bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterns in the composition and richness of helminth communities in brown trout, Salmo trutta, in a group of reservoirs
Authors: Hartvigsen R. , Kennedy C. R.
Published: April 2005

Helminth community composition and richness were studied in brown trout, Salmo trutta, in 10 reservoirs of broadly similar age and characteristics situated close to each other in a well‐defined region of south‐west England. Communities were compared using cluster and ordination analyses, and possible correlations between helminth richness and a number of environmental variables were investigated. The hypothesis that the helminth communities should show high degrees of similarity and that large differences between reservoirs and a high degree of clustering would be unrecognizable was refuted. Levels of community similarity were low and comparable to those determined for helminths in salmonids in natural lakes. Trout in some reservoirs exhibited very distinctive helminth faunas and clustering of reservoirs was apparent. No single factor, including reservoir size and presence of piscivorous birds, had a predominant influence on community richness or composition but rather a multiplicity of local factors was believed to influence these parameters. The results indicate that local factors promoting distinctiveness have a greater influence on the composition and richness of fish helminth communities in lakes and reservoirs than do regional factors promoting similarity.
A unique surface pattern and micropylar apparatus in the eggs of Luciocephalus sp. (Perciformes, Luciocephalidae)
Authors: Riehl R. , Kokoscha M.
Published: April 2005

A hitherto undescribed Luciocephalus species was bred in captivity for the first time. The male mouthbrooders spawned about 80 slightly pear‐shaped eggs with a diameter varying from 2‐2 to 3‐4 mm. The enveloping zona radiata measured 15 μm in thickness. In the SEM the outer surface of the zona radiata showed a pattern which is unique among all teleosts studied to date. Many of the numerous, virtually parallel ridges extended from the vegetal to the animal pole. There they spiralled towards the micropyle and terminated in its pit. The role of such a surface pattern as a sperm guidance system was discussed.
Seasonal studies of the biology of Achtheres percarum in perch, Perca fluviatilis, from four Finnish lakes over a 3‐year period
Authors: Valtonen E. T. , Tuuha H. , Pugachev O. N.
Published: April 2005

Achtheres percarum infection on the gills of perch Perca fluviatilis was studied from four lakes in central Finland in monthly or bimonthly samples of fish during a 3‐year period. The highest prevalence and intensity of infection (30%, 0.7 copepods/fish) were found in the oligotrophic, unpolluted Lake Peurunka and the lowest (6%, 0.1 copepods/fish) in the eutrophic and polluted Lake Vatia. According to hierarchical loglinear models the prevalence of A. percarum infection was related to the lake, but not to the year. However, when logit models were constructed such that two ‘seasons’ (‘cold’ and ‘warm’ periods) were included, it was apparent that the year also influenced the prevalence of A. percarum, but only during the ‘warm’ period of the year. Achtheres percarum had an age dependent relationship only in Lake Peurunka, where the infection increased with increasing age of the fish. Some developmental stages of A. percarum parasitizing the gills of perch are described. Data on the seasonal occurrence of A. percarum developmental stages are given and it is suggested that at least two generations are produced annually.
Structure and volume of the hoki, Macruronus novaezelandiae (Merlucciidae), swimbladder
Authors: Jay C. V.
Published: April 2005

The structure of the hoki, Macruronus novaezelandiae, swimbladder is similar to well‐developed swimbladders in other deep water fish that undergo extensive diel vertical migrations. The preponderance of a globular mass of submucosal tissue in the posterio‐ventral floor of the swimbladder in large individuals is an unusual feature of unknown function, but has characteristics similar to regressed swimbladders that occur in some species of the Myctophidae. Two out of three different estimates of swimbladder volume were significantly lower than ‘neutral buoyancy volume’ estimates, probably because the swimbladders were inflated artificially without accounting for their natural compliancy and internal pressure. Volume estimates from such swimbladders may reduce substantially the accuracy of target strength estimates from morphometry‐based models of the swimbladder. However, this may be a trivial consideration in acoustic surveys compared to the probable occurrence of diel and seasonal variation in swimbladder shape and volume.
Allometric growth in juvenile cod (Gadus morhua) and possible effects on cannibalism
Authors: Otterå H. , Folkvord A.
Published: April 2005

Cod juveniles of about 20 mm had the lowest potential predator: prey length ratio based on mouth gape of the predator and the body height of the prey. This implies that the cannibalistic potential is maximized in this size range.
Distribution and prevalence of Anguillicola crassus in eels from the tidal Thames catchmentb
Authors: Pilcher M. W. , Moore J. F.
Published: April 2005

Data gathered between 1988 and 1992 document the spread of the parasitic nematode Anguillicola crassus among eels in the tidal Thames catchment. Eel samples revealed a parasite prevalence ranging between 12 and 32% with a variation in intensity of infection of between one and five nematodes per infected host. Differences in the salinity regime between sampling points may be linked to the range of levels of infection in eels because of the saline tolerance limits of parasite developmental stages. The euryhaline teleost, the smelt (Osmerus eperlanus) found throughout the tidal river has been shown by others to be able to transfer nematode larval stages experimentally to large eels. Smelt found in the tidal Thames thus could possibly act as a further intermediate host to the eel population. The results support the theories proposed by previous workers that the parasite originally entered the tidal Thames via the commercial trade in live eels.
Water balance in eggs of striped bass (Morone saxatilis)
Authors: Mangor‐Jensen A. , Waiwood K. G. , Peterson R. H.
Published: April 2005

Measurements of embryonic volume revealed regulation capability before hatch. Water diffusion permeability, determined as tritiated water efflux, was found to be low, but within the range for fish eggs. The perivitelline fluid is readily interchangeable with the external medium due to a high chorion permeability to both water and salt.
Herbivory in the tilapia Oreochromis niloticus: a comparison of feeding rates on phytoplankton and periphyton
Authors: Dempster P. W. , Beveridge M. C. M. , Baird D. J.
Published: April 2005

A quantitative comparison of the grazing behaviour of young Oreochromis niloticus feeding on the planktonic cyanobacterium Microcystis aeruginosa and a periphytic community dominated by the cyanobacterium Oscillatoria sp., determined that biomass ingestion rates of fish filter‐feeding on planktonic cyanobacteria were significantly lower than those surface‐grazing on periphyton. Comparisons of published laboratory data on filter‐feeding with field data on algal ingestion rates suggest that filter‐feeding may be a relatively unimportant method of ingesting algae.
Differences in protein mobilization between ventral and dorsal parts of white epaxial muscle from fed, fasted and refed white sturgeon (Acipenser transmontanus)
Authors: Kiessling A. , Hung S. S. O. , Storebakken T.
Published: April 2005

The effect of starvation‐refeeding on protein mobilization in the lateral line, lateral (midway between lateral line and dorsum) and dorsal parts of white sturgeon (Acipenser transmonlanus) white epaxial muscle (type IIB) were compared by measuring muscle cross‐sectional fibre areas. Effects on red (type I) and pink (type IIA) muscle were also studied. Fish starved throughout the experiment (5 weeks) showed a uniform response, i.e. the cross‐sectional fibre area decreased at all sampled locations in the white muscle as well as in red and pink muscle. Fibre size in fish refed for 3 weeks after 2 weeks of fasting (S/F) was reduced mainly in the dorsal region of the white muscle. Starvation for 3 weeks after 2 weeks of initial feeding (F/S) also reduced fibre size mainly in the dorsal regions of the white muscle and in the pink muscle. The results indicate that in sturgeon exposed to short periods of low food availability, protein is utilized preferentially from trie more dorsal regions of the white epaxial muscle and from pink muscle. Protein in white muscle located closer to the lateral line and in red muscle seems to be spared. With the onset of refeeding, protein deposition occurred rapidly in pink muscle, but was delayed significantly in the dorsal part of the white muscle.
Purification of flounder (Paralichthys olivaceus) fibronectin and its localization during re‐epithelialization at a fin wound
Authors: Kurokawa T. , Suzuki T. , Funakoshi S.
Published: April 2005

Plasma fibronectin (FN) of flounder Paralichthys olivacem was purified and characterized. Flounder FN was purified by a combination of affinity chromatography using Sepharose coupled with flounder gelatin and gel filtration on Superose 6. Flounder FN was found to be a disulphide‐linked heterodimer of 220 and 230 kDa polypeptides. It had cell‐spreading activity for baby hamster kidney (BHK) cells, which was inhibited by the synthetic peptide, Gly‐Arg‐Gly‐Asp‐Ser‐Pro. In flounder explants, anti‐flounder FN antiserum distinguished fibroblast‐like cells from epithelial cells; indirect immunofluorescence showed that the fibroblast‐like cells exhibited a fibrous staining to the antiserum, but that epithelial cells did not. These results suggest that flounder FN is a homologue of mammalian FN.

The localization of FN during re‐epithelialization at the site of a severed fin was investigated. When the top of the fin was cut, epidermal cells covered the surface of the wound within 1 h. FN is detected at the wound site during epidermal cell migration, suggesting that it serves as a cell‐adhesion factor for prompt re‐epithelialization at wound sites.
The size of lipid depots‐a factor contributing to the control of food intake in Arctic charr, Salvelinus alpinus?
Authors: Jobling M. , Miglavs I.
Published: April 2005

Food intake of Arctic charr was greatest in the fish with reduced lipid depots. It is suggested that appetite declines as lipid accumulates and energy reserves become repleted, such that energy reserves are then maintained close to some set‐point.
Mature male parr buried among eggs in an Atlantic salmon redd
Authors: Sægrov H. , Urdal K.
Published: April 2005

A mature mate parr of Atlantic salmon was found buried among eggs 28 cm beneath the gravel surface in a salmon redd. Egg mortality in this egg‐pocket was considerably higher than in neighbouring egg‐pockets (52 v. 3%), presumably due to decay.
Dominance hierarchies of male green swordtails (Xiphophorus helleri) in nature
Authors: Franck D. , Ribowski A.
Published: April 2005

Swordtail males formed dominance hierarchies at shallow sites in creeks or streams and invested much time in maintaining a high rank‐order position (mean 11·1 chases per 5 min).
The embryological origin of the juxtatesticular body in jawfishes (Opistognathidae)
Authors: Rasotto M. B.
Published: April 2005

A male accessory sex organ, termed the juxtatesticular body (JTB), is located in the posterior part of the trunk, outside the coelomic cavity, lying ventral to the urinary ducts and dorsal to the urinary bladder and testes in jawfishes. Its microscopic structure is unusual for an accessory sex organ because it is highly vascularized, organized in small follicles, and ductless. The embryological origin of the JTB and the development of the urogenital apparatus was studied in juveniles of Opistognathus whitehurstii and O. maxillosus. Both sexes possess a structure located outside the coelomic cavity in the posterior part of the trunk. In females this structure showed the same histological organization as the kidney, however in males it was different and recognized as the JTB. The degree of development of the JTB followed that of the testes, being represented in youngest recognizable males only by a small mass of mesenchymal cells while it was fully developed in males with spermatogenic testes. In most immature males renal structures, such as tubules and glomeruli, were found in the dorsal part of this structure. On the basis of anatomical and cytological features a nephrogenic origin for the JTB is proposed.
Population biology and stock assessment of Pristipomoides filamentosus on the Mahe Plateau, Seychelles
Authors: Mees C. C.
Published: April 2005

The population of P. filamentosus around the periphery of the Mahe Plateau was studied using data derived from commercial handline fishing operations between November 1989 and December 1990. Sex ratio was close to one. Fork length was in the range 25.6–79.8 cm: at first sexual maturity, 36–38 cm for females and 40–42 cm for males. Spawning occurred from October to April peaking between February and April and in November.

The length (f.l., cm)–weight (kg) relationship was W=0.00005353 ×f.l.2.7004. The von Bertalanffy growth parameters, estimated from length frequency data, were K=0.2875 and Linf=81.7 cm. Mortality rates, estimated from length converted catch curve analysis, were Z=0.811, F=0.277 with M=0.534 derived from Pauly's empirical formula. Jones' length cohort analysis gave an estimate of F= 0.294 for the fully exploited part of the stock, and a density of 2.59 t km−2 for the periphery of the plateau from 75 to 150 m depth. The Lesley constant catchability model, applied to the results of intensive fishing around isolated banks, derived a mean density estimate of 2.99t km−2. The sustainable yield was estimated to be 233–268 tonnes per annum and the catch in 1990 was 200 tonnes.
Characterization of sugar moieties and oligosaccharide sequences in the distal intestinal epithelium of the rainbow trout by means of lectin histochemistry
Authors: Pajak B. , Danguy A.
Published: April 2005

Lectin histochemical study was performed on the distal intestinal mucosa of the rainbow trout. A panel of 25 biotinylated leetins for detection of sugar residues and oligosaccharide sequences of glycoconjugates on Bouin's solution‐fixed paraffin embedded sections were used as probes. The avidin‐biotin‐peroxidase complex (ABC) was used to visualize the binding sites of lectins. A rich supply of carbohydrates was detected in this gut mucosal region. Marked differences in lectin labelling of goblet cells and enterocytes (absorptive cells) probably reflect various functional activities. The results are compared with those (scarce) obtained from other teleosts. Species differences in carbohydrate residue composition may be related to various feeding habits. The roles of posterior intestinal glycoconjugates in host‐parasite interaction, macromolecular ingestion and immunological implications are discussed.
Shelter utilization by Gobius cruentatus and Thorogobius ephippiatus (Teleostei: Gobiidae)
Authors: Wilkins H. K. A. , Myers A. A.
Published: April 2005

Parameters of shelters utilized by Gobiuscruentatus and Thorogobius ephippiatus were measured, in situ, using SCUBA. Both species exhibited non‐random use of shelters, with T. ephippiatus, the smaller of the two species, utilizing significantly larger shelters than G. cruentatus. Interspecific size differences and competitive exclusion are not considered to be of major importance in the observed differential utilization of shelters. The size of shelters utilized by both species is suggested to be influenced by current velocities.
The influence of hunger on shoal size choice by three‐spined sticklebacks, Gasterosteus aculeatus
Authors: Krause J.
Published: April 2005

Single sticklebacks (Gasterosteus aculeatus) were presented with a choice between (a) a shoal and an empty compartment, and (b) two different sized shoals of conspecifics. The choice of hungry test fish (food‐deprived for 24 h and 72 h, respectively) was compared to that of fish which were fed to satiation once a day. It was hypothesized that due to the increased level of competition for food in large shoals, hungry fish would spend less time with the larger of two shoals than their well‐fed conspecifics. The results showed that there was indeed a significant trend for test fish to spend a decreasing amount of time near the compartment with the larger number of fish with increasing duration of food deprivation.
Compensatory growth and reduced maturation in second sea winter farmed Atlantic salmon following starvation in February and March
Authors: Reimers E. , Kjørrefjord A. G. , Stavøstrand S. M.
Published: April 2005

Starvation of second sea winter farmed Atlantic salmon through February and March reduced body weight by 0.10% day−1 or 6.0% during the starvation period, whereas fed fish increased body weight by 0.10 day−1 or 5.9%. When fed again during 41 days in April and May, the starved group increased weight by 22.7% (0.55% day−1) compared with a 11.4% (0.28% day−1) gain in the unrestricted control. Ultrasound determination of sex and maturity in late May showed that the incidence of maturation was reduced by 48% among females and 32% among males in the starved group, compared with the unrestricted group.
The accumulation of 137‐caesium from fresh water by alevins and fry of Atlantic salmon and brown trout
Authors: Morgan I. J. , Tytler P. , Bell M. V.
Published: April 2005

The accumulation of 137‐caesium from water by alevins and fry of Atlantic salmon and brown trout was studied, At ‘normal’ pH (∼7.4), input rates (kWF) and equilibrium concentration factors (CFeq) of 137‐caesium were four to five times greater in both species of alevins than those in the fry. Input rates and equilibrium concentration factors were consistently greater in brown trout than in Atlantic salmon. The input rate of 137‐caesium was most rapid in kidney, gill and gut of fry. The majority of the radiocaesium was, however, deposited in muscle tissue which had consistently the longest biological half‐life of 50–90 days. 137‐Caesium input was significantly reduced at low pH (∼5.0) but output rates (kFW) were little affected. It is concluded that juvenile fish are more susceptible than adults to radiocaesium accumulation from freshwater but that food is the major source of 137‐caesium in freshwater fish. The behaviour of 137‐caesium is discussed with respect to potassium.
The distribution of 0‐group flatfish in relation to abiotic factors on the tidal flats in the brackish Dollard (Ems Estuary, Wadden Sea)
Authors: Jager Z. , Kleef H. L. , Tydeman P.
Published: April 2005

The distribution of 0‐group flatfish was investigated in 1992 in the Dollard (Ems–Dollard estuary, Wadden Sea). 0‐Group plaice, flounder and sole were not evenly distributed over the sampled locations. The spatial distribution pattern of 0‐group flatfish in the Dollard changed during the investigation period. In the first week of sole presence, when the mean length of sole was 24–30 mm, salinity correlated significantly with sole density. The distribution of juvenile sole larger than 40 mm total length was affected by the elevation of the location: 0‐group sole was restricted to the sampled site with the lowest elevation. The distribution of 0‐group plaice was related to sediment: no juvenile plaice were caught at locations with more than 10% mud fraction in the sediment. The distribution of 0‐group flounder was also correlated with sediment. Later in the year, salinity correlated negatively with the distribution of 0‐group flounder. The influence of sediment composition is probably indirect and linked to the abundance of preferred food items, such as Corophium volutator. Abiotic conditions were suitable to 0‐group plaice, flounder and sole.
Distribution, growth and movement of River Usk brown trout (Salmo trutta)
Authors: Bembo D. G. , Beverton R. J. H. , Weightman A. J. , Cresswell R. C.
Published: April 2005

The River Usk catchment in South Wales supports mainly freshwater resident brown trout, with few anadromous fish. Electric fishing and netting revealed that age‐class distribution differed between main river and tributary habitats, the latter environment acting as a nursery area for young fish. Few fry were found at main river sites. Age‐class distribution also differed between tributary systems, and possible reasons are discussed. Trapping experiments indicated that trout move to main river habitat at 2+ yr. Lengths at age (back‐calculated from scale reading) were similar for main river and tributary resident fish at 1 and 2 year, but main river fish were larger at 3 and 4 yr. This habitat shift and size difference is discussed with reference to current angling regulations.
Evolutionary aspects of fish distribution: genetic variability and adaptation
Authors: Carvalho G. R.
Published: April 2005

Many species of freshwater and anadromous fish are fragmented into local populations, some of which display adaptive traits that enhance survival and reproduction in particular environments. This paper focuses on the genetic component of response to heterogeneous environments, with emphasis on how the levels and distribution of genetic diversity may influence the distribution of conspecific populations. It addresses three aspects of genetic variability and adaptation: (1) the significance of genetic variability in relation to adaptation; (2) the adaptive significance of population differentiation; (3) the effects of stocking on local adaptation. In addition to considering local adaptation in salmonids, especially in relation to the genetic consequences of stocking, examples are chosen across fish taxa, with emphasis on recent studies in the guppy, Poecilia reticulata. The significance of within‐population genotypic variance in fitness traits, genetic load and outbreeding depression is discussed in relation to adaptation. Evidence for local adaptation is drawn from molecular investigations, genotypic selection experiments, and integrated breeding and field studies. The fragility and uniqueness of locally adapted gene pools is emphasized. Threats arise from direct interactions between native and introduced fish through stocking and escapees of cultured fish. Conservation of genetic resources must not only include practices that maximize levels of genetic diversity, but also measures to preserve the associated genotypic variance in ecologically‐significant traits. The integration of descriptive population genetic studies with empirical demonstrations of adaptive traits is encouraged.
Physiological determinants of distribution in fish*
Authors: Davenport J. , Sayer M. D. J.
Published: April 2005

Fish are totally excluded, by virtue of their physiology, only from a permanently terrestrial existence, from bodies of water with a pH below 4 or above 10 or with a calcium content below 10 mmol l−1, from permanently anoxic environments and from hypersaline water bodies with salinities above about 90‰. In less extreme, but still demanding, environments physiological limitations constrain the distribution of certain categories of fish. Extreme conditions are associated with low‐energy life styles.
Vertical distribution of Atlantic salmon (Salmo salar) as a function of illumination
Authors: Huse I. , Holm J. C.
Published: April 2005

The vertical distribution of cultured Atlantic salmon larger than 1 kg was monitored by hydroacoustics in both a shallow (6 m) and a deep (20 m) cage. Surface light levels and fish distribution were registered for three periods throughout the year. The two fish groups were fed calculated rations twice a day. During the winter and spring (including vernal equinox), the fish were distributed at around 5 m depth in both cages when not feeding. Around summer solstice, the fish preferred deeper waters when not feeding. The light dependency of the vertical migration was pronounced, and indicates clearly that even a 20 m deep cage is not deep enough to meet the depth requirements of large Atlantic salmon during summer.
Distribution and density of populations of goldsinny wrasse (Ctenolabrus rupestris) on the west coast of Scotland
Authors: Sayer M. D. J. , Gibson R. N. , Atkinson R. J. A.
Published: April 2005

A field survey of populations of goldsinny wrasse (Ctenolabms rupestris) was undertaken on selected areas of rocky coast of west Scotland. Observations by sub‐aqua diving were used to determine distribution, habitat preference, and population density, and their seasonal variations. Availability of the preferred refuge type (crevices on rock faces, or between boulders, where two or more entrances exist) was essential in determining goldsinny presence. Goldsinny were not always present in areas or at depths where the influences of freshwater runoff (low temperatures and salinities) were likely, even if the preferred habitat type was available. In areas remote from these influences, and where there were suitable refuges, depth of water (0–44 m), macroalgal cover and high current speeds (2.1–3.6 ms−1) did not affect goldsinny distribution. Observed densities of goldsinny reached a peak in summer months with a maximum of 4.0 m−2 in areas of shallow boulder scree, but only 1.0 m−2 in shallow areas with little scree, or at deeper study sites. Numbers of goldsinny observed actively swimming decreased after October, with a rapid disappearance in November. A gradual reappearance was recorded in late April, and early May. Changes in activity may be influenced by both water temperature and photoperiod. Young‐of‐the‐year goldsinny were first observed in August in shallow water (0–8 m) areas typified by rock/boulder scree and/or high macroalgal cover. Where adults also inhabited these nursery areas, 0+ fish could make up over 50% of the total population. After their first winter, juvenile goldsinny may migrate away from inshore sites.
Analysis of the demersal community of fish and cephalopods on the Agulhas Bank, South Africa
Authors: Smale M. J. , Roel B. A. , Badenhorst A. , Field J. G.
Published: April 2005

The demersal fish and cephalopod communities of the continental shelf and upper slope from 17 to 395m deep were studied during five annual cruises between Cape Agulhas and Port Alfred, South Africa. The cruises showed a consistent pattern of an inshore community (<100m), a shelf community (c. 90–190m) and a shelf‐edge/upper slope fauna (>200m). These groups were identified by dendrograms and multidimensional scaling cluster analysis, which supported on‐board observations of catch variation with depth. Although the boundaries are not clearly defined, examination of physical features at the clustered stations suggests that depth, temperature and, to a lesser extent, oxygen concentration are important in the grouping. Occasional, apparently anomalous associations of inshore stations suggested that water temperature and oxygen may over‐ride the normal depth distributions of the species groups. This intimates that patterns offish and cephalopod distribution may be dynamic and in part related to the physical parameters of the water body.
Vulnerability of late larval and early juvenile Atlantic herring, Clupea harengus, to predation by whiting,Merlangius merlangus
Authors: Gallego A. , Heath M. R.
Published: April 2005

Laboratory experiments investigated changes in the vulnerability of herring to predation by whiting during growth from <34 to >80mm in length, Premetamorphic herring (<50mm) failed to react to c. 50% of attacks by the predator, but this was reduced to c. 20% in postmetamorphic fish. Premetamorphic herring failing to react had c. 30% probability of survival due to unforced errors by the predator (unsuccessful attacks that did not elicit a reaction by the prey), but these errors did not occur after herring metamorphosis. The loss of the advantage of lower conspicuousness following metamorphosis was counterbalanced by increased reactivity. Antipredator benefits should increase with schooling behaviour (first evident in experiments at c. 50 mm), so predation mortality should decrease in postmetamorphic herring in the sea. Metamorphosis itself would be associated with high predation risk since conspicuousness is enhanced but reactivity and schooling behaviour are still not fully developed.
Germinal potentialities during sexual state changes in a protandric hermaphrodite, Amphipnon frenatus (Teleostei, Pomacentridae)
Authors: Bruslé‐Sicard S. , Reinboth R. , Fourcault B.
Published: April 2005

In Amphiprion frenatus, a protandric hermaphrodite, male sex inversion is characterized by a decrease of spermatogenic activity in the ovotestis followed by a degeneration of male gevm cells and an increase of oogenic activity. Among female germ cells, undifferentiated primordial germ cells (PGCs) were identified; their participation in building up the ovary is suggested. In addition, the unusual association of juveniles with a single adull member or juvenile groupings lacking the presence of a monogamous pair, induced in juveniles the anticipated sex differentiations (in either male or female orientation) in which not only spermatogonia and oogonia but also PGCs are involved.
Extrahepatic tissue copper concentrations in white perch with hepatic copper storage
Authors: Bunton Tracie E. , Frazier John M.
Published: April 2005

Hepatic copper storage in man (Wilson's disease), Bedtington and West Highland white terriers, and white perch (Morone americana) is characterized by the progressive accumulation of copper in hepatic lysosomes bound to cytoprotective metallothionein. In man, saturation of the liver storage capacity results in the distribution of copper to extrahepatic tissues with multiple organ system dysfunction. To determine if extrahepatic tissue copper concentrations also increase in white perch, copper and zinc levels in liver, brain, heart, gills, serum, and bile were determined by atomic absorption spectrophotometry and compared to striped bass (Morone saxatilis). Results showed that brain copper concentrations in. white perch were elevated and significantly correlated with liver copper. Bile and serum copper also increased significantly with liver copper. Copper levels in heart and gill tissues were low. Liver zinc was increased in white perch but not to the same magnitude as copper, and was correlated significantly with liver copper; possibly a non‐specific secondary increase related to an overall increase in hepatic metallothionein. Histochemical staining of liver with rubeimc acid for copper was proportional to copper concentrations, and clusters of positive mononuclear cells were also seen in brain and spleen. Foci of macrophages in spleen were also intensely positive with Perl's iron stain which may have been indicative of haemolysis. The patterns of copper distribution seen in white perch present a useful comparative model to study alterations in copper metabolism.
Further studies on the sexuality of the hermaphroditic teleost Diplodus sargus, with particular reference to protandrous sex inversion
Authors: Micale Valeria , Perdichizzi Francesco
Published: April 2005

Histological events associated with the process of sex inversion are described in the protandrous teleost Diplodus sargus reared in captivity. This species possesses typical sparid ovotestes in which the testis and ovary occur in separate zones. After spawning, the testicular tissue within the bisexual gonad undergoes regressive changes such as spermatogonial degeneration, deposition of yellowish pigment and proliferation of connective cells and fibres. At the same time ovarian tissue begins to develop. Transitional individuals were 26–7% of examined fish, while the other 73–3% were functional males.
Changes in otolith microchemistry of the Japanese eel, Anguitta japonica, during its migration from the ocean to the rivers of Taiwan
Authors: Tzeng W. N. , Tsai Y. C.
Published: April 2005

The newly recruited Japanese eel, Anguilla japonica, elvers and 1‐year‐old eels collected in estuaries and in rivers, respectively, were studied. The microstructure and chemical composition of the sagittal otolith of these eels were examined by SEM and wavelength‐dispersive spectrometer (WDS), A transition zone or‘elver mark’was observed in the otolith of the young eels. A comparison of the otoliths of elvers with those from the 1‐year‐old eels suggests that this transition zone was deposited during upstream migration, a change from a marine to freshwater environment. Strontium (Sr) content in the primordium of the otolith of both elvers and young eels was low, probably due to the maternal or freshwater origin of the oocyte. The concentration of Sr in the otolith increased gradually during marine life and reached a peak approximately 1 month before upstream migration. As the elvers entered the estuary, the Src concentration dramatically decreased and remained at a low level thereafter. These findings indicate that the history of the migratory environment of the eel can be reconstructed from a combined study of otolith microstructure and microchemistry analysis.
Phylogeny of flatfishes (Pleuronectiformes): comparisons and contradictions of molecular and morpho‐anatomical data
Authors: Verneau O. , Moreau C. , Catzeflis F. M. , Renaud F.
Published: April 2005

Several species of flatfishes (Pleuronectiformes) have been studied by isoenzyme electrophoresis and DNA/DNA hybridization to establish the evolutionary relationships of this group of fishes. This molecular data‐based phylogeny has been compared to previously described phylogenies based on morpho‐anatomical criteria. A number of discrepancies are observed and discussed. The high degree of genetic divergence observed within the families of Pleuronectiformes indicates that their origin seems to be much older than suggested by their striking morphological similarity.
Effects of salinity on distribution, growth and survival of three neotropical armoured catfishes (Siluriformes—Callichthyidae)
Authors: Mol Jan H.
Published: April 2005

Three species of closely related armoured catfishes, Hoplosternum littorale, H. thoracatum and Callichthys callichtkys, are widely distributed throughout (sub)tropical South America, but a detailed inspection of collection localities in both Suriname and the South American continent reveals a clear pattern. Hoplosternum littorale is not found in rainforest creeks and clear‐water rivers draining the Precambrium Guiana and Brazilian Shields. Here, waters are extremely poor in dissolved minerals. In salinity tolerance experiments, 1‐week‐old larvae of H. littorale were found to be incapable of surviving in rainwater that is also very poor in electrolytes. Probably for the same reason, H. littorale is not collected in black‐water rivers like the Rio Negro. Within the Amazon river‐system H. litiorale is found in sediment‐laden white‐water rivers originating in the Andes. Larvae of H. thoracatum and C. caiiichthys are able to survive and develop further in rainwater and consequently have a less restricted distribution than H. littorale. Both species are found in clear water and black water. All three species tolerate salinities up to 2000 mg Cl/1, and show a marked decrease in growth at low salinities.
The fate of a roach Rutilus rutilus stock under an extremely strong fishing pressure and its predicted development after the cessation of mass removal
Authors: Horppila J. , Peltonen H.
Published: April 2005

The effects of very intensive exploitation on a roach stock over 5 years are estimated. The total roach catch of the mass removal carried out with trawls was 507 metric tons (195 kg ha−1, 54% of the total catch). According to the virtual population analysis the biomass of the stock has decreased from 180 kg ha−1 in 1989 to c. 50 kg ha−1 in 1993. The production of the stock has fallen from 64 to 33 kg ha−1. The stock is dominated by younger age groups than before the mass removal. The future development of the stock is predicted by considering different levels of natural and fishing mortality. If the exploitation is stopped totally after 1993, roach biomass is predicted to double in 3 years. A constant fishing mortality rate of 0.3 (yearly catches 45–50 metric tons) would prevent the recovery of the stock, providing that 1–year–old and older roaches are exploited.
Non‐specific cellular responses of rainbow trout to Vibrio anguillarum and its extracellular products (ECPs)
Authors: Lamas J. , Santos Y. , Bruno D. W. , Toranzo A. E. , Anadón R.
Published: April 2005

We have studied the early inflammatory response induced by Vibrio anguillarum and by its extracellular products (ECPs) in rainbow trout after intraperitoneal injection. The results showed a very similar inflammatory response which included leucopenia, mainly due to lymphopenia, neutrophilia and an increase in the number of circulating monocytes. Melanomacrophages as well as immature leucocytes were frequently observed circulating in the blood of injected rainbow trout. Monocytes often contain phagocytosed bacteria and other, altered cells including erythrocytes and leucocytes. However, neutrophils only occasionally phagocytosed bacteria. Many circulating leucocytes showed important structural alterations. Neutrophils of trout injected with bacteria and ECPs also showed stronger PAS‐staining than those of control trout as well as Döhle bodies and swollen granules. A marked vasodilatation was observed in the kidney and spleen which was coincidental with a mobilization of eosinophilic granular cells and an hypertrophy of sinusoidal endothelial cells showing an increase in the number of cytoplasmic granules. An increase in the number of macrophages and melanomacrophages in the kidney and spleen as well as oedema and leucocyte infiltration in the liver and gills were also noted.
Precocious ovarian recrudescence and induced off–season spawning of Heteropneustes fossilis by D‐Lys6 salmon gonadotropin releasing hormone analog (sGnRH‐A)
Authors: Alok Deoraj , Krishnan T. , Salunke Dinakar , Gupta Hemamalini , Talwar G. P. , Garg Lalit C.
Published: April 2005

The feasibility of photothermal treatment and use of salmon gonadotropin releasing hormone analogue (sGnRH‐A) for induced spawning of Heteropneustes fossilis outside the spawning season was investigated. Fish were maintained at 30° C and 14 h light (L)/10 h dark (D) for 60 days between the post‐spawning season and preparatory season. Fish attained gonadal maturity 4 months earlier compared to the natural spawning season. Mature fish were induced to spawn by D‐Lys6 sGnRH‐A at a dose of 25 μg kg−1 body weight. The eggs obtained were fertilizable. Injection of D‐Lys6 sGnRH‐A at different time points during the photodiurnal cycle did not influence the latency period and spawning of H. fossilis.
Growth, movements and diet of the terapontid Amniataba caudavittata in an Australian estuary
Authors: Wise B. S. , Potter I. C. , Wallace J. H.
Published: April 2005

Samples of Amniataba caudavittata were collected from the Swan Estuary in south‐western Australia between February 1977 and December 1980, using seine nets in inshore shallow waters and gillnets and otter trawls in offshore waters. Although fish could only be aged using otoliths until they were 18–22 months old, they had by that time reached c. 75% of their final length. The mean lengths of the cohorts determined by using MIX, which analysed each of the monthly length‐frequency distributions independently, were similar to those yielded by MULTIFAN, which constrains the means of each of the sequential and corresponding cohorts to a von Bertalanffy growth curve. Consequently, the von Bertalanffy growth curve parameters determined by MULTIFAN and those derived from the use of the means produced by MIX were similar. The clear cut trends exhibited by the progression of modal lengths in successive samples, and their close correspondence to the trends shown by the growth curves, demonstrate that many A. caudavittata live for at least 3 years. Growth was seasonal and confined to the warmer months of the year. The apparent negative growth recorded in winter can be attributed to a tendency for the smaller representatives of the different cohorts to remain inshore at that time and thus to be more susceptible to capture by seine netting, the main sampling method. Offshore movements by larger fish in the winter allow those fish to remain in the high salinities found beneath the pronounced haioclines that form in the deeper waters of this estuary during the heavy freshwater discharge that occurs typically at that time of the year. Adult A. caudavittata move into the upper estuary where spawning occurs, with considerable numbers of the resultant juveniles then moving downstream into the middle estuary. A, caudavittata is a benthic omnivore, with the 0+ age class ingesting algae and a range of small crustaceans, while older fish prey to a greater extent on polychaetes.
Characteristics of dispersal in the eastern mosquitofish Gambusia holbrooki
Authors: Congdon Bradley C.
Published: April 2005

The demographic and genetic characteristics of dispersing Gambusia holbrooki were examined relative to changes in stream flow velocity, flow direction, and rapid saltwater inundation. Dispersal of all G. holbrooki sex classes decreased as flow velocity increased, dispersal for a given flow velocity being greater in female, than male and juvenile fish respectively. Juveniles and males dispersed at low (9 mm s−1) but not high (109 mm s 1) flow. Females dispersed at both flow rates. Dispersing adults were not larger than non‐dispersing adults of the same sex. Direction of dispersal was sex and size dependent, but independent of flow velocity. Larger females (>22 mm) moved preferentially downstream, while smaller females (17–22 mm) remained stationary or moved in the upstream direction. Males dispersed equally in both directions. No relationship was found between dispersal characteristics and the presence of high salt concentrations. Movement patterns at high flow were independent of glucose‐6‐phosphate isomerase (GPI‐2*) alleles carried by dispersing individuals. Significant non‐random dispersal of sex or size cohorts, and the interaction of dispersal with flow velocity have significant implications for the maintenance of genetic diversity in stream ecosystems, particularly where localized selection or genetic drift may alter the genetic constitution of specific sex or size cohorts. The applicability of these results to field populations is discussed.
The relationship between river flow and entry to the Aberdeenshire Dee by returning adult Atlantic salmon
Authors: Smith G. W. , Smith I. P. , Armstrong S. M.
Published: April 2005

One hundred and nine returning adult salmon were radio‐tagged in the estuary of the Aberdeenshire Dee, Scotland between February and August 1985 to 1989 and the times when 62 fish entered the river were recorded. Elapsed times between tagging and river entry were significantly greater during periods of lower than average river flows in all months where there were sufficient data to allow statistical comparison. The degree of association between river entry and particular levels of river discharge rate varied seasonally. The proportion of days associated with river entry declined at the lower end of the range of flows available to tagged fish in the summer months. Absolute levels of river discharge played a significant role in modifying the response of salmon to changing flows. During periods of lower than average seasonal flow, river entry was closely associated with days when flow had increased since the previous day. During periods of higher than average flow, river entry was not significantly associated with such periods of increased flow. The results suggest that models which relate river entry by salmon to absolute discharge rates alone are unlikely to be generally reliable.
The metabolism of neutral and polar lipids in eleuthero‐embryos and starving larvae of the African catfish Clarias gariepinw
Authors: Verreth J. , Custers G. , Melger W.
Published: April 2005

Lipid class analysis was carried out on developing eggs, eleuthero‐embryos (yolk sac larvae) and starving larvae of the freshwater species Clarias gariepinus, using thin layer chromatography. Samples were taken at fixed intervals from a large pool of fertilized eggs obtained through induced reproduction of several parent fish. The total lipid content of fertilized eggs fluctuated around 22% of the dry weight and decreased from 21% at hatching to about 12–5% at yolk absorption. In starving larvae, the amount of total lipid per individual remained relatively constant. Polar lipids [phosphatidylcholine (PC) and phosphatidylethanolamine (PE)] together accounted for 73·6 to 80% of total lipid. PC was by far the most abundant lipid class during the entire experimental period (70–75% of total lipid). PC was catabolized proportionally to total lipid, demonstrating its role as the main energy supplier. All yolk PE was converted to body tissue. The neutral Hpids consisted of triglycerides (TAG), cholesterol and cholesteryl esters (respectively 12·5, 10 and 3% of total lipid in newly fertilized eggs). All TAG were depleted before complete yolk absorption.
Effects of experimental seismic shock on vasoactivity of arteries, integrity of the vascular endothelium and on primary stress hormones of the Atlantic salmon
Authors: Sverdrup A. , Kjellsby E. , Krüger P. G. , Fløysand R. , Knudsen F. R. , Enger P. S. , Serck‐Hanssen G. , Helle K. B.
Published: April 2005

The postulated harmful effects of underwater detonations of explosives on the vascular endothelium in farmed Atlantic salmon were assessed under controlled conditions. Acclimated salmon were exposed to a series of 10 underwater explosions over 70 min, each of ≃2 MPa in pressure amplitude, in a laboratory tank. No mortality occurred immediately or during the subsequent 7 days of observation. The response to each of the 10 detonations was cessation of swimming for a few minutes and failure to express a flight reaction.

Structurally, the vascular endothelium of the ventral aorta (VA) and the coeliaco mesenteric artery (CMA) revealed signs of injury within the first 30 min after the experimental shock. In contrast to vessels from the controls, the injury was further aggravated by the mounting procedure for tension recording. The endothelial impairment was temporary, persisting throughout the first days while being restored after 1 week.

Functionally, the cholinergic and adrenergic vasoconstrictor responses in the CMA were markedly reduced during the first day after the shock. These responses were similar to those observed in the endothelium probed CMA of controls. The loss of structural integrity and the reduced functional responses indicated a temporary impairment of the vascular endothelium in response to this experimental simulation of a seismic shock.

The primary stress hormones, adrenaline and cortisol, were not immediately elevated in plasma, but revealed different patterns of delayed increases. The head kidney content of catecholamines was not altered by the acoustic shock, while the atrial uptake of both calecholamines declined progressively during the 48 h of observation. Plasma chloride was not affected.