bluuebunny/crossref_metadata_2025 huggingface dataset:
Communities of parasites of freshwater fish of Jersey, Channel Islands
Authors: Kennedy C. R. , Laffoley D. d'A. , Bishop G. , Jones P. , Taylor M.
Published: January 2006

The parasite faunas of 12 species of freshwater fish from 17 localities on the island of Jersey were examined. Comparison of the species composition, number, diversity and equitability of the parasite fauna of each species of fish in each locality revealed that community diversity was always low, that most communities were dominated by a single species of parasite, and that community similarity between host species, and often between sites, was generally low. This was not related to unavailability or distribution of potential, invertebrate, intermediate host species, but appeared to be due to chance colonization events. With two exceptions, little exchange of parasites took place between host species, despite vacant niches in the parasite communities and the absence of competitors, and normal parasite specificity was maintained. Comparison of the parasite communities with those on other oceanic islands suggests that they are poorer than would be predicted by island biogeographical theory, and that this is not a very good predictor of parasite community richness on oceanic islands.
Some mechanical and morphological properties of the chorions of marine teleost eggs
Authors: Davenport J. , Lønning S. , Kjørsvik E.
Published: January 2006

The eggs of plaice, Pleuronectes platessa, lumpsucker, Cyclopterus lumpus, and capelin, Mallotus villuses, were investigated. Chorion strength was measured in three ways: by tearing isolated chorions, by bursting eggs, and by penetrating eggs with a fine needle. The results obtained showed that tearing resistance and bursting pressure (which both rise after activation of eggs in sea water) are closely related to one another, both reflecting resistance to circumferential tension. Penetration pressure (corresponding to resistance to radial penetration, i.e., hardness in the materials sense) also rises, but the time‐scale of the rise differs from that of bursting resistance, particularly in the case of capelin eggs which become ‘hard’ in the sense that they resist high bursting loads, but have a ‘soft’ chorion which does not resist penetration. Differences in chorion strength between species, and alterations in chorion strength during egg development within species, are related to morphological features and changes.
Changes in blood cell composition of the brown trout, Salmo trutta L., during the spawning season
Authors: Pickering A. D.
Published: January 2006

Differential blood cell counts were monitored in three different strains of brown trout through three separate spawning seasons. A consistent elevation in the number of circulating erythrocytes was observed in sexually mature male fish (compared with immature fish of either sex) during October‐December of each season. A marked lymphocytopenia also occurred during October in mature fish of both sexes with lymphocyte numbers still being significantly depressed as late as March the following year. It is concluded that the use of haematology as a technique for assessing the state of health of salmonid fish must take into account the sex and state of maturation of the fish. The possible consequences of changes in haematology during sexual maturation are discussed in terms of respiratory function and defence against pathogenic challenge.
The reproductive biology of a tropical cyprinid, Hampala macrolepidota (Van Hasselt), from Zoo Negara Lake, Kuala Lumpur, Malaysia
Authors: Abidin A. Z.
Published: January 2006

From a study on some aspects of the reproductive biology of the tropical cyprinid Hampala macrolepidota (Van Hasselt) in Zoo Negara Lake, Kuala Lumpur, Malaysia, analyses of the maturity stages, gonadosomatic indices and oocyte diameter patterns show that this fish is able to spawn throughout the year. However, physicochemical and environmental factors determine the actual spawning time of this fish. Spawning activity is associted with decreasing temperatures and daylengths, rising water levels and increasing turbidities. Spawning is protracted and coincides with the rainy season which extends from November to March the following year.
Distribution of the flagellate Hexamita salmonis Moore, 1922 and the microsporidian Loma salmonae Putz, Hoffman and Dunbar, 1965 in brown trout, Salmo trutta L., and rainbow trout, Salmo gairdneri Richardson, in the River Itchen (U.K.) and three of its fish farms
Authors: Poynton S. L.
Published: January 2006

The occurrence of Hexamita salmonis Moore, 1922 and Loma salmonae Putz, Hoffman and Dunbar, 1965 was investigated at 10 sites on the R. Itchen (five for brown trout only, three for rainbow trout only, and two for both brown trout and rainbow trout) and at three of its nine fish farms (two for rainbow trout, one for brown trout). Hexamita salmonis was recorded in brown trout from three river sites and the farm, and in rainbow trout from both farms and four river sites. Prevalence of Hexamita salmonis in farmed rainbow trout was higher than in farmed brown trout and was consistent with the former species being more susceptible to infection. H. salmonis was at significantly higher prevalence in rainbow trout from farm no. 5 than farm no. 2 for three size classes of fish. In wild brown trout and feral rainbow trout, the highest prevalences of H. salmonis were recorded at sites in the vicinity of farm no. 2. This distribution was consistent with an area of naturally high infection levels, and with infected fish unintentionally released from farm no. 2 serving as a source of infection, the infection subsequently becoming established in the river fish. Loma salmonae was recorded in wild brown trout and in rainbow trout from both farms. This appears to be the first recording of this parasite from British salmonids and also the first recording of the parasite from brown trout. The distribution of the parasite (particularly the prevalence being higher at farm no. 2 than farm no. 5) was consistent with it being introduced into the R. Itchen via rainbow trout from farm no. 2 (and probably no. 3) much of whose stock derived from imported Californian ‘Shasta’ rainbow trout.
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 relationship between feeding preferences and consumption rates in grass carp and grass carp × bighead carp hybrids
Authors: Wiley M. J. , Pescitelli S. M. , Wike L. D.
Published: January 2006

The relationship between food preference hierarchy and consumption rate was examined for the grass carp, Ctenopharygodon idella, and its Fl hybrid (grass carp × bighead carp). Preferences of both types of fish were similar, although hybrids consumed vegetation at a much lower rate. For both, relative preference in feeding trials with mixed plant species was significantly correlated with consumption rate in monospecific feeding experiments. No correlations were found between preference and caloric content, protein content or relative water content. The hypothesis is proposed that preference hierarchies reflect relative handling times of different food types and that these fish maximize ‘through‐put’ by preferentially consuming plant species which can be most rapidly ingested.
Effect of orally‐administered 17α‐methyltestosterone on spermatogenesis in immature milkfish, Chanos chanos Forsskal
Authors: Lee C. S. , Weber G. M. , Tamaru C. S.
Published: January 2006

Diets containing 17α‐methyltestosterone (17α‐MT) were fed to milkfish, Chanos chanos, both during the spawning season (experiment 1) and after (experiment 2). The daily dosage of 17α‐MT per kg of body weight was either 25 mg or 12.5 mg in experiment 1, and either 12.5 mg or 6.25 mg in experiment 2. The fish in both experiments were smaller than the minimum mature size previously reported. After 12 weeks of treatment, the treated fish had GSIs that were four times higher than the control fish in both experiments. Histologically, the testes of the control fish had only spermatogonia, in contrast to spermatozoa in the treated fish. However, no male possessed running milt. So 17α‐MT induced spermatogenesis but not spermiation in the immature‐sized milkfish.
Renal glomerular evolution in Antarctic notothenioid fishes
Authors: Eastman J. T. , Devries A. L.
Published: January 2006

Light and electron microscopy were used to document the degree of glomerular development in 10 species of Antarctic notothenioid fishes. When combined with results of previous studies, data revealed that 16 of 20 species inhabiting subzero sea water were aglomerular. One subantarctic and two temperate species were pauciglomerular, and an additional temperate species had a moderate number of glomeruli. Renal corpuscles were variable in number and diameter among the pauciglomerular species, and most had few patent glomerular capillaries. Radiolabelled markers indicated that the glomerular filtration rate was low in the pauciglomerular Notothenia angustata, ranging from 0.005 to 0.124 ml h−1 kg−1 in eight specimens. Arterial perfusion of Microfil demonstrated that arteries supplying aglomerular and pauciglomerular kidneys were confined largely to the periphery of the organ, and glomerular capillaries were absent or few in number. As ancestral notothenioids probably had glomerular kidneys, data from 20–25% of the fauna suggest that there has been an evolutionary loss of glomeruli in many species. The pattern of glomerular reduction is consistent with the hypothesis that the selective advantage of aglomerularism is in the urinary conservation of small molecular weight antifreeze glycopeptide compounds that are vital to survival in sub‐zero Antarctic waters.
Distribution of metacercariae of Centrocestus formosanus (Trematoda: Heterophyidae) on the gills of Aplocheilus panchax
Authors: Madhavi R.
Published: January 2006

The metacercariae of Centrocestus formosanus (Nishigori 1924) occur on the gills of freshwater fishes in association with blood vessels. The microecology of the metacercariae on the gills of the cyprinid fish Aplocheilus panchax (Ham. & Buch.) was investigated. The cysts showed a preference for anterior gills and for the dorsal section of each gill. Variations in the density of infection, season and size of the fish do not affect the spatial distribution of metacercariae. It is presumed that ventilation water currents spread the cercariae onto the anterior gills and then the cercariae actively select the preferred habitat.
A review of competitive resource sharing under constraints in sticklebacks
Authors: Milinski M.
Published: January 2006

The best strategy for an animal competing intraspecifically for food depends on its relative competitive ability, its needs, and on the strategies its competitors are using. Three different investigations using threespined sticklebacks, Gasterosteus aculeatus, as predators and Daphnia or Tubifex worms as prey are reviewed: (1) six sticklebacks differing in competitive ability compete for two food patches, of which one is twice as profitable as the other; (2) two sticklebacks differing in competitive ability compete in one patch for two types of prey, of which one is three times as profitable as the other; (3) parasitised and healthy sticklebacks have to decide alone, and in competition with each other, how close they dare approach on their own to a live predator waiting close to profitable food. The best strategy from the point of view of the stickleback is different from that of its parasite. The two parasite species studied, Schistocephalus solidus and Glugea anomala, ought to influence their host's behaviour in opposite directions.
Behaviour of the abyssal grenadier, Coryphaenoides yaquinae, monitored using ingestible acoustic transmitters in the Pacific Ocean
Authors: Priede I. G. , Smith K. L.
Published: January 2006

Scavenging grenadier fishes, Coryphaenoides yaquinae, were tracked with ingestible acoustic tags at 5800 m depth in the central North Pacific. A free‐fall vehicle comprising a video camera and recording system together with a hydrophone, ultrasonic acoustic receiver and recorder was deployed on the sea bed. Special acoustic transmitters (75 kHz) were wrapped in bait and attached below and in view of the camera. Grenadiers were observed to ingest the baited transmitters and move away to ranges of over 100 m within 5h, some returning several times to within range of the receiving system. Voluntary ingestion of transmitters by this grenadier demonstrates that an inacessible population can be studied and provides a basis for development of automated tracking systems for long‐term monitoring of individual deep‐sea fish.
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.
Electrophysiological abnormalities produced by ammonium in isolated perfused brook trout, Salvelinus fontinalis, hearts
Authors: Bubien J. K. , Meade T. L.
Published: January 2006

Electrocardiographic (ECG) abnormalities and arrhythmias have been observed in hyperammonemic patients and in animals injected with ammonium salts. Ammonium is excreted directly into the environment by fish, and it is a potent fish toxin, but the effects of ammonium on the cardiovascular system of fish are unknown. This study investigated the cardiotoxic effects of ammonium on isolated perfused fish hearts. These were compared with ammonium‐induced cardiac electrophysiological abnormalities observed in humans and other experimental animals. Isolated perfused fish hearts exhibit ammonium‐induced cardiac abnormalities similar to the ammonium‐induced abnormalities seen in the hearts of higher vertebrates. Therefore, we conclude that the myocardium of ammonotelic species does not possess a specialized ammonium detoxification mechanism, and that ammonium is cardiotoxic to salmonid fish.
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.
Mullet grazing on surf diatom accumulations
Authors: Romer G. S. , McLachlan A.
Published: January 2006

Grazing by southern mullet, Liza richardsoni (Smith), on surf diatoms occurring in bloom concentrations off an ocean‐exposed East Cape beach, South Africa, was investigated. Field observations and stomach content analysis demonstrated that surf diatoms taken from the air‐water interface were a principal source of food. A qualitative examination of stomach contents revealed a feeding transition from planktonic carnivore in juveniles to a diet consisting entirely of surf diatoms in larger fishes. This change in diet commonly occurred at a standard length of 50–135 mm. Fish larger than 135 mm fed entirely on surf diatoms which were ingested together with large quantities of beach sediment. Grazing on surf diatoms only took place during daylight hours. Energy, ash, protein, fat and carbohydrate content determinations indicate a high food quality of surf diatoms. It is concluded that surf diatom accumulations form a richly concentrated and reliable food source of high nutritional quality for these fish. Possible widespread grazing on surf diatoms by mullets is considered.
An incident of predation on queen conch, Strombus gigas L. (Mollusca, Strombidae), by Atlantic permit, Trachinotus falcatus L. (Pisces, Carangidae)
Authors: Jory D. E.
Published: January 2006

Atlantic permits were observed to break up and eat juvenile queen conches in an aquarium. It is suggested that this may occur in the wild more commonly than reported and may pose a threat to some conch seeding programmes.
Cytogenetics and taxonomy: considerations based on chromosome studies of freshwater fish
Authors: Bertollo L. A. C. , Moreira–Filho O. , Galetti P. M.
Published: January 2006

Several species belonging to different families of Brazilian freshwater fish are being studied cytogenetically, and the results obtained thus far have indicated interesting peculiarities. We show that karyotypic analysis, in addition to contributing to a better knowledge of the species, can also aid in their characterization, and we demonstrate the advantages of an associated cytogenetic‐taxonomic study, especially with respect to some groups of neotropical freshwater fish in Brazil.
The effects of sodium pentachlorophenate, diet and sampling procedure on amine and tryptophan concentrations in the brain of rainbow trout, Salmo gairdneri Richardson
Authors: Sloley B. D. , Hickie B. E. , Dixon D. G. , Downer R. G. H. , Martin R. J.
Published: January 2006

The response of rainbow trout (Salmo gairdneri Richardson) to sublethal levels of sodium pentachlorophenate (NaPCP) was determined by measuring brain concentrations of the amines dopamine (DA), norepinephrine (NE), 5‐hydroxytryptamine (5‐HT) and the free amino acid tryptophan (TP) using high performance liquid chromatography with electrochemical detection. Sodium pentachlorophenate had no major effect on the concentrations of the biogenic amines. Mean control concentrations (ng g−1 brain, S.E.) were: DA, 146.2, 9.9; NE, 205.8, 16.6; and 5‐HT, 110.5, 8.8. There was a significant dose‐dependent increase in TP concentration. Fish exposed to 200ng I−1 NaPCP showed a 128% increase in TP level relative to the mean control concentration of 1980 (50) ng g−1 brain. The effects of diets varying in lipid and carbohydrate content, anaesthetization with tricaine methanesulphonate or 2‐phenoxyethanol, and electroshock were also investigated. No differences between treatment groups were detected.
Lesion induction by the plerocercoid Lacistorhynchus tenuis (Cestoda) and wound healing in the striped bass Morone saxatilis (Walbaum)
Authors: Sakanari J. A. , Moserj M.
Published: January 2006

San Francisco Bay‐Delta striped bass, Morone saxatilis (Walbaum), form open lesions in response to a plerocercoid infection of Lacistorhynchus tenuis (Van Beneden, 1858) (Cestoda: Trypanorhyncha). Laboratory infection experiments showed that striped bass can be infected with the plerocercoids by ingesting infected copepods. Histological sections indicated that a cellular host response was mounted early in the infection period, and that despite the leucocytic infiltration the parasites continued to develop. However, at 3 months post‐infection some of the plerocercoids began to degenerate, and lesions formed at this time and 14 months post‐infection. Open lesions in adult striped bass collected from the field took 2 months to heal and were detectable for at least 22 months. Regeneration of the muscle tissue did not occur although the wound completely healed externally.
An aerial method of assessing spawning activity of Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., in Norwegian streams
Authors: Heggberget T. G. , Haukebø T. , Veie‐Rosvoll B.
Published: January 2006

A method using light aircraft to observe spawning activity of Atlantic salmon and brown trout in some Norwegian streams was tested between the years 1981 and 83. From the air, spawning redds of these species appear as light, oval spots in the river bottom. The method was successfully applied to most of the rivers studied, and information about numbers of redds, distribution of redds and spawning times was obtained. However, it has several limitations, the most important being that it proved to be unsuccessful in a deep river with high water turbidity. Also, during periods with high precipitation and high water level, the method cannot be used. Several quantitative and qualitative aspects of the results obtained by this technique are discussed.
Water and ion balance in hydrating oocytes of the grey mullet, Mugil cephalus (L.), during hormone‐induced final maturation
Authors: Watanabe W. O. , Kuo C‐M.
Published: January 2006

Sequential changes in water content and inorganic ion concentrations occurring in intra‐ovarian oocytes of the grey mullet, Mugil cephalus L., during hormone‐induced final maturation are described. Post‐vitellogenic oocytes have a water content of 59.4%. During final maturation, oocyte water increases rapidly to a maximum of 84.8% at oviposition. Hydration is accompanied by a relatively small increase in dry matter due to the concurrent uptake of inorganic ions and an apparent uptake of organic matter.

Net uptake of Ca2+ during hydration is negligible. Net uptake of Mg2 + and Na+ occurs in less than equimolar proportions. Net uptake of K+ and Cl− occurs in greater than equimolar proportions prior to ovulation, returning to equimolarity at oviposition. Hence, hydration results in a dilution of intracellular Ca2+, Mg2+ and Na+ to minimum concentrations at oviposition. In contrast, K+ and Cl− concentrations are slightly elevated prior to ovulation, returning to initial levels at oviposition. A 1:1 stoichiometric relationship in net uptake of K + andCl− is evident.

Intracellular osmotic pressure in post‐vitellogenic oocytes is 203.4 ± 18.0 mOsmolkg−1. Osmotic pressure rises to a peak of 421.3+ 17.3 mOsmol kg−1 prior to ovulation, then declines to 313.3 ± 15.0 mOsmol kg−1 at oviposition. This rise in osmotic pressure prior to ovulation cannot be accounted for solely on the basis of inorganic ion uptake and must be attributed to changes in intracellular concentrations of organic solutes as well. An apparent increase in non‐ash dry matter during hydration suggests that a net uptake of organic solute is involved. A relatively small organic molecule with high osmotic activity (e.g., amino acids) is implicated.
Dicing with death: predator inspection behaviour in minnow shoals
Authors: Pitcher T. J. , Green D. A. , Magurran A. E.
Published: January 2006

When shoaling minnows encounter a stalking pike, fish leave the shoal, approach the potential predator and then usually halt briefly before returning to the group. This behaviour, termed predator inspection, has been reported from encounters with both real and model pike. A description of inspection behaviour is given using data from experiments with a model pike made to approach foraging minnows with a standardised stalk. Evidence is presented that inspecting fish assess the risks involved. Individual minnows which have carried out an inspection visit to the predator model exhibit changes in behaviour on return which are contingent upon the state of the model, demonstrating that information is gained. Other fish change their behaviour after an inspector returns to the group, suggesting that information about the threat is transferred among the shoal. Possible costs of predator inspection behaviour may balance these benefits of knowledge, but require further investigation.
Seasonal variation of egg size in the sardine, Sardino pilchardus Walb., of the Saronikos Gulf: causes and a probable explanation
Authors: Daoulas Ch. , Economou A. N.
Published: January 2006

The change of egg size in sardine of the Saronikos Gulf (Greece) during the course of the spawning season is examined in relation to the changing conditions of temperature and plankton biomass. It is suggested that the intraspecific variation of egg size is an ecophenotypic rather than a genetic phenomenon, arising from the disturbance of the normal ratio between growth and differentiation rates during the oocyte stage. Assuming that a positive relation between the growth rate of the mother and the growth rate of the eggs during maturation exists, environmental or endogenous factors promoting or retarding the adult growth rate will accelerate or decrease the growth rate of the eggs in relation to the rate of differentiation, resulting in smaller or bigger eggs respectively.
Haematological and immunological changes in channel catfish stressed by handling and transport
Authors: Ellsaesser C. F. , Clem L. W.
Published: January 2006

Handling of fishes in the field or in the laboratory is frequently characterized by increased susceptibility to disease thought to be mediated by immunologic suppression. In order to ascertain if such immunologic suppression occurs after stress, we developed a laboratory model for the induction of acute handling and transport stress that could reproducibly effect both haematological and immunological changes in channel catfish. Eighteen hours after the induction of stress there was a marked lymphopenia which appeared to be the result of a reduction in the number of both T and B lymphocytes in the circulation. There was also the expected neutrophilia with increases of up to 30% of the circulating leucocytes. Studies on the in vitro immunological function of the remaining circulating lymphocytes demonstrated that cells from stressed fish could no longer respond to the mitogens LPS and ConA, nor could they undergo primary anti‐hapten antibody responses to either T‐dependent or T‐independent antigens. These losses of in vitro function could not be attributed to the presence of stress‐induced suppressor cells or to a loss or diminution of accessory cell function.
Experimental evidence for geomagnetic orientation in juvenile salmon, Oncorhynchus tschawytscha Walbaum
Authors: Taylor P. B.
Published: January 2006

Juvenile chinook salmon, Oncorhynchus tschawytscha, kept under artificial light in a rectangular holding tank aligned east/west for 18 months, showed a preferred temporal and directional orientation of 270° with respect to water flow and the source of food.

Individual fish transferred from the holding/training tank to an unfamiliar circular test arena in another room devoid of local directional cues showed a mean of means preferred unimodal orientation of 264°.

Controlled re‐introduction of individual stimuli revealed a hierarchy of orientation cues; one of these was a response to magnetism. A 90° clockwise shift in the horizontal component of the earth's magnetic field was followed by a significant change in the mean of means axial orientation, for the fish under test, from 258°/78° to 354°/174°. After restoration of the normal magnetic field the mean of means axial orientation reverted to 274°/94°.
Evidence for density‐dependent establishment and survival of Pomphorhynchus laevis (Müller, 1776) (Acanthocephala) in laboratory‐infected Salmo gairdneri Richardson and its bearing on wild populations in Leuciscus cephalus (L.)
Authors: Brown A. F.
Published: January 2006

Experimental primary and superimposed infections of Salmo gairdneri with various dosages of Pomphorhynchus laevis indicated that density‐dependent parasite establishment and survival occurred such that the number of parasites which survived to reproduce within an individual fish reached a ceiling level. The possibility that this mechanism is responsible for the generation of the observed positive relationship between the length and worm burden of Leuciscus cephalus taken from a natural population in the River Severn, England is discussed in the light of these experiments.
Environmental control of salinity preferences in four sympatric species of sticklebacks: Gasterosteus aculeatus, Gasterosteus wheatlandi, Pungitius pungitius and Apeltes quadracus
Authors: Audet C. , Fitzgerald G. J. , Guderley H.
Published: January 2006

Salinity preferences of four sympatric species of sticklebacks (Gasterosteus aculeatus, Gasterosteus wheatlandi, Pungitius pungitius, Apelles quadracus) were studied after acclimation to different regimes of photoperiod and temperature. The results indicate that photoperiod and temperature influence salinity preferences of G. aculeatus, G. wheatlandi and A. quadracus but that they are virtually without effect in the case of P. pungitius. Moreover, the overall photoperiod effects on salinity preferences are in accordance with the migratory movements of G. aculeatus and A. quadracus. The effect of temperature was more difficult to analyse because of its unnatural timing. It is clear, however, that temperature is involved in the regulation of salinity preferences of G. aculeatus and perhaps of G. wheatlandi. The relative importance of external factors in the adjustment of salinity preferences differed for the four species. However, the results suggest that for G. aculeatus and A. quadracus salinity preferences are an important component of the orientation mechanisms used during their seasonal migrations.
Plasma insulin levels during the spawning migration of the pink salmon, Oncorhynchus gorbuscha
Authors: Plisetskaya E. M. , Donaldson E. M. , Dye H. M.
Published: January 2006

Plasma insulin concentration was measured by homologous radioimmunoassay in male and female pink salmon. Oncorhynchus gorbuscha, during spawning migration in the Fraser and Thompson Rivers, British Columbia. Although the fish ceased feeding prior to entering fresh water, plasma levels of insulin remained stable (males) or even elevated (females) during the final stages of oogenesis and spermatogenesis, decreasing thereafter. Mean concentrations ranged from 0–69 to 1.24 ng ml−1 in males and from 0.33 to 0.88 ng ml−1 in females. At all stages in the anadromous migration where a significant difference in plasma insulin levels between the sexes was observed, males had higher concentrations than females.
Long‐term changes in the prevalence of two helminth parasites (Cestoda: Trypanorhyncha) infecting marine fish
Authors: Mackenzie K.
Published: January 2006

Changes in prevalence of the plerocerci of Grillotia angeli Dollfus, 1969 in mackerel, Scomber scombrus L., and of Lacistorhynchus sp. in herring, Clupea harengus L., were recorded over periods of eight years (1978–1985) and 11 years (1974–1984), respectively. Data were collected from 21 year classes of mackerel in an area to the south‐west of Britain and Ireland and from seven year classes of herring in the eastern North Sea. Both sets of data showed sharp decreases in parasite prevalence from periods at relatively high levels to others at much lower levels. The changes in prevalence occurred at the same time in both host‐parasite systems and coincided with the end of the hydrographic phenomenon known as the mid‐70s salinity anomaly. Possible explanations for the changes which are discussed include changes in abundance of first intermediate and definitive hosts, variations in host year class strength, changes in hydrographic conditions and changes in host diet.
Migrations of sea trout, Salmo trutta L., from the Vardnes river in northern Norway
Authors: Berg O. K. , Berg M.
Published: January 2006

During the periods 1956–1963 and 1967–1970 traps were operated to catch upstream‐ and downstream‐migrating sea trout, Salmo trutta L. A total of 15 788 sea trout were tagged, using Carlin tags. The number of recaptures made in the traps was 4481, of which 1796 were recaptured more than once.

The distribution of the 2122 recaptures in the sea provides a picture of the sea‐migration pattern. Of the sea recaptures, 52.8% were reported as within a distance of 3 km from the river mouth, compared to 0.7% more than 80 km away. All the different size‐groups of sea trout were represented among both the long‐distance and the short‐distance migrants. The results of this study of sea trout migrations are discussed in relation to the published results for Atlantic salmon, Salmo salar L., and sea charr, Salvelinus alpinus (L.), from the same river.

The four highest values recorded for mean distance of daily travel away from the river were 20, 8, 8 and 6km day−1 by smolts and 6, 6, 5 and 5km day−1 by larger‐sized sea trout.

Recaptures of tagged sea trout in rivers other than the Vardnes totalled 506, of which 306 had been tagged as smolts. The calculated minimum percentage of stray is 15.5%. The proportion of sea trout from the Vardnes river that actually spawn in other rivers is not known. No significant difference in length distribution was found between the sea trout caught in the Vardnes river and those caught in other rivers. An hypothesis concerning the selective advantages of straying by anadromous salmonids living in small rivers is discussed.
Phagocytic cells in blood from rainbow trout, Salmo gairdneri (Richardson), characterized by flow cytometry and electron microscopy
Authors: Thuvander A. , Norrgren L. , Fossum C.
Published: January 2006

An in vitro assay for estimating the proportion of phagocytic cells among peripheral leucocytes from rainbow trout by flow cytometry (FCM) and fluorescence microscopy was evaluated. Data from FCM were compared with fluorescence microscopic observations and good correlation (r= 0.87) was found. The influence of various culture conditions, such as serum type, duration of incubation and temperature, on the in vitro phagocytic assay was investigated. Cultures supplemented with brown trout serum and incubated for 18 h at 19° C were considered to give optimal conditions for phagocytosis. The proportion of phagocytic cells detected in the peripheral blood leucocyte preparation was 3.3 ± 1.5% with FCM and 5.5 ± 2.4% with fluorescence microscopy. The applicability of the method was demonstrated in a preliminary study with arsenic. In a concentration of 1 μg ml−1, arsenic increased the proportion of actively phagocytic cells, but, at a high concentration, 100 μg ml−1, it decreased the phagocytic activity. Electron microscopy was used for morphological classification of the peripheral leucocytes throughout the study.
Some effects on the growth of brown trout from exposure to aluminium at different pH levels
Authors: Sadler K. , Lynam S.
Published: January 2006

Yearling brown trout, Salmo trutta L., were exposed to various concentrations of inorganic aluminium (0–3.7 μM1−1) over a pH range of 4.3–6.5 in a flow‐through bioassay apparatus using synthetic test media. Low pH, in the absence of aluminium, produced little effect on growth or survival except at the lowest pH tested (4.3). At pH less than 5.5, concentrations of total aluminium in excess of 1 μM 1−1 (27μg 1−1) were found to retard growth. The effects of a given aluminium concentration were markedly reduced at pH above 5.5.

The change in aluminium toxicity with pH must be related to changes in aluminium chemistry. When growth rates are correlated with the different aluminium species, calculated using thermodynamic equilibrium constants given in the literature, it appears that the Al(OH)2 + species is the most toxic, with a small contribution also coming from polymeric complexes.
Fermentative microbial digestion in herbivorous fishes
Authors: Rimmer D. W. , Wiebe W. J.
Published: January 2006

Two herbivorous fishes of the genus Kyphosus (family Kyphosidae) possess unique digestive tracts among fishes, with well‐developed caecal pouches and a complex gut‐resident microflora. The presence of high concentrations of volatile fatty acids in the gut confirms fermentative digestion in fishes for the first time.
The vertical and transverse distribution of larval herring in the River Blackwater estuary, Essex
Authors: Henderson P. A.
Published: January 2006

The vertical and transverse distributions of spring‐spawned larval herring were studied in the River Blackwater estuary, Essex. Sampling was undertaken during May when larval densities within the estuary were at a maximum for the year. At this time, larval lengths were in the range 7–16 mm. No clear diel pattern in the vertical distribution was found, although larval distribution at night was more even.

The tides were found to influence the vertical distribution. Surface waters (< 1.5 m in depth) were avoided during both flood and ebb tides, but used during slack water. Larval densities at ebb were higher near the sea bed than during the flood tide. It was concluded that this behaviour will tend to transport larvae into and retain them within the estuary.
The effect of sublethal endrin exposure on rainbow trout, Salmo gairdneri Richardson. II. The effect of altering serum cortisol concentrations on the immune response
Authors: Bennett R. O. , Wolke R. E.
Published: January 2006

The effect of altering serum cortisol concentrations on the immune response was elucidated in endrin‐ and non‐endrin‐exposed rainbow trout, Salmo gairdneri. Fish were immunized with 10 μg of Yersinia ruckeri O‐antigen following 30 days of treatment. The migration inhibition factor assay (MIF), plaque‐forming cell assay (PFC) and serum agglutination titres (SAG) were performed 2, 14 and 30 days post‐antigen inoculation. Endrin exposure was continued subsequent to antigen inoculation. Control fish were fed 20 and 35 mg kg−1 body weight day−1 of cortisol and metyrapone, respectively. Endrin‐exposed fish received 35 mg kg−1 body weight day−1 of metyrapone in their diet. Control fish receiving cortisol had significantly reduced MIF, PFC and SAG responses. The MIF response was completely restored in endrin‐exposed fish receiving dietary metyrapone. The PFC response and SAG titres were partially restored, 61 and 69% respectively, in endrin‐exposed fish receiving metyrapone. The results indicate that elevated serum cortisol concentration obtained in endrin‐exposed fish has a central role in repression of the immune response.
The gonadal cycle of captive white bream, Diplodus sargus (L.)
Authors: Micale V. , Perdichizzi F. , Santangelo G.
Published: January 2006

A histological study was carried out to follow gonadal changes in captive white bream during the second and third years of life. All but one individual matured as a male. Spawning was found to occur in winter. Environmental factors are likely to have influenced the reproductive activity of the captive fish.
The palatine bone and its associations in gadoid fishes
Authors: Howes G. J.
Published: January 2006

The articulation of the palatine bone in gadoid fishes has been thought of as a specialization of that group. It is shown that there are, in fact, three principal types of articulation, two of which are shared with other gadiform groups. The type of palatine articulation in other paracanthopterygians is briefly described and compared with that of various acanthopterygians. The supposed relationships of some gadoids are commented upon in the light of the specialized nature of some types of palatine articulation.
Morphological and sensory specializations of five New Zealand flatfish species, in relation to feeding behaviour
Authors: Livingston M. E.
Published: January 2006

The morphology of the feeding apparatus and sensory systems of flatfish species Rhombosolea plebeia (Richardson, 1843), Rhombosolea leporina Günther, 1862, Peltorhamphus novaezeelandiae Günther, 1862, Pelotretis flavilatus Waite, 1911 (f. Pleuronectidae) and Arnoglossus scapha (Forster, in Bloch & Schneider, 1801) (f. Bothidae) are described. The four pleuronectid species have asymmetric jaws and non‐toothed gill rakers typical of benthic‐feeding flatfish, while the bothid has symmetric jaws and toothed gill rakers typical of midwater‐feeding flatfish. R. plebeia, R. leporina and P. novaezeelandiae have extensive external taste bud systems which facilitate non‐visual prey location. External tastebuds are lacking in P. flavilatus and A. scapha; however, these two species have relatively large, prominent eyes which facilitate visual prey location. The lateral line is well‐developed in all five species, but R. plebeia, R. leporina and particularly P. novaezeelandiae have additional free neuromasts on their blind sides, which probably assist in prey location.

The feeding habits of these flatfish species closely reflect their morphological and sensory specializations. A detailed feeding study in Wellington Harbour, New Zealand showed that R. plebeia, R. leporina and P. novaezeelandiae have closely overlapping diets consisting of largely sedentary or inactive invertebrates living in the bottom sediments. In contrast, P. flavilatus and A. scapha have specialized diets of one or two species only. While the latter two species differ in that P. flavilatus is a benthic feeder and A. scapha is pelagic feeder, both are visual feeders and therefore more specialist than the other three species.
Eye migration and cranial development during flatfish metamorphosis: a reappraisal (Teleostei: Pleuronectiformes)
Authors: Brewster B.
Published: January 2006

The literature concerning eye migration and cranial development during flatfish metamorphosis is briefly reviewed and found to give rise to five hypotheses to account for the phenomenon. The cranial morphology of specimens of Soleidae, Pleuronectidae, Scophthalmidae and Bothidae in pre‐metamorphic, metamorphic and post‐metamorphic stages are described. The mechanisms by which eye migration and cranial development occur are discussed and some aspects of pleuronectiform relationships are briefly commented on.
Haemolytic activity in the serum of brown trout, Salmo trutta
Authors: Ingram G. A.
Published: January 2006

Brown trout serum contains a natural, spontaneous, antibody‐independent lytic activity and a haemolysin antibody complement‐mediated lytic activity against unsensitized and trout antibody‐sensitized sheep erythrocytes, respectively. The use of various activators and inactivators of the mammalian complement system demonstrated that trout serum possesses complement or complement‐like components similar in activity to those present in the classical and alternative pathways found in mammals. A single injection of trout with sheep erythrocytes stimulated the production of antibody‐secreting cells in lymphoid organs and increased the levels of natural haemolysins. A second injection of sheep erythrocytes further raised the haemolysin values and antibody‐secreting cell counts. Serum complement from homologous or closely related fish species was more effective for use in the haemolysin and antibody‐secreting cell assays than that from heterologous sources, except guinea pig. Based on physico‐chemical properties, gel filtration and immunoelectrophoretic studies, natural and induced anti‐sheep erythrocyte haemolysins were found to be similar molecules and are possibly high molecular weight IgM antibodies.
The ontogeny of gut‐associated lymphoid tissue in Oreochromis‐mossambicus
Authors: Doggett T. A. , Harris J. E.
Published: January 2006

The ontogenesis of gut‐associated lymphoid tissue (GALT) was investigated using histological procedures. Samples were taken at various time intervals to include larval, first‐feeding and juvenile stages. Whole fish and tissue samples were embedded in either paraffin wax or metha‐crylate resin and sections stained with Giemsa, periodic acid‐Schiff (PAS), methyl green pyronin (MGP) and methylene blue. GALT was first observed as individual lymphocyte‐like and macrophage‐like cells in the lamina propria, and in later stages plasma cells and granulocytes were identified. Leucocytes began to infiltrate the epithelium just prior to first feeding and then rapidly once feeding had began. By day 50, GALT was equal to that observed in the adult gut.
Effects of the pesticides atrazine and lindane and of manganese ions on cellular immunity of carp, Cyprinus carpio
Authors: Cossarini‐Dunier M.
Published: January 2006

Pesticides and metals in the aquatic environment can peturb the fish immune system and, consequently, increase their susceptibility to pathogenic agents. Lindane, an insecticide, was tested for its effects on skin graft rejection after daily administration in the food for 1 month (1000 mg lindane kg−1 food). No difference was observed from the control for the first set of graft rejection times (8 days) or for the second set of graft rejection times (5 days), even if the lymphoid organs were highly contaminated with lindane. Atrazine, lindane and manganese were tested for their effect on in vitro phagocytosis of Yersinia ruckeri and zymosan (yeast extract) by pronephric and splenic macrophages. Neither pesticide had any effect on macrophage phagocytosis at concentrations up to their limit of solubility in water. Manganese ions, in the range 6.25–50 ppm, had a strong enhancing effect on phagocytosis of Y. ruckeri, as did zymosan, but only at a concentration of less than 6.25 ppm.
Effects of diet, sham‐immunization and bleeding on the immune response kinetics for two strains of Cyprinus carpio
Authors: Salomoni C. , Fiorentino M. , Palenzona D. L.
Published: January 2006

The effects of diet and experimental procedures for immunization and bleeding on the immune responsiveness of two strains of Cyprinus carpio were investigated. In addition, the relationship between the genetic structure of these fish, based upon the pattern of scaling, and antibody production was studied. The antibody response to sheep red blood cells (SRBC) was assessed by direct haemagglutination. The control titres for both uninjected and sham‐immunized fish, using phosphate buffer saline, were evaluated for each treatment. The results show that diet and multiple bleeding influence the antibody response kinetics to SRBC. The observed differences are dependent upon the strain from which the serum is isolated. Furthermore, the change in antibody titre in the controls is negligible when compared to the increase observed after immunization with SRBC.
Bacterial kidney disease: the potential role of soluble protein antigen(s)
Authors: Turaga P. , Wiens G. , Kaattari S.
Published: January 2006

Soluble protein antigens, isolated from the supernatants of Renibacterium salmoninarum cultures, have been found to suppress the in vitro antibody reponses of coho salmon, Oncorhynchus kisutch, lymphocytes and to be associated with decreasing haematocrit values in vivo.