadotropin were considerably higher throughout in females than in males. It is concluded that this stock of pink salmon is at an advanced stage of sexual development when it enters fresh water. The endocrine changes observed during this study represent those controlling the final stages of reproduction, specifically final oocyte maturation and ovulation in females, and the final stages of spermatogenesis and spermiation in males.
The musculature of the electric fish Eigenmannia virescens (South American green knife fish) characterized with cytochrome oxidase staining
Authors: Behrend K.
Published: January 2006

Using cytochrome C‐oxidase staining, different types of somatic musculature were clearly distinguished in the gymnotoid fish Eigenmannia virescens. Except for a few thin fibres in the region of the horizontal septum, which stained faintly, no others in the trunk muscle stained. Strong staining appeared in the fibres of the anal fin muscles. According to the classification of fish musculature into white, intermediate and red, only the locomotory organ of this fish has red fibres, whereas the trunk muscles are white. The red muscles along the horizontal septum, found in all other fish which have been investigated in this respect, seem to be absent. This is noteworthy since the anal fin alone provides locomotion while the trunk muscles are responsible for posture only.
Quantification of methaemoglobin reduction in red blood cells of the rainbow trout Salmo gairdneri R.
Authors: Mohr A. , Wolf W. , Bohl M. , Hoffmann R.
Published: January 2006

A quantitative methaemoglobin reductase assay was developed applicable for fish blood. In the trial method, plasma and DNA of red cells proved to be sources of error. Satisfactory linearity was obtained after modifying the method. The reaction could not be started by NADPH and was inhibited by citrate. Reduction activity was studied in rainbow trout. DNA and Hb were compared as reference values.
Mortality of young‐of‐the‐year Oreochromis mossambicus in Hartbeespoort Dam, South Africa
Authors: Cochrane K. L.
Published: January 2006

The mortality of Oreochromis mossambicus fry in Hartbeespoort Dam was determined by fitting catch curves to length frequencies of fry, which are spawned continuously from October to March. An inverse relationship was found between survival and population density for the three years 1982–1984.

Fry are subject to cold‐induced mortality in winter and this has a marked effect on standing stock. Winter mortality was classified into four categories of severity which were found to occur randomly with approximately equal frequency. The effect of the mortality on predicting yield is discussed.
A test of a size‐selective predation model with juvenile brook charr, Salvelinus fontinalis
Authors: Grant J. W. A. , Noakes D. L. G.
Published: January 2006

The size distributions of invertebrates in drift samples and stomachs of juvenile brook charr, Salvelinus fontinalis, were compared to test Dunbrack & Dill's (1983) model which predicts the size composition of the diet of stream salmonids. Prey less than 0.4 mm wide were less common in the diet than in the drift, while prey greater than 0.6 mm wide were more common. The behavioural model of Dunbrack & Dill (1983) predicted the actual diet reasonably well, although there were significant differences between the predicted and observed diets in three of four cases.
Migrational swimming speeds of the American shad, Alosa sapidissima, in the Connecticut River, Massachusetts, U.S.A.
Authors: Katz H. M.
Published: January 2006

Of 91 sonic‐tagged American shad, 78 were tracked upriver to their spawning grounds. The remaining 13 tagged shad dropped back downstream over a dam or moved downstream through the adjacent canal system. Sonic‐tagged shad swam upstream individually. ‘Apparent’ swimming speeds (the time to travel between two points) during daylight hours ranged from 11 to 93 cm s−1 when water temperatures were below 20°C and from 9.8 to 64 cm s−1 when water temperatures exceeded 20°C. Swimming speeds at night ranged from 8 to 53 cm s−1. As the flow rate increased, shad swam faster. A major flood, producing flows reaching 300 cm s−1, flushed all sonic‐tagged shad away.
Morphological and functional alterations induced in trout intestine by dietary cadmium and lead
Authors: Crespo S. , Nonnotte G. , Colin D. A. , Leray C. , Nonnotte L. , Aubree A.
Published: January 2006

Effects of oral administration of lead and cadmium on structure and function of trout intestine were investigated in Salmo gairdneri. Fish were fed either cadmium (5 mg kg*1 fish per day) or lead (10 mg kg−1 fish p er day) and sacrificed after a 15 or 30 day treatment.

Levels of cadmium and lead in kidney, liver and spleen were significantly increased by the 15th day of treatment.

Following both cadmium and lead treatment, morphological observations showed an increased mucous cell activity, a disruption of intestinal brush border and an increased renewal rate of absorptive cells.

Influx (Jms), outflux (Jsm) of chlorine and sodium ion and net fluxes were measured on perfused intestinal segments and ouabain‐sensitive sodium, potassium‐ATPase (Na, K‐ATPase) activity was determined on intestinal scrapings. Cadmium did not alter either sodium chlorine transepithelial fluxes or sodium, potassium‐ATPase activity, but lead did. In the middle intestine, lead modified significantly transepithelial sodium and chlorine fluxes (Jms Na: 3.21 ± 0.34 to 1.79 ± 0.29 and Jms Cl: 3.32 ± 0.34 to 1.86 ± 0.22μmol h−1 cm−2, n = 6) after 30‐day diet. Jnet remain unchanged and Na, K‐ATPase activity decreased. In the posterior intestine, lead altered only Jms Na (1.95 ± 0.31 to 0.37 ± 0.09μmol h−1 cm−2) and Jms Cl. Consequently Jnes were also decreased.

So, although both cadmium and lead induce morphological disorders in the middle and in the posterior intestine of the trout, they have different effects on the absorption mechanisms of ions.
A new type of metabolism chamber for the determination of active and postprandial metabolism offish, and consideration of results for coregonid and salmon juveniles
Authors: Dabrowski K. R.
Published: January 2006

The optomotor reaction of juvenile Coregonus schinzipalea Val. et Cuv. and Salmo salar L. was utilized to develop a circular tube metabolism chamber to measure oxygen consumption and ammonia excretion as a function of swimming speed. The metabolism chamber with a constant water flow assured the maintenance of stable conditions. The unidirectional movement of fish was measured in a circular tube with a single narrowing. The relationships between the swimming speed and oxygen consumption or ammonia excretion described by exponential equations allowed the extrapolation towards the standard metabolism, i.e., zero swimming speed. For a juvenile coregonid (0.1–0.15 g individual weight, 2.6–2.8 cm total length) standard metabolism at 14° C was estimated as 0.65 mg02 g−1 h−1 and 17.3 μg N(NH3)g−1 h−1, whereas for juvenile salmon (136mg individual weight) respective values at 22° C were 0.047mg02g−1h−1 and 0.61 μg N(NH3)g−1 h−1. The feeding test with juvenile salmon was also performed in this circular chamber, and in both energy and nitrogen budgets after a meal the partitioning could be precisely attributed to standard metabolism, active metabolism and specific dynamic action (in the case of oxygen consumption) or postprandial nitrogen increase.

The new metabolism chamber allowed the relationship between metabolism and swimming velocity of juvenile fish with developed rheotactic response. It could be used with adult fish for similar purposes.