bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrosensory avoidance of metal obstacles by the paddlefish
Authors: Gurgens C. , Russell D. F. , Wlikens L. A.
Published: April 2005

Paddlefish Polyodon spathula detected and avoided obstacles with an exposed metallic surface but not plastic objects. An aluminium obstacle was avoided from significantly greater minimum approach distances than were any of the other obstacles. No significant difference was detected between the plastic and plastic‐covered aluminium obstacles, while control values were significantly less than for all obstacle types. Avoidance distances measured at different water conductivities were not significantly different. Fish collided frequently with the plastic and plastic‐covered aluminium obstacles, and with the control site, suggesting that these obstacles were not detected by the electrosensory apparatus. The aluminium obstacle was avoided successfully in all test runs. The unambiguous avoidance behaviour elicited by the aluminium obstacle suggests that large metallic structures, such as locks and dams, have the potential to interfere with paddlefish migrations. ©2000 The Fisheries Society of the British Isles
Factors related to gizzard shad and the threadfin shad occurrence and abundance in Florida lakes
Authors: Allen M. S. , Hoyer M. V. , Canfield D. E.
Published: April 2005

Gizzard shad Dorosoma cepedianum were collected in 23 and threadfin shad D. petenense were collected in 22 of the 60 Florida lakes sampled. Logistic regression equations were 94% effective for predicting gizzard shad occurrence from chlorophyll and lake surface area, and 84% effective for predicting threadfin shad occurrence from lake surface area and lake volume inhabited (PVI). Occurrence of both shad species was related positively to lake size. In lakes where gizzard shad or threadfin shad were collected, shad density and biomass of both shad species were related positively to chlorophyll. Gizzard shad populations were generally vulnerable to predation in lakes, with the per cent of gizzard shad ≤200mm LT values exceeding 60% with few exceptions. Effects of gizzard shad and threadfin shad on fish community dynamics may be confined to relatively large (>100 ha) and fertile (chlorophyll >20–30μg l−1) Florida lakes.
Foraging kinematics of barramundi during early stages of development
Authors: Dowling N. A. , Hall S. J. , Mitchell J. G.
Published: April 2005

Contrary to expectations there was no transition from a saltatory to a cruise search strategy in foraging behaviour of 7‐to 33‐day‐old barramundi over the period of metamorphosis. Rather, there was a continual change in foraging behaviour, with increasing durations between swimming pauses and increasingly straight swimming paths, implying that hydrodynamic constraints on swimming may be a key determinant of foraging kinematics. It is suggested that the notion of saltatory search as a third, unique foraging strategy needs to be re‐evaluated.
Genetc divergence and phylogeny of the Salmoninae based on allozyme data
Authors: Osinov A. G. , Lebedev V. S.
Published: April 2005

The data on 31–37 allozyme loci in 21 species of nine salmonid genera are used for phylogenetic analysis by seven distance methods and several variants of cladistic analysis. Monophyletic origin for all genera and three sub‐families of the Salmonidae is corroborated. The closest phylogenetic relationships are characteristic of Parasalmo and Oncorhynchus (bootstrap support is 88–99%), Brachymystax and Hucho (68–97%), and the clade (Brachymystax + Hucho)+Salmo (up to 85%). The patterns of phylogenetic relationships in the group Salmo‐Parasalmo‐Oncorhynchus are analogous to those in the group Parahucho‐Hucho‐Brachymystax. The position of Parahucho in phylogenetic trees of the Salmoninae is extremely unstable, although it is most likely associated with the clade (Brachymystax + Hucho)+Salmo) or Salvelinus. When using the out group analysis, Salvelinus appears as the earliest branch of the Salmoninae tree, whereas if the molecular clock is assumed, the basal position is occupied by Oncorhynchus. However, the latter genus is probably characterized by a substantially increased rate of molecular evolution.
Macrophage aggregates in gilthead sea bream fed copper, iron and zinc enriched diets
Authors: Manera M. , Sera R. , Isani G. , Carpenéa E.
Published: April 2005

Gilthead sea bream Sparus aurata from consecutive year classes (0+ and 1+) and from the same parent stock were fed four diets, three of which were fortified with copper, iron and zinc. Concentrations of these elements were little affected by the diet. Hepatic, renal and splenic tissues sections were examined to detect the influence of the diet on the number and morphology of macrophage aggregates (MAs); in particular their structure was examined in the spleen. Three different types of MAs were detected: (1) unstructured, (2) partially structured and scarcely defined and (3) fully structured and well defined. Melanin was the most abundant pigment in the pigmented macrophages which form MAs and the amount of this pigment was influenced by season. Ferritin, in contrast with previous data obtained in other fish species, was more abundant in renal than in splenic MAs. Significant differences in splenic MA numbers among fish fed different diets and among different periods of the year were detected. The results suggest that a polyfactorial regulation could act on the splenic MA number in gilthead sea bream.
Effects of courtship and relative mate size on sexual motivation in Atlantic salmon
Authors: De Gaudemar B. , Bonzom J. M. , Beall E.
Published: April 2005

Both sexes of Atlantic salmon Salmo salar were very sensitive to the absence of their mate on the spawning ground, particularly females during the last hour before oviposition. The improvement of behavioural chaining just before viposition might elicit the accurate timing of synchronized gamete release for successful fertilization. While the reproductive behaviour of the opposite sex could largely affect breeding activity, relative mate size appeared to be the prevailing sexual motivation factor in this species. Even in the absence of courtship, large mate size may constitute a supra‐stimulus inducing an increase in spawning behaviour of the other sex. Females with smaller males delayed their first spawning activity, took longer to spawn and made more nests than those with large males. However, female egg retention was not influenced by relative male size.
The pathology and seawater performance of farmed Atlantic salmon infected with glochidia of Margaritifera margaritifera
Authors: Treasure J. W. , Turnbull T.
Published: April 2005

The pathology of glochidial infection of the freshwater mussel Margaritifera margaritifera was examined in farmed Atlantic salmon Salmo salar in fresh water and for 150 days after transfer of salmon to sea water. Prevalence of infection in fresh water was 95%, mean abundance 134 per fish and mean infection intensity 140. Prevalence in sea water was 80–94% in the first 7 weeks after transfer but glochidia were absent, apart from remains, after 50 days in sea water. Glochidia on salmon in fresh water were associated with localized hyperplasia and fusion of secondary gill lamellae. Focally extensive epithelial hyperplasia and fusion of secondary lamellae were present 4–10 days after transfer to sea water. Twenty‐three days after transfer, small nodules with a more discrete appearance were present suggesting partial resolution of tissue response; hyperplastic responses associated with glochidia were much reduced after 50 days. Plasma chloride in infected fish 10 days after transfer was 153 mmol. 1−1, significantly higher than fish without infection, suggesting poorer adaptation to sea water. No mortalities due to glochidial infection in sea water were recorded and there was no significant difference in mean weight between infected and control fish.
Seasonal patterns in feeding ecology of three small fishes in the Biandantang Lake, China
Authors: Xie S. , Cui Y. , Zhang T. , Li Z.
Published: April 2005

Feeding ecology of three small fish species, Hypseleotris swinhonis, Ctenogobius giurinus and Pseudorasbora parva was studied seasonally in the Biandantang Lake, a small, shallow lake in central China. Gut length, adjusted for total body length, was significantly higher in spring than in other seasons for all the three species. Seasonal changes in gut length were not associated with changes in food quality. Weight of fore‐gut contents, adjusted for body weight, was significantly higher in winter and spring than in summer and autumn in H. swinhonis and C. giurinus, and significantly higher in autumn than in spring and summer for P. parva. Percentage of empty fore‐guts was highest in summer and lowest in spring for H. swinhonis and C. giurinus, and highest in winter and lowest in autumn for P. parva. Diet of the three small fishes showed apparent seasonal changes, and these changes reflected partly the seasonal fluctuations of food resources in environment. Diet breadth was high in winter and low in autumn for H. swinhonis, high in winter and low in spring and summer for C. giurinus, and high in autumn and low in spring for P. parva. Diet overlaps between pairs of species were biologically significant in most cases, except between H. swinhonis and P. parva in summer and autumn and between C. giurinus and P. parva in autumn.
The biometry of gills of 0‐group European flounder
Authors: Hartl M. G. J. , Hutchinson S. , Hawkins L. E. , Eledjam M.
Published: April 2005

The gill surface area of 0‐group, post‐metamorphic Pleuronectes flesus L. was examined using digital image analysis software and expressed in relation to body mass according to the equation log Y=loga+c logW (a=239·02; c=0·723). The components that constitute gill area, total filament length, interlamellar space and unilateral lamellar area were measured. The measurement of the length of every filament on all eight arches showed that commonly used methods of calculation can lead to an under‐estimation of up to 24% of total filament length. Direct measurements of unilateral lamellar area with digital image analysis showed that previously reported gill area data for the same species was over‐estimated by as much as 58%. In addition, in this species the neglect of gill pouch asymmetry after metamorphosis, can bring about a 14% over‐estimation of total gill area.
Urine of ovulated female masu salmon attracts immature male parr treated with methyltestosterone
Authors: Yambe H. , Yamazaki F.
Published: April 2005

Methyltestosterone‐treated immature male masu salmon Oncorhynchus masou parr were attracted to both the urine of ovulated females and the ether soluble basic substances extracted from the urine, but not to immature female urine. It is suggested that the male response to the sex attractant (releaser pheromone) in the urine is under the control of androgens.
Annual variations in the reproductive traits of Pomatoschistus microps in a Mediterranean lagoon undergoing environmental changes: evidence of phenotypic plasticity
Authors: Pampoulie C. , Bouchereau J. L. , Rosecchi E. , Poizat G. , Crivelli A. J.
Published: April 2005

The spawning period of the common goby Pomatoschistus microps from 1993 to 1997 in the Vaccarès lagoon did not vary, except in 1997 when it was longer due to the reproduction of the young‐of‐the‐year. Egg size and number, and reproductive allocation varied greatly with one year to another. Female common gobies increased both their fecundity per spawning act and their egg size from 1993 to 1995. The annual variation in the reproductive effort suggests a high phenotypic plasticity of reproductive traits in P. microps, in the face of environmental perturbations. In winter 1993–1994, a centennial flood of the Rhône River caused major hydrological changes in the lagoon in less than 1 week, affecting many invertebrates and fish for several years. The reproductive investment of the common goby increased, possibly as a consequence of those environmental changes.
Comparison of gene flow estimates between species of darters in different streams
Authors: Faber J. E. , White M. M.
Published: April 2005

Allozyme variation was assessed at two localities for 38 loci inEtheostoma blennioidesand 43 loci inE. flabellare. Percent polymorphism (P) ranged from 18·4 to 31·6 and average heterozygosity (H) ranged from 0·026 to 0·079. Estimates of gene flow indicated panmictic populations ofE. blennioidesand sub‐divided populations ofE. flabellare, with significantly more substructuring ofE. flabellarefrom one population. Population structuring ofE. flabellareand no structuring ofE. blennioidesis consistent with predictions based on life history data. Significantly different gene flow estimates forE. flabellarebetween streams imply that each stream environment induced different population structures. Reduced heterozygosity for both species and significantly less population structuring in one population are consistent with drought‐induced extinction and recolonization that probably occurs in the smaller stream.
Induction of maturation and spermiation in the male European eel: assessment of sperm quality throughout treatment
Authors: Pérez L. , Aturiano J. F. , Tomás A. , Zegrari S. , Barrera R. , Espinós F. J. , Navarro J. C. , Jover M.
Published: April 2005

Weekly injections of human chorionic gonadotropin (hCG; 1·5 IU g−1W) induced spermiation in 87–100% farmed male European eels Anguilla anguilla over a 10‐week period, producing 3 ml (100 g)−1 milt volume, at 1˙4×109 spermatozoa ml−1 sperm mobility peaked in ninth week of treatment with 97% of males with motile sperm. Gonadotropin‐treated males showed earlier but similar morphological changes to control males. Whereas higher sperm density was obtained 6 h after hCG administration, higher percentage of motile cells and longer sperm mobility were observed 24 h after the treatment indicating that this is the optimum time to obtain good sperm after the hormonal induction. Several monounsaturated fatty acids in sperm increased significantly from week 5 to 9 of treatment (when highest volume, density and mobility of milt were recorded), whereas eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and total n‐3 polyunsaturated fatty acids (PUFAs) were significantly reduced. Fatty acid levels returned to initial values after 13 weeks of treatment. These results are in agreement with the reduction of n‐3 PUFAs recently observed in the ovary of female Japanese eel during artificial maturation, and an attempt is made to suggest a physiological explanation of its possible relation with sperm quality.
Effects of polyunsaturated fatty acids and gonadotropin on prostaglandin series E production in a primary testis cell culture system for the European sea bass
Authors: Asturiano J. F. , Sorbera L. A. , Zanuy S. , Carrillo M.
Published: April 2005

Prostaglandin series E (PGE) production by mixed populations of isolated sea bass Dicentrarchus labrax testicular cells was measured after culture at 20° C in L‐15 for up to 24 h in the absence or presence of arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and/or gonadotropin (hCG). AA stimulated a significant dose‐ and time‐dependent increase in PGE production. EPA stimulated PGE production only during the first 6 h although levels were 26·4% those induced with AA; DHA reduced PGE production. Although hCG alone had no effect, it enhanced AA‐induced PGE formation and suppressed EPA‐induced PGE production. These results suggest that essential PUFAs modulate significantly testicular PGE production in vitro and therefore may have important effects on steroidogenesis and spermiation in the male European sea bass.
Analysis of mitochondrial DNA sequences from two Maurolicus taxa: evidence for separate species?
Authors: Suneetha K. B. , Dahle G. , Nævdal G.
Published: April 2005

Fixed nucleotide differences were found in the partial 16S rRNA mitochondrial gene sequences between two regional populations of Maurolicus (identified as M. muelleri and M. walvisensis), indicating clear genealogical separation of the two taxa. Accordingly, the two taxa can be considered as recently diverged species, supporting the recent proposition of a polytypic genusMaurolicus.
Some characteristics of freezing avoidance in two osmerids, rainbow smelt and capelin
Authors: Raymond J. A. , Hassel A.
Published: April 2005

Winter‐acclimatised rainbow smelt Osmerus mordax have elevated levels of glycerol and trimethylamine oxide (TMAO), and a protein antifreeze, all of which are lost in summer. No seasonal differences were found in glycerol‐3‐P‐dehydrogenase, glycerol‐3‐phosphatase and glutamate dehydrogenase, which are involved in the synthesis of glycerol or its precursors. Although glycerol production requires NADH, no large seasonal differences were found in the activities of glucose‐6‐P‐dehydrogenase and 6‐phosphogluconate dehydrogenase (pentose phosphate pathway), malate dehydrogenase and aspartate aminotransferase (malate‐aspartate shuttle) or in the NAD : NADH ratio. Thus, other regulatory mechanisms must be involved. Capelin Mallotus villosus collected from mid water in the Barents Sea in September (water temperatures +0·4 to −1·6°C) had only negligible amounts of glycerol, and no protein antifreeze, although serum TMAO levels (44 mm) were unusually high for a teleost. Capelin appear to avoid freezing largely by avoiding water layers with temperatures below their body freezing point, and by occasional supercooling.
Heavy metal pollution in Antarctica: a molecular ecotoxicological approach to exposure assessment
Authors: Evans C. W. , Hills J. M. , Dickson J. M. J.
Published: April 2005

Trematomus bernacchii sampled from two sites at Ross Island, Antarctica, were assessed for condition (gonadal and hepatic somatic indices and condition factor), pathological state (liver and gill histology), hepatic metal (Zn, Cu, Cd and Ni) concentrations, and metallothionein induction by quantitative competitive (qc) RT‐PCR. Fish from a polluted site (Winter Quarters Bay) had pathological anomalies including necrosis and periductal inflammation in their livers, and X‐cell disease, epithelial hyperplasia, lamellar fusion and aneurysms in their gills. Such anomalies were less common in fish from a relatively pristine site (Backdoor Bay, Cape Royds). Fish from both sites had similar liver concentrations of Zn, Cu and Cd and qcRT‐PCR revealed similar levels of hepatic metallothionein mRNA. Ni in the livers of fish from Winter Quarters Bay were higher than those in fish from Backdoor Bay, but the differences were not great enough to affect hepatic metallothionein mRNA significantly. Despite the polluted state of Winter Quarters Bay waters, it seems that the heavy metals present may have only limited impact on the health status of fish collected from this locality. This may reflect a low bioavailability of the heavy metals in Ross Island marine sediments and suggests that other factors, such as relatively high levels of organic pollutants (PAHs, PCBs) or pathogens from the nearby sewage outlet, may play a more significant role in the aetiology of pathological conditions in fish from Winter Quarters Bay.
Allozyme and microsatellite DNA markers of toothfish population structure in the Southern Ocean
Authors: Smith P. , McVeagh M.
Published: April 2005

Toothfish represent a major finfish resource in the Southern Ocean, where there has been a rapid increase in exploitation of the Patagonian toothfish Dissostichus eleginoides. Molecular genetic methods have been applied to address questions relating to stock discrimination in D. eleginoides. Eight microsatellite loci were tested in population samples from the Atlantic, Indian, and Pacific Ocean sectors of the Southern Ocean. Some loci were characterised by a large number of alleles, but no alleles were restricted to specific ocean basins. However there was a significant allelic heterogeneity in the total data indicative of population differentiation, and a high level of genetic sub‐division was measured with FST and RST. Seven polymorphic allozyme loci revealed no significant heterogeneity among Pacific and Indian Ocean sector samples. The microsatellite DNA heterogeneity suggests that there is restricted gene flow through the Southern Ocean, and that the different fishing grounds may support independent stocks.
Fishes on the Antarctic continental shelf: evolution of amarine species flock?*
Authors: Eastman J. T. , McCune A. R.
Published: April 2005

Distance, currents, deep water and sub‐zero temperatures isolate the waters of the Antarctic continental shelf from other shelf areas in the Southern Hemisphere. The Antarctic shelf is an insular evolutionary site for a variety of marine organisms. The fish fauna is relatively small and unusual in composition, consisting of 213 species with higher taxonomic diversity restricted to 18 families. Ninety‐six species of perciform notothenioids comprise 45% of the fish fauna. However in many areas of the shelf, including the highest latitudes, notothenioids make up 77% of the species and 90–95% of fish abundance and biomass. Notothenioids are morphologically and ecologically diverse and have diversified into niches in the water column. Antarctic notothenioids were evaluated using criteria employed for assessing freshwater species flocks. Although monophyly is in question, notothenioids exhibit the disproportionate speciosity (5·6‐fold more Antarctic than non‐Antarctic species) and high endemism (97%) characteristic of a species flock. Notothenioids are one of the first recognized examples of a species flock of marine fishes. Notothenioids are compared with some freshwater species flocks and calculations made of the time required for speciation (TFS) for notothenioids of the family Channichthyidae. Estimates of TFS are slower than for most lacustrine species flocks but similar to estimates for island radiations of birds and arthropods.
Inter‐annual variation in the gonad cycle of the mackerel icefish
Authors: Everson I. , Kock K.‐H. , Ellison J.
Published: April 2005

Spawning by Antarctic fish is generally considered to be seasonal and restricted to a brief period during the autumn and winter. Arising from this it has been assumed that the gonadal maturation cycle is also closely associated with the time of year. The gonad maturation cycle of the mackerel icefish Champsocephalus gunnari was investigated using data collected during research surveys and from sampling the commercial fishery. Spawning appears to occur at the same time each year, but the timing of gonadal development is subject to a considerable inter‐annual variation. The implications of this variation are discussed with respect to feeding conditions.
In vitro carbon dioxide excretion from erythrocytes of two species of Antarctic fishes and its inhibition by catecholamines
Authors: Powell M. D. , Forster M. E. , Davision W.
Published: April 2005

This study was designed to investigate whether the blood of Pagothenia borchgrevinki, exhibits a Haldane effect, and whether activation of a Na+/H+ antiporter increases transport of intracellular protons and Bohr protons out of the erythrocytes resulting in inhibition of CO2 excretion in both P. borchgrevinki, and Dissostichus mawsoni. When carbon dioxide dissociation curves were determined from blood samples pooled from three fish under oxygenated and deoxygenated conditions a Haldane effect was observed. Using an in vitro, CO2 excretion assay, the rate of HCO3− dehydration was determined on blood and plasma equilibrated under an N2atmosphere then rapidly oxygenated with air in the presence of 10−5 M noradrenaline or acetazolamide (1004M). Whole blood and plasma from P. borchgrevinki, and D. mawsoni, were equilibrated with 0·5% CO2 in air and assayed in the presence of 10−5 M noradrenaline. Erythrocyte CO2 excretion rates were depressed significantly by noradrenaline in both species. The whole blood HCO3− dehydration rate was depressed significantly following rapid oxygenation in the presence of acetazolamide indicating that the pathway of CO2 excretion included activation of intracellular carbonic anhydrase and an adrenergic receptor.
First description of larvae of Acanthodraco dewitti in the Ross Sea, Antarctica
Authors: Mesa M. La , Granata A. , Guglielmo L. , Vacchi M.
Published: April 2005

Six postlarval and an adult bathydraconid were collected in Terra Nova Bay, Ross Sea, during January‐February 1988 and February 1998, respectively. The adult was identified as Acanthodraco dewitti Skóra, 1995 (type locality South Shetland Islands), a species not recorded in the Ross Sea. The postlarvae may be those of A. dewitti. The morphology and pigmentation patterns of the postlarvae are described and compared with those of other bathydraconids.
Dissolved oxygen concentration and emergence of sea trout fry from natural redds in tributaries of the River Rhine
Authors: Ingendahl D.
Published: April 2005

A total of 4289 sea trout Salmo trutta alevins swam up from six of eleven covered redds. They emerged only from those redds where the mean dissolved oxygen level was >6·9 mg l−1 and the Sorting coe.cient, an indicator of intragravel void space, was <5. These results are discussed in relation to field studies using artificially buried salmonid eggs but also in relation to the ongoing programme for the reintroduction of Atlantic salmon in tributaries of the River Rhine.
Holding temperature during the breeding season influences final maturation and egg quality in common wolffish
Authors: Tveiten H. , Solevåg S. E. , Johnsen H. K.
Published: April 2005

Mature common wolffish, Anarhichas lupus L., previously held at 8°C for several months, were exposed to 4, 8 or 12°C throughout the breeding season (November‐January). Regardless of temperature, some females ovulated in early‐November, but thereafter ovulation was delayed in the 8 and 12°C groups compared with the 4°C group. Temperature experienced by the adult fish also affected egg development and survival even though eggs were incubated at a common temperature of 6°C. The percentages of normally cleaved eggs (at the 32‐cell stage) and egg survival to the eyed stage were significantly lower in the 12°C group (8%) than in the 4°C (73%) and 8°C (48%) groups. The differences in egg survival were also significant between the 4 and 8°C groups. Egg survival was also influenced by the length of time the broodfish had been exposed to the different temperatures: at 4 and 12°C there were significant positive and negative relationships, respectively, between egg survival and the number of days for which the female had been exposed to the given temperature prior to ovulation. Temperature experienced by the female did not affect egg size, relative egg weight, fertilization rate, relative fecundity or the number of ovulating individuals. The results indicate that both the timing of ovulation and egg quality of common wolffish are affected by the temperature experienced during the breeding season.
Anatomical features and histology of the digestive tract of two related neotropical omnivorous fishes (Characiformes; Anostomidae)
Authors: Albrecht M. P. , Ferreira M. F. N. , Caramaschi E. P.
Published: April 2005

The estimated mean intestinal coefficients of Leporinus friderici Bloch, 1794 and L. taeniofasciatus Britski, 1997, from the Upper Tocantins River, central‐western Brazil, were 1·25±0·15 and 1·14±0·07, respectively. The external surfaces of the lips have taste buds. The histological structure is composed of four layers: mucosa, submucosa, muscular, and serosa. No muscularis mucosa is detected. The oesophageal epithelium is stratified in L. friderici and pseudostratified in L. taeniofasciatus, the latter with PAS+ basal cells and eosinophilic apical cells. A thick layer of adipose tissue was found within the submucosa. Leporinus taeniofasciatus has a sphincter separating the cardiac and fundic portions of the stomach. In both species, gastric glands are present in the stomach, except in its pyloric portion. The pyloric caeca possess a simple columnar epithelium with brush border and three types of goblet cells. Rodlet cells were found in L. friderici. The three portions of the intestine showed no histological differences. Anatomical and histological features of the digestive tract are consistent with the omnivorous habit of both these species.
Seasonal changes in the habitat use and movements of adult European grayling in a large subarctic river
Authors: Nykänen M. , Huusko A. , Mäki‐Petäys A.
Published: April 2005

In late summer (13 August–13 September 1998), at water temperatures of 12·0–15·7° C, grayling (n=14) stayed mainly in the riffle‐section where they were captured in a large regulated river in northern Finland, moving little between consecutive days. In autumn (2–30 October 1998), at 1·7–6·7° C, the fish (n=16) migrated to potential overwintering sites 0–14 km up‐ or downstream by mid October, moving mainly short distances thereafter. The daily movement rates, and the total ranges covered by the fish in late summer and autumn were 54±32 m (mean±s.d) and 1053±1636 m, and 190±168 m and 3135±1850 m, respectively. In autumn the fish used deeper habitats (most suitable range 150–400 cm) with lower current velocities (20–80 cm s−1) and finer bottom substrata (mainly sand) than in late summer (depth 100–325 cm, velocity 30–110 cm s−1, and cobble‐boulder substrata).
Osteologic development of the viscerocranial skeleton in sea bream: alternative ossification strategies in teleost fish
Authors: Faustino M. , Power D. M.
Published: April 2005

The ontogeny of the viscerocranial skeleton of sea bream Sparus aurata larvae was studied from 1 to 90 days post‐hatching. In the smallest specimens analysed at 2·7 mm LN no cephalic elements were present and at 3·1 mm LN the following cartilaginous structures were visible: trabecula cranii, auditory capsule, Meckel's cartilage, quadrate, hyosymplectic cartilage, sclerotic, hypohyal, ceratohyal epihyal cartilage, interhyal, hypobranchial 1 and ceratobranchial 1. The only structure ossified at this size is the maxillary and the next ossified structures to appear are the preopercle and opercle at about 3·7 mm LN. The last bones to appear are infraorbital 2 and 6 at 15·1 mm LS. The first cartilaginous elements and structures to ossify in S. aurata appear to be related with functional requirements, so that structures involved directly in feeding and breathing generally appear and ossify before those that are not. The ontogeny of different regional structures revealed that generally the dermal bones ossify before the cartilage replacement bones. Comparison of S. aurata viscerocranial skeleton ontogeny with that of phylogenetically distant fish demonstrates that different ossification strategies exist in higher and lower teleost fish.
Spontaneous activity was unaffectedby ration size in Nile tilapia and gibel carp
Authors: Qian X. , Cui Y. , Xiong B. , Xie S. , Zhu X. , Yang Y.
Published: April 2005

Two growth trials using a range of ration sizes from starvation to maximum feeding suggested that linear relationships existed between specific growth rate and ration size for Nile tilapia and givel carp. Continuous measurement of activity showed that activity level, in terms of distance swum per day, was not affected significantly by ration size in both Nile tilapia and gibel carp.
Gastric evacuation in horse mackerel. I. The effects of meal size, temperature and predator weight
Authors: Temming A. , Herrmann J.‐P.
Published: April 2005

Gastric evacuation experiments were performed on horse mackerel Trachurus trachurus. A nearly full matrix experimental design with respect to the variables predator weight (<10–400 g) meal size (up to 7·8% body weight) and temperature (10–20°) was covered with 0‐group smelt Osmerus eperlanus as prey. A general evacuation model without meal size as a variable was fitted to the data on wet weights as well as on dry weights by means of non‐linear regression technique. Two methods of data transformation, relative data and square root transformation, were applied to improve variance homogeneity. The most reliable model fit was achieved on dry weight data applying the square root transformation technique:

image

where St=stomach content (g wet weight) at time t after ingestion, S0=the initial meal size, W=predator (g wet weight), and T=temperature. The estimated coefficient of the exponential temperature function, δ=00·032, corresponds to a Q10 value of 1·4 which is outstandingly low in comparison with results on other species. However additional experiments to determine maximum daily food rations indicated that appetite in contrast to gastric evacuation is strongly temperature dependent.
Use of otolith microincrements for estimating the age and growth of young armoured catfish Hoplosternum littorale
Authors: Ponton D. , Mol J. H. , Panfili J.
Published: April 2005

At 27·0–28·0°, the lapilli of Hoplosternum littorale developed rapidly in the embryo between 35 and 21 h before hatching. At hatching, lapilli averaged 78 μ;m on their longest axis and 69 μ;m on their shortest axis, and had up to three faint narrow microstructures. Primordia were fused and the large core was surrounded by a conspicuous discontinuous zone, formed at hatching, and visible in both sagittal and transverse preparations. The deposition rate of microincrements, counted in transverse thin sections of lapilli, was daily at least for the first 50 days and the innermost microincrements were deposited from hatching on. The growth rates of H. littorale differed significantly between two different rice field habitats in Suriname.
Fasting and hypothalamic catecholamines in goldfish
Authors: de Pedro N. , Delgado M. J. , Alonso‐Bedate M.
Published: April 2005

Hypothalamic catecholamines and their metabolites have been studied after 7 days starvation and starvation plus 1 day refeeding in goldfish Carassius auratus. A reduction of norepinephrine (NE) and dopamine (DA) content (21 and 28%, respectively) together with an increase (53%) of NE turnover, without significant modifications of DA turnover was observed following 7 days starvation. These data indicate that NE and DA are involved in the hypothalamic response to fasting in fish. Different mechanisms can be suggested, that is, an activation of noradrenergic system and a decrease of dopaminergic system by fasting. NE would stimulate food intake, whereas DA would inhibit it.
Visual morphology and feeding behaviour of the daggertooth
Authors: Welch D. W. , Pankhurst P. M.
Published: April 2005

Dissection of freshly eaten prey suggests that the North Pacific daggertoothAnotopterus nikparinisever the spine of small prey with a single slashing blow. The bite marks indicate that the immobilized prey is manipulated and swallowed head first. Frequent evidence suggests daggertooth wound prey which are too large to consume whole by cutting off strips of flesh. In either case the wounds consist of a single prominent slash mark on one side and a series of inconspicuous marks on the opposite side. Retinal morphology provides supporting evidence that daggertooths are visual ambush predators that attack prey from below, and should be considered as epipelagic rather than mesopelagic fish. Visual acuity appears to be high, suggesting that frequent attacks on prey too large to be killed immediately is not error, but a well‐defined feeding behaviour. The daggertooth may be a significant source of mortality for economically important fish such as all sizes of salmon.
Gonad structure and sexual pattern in two threadfin breams and possible function of the dorsal accessory duct
Authors: Lau P. P. F. , Sadovy Y.
Published: April 2005

A dorsal accessory duct (DAD) structure was found on the dorsal side of a functional testis in all males of both Nemipterus virgatus and N. japonicus, and determined to be homologous to the ovary, based on structural, histological and cytological evidence. Secretions, in the DAD varied according to reproductive season and were particularly marked in N. virgatus. The sexual pattern of both species was functional gonochorism. The secretions of the DAD suggest some unknown function, possibly associated with spawning, which has evidently arisen de novo within a rudimentary ovary: this is the only example of its type reported among hermaphroditic fishes.
Increased number of hybrids between benthic and limnetic three‐spined sticklebacks in Enos Lake, Canada; the collapse of a species pair?
Authors: Kraak S. B. M. , Mundwiler B. , Hart P. J. B.
Published: April 2005

In July 1999, 49 three‐spined sticklebacks were sampled from Enos Lake, Canada. Here a benthic/limnetic species pair is known to exist. In the sample, six individuals (12%) were of intermediate phenotype. These represent 17% of the 35 males in the sample. This large number of intermediates contrasts with the 1% in previous samples reported in 1984 and 1992 and may signal the collapse of the species pair.
Behavioural responses of fathead minnows to hypoxanthine‐3‐N‐oxide at varying concentrations
Authors: Brown G. E. , Adrian J. C. , Shih M. L.
Published: April 2005

Antipredator behaviour of fathead minnows Pimephales promelas increased significantly on exposure to hypoxanthine‐3‐N‐oxide at concentrations as low as 0·4 n with no further increase in response at concentrations up to 6·7.
Metazoan parasites of Macruronus magellanicus from southern Chile as biological tags
Authors: Oliva M. E.
Published: April 2005

Examination of 450 specimens of Macruronus magellanicus from two fishing grounds in southern Chile (Talcahuano: 36°40'S, Punta Arenas: 54° S) revealed 24 205 metazoan parasites, belonging to 15 taxa with low specificity: Chondracanthus australis and Neobrachiella sp. (Copepoda); Elytrophalloides oatesi, Gonocerca phycidis, Derogenes varicus and Brachyphallus parvus, (Digenea); Hepatoxylon trichiuri, Scolex pleuronectis, Clestobothrium crassiceps, Grillotia dollfusi, Pseudophyllidea gen. sp. (Cestoda); Anisakidae, Cucullanus sp. (Nematoda), Corynosoma australe and Acanthocephala gen. sp. (Acanthocephala). The list includes parasites that are common to other merluccids from the zone. The parasitological evidence does not suggest the existence of two discrete stocks, but the existence of a migratory process from south to north.
The ultrastructure of spermiogenesis and spermatozoa in Diplomystes mesembrinus
Authors: Quagio‐Grassiotto I. , Oliveria C. , Gosztonyi A. E.
Published: April 2005

Spermiogenesis in Diplomystes mesembrinus, one of the most primitive species from the Siluriformes, occurs in cysts. Differentiation of spermatids is characterized by chromatin compaction, flagellum development, nuclear fossa formation, rotation of the nucleus, and excess cytoplasm elimination. The spermatozoon head is round, the nucleus contains highly condensed chromatin clusters, the midpiece is short, the axoneme shows a 9 +2 pattern with two discrete lateral projections, and the acrosome is absent. The nuclear fossa penetrates deeply into the nucleus, including the centriolar complex and the start of the axoneme. The single large C‐shaped mitochondrion surrounds the initial segment of the axoneme. The structural features of D. mesembrinus spermatozoon are similar to the Clupeiformes.
Fish condition analysis by a weighted least squares procedure: testing geographical differences of an endangered Iberian cyprinodontid
Authors: Vila‐Gispert A. , Moreno‐Amich R.
Published: April 2005

A weighted procedure for analysing fish condition, when conventional ANCOVA assumptions cannot be assumed because the coefficients of regression and residual variances were not equal among groups, proved adequate for most data sets. Data for an Iberian cyprinodontid fish were used to demonstrate the proposed method.
Patterns of ion regulation in acidophilic fish native to the ion‐poor, acidic Rio Negro
Authors: Gonzalez R.J. , Wilson R.W.
Published: April 2005

The Na+ uptake mechanism of cardinal tetras Paracheirodon axelrodi displayed specialization for operation in dilute waters of the amazonian Rio Negro. Kinetic analysis revealed low Km and high Jmax values which ensure high rates of uptake even in very dilute waters. In contrast, Na+ uptake of angelfish Pterophyllum scalare did not appear to be specialized for dilute waters at all, with much higher Km and lower Jmax values. Na+ uptake in cardinal tetras was high and completely unaffected down to pH 3·5, while uptake in angelfish was much lower and progressively inhibited by dropping pH; it was completely shut down at pH 3·5. During chronic exposure to pH 4·0 and 3·5, angelfish showed no ability to restore Na+ uptake and at pH 3·5 all individuals died between day 3 and 6 presumably due to small, but steady loss of Na+. At low pH, both species displayed a strong ability to prevent stimulation of diffusive Na+ losses. In angelfish, the ability to control diffusive ion losses at low pH was related to a high branchial affinity for Ca2+. For cardinal tetras, the rate of Na+ loss appeared to be independent of water Ca2+ concentration. The specializations of cardinal tetras are similar to other characid fishes tested, but the results for angelfish reveal a new pattern of ion regulation in acidophilic species from the Rio Negro. The differences between the species may be the result of their different distributions, cardinal tetras are found in the central Rio Negro region while angelfish are more peripheral, or they may reflect phylogenetic differences.
Can goby spermatozoa pass through the filament adhesion apparatus of laid eggs?
Authors: Giulianini P. G. , Ota D. , Marchesan M. , Ferrero E. A.
Published: April 2005

SEM observations of the egg adhesion of grass goby Zosterisessor ophiocephalus show perforations between filament insertions on the basal plate. These are adequate in size to let through spermatozoa which eventually reach the micropyle. This accounts for post‐attachment egg fertilization occurring naturally and in artificial fertilization experiments.
Long‐term effect of radio‐tagging on the swimming performance of pikeperch
Authors: Koed A. , Thorstad E. B.
Published: April 2005

Critical swimming speed of adult pikeperch Stizostedion lucioperca (LT 53–72 cm) that had spent one year in the field after tagging with body‐implanted radio transmitters were not affected compared with untagged controls.
Types of the Italian freshwater goby Padogobius nigricans (Canestrini, 1867)
Authors: Nocita A. , Vanni S.
Published: April 2005

The location of type material of the Italian freshwater goby Gobius fluviatilis var. nigricans Canestrini, 1867 was previously unknown. However, syntypes of this taxon have been identified now in the Museo Universitario di Storia Naturale e della Strumentazione Scientifica, Modena, Italy. Also this material is the type series of Gobius avernensis, described by Canestrini in 1868. Vestigial predorsal squamation in Padogobius nigricans is noted.
Genetic differences in physiology, growth hormone levels and migratory behaviour of Atlantic salmon smolts
Authors: Nielsen C. , Holdensgaard G. , Petersen H. C. , Björnsson B. Th. , Madsen S. S.
Published: April 2005

Out of five strains of Atlantic salmon Salmo salar of 1+ years released upstream of a fyke net in the River Gudenaa in 1996, three, Lagan, Ätran and Corrib, migrated immediately, 50% of the recaptured fish reaching the net in 3–6 days. Burrishoole and Conon fish migrated with a 15–19 day delay. Smolt development in 1997 at the hatchery showed a spring surge in gill Na+, K+‐ATPase activity in all strains which was correlated with increased seawater tolerance. Differences in the timing of gill enzyme development matched the observed migration pattern well. Lagan, Ätran and Corrib strains reached high enzyme activity earlier than the Burrishoole and Conon strains, and strains with delayed enzyme development and migration showed a delayed regression of seawater tolerance compared with the early strains. Inter‐strain differences in plasma growth hormone profiles could not be related to the observed patterns of Na+, K+‐ATPase and seawater tolerance development. The study gives evidence of genetic influence on the timing and intensity of smolting and subsequent migration in Atlantic salmon.
Haematological and physiological responses of brook charr, to untreated and limestone‐neutralized acid mine drainage
Authors: Cole M. B. , Arnole D. E. , Watten B. J. , Krise W. F.
Published: April 2005

Brook charr, Salvelinus fontinalis, exhibited depressed plasma sodium and elevated plasma glucose concentrations in untreated acid mine drainage effluent (AMD), at two dilutions. Plasma sodium and glucose concentrations remained stable in treated AMD, pulsed, fluidized beds of limestone and carbon‐dioxide pre‐treatment of influent, and in AMD‐free water. Results indicate that effluents produced by this treatment system were not toxic to these fish, despite still containing moderate concentrations of manganese (3–4 mg l‐1 following dilution in exposure systems), and provide justification for field deployment and further biological testing of this treatment in the field.
Depth selection behaviour during activity cycles of juvenile plaice on a simulated beach slope
Authors: Burrows M. T.
Published: April 2005

Juvenile plaice Pleuronectes platessa on a sand slope in a laboratory tank showed depthselection behaviour consistent with offshore migration by day and onshore by night, as seen in natural conditions. Plaice stayed deep (0·5 m) and avoided the shallowest water (<10 cm depth) during light periods, but ventured up the slope and into the shallows in darkness. The freshly caught fish showed circatidal cycles of activity, but showed no change in depth selection between periods of high (time of expected high water) and low activity (expected low water). This suggests that changing direction of movements in tidal migration is controlled by responses to changing environmental conditions. Further analysis showed movements of fish up the slope to be slower, covering less distance and with shorter pauses in between than moves down the slope. Frequency, distance travelled and speed of moves up and down the slope did not change with tidal or light‐dark cycles, and so such modulation could be ruled out as a mechanism for migration.
Failure to induce over‐compensation of growth in maturing yellow perch
Authors: Hayward R. S. , Wang N.
Published: April 2005

Unlike juvenile F1 male bluegill Lepomis macrochrus× female green sunfish L. cyanellus, maximized episodes of compensatory growth (CG) in 2 year yellow perch Perca flavescens did not surpass control masses because internal regulation caused abrupt appetite reduction upon catch‐up. Together, the hybrid sunfish study and present work indicate that CG‐maximizing feeding schedules and absence of an internal growth limiting mechanism are both required to produce substantial growth overcompensation (GOC). The less vigorous and less resilient CG responses of the yellow perch relative to those of the similarly fed hybrid sunfish appear indicative of the lack of GOC capacity in the former. This contrast, and results of previous studies are interpreted to suggest that GOC capacity may be limited to early life stages of fishes which have a substantial reproductive potential but are at high risk of mortality due to their small size. The possibility that GOC capacity is time‐of‐year‐dependent and species‐specific is considered also. Food deprivation periods that produced the strongest CG responses differed for male (2 days) and female (12 days) yellow perch. Among controls fed without restriction, growth rate and growth efficiency of female yellow perch exceeded those of males two‐fold, however, males showed a greater capacity to catch‐up to same‐sex controls when undergoing CG. A feeding schedule using maintenance feeding v. food deprivation to elicit CG yielded the most rapid catch‐up to control masses in the yellow perch. Such feeding schedules may produce even greater GOC than was achieved previously in hybrid sunfish, where feeding schedules involving food deprivation were employed.
A preliminary test of the transitional growth spurt hypothesis using the protogynous coral trout Plectropomus maculatus
Authors: Adams S. , Williams A. J.
Published: April 2005

Estimates of back‐calculated size at age provided no evidence of a growth spurt following sexual transition in the protogynous serranid Plectropomus maculatus. The results suggested that mature females that had a large size at age early in life changed sex to male.