bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphological variation and taxonomic status of Altai osmans, Oreoleuciscus, from the upper reaches of the Ob River system
Authors: Golubtsov A. S. , Berendzen P. B. , Annett C. A.
Published: April 2005

The morphology of the endemic Altai osmans Oreoleuciscus spp. (Cyprinidae), from headwaters of the Ob tributaries in the Altai Republic (Russia), Terekhol Lake in the Tuva Republic (Russia), and the Chovd Gol River drainage and related bodies of water (Mongolia), where they are one of only four fish species occurring in most bodies of water were examined. Their high degree of morphological variation makes species determination problematical. Analysis of six meristic counts and principal component analysis (PCA) of 21 morphological measurements discriminated two species, Oreoleuciscus potanini and O. humilis . The results suggest that only O. potanini occurs in the upper reaches of the Ob system. The systematics and biogeography of Oreoleuciscus are discussed.
The effect of stress and exercise on post‐mortem biochemistry of Atlantic salmon and rainbow trout
Authors: Thomas P. M. , Pankhurst N. W. , Bremner H. A.
Published: April 2005

Freshwater Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss responded similarly to increase in water flow (exercise), reduction in holding tank water level (stress), or 30 min chasing with water level reduction (stress and exercise). Stress generally resulted in elevated plasma cortisol, above the control. Fish responded to stress and exercise combined, with elevated lactate and [H+] which was sometimes associated with elevated plasma cortisol. These changes were combined with a depletion of the muscle adenylate pool. Post‐mortem, this resulted in an increase in the rate of onset of rigor, and a higher and sometimes sustained muscle proton load. Both species produced predominantly inosine as opposed to hypoxanthine, for up to 72 h of ice storage. This study shows that the physiological disruption in Atlantic salmon and rainbow trout caused by simulated harvest conditions of stress and exercise, results in mostly transient changes in post‐mortem muscle biochemistry. These changes lead to an earlier onset and resolution of rigor, and lower post‐mortem muscle pH in comparison to the control.
Molecular phylogeny of the humbug damselfishes inferred from mtDNA sequences
Authors: Bernardi G. , Crane N. L.
Published: April 2005

The damselfish genus Dascyllus comprises nine species of both large‐ and small‐bodied fishes distributed over the entire Indo‐West Pacific. Most members of the genus have polygynous mating systems with protogynous sex change, while others are promiscuous with no sex change. Hypotheses linking presumed phylogenetic relationships with body size, sex change and mating structure have been proposed previously. However, lack of a strong phylogenetic hypothesis has prevented the careful testing of such hypotheses. In this study, the phylogenetic relationships between Dascyllus species based on mitochondrial DNA sequences (cytochrome b and 16SrRNA) have been established. The data also shed light on the relationship between mating structure and body size, as well as on the complex biogeographical patterns of the genus.
Otolith microstructure during the pelagic, settlement and benthic phases in burbot
Authors: Fischer P.
Published: April 2005

During the pelagic larval phase of burbot Lota lota L., the pattern of otolith increments changes, showing three, clearly distinguishable growth sectors: a first sector with faint increments, difficult to enumerate, comprising an average (±S.D.) of 17˙5±6˙7 increments, a second sector with distinct increments comprising an average of 33˙1±7˙6 increments and a third sector where increments again become faint and difficult to enumerate. Laboratory experiments conducted in parallel to the field investigation showed that settlement occurs after the formation of this third, faint sector and is marked by the formation of numerous accessory growth centres within the range of three to five daily increments. There was a strong linear relationship between sagittal width and total length of the burbot (r2=0˙928) over the range examined. Significantly different growth rates were calculated for the three otolith sectors (faint, distinct, faint) in burbot larvae, indicating large environmental changes during their pelagic larval phase in Lake Constance. These results suggest that inshore migration of burbot larvae does not take place in the warm epilimnetic surface waters but via an alternative pathway, the cold hypolimnion or profundal zone.
The effect of prey mobility, prey contrast, turbidity and spectral composition on the reaction distance of Gobiusculus flavescens to its planktonic prey
Authors: Utne‐Palm A. C.
Published: April 2005

The reaction distance of Gobiusculus flavescens to mobile and immobile copepod prey of different transparency was studied in water conditions with different turbidity levels or spectral composition. Both prey contrast (red or transparent Calanus spp.) and prey mobility caused reaction distance of G. flavescens to increase. The effect of prey mobility or prey transparency on reaction distance was independent of turbidity level. Longest reaction distances were measured for mobile and red prey at intermediate turbidity levels (10–20 JTU). Contrast threshold decreased with increasing turbidity. Although contrast of red and transparent copepod prey increased with increasing wavelength, longest reaction distances were observed at shorter wavelengths (blue–green). Lowest contrast threshold was found at shorter wavelengths. Visual pigments of G. flavescens are adapted to its natural environment. Both turbidity and spectral composition influenced G. flavescens contrast threshold.
The sailfin dory, a first British record
Authors: Swaby S. E. , Potts G. W.
Published: April 2005

A sailfin dory Zenopsis conchifer was caught oV the south coast of Britain in 1995. This species has been increasing in northern European waters and this record represents the first in British waters.
Shifts of food habit and jaw position of white‐spotted charr after damming
Authors: Morita K. , Suzuki T.
Published: April 2005

Stomach fullness of white‐spotted charr, Salvelinus leucomaenis did not differ significantly between above‐dam (allopatric with masu salmon) and below‐dam (sympatric with masu salmon) areas, but stomach contents did. Juveniles (1+) below the dam consumed relatively more aquatic insects (benthic prey), and those above the dam consumed relatively more terrestrial insects (drifting prey), but there was no difference in the diet of >2+ fish between areas. The mouths of juveniles above the dam were more terminal than those of fish below the dam. The adaptive significance of these differences is discussed in relation to differences in fish assemblages. 1999 The Fisheries Society of the British Isles
Prior residence, body size and the dynamics of territorial disputes between male freshwater angelfish
Authors: Chellappa S. , Yamanoto M. E. , Cacho M. S. R. F. , Huntingford F. A.
Published: April 2005

Territorial interactions between pairs of size mismatched, sexually mature male angelfish Pterophyllum scalare were investigated in three different conditions: with the larger fish resident (the large resident condition), with the smaller fish resident (the small resident condition) and in a neutral territory (the neutral condition). In the two resident conditions, approximately half of the intruders had previously held territories and half had not. In all categories of fight, one fish showed submissive postures and lost the fight; eventual losers performed both attack and threat at a lower rate than eventual winners. Attack rate declined as the encounter progressed, while rate of performance of threat postures increased. In fights on neutral territories, the larger fish won all fights. In all fights with a resident‐intruder asymmetry, the resident fish won the encounter, regardless of relative size. In eventual winners but not in eventual losers, levels of attack were lowest in the neutral encounters. In the small resident condition, levels of attack (corrected for activity of the resident) were lower in intruders that had previously held a breeding territory. Relative size influenced behaviour shown during fights, in that overall intensity was correlated negatively with size differential in all conditions. Thus although prior residence is the primary determinant of the outcome of territorial encounters in this species, both relative body size and prior possession of territory also influence the nature of the interaction.
Resource sharing among cod, haddock, saithe and pollack on a herring spawning ground
Authors: Høines Å. S. , Bergstad O. A.
Published: April 2005

Cod Gadus morhua, haddock Melanogrammus aeglefinus, pollack Pollachius pollachius and saithe Pollachius virens were abundant fishes on herring Clupea harengus spawning grounds o. southwestern Norway. Their diets were species specific and ontogenetic changes were similar to patterns observed in other areas, indicating both inter‐ and intraspecific resource sharing. However, strong interspecific diet overlap occurred when cod and pollack preyed upon sandeel Ammodytes marinus, and when all the gadoids fed on herring eggs during the herring spawning season in the spring. These prey items were very abundant and the extensive diet overlap may not reflect strong competitive interaction.
Microsatellites reveal fine‐scale genetic structure in stream‐living brown trout
Authors: Carlsson J. , Olsén K. H. , Nilsson J. , ØVerli Ø. , Stabell O. B.
Published: April 2005

MultilocusFSTestimates revealed a pronounced genetic structure at six microsatellite loci in brown troutSalmo truttain Nordre Finnvikelv, with at least three breeding units that remained stable over time. Significant differences in allele frequencies were found between five sections within a 3‐km range, even when no physical barriers prevented fish from migrating between sections. It is argued that geological structures may rise to patterns resembling isolation by distance. Seemingly, the most important factor causing genetic differentiation in Nordre Finnvikelv is genetic drift in small populations that are geologically subdivided by a tributary and by impassable waterfalls. Some correlation between previous behavioural observations and genetic structures were found.
Stress‐induced changes in concentrations of plasma sex steroids in black bream
Authors: Haddy J. A. , Pankhurst N. W.
Published: April 2005

Cortisol levels of black bream Acanthopagrus butcheri at capture did not change with time of day, gonadal stage or season and were 1·9±0·2 and 2·8±0·4 ng ml−1 for male and female fish, respectively. Confinement resulted in significantly elevated cortisol levels at all time periods; however, levels after 24 h of confinement were significantly lower than peak cortisol levels (15 min for males and 1 h for females). Confinement stress resulted in reduced levels of 17β‐oestradiol (E2) and testosterone (T) within 1 h in sexually mature females. In mature males, suppression of T and 11‐ketotestosterone (11KT) occurred after 30 min and 6 h of confinement, respectively. The relationship between confinement stress and levels of 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β P) was more complex, with levels in males being elevated after 15 min and 24 h and suppressed after 6 h of confinement. In contrast, 17, 20β P levels in females were elevated after 1 h of confinement. In regressed females, plasma E2 and T concentrations were low at capture and were not affected by confinement stress whereas plasma 17, 20β P was elevated within 1 h. This study indicates that stress exerts a rapid inhibitory effect on gonadal steroidogenesis.
Comparative morphology of male reproductive systems in Mediterranean blennies (Blenniidae)
Authors: Richtarski U. , Patzner R. A.
Published: April 2005

The male reproductive organs of 16 species of Mediterranean Blenniidae (Aidablennius sphynx, Blennius ocellaris, Coryphoblennius galerita, Lipophrys adriaticus, L. canevae, L. dalmatinus, L. nigriceps, Parablennius gattorugine, P. incognitus, P. sanguinolentus, P. rouxi, P. tentacularis, P. zvonimiri, Paralipophrys trigloides, Salaria pavo and Scartella cristata) consist of pairs of testes, testicular glands, spermatic ducts, and blind pouches. Three main types of accessory sex organs were found by comparing the external morphology of the male gonads. Differences between species were observed in the volume of the testicular gland in relation to the volume of the testis and in the size and length of the spermatic ducts, and blind pouches. The anatomy of the testicular glands of all species investigated do not differ. Each gland consists of ducts that appear to be tubules which terminate at the testis periphery on one side and at the spermatic duct on the other side. Contrary to previous claims, A. sphynx has no fat body in place of the testicular gland; the gland of this species was not distinguishable from that of the other species investigated. In the Lipophrys species, in P. trigloides, and in B. ocellaris, a transition zone between testis and testicular gland is present. The testicular blind pouches empty into the spermatic ducts, into the ureter, or separately on the genital papilla. In most species, the epithelium has no or low folds, while in S. pavo it possesses high folds that nearly fill the lumen of the blind pouches. The morphological results are discussed in connection with taxonomy, ecology, and behaviour of the fishes.
New discovery of the Ukrainian brook lamprey in Croatia
Authors: Holčík J. , Delić A.
Published: April 2005

The Ukrainian brook lamprey Eudontomyzon mariae was collected in two streams belonging to the Sava river basin in Croatia. The great variation in morphological characters of this species is emphasized and its description is augmented. Clinal variation in the trunk myomeres, total length and the oral disc dentition is detected.
Comparative morphology and diet of young cichlids in the dammed Sinnamary river, French Guiana, South America
Authors: Ponton D. , Mérigoux S.
Published: April 2005

The growth of most mensural characters of Krobia guianensis and Crenicichla saxatilis during early development was explained by a split regression indicating inflection in allometry at specific standard lengths. Double‐centred PCA revealed morphological transformations during ontogeny mostly under the influence of the maximum body depth and the maximum caudal peduncle width, the area of the caudal fin and the horizontal diameter of the eye contributing also, but to a lesser extent. Young K. guianensis switched to larger prey at the end of the period when the growth of most of their studied mensural characters demonstrated an inflection, but young C. saxatilis changed their diet at a much smaller size than that at which an inflection occurred. However, in the lower reservoir sites, most young juveniles of K. guianensis and C. saxatilis did not switch to larger items during their ontogeny and micro‐crustaceans occurred more frequently in their diet. It is hypothesized that the low net energy gained when eating such small prey may explain why the young of both species were thinner at these sites than in their undisturbed habitats. If food resources of young cichlids do not improve in the Petit‐Saut reservoir, it is hypothesized that these species will develop stunted populations there.
Variation in the intraspecific relationship between fish length and intensity of parasitic infection: biological and statistical causes
Authors: Poulin R.
Published: April 2005

In a meta‐analysis, the overall mean correlation between fish length and the intensity of parasitic infections derived from 76 different host–parasite species was positive but weak and non‐significant, following corrections for sample size. Whether the parasites were acquired by ingestion or by skin contact had no influence on the strength of the relationship. For cestodes, larval digeneans, and gnathiid isopods, however, the mean correlation between fish length and intensity of infection was significant. Some statistical parameters influenced the strength of the raw correlations computed within samples and thus led to over‐ or under‐estimation of the true relationship. Sample size correlated negatively with the value of the correlation coefficients, whereas range in both fish lengths and intensities of infection correlated positively with the value of the correlation coefficients. Distinguishing between statistical noise and the biological processes shaping the sizev.intensity relationship will be important if this relationship is to be incorporated into fish population models.
Intestinal morphology in growth hormone transgenic coho salmon
Authors: Stevens E. D. , Devlin R. H.
Published: April 2005

In two GH transgenic coho salmon Oncorhynchus kisutch, the surface area of the intestine was 2·2 times that of control salmon and the growth rate was about twice that of controls. It seems likely that the enhanced intestinal surface area is a compensatory feature that is manifested in fast growing salmonids.
Compensatory growth, feed utilization and activity in gibel carp, following feed deprivation
Authors: Qian X. , Cui Y. , Xiong B. , Yang Y.
Published: April 2005

Following a period of food deprivation, gibel carp compensated for growth through increased feed intake and conversion efficiency, but increased conversion efficiency was not achieved by increasing digestibility or reducing activity.
Gene flow in Trinidadian guppies
Authors: Becher S. A. , Magurran A. E.
Published: April 2005

In 1957, guppies Poecilia reticulata from the Caroni drainage were introduced into habitat suitable for (but devoid of) guppies upstream of a waterfall in the Turure River of the Oropuche drainage. Previous allozyme studies, describing gene flow due to both sexes, showed that guppies downstream of the waterfall barrier represent an admixture of native and introduced genotypes. Using a polymerase chain reaction‐restriction fragment length polymorphism assay of the highly divergent mitochondrial NADH2 gene only 12% of genotypes in the downstream population were shown here to correspond to the native matriline. The prevalence of introduced genotypes is discussed in the context of sexual conflict theory.
The influence of temperature on the onset of first maturity in sea bass
Authors: Pawson M. G. , Pickett G. D. , Witthames P. R.
Published: April 2005

Oocyte development was aborted and full maturity did not occur in virgin female sea bass Dicentrarchus labrax unless they remained in water above 10° C during the main period of gonad development. There was no difference in the condition factors of females with high or low IG values in March, which indicates that retarded gonadal development was not necessarily due to poor body condition or nutritional state. It is suggested that the extended duration of the adolescent phase of female bass around southern Britain is a response to their environment, rather than an intrinsic aspect of the species'biology.
Seasonal changes in the hypo‐osmoregulatory ability of brook charr: the role of environmental factors
Authors: Claireaux G. , Audet C.
Published: April 2005

In winter, brook charr Salvelinus fontinalis demonstrated poor osmoregulatory ability. Saltwater (SW) transfer resulted in sharp increases in plasma osmolality and chloride levels, a decrease in white muscle water content and high mortality. A clear improvement of the hypo‐osmoregulatory mechanism e.ciency was observed in spring; by May or June, fish achieved full acclimation within 1 week of SW transfer. In early fall, the time needed to restore osmotic and ionic balance increased once again. A high level of stress was detected only in winter and fall, as indicated by plasma cortisol and glucose concentrations. Great improvement in osmotic and ionic regulation was observed when brook charr were transferred to 80 C SW in February and April while impaired SW adaptability was recorded in individuals transferred to 2·50° C SW in June and August. Temperature itself was more important than a thermal gradient between fresh and salt water. Stress indicators substantiate this temperature‐dependent improvement of osmotic and ionic regulation in brook charr. The results support the hypothesis of a minor contribution of cortisol to hypo‐osmotic regulation in brook charr, as the cortisol response always seemed to be associated with stress in the experiments.
The effect of food deprivation and refeeding on the liver, thyroid hormones and transthyretin in sea bream
Authors: Power D. M. , Melo J. , Santos C. R. A.
Published: April 2005

There was a significant reduction in body weight of sea bream Sparus aurata and the hepatosomatic index after 3 weeks food deprivation. Liver biochemical indices and morphology were altered by food deprivation, there was a loss of eosin staining in hepatocyte cytoplasm and the appearance of large depleted vacuoles. Cell and nuclear area were significantly reduced (P<0·001) and did not return to control values after 1 week of refeeding. The water, lipid, glycogen and protein content of the liver was significantly reduced by 3 weeks fasting but recovered rapidly after 1 week refeeding. Food restriction also had a marked effect on circulating thyroid hormones and the concentration of plasma T3 (33·98±12·47 ng ml‐1) and T4 (16·54±9·5 ng ml‐1) was significantly (P 0·001) lower than the control (66·52±13·4 and 56·83±7·3, respectively). Refeeding for 1 week restored circulating T3 (P< 0·05) close to control levels but did not significantly affect the concentration of T4. Northern blotting with an homologous probe for transthyretin (TTR) demonstrated clearly the expression of a single mRNA transcript of 0·7 kb for this protein in the liver. The level of TTR message was substantially reduced below control levels in the liver of fasted fish and 1 week refeeding failed to restore expression.
The effects of heat shock and acclimation temperature on hsp70 and hsp30 mRNA expression in rainbow trout: in vivo and in vitro comparisons
Authors: Currie S. , Moyes C. D. , Tufts B. L.
Published: April 2005

Heat shock (25° C) of 10° C‐acclimated rainbow trout Oncorhynchus mykiss led to increases in heat shock protein 70 (hsp70) mRNA in blood, brain, heart, liver, red and white muscle, with levels in blood being amongst the highest. Hsp30 mRNA also increased with heat shock in all tissues with the exception of blood. When rainbow trout blood was heat shocked in vitro, both hsp70 and hsp30 mRNA increased significantly. In addition, these in vitro experiments demonstrated that blood from fish acclimated to 17° C water had a lower hsp70 mRNA heat shock induction temperature than did 5° C acclimated fish (20 v. 25° C). The hsp30 mRNA induction temperature (25° C), however, was unaffected by thermal acclimation. While increases in hsp70 mRNA levels in blood may serve as an early indicator of temperature stress in fish, tissue type, thermal history and the particular family of hsp must be considered when evaluating stress by these molecular means.
Territorial boundaries of the male beaugregory damselfish
Authors: Itzkowitz M. , Ludlow A. , Haley M.
Published: April 2005

On six separate occasions during a two month period, there were no significant differences in mean attack distances by territorial male beaugregory damselfish Stregastes leucostictus against male conspecifics, bluehead wrasse Thalassoma bifasciatus and striped parrotfish Scarus iserti. Feeding areas and patrolling areas were typically smaller than attack distances. The presence or absence of eggs, or the quantity of eggs within the male's territory also was not significantly correlated with attack distances. © 2000 The Fisheries Society of the British Isles
Early survival and growth in populations of grayling with recent common ancestors—field experiments
Authors: Haugen T. O.
Published: April 2005

Among eight populations of graylingThymallus thymallusthat shared common ancestors 8–28 generations earlier, mean egg mortality ranged between 1·2 and 59·8%; mortality during yolk sac absorption was low (0middot;0–8middot;0%) and mean survival to swim‐up was high (90–97%), with two exceptions (20% and 50%). Survival probabilities differed significantly among populations, even after statistically adjusting for size at swim‐up and water depth, water velocity, gravel size and temperature. Development time from fertilization to first observed swim‐up was significantly different among populations, ranging between 27 to 40 days, or 264 to 280 degree‐days. Mean specific growth rates during the first external feeding period varied between 1·2 and 2·0% day‐1among populations. Population‐specific growth rates were independent of temperature. Rates of divergence were of the same order as in other salmonid studies showing rapid evolution. The phenotypic differences may be due partly to genetic differentiation among the populations.
Analysis of motility parameters from paddlefish and shovelnose sturgeon spermatozoa
Authors: Cosson J. , Linhart O. , Mims S. D. , Shelton W. L. , Rodina M.
Published: April 2005

Ninety to 100% of paddlefish Polyodon spathula were motile just after transfer into distilled water, with a velocity of 175 μm s‐1, a flagellar beat frequency of 50 Hz and motility lasting 4–6 min. Similarly, 80–95% of shovelnose sturgeon Scaphirhynchus platorynchus spermatozoa were motile immediately when diluted in distilled water, with a velocity of 200 μm s‐1, a flagellar beat frequency of 48 Hz and a period of motility of 2–3 min. In both species, after sperm dilution in a swimming solution composed of 20 mM Tris–HCl (pH 8·2) and 20 mM NaCl, a majority of the samples showed 100% motility of spermatozoa with flagella beat frequency of 50 Hz within the 5 s following activation and a higher velocity than in distilled water. In such a swimming medium, the time of motility was prolonged up to 9 min for paddlefish and 5 min for sturgeon and a lower proportion of sperm cells had damage such as blebs of the flagellar membrane or curling of the flagellar tip, compared with those in distilled water. The shape of the flagellar waves changed during the motility phase, mostly through a restriction at the part of the flagellum most proximal to the head. A rotational movement of whole cells was observed for spermatozoa of both species. There were significant differences in velocity of spermatozoa between swimming media and distilled water and between paddlefish and shovelnose sturgeon.
Genetic variation in mortality of chinook salmon during a bloom of the marine alga Heterosigma akashiwo
Authors: Hard J. J. , Connell L. , Hershberger W. K. , Harrell L. W.
Published: April 2005

Mortality in a netpen‐reared population of 3‐year‐old chinook salmon Oncorhynchus tshawytscha during an extensive 1997 bloom of the alga Heterosigma akashiwo in Puget Sound, Washington, was low (7·2%), and corresponded to a reduction in variance effective population size of 9·4%. Under a liability threshold model, the heritability of mortality (± S.E.), based on paternal half‐sibs, was estimated at 0·15 ± 0·04. No significant genetic variation was detected for date of death. Despite the low overall mortality, the consequences for variation in family size underscore the importance of maximizing genetic variation in cultured fish populations later released to the wild as a precaution against mortality and losses of genetic variation over the life cycle. The pattern of family variation in response to this algal bloom provides evidence for potentially selective mortality of anadromous salmonids in the marine environment during natural perturbations.
Induction of spermiation in common carp after enhanced intestinal uptake of sGnRH‐A and Pimozide
Authors: Roelants I. , Mikolajczyk T. , Epler P. , Ollevier F. , Chyb J. , Breton B.
Published: April 2005

The inherent ability of the carp Cyprinus carpio gut to absorb intact salmon gonadotropin hormone‐releasing hormone analogue (sGnRH‐a)+Pimozide (Pim), without loss of their bioactivity is very limited. Artificial intestinal absorption enhancement boosted sGnRH‐a and Pim induced GtH II release and milt production significantly. The intraperitoneal route of administration was more effective than the oral one. A potential application of the oral route for peptidergic drug delivery and the possibility of developing a dietary delivery system is discussed.
Male trait distribution determined alternative mating tactics in guppies
Authors: Jirotkul M.
Published: April 2005

The distribution of the percentage of the body of male guppies Poecilia reticulata covered with orange coloration influenced alternative mating tactics. At 15% mean coverage, male guppies interfered with other courting males more and engaged in courtship activities longer than males with 10% mean coverage. When males were tested in a situation with a wide variety of male types, males switched among females less frequently than when the variance among males was low.
Branchial acid‐base transfers in the euryhaline oyster toadfish during exposure to dilute sea water
Authors: Claiborne J. B. , Compton‐Mccullough D. , Walton J. S.
Published: April 2005

Sea water dilution (to 5% and 1% of sea water) induced a reversible, plasma metabolic acidosis in a euryhaline teleost (the oyster toadfish, Opsanus tau). Net H+ transfer between the fish and the water decreased in both low salinity exposure (LSE) groups during the first week of exposure and ΔH+ returned to normal after ∼10 days of 5% LSE, but not during 1% LSE.
First record of the bluespotted cornetfish from the Mediterranean Sea
Authors: Golani D.
Published: April 2005

Three specimens of the Indo‐Pacific Bluespotted cornetfish Fistularia commersonii are recorded for the first time from the Mediterranean. The presence of this species in the Mediterranean is due to migration from the Red Sea via the Suez Canal.
Food consumption and daily feeding periodicity: comparison between pelagic and demersal whiting in the North Sea
Authors: Pedersen J.
Published: April 2005

Pelagic North Sea whiting Merlagius merlangus fed at night, while demersal whiting fed by day. The estimated specific daily ration ranged from 4·38 to 7·84% in 1992 and from 3·99 to 10·31% in 1993 using the in situ rate of gastric evacuation. Using Andersen's evacuation model the specific daily ration ranged from 0·41 to 1·66% in 1992 and from 0·78 to 1·75% in 1993. The specific daily rations were significantly different where energy density of stomach content by length class of whiting was significantly different between the two layers and years. The fact that daily ration was related to prey composition and energy density of the prey and spatial distribution of the whiting, demonstrates the need for a sampling design that includes both pelagic and demersal layers when quantifying the food consumption of whiting.
Influence of zooplankton and phytoplankton on the fatty acid composition of digesta and tissue lipids of silver carp: mesocosm experiment
Authors: Domaizon I. , Desvilettes C. , Debroas D. , Bourdier G.
Published: April 2005

Zooplankton appeared to be the major contributor to the diet of 1+ silver carp, whereas 3+ fishes exhibited a more evenly balanced spectrum between zooplankton and phytoplankton. The fatty acids profiles of digesta were influenced by zooplankton, particularly for 1+ silver carp. Together, fatty acid profiles of tank zooplankton and digesta were characterized by high proportion of 20 : 5ω3 and 20 : 6ω3. The fatty acids composition of the phytoplankton reflected the dominance of cyanobacteria and chlorophycea, with high quantities of 18 : 2ω6 and 18 : 3ω3. Although cyanobacteria accounted for >70% of the phytoplankton biomass ingested by the carp, fatty acids profiles of digesta were not influenced by phytoplankton fatty acids composition. The low digestive and conversion efficiency of Microcystis aeruginosa explain this absence of relation. The neutral lipids in silver carp tissues reflected poorly the fatty acids profiles in the diet, the semi‐natural conditions and the diet dominated throughout the study by zooplankton, led to little variation in tissues fatty acids. The phospholipids in the muscle, liver and peri‐intestinal fat were characterized by a rather low proportion of polyunsaturated fatty acids (PUFA) in both 1+ and 3+ fish. From a qualitative view point, cryptophycea, diatoms, and especially zooplankton are much more valuable food for the silver carp than cyanobacteria and desmid chlorophycea which are poor in long‐chain PUFA.
An evaluation of some electrical waveforms and voltages used for electric fishing; with special reference to their use in backpack electric fishing gear
Authors: Beaumoint W. R. C. , Lle M. J. , Rouen M. A.
Published: April 2005

Exponential pulse waveform in electric fishing gave a significantly poorer capture efficiency than other waveforms evaluated. Plasma cortisol levels were significantly and uniformly elevated after shocking by all waveforms. Mortality from the electric fishing was low, 0·2% overall, with few sub‐lethal effects. A 0·5 ms duration square pulse waveform had significantly higher catch‐per‐unit‐power than the other waveforms.
Differences in initial and acquired resistance to Ichthyophthirius multifiliis between populations of rainbowfish
Authors: Gleeson D. J. , McCalum H. I. , Owens I. P. F.
Published: April 2005

Wild‐caught rainbowfish Melanotaenia spp. originating from three isolated populations were infected with a quantified dosage of parasites Ichthyophthirius multifiliis in a controlled environment. The Melanotaenia eachamensis from Dirran Creek were much more susceptible to ichthyophthiriasis than were M. splendida from the Lake Tinaroo or Bluewater Creek populations. When the highly susceptible Dirran Creek rainbowfish were crossed with rainbowfish from a fourth population, Lake Eacham M. eachamensis, they produced hybrids with significantly higher resistance than pure‐bred Dirran Creek, but not higher than pure‐bred Lake Eacham fish. Hence, intraspecific hybridization increased resistance to I. multifiliis infection in M. eachamensis. Hosts from all three populations were much less susceptible to infection on their second exposure to the parasite. However, the Bluewater Creek population was better able to acquire immunity to I. multifiliis than either the Dirran Creek or Lake Tinaroo populations. It is tentatively suggested that there may be a link between the heterozygosity of populations of rainbowfish and their initial ability to resist infection by Ichthyophthirius multifiliis.
Growling for food: acoustic emissions during competitive feeding of the streaked gurnard
Authors: Amorim M. C. P. , Hawkins A. D.
Published: April 2005

The streaked gurnard Trigloporus lastoviza produced only one sound type, a growl, lasting up to 3 s and consisting of repeated groups of typically one to three pulses. The foraging fish followed two different strategies. In the first, the fish circled the feeding area, grasped a food item and fled, sometimes displaying aggressively to competitors. With this foraging strategy, fish usually made sounds as they circled, grasped and fled. Fish that growled while circling were more likely to grasp a food item subsequently than were silent fish. The second feeding strategy occurred when a fish had already ingested food or failed to get any. In this case, typically fish searched for food on the substratum or approached and touched other individuals that were feeding, sometimes grabbing food that was spat out during food handling by the other fish. Although payback experiments would be needed to draw firm conclusions on the communicative function of growling during competitive feeding in the streaked gurnard, the results suggest that sound production confers advantages to individuals competing for limited food resources.
Divergence in juvenile growth and life history in two recently colonized and partially isolated chinook salmon populations
Authors: Unwin M. J. , Quinn T. P. , Kinnison M. T. , Boustead N. C.
Published: April 2005

In 47 families of New Zealand chinook salmon,Oncorhynchus tshawytschaderived from two populations, differing in mean spawning date by 11–17 days and in juvenile life history, neither mean ovum weight nor mean time to hatch differed between the two populations, but substantial differences in mean family weight were apparent from 6 months after fertilization. Differences in growth rates from 12 to 24 months were relatively small, suggesting that most of the divergence in size and growth occurred during the first 6 months of life. There were differences in mean weight for families spawned 11–17 days apart, the approximate interval by which peak spawning date differs between the two populations, but these did not persist beyond 7 months. Differences between the two populations are consistent with their natural life history. The slower growing population experiences cooler temperatures during stream residence and is dominated by fish which spend a year in fresh water before seaward migration, whereas the faster growing population normally experiences warmer temperatures and migrates to sea in the first year of life. These results provide further evidence of life history evolution in partially isolated chinook salmon populations within 90 years (c.30 generations) of becoming established.
Body size and shoaling in fish
Authors: Hoare D. J. , Krause J. , Peuhkuri N. , Godin J.‐G. J.
Published: April 2005

Shoaling behaviour is generally described as a trade‐off between the anti‐predator benefits of living in groups and the costs of increased foraging competition. An individual's fitness varies as a function of shoal size and shoal composition, and this relationship is potentially body length dependent. As teleost fishes show indeterminate growth, many populations exhibit a broad range of individual body lengths. The latter is used as a criterion in active choice of shoaling companions, and shoals are often size‐assorted. This reduces predation risk through minimizing phenotypic oddity, and may reduce competition between size‐classes. There is some evidence for a positive relationship between shoal size and the body length of shoal members, although it remains unclear whether this is a result of active shoal‐size choice or a by‐product of the body length distribution of the population. Shoal membership is highly dynamic and individuals may maximize their fitness by switching frequently between groups of varying size and composition in response to changes in their physiological stage and the external environment. Fish shoals provide an excellent opportunity to investigate the functions and mechanisms of group living, and future studies should aim to take an integrated view of individual behaviours, group size and phenotypic composition when investigating group choice decisions.
Restoration of the taxon Lycodes marisalbi, with notes on its disjunct Arctic distribution
Authors: Møller P. R.
Published: April 2005

Examination of a large number of Lycodes specimens from the Arctic Ocean showed that western Canadian Arctic (Beaufort Sea) specimens, hitherto identified as Lycodes pallidus Collett, 1878 are identical with Lycodes marisalbi Knipovich, 1906 from the White Sea. Both populations have a ventro‐medio‐lateral lateral line system, not in accordance with the ventral and posterior medio‐lateral type of lateral line found in L. pallidus. Lycodes marisalbi, which has been regarded as a subspecies of L. pallidus since 1954, is hence restored as a valid taxon. A revised diagnosis, description and synonymy are given. The extended distribution range of L. marisalbi is probably disjunct (White Sea and Beaufort Sea), indicating a biogeographic pattern characterized by affinity to relatively shallow water with reduced salinity. Specimens from Franklin Bay (Beaufort Sea) with light vertical bars, previously assigned to Lycodes sagittarius McAllister, 1975 are here assigned to L. marisalbi, restricting L. sagittarius to include uniformly brown specimens only.
Observations on mass atresia and skipped spawning in northern Atlantic cod, from Smith Sound, Newfoundland
Authors: Rideout R. M. , Burton M. P. M. , Rose G. A.
Published: April 2005

Atlantic cod Gadus morhua were collected from Smith Sound, Newfoundland in January 1999. Visual examination of females (n=150) and males (n=126) revealed that some large fish (42–79 cm) had underdeveloped gonads. Histological examination of underdeveloped ovaries indicated that the majority of these females were undergoing mass resorption of oocytes and would not have spawned in 1999. Fish in this condition included females that were aborting their first attempt at maturation and females that had spawned the previous year but were failing to re‐ripen. Somatic and liver condition were significantly lower (P<0·05) for fish undergoing mass oocyte resorption than ripening females, suggesting that the interruption in the maturation cycle may have been related to insufficient nutrient storage. In males, testes of some adult fish were considered to be non‐reproductive as they showed no signs of ripening and probably would not have spawned in 1999. Liver condition was significantly higher (P<0·05) for non‐reproductive males than those that were ripening. Disruptions in male and female reproductive cycles may also have been related to water temperatures that were too cold (0–0·5° C) for successful gamete development. Immature gametes (perinucleolar oocytes in females; spermatogonia in males) showed no signs of breakdown in non‐reproductive individuals, suggesting that they retained the potential to develop and spawn gametes in 2000.
Sampling characteristics of two methods for capturing age‐0 fish in pelagic lake habitats
Authors: Tischler G. , Gassner H. , Wanzenböck J.
Published: April 2005

For the capture of rapidly developing and fast growing age‐0 Perca fluviatilis, a sampling precision of <0·2 could be achieved with both push‐netting and purse seining. Night catches obtained from purse seining showed predominantly and sometimes significantly higher densities. The push‐net system was appropriate for capturing newly hatched larvae and juveniles up to c. 30 mm LT. The small purse seine was appropriate for fish of 14–30 mm. For perch >30 mm, a 120×5 m purse seine was most suitable.
Incidence of physical injury of mature male parr in a natural population of brown trout
Authors: Broberg M. M. , Nielsen E. E. , Dieperink C.
Published: April 2005

In a brown trout Salmo trutta population, there was a much higher frequency of injuries among mature male parr than among immature or female parr. The quantitative data are discussed in relation to spawning success and overall fitness.
Identification of palearctic coregonid fish species using mtDNA and allozyme genetic markers
Authors: Politov D. V. , Gordon N. Yu. , Afanasiev K. I. , Altukhov Yu. P. , Bickham J. W.
Published: April 2005

Two types of molecular genetic markers were used for genetic identification of species and local stocks of palearctic coregonids (Coregonidae, Salmoniformes, Teleostei). Seven nominate species of whitefishes and ciscoes Coregonus, spp. of Eurasia Arctic Sea basin and inconnu Stenodus leucichthys nelma, represented by specimens from North America were studied. Using restriction analysis of PCR‐amplified products of the ND‐1 gene of mitochondrial DNA (mtDNA) and allelic composition at several allozyme loci discrimination was successful between C. lavaretus pidschian, Siberian whitefish, C. nasus, broad whitefish, C. autumnalis, Arctic cisco, C. migratorius, Baikal omul, C. peled, peled, and C. sardinella, least cisco. Muksun C. muksun, was indistinguishable from Siberian whitefish. Creatine kinase (CK) isozyme patterns and Rsa, I restriction patterns of ND‐1 were the most effective markers allowing discrimination among species. Intra‐specific differentiation in mtDNA was found in all species but was much less pronounced than inter‐species variation. In several specimens composite haplotypes typical of another species were found that reflect probable gene introgression by hybridization. A combination of mtDNA and nuclear genetic markers is suggested for reliable identification of both typical species representatives and hybrids.
The bulbus arteriosus of stenothermal and temperate teleosts: a morphological approach
Authors: Icardo J. M. , Colvee E. , Cerra M. C. , Tota B.
Published: April 2005

The bulbus arteriosus, ‘windkessel’, of several species of stenothermal and temperate teleosts has been studied by conventional light microscopy and electron microscopy. The bulbus wall is divided into an endocardium, ridges, and middle and external layers. The endocardium of all species shows moderately‐dense bodies, which vary widely although the significance is not known. The endocardium in Antarctic teleosts invaginates into the ridge tissue to form solid epithelial cords that show signs of active secretion related to protective substances. Cords also form in serranidic and sparidic species, but signs of active secretion are not evident. The ridges consist of cells within a filamentous meshwork. Ridge cells appear to be smooth muscle cells that undergo a phenotypic transition from the endocardium toward the middle layer. Middle layer cells are typical smooth muscle cells surrounded by a filamentous matrix. The appearance and composition of the extracellular matrix varies widely among species, with those from the Antarctic lacking collagen and elastin fibres. The external layer is a collagenous matrix that contains fibroblasts, blood vessels and nerves. In most Antarctic teleost species this layer lacks blood vessels, but contains nerve fibres. Some of these fibres could have a sensory function to control bulbus dilatation. The external layer of Trematomus bernacchii has the appearance of a germinal centre and may be involved in the immune humoral response. The epicardium is atight epithelium that may control passage of substances with the pericardial cavity.
Genetic differentiation of charrs in the Russian north and far east
Authors: Salmenkova E. A. , Omelchenko V. T. , Kolesnikov A. A. , Malinina T. V.
Published: April 2005

Genetic differences and relationships within charrs Salvelinus alpinus, northern and southern S. malma, S. taranetzi, S. levanidovi and S. leucomaenis, were studied by examination of 31–35 allozyme loci and PCR‐RFLP analysis of mtDNA segment (about 2600 bp) including the cytochrome b gene and D‐loop. Data for mtDNA were also obtained for samples of S. drjagini, S. albus and for European samples of S. alpinus. Generally allozyme and mtDNA segment analyses produced similar pictures of genetic divergence and relationships. The southern S. malma exhibited the greatest genetic variability (allozyme heterozygosity and mtDNA haplotype diversity). S. alpinus, S. malma, S. levanidovi and S. leucomaenis had fixed differences from one another at various allozyme loci, and differed in fixed (but polymorphic in S. malma) individual mtDNA haplotypes produced with MspI restrictase. Such genetic individuality is typical of distinct taxa. S. taranetzi is closest genetically to allopatric S. alpinus, but exhibited fixed differences from the northern S. malma in sympatry. In all samples of S. alpinus the only mtDNA haplotype was shared with S. drjagini.S. albus shared its single haplotype with the northern S. malma from the same locality. S. leucomaenis is differentiated from the other species to the greatest extent, possibly reflecting an early evolutionary divergence. Some evolutionary and taxonomic implications of the genetic relationships of charrs studied are discussed.