bluuebunny/crossref_metadata_2025 huggingface dataset:
The ageing phenomenon of turbot spermatozoa: effects on morphology, motility and concentration, intracellular ATP content, fertilization, and storage capacities
Authors: Suquet M. , Dreanno C. , Dorange G. , Normant Y. , Quemener L. , Gaignon J. L. , Billard R.
Published: April 2005

The deleterious effect of the ageing phenomenon of turbot spermatozoa was investigated in relation to the sampling date. Spermatozoa with a low or highly condensed chromatin and a middle piece containing numerous or a few vesicles were observed simultaneously 80 and 47 days before the beginning of the spawning period of the females. The middle piece of spermatozoa contained few vesicles, 39 days after the end of the reproductive period. At the same date, some spermatozoa appeared in which the plasma membrane was broken. Sperm motility, assessed just after collection in terms of arbitrary motility scores from 0 to 5, was significantly increased both at 10 and 60 s post‐activation, for samples collected 18 days after, 25 days before and 9 days after the beginning of the spawning period of the females, respectively compared to samples collected 6 days before, 55 days after and 88 days after the end of this period. A lower short‐term storage capacity was recorded at 10 and 60 s post‐activation for sperm samples collected 6 days before and 88 days after the end of the reproductive period, respectively compared to 18 days and 9 days after the beginning of the spawning period. At 60 s post‐activation, a higher motility of thawed spermatozoa was observed for samples collected 5 days before the beginning of the spawning period (motility recovery index: 86.4 ± 19.4%) compared to 71 days after the end of this period (55.0 ± 12.0%). The fertilizing capacity of sperm samples collected 61 days after the end of the spawning season (66.1 ± 14.6%) was significantly lower than that recorded for samples collected 34 days after the beginning of the spawning period (75.2±9.6%). On the contrary, there was no significant decrease in endogenous ATP content (31 days after the beginning of the spawning period, 14.53 ± 0.84; 48 days after the end of this period, 10.75 ± 5.26 nmol 10− 8 spermatozoa). Furthermore, sperm concentration significantly increased between the same dates (respectively 3.3 ± 0.8–9.4±4.8×109 spermatozoa ml−1).
Effects of the brain parasite Myxobolus arcticus on sockeye salmon
Authors: Moles A. , Heifetz J.
Published: April 2005

Parasitism with Myxobolus arcticus did not affect smolt size of sockeye salmon or their osmocompetence, but had a deleterious effect (P<0.001) on the swimming speed of naturally infected smolts. Parasitized fish had a mean swimming speed of 2.89 fork length s−1 (LF s−1) compared with 4.37 LF s−1 for unparasitized fish. The parasite probably impairs swimming ability by affecting the central nervous system, but this effect does not appear severe enough to limit the parasite's usefulness in stock separation.
Geographic variation in the maturity and growth schedules of English sole along the U.S. west coast
Authors: Sampson D. B. , Al‐Jufaily S. M.
Published: April 2005

Logistic regression analyses showed that the maturity v. length relationship for female English solePleuronectes vetulusvaried significantly among sampling locations from California to British Columbia in June–September. Stepwise analyses found that latitude, bottom gradient, bottom temperature and sediment type were all significant factors. Regression analyses of age at length from subsamples indicated that latitude, maturity and bottom sediment had significant effects on growth. Data from the aged subsamples showed significant differences among age classes in the length v. maturity relationship with older fish attaining maturity at smaller sizes than younger fish. On a coast wide basis the length and age at 50% maturity werec.230 mm and 4·7 years respectively. Growth rate and length at 50% maturity have decreased substantially relative to observations from the 1950s, but age at 50% maturity has increased.
Influence of water quality, habitat and species richness on brown trout populations
Authors: Eklöv A. G. , Greenberg L. A. , Brönmark C. , Larsson P. , Berglund O.
Published: April 2005

The influence of water quality, physical habitat and species richness on the occurrence, density and size of brown trout at 216 stream sites in southern Sweden was studied. Discriminant analysis showed that the occurrence of trout at a locality was largely determined by oxygen conditions and medium‐sized substrata. At localities where trout occurred, the density of + trout was highest in narrow streams with high oxygen concentrations. For older trout, >0+ in age, stream size and temperature were negatively related to density. Biotic factors also appeared to affect trout density, as trout density was inversely related to abundance of predators and coexisting species. Even intraspecific competition appeared to be important as length of 0+ trout was inversely related to trout density. It is suggested that improvements of water quality may be an effective way to restore sea trout populations in southern Sweden, especially in narrow streams where smolt production has the highest potential.
Diel feeding rhythms and daily food consumption of juvenile Atlantic salmon in the River Alta, northern Norway
Authors: Amundsen P.‐A. , Bergersen R. , Huru H. , Heggberget T. G.
Published: April 2005

Atlantic salmon fry (0+) sampled from the River Alta exhibited only minor differences in stomach content weights and feeding rates throughout diel periods, but feeding rates were generally lowest at night. In contrast, salmon parr (1+ to 3+) had large diel fluctuations in stomach content weight, with the largest weights usually being recorded during the night and early morning. Accordingly, their feeding rates were highest at night. This nocturnal feeding pattern was consistent throughout all sampling occasions, and appeared to reflect a persistent feeding periodicity in the salmon parr. The daily food consumption rates of both fry and parr were highest during midsummer and decreased towards autumn.
Nitrogenous excretion in the Antarctic plunderfish
Authors: Boyce S. J.
Published: April 2005

The nitrogenous excretion rates (total ammonia nitrogen, urea, and primary amines) of plunderfish Harpagifer antarcticus were related significantly to length and to wet mass (mass exponents of 0·94, 1·01, 1·07 and 0·93 for total ammonia nitrogen, urea, primary amines, and total nitrogen, respectively). The routine total ammonia excretion rates [22·23 & 2·0 mg N kg−1 day−1 (mean±S.E.)] of plunderfish measured in Antarctica are 10–69% lower than those of comparable non‐polar species. Plunderfish are ammonotelic, but the proportion of the total nitrogenous waste attributable to each category was variable between individuals. On average (ranges in parentheses), total ammonia nitrogen, urea, and primary amines accounted for c.82 (57–97), 13 (2–28), and 5 (0·6–22)%, respectively, of the total nitrogen excreted. Polar fish differ from their non‐polar relatives only in the rate, and not the nature, of their nitrogenous waste excretion processes.
Summer diel activity and movement of adult brown trout in high‐elevation streams in Wyoming, U.S.A.
Authors: Young M. K.
Published: April 2005

The variation in diel activity patterns was determined by implanting transmitters in adult brown trout of various sizes in two montane streams in two summers in the central Rocky Mountains, U.S.A. More brown trout tended to be active, and to move greater distances, each hour during twilight and night than during the day. Mean hourly light intensity was significantly negatively correlated with the proportion of fish active and with the distance moved. Maximum water temperature was not correlated with any measure of diel activity. Brown trout displayed fidelity to diurnal positions within a given diel cycle. Overall, fish were active an average of 11 h, had an average home range of 41 m, and moved an average of 121 m over the diel cycle. Fish length and distance moved were significantly positively correlated. Water temperature, predator avoidance, and foraging tactics may influence these patterns of diel behaviour in adult brown trout in U.S. streams.
A new method for three‐dimensional otolith analysis
Authors: Hamrin S. F. , Arneri E. , Doering‐Arjes P. , Mosegaard H. , Patwardhan A. , Sasov A. , Schatz M. , Dyck D. Van , Wickström H. , Van Heel M.
Published: April 2005

The three‐dimensional (3‐D) shape and density distribution of a cod otolith was determined using a newly developed micro X‐ray tomograph. The technique requires no special treatment of the otolith and could yield the entire 3‐D growth history in a single analysis. 999 The Fisheries Society of the British Isles
The effect of stress on reproduction in Atlantic cod
Authors: Morgan M. J. , Wilson C. E. , Crim L. W.
Published: April 2005

This study imposed stress upon spawning cod Gadus morhua in the laboratory to evaluate the potential effects of trawl avoidance on their reproductive physiology and spawning behaviour. Plasma cortisol levels of stressed fish were significantly higher than controls. Stressed cod initiated fewer courtships and often performed an altered courtship sequence. Both control and stressed fish spawned and there was little difference in the production of eggs, fertilization rate, hatching success or time to starvation of larvae. However, stressed fish produced abnormal larvae more frequently. Cod exposed to a chronic stressor are able to spawn successfully, but there appears to be a negative impact of this stress on their reproductive output, particularly through the production of abnormal larvae.
Temporal variation in male traits, nesting aggregations and mating success in the peacock blenny
Authors: Oliveira R. F. , Almada V. C. , Forsgren E. , Gonçalves E. J.
Published: April 2005

At the beginning of the breeding season male Salaria pavo that have eggs in their nests are larger, have more developed anal glands and less intense eye‐spots and are located in breeding aggregations. These differences cease to occur from the peak of the breeding season (June—July) onwards. Two scenarios are presented that may explain these results: (1) smaller and younger males may begin to breed later devoting part of the warm season to growth; (2) females may cease to be selective as the nesting space begins to be saturated with eggs. These results raise one methodological and one conceptual question. The search for correlates of male reproductive success must cover different phases of the breeding season to capture the overall dynamics of the processes involved. The operational sex ratio for cavity‐spawning fishes should take into account the availability of spawning sites rather than just counting the sexually mature members of each sex.
Nucleolar variations during the ontogenesis of diploid and tetraploid cyprinid species
Authors: Arkhipchuk V. V.
Published: April 2005

Studying the quantitative characteristics of nucleoli in cells of several cyprinid species (Cyprinus carpio, Carassius auratus gibelio, Carassius auratus auratus, Aristichthys nobilis, Ctenopharyngodon idella, Hypophthalmichthys molitrix) has shown a definite programme that controls genetically changes in the nucleolar characteristics during fish ontogenesis. In embryogenesis, the nucleolar activity, which has been estimated from the number and size of nucleoli, decreased; this process was realized dissimilarly in diploid and tetraploid cells. A correlation between the nucleolar characteristics and the body mass of juvenile fish was found. Parameters of the nucleolar activity were closely related to the physiological state of mature organisms and featured tissue specificity, rhythmicity, and high level of heritability.
Reproductive success and the energetic cost of parental care in male smallmouth bass
Authors: Gillooly J. F. , Baylis J. R.
Published: April 2005

Direct field measurements of the energetic expenditure on parental care and within‐nest reproductive success of individual male smallmouth bassMicropterus dolomieuiwere determined by measuring the change in total body mass as well as by total body electroconductivity analysis (TOBEC™). With TOBEC, the change in total body lean mass of the same live individual was measured non‐destructively at the beginning and end of the parental care period. Lean mass was the primary source of energy utilized during parental care indicating starvation and potential loss of future reproduction. Individual loss in lean mass was related positively to reproductive success suggesting that the energy expended during parental care does affect individual fitness.
A study of the histology of the digestive tract of the Nile tilapia
Authors: Morrison C. M. , Wright J. R.
Published: April 2005

The digestive tract of Oreochromis niloticus is described, in order to resolve discrepancies found between previous accounts. Two types of goblet cells were found in the oesophagus, which differed in size, and in staining characteristics with periodic acid‐Schiff and alcian blue. A region with tubular glands consisting of large mucous cells was continuous from the entry of the oesophagus, across the anterior part of the stomach to the pyloric valve, essentially providing a bypass circumventing the sac‐like portion of the stomach. This region, which is lined with striated muscle, may be a means of disposing of unwanted material, either by regurgitating it, or by passing it rapidly along to the intestine. Large mucus cells in the tubular glands and the neck cells of the gastric glands probably protect the mucosa from the very acid contents of the stomach. An ileorectal valve was present. There is therefore a separate intestine and rectum in O. niloticus, as in most teleosts.
Healing of abdominal incisions in sea lamprey larvae: a comparison of three wound‐closure techniques
Authors: Lowartz S. M. , Holmberg D. L. , Ferguson H. W. , Beamish F. W. H.
Published: April 2005

Sea lamprey larvae Petromyzon marinus were incised full thickness through their abdominal wall and the wounds closed with one of three closure techniques: cyanoacrylate adhesive (glue), a simple interrupted (SI) suture pattern, and an interrupted horizontal mattress (HM) pattern. Postoperative mortality was 13% for the glued animals and 7% for both sutured groups. No significant differences were found between groups with respect to occurrence of abdominal eviscerations, adhesions, granulation tissue or intact epithelium. The HM pattern reduced significantly the occurrence of abdominal hernia formation compared to the glued animals. Gross inflammation was found to decrease from 100% at day five to 20% at 2 weeks in both suture groups, but decreased only from 80 to 60% for glued animals through the course of the study. Some sutures remained intact in the HM group at 2 weeks, yet no sutures remained in the SI group. No glue was present on any of the wounds treated with tissue adhesive at any collection period. Tissue apposition was achieved best with the HM pattern and this may improve the animal's chance for normal, long‐term survival.
Elemental composition of otoliths from Atlantic croaker along an estuarine pollution gradient
Authors: Hanson P. J. , Zdanowicz V. S.
Published: April 2005

Elemental compositions of otoliths of young‐of‐the‐year Atlantic croaker Micropogonias undulatus at stations along a pollution gradient in Galveston Bay, Texas, were compared with those of sediments and livers to establish the level of consonance between otolith and habitat chemistries. Both coupled and uncoupled trends were indicated, with the bulk of the results pointing to the need for additional research to test the working hypothesis that the otolith stores a temporal record of elemental chemistry of resident waters. Lack of simple correlations between elemental concentrations in sediment or liver and in otoliths indicate that other biological and geochemical factors influence otolith composition.
Characterization of morphology and physiological actions of scale osteoclasts in the rainbow trout
Authors: Persson P. , Björnsson B. Th. , Takagi Y.
Published: April 2005

The morphology of scale osteoclasts in rainbow trout Oncorhynchus mykiss was characterized by light and scanning electron microscopy, and the effects of oestradiol‐17β‐treatment and sexual maturation on scale osteoclast morphology were investigated. The cells associated with resorption cavities could be distinguished morphologically as two types: symmetrical, compact cells lacking or having only a few cell processes, termed type 1 cells, and asymmetrical cells covered with folds and having several cell processes, termed type 2 cells. In adult sexually maturing fish, where scale resorption was high, type 1 cells were predominant. In juveniles and spawned adults where scale resorption was assumed to be relatively low, mostly type 2 cells were present. Oestradiol 17‐β‐treatment of juvenile rainbow trout increased the osteoclast activity, but did not affect the osteoclast morphology. Using light microscopy, the majority of the cells observed in, and closely associated with, the resorption cavities were mononucleated in both maturing and spawned fish. Occasionally, bi‐ and multinucleated osteoclasts were observed in the maturing, but not in the spawned fish. Light microscopic enzyme‐histochemistry showed that the majority of the mononucleated cells, as well as the bi‐ and multinucleated ones, were tartrate resistant acid phosphatase positive in both groups of fish, thus implying that both type 1 and type 2 cells were osteoclasts. It is thus apparent that scale resorption in rainbow trout is carried out by two morphologically distinct osteoclast populations, representing different stages of osteoclast activity and/or different stages of osteoclast differentiation.
Prespawning sound production in mediterranean sand‐gobies
Authors: Lugli M. , Torricelli P.
Published: April 2005

The emission of breeding vocalizations among sand‐gobies Pomatoschistus marmoratus, P. canestrini and Knipowitschia panizzae are described. The sounds of these gobies are pulse trains emitted by the male during mating interactions in the nest (prespawning sounds).
In vitro oocyte maturation in the sea bass: effects of hCG, pituitary extract and steroids
Authors: Sorbera L. A. , Asturiano J. F. , Carrillo M. , Cerda J. , Kime D. E. , Zanuy S.
Published: April 2005

Exposure of sea bass Dicentrarchus labrax oocytes to 25, 50, 100, and 300 IU ml−1 of human chorionic gonadotropin (hCG) resulted in a dose‐dependent increase (ED50=60 IU ml−1) in the maximal maturation and volume response rate over a 120‐h incubation period. Oocytes responded in a similar dose‐dependent manner to graded doses of homologous sea bass pituitary extract (ED50=3·3#10−2 PE ml−1). The response latency of sea bass oocytes to endogenous and exogenous gonadotropins was similar (t1/2≃45 and 48 h, respectively). Both 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20βP) and 17α,20β,21‐trihydroxy‐4‐pregnen‐3‐one (20βS) stimulated maturation in a dose‐ and time‐dependent manner with t1/2 values less than those of hCG (15 h and 7·5 h at 100 ng ml−1, respectively); 17α,20α‐dehydroxy‐4‐pregnen‐3‐one (17,20αP) was ineffective. 17,20βP was more potent at all doses tested. The stimulatory actions of gonadotropin and maturation‐inducing steroid (MIS) involved both transcription and translation since maturation was significantly inhibited in the presence of actinomycin D and cycloheximide. Moreover, pituitary extract and hCG stimulated release of higher levels of 17,20βP in a dose‐ and time‐dependent manner in follicle incubations as compared to 20βS suggesting that this steroid may in fact be the MIS in this species.
Intercohort competition causes spatial segregation in brown trout in artificial streams
Authors: Vehanen T. , Mäki‐Petäys A. , Aspi J. , Muotka T.
Published: April 2005

When together in a flume, 13‐cmLs(age‐1) trout appeared to increase their activity and behaved more aggressively, whereas 10‐cmLs(age‐0) trout tended to move less and were rarely aggressive in the presence of the larger size class. Both size classes were less mobile and preferred lower water velocities in winter than in summer, and increased their use of instream cover in winter. When both size classes were present, only small trout decreased their use of low water velocities and cover. The results indicate that intercohort competition may cause spatial segregation among size groups of brown trout, especially in winter when trout attempt to minimize their maintenance costs.
Food of introduced mosquitofish: ontogenetic diet shift and prey selection
Authors: García‐Berthou E.
Published: April 2005

The mosquitofish Gambusia holbrooki of Lake Banyoles, Catalonia, Spain, were strictly littoral. Their population was dominated by females throughout the year, except in spring when males were more common. Their diet was based on littoral cladocerans, particularly Chydorus sphaericus, Scapholeberis ramneri, Ceriodaphnia reticulata, and Pleuroxus laevis, and nematoceran (basically chironomid) adults. There was a large variety of prey of terrestrial (collembolans, ants) or aquatic neustonic origin (S. ramneri, emerging nematoceran adults), showing the microhabitat of mosquitofish closely linked to the water surface. In contrast to other studies, terrestrial insects were not especially important in summer. In addition to seasonal and between‐site variation, there was an ontogenetic diet shift from microcrustaceans, particularly cladocerans (smallest fish also using diatoms and copepod nauplii) to larger prey, namely nematoceran adults. However, there was an unusual, inverse relationship between fish length and the size of two prey (S. ramneri and the collembolan Sminthurides sp.), paralleling the overall increase in mean prey size.
A releaser pheromone that attracts males in the urine of mature female masu salmon
Authors: Yambem H. , Shindo M. , Yamazaki F.
Published: April 2005

A releaser pheromone of masu salmon Oncorhynchus masou was investigated using Y‐maze behavioural experiments. During the reproductive season, urine of mature females contains a releaser pheromone which acts as a sex attractant for spermiating mature male parr. The releaser pheromone in mature female urine is one or more low molecular weight substances (less than 10 000) soluble in ether under basic conditions. The attractant was not present in either the coelomic fluid of ovulated females nor in neutral or acidic extracts of female urine which contain free steroids and F‐type prostaglandins, respectively.
A preliminary investigation of spawning migrations of grayling in a small stream as determined by radio‐tracking
Authors: Parkinson D. , Philippart J.‐C. , Baras E.
Published: April 2005

Adult grayling Thymallus thymallus migrated from 230 to 4980 m up the Aisne stream, Belgium, to spawn between 18 and 29 March, under decreasing floods, increasing temperature and low turbidity. Males (n=4) arrived on spawning grounds several days earlier than females (n=2), stayed there longer (10–19 v. 2–3 days), and occupied a single ground each, whereas females moved between several places. After spawning, all grayling homed precisely into the pool‐riffle sequences where they were tagged in late February, and remained here until late June. These observations indicate that resident grayling are far less mobile than autumn‐spawning salmonids, and that the environmental factors triggering spawning migrations resemble more closely those of spring‐spawning cyprinids than of other salmonids. The implications of these restricted mobility patterns are discussed within the scope of population structure, and impact of river management.
Development of new VNTR markers for pike and assessment of variability at di‐ and tetranucleotide repeat microsatellite loci
Authors: Hansen M. M. , Taggart J. B. , Meldrup D.
Published: April 2005

Levels of variation at six VNTR (variable number of tandem repeats) loci, one minisatellite and five microsatellite loci, isolated from tri‐ and tetranucleotide enriched DNA libraries for northern pike were generally low in two Danish populations (1–4 alleles; expected heterozygosity 0–0·57), though one highly variable microsatellite (13 alleles; expected heterozygosity 0·79) was identified. In combination with previously published microsatellites a set consisting of nine polymorphic loci appeared to be useful for discriminating populations, as determined by assignment tests.
Upper thermal limits for feeding and growth of 0+ Arctic charr
Authors: Thyrel M. , Berglund I. , Larsson S. , Näslund I.
Published: April 2005

When Arctic charr Salvelinus alpinus from two diVerent stocks were fed live Neomysis integer, the upper thermal limits for feeding and growth were established in the range 21·5–21·8° C. These critical temperatures might have been underestimates, because fish tend to show increased sensitivity to handling at high experimental temperatures. In the second experiment, the proportion of feeding undisturbed charr from four stocks decreased initially as temperature was raised in steps from 18 to 22° C. At the lower temperatures, 18 and 20) C, almost all fish resumed feeding, but the recovery time was longer and more fish ceased to feed at 20) C than at 18° C. When the temperature was increased to 21° C, 50% of the fish ceased feeding permanently, and all fish ceased feeding within 2 days at 22° C. It is concluded that 0+ charr cease to feed and grow at c.21·5) C and that the critical temperatures for feeding and growth coincide.
Development in Salmo trutta at different temperatures, with a quantitative scoring method for intraspecific comparisons
Authors: Killeen J. , McLay H. A. , Johnston I. A.
Published: April 2005

The period from fertilization to the end of yolk resorption in the brown trout Salmo trutta was described as a series of 40 successive steps, each describing the maturation of multiple characters during an interval of development. An associated quantitative scoring system was devised, whereby individual embryos were assigned points ranging from 1 to 1000, on the basis of the assessment of a wide range of developmental features. Developmental score increased linearly with embryonic age at all temperatures studied (2, 6 and 10° C), indicating that the relative durations of successive intervals of development were maintained. At lower temperatures, the beginning of heartbeat, trunk muscle contractions, bile production, pectoral fin movements and hatching were all delayed relative to the rest of development. Therefore these features have been excluded from the scoring system. Maternal migratory type did not affect early developmental patterns.
On the rehabilitation of the clariid catfish genus Bathyclarias endemic to the East African Rift Lake Malawi
Authors: Anseaume L. , Teugels G. G.
Published: April 2005

A morphological and osteological study on a large number of specimens, together with zoogeographical data, indicate that the genus Bathyclarias, previously synonymized with the genus Dinotopterus, is a valid genus. It is rehabilitated in this paper. Bathyclarias is endemic to Lake Malawi, while Dinotopterus is confined to Lake Tanganyika.
Spermatozoa in triploids of the rosy bitterling Rhodeus ocellatus ocellatus
Authors: Kawamura K. , Ueda T. , Aoki K. , Hosoya K.
Published: April 2005

Artificially induced triploid male Rhodeus ocellatus ocellatus showed typical nuptial colorations, irrespective of spermiation. In milt from triploids, abnormal spermatozoa (malformation of the head and mitochondrion, excessive formation of the head, mitochondrion and flagellum, and no flagellum) occurred at 78°4% frequency. Spermatozoa with multiflagella were most common, often with a saccate‐like organ. Many triploid spermatozoa moved actively as long as those of diploids (10·92±0·91 min=mean±S.D., P>0·05), but did not advance like diploids, spinning around until movement ceased. The sperm density in triploids was < 2% of that from diploids. In triploid testes, deformed and variously sized spermatids were often observed, and normal spermatids and spermatozoa were seldom recognized. The DNA content of triploid spermatozoa varied greatly, compared with that of diploids. Peak of sperm DNA content differed slightly between two triploid samples with two peaks at 1·5 n and 1·9 n (P<0·0001 in both), respectively. Triploids had the greatest average sperm head diameter of 2·25±0·67 μm (mean±S.D.), while that of diploids was 1·83±0·15 μm (P=0·002). In the fertilization test using the eggs of diploids (n=1500, 30 trials), only one egg developed. The embryo chromosome number was 60 (2·5 n) and the ploidy of spermatozoa contributing to fertilization appears to be 1·5 n. The extremely low fertility of triploid R. o. ocellatus spermatozoa seems to be caused by the reduced motility and large head size of spermatozoa, and the low sperm density of the milt. The ploidy of spermatozoa that are successful in fertilization is likely to be related to the distribution pattern in the DNA content of cells.
Reduced growth of Atlantic cod in non‐lethal hypoxic conditions
Authors: CHABOT D. , DUTIL J.‐D.
Published: April 2005

Growth in length and mass, improvements in condition, as well as final condition of c. 700 g Atlantic cod Gadus morhua were significantly less at 45% and 56% O2 saturation than at 65%, 75%, 84% and 93% O2 saturation. Hypoxia decreased food consumption. In turn, food consumption explained 97% of the variation in growth. Conversion efficiency varied slightly, but significantly, with level of dissolved O2, except that the group reared at 93% O2 had a lower than expected conversion efficiency. Slow growth in low O2 was not due to increased activity, because activity decreased in hypoxia. In the Gulf of St Lawrence, waters deeper than 200 m usually are <65% saturated in O2, and thus should impact negatively on cod growth.
Morphological evidence for the occurrence of two electric catfish (Malapterurus) species in the White Nile and Omo–Turkana systems (East Africa)
Authors: Golubtsov A. S. , Berendzen P. B.
Published: April 2005

Morphological analysis of 28 Malapterurus specimens collected from the Nile and Omo–Turkana basins revealed two groups. The first was characterized by low vertebral counts (41–44) and numerous gill rakers (14–22) situated along the entire first ceratobranchial, the second group was characterized by high vertebral counts (47–51) and a low number of gill rakers (6–13) situated only on the upper portion of the first ceratobranchial. Through comparison with the type specimens of three currently recognized Malapterurus species and comparison with museum collections from the Nile, Omo–Turkana, and Chad basins, these two groups were identified as M. electricus and M. minjiriya. A principal component analysis of 27 measurements allowed partial discrimination among species. Biogeographic aspects of finding M. minjiriya in the tributaries of the White Nile and in the middle reaches of the Omo River are discussed.
Return migration of Atlantic salmon in the River Tana: the role of environmental factors
Authors: Erkinaro J. , ØKland F. , Moen K. , Niemelä E. , Rahiala M.
Published: April 2005

Multi‐sea‐winter Atlantic salmon (75–115 cm fork length LF, 2–4‐winter fish) were radio‐tagged in the Tanafjord (700 N), Norway, in 1992–1993, and 130 fish entered the large subarctic River Tana (Teno). They entered the fresh water at any time of the tidal cycle but more so during the high and ebbing tides. No diel rhythm was detected in river entry under polar day conditions. There were no differences in the change of flow between days when salmon moved and when they did not, but during active migration increasing discharge was associated with increased swimming activity of salmon, especially later in the summer. Increasing air temperature was also associated with enhanced migration activity. Low river flow was associated with increasing delay in salmon passing the first riffle area of the river, 35 km from the sea.
Anguillicola crassus (Nematoda, Dracunculoidea); first documented record of this swimbladder parasite of eels in Ireland
Authors: Evans D. W. , Matthews M. A.
Published: April 2005

In summer 1998 European eels infected with the swimbladder nematode Anguillicola crassus were detected in the Erne catchment, Ireland, probably introduced recently through the commercial eel trade.
Feasible mechanisms for algal digestion in the king angelfish
Authors: Martínez‐Díaz S. F. , Pérez‐España H.
Published: April 2005

To determine the ability of the king angelfishHolacanthus passerto digest algae, three algal species were immersed in acidic conditions similar to that found in the stomach of fish. Only one of them was not susceptible to acidic lysis; two were affected after 40 and 60 min at pH 2·0. King angelfish have an expanded region of the intestine called here the hindgut chamber (HC) containing populations of micro‐organisms. Some of these micro‐organisms have the capacity to grow in cellulose, agar, and alginic acid; the main components of algal cell walls. Micro‐organisms grew in carboxymethylcellulose cultures under aerobic and micro‐aerobic conditions. The HC is highly vascularized, which could increase absorptive efficiency of material digested in it.
Genetic variation and taxonomic analysis of the subgenus Profundulus
Authors: Doadrio I. , Carmona J. A. , Martínez E. , De Sostoa A.
Published: April 2005

The current taxonomy within the subgenus Profundulus was reviewed and at least five different species were recognized on the basis of unique genetic characters. Two of them are considered to be new species not yet described: one is known only from a single spring in the Tehuantepec basin (Mexico); the second extends mainly through springs in the Mixteca region of Mexico. The maximum Nei distances were found between P. oaxacae and the rest of the species belonging to this subgenus. Compared with the other Profundulus species, the new species from Mixteca also had high Nei values, which suggest separation of these species probably during the Miocene period. Therefore, the previously postulated old Central American origin of Profundulus is supported by our data. The mountain uplift that gave rise to the current division of Pacific and Atlantic rivers may be the reason for the current distribution pattern of the subgenus Profundulus. The sporadic presence of this subgenus in the headwaters of some Atlantic rivers has been interpreted as the result of fluvial captures during the Pleistocene period.
Seasonal differences in routine oxygen consumption rates of the bonnethead shark
Authors: Carlson J. K. , Parsons G. R.
Published: April 2005

Routine oxygen consumption rates of bonnethead sharks, Sphyrna tiburo, increased from 141·3±29·7 mg O2 kg−1 h−1 during autumn to 218·6±64·2 mg O2 kg−1 h−1 during spring, and 329·7±38·3 mg O2 kg−1 h−1 during summer. The rate of routine oxygen consumption increased over the entire seasonal temperature range (20–30° C) at a Q10=2·34.
Variation in structure and distribution of pre‐spawning Pacific herring shoals in two regions of British Columbia
Authors: Mackinson S.
Published: April 2005

In two regions of British Columbia, small and medium‐sized shoals of pre‐spawning Pacific herring Clupea harengus pallasi were most numerous and occurred as neighbours more frequently than would be expected by chance. Herring displayed a typical diurnal vertical migration, although shoals in the Central Coast were more evenly distributed through the water column during the day than those in the Strait of Georgia. As maturation progressed, shoals were found in shallower water, more densely packed and vertically extended in shape. In the Strait of Georgia, shoals were considerably larger, and positioned relatively deeper in the water column. Very large (>5000 t) shoals were found at specific locations characterized by high water exchange. Large shoals may act as an anti‐predator strategy to the abundant sealions and birds. Moreover, staying deep in the water column, and associating with dips in the sea bed, reduces predation risk and confers energy savings through hydrodynamic advantage. Smaller, denser, vertically extended, travelling shoals, prevalent during the later stages of gonad maturation, were similar in nature to labile spherical shoals observed in the Central Coast at different locations each day. Both these shoal types may benefit from synchrony and co‐ordination when evading predators that is not possible for larger shoals. The more highly clustered distribution of shoals in the Central Coast is presumed to be linked to their tight association with rock outcroppings typical of this region.
Male mate preference and size‐assortative pairing in the convict cichlid
Authors: Beeching S. C. , Hopp A. B.
Published: April 2005

Male convict cichlids Cichlasoma nigrofasciatum presented three females simultaneously were found to prefer larger females, even if a female's size exceeded their own. This indicates that some mechanism other than male choice, such as female choice or intrasexual competition, must contribute to male‐larger assortative pairing in convict cichlids. Despite a preference for larger females, males continued to consort with smaller females when available, and a females attractiveness was a function of her size relative to other females.
Behavioural and heart rate responses to food limitation and predation risk: an experimental study on rainbow trout
Authors: Höjesjö J. , Johnsson J. I. , Axelsson M.
Published: April 2005

Food‐restricted rainbow trout Oncorhynchus mykiss maintained a lower basal heart rate than satiated fish, probably as a result of reduced metabolic rate. Food‐restricted fish were also more active during feeding and were more willing to take risks than satiated fish. Both satiated and food‐restricted fish were positioned lower in the tank after the predator attack. Heart rate increased more during feeding in the food‐restricted fish compared to the satiated, but energy status had no general effect on the relation between heart rate and behaviour. Hence, the increase in heart rate was mainly a response to the more active foraging behaviour in the food‐restricted fish. Moreover, behavioural activity in the food‐restricted fish was associated with a higher heart rate after the predator attack than when the fish was undisturbed, which may reflect physiological preparation for flight. These findings suggest that behavioural and cardiac responses are coadapted to meet variation in food availability and predation risk in the wild.
Influence of water temperature on demand‐feeding rhythms in sea bass
Authors: Aranda A. , Sánchez‐Vázquez F. J. , Madrid J. A.
Published: April 2005

Under natural environmental conditions, sea bass feeding rhythms are nocturnal in winter and diurnal during the rest of the year. Increasing water temperature from 22 to 28°C or decreasing it to 16°C had little effect on the dual feeding behaviour of sea bass. An 8:16 LD photoperiod with low temperature or 16:8 LD with high temperature also failed to change the diurnal/ nocturnal behaviour of sea bass. In conclusion, sea bass feeding rhythms did not follow passively the manipulated environmental factors simulating summer and winter conditions in the laboratory, which suggests an endogenous circannual control of the seasonal phase inversion.
Seasonal changes in fish community structure of intermittent streams in the middle reaches of the Guadiana basin, Portugal
Authors: Pires A. M. , Cowx I. G. , Coelho M. M.
Published: April 2005

Seven sites on three tributaries with intermittent flow regimes in the middle reaches of the Guadiana, i.e. Xévora, Caia and Degebe, were sampled approximately every 3 months from April 1995 to April 1997. The density and biomass of fish were greater in downstream rivers and sites. Along the Xévora River, a series of point abundance samples showed evidence of fish zonation along the river. Canonical correspondence analysis (CCA) suggested a simple relationship between the different species and their preferred habitat. The small‐sized Rutilus alburnoides and Leuciscus pyrenaicus used most or all of the habitats with some cover and flowing water. Greater concentrations of larger fish were found in downstream reaches which generally had greater depths as stream width increased: large Barbus microcephalus, B. steindachneri and B. comiza preferred such sites on the Degebe River. Droughts in seasonal Mediterranean streams such as the Guadiana River are a predictable natural disturbance. In the summer, flow ceases and some stretches of river consist of isolated pools. This results in intense aggregations of fish and possible competition for food and/or space. Although some species are well adapted to natural droughts, habitat degradation and possibly the introduction of exotic species contribute to marked variability in species composition.
Characteristics of sperm of captive seabass in relation to its fertilization potential
Authors: Fauvel C. , Savoye O. , Dreanno C. , Cosson J. , Suquet M.
Published: April 2005

Seabass Dicentrarchus labrax sperm concentration was high (up to 60 × 109 spz ml−1) but decreased significantly at the end of the reproductive season (mid‐March) in monthly sampled fish. The spermiation period may be shortened by frequent stripping. Sperm can be prediluted up to 1: 128 in non‐activating medium without loss of initial motility and motility duration. Immediately after activation by transfer to sea water, all the spermatozoa were motile for 10 s and then the number of motile cells decreased progressively but sharply to zero, so that the duration of sperm motility was very short (40 s). As a consequence, the fertility of seabass sperm decreased exponentially after 10 s following sperm activation and was zero by 1 min. The sperm requirements for optimal fertilization were c. 66 000 spermatozoa per egg. Scalingup of the experimental insemination procedure yielded better fertilization rates while conserving the individual differences due to the breeder pairs.
Development of agonistic behaviour and vocalization in croaking gouramis
Authors: Henglmüller S. M. , Ladichm F.
Published: April 2005

The development of agonistic behaviour and vocalization in the croaking gourami Trichopsis vittata was studied from hatching to sexual maturity (4 months of age). Initial interactions started when fry were 11 days old and consisted of approach and flight in a feeding context. More complex threat patterns appeared during dyadic encounters as fish grew older. Lateral display (spreading of median fins in a lateral position) first occurred during the third week, circling shortly afterwards and pectoral fin beating when fish were 7 weeks old. Rapid pectoral fin beating was first accompanied by sound emission at 8 weeks. Initially, croaking sounds were built up mainly of a series of single pulses, each one produced by one pectoral fin. Later, single pulses gave way to double pulses. Furthermore, pulse period and number of pulses increased, while the dominant frequency of croaks decreased significantly with age. After vocalization was established, frontal display, mouth biting and retreat behaviour occurred at the age of 10 weeks. Initially, young exhibited vertical bars which gave way to dots and horizontal bars at 8 weeks when fish started to vocalize. The order of appearance of behavioural patterns during ontogeny corresponds to the order of appearance in fights between adults. This is the first study demonstrating that the ontogenetic development of social signalling comprises characteristic changes in behaviour, vocalization and coloration in a teleost fish.
Feeding and growth of whitefish fed restricted and abundant rations: influences on growth heterogeneity and brain serotonergic activity
Authors: Jobling M. , Koskela J. , Winberg S.
Published: April 2005

The whitefish,Coregonus lavaretus, is a schooling species, and it was hypothesized that, when faced with feed restriction, the behaviours associated with a schooling habit would lead to there being less heterogeneity in feeding and growth than has been observed in other members of the Salmonidae. This was tested by monitoring the feeding, growth and brain serotonergic activity of whitefish subjected to different levels of feed restriction (full rations and regimes estimated to give a 25 and 50% reduction in growth rate). The feed restrictions were successful in reducing rates of feeding and growth, but these reductions were not accompanied by any marked increases in interindividual variations in either feed intake or growth rates. Consequently, the imposition of restricted feeding regimes did not result in an increase in the size variation of fish within rearing tanks. Further, the brain serotonergic activity (assessed as 5‐HIAA: 5‐HT ratio) of individual fish was not found to correlate with either their feed intake or growth rates. This suggests that any competition resulting from restricted feeding did not lead to the establishment of marked dominance‐subordination relationships. 5‐HIAA: 5‐HT ratios were, however, higher amongst fish fed the most restricted rations than in fish of the other groups. This may have been a reflection of a general nutritional stress rather than pointing to an increase in social conflict amongst the fish fed the lowest rations. When provided with abundant rations the fish that had been feed‐restricted responded by becoming hyperphagic and showing catch‐up growth, the degree of compensation being related to the severity of the previous food restriction. Taken together the results suggest that restricted feeding may be a suitable method for controlling rates of production of whitefish, without there being a high risk of a marked increase in size variation with the passage of time.
Territorial competition among wild brown trout fry: effects of ownership and body size
Authors: Johnsson J. I. , Nöbbelin F. , Bohlin T.
Published: April 2005

The effects of ownership, energy status and relative size on the ability to defend a territory were studied in dyadic contests among wild brown trout fry. A logistic regression showed that the territory owner won 85% of the contests with opponents of equal size, and that a 30% size advantage was required to balance the advantage of ownership. Energy status did not affect the ability to win territorial contests.
A reassessment of the eels of the genus Bathycongrus in the Indo‐west Pacific
Authors: Castle P. H. J. , Smith D. G.
Published: April 2005

Difficulties in identifying the species of the congrid eel genus Bathycongrus Ogilby, 1898 that frequent the upper slope in the Indo‐west Pacific arise principally because these eels possess very few distinctive external characters. The differences in body proportions between the seven species that are recognized here are not easy to evaluate because of the frequent loss and subsequent regrowth of the tail tip. There are differences in the size and number of vomerine teeth, though these are not readily quantifiable, and in the number of vertebrae. However, the combination of these two characters allows the recognition of large/small‐toothed forms and those with low‐count, mid‐count, and high‐count vertebral numbers. The solution here has been to lump together some of the 16 nominal species.

Accordingly, seven Indo‐west Pacific species are recognized in this account. Uranoconger Fowler, 1934 is synonymized with Bathycongrus. Larval characters, especially the number of myomeres, may be of some assistance in resolving the problems of species identification. A key to the species is given.
New and rare snailfish genus Paraliparis from the Weddell Sea with the description of two new species
Authors: Matallanas J.
Published: April 2005

Specimens of Paraliparis balgueriasi n. sp., P. hureaui n. sp., P. charcoti, P. incognita, P. meganchus, P. mawsoni and P. antarcticus were obtained from the Weddell Sea. Paraliparis balgueriasi n. sp. and P. hureaui n. sp. are described in detail. The endochrondral pectoral girdle of P. charcoti, described here for the first time, is the only one among the Liparidae to show five radials (1+1+1+1+1), two of which (R3 and R4) are horseshoe shaped. Paraliparis incognita and P. meganchus are new records from the Weddell Sea.