bluuebunny/crossref_metadata_2025_split huggingface dataset:
Energetic costs at different levels of feeding in juvenile cod, Gadus morhua L.
Authors: Soofiani N. M. , Hawkins A. D. 
Published: January 2006

The energetic costs associated with feeding by juvenile cod were determined by means of an open‐circuit respirometer. Fish acclimated to several temperatures (7, 10, 15 and 18°C) were kept at natural lighting levels, and fed inside their individual respirometers. They consumed a diet compounded from natural foods, at five different ration levels, their oxygen consumption being monitored continually over an 11–16 day period.After each meal the rate of oxygen consumption increased to above the pre‐feeding level, reaching a peak 8–10 h later. With each successive meal the oxygen consumption showed a cumulative increase, reaching a maximum usually after the last meal.The elevation in metabolic rate associated with feeding was dependent upon ration size, increasing linearly as the food intake increased. The effect was also dependent upon temperature; for fish fed to satiation the total energy cost was equivalent to 11.9, 10.9, 16.4 and 17.1% of the ingested energy at 7, 10, 15 and 18°C respectively. For resting satiated fish the rate of oxygen consumption was close to the maximum rate for active fish.
Distribution and ultrastructure of taste buds in the oropharyngeal cavity of the rainbow trout, Salmo gairdneri Richardson
Authors: Ezeasor D. N. 
Published: January 2006

The distribution, external surface morphology and ultrastructure of taste buds in the oropharyngeal cavity of the rainbow trout, Salmo gairdneri Richardson, were studied using scanning and transmission electron microscopes (SEM and TEM). The SEM revealed three taste bud types, varying only in their degree of elevation from the general level of the epithelium. Types I and II were located on elevated papillae associated with teeth on the dentary, maxilla, palate, tongue and pharyngeal pads while the unelevated Type III were mainly found in the anterior (branchial) pharynx.Each taste bud was composed of four cell types: basal, dark, intermediate and light cells, the apical processes of the last three filling the taste pores. The intermediate and light cells appeared similar in ultrastructure, varying only in the amount and organization of smooth endoplasmic reticulum (SER) in their cytoplasm. In addition to its contacts with the processes of intragemmal nerves distally, the basal cells established independent contacts with processes of extragemmal nerves basally. It is suggested that the distribution of the taste buds and their close association with teeth are adaptations to the predatory feeding habit of the rainbow trout. Age differences may account for the existence of two types of gustatory cells and the manner of innervation of the taste bud suggests the existence of two pathways for the transmission of gustatory sensation to the central nervous system (CNS).
Overwintering mortality of migratory Arctic charr, Salvelinus alpinus, (L.) reared in salt water
Authors: Wandsvik A. , Jobling M. 
Published: January 2006

The mortality of Arctic charr, Salvelinus alpinus, previously grown‐on in salt water during the summer months, was studied during the winter 1980–81. Mortality did not appear to be related to a‘ critical size‘ but rather to rates of growth shown by the fish during the summer months. Mortality was high amongst the slow‐growing fish.The results are discussed in relation to published data on the osmoregulatory capabilities of Salvelinus spp.
Reproductive anatomy of the Australian grayling, Prototroctes maraena Gunther
Authors: Berra T. M. 
Published: January 2006

Gross anatomy of Australian grayling testes showed progressive enlargement from March to the peak of the spawning season in late April–early May. The single, left testis changed from a flat, translucent wisp of tissue consisting of an anterior and posterior lobe connected by a thin filament to a three‐dimensional mass of milky‐white tissue which filled the coelomic cavity. Spawning lasted 2 weeks and testicular regression was apparent by 8 May when the bilobed condition of the testis was noted. The testis cleared rapidly and resembled pre‐spawning conditions by mid‐June. Histological examination revealed that Australian grayling testes follow the pattern of teleost spermatogenesis whereby clusters of spermatogonia arise from resting germ cells and all of the cells within a given cluster mature at approximately the same time.The single left ovary of Australian grayling females showed a similar pattern of development, filling the body cavity with an average of 47 000 eggs of 0.9 mm diameter by late April–early May. Females exhibited swollen genital vents near spawning and males developed breeding tubercles which are illustrated by scanning electron micrograph.
Fish production in Oued Sebaou, a seasonal river in North Algeria
Authors: Penczak T. , Moliński M. 
Published: January 2006

Fish were sampled by electrofishing at three contiguous sites 26 km from the source of Oued Sebaou, a seasonal river in North Algeria. River discharge ranges from 300 m3s−1 in the peak of the rainy season to 0.1 m3s−1 at the end of the dry season. Extensive gravel extraction from the river bed takes place during the dry season.Two species were recorded at each site: Barbus callensis, which is heavily fished locally, and Anguilla anguilla. The three sample maximum likelihood Zippin method was used to estimate mean density and standing crops, which were: barbel, 452 fish ha−1, 5.33 kg ha−1; eels, 149 fish ha−1, 3.04 kg ha−1. Estimated average biomass and production were: barbel, 2.31 kg ha−1, 4.27 kg ha−1 year−1; eels, 1.51 kg ha−1, 2.60 kg ha−1 year−1.
The effect of the migration of Alosa fallax fallax (Laécpède) into fresh water, on branchial and gut parasites
Authors: Aprahamian Miran W. 
Published: January 2006

The prevalence and relative density of branchial and gut parasites taken from Almafullax in the estuary of the River Severn, at the start of the freshwater phase of its spawning migration, were compared with those taken from their spawning grounds in fresh water. Mazocrues alosue showed no significant difference in prevalence between the two habitats, though their relative density did fall significantly. Because of the direct relationship between length and relative density, this difference may be explained by the estuary samples of A. fullux being of fish significantly larger than those from fresh water. Other possible causes are discussed. The prevalence and relative density of M. alosae showed a trend to increase with age of the host. Repeat spawning A. fallax had a significantly greater relative density and prevalence of M. alosue when compared to virgin fish.Analysis of the sampled population showed that Clavellisu emarginata declined significantly in both prevalence and relative density in fresh water, and this was confined to the younger and first time spawning A. fullux. Thynnuscuris aduncum showed significant reductions in prevalence and relative density of infection in fresh water when compared to the estuarine samples.The species Hemiurus uppendiculatus and Pomphorhynchus laevis showed no significant difference in prevalence and relative density of infection, and Pronoprymna ventrzcosa no significant difference in prevalence, between the two habitats.
Habitat evaluation as a fisheries management tool
Authors: Milner N. J. , Hemsworth R. J. , Jones B. E. 
Published: January 2006

The application, rationale and process of habitat evaluation methods are discussed in the context of present day fisheries management. The need to consider habitat features at site and catchment level is stressed.Development of habitat evaluation techniques for assessing brown trout habitat in Welsh streams is reported, and examples of these approaches are given: qualitative (visual assessment), semi‐quantitative (a combination of subjective and quantitative measurements) and quantitative (measurements on transect system). Habitat attribute‐fish population models were based on functional linear regressions and multiple regression (for the quantitative method). Quantitative models explained up to 80% of the variance in abundance of medium sized (10–20 cm) trout in hard water (>25mgl‐1 CaCO3), but were less effective when data from soft waters were included. Testing of the qualitative and semi‐quantitative methods on independent data demonstrated that the latter was more effective in predicting habitat quality.Survey costs varied considerably but, although the more precise methods were more costly per site, they were the most cost‐effective because fewer sites were required for a given level of precision.The problems associated with soft‐water sites are discussed in terms of factors affecting site carrying capacity; and selection of methods is briefly considered in the light of current management practise.
The effects of the Kielder scheme on fisheries
Authors: Cave J. D. 
Published: January 2006

The scheme is briefly described. The success of the Kielder and Bakethin reservoir fisheries is examined. The poor condition of trout in Kielder reservoir is considered in relation to physical and chemical factors including water turbidity, low nutrient levels and the location of the reservoirs.The performance of Kielder hatchery and the difficulties of collecting broodstock of Tyne origin are described.The effects of water releases from Kielder reservoir upon the salmon, Salmo salar L., and brown trout Salmo trutta L., fisheries within the River North Tyne and examined. Aspects considered include modified water temperature regimes, water chemistry and the magnitude and timing of releases for river regulation and generation of hydroelectric power.The problems associated with fish passage at Riding Mill weir, the point of water transfer to the River Wear and River Tees, are examined and the progress of inter‐river transfers is described.
An alternative concept to home range theory with respect to populations of cyprinids in major river systems
Authors: Linfield R. S. J. 
Published: January 2006

Homing behaviour in cyprinid species has been demonstrated by a number of research workers during the past 35 years. The British work has been principally conducted through tank experimentation with roach, gudgeon and minnows, but limited field data indicating home range behaviour have also been published. Evidence is now presented, from a fish population assessment and management programme covering 6000 km of river fisheries in the Anglian region of eastern England, to suggest that home range mechanisms do not play a significant role in the overall stock dynamics of cyprinid species in major river systems.An alternative hypothesis which fits the range of observed circumstances more closely is described, based on a perception of cyprinid communities as totally mobile populations influenced predominantly by river flow characteristics and behavioural responses to flow and seasonal temperature factors. This concept is illustrated with a sequential series of schematic diagrams of a river catchment in which the key factor of infinitely variable movement patterns interspersed with periods of passive downstream displacement (negatively size‐related) is modified by increasing degrees of interference by river structures.The implications of the alternative concept to the management of riverine fish populations is discussed and alternative strategies to the traditional style cyprinid stockings illustrated within the paper are suggested which do not rely on home range mechanisms.
The possibilities of improving catchable fish stocks in lakes undergoing eutrophication
Authors: Bnińska M. 
Published: January 2006

The area of Mazurian Lakeland is the biggest lake concentration in Middle Europe. Its lakes are subjected to various man‐made impacts and disturbances, resulting in many changes in the aquatic environment and the fish stocks. Most frequently these changes are typical of the process of accelerated eutrophication, and are connected with undesirable succession in the fish stocks. Generally, predatory species, which naturally regulate the stock and maintaiil its balance, disappear from the environment, as do other valuable fish species, e.g. coregonids. At the same time food resources (weed fishes, plankton) for those species develop abundantly.Assessment of the management of lakes by one of the State Lake Fish Farms located in Mazurian Lakeland is presented against a background of various man‐made influences on the aquatic ecosystems in this region. The State Fish Farm under study manages 56 lakes of total area over 5800 ha. For each of these lakes detailed records were available of the commercial catches of particular species and their artificial stockings over a period of 31 years. These, their trends and inter‐relationships have been analyzed. Artificial stockings represented one of the best methods of counteracting adverse changes taking place in the fish stocks, with a simultaneous utilization of the productive potential of the lakes. Against this background, forecasts are made of the expected changes, and basic approaches to the proper management of the fish stocks are suggested.
The reproductive cycle of yellowfin bream, Acanthopagms australis (Günther), with particular reference to protandrous sex inversion
Authors: Pollock B. R. 
Published: January 2006

Yellowfin bream, Acanthopagrus australis, of all age classes were collected from Moreton Bay, Australia. The species possessed typical sparid ovotestes in which the testis and ovary occur in separate zones. During the spawning period (June‐August) juveniles, functional males and functional females could be distinguished by the macroscopic appearance of the gonad. The sex ratio of males to females decreases with age, indicating protandrous sex inversion.Histological and structural study of the ovotestis showed all fish have previtellogenic cells in the ovarian zone but only juvenile and male fish have developing spermatogenic cells in the testis. Most juveniles become functional males by the age of two years but a small proportion of juveniles develop directly into functional females (primary females). Protandrous sex inversion commences after the spawning period when male fish appear with spermatozoa and no other spermatogenic cells in the testis. During the period November‐January male fish with no spermatogenic cells are common and a reduction in size of the testis occurs so that by March‐April the ovotestis becomes structurally and histologically similar to the female ovotestis. Some fish remain functional males during their whole life‐history (primary males). In functional females vitellogenic cells are present in the ovary only during the spawning period and the testis remains very small in size.
Gastric emptying and the return of appetite in juvenile turbot, Scophthalmus maximus L., fed on artificial diets
Authors: Grove D. J. , Moctezuma M. A. , Flett H. R. J. , Foott J. S. , Watson T. , Flowerdew M. W. 
Published: January 2006

Gastric emptying time in Scophthalmus maximus, when fed friable artificial pellets based on fishmeal, is composed of two phases:(a) a delay time (td) during which the meal forms a bolus and which shortens with temperature, and(b) an emptying phase (duration tend) which varies with meal size (S), body weight (W) and temperature (71 according to:
image

(where tend is in h, S is in g, W is in g and T is °C). During the emptying phase, stomach contents decrease curvilinearly according to:
image

(where St, & So is in g and t is in h) in which the instantaneous digestion rate, K, varies with fish weight and temperature as:
image

Food pellets were prepared which remained separate and did not form a bolus in the stomach; K increased if a given meal size was subdivided to increase surface area. If meal size was increased by ingestion of identical pellets, K decreased. After a satiation meal, appetite in young turbot returns in direct relation to the degree of stomach emptiness. When food is regularly available, young turbot feed steadily at a rate which maintains their stomachs at c. 85% maximum fullness. When trained to use demand feeders, the fish interact as a group to feed rhythmically, but feeding rate falls 33% to only two‐thirds of the previous rate since stomach fullness, and hence digestion rate (g h−1), is maintained at a lower level. Reduction in dietary energy density below 1 kCal g−1 increases gastric emptying rate and the turbot demonstrate partial compensation by increasing food intake. On energy‐rich diets, protein nitrogen and energy assimilation efficiencies remain high (97 5% and 91% respectively) irrespective of feeding rate and frequency.
Exercise training and the stress response in rainbow trout, Salmo gairdneri Richardson
Authors: Woodward J. J. , Smith L. S. 
Published: January 2006

Plasma levels of catecholamines, cortisol, and glucose were monitored in rainbow trout during a 6‐week forced swimming exercise programme. Compared to resting non‐exercised controls, resting trained fish had lower levels of epinephrine, norephinephrine, cortisol, and glucose during the last 3 weeks of training. Initially, trained fish that were swimming had higher levels of epinephrine than resting trained fish. After 2 weeks of exercise, swimming did not significantly elevate epinephrine levels in trained fish. Glucose levels were consistently greater in swimming fish than in resting fish. At the end of the training period, exercised trout had lower (15–20%) oxygen consumption rates while resting or swimming than unexercised fish.After a 5‐month forced swimming exercise programme plasma levels of catecholamines and glucose were monitored in trained and untrained cannulated rainbow trout after 2 min of mild agitation. Trained fish showed an immediate (within 1 min) increase in the levels of epinephrine, but not norepinephrine and a delayed (within 15 min) increase in the levels of plasma glucose. Epinephrine levels returned to pre‐stress levels within 15 min. Untrained fish had no significant increase in the plasma levels of norepinephrine, epinephrine, or glucose.
The induction of spawning behaviour in Puntius gonionotus (Bleeker) by treatment with prostaglandin PGF2α
Authors: Liley N. R. , Tan E. S. P. 
Published: January 2006

Groups of Puntius gonionotus were brought into breeding condition by treatment with extracts of homoplastic pituitary material. Spawning in P. gonionotus includes a number of distinctive features which appear to be adaptations to reproduction in a riverine habitat. These features include the absence of a specific substrate requirement, the production of non‐adhesive, buoyant eggs, an elaborate circling display by the male, and a long spawning run during which gametes are dispersed across the current.Spawning activity began 3–4 h after treatment with pituitary material. The relatively sudden increase in female responsiveness and attractiveness to males appears to coincide with the occurrence of ovulation. It is hypothesized that at this time the female releases a chemical signal which attracts and excites the male. Females participate in a number of spawning runs over a period of 30 min, thereafter female activity decreases rapidly.Injections of a prostaglandin (PGF2a) were effective in inducing spawning activity in non‐gravid females. This finding provides support for the hypothesis, based on work with goldfish, Carassius auratus, that prostaglandin provides a link between periovulatory events in the ovary and the brain mechanism governing spawning activity.
Reproductive behaviour and early development of the Drysdale hardyhead, Craterocephalus sp. nov. (Pisces: Atherinidae), from the Alligator Rivers System, Northern Territory, Australia
Authors: Semple G. P. 
Published: January 2006

Craterocephalus sp. nov. showed sexual dimorphism in body shape during the breeding season. Pairing occurred during daylight with a single release of eggs amongst submerged vegetation between sunrise and the early afternoon on the same day. The eggs were demersal, adhesive, spherical (0.87–0.96 mm diameter) and had 12 adhesive filaments (0.5–1.5 mm long) at the animal pole. Approximately 24 oil droplets (0.02–0.08 mm diameter) persisted throughout egg and larval development. Hatching occurred 155–160 h after spawning at 25–27° C.The yolk‐sac larvae were 3.85–3.95 mm notochord length at hatching and began feeding at the surface after absorption of the yolk (3–12 h after hatching). All fin rays were developed in 9.4 mm standard length fry, which moved from midwater to feed on the substrate. Aquarium reared fish first spawned at 30 mm s.L. when 165 days of age.Features of Craterocephalus reproduction, as they relate to a specific survival strategy, are briefly discussed.
The glucose and lactate kinetics of American eels, Anguilla rostrata (LeSueur), under MS 222 anaesthesia
Authors: Cornish I. M. E. , Moon T. W. 
Published: January 2006

Glucose and lactate kinetics were examined in fed and food‐deprived American eels, Anguilla rostrata (LeSueur), under MS 222 anaesthesia (AE). These values are compared to free‐swimming, non‐anaesthetized animals (FSE) reported previously (Cornish & Moon, 1985). The AE group demonstrated a steady but minor hyperglycemia during the 5‐h experiment and significant decreases in both glucose turnover and metabolic clearance rates compared to the FSE groups. Food‐deprivation further depressed these kinetic parameters.Blood lactate continuously increased during the experiment, reaching values 300 times (fed) and 100 times (food‐deprived) higher than the similar FSE groups. Consistent with these higher concentrations, rates of lactate appearance in and disappearance from the blood generally increased with anaesthesia.This study supports the view of Soivio et at. (1977) that MS 222 acts as an asphyxiant. The associated metabolic disruptions are consistent with a reduction in oxidative in favour of anaerobic tissue metabolism. The specific changes in glucose and lactate parameters reflect the nervous and hormonal disruptions occurring with anaesthesia. These studies urge caution in the interpretation of data using an anaesthetized fish preparation.
The effects of carnitine on the growth of sea bass, Dicentrarchus labrax L., fry
Authors: Santulli A. , D'Amello V. 
Published: January 2006

Carnitine treatment has an appreciable effect on the hatchery‐reared sea bass, Dicentrarchus labrax, fry.The administration of the laevorotatory isomer (1‐carnitine) which is engaged in the transport of the acyl and acetyl groups through the mitochondrial membrane, stimulating lipid metabolism, increases the growth rate and the protein content of the treated fry.The dextrorotatory isomer (d‐carnitine), which is an antagonist of the 1‐carnitine, has an opposite effect on the growth and metabolism of the treated fry.