bluuebunny/crossref_metadata_2025_split huggingface dataset:
A radiographic estimation of the effect of temperature on gastric emptying time in Sarotherodon niloticus (L) × S. aureus (Steindachner) hybrids
Authors: Ross B. , Jauncey K. 
Published: January 2006

A radiographic technique was used to determine temperature effects on gastric emptying time in S. niloticus/aureus hybrids. Stomach evacuation times for 30 g fish fed 3% of their body weight were 8.5 h at 30° C, 10.8 h at 25° C and 16.4 h at 20° C. Hence, there was a negative correlation between stomach evacuation time and temperature. The Q10 between 20 and 30° C was calculated to be 1.92. Similar relationships were found for intestinal evacuation and total evacuation.The data were used to estimate maximum daily feed intake levels of fish within the size range studied. Levels for 30 g fish were 8.5% body weight at 30° C, 6.6% at 25° C and 4.4% at 20° C. However, the optimum feeding regime should take account of the feeding behaviour of the animals.
Changes in selected blood component values of rainbow trout, Salmo gairdneri Richardson, following the blocking of the cortisol stress response with betamethasone and subsequent exposure to phenol or hypoxia
Authors: Swift D. J. 
Published: January 2006

Cortisol was undetectable in rainbow trout plasma 24 h after the fish had been injected with betamethasone. This drug is known to suppress ACTH release and, consequently, cortisol production in teleosts. The blood glucose, chloride, sodium, potassium and total protein concentrations were not significantly affected by betamethasone. However, significantly increased blood packed cell volume values were found.Betamethasone‐injected fish when exposed to hypoxia or phenol had a pattern of blood component changes similar to those found in sham‐injected fish also exposed to the pollutants. These changes in turn were similar to those found in exposed but uninjected and unhandled fish. Suppression of rainbow trout plasma cortisol concentrations with betamethasone apparently has no effect on the fish's short‐term blood component responses to pollutants under the conditions used in these experiments, but does prevent a stressormediated increase in plasma cortisol concentrations.
Changes in intestinal fluid transport associated with smoltification and seawater adaptation in coho salmon, Oncorhynchus kisutch (Walbaum)
Authors: Collie N. L. , Bern H. A. 
Published: January 2006

The intestinal role in osmoregulatory preadaptation of freshwater‐adapted (FW) yearling coho salmon during smoltification was examined. Measurements of intestinal net fluid absorption (JV) using an in vitro sac preparation showed that JV of FW parr was significantly less than that of either FW or seawater‐adapted (SW) smolts. From two to four weeks following the springtime thyroxin surge, JV increases in FW coho to a level comparable with that observed for SW smolts. JV remained elevated in FW smolts throughout most of the summer and then decreased in the autumn. Two months after the thyroxin peak, intestinal wet weight per unit serosal surface area increases. Coho stunts resulting from premature transfer into sea water had significantly higher JV than that seen in SW smolts. The elevated JV of stunts is only partially explicable on the basis of differences in body weight between stunts and smolts.Our observations indicate that an increase in intestinal fluid absorption is a preadaptive change associated with smoltification occurring in concert with alterations in renal and branchial osmoregulatory mechanisms. The timing of the increase in JV suggests a phase relationship to the thyroxin surge. This temporal relationship may help to explain the efficacy of using changes in plasma thyroxin levels to predict hatchery‐fish release dates that may optimize eventual seawater survival.
Effect of food attractants on appetite and growth rate of gilthead bream, Sparus aurata L.
Authors: Tandler A. , Berg B. A. , Kissil G. wm. , Mackie A. M. 
Published: January 2006

Appetite and growth rate were measured in Sparus aurata fed ad‐libitum a basal diet supplemented with either a synthetic mixture of chemicals based upon the analysis of Mylilus edulis, muscle extract, or newly hatched Artemia saline nauplii. These components were tested for their feeding attraction potency, and were added to the basal diet at three concentrations each; 5, 10 and 20 g kg‐1 dry diet.Appetite, which was defined as ad‐libitum food intake, was significantly affected by the type and concentration of attractant. When the basal diet was supplemented with 10 or 20 g kg‐1 of the synthetic Mytilus edulis muscle extract, it was associated with significantly higher appetite than the basal diet only or the basal diet supplemented with any level of newly hatched Artemia salina nauplii. On the other hand, relative growth rate under the same conditions did not completely conform to the results with appetite. The difference between appetite and growth rate as criteria for the evaluation of food attractants is discussed.
Vertical distribution and abundance of the Peruvian anchovy, Engraulis ringens, and sardine, Sardinops sagax, larvae during November 1977
Authors: Sameoto D. 
Published: January 2006

Horizontal samples taken with the BIONESS at various depths on 13 stations within 115 km of the coast of Peru showed nine species of fish larvae present with the most common of these being, in order of abundance, Leuroglossus stilbius, Sardinops sagax, Diogenichthys laternatus, Merluccius gayi and Engraulis ringens. All the species except S. sagax and E. ringens showed a diurnal migration to the upper 30 m of water at night. The two above species were present in the top 30 m at all times. The size of the larvae of all species did not vary with time, depth or sample location. The numbers of larvae increased with zooplankton m−3 up to 1000 copepods m−3 above which no further increase in larvae occurred. A significant linear relationship was found between the total number of larvae m−2 and biomass and zooplankton m−2, but not between individual species of larvae and zooplankton biomass. Significant correlations were found between E. ringens and seven species of copepods found in the upper 50 m of water.Polymodal analysis showed that the larval populations of all species, with the possible exception of S. sagax, were made up of more than one sub‐population. From this analysis the length of the spawning season forE. ringens was estimated at 54–68 days.A significant correlation was found between the numbers of E. ringens larvae m−2 and the maximum concentration of chlorophyll α, as measured with Batfish, in the area of the BIONESS stations. This showed the largest numbers of larvae in areas of the highest chlorophyll concentrations.
Swimming performance of juvenile sprat, Sprattus sprattus L., and herring, Clupea harengus L., at different salinities
Authors: Turnpenny A. W. H. 
Published: January 2006

Sustained swimming performance of juvenile sprat, S. sprattus (29–48 mm s.l.), and herring, C. harengus (46–58 mm) was measured in a laboratory flume over a range of salinities from 18 to 33%0 at water temperatures of 16–19°C. Critical swimming speeds (CSS) of both species, relative to body length, were similar, averaging 10–12 body lengths per second (bl s−1). There was no apparent relationship with salinity.These swimming speeds are higher than values generally quoted in the literature for sustained swimming of sprat and herring (2–7 bl s−1) and it is concluded that the better performance found in this study was a function of improved fish handling techniques, and of the size of fish used since most other studies have dealt with larger, commercial sized fish.
Digestion of free‐living nematodes fed to fish
Authors: Hofsten A. V. , Kahan D. , Katznelson R. , Bar‐El T. 
Published: January 2006

Free‐living nematodes—Panagrellus sp., Turbatrix aceti, Caenorhabditis elegans and C. briggsae—were each fed to the fish Danio sp. and the process of their digestion, in the fish alimentary canal, was studied by light and electron microscope.Almost no identifiable nematodes were found in the fish gut when the digestion period was 3 h or more, except for buccal capsules of the four studied species, males' spicules of Panagrellus sp. and Turbatrix aceti and egg‐capsules of the Caenorhabditis species. These structures could serve as indicators that the nematodes had been preyed on and digested by the fish.Differences in the mode of digestion were noticed between the various species of nematodes studied, after a period of 0·5–1 h, in the fish gut. In Panagrellus sp. and T. aceti disintegration of the soft inner tissues occurred mostly at the anterior or posterior ends of the nematode's body, while in Caenorhabditis the majority of digested nematodes were affected at both ends or evenly along the entire body. Digestion seemed to be initiated mostly at the nematodes' body apertures: mouth, anus or cloaca, and vulva which could be due to a more vulnerable cuticle around those areas. Disintegration proceeded from the soft inner parts to the more resistant cuticle that was finally disintegrated. Of the three layers of cuticle the most resistant were the external cortex and the basal layers.
Inter lake comparison of liver morphology and in vitro hepatic monodeiodination of L‐thyroxine in sexually mature coho salmon, Oncorhynchus kisutch Walbaum, from Lakes Erie, Ontario, Michigan and Superior
Authors: Leatherland J. F. , Sonstegard R. A. 
Published: January 2006

The hepatosomatic index (HS1) of female sexually mature coho salmon, Oncorhynchus kisutch, from Lake Superior was significantly higher (P<0.01) than in males, whereas that of females from Lake Erie was significantly lower (P<0.05) than in males; there was no significant sex differences in coho salmon from Lakes Ontario or Michigan. Hepatic nuclear areas (HNA) were significantly higher (P<0.01) in males compared with females in fish collected from Lakes Ontario and Erie, but there was no sex differences in HNA of coho salmon from Lakes Superior or Michigan. In all four lakes, hepatocyte cytoplasmic volume was significantly higher (P<0.01) in males than in females from the same lake, and the cytoplasmic volume: nuclear volume ratio of males was corresponding significantly higher (P< 0.05) than in females from the same lake.Two hepatocytic cell types were evident, termed' light and dark cells, based on the electron density of their cytoplasmic matrix. There were considerable intersex and interlake differences in the relative populations of light ‘and dark’ cells in coho salmon from Lakes Ontario, Michigan, Erie and Superior, and also in the hepatocytic content of lipid, glycogen, mitochondria and ribosomal and smooth endoplasmic reticulum.There were no sex differences with regard to in vitro hepatic monodeiodination of L‐thyroxine (T4) to triiodo‐L‐thyronine (T3) in salmon from any of the lakes. However, T4 to T3 conversion was significantly lower (P< 0.05) in liver homogenates prepared from Lake Ontario coho salmon than in comparable preparations of liver from Lake Superior, Lake Erie, or Lake Michigan salmon.
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.
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.
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.
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.
Interspecific interactions and diet of sympatric juvenile brook charr, Salvelinus fontinalis, and adult ninespine sticklebacks, Pungitius pungitius
Authors: Gaudreault A. , Miller T. , Montgomery W. L. , FitzGerald G. J. 
Published: January 2006

Breeding male ninespine sticklebacks, Pungilius pungitius, are highly aggressive toward juvenile brook charr. Salvelinus fontinalis, in the Matamek River, Québec. Field observations revealed that such aggression was always initiated by the sticklebacks and only if the charr approached their nests or free‐swimming fry. There was considerable overlap in diet in August, but not in June and July, suggesting competition for food is possible under some circumstances.In laboratory stream tanks, we compared frequency of intraspecific and interspecific aggression of single and mixed species groups over a range of densities. There was no simple relationship between aggression and density for either species, although significant differences in aggression occurred among fish in some of the different density conditions.
Protogynous hermaphroditism in the slinger, Chrysoblephus puniceus (Gilchrist & Thompson, 1908) (Teleosteir:Sparidae)
Authors: Garratt P. A. 
Published: January 2006

Hermaphroditism in the marine fishes is well documented, especially in the family Sparidae in which at least 35 species have been reported. Within this family sexuality ranges from gonochorism, through rudimentary, protogynous and protandrous hermaphroditism, to what is thought to be a single functional hermaphrodite.A biological study of the economically valued Chrysoblephus puniceus revealed marked differences in the size of male and female fish, suggesting that this sparid undergoes sex reversal. Histology of gonads macroscopically classified as ‘female’, ‘male’ and ‘hermaphrodite’ were analysed. Degenerating pre‐vitellogenic oocytes in the ovarian sections of hermaphroditic gonads confirm that C puniceus is a protogynous hermaphrodite.
Observations on the size, dry weight and energy content of the eggs of some demersal fish species from British marine waters
Authors: Hislop J. R. G. , Bell M. A. 
Published: January 2006

The diameters, dry weights and calorific value of the eggs of seven gadoid species (cod, Gadus morhua, haddock, Melanogrammus aeglefinus, whiting, Merlangius merlangus, Norway pout, Trisopterus esmarkii, lythe. Pollachius pollachius, saithe, P. virens, ling. Molva molva) and one pleuronectid (plaice, Pleuronectes platessa) were measured. Ling eggs contain an oil globule; the eggs of the other species do not.Preservation in formaldehyde solution caused a small (<4%) reduction in egg diameter but a large (15–30%) reduction in dry weight. There was no significant difference between the dry weights of unpreserved eggs weighed after (a) oven‐drying at 60° C or (b) freeze‐drying. Equations relating the dry weight of unpreserved eggs to unpreserved diameter and to preserved diameter are given for six species, and general equations that may apply to all North Sea gadoids whose eggs lack an oil globule are calculated. The calorific values of the dried, unpreserved eggs of all species except ling were similar (mean 23.19 kJ g−1, S.D. 1.50) but the value for ling was higher (mean 26.92 kJ g−1, S.D. 2.29). The estimated energy content (kJ 1000 eggs−1) of eggs of each species are tabulated.
The fish populations of some streams in Wales and northern England in relation to acidity and associated factors
Authors: Turnpenny A. W. H. , Sadler K. , Aston R. J. , Milner A. G. P. , Lynam S. 
Published: January 2006

Electrofishing and water quality surveys were carried out on 60 upland moorland streams in central and north Wales and the Peak District of England (south Pennines). A number of biological characteristics of the fish populations were recorded, including species representation, population density and biomass and, for brown trout, Salmo trutta L., only, growth, condition factor and diet. The stream waters were also analysed over a 2‐year period for pH, calcium, aluminium and the heavy metals copper, zinc and lead.Mean pH levels in the streams ranged from 5.0 to 7.6, with calcium concentrations in the range 0.80–27 mg 1−1. Trace metal concentrations (Al, Cu, Zn, Pb) tended to be elevated in the more acid streams. The latter had fewer fish species, and a higher proportion was fishless, 73% at pH < 5.5 compared with 6% at pH >6.5. Trout and eels, Anguilla anguilla L., predominated at lower pH values, but at reduced population levels.Dietary composition and stomach fullness of trout were similar throughout the stream pH range. More than 40% of the diet was derived from surface and terrestrial sources, supplementing autochthonous items. Growth (as back‐calculated length to end of first year of life) and condition factor did not vary significantly with respect to stream acidity. It is thus concluded that the impoverishment of trout populations in the more acid streams was not a second‐order effect acting through the lower trophic levels.Water quality acting directly on fish would appear to account for the poor status of salmonid fisheries in acid streams. Absence or paucity of salmonids was related to high levels of labile monomeric aluminium (>40 μgl−1) or Cu‐Zn‐Pb toxicity (>0.4 t‐LC50 to rainbow trout, Salmo gairdneri Richardson). Limiting values in this study correspond well with published laboratory and field data.
The problem of sexual inversion in the minnow, Phoxinus phoxinus (L.)
Authors: Rasotto M. B. , Cardellini P. , Marconato E. 
Published: January 2006

The incidence of sexual inversion in Phoxinus phoxinus has been studied by examining histologically (a) the gonads of 406 adult specimens caught from the wild during a period of 16 months, (b) the gonads of 168 adults kept in captivity in groups with an experimentally altered sex‐ratio, and (c) the differentiation of the gonads in the fry.All the adults had either testes or ovaries and no case of intersexuality was observed. For both testis and ovary, we recognized two phases, depending on the seasonal cycle: an active spring‐summer phase, corresponding with the period of reproduction, and a quiescent autumn‐winter phase. The ovaries showed an asynchrony in oocyte development, which is typical of species that spawn many times during the breeding season.In P. phoxinus the ovaries are easily recognizable just one month after hatching and testes are well differentiated in 2‐month‐old fingerlings. Differentiation is, therefore, precocious and follows a pattern typical of gonochoristic species in which hermaphroditism never occurs.