bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of diet and digestive cycle on the gastrointestinal tract pH values in the goldfish, Carassius auratus L., Mozambique tilapia, Oreochromis mossambicus (Peters), and channel catfish, Ictalurus punctatus (Rafinesque)
Authors: Maier K. J. , Tullis R. E.
Published: January 2006

The digestive tract pH values of the teleost fish Oreochromis mossambicus, Carassius auratus and Ictalurus punctatus were determined in fish that were (1) starved, (2) fed herbivorous, omnivorous and carnivorous diets and (3) fed altered pH diets. The digestive tract pH profile was determined throughout an 8 h cycle. The herbivorous or carnivorous nature of the diet did not affect the pH values in any of the species. Significant differences in gut pH values were observed when the fish ingested diets with altered pHs. There was a difference between the starved and baseline fed values in Carassius auratus which was not observed in the other species. The pH values in the digestive tracts of the three species varied during the digestive cycle.
The effect of dissolved cadmium on the chloride cells of the gills of the stickleback, Gasterosteus aculeatus L.
Authors: Oronsaye J. A. O. , Brafield A. E.
Published: January 2006

The numbers of chloride cells on the gills of three‐spined sticklebacks, Gasterosteus aculeatus, have been measured after exposure of the fish to 0.5, 1.0 and 1.5 mg Cd2+ dm−3 soft water (132 mg dm−3 as CaCO3) and 2, 4 and 6 mg Cd2+ dm−3 hard water (299 mg dm−3). The numbers of chloride cells increased with time but later tended to decline. The significance of this finding is discussed in relation to the functions of chloride cells, one of which is presumed to be to eject absorbed heavy metals such as cadmium.
Sexual maturation in triploid rainbow trout, Salmo gairdneri Richardson
Authors: Lincoln R. F. , Scott A. P.
Published: January 2006

This paper compares some morphological and endocrinological characteristics of diploid and triploid rainbow trout.

Significant differences were found between diploid and triploid females in GSI, condition factor, gut weight, liver weight and percentage dress‐out, and between diploid and triploid males in GSI, condition factor and gut weight.

Diploid females had large, well‐developed ovaries containing yolk‐filled secondary oocytes whereas the triploids had only string‐like ovaries containing nests of oogonia. No primary oocytes were present.

All the diploid males produced copious quantities of milt but it was possible to express a thin, watery milt containing motile spermatozoa from only two of the 12 triploid males. Testes weights in triploids were similar to those of diploids but, while the diploid testes were packed with spermatozoa, those of the triploids consisted mainly of spermatocytes and spermatids with few spermatozoa present. Measurements of the heads of spermatozoa revealed that those from triploids were larger and had a wider size range than those from diploids.

Levels of testosterone and 11‐ketotestosterone in triploid and diploid males were not significantly different. However, levels of testosterone and 17β‐oestradiol in diploid females were considerably higher than those of triploid females.
Interactions of temperature and sublethal environmental copper exposure on the energy metabolism of bluegill, Lepomis macrochirus Rafinesque
Authors: Felts P. A. , Heath A. G.
Published: January 2006

Copper (0.21 mgl−1) caused a decrease in whole body oxygen consumption in bluegills exposed for 32 days, but no changes occurred during days 3, 4 or 9 of copper exposure. In vitro oxygen consumption of gill and brain, were not significantly altered, whereas liver Q O2, was slightly elevated which suggests that copper is acting to decrease oxygen consumption of the whole animal at a higher level of integration than these individual tissues. In fish subjected to an increase in temperature as well as sublethal copper exposure, whole body oxygen consumption was higher than controls 5 days after the temperature was increased, indicating a delay in temperature acclimation in the copper exposed fish. This difference was reflected in higher in vitro oxygen consumption in the liver and gill of these fish suggesting the metal was delaying the process of temperature acclimation by at least in part acting directly on the tissues.
Migration of wild and hatchery reared smolts of Atlantic salmon, Salmo salar L., through lakes
Authors: Hansen L. P. , Jonsson B. , Døving K. B.
Published: January 2006

In 1982 and 1983 descending wild Atlantic salmon smolts, Salmo salar L., were caught in a fish‐trap at the mouth of the River Imsa. Together with hatchery‐reared smolts of the River Imsa strain they were tagged and released at three different sites of the Imsa‐Lutsi watercourse: in the Imsa River 1 km above the trap, and in two lakes, 3 and 11 km upstream of the trap. The recapture‐rate in the fish‐trap decreased with increased migration distance. The hatchery‐reared smolts migrated downstream faster than wild smolts. Lake‐released smolts were considerably delayed in their downstream migration compared to the river released smolts. The results are discussed in relation to environmental and physiological parameters.
Plasma glucose and plasma fatty acid levels of Limanda limanda (L.) in relation to season, stress, glucose loads and nutritional state
Authors: Fletcher D. J.
Published: January 2006

The effects of season, stress, glucose loads and nutritional state on the plasma glucose (PG) and plasma fatty acids (PFA) of Limanda limanda were 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. Limanda showed 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 of Mytilus edulis tissue led to a reciprocal rise and fall of PG and PFA. Short‐term food deprivation had no effect upon PG although PFA rose significantly.
Blood adaptations to marine and freshwater environments in fish of the Family Sciaenidae (Perciformes)
Authors: Mavares R. N. , Pérez J. E.
Published: January 2006

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 pressure.
Studies on relations of bacteria with skin surface of Carassius auratus L. and Poeciloia reticulata
Authors: Crouse‐Eisnor R. A. , Cone D. K. , Odense P. H.
Published: January 2006

Inocula taken from body surfaces of goldfish and guppy indicated the presence of a variety of aquatic bacteria. However, bacteria were not seen when skin samples were studied by means of histology and scanning electron microscopy. Skin from the body flank was essentially a barren field of Malpighian cell surfaces, interrupted occasionally by goblet cell secretions. Under experimental conditions, Aeromonas hydrophila (Gram‐negative, motile rod) attached in large numbers to the dermal surface of artificially made wounds in goldfish, but none was found on adjacent Malpighian cells. Freshly collected skin secretions from goldfish did not influence survival or growth of A. hydrophila in vitro. The study concludes that, under normal conditions, cuticle overlying the Malpighian cells prevents firm attachment and colonization of the skin by aquatic bacteria. It is argued that bacteria isolated by microbiological studies were simply in suspension near the body surface.
Occurrence and distribution of Dolops ranarum Stuhlmann, ectoparasite of freshwater fish in the Transvaal, South Africa
Authors: Avenant A. , van As J. G.
Published: January 2006

During 1982–83 fish parasitological surveys were carried out in 15 dam reservoirs in the Transvaal. The fish ectoparasite Dolops ranarum was found on eight different fish species of which Oreochromis mossambicus. Clarias gariepinus and Barbus marequensis are regarded as main hosts. Distribution records and infestation statistics are presented. It was found that D. ranarum is restricted to the Limpopo Drainage System. An evaluation of site preference on host fish reveals that the mouth cavity, in the case of O. mossambicus, and skin and fins, in the case of C. gariepinus, were the sites most intensively infested by this parasite.
The effect of starvation on RNA: DNA ratios and growth of larval striped bass, Morone saxatalis
Authors: Wright D. A. , Martin F. D.
Published: January 2006

Hatchery reared larval striped bass, Morone saxatilis, 8‐days‐post‐hatching were subjected to various feeding/starvation regimes over a period of 14 days.

Batches of larvae from each treatment were sampled over the 14‐day period and subdivided for determination of notochord length and RNA:DNA ratio. The best growth was found in fully fed F1000 larvae (exposed to 1000 Artermia nauplii l−1), which reached 8.2 mm after 11 days and 9.6 mm after 14 days. Starved animals after 11 days had notochord lengths of 4.9 mm. Growth curves from feeding‐delayed larvae indicated that animals fed after up to 5 days starvation were capable of complete recovery. F100 larvae (exposed to 100 Anemia nauplii 1−l) had a slower growth rate than F1000 larvae, reaching a notochord length of 7.3 mm after 14 days. RNA:DNA ratios over time closely followed notochord growth curves, with clear differences between starved, F100 and F1000 larvae being established after only 2 days. Equilibrium RNA:DNA ratios of 3.0 and 2.25 were established in F1000 and F100 larvae, respectively, 6.8 days after the beginning of the experiment. The average lag time between a change from the starved to the fed condition and a change in RNA:DNA ratio as determined by the divergence of the nucleic acid curve from the starved condition was 0.66 days.

In treatments where starvation followed various periods of feeding, larvae regressed in notochord length such that the final length at 14 days reflected the degree of feeding. RNA:DNA ratios in these animals again closely followed growth curves with a lag time of 0.81 days.

It was concluded that RNA:DNA ratios provided very accurate indices of growth in striped bass larvae which were highly sensitive to feeding status.
Aspects of leucocyte migration in the plaice, Pleuronectes platessa L.
Authors: MacArthur J. I. , Thomson A. W. , Fletcher T. C.
Published: January 2006

Histological studies on plaice tissues revealed mononuclear phagocytes emigrating through capillary endothelium in response to bloodborne foreign erythrocytes, with a >50% increase in circulating leucocytes within 2 h. Despite this rapid influx of leucocytes, cellular accumulation during peritoneal inflammatory responses was significantly slower than in mammals. In vitro studies with chemotaxis chambers revealed that random leucocyte migration was enhanced in the presence of endogenous chemostimulatory substances (inflammatory exudate fluid and endotoxin‐activated plaice serum) although directional migration was not demonstrated. It is suggested that, compared with mammals, the slower accumulation of teleostean leucocytes at sites of injury is not due to a locomotory defect but possibly results from lower levels of endogenous chemoattractants being generated.
The assessment of flow characteristics at certain weirs in relation to the upstream movement of migratory salmonids
Authors: Winstone A. J. , Gee A. S. , Varallo P. V.
Published: January 2006

A major problem in relation to the rehabilitation of migratory salmonids into many industrial rivers in South Wales is the presence of large abstraction weirs which can, under certain flows, constrain the upstream migration of fish. A method is presented whereby the constraints at two weirs on the River Afan were assessed by relating the swimming capacities of different sizes of fish and the flows needed to stimulate upstream movement to the distribution of flows and current velocities. The ‘gateways’ for fish to ascend the weir are calculated, and their significance in relation to historical flow data and the requirement for remedial action are assessed.
Evaluation of pulse fishing for the walleye, Stizostedion vitreum vitreum, in Henderson Lake, Ontario
Authors: Reid D. M. , Momot W. T.
Published: January 2006

A total of 3226 walleye were removed from Henderson Lake, Ontario over 3 years (1980–2), causing the stock to collapse. This removal tested the applicability of ‘pulse’ fishing as a management alternative, and also provided an opportunity to determine which population characteristics might be monitored to serve as predictors of stock collapse in this species.

Following initial exploitation, increased length at age occurred only within younger age‐lasses. To use this response as a predictor, one must first obtain pre‐exploitation length‐at‐age data through using the proper gear to sample small fish. Abrosov's mean age to mean age at maturity index may also forewarn of stress (1.2 critical t value for Henderson Lake), but poor recruitment usually invalidates this index, since the lower angling vulnerability of large fish biases mean age calculations. While annual production estimates were a good indicator of the collapse, their determination required much effort. Petersen population estimates produced much more realistic estimates of population size than Schumacher–Eschmeyer estimates, but both estimates not only require much effort but also are influenced by changes in recruitment.

Poor predictors of the walleye collapse included: catch‐per‐unit‐effort data, which, while giving some idea of fish density, were not good indices of exploitation stress; condition factors, which were not correlated to fish abundance; fecundity increases, which suffered far too much of a retarded response in Henderson Lake to serve as a predictor of stock collapse. The inability to determine accurately sex ratios of measure recruitment made these parameters unless.

At least over the short term, neither northern pike nor white sucker populations have increased following the walleye collapse. As yet, walleye have not returned to their former abundance, so the operational usefulness of ‘pulse’ fishing remains an unknown.
Use of a municipal environmental quality index for understanding and management of aquatic habitats and fish populations
Authors: Katz A. H. , Katz H. M.
Published: January 2006

This study describes the use of a technique developed to assess environmental quality in a municipality. The Environmental Quality Index (EQI) is a tool that can aid land‐use planning, permitting a maximum understanding of the implications for the ecology of an area. A matrix shows the status of each of a series of environmental parameters at each time that an EQI is formulated. Time series analysis is used to quantify environmental impacts on a discrete community's ecosystem: this process allows the graphing of the dynamics of a changing natural resource. Thus, correlation of abiotic changes can be made with changes in biota: for instance, a correlation between proximity to effluents from sewage treatment plants and fish and aquatic plant species diversity is useful information in the managcrnent of fishery resources. Similarly, knowledge of the rate of shift from lotic to lentic waters, due to increased impounding, and its relationship to aquatic plant species diversity is important for land‐use planners who are sensitive to environmental considerations. Decisions made with environmental preservation in mind will help to maintain high quality aquatic habitats.
Pathology of gill and liver tissues from two genera of fishes exposed to two coal‐derived materials
Authors: Stoker P. W. , Larsen J. R. , Booth G. M. , Lee M. L.
Published: January 2006

Bullhead catfish, Ictalurus nebulosus, and rainbow trout, Salmo gairdneri, were subjected to two coal‐derived substances to evaluate each material for potential carcinogenic activity. Substances tested included a solvent‐refined coal heavy distillate and a sediment extract from an industrially polluted river in Ohio. Two subfractions, one containing the polycyclic aromatic hydrocarbons and the other containing the nitrogen heterocycles of each material were also tested. Following a 16‐h exposure period, the gill and liver tissues were removed and examined by standard light and electron microscopy techniques. Hyperplasia of the gill tissue and some engorgement with blood of the secondary lamellae were observed with the light microscope. At the electron microscope level, hepatocyte mitochondria were swollen with a loss of cristae, and rough endoplasmic reticulum fragmented. Results suggest that most of the treatments studied induced pathological responses in fish. Of the two fish tested, the rainbow trout was the most sensitive indicator of environmental pollution.
Rare and little‐known fishes in the Thames Estuary
Authors: Andrews M. J. , Wheeler Alwyne
Published: January 2006

The occurrences of 18 species of rare or little‐known marine fishes in the Thames area are reported. Random dispersal at a pelagic larval or post‐larval stage of development, when movements of fishes can be influenced by currents and tides, may explain the presence of several species. Many of the oceanic or lithophilous species considered in the report could only have originated from the Atlantic Ocean or the western Channel and probably entered the Thames Estuary having moved through the Straits of Dover, but one species is presumed to be vagrant from the northern North Sea. Information provided in the text suggests that two species probably should not be included under the ‘rare’ category which hitherto has been used to describe their status in the Thames Estuary. It is likely that the ‘rare’ categorization arose because the species involved were until recently subject to taxonomic confusion with related species.
Lake resident and migratory smelt, Retropinna retropinna (Richardson), of the lower Waikato River system, New Zealand
Authors: Northcote T. G. , Ward F. J.
Published: January 2006

Retropinna retropinna occurred in two forms in Lake Waahi, North Island, New Zealand. One form was characterized by high mean gill raker counts (c. 28) and low mean vertebral counts (c. 52)—similar to those of non‐migratory, lake resident, native smelt in some other lakes of the lower Waikato River system. The other form had low mean gill raker counts (c. 21) and high vertebral counts (c. 60)—similar to migratory smelt at five sites along the lower Waikato River down to its estuary. The lake resident form was shorter but deeper bodied than the migratory form, as indicated by significant differences in mean length and in weight‐length regression analyses.

The two forms overlapped in time of sexual maturity. As in other native lacustrine smelt populations of the lower Waikato system, the resident form had more but smaller eggs than the migratory form. The egg number to body length regression and the mean egg diameter of migratory Lake Waahi smelt were similar to those of lower Waikato River smelt. Evidence for reproductive separation of the two forms is presented and mechanisms controlling their meristic and other differences are considered.
The food and feeding habits of the goatfish, Parupeneus barberinus (Lacepede), from Aqaba, Jordan
Authors: Wahbeh M. I. , Ajiad A.
Published: January 2006

The food habits of the goatfish, Parupeneus barberinus, from Aqaba were studied. A total of 166 fish over a range of 15 to 27.7 cm and representing five age groups were examined. The major dietary components, based on occurrence, were crustaceans (82.6%), sand (71.1%), foramniferans (55%), detritus (52.3%) and polychaetes (49%). Based on gravimetric analysis, crustaceans and sand were the major food components comprising 54.4% and 23.3% of the total food weight respectively. The food consumption decreased from 1.5% of body weight in the 2‐year group to 0.3% of body weight in the 6‐year group. Seasonal variations were observed in relation to food consumption, percentage weight composition and intensity of feeding.
Growth, body composition and hepatic tyrosine aminotransferase activity in cortisol‐fed channel catfish, Ictalurus punctatus Rafinesque
Authors: Davis K. B. , Torrance P. , Parker N. C. , Suttle M. A.
Published: January 2006

Metabolic consequences of chronic elevation of cortisol in the diet of yearling channel catfish, Ictalurus punctatus, were studied. Cortisol was incorporated into the diet in concentrations of 1, 10, 50 and 100 μg/g of food. This diet was offered at 3% of the body weight per day for 10 weeks. Fish were individually weighed and measured at 2‐week intervals and feeding rates were adjusted. Body weight, liposomatic index and condition factor were significantly lower and food conversion was significantly higher in fish fed 50 or 100 μng cortisol/g of food when compared with controls. The hepatosomatic index of fish fed cortisol at the rate of 100 μg/g of food decreased significantly. Specific activity of hepatic tyrosine aminotransferase was significantly higher at the two highest cortisol doses. Long‐term cortisol administration can reduce growth and condition factor by activating gluconeogenic mechanisms in which lipids and amino acids, rather than carbohydrates, are used for energy production. The metabolic effects of exogenous cortisol in this study offer an explanation for the decreased growth of fish under conditions that activate the secretion of endogenous cortisol.
Histology of the adenohypophysis of the kelp greenling, Hexagrammm decagrammus (Hexagrammidae)
Authors: Hendee J. C. , Mueller G.
Published: January 2006

A combination of fixatives and stains were applied to the adenohypophysis of the kelp greenling, Hexagrammus decagrammus, to determine which were the most suitable for observation under a light microscope. Lillie's calcium acetate formalin (LCAF) followed by haematoxylin and eosin, lead haematoxylin/periodic acid‐Schiff and alcian blue/periodic acid‐Schiff/orange G provides the best general staining characteristics. Lactotropes, corticotropes, thyrotropes, somatotropes, gonadotropes and two types of melanotropes were effectively identified.
Larval ontogeny and morphology of the fire‐tailed gudgeon, Hypseleotris galii (Eleotridae)
Authors: Konagai M. , Rimmer M. A.
Published: January 2006

The larval ontogeny of Hypseleotris galii is described and illustrated. ‘Premature’ yolk sac larvae hatch with unpigmented eyes and no mouth. ‘Late’ yolk sac larvae hatch with pigmented eyes and a functional mouth. Hatching glands are distributed on the head and ventral surface of the body. The yolk is absorbed and the larvae begin feeding 6 days after hatching. Larval development is completed 74 days after hatching. Hypseleotris galii larvae have six pairs of naked neuromasts: two pairs on the head and four pairs on the body. The significance of these results to developmental strategies in Hypseleotris species is discussed.
Growth, mortality, parasitism, and potential yields of two Priacanthus species in the South China Sea
Authors: Lester R. J. G. , Watson R. A.
Published: January 2006

In the northern part of the South China Sea the ‘big‐eye’, Priacanthus tayenus, spawned once a year in June, had von Bertalanffy growth parameters of k = 0.8 and L∞= 30 cm, and a mean total annual instantaneous mortality of Z= 2.0, calculated from adjusted catch curves and a mean length equation. The natural mortality rate M= 1.4, fishing mortality rate F= 0.6, and the exploitation rate (E) was 0.27. The maximum potential yield, calculated using Marten's method, was 0.06 kg/recruit when F= 5.4. The fish were heavily parasitised by the protozoan Pleistophora priacanthicola.

A second big‐eye, P. macracanthus, spawned twice a year in May‐June and September, had growth parameters of κ= 0.7 and L∞= 32, and population parameters of Z= 2.0, .F= 0.7, and E= 0.34. The maximum potential yield was 0.13 kg/recruit when F= 5.8.

A marked reduction in fishing mortality occurred for both species between 1965 and 1966, coinciding with the onset of the Chinese Cultural Revolution. Our estimates of maximum potential yield correspond to fishing mortalities eight times estimated levels, though such heavy exploitation could risk recruitment failure.
Chromosomal studies by blood leukocyte culture technique on three salmonids from Yugoslavian waters
Authors: Al‐Sabti Kabil
Published: January 2006

Three species of salmonids, rainbow trout, Salmo gairdneri, brown trout, S. trutta, and marble trout, S. marmoratus, have been studied for their karyotypes. In rainbow trout 316 metaphases were studied and recorded 2n of 60 with 44 meta‐ to submetacentric and 16 subtelo‐ to telo‐centric chromosomes, and the number of chromosome arms (NF) of 104. Observation on 243 metaphases of brown trout showed 2n of 80 with 20 meta‐ to submetacentric, 60 telocentric chromosomes and the nf of 100. While in 164 metaphases from the marble trout 2n was of the order of 80 out of which 22 were meta to submetacentric and 58 telocentric chromosomes with nf of 108.
The occurrence of Pampus argenteus (Euphrasen, 1788), (Osteichthyes, Perciformes, Stromateoidei, Stromateidae) in the North Sea
Authors: Davis Peter , Wheeler Alwyne
Published: January 2006

The occurrence in the North Sea of a specimen of the white pomfret, Pampus argenteus (Euphrasen, 1788), a mesopelagic fish which is native to the Indian Ocean and particularly South‐east Asia and the East China Sea, is described. Other anomalous distribution records for the same species are examined and some possible explanations investigated.
Estimation of largemouth bass, Micropterus salmoides Lacépède, growth using the liver somatic index and physiological variables*
Authors: Adams S. M. , McLean R. B.
Published: January 2006

Stepwise regression models utilizing five easily‐measured condition indices, two physiological variables and two environmental variables were developed for estimating the monthly growth of age‐I and II largemouth bass sampled during 1980 and 1982. The liver‐somatic index (LSI) and standard metabolism at surface and thermocline temperatures were the most significant variables for estimating growth. Determination of monthly growth using the LSI requires 50% fewer samples than the usual method of following changes in monthly mean weight. Because the LSI responds relatively rapidly to levels of energy intake and temperature, this index can be used to signal possible adverse effects on fish before changes in growth can be observed. This approach could be a useful management tool because, once validated for a particular aquatic system, frequent cost‐effective growth estimates could be used to identify the presence of ecological perturbations and to quantify their effect.
Comparison of two samplers for quantitatively collecting larval fishes in upper littoral habitats*
Authors: La Bolle L. D. , Li H. W. , Mundy B. C.
Published: January 2006

Performance of two larval fish samplers, a hand–towed net and a dropbox enclosure, was similar when tested in shallow (x water depth, 20 cm) upper littoral–zone habitats. There was no significant difference between means of larval fish density (by total catch and by species) estimated from the catch in each gear, during the day and at night. Mean length of larvae (total catch) from the tow net was significantly longer than that from the dropbox during the day, but mean length did not differ between gear at night. Mean lengths of larvae of each species between gear were not significantly different within each period. Both gears collected significantly longer larvae (total catch and by species) during the day than at night probably because of diel movements of larvae of different sizes and species.
A pharmacological dose of 17 β‐oestradiol produces minimal metabolic stimulation but evokes hepatic necrosis in the immature female serranid Epinephelus akaara
Authors: Ng T. B. , Tam P. P. L. , Woo N. Y. S.
Published: January 2006

A pharmacological dose of 17β‐oestradiol (5 mg kg−1 per injection for a total of five injections over a period of 9 days) increased liver and serum lipid concentration and induced vitellogenin into the serum of the immature female red grouper Epinephelus akaara. The levels of electrolytes, glucose, lactate and protein in the serum, and the protein, glycogen and water content of liver and muscle were not affected. The activities of enzymes regulating gluconeogenesis, glycolysis, Krebs cycle, transamination and glycogen synthesis remained unaltered. These findings are in marked contrast to those of Ng et al. (1984) which showed a strong stimulatory effect of a ten‐times smaller dose of 17β‐oestradiol on these biochemical parameters. Ultrastructural examination of hepatocytes of these heavily oestrogenized fish revealed that some cells possessed organelles with an abnormally activated appearance while others had undergone necrotic changes, suggesting that some hepatocytes were overstimulated and subsequently degenerated. Results of the present investigation caution against the use of a pharmacological dose of 17β‐oestradiol in fish culture.
Chitinolytic enzymes and the bacterial microflora in the digestive tract of cod, Gadus morhua
Authors: Lindsay G. J. H. , Gooday G. W.
Published: January 2006

The levels of chitinolytic enzymes and chitinolytic bacteria in the digestive tract of feeding and fasting cod were compared. Enzyme activities within a given tissue were of a similar order irrespective of the presence of chitinolytic bacteria and/or chitin. Cod chitinase and chitobiase are therefore endogenous and constitutive enzymes. Fasting cod had similar numbers of bacteria within the gastro‐intestinal compartments as feeding fish. Representative bacterial isolates from fasting fish were characterized.
Predation on migrating smolt as a regulating factor in Baltic salmon, Salmo salar L., populations
Authors: Larsson P.‐O.
Published: January 2006

The results of three investigations, two with wild smolt and one with hatchery‐reared smolt of altic salmon, were analysed with regard to mortality due to predation during river and estuarine migration. This mortality was found to be high, at least 50% of the initial number of smolt was estimated not to reach marine waters. Smolt mortality may be important in population regulation, analoguous to other animal species having the same life strategy with two life stages and a transfer to a new habitat connected to the shift in life stage.
Feeding biology of Aplocheilichthys normani, Ahl, a small Cyprinodontidae from West Africa
Authors: Romand R.
Published: January 2006

Aplocheilichthys normani is a small Cyprinodontidae endemic in tropical Africa from Senegal to central Sudan. Analysis of the gut content of two populations from Guinea reveals that it feeds mainly on small crustaceans and chironomid larvae. Experimental investigations into its predatory capacity vis‐á‐vis the larvae of Aedes aegypti show that there is a significant difference between the daily feeding rates in adult versus subadult specimens. Moreover, significant 24 h variations were also observed. The feeding rate is also related to the stage of the larvae, i.e. the predatory capacity is greater for smaller prey. The 24h feeding rate variations show that A. normani feeds both during the daylight hours and at night, with a slightly higher predatory activity during the daylight hours. The peak in feeding activity occurs during the two hours before dark. Tests on feeding preferences show that the fish prefers, in descending order, Aedes, Anopheles and Culex larvae. Its larvivorous activity against mosquito larvae was corroborated by small‐scale field studies. We propose that this species be considered for possible use in the biological control of mosquito larvae in West Africa.
The secondary immune response of young carp, Cyprinus carpio L., following injection of cortisol
Authors: Ruglys M. P.
Published: January 2006

Cyprinus carpio immunized at 9 weeks after hatching with either human gamma globulin or trinitrophenylated sheep red blood cells either fail to respond or respond poorly on secondary exposure at 17 weeks of age. Injection of cortisol either simultaneously with the antigen, or 3 days prior to, or 3 days after antigen, permits the antibody response to proceed upon subsequent challenge. The implication of these results for the ontogeny of the fish immune response is discussed.
Trophic diversity in deep‐sea fish
Authors: Mauchline J. , Gordon J. D. M.
Published: January 2006

The general composition and diversity of the diets of the 43 most commonly caught pelagic and demersal fish of the Rockall Trough, north‐eastern Atlantic Ocean, are assessed. The fish are divided into three Groups. The 8 species in Group I consist of both pelagic and demersal species feeding on relatively few prey‐classes and having a diet of low diversity and few items per meal. Group II contains 22 pelagic and demersal species with more diverse diets, less restricted dietary composition, but still consuming relatively few items per meal. Group III is the 12 demersal macrourid species with the most diverse diets, a variable dietary composition and the greatest mean number of items per meal. One species, Maurolicus muelleri, had too many unidentified components in its diet to allow classification in terms of Groups I, II or III. All diets contained dominant items, the diversity within diets offish in Groups II and III arising from the inclusion of subdominants and rare items. The diets of species in Groups I and II can be defined in terms of ecological constitution, trophic diversity and prey‐species composition. Those of the Group III macrourids differ in that their definition is liable to be a compromise between the situation where ecological constitution and trophic diversity are adequately defined but not species composition.
Intensive culture of grass carp and hybrid grass carp larvae
Authors: Opuszynski K. , Shireman J. V. , Aldridge F. J. , Rottmann R.
Published: January 2006

Intensive culture of grass carp and hybrid grass carp (Ctenopharyngodon idella x Aristichthys nobilis) larvae was conducted under Florida (U.S.A.) conditions. The influence of different rearing facilities (indoor tanks, outdoor tanks and cages) and different methods of fish feeding using live zooplankton and artificial food was tested. High survival (86–100%) and satisfactory grass carp growth (47–56 mg) were obtained in the outdoor tanks and cages during the 10–day experiment. It is believed, that the technique described can be used after some improvements for commercial–scale grass carp larvae rearing. Low survival (1–3%) was obtained in the hybrid culture experiment even though satisfactory growth rates (84–212 mg) were obtained after 13 days. High mortality was attributed to genetic abnormalities caused by hybridization. The hybrid does not appear to be a promising fish for culture.
The genetic structure of fish: differences in the intraspecific distribution of biochemical genetic variation between marine, anadromous, and freshwater species
Authors: Gyllensten U.
Published: January 2006

Biochemical genetic markers have been increasingly used for inferences on the population genetic structure of various fish, but little attention has been paid to relative differences in the distribution of variability within species in different groups of fish. Nested gene diversity analyses of multiple locus electrophoretic data from the literature for 19 species (6 marine species, 4 anadromous salmonids, and 9 freshwater species (5 salmonids)), mainly from Scandinavia and North America, show that (i) average heterozygosity is higher in marine species than in freshwater species, (ii) the average fraction of the total gene diversity allocated between localities increases in the order marine (1.6%), anadromous (3.7%), and freshwater species (29.4%), and (iii) the fraction of the total gene diversity associated with differences between geographic clusters of localities is generally smaller than that between localities within clusters. This finding is consistent with that the differentiation observed in most species is of postglacial origin, and that the timespan available since deglaciation has been too short to result in the accumulation of substantial differences between clusters.
Seasonal changes in serum glucose and condition of the plaice, Pleuronectes platessa L.
Authors: White A. , Fletcher T. C.
Published: January 2006

Monthly sampling of plaice caught off the north‐east coast of Scotland between February 1983 and May 1984 revealed a seasonal increase in condition factor, hepatosomatic index and serum glucose, which appeared to be related to the period of active feeding. The spleen indices followed a similar seasonal increase, although this was not statistically significant, while the kidney indices showed little change over the 16 months. The peak for the gonadosomatic index was in February/March 1984, but among these plaice (aged 4–5 years) there were still large numbers of immature males and females and there was no increase in 1983. Apart from the hepatosomatic index for January 1984, there was no significant difference between male and female plaice.
Infestations of Atlantic salmon, Salmo salar, by Gyrodactylus salaris in Norwegian rivers
Authors: Johnsen B. O. , Jensen A. J.
Published: January 2006

Over the 6 years 1980–85, 212 Norwegian rivers have been examined for occurrence of Gyrodactylus salaris: it was found in 26 rivers and six salmon hatcheries scattered throughout the country from Troms county in the north to Sogn og Fjordane in western Norway. The distribution of G. salaris is connected with the stocking of fish from infected salmon hatcheries. The populations of salmon parr have been drastically reduced in the infected rivers. In later years catches of ascending salmon in these rivers have also sharply declined: in 1984 salmon fishery losses were estimated at 250–500 t.

Gyrodactylus salaris is most probably a recent introduction to Norwegian rivers. A primary aim is to exterminate this parasite from all infected rivers and hatcheries: so far this has been accomplished in one river and one hatchery.
Oxygen consumption in Oreochromis niloticus (L.) in relation to development, salinity, temperature and time of day
Authors: De Silva C. D. , Premawansa S. , Keembiyahetty C. N.
Published: January 2006

Oxygen consumption of Oreochromis niloticus at different stages of development was studied in relation to salinity, temperature and time of day, using a Warburg apparatus. The oxygen consumption of newly hatched (0–14 h) larvae was 3.40 μl O2 larva−1 h−1, of older yolk sac larvae 10.09 μl O2 larva−1 h−1, and of one‐month‐old fry 32.99 μl O2 larva−1 h−1. The QO2 values showed a decrease with development and growth, ranging from 21.2–26.0 μl O2 mg−1 h−1 in newly hatched larvae to 2.97 μl mg−1 h−1 in one‐month‐old fry. Changes in oxygen consumption occurred with salinity, the highest being at 17%o. Active larvae (12‐24 mm T.L.) showed a doubling of consumption with a 10° C rise in temperature, and their Q10 factor increased from 2.25 to 3.43 with increasing size. Day‐old yolk‐sac larvae, late yolk‐sac larvae (5 days old) and fry of 12 14 mm length all showed a depression in oxygen consumption at midnight followed by a dawn rise.
The feeding ecology of Pleuronectes platessa L., Limanda limanda (L.) and Scophthalmus rhombus (L.) in Carmarthen Bay, South Wales, U.K.
Authors: Wyche C. J. , Shackley S. E.
Published: January 2006

To assess the feeding habits of plaice, Pleuronectes platessa L., and dab, Limanda limanda (L.), within Carmarthen Bay, three sampling techniques were used: benthic trawling and surf‐zone push‐netting were undertaken during the feeding season for the gut contents of plaice and dab (age groups 0‐IV) and of 0‐group brill, Scophthalmus rhombus, to be analysed in detail, and a benthic macro‐fauna grab survey covered the trawled ground to assess the distribution of food species in relation to gut contents. Plaice consumed commonly‐occurring food species whereas dab took any available food. The main items were the same for both species, but secondary food preferences differed. Variations in gut contents within species, for the same sized fish, chiefly resulted from the spatial distribution of fish and not seasonal variations in the benthic macro‐fauna. The length and not the age of fish primarily determined the selection of food organisms.
Some effects of low pH and calcium on the growth and tissue mineral content of yearling brown trout, Salmo trutta
Authors: Sadler K. , Lynam S.
Published: January 2006

Yearling brown trout, Salmo trutta, were exposed to low mineral content water (nominal concentrations of 20μmol 1−1 magnesium, 7.7 μmol 1−1 potassium, 44 μmol 1−1 sodium) over a pH range of 4.0–5.2 with ambient calcium concentrations of 2.5–60 μmol 1−1. All fish died at pH 4.0 and 4.2 irrespective of ambient calcium concentration and also at pH 4.4 with only 2–3 μmol 1 −1 calcium (that is calcium‐free water except for that leached from the diet or excreted by the fish). Good growth rates were obtained over the remaining treatments which extended down to pH 4.4 with as little as 7 μmol 1−1 calcium. When starved, weight loss was inversely correlated with pH. Effects on plasma chloride, percentage dry weight and calcium, potassium sodium, and phosphorus contents of skin, muscle and bone tissue were also investigated. These demonstrated pH effects on mineral metabolism in starved fish, but no effects were detected in fed fish.
Morphological and phagocytic characteristics of peritoneal exudate cells in tilapia, Oreochromis niloticus (Trewavas), and carp, Cyprinus carpio L.
Authors: Suzuki K.
Published: January 2006

The morphology and phagocytic activity of peritoneal exudate cells (PEC) obtained by an intraperitoneal injection of liquid paraffin into tilapia, Oreochromis niloticus, and carp, Cyprinus carpio, were studied with light and electron microscopy. PEC consisted of monocyte‐macrophage series cells (M‐Mø), neutrophils, eosinophils (granular cells) and others. Cells exhibiting the same morphology as mammalian macrophages but different from monocytes of the same species were identified with light and electron microscopy and designated as peritoneal macrophages. Light and electron microscopy revealed that M‐Mø, neutrophils and eosinophils (granular cells) phagocytozed foreign materials added in vivo and in vitro. Eosinophils appeared later in the peritoneal exudate and less actively phagocytic as compared with M‐Mø and neutrophils. Small and large phagosomes were formed in M‐Mø, neutrophils and eosinophils (granular cells). Large phagosomes were common in neutrophils. Fusion of cytoplasmic granules with the phagosome membrane was observed. The in vitro experiment on phagocytosis revealed that the phagocytic rates in M‐Mø and neutrophils were positively correlated with the doses of foreign materials. The results indicated that these two cell types have the highest capacity of phagocytosis.
Physiological salines and the mechanical properties of trout red blood cells
Authors: Hughes G. M. , Kikuchi Y. , Barrington J.
Published: January 2006

Suspensions of rainbow trout erythrocytes in different physiological salines were compared with respect to their haematological and filtration properties.

A method is described for the suspension of erythrocytes in Cortland saline which has proved suitable for studies of their mechanical properties over periods of several hours.

Significant differences were found between whole blood samples taken during cannulation and after several days recovery, particularly mean cell volume, frequency distribution of red cell volumes and the pore passage time through nucleopore filters. These differences were also found using red cell suspensions of the same bloods. The pore passage time of whole blood sampled during cannulation or its suspensions is less than that of recovery blood although its mean cell volume is greater.
Upstream migration of adult Atlantic salmon, Salmo salar L., in the River Vefsna, northern Norway
Authors: Jensen A. J. , Heggberget T. G. , Johnsen B. O.
Published: January 2006

Daily ascents of adult Atlantic salmon (Salmo salar) in the Laksforsen waterfall in the River Vefsna were recorded over 3 years. Ascent was correlated to 12 physical and meteorological parameters by multiple regression analysis. Change in water temperature was included in the regression model in all 3 years, and change in river flow was also included in 2 of the 3 years. No other variable was included in the regression model at the 0.05 significance level.
Population estimates of juvenile Atlantic salmon, Salmo salar, as indices of smolt production in the R. Scorff, Brittany
Authors: Baglinière J.‐L. , Champigneulle A.
Published: January 2006

The numerical production of juvenile Atlantic salmon was estimated on an Armorican Massif river (Brittany), using habitat characteristics of the main stream and an annual electrofishing census from 1975 to 1983. This showed that (i) 0 + fish accounted for 79% of the production; (ii) there were larger annual variations of production in spite of some compensatory events depending on genetic and environmental factors; (iii) riffles and rapids (depth <40cm, current velocity > 40 cm s−1) were the more productive habitats, providing 86.4% of the production from 28% of the water area; (iv) the middle course of the river accounted for 57.6% of production, producing more 1 + individuals in a large area of rapids.

Features of this method, their limitations and the value of the results are discussed in relation to the estimation of smolt production.
Fish distribution in Kainji Lake, Nigeria
Authors: Balogun J. K.
Published: January 2006

A study of the distribution of fish populations in the inshore, surface and bottom water habitats of L. Kainji, and comparison with previous data, showed that there has been a relative increase in the populations of the fish families Cichlidae, Bagridae, Schilbeidae, Centropomidae and Cyprinidae and a relative decrease in the populations of the Characidae, Mochokidae, Citharinidae and Mormyridae. The overall composition of fish families caught in the three habitats varied significantly (P<0.05). Four of the nine major families showed habitat preference: there was a preponderance of Cichlidae and Centropomidae in the inshore water habitat; Bagridae were evenly distributed in the inshore and bottom waters; and Schilbeidae were the most abundant in the surface water habitat. There were significant differences in the total catch among the various sampling stations. However, there was no significant difference in the catch of various family groups except in Cyprinidae. It was established that overall catches from the three major habitats were inversely proportional to water level in the lake.