bluuebunny/crossref_metadata_2025 huggingface dataset:
First occurrence and new length record for the bigeye thresher shark in the north‐east Atlantic
Authors: Thorpe T.
Published: April 2005

The first confirmed record for the bigeye thresher shark Alopias superciliosus caught in the far north‐east Atlantic is described here. The specimen was the longest and heaviest recorded to date. Above‐average summer sea temperatures occurred in the catch area in 1995.
Postembryonic development of the cephalic region in Heterobranchus longifilis
Authors: Vandewalle P. , Gluckmann I. , Baras E. , Huriaux F. , Focant B.
Published: April 2005

At hatching, Heterobranchus longifilis does not display any primordia of the cephalic skeleton. The latter appears 12 h post–hatching and develops in three stages up to day 16. The first stage (12 h to 2 days) involves almost exclusively the development of the chondrocranium. During the second period (days 3–8), dermal elements of the splanchnocranium appear. The final stage is marked by resorption of the cartilages, progressively replaced by ossifications (days 10–16). At their appearance the elements of the splanchnocranium are fused together, as are the first neurocranial elements. Later, the splanchnocranium splits up. By the time the yolk sac is completely resorbed, the buccal and pharyngeal jaws are present, the suspensoria and hyoid bars are partially developed, and the parasphenoid partially closes the hypophyseal fenestra. These structures delimit a buccal cavity that is probably functional, i.e. capable of participating in the intake of exogenous food. Next to continue its development is principally the splanchnocranium, completing the walls of the buccal cavity. Cartilage resorption parallels the appearance of endochondral ossifications (except for the trabecular bars). Braincase closure begins to accelerate once the buccal system is complete.
Daily feeding rhythms in Atlantic salmon I: feeding and aggression in parr under ambient environmental conditions
Authors: Kadri S. , Metcalfe N. B. , Huntingford F. A. , Thorpe J. E.
Published: April 2005

Daily feeding patterns of tank‐reared Atlantic salmon Salmo salar parr under ambient conditions and their relationship with patterns of aggression were investigated during spring and autumn. A single, early afternoon feeding peak was observed during spring but no consistent pattern emerged from the autumn trial (fish did tend to feed in synchrony, even though the population's feeding pattern varied between days). Aggression was highest at first light during both spring and autumn, reducing thereafter throughout the day. Feeding and aggression were out of phase during spring, with the level of feeding increasing as aggression decreased. It is suggested that the high levels of early morning aggression are associated with re‐establishment of the social order that breaks down after a period of darkness; in the spring this may have inhibited feeding.
The effect of natural selection on estimates of genetic divergence among populations of the Atlantic salmon
Authors: Jordan W. C. , Verspoor E. , Youngson A. F.
Published: April 2005

The effect of natural selection on the mMEP‐2* locus on measures of genetic divergence among Atlantic salmon populations was investigated by examining the pattern of change in the level of genetic differentiation (FST) averaged over loci when data on the mMEP‐2* locus were either included or excluded. The level of FST among populations at various geographic scales was estimated from allele frequencies at up to four loci (sAAT‐4*, IDDH‐1*, IDHP‐3*, and mMEP‐2*). At smaller geographic scales (within river systems or limited geographic regions) levels of variance in mMEP‐2* allele frequencies were reduced relative to mean levels. At larger geographic scales (across continents or the species range) variation in mMEP‐2* allele frequencies was greater than mean levels. These results suggest an a priori hypothesis for the effect of selection on the mMEP‐2* locus which may be applied in future studies on variation in protein coding or other (e.g. mini‐ and microsatellite) loci in the Atlantic salmon. It is recommended that estimates of gene flow among populations of the Atlantic salmon based on mean FST estimates which include data on the mMEP‐2* locus should be viewed with caution.
Does cyclicity of growth rate in rainbow trout exist?
Authors: Noel O. , Le Bail P.‐Y.
Published: April 2005

Ninety rainbow trout Oncorhynchus mykiss were reared in three tanks (n= 30), and their growth rate was monitored for 25 weeks. During the experiment, fish were fed ad libitum, and kept under simulated natural photoperiod and constant temperature (14 ± 1°C). Throughout the experiment, water quality (pH, O2, N‐NH3, N‐NH4, NO2) was considered optimum. Two growth rate periods were observed on the population: first an acclimation period (weeks 1–5), followed by a period of general decrease in growth rate (weeks 5–25). This trend was modelled with a third‐order polynomial function. The autocorrelation analysis of the fluctuations revealed a cyclicity of the growth rate with a 4–5‐week period. This cyclicity was independent of the tanks and of the growth rate trend type (long‐ v. short‐term acclimation period). However, at the individual level, trends as well as short‐term fluctuations were heterogeneous and no clear cyclicity could be detected. The biological relevance of the population growth rate cyclicity and the apparent absence of similar individual fluctuations are discussed.
Comparative efficacy of clove oil and other chemicals in anaesthetization of Pomacentrus amboinensis, a coral reef fish
Authors: Munday P. L. , Wilson S. K.
Published: April 2005

The efficacy of quinaldine, benzocaine, MS‐222, 2‐phenoxyethanol and clove oil was compared for anaesthetizing settlement stage Pomacentrus amboinensis, a frequently studied coral reef fish. Induction to anaesthesia, behaviour during anaesthesia, recovery times and survival rates of fish treated with the different chemicals were compared. Clove oil was only marginally less effective than quinaldine and was more effective than other chemicals tested, except at high concentrations. In addition, fish exposed to clove oil exhibited a much calmer induction to anaesthesia than fish exposed to quinaldine. Therefore, clove oil may be an effective alternative to quinaldine as a fish anaesthetic. Recovery time after anaesthesia with clove oil was two to three times longer than recovery from other chemicals, a desirable charcteristic for use in field studies. Survival rates were excellent for all chemicals.
Assessment of structural and functional similarities and differences between caeca of the bluegill
Authors: Hossain A. M. , Dutta H. M.
Published: April 2005

Bluegill Lepomis macrochirus possess six to eight gastrointestinal caeca, >70% having seven. The terminal caeca toward abdominal edge (C6, C7) were always larger than the terminal caeca toward the vertebral column (C1, C2) and middle caeca (C3, C4, C5). The caeca varied in relative thickness of the histological layers and lumen space. The terminal caeca (C1, C2, C6, C7) have anatomical positional advantage over, and possess more contents, than the middle ones (C3, C4, C5) in both field and laboratory conditions. Hence, all caeca in bluegill may have the same function but their functional potentials are not the same. Two factors, size of caeca and anatomical position of caeca, apparently work synergistically to cause variation in their functional efficiency.
Do random fluctuations in the intervals between feeding affect growth rate in juvenile three‐spined sticklebacks?
Authors: Ali M. , Wootton R. J.
Published: April 2005

This study measured the effects of regular and irregular intervals between feeds on the growth performance of juvenile Gasterosteus aculeatus. The experimental period was 21 days at 14) C and photoperiod of 10L: 14D. The fish were housed individually. The control fish received a constant ration every day. Fish on a constant interval were fed on days 1, 5, 9, 13, 17 and 21. Fish on a random regime were fed with the same average interval between feedings, but the interval varied randomly between 1 and 5 days. The rations were calculated so that over the 21‐day period, all fish were supplied with the same total quantity of food. The two ration levels were: 2% (maintenance ration) and 6% of the initial body weight per day. At a given ration, the feeding interval had no significant effect on specific growth rate, RNA/DNA ratio and lipid contents. The percentage dry matter was slightly, but significantly lower in treatment groups than in the control group. Groups receiving a mean 2% ratio consumed all the food supplied. At a mean ration of 6%, the control group ate 100%, the regular interval group 95·4% and the irregular interval 98·3% of the total food supplied. For the temporal patterns of feeding used, the fish were able to adjust their food intake, when food become available, to compensate for short periods of food deprivation and maintain their growth performance except for a decrease in dry matter content.
Effects of mass removal and variable recruitment on nutrient excretion by a planktivorous roach stock
Authors: Horppila J.
Published: April 2005

The effects of intensive fishing and fish recruitment on the nutrient excretion rate by a planktivorous roach Rutilus rutilus stock in Lake Vesijärvi were estimated using a bioenergetics model. The values were compared with those given by the model assuming that no mass removal occurred or that the mass removal ceased after 2 years. According to the model, during June‐August 1989 phosphorus (P) excretion by the pelagic roach stock corresponded to 18% of the annual external P loading and showed a maximum of 0.4 mg m−2 day−1. As a result of mass removal, the maximum daily P excretion declined to 0.18 mg m−2 by 1990 and to 0.10 mg m−2 by 1992. The reduction was due to the lower number of roach, while the excretion rates of individual fish were unaffected. A 2‐year mass removal would have temporarily reduced the P excretion rate, but in 1991 and 1992 the highest daily excretion rates would have been doubled compared with values after the 4‐year mass removal. Assuming no fishing mortality, interannual differences were diminished and the excretion rates in 1991 and 1992 were 2.5 times higher than the values after the 4‐year mass removal. The results suggest that nutrient recycling by fish stocks may be affected substantially by fisheries management. However, the effects are dependent on the timing of fishing due to the variations in the year class strength of fish. In Lake Vesijärvi the reduction in nutrient excretion was amplified coincidentally by the natural variation in recruitment of the roach stock.
Energy allocation in larval and juvenile Coregonus lavaretus: validation of a bioenergetics model
Authors: Huuskonen H. , Karjalainen J. , Medgyesy N. , Wieser W.
Published: April 2005

Food consumption and energy allocation of larval and juvenile whitefish Coregonus lavaretus L. were studied by conducting respirometry experiments at 10, 12 and 15° C. Results from these experiments were compared with those predicted by a bioenergetics model that used observed growth as the major input. The data were used to assess the performance of the model, and evaluate its suitability for estimation of food consumption by whitefish. The mean absolute % error (ɛ) between observed and predicted food consumption was 16·3%, and the modelling efficiency (ME) was 0·90, indicating that the model was reasonably robust. Linear regression analysis of predicted v. observed food consumption values gave a slope slightly above unity, indicating a tendency for the model to overestimate consumption at higher values. ɛ and Me were also calculated for total metabolic rate (RT), and they equalled 13·0% and 0·85, respectively. Despite some deficiencies, it is concluded that the model can be used for prediction of food consumption by highly active, planktivorous fish such as whitefish.
Isolation and characterization of mRNA encoding the chicken‐II type gonadotropin‐releasing hormone (GnRH) precursor in the rainbow trout
Authors: Penlington M. C. , Harden N. , Garside J. , Hoole D. , Arme C.
Published: April 2005

The cDNA encoding the [His5Trp7Tyr8] gonadotropin‐releasing hormone (chicken‐II‐type GnRH; cGnRH‐II) precursor from rainbow trout Oncorhynchus mykiss has been sequenced using reverse transcription and rapid amplification of cDNA ends (RACE). The precursor cDNA is 544 bp from which an open reading frame of 258 bases encodes a 86 amino acid precursor. The tripartite structure of the encoded peptide is identical to all other GnRHs reported to date. The rainbow trout cGnRH‐II cDNA, including both the precursor encoding and non‐coding regions, shared 52–80% identity with others of this variant characterized in fish. When the individual components that encode the tripartite structure were compared, identity was significant across the GnRH, signal and associated peptide encoding regions. Nucleotide similarity between non‐coding regions were generally low. In trout, only the cGnRH‐II, but not the signal or associated peptide encoding region, shared significant similarity to the cGnRH‐II precursor cDNAs characterized from the tree shrew. Cladistic analysis using the bases encoding cGnRH‐II precursors resulted in their broad division into two, fish and tree shrew. The fish could be classified generally into two, the Ostariophysi (siluriforms and cypriniforms) and Acanthopterygii (perciforms) together with the Protacanthoptergyii (salmoniforms). Trout shared greatest homology with the Acanthopterygii. Northern analyses identified a single transcript that was expressed in the midbrain only.
Tropical fishes: patterns and propensities*
Authors: Pauly D.
Published: April 2005

When key biological statistics (growth parameters, mortality rates, etc.) of a large number of fish species are plotted against other variables (notably maximum size and mean habitat temperature), clear trends or patterns tend to emerge. These patterns are usually not perceived as requiring explanation, as reflected in the rarity of pertinent hypotheses in the literature, relative to the ubiquity of the patterns. A theory is presented which has the potential to explain the propensities behind many of these observed patterns. This theory, based on the author's earlier work, is built around the notion that gill area severely constrains the respiration and hence the growth of fishes (and other water‐breathing animals). The patterns generated by growth‐related processes, such as mortality, reproduction or food consumption can then also be explained. In this theory, tropical fishes are not different from other fishes, once account is taken of the fact that tropical fish are, not metaphorically but literally, in hot water.
High biomass and production but low energy transfer effciency of Caribbean parrotfish: implications for trophic models of coral reefs§
Authors: Van Rooij J. M. , Videler J. J. , Bruggemann J. H.
Published: April 2005

Quantitative data are presented to assess the trophic role of scarids on the fringing coral reef of Bonaire (Netherlands Antilles), with particular emphasis on the stoplight parrotfishSparisoma viride. Average herbivore biomass on the reef was 690 kg ha−1, 22% of which was accounted for byS. viride. From data on relative gonad weights, daily spawning frequencies, and egg numbers obtained by stripping, with previous estimates of somatic growth and energy intake, a gross effciency (GE: somatic plus gamete production/ consumption) of 2.3% was obtained. This is a factor of five to seven lower than the GE suggested to be valid for most aquatic ecosystems, including coral reefs. To investigate one potential cause for our low estimate, overestimation of food intake, our intake estimates were compared with published values for other herbivorous coral reef fish. This yielded a relationship (daily C intake=0.0342#W0.816; wet body massWin g) with high correlation (r2=94.6%,n=13), which shows that the intake estimates agree well with other published data. Averaged over the year, primary production at 0–3 m depth was 17.2 kg C ha−1day−1while herbivore consumption was estimated at 17.4 kg C ha−1day−1, indicating an ecotrophic effciency (EE, the fraction of total production at one trophic level that is consumed by all predators) of 100%. This suggests strongly that the food intake estimates are realistic, since no changes in algal biomass were observed over the study period. The two scarids for which food intake was actually measured in our own study area, were estimated to consume 55% of the algal production in the shallow reef (S. viride, 20%;Scarus vetula, 35%). This is lower than expected if consumption were proportional to biomass (S. viride, 22%;S. vetula, 40% of herbivore biomass in the shallow reef). Consequently, a minimum estimate of 88–91% can be inferred for the EE of these two species. Multiplied by GE, this yields a transfer effciency (TE, the fraction of production passing from one trophic level to the next) of 2%. For coastal and coral systems the primary production required (PPR) to sustain fisheries was estimated to be 8.3%, which was based on a TE of 10%. The present estimates show that the TE of a major herbivore at our reef is at least a factor of five lower. Assuming that the estimate is representative for all scarids (comprising 70% of the herbivore standing stock), it can be concluded that the PPR to sustain coral reef fisheries may be as high as 40% of the total primary production. The low value reported before, might suggest that the effect of fishing mainly affects target populations but not the lowest trophic levels. It is argued that our estimate is more realistic for coral reefs supporting high scarid biomass and explains better the many reports of coral destruction due to algal overgrowth at exploited reefs.
Characterization of spermatozoa and eggs of the rabbitfish
Authors: Lahnsteiner F. , Patzner R. A.
Published: April 2005

The spermatozoon of Siganus rivulatus is symmetrical in its longitudinal axis, has no acrosome, an almost spherical nucleus, a small mid‐piece with six mitochondria, centrioles arranged at an acute angle to each other, no nuclear fossa, and a flagellum without fins. Sperm motility is reversibly inhibited in the seminal plasma, and in electrolyte and non‐electrolyte solutions of 100 mosmol kg−1 and activated by an increase in osmotic pressure. The sperm motility parameters remain constant for 5 min after activation, then motility starts to decrease and stops 25–30 min after activation. Osmolalities between 600 and 1100 mosmol kg−1 and a pH between 7·5 and 9·0 do not affect the sperm motility parameters. The eggs of S. rivulatus contain several large central lipid droplets composed of neutral lipids and glycolipids. Glycogen granules and sialoglycoproteins are dispersed between the lipid droplets. The protein yolk, consisting of neutral and slightly basic proteins is located peripherally. The cortical alveoli containing neutral polysaccharids are located in the outermost regions in close vicinity to the oolemma. The chorion is two‐layered and has no specialized surface structures.
Effect of variable food levels on reproductive performance of breeding female three‐spined sticklebacks
Authors: Ali M. , Wootton R. J.
Published: April 2005

The study examined the response to variation in food ration within a breeding season on components of the reproductive performance of mature female three‐spined sticklebacksGasterosteus aculeatus, a batch spawner. The main effect of food availability was on the duration of the inter‐spawning interval (ISI). Low ration resulted in an increase in the number of days until the next spawning. A low ration during one inter‐spawning interval increased the length of the next ISI, even if there was a high ration in the latter. Females that experienced high rations for two successive ISIs showed an increase in batch fecundity over the successive spawnings. There was no tendency for fish on low rations to produce bigger eggs or eggs with higher lipid concentration. Females on low ration had a lower carcass dry matter concentration and a lower liver dry weight immediately after their third spawning. Female sticklebacks responded to a low ration with little change in egg number or size, but a slight reduction in physiological condition. Egg characteristics and, to a lesser extent, batch fecundity are insensitive to current rate of food consumption, but the interval between spawnings is sensitive to both current and previous rates of consumption.
Variation in field estimates of daily ration in young yellow perch
Authors: Grant S. M. , Kott E.
Published: April 2005

The quantity of food in the complete digestive tract of young‐of‐the‐year yellow perch Perca flavescens varied between samples taken at the same time of the day over 2–3 consecutive days, resulting in a 1·7‐ to 2·5‐fold variation of in situ estimates of daily ration. Increased food intake rates were related to increased consumption of large prey items suggesting a day‐to‐day pattern in the quantity and size of food consumed.
Age structure and diel activity of pouting on the Poole Bay artificial reef
Authors: Fowler A. J. , Jensen A. C. , Collins K. J. , Smith I. P.
Published: April 2005

Predominantly (86·6%) juvenile (<191 mm) pouting Trisopterus luscus formed inactive, nonfeeding schools around artificial reef units in Poole Bay, Dorset, during daylight hours and the position of the schools was related to differing tidal conditions. At current speeds >0·3 m s−1, the pouting congregated close to the reef units, remained low in the water column and maintained position. At current speeds <0·1 m s−1, the schools were more dispersed, further away from reef units and higher in the water column. This tidally‐related behaviour is thought to be related to energy conservation during the daylight hours, when the pouting utilize the lee of reef units during strong tidal currents. Between 15 and 30 min after dusk the majority of pouting left the artificial reef, and returned 45–60 min before dawn. A brief mark‐recapture programme, using 0‐ to 1‐group pouting, confirmed that a proportion of the pouting tagged were present on the artificial reef up to 5 days after marking, suggesting that the site was being used to some extent as a home reef. The nocturnal foraging pattern may be related to the availability of prey species.
The presence of Couch's goby in the Mediterranean Sea
Authors: Stefanni S. , Mazzoldi C.
Published: April 2005

Known distribution of Couch's goby, Gobius couchi Miller & El‐Tawil, 1974 formerly limited to the British Isles, appears now to be extended to the Mediterranean. A new specimen collected at the island of Ischia, near Naples, Italy, is described.
Molecular cloning and developmental expression of the halibut thyroid hormone receptor‐α
Authors: Llewellyn L. , Nowell M. A. , Ramsurn V. P. , Wigham T. , Sweeney G. E. , Kristjánsson B. , Halldórrson Ó.
Published: April 2005

To analyse the role of thyroid hormones in development of the halibut Hippoglossus hippoglossus, a cDNA library was constructed from mRNA isolated from metamorphosing halibut larvae and approximately 500 000 recombinants were screened using a probe derived from the thyroid hormone receptor (TR)‐α gene of the frog Xenopus laevis. A single positive clone was isolated and sequenced. It was found to contain the entire coding sequence of the halibut TR‐α gene. Expression of the TR‐α gene during halibut development was monitored using reverse‐transcriptase polymerase chain reaction, which showed that there is a several‐fold increase in the level of TR‐α expression around the time of hatching but that the level of TR‐α expression is relatively constant thereafter.
Dynamic morphology of fish larvae, structural implications of friction forces in swimming, feeding and ventilation*
Authors: Osse J.W.M. , van den Boogaart J. G. M.
Published: April 2005

Dynamic morphology is the study of the ontogenetic transformations of functional systems in growing organisms. This paper describes these processes in fish larvae as they grow into the juvenile stage. Details of form changes and growth at the level of the organism and its organs are given. Some mechanical functions, such as swimming, eating and ventilation/respiration, which are important for surviving the most vulnerable period of life, the larval period, are analysed and their demands on structures and constructions are correlated with changing forms, size dimensions and environmental factors. The size‐ and velocity‐dependent influences of viscosity, as an important physical environmental factor, are the points of emphasis. The changing form of the swimming motion, form and task of the finfold at different places along the body, modes and requirements of aquatic feeding and respiration are reflected in the changing sizes and proportions of the developing larval body.
Influence of sexual maturity on feeding, growth and energy stores of wild Atlantic salmon parr
Authors: Arndt S. K. A.
Published: April 2005

Maturing Salmo salar parr had significantly lower short‐term energy stores (indicated by hepato‐somatic index) in August, and significantly lower energy stores and growth rate (indicated by RNA : DNA) in September than immature parr captured from the same stream sites on the same date. There were no significant differences in gut fullness or protein concentrations, suggesting that up to early September the main energetic consequences of maturation were a reduction in allocations to growth and short‐term energy storage, but not a mobilization of long‐term stored energy in the form of proteins. These are the first observations of relative food intake and energy storage for maturing parr under natural conditions, and also the first to assess growth effects on wild fish before completion of the maturation process.
Histological and morphological evaluations of the digestive tract and associated organs of haddock throughout post‐hatching ontogeny
Authors: Hamlin H. J. , Von Herbing I. Hunt , Kling L. J.
Published: April 2005

At hatching, the oesophagus of haddock Melanogrammus aeglefinus lacks goblet cells, the intestine is a simple undifferentiated tube, the liver is present as a rounded mass caudal to the heart, and numerous zymogen granules are present in the pancreas. The first intestinal convolution appears at day 2, at the posterior end of the digestive tract. The oesophagus displays alcian blue and PAS positive mucus secreting cells on day 12, which become numerous by day 15. By day 18, epithelial cells of the posterior intestine show evidence of protein absorption in the form of supranuclear vacuoles. The swimbladder inflates in 50% of the larvae by day 22, although inflation rate is highly variable. By day 35, or 10 mm, a pyloric caecal ridge appears which separates the presumptive stomach, which is now showing evidence of gastric gland formation, from the intestine. This marks the beginning of digestive features characteristic of the juvenile stage.
Loaches of the genus Lepidocephalichthys, from Manipur, with description of a new species
Authors: Arunkumar L.
Published: April 2005

A new species Lepidocephalichthys manipurensis, is described, confined to the Chandel district of Manipur near the adjoining borderland areas of Manipur, India and Burma (Myanmar). It is distinguished by the following combination of characters: a sharp small black dot just above the upper base of the caudal fin; 8–9 dorsal short dark ashy brown bars from occiput to the base of the caudal fin; absence of scales on the vertex of head; caudal fin fork, pectoral, ventral and anal fins are non‐immaculate; least depth of caudal peduncle 50·00–60·24% (mean 54·09) of its length and 7·69–8·11%L, S (mean 8·22); caudal fin with 4–5 W‐shaped bands: a single dark black stripe from tip of snout to eye; 8–11 spots on the mid lateral line; and 30–31 vertebrae. A key to the identification of lepidocephalid loaches of Manipur is provided.
Morphological variation in hybrids between Salmo marmoratus, and alien Salmo species in the Volarja stream, Soca River basin, Slovenia
Authors: Delling B. , Crivelli A. J. , Rubin J‐F. , Berrebi P.
Published: April 2005

There were significant correlations between colour pattern, LDH‐5*, genotype and certain meristic characters in 59 hybrid trout Salmo, sp. from the Volarja stream, Soca River basin, Slovenia. It is concluded that panmixia between native Salmo marmoratus, and introduced S. trutta, of Atlantic, Danubian and Mediterranean origin had not been reached in this zone, despite the long period of introgression. The result is in agreement with other studies dealing with introgression in Salmo, and for management purposes certain morphological characters, especially colour pattern, can be a valuable tool in restoring the marble trout population in the Soca River.
Oxygen and acid‐base status related drives to gill ventilation in carp
Authors: Soncini R. , Glass M. L.
Published: April 2005

Gill ventilation in carp Cyprinus carpio increased 50% with a reduction of [O2]a to 60% of the control value. Small decreases of inspired PO2 also increased ventilation, which occurred without any significant changes of the blood gas picture. Ventilation increased with hypercapnia but only if [O2]a became reduced by concomitant Bohr and Root shifts. Consistently, hypercapnia failed to increase ventilation when combined with hyperoxia. Therefore, it was not possible to ascribe any ventilatory response to specific CO2/pH receptors.
Mitochondrial DNA variation in European populations of Silurus glanis
Authors: Krieg F. , Triantafyllidis A. , Guyomard R.
Published: April 2005

Mitochondrial DNA diversity of 13 wild Silurus glanis populations (covering the entire range of the species) and eight hatchery populations was investigated. PCR‐RFLP analysis of four regions of mitochondrial DNA (cytochrome b, control region, ND‐5/6) was used. Nineteen haplotypes were found. Thirteen of them were private. The proportion of total genetic diversity attributable to population differentiation was almost 80%. Despite the existence of significant differentiation between populations for mtDNA variation, no consistent pattern of geographic structuring was revealed and nucleotide divergence among S. glanis populations was low. These phenomena are discussed with regard to the impact of glaciation events. The domesticated stocks show less genetic diversity than natural ones, possibly due to their mode of management. Analysis of three European catfish species S. glanis, S. aristotelis and Silurus triostegus (sampled in the Euphrates river) revealed several endonucleases which produced restriction phenotypes diagnostic for the three species.
Unpredictability of fish recruitment: interannual variation in young–of–the–year abundance
Authors: Karjalainen J. , Auvinen H. , Helminen H. , Arjomäki T. J. , Niva T. , Sarvala J. , Vilhanen M.
Published: April 2005

In 1989–1998, vendace larvae Coregonus albula were sampled in Finnish lakes following a stratified random sampling design. The abundance of young–of–the–year vendace after the first growing season was estimated using catch–per–unit–effort statistics. The number or total area of nursery places hardly limited the recruitment of vendace in the study lakes. The major proportion of prerecruit mortality of vendace occurred in the larval phase and larval sampling produced significant information on young–of–the–year survival. Although larval abundances and recruitment were clearly associated only in Lake Onkamo, generally high larval abundance was needed to produce high number of recruits.
A modified Bläzka–type respirometer for the study of swimming metabolism in fishes having deep, laterally compressed bodies or unusual locomotor modes
Authors: Hove J. R. , Gordon M. S , Webb P. W. , Weihs D.
Published: April 2005

A low volume (8·4 l), rectangular (cross–section) respirometer modified from a Bläzka–type coaxial circuit, which provides rectilinear flow at speeds up to 0·36 m s–1, is described.
Refuge use in sticklebacks as a function of body length and group size
Authors: Krause J. , Longworth P. , Ruxton G. D.
Published: April 2005

A change in anti–predator strategy from hiding to grouping outside a refuge was observed in large three–spined sticklebacks. No such change in strategy was seen in small fish. The body–length dependence of this strategy change is discussed in the context of metabolic constraints.
Osteology and myology of the cephalic region and pectoral girdle of Plotosus lineatus, with comments on Plotosidae (Teleostei: Siluriformes) autapomorphies
Authors: Oliveria C. , Diogo R. , Vandewalle P. , Chardon M.
Published: April 2005

From comparisons of the cephalic and pectoral girdle structures of Plotosus lineatus with those of other plotosid as well as non‐plotosid siluriforms, plotosid catfishes can be defined by at least six autapomorphies. These are: (1) the absence of the ventral division of the muscle arrector dorsalis; (2) the double articulation between the neurocranium and the anterior part of the suspensorium; (3) the greatly enlarged utricular otolith, which profoundly inflates the ventral surfaces of both the prootic and the pterotic; (4) the attachment of the muscle extensor tentaculi on the neurocranium lies further anteriorly than its insertion on the autopalatine; (5) the coronoid process of the mandible is linked to the maxillary by means of two thick, long ligaments; (6) the enlarged base of the maxillary barbel.
Reproductive biology of the conger eel from the south coast of Brittany, France and comparison with the Europe eel
Authors: Sbaihi M. , Fouchereau‐Peron M. , Meunier F. , Elie P. , Mayer I. , Burzawa‐Gerard E. , Vidal B. , Dufour S.
Published: April 2005

The gonadosomatic indices (IG) of female conger eel Conger conger, aged between 2 and 11 years postmetamorphosis, ranged between 0·04 and 4·78 and were correlated with both age and body length. Microscopical examination of the gonads showed immature ovaries at two main stages of oocyte development, pre‐vitellogenic oocytes for IG < 1, and oocytes at an early vitellogenic stage (lipid vesicle stage) for IG>1. The immaturity of the conger eels sampled in Concarneau Bay indicates that this species probably spawns in deeper oceanic waters. Radioimmunoassays (RIA) of sex steroids gave low serum levels of oestradiol and of 11‐ketotestosterone, but higher levels of testosterone correlated with increase in IG. Immunoenzymatic assay (ELISA) indicated low serum levels of vitellogenin (VtG), which were significantly correlated with IG. The pre‐vitellogenic and early vitellogenic stages observed in the coastal C. conger were similar to the oocyte stages found in the European eel Anguilla anguilla, at the yellow and silver phases of its life cycle respectively. However, other morpho‐functional changes, associated with silvering in Anguilla species, such as the increase in ocular index, and regression of the digestive tract, did not occur at the early vitellogenic stage in conger eels.
Ability of predatory native Australian fishes to learn to avoid toxic larvae of the introduced toad Bufo marinus
Authors: Crossland M. R.
Published: April 2005

Of two native Australian fishes naïve to the introduced toad Bufo marinus most barramundi Lates calcarifer rapidly learned to avoid B. marinus tadpoles, while sooty grunter Hephaestus fuliginosus exhibited considerable intraspecific variation in their learning ability. Some sooty grunter learned to avoid tadpoles after only a few attacks, while other individuals continued to attack and reject tadpoles throughout the entire laboratory trials. Individuals of both species recognized and avoided tadpoles 1 day after their previous encounter. None of the fishes died during the trials. The observed variation in behavioural responses of fishes to B. marinus may be due to differences in (1) learning ability, (2) fish hunger levels, and or (3) tadpole palatability and toxicity. The results demonstrate that most barramundi and sooty grunter learn to avoid B. marinus tadpoles with minimal trauma. Consequently, it is anticipated that the toads are unlikely to have a significant negative impact on wild populations of these fishes through direct toxic effects.
Dietary fructose does not specifically induce hepatic glucokinase expression in rainbow trout
Authors: Panserat S. , Capilla E. , Gutierrez J. , Vachot C. , Plagnes‐Juan E. , Aguirre P. , Brèque J. , Kaushik S.
Published: April 2005

Glucokinase (GK) catalyses the first step of hepatic glycolysis to store the excess dietary glucose. After rainbow trout Oncorhynchus mykiss were fed a single meal with dietary glucose and fructose, there was induction of GK expression, although no specific effect of dietary fructose was observed. This suggested that dietary fructose is not essential to improve dietary glucose Utilization.
The effects of light intensity and algae‐induced turbidity on feeding behaviour of larval striped trumpeter
Authors: Cobcroft J. M. , Pankhurst P. M. , Hart P. R. , Battalene S. C.
Published: April 2005

Striped trumpeter larvae reared in algal cell‐induced turbid water (greenwater) fed equally well in clearwater in a light intensity range of 1–10 μmol s‐1 m‐2, when evaluated in terms of both the proportion of larvae feeding and larval feeding intensity. An ontogenetic improvement in photopic visual sensitivity of larvae was indicated by improved feeding at 0·1 μmol s‐1 m‐2, from 26±5% of larvae feeding and 0·027±0·005 rotifers consumed per feeding larva min‐1 on day 8, to 96±2% and 0·221±0·007 rotifers consumed larva‐1 min‐1 on day 23 post‐hatching. Algal cell‐induced turbidity was shown to reduce incident irradiance with depth, indicated by increasing coefficients of attenuation (1·4–33·1) with increasing cell densities (0–2×106 cells ml‐1), though light intensities in the feeding experiment test chambers, at the algal cell densities tested, were within the optimal range for feeding (1–10 μmol s‐1 m‐2). Algae‐induced turbidity had different effects on larval feeding response dependent upon the previous visual environment of the larvae. Young larvae (day 9 post‐hatching) reared in clearwater showed decreased feeding capabilities with increasing turbidity, from 98±1% feeding and 0·153±0·022 rotifers consumed larva‐1 min‐1 in clearwater to 61±10% feeding and 0·042±0·004 rotifers consumed larva‐1 min‐1 at 56 NTU, while older clearwater reared larvae fed well at all turbidities tested. Likewise, greenwater reared larvae had increased feeding capabilities in the highest algal cell densities tested (32 and 66 NTU) compared with those in low algal cell density (6 NTU), and clearwater (0·7 NTU) to which they were naïve.
REGULAR PAPERS Habitat distribution and size structure in freshwater fish communities: effects of vendace on interactions between perch and roach
Authors: BEIER U.
Published: April 2005

In a study of habitat selection and size structure in three fish species in 115 Swedish lakes, roach Rutilus rutilus used the pelagic habitat to a lesser extent and were lower in pelagic biomass in the presence of vendace Coregonus albula. Size distributions of roach were skewed toward larger sizes in lakes with vendace, although a similar pattern of size‐dependent habitat use was found regardless of lake group. In disagreement with predictions, vendace did not affect relative perch Perca fluviatilis biomass, size structure, or the proportion of large perch. However, a higher growth for large perch indicated higher per capita energy intake in lakes with vendace.
Differences in susceptibility to sea lice infection between a sea run and a freshwater resident population of brown trout
Authors: Glover K. A. , Nilsen F. , Skaala Ø. , Taggart J. B. , Teale A. J.
Published: April 2005

Two experimental groups comprising mixed Norwegian sea run and freshwater resident brown trout Salmo trutta were infected with sea lice Lepeophtheirus salmonis in replicate tanks. Comparison of mean abundance and louse development between the sea run and resident groups revealed highly significant differences in lice abundance. The resident trout had an average abundance ± of 6·3±0·37 and 6·6±0·43 lice whilst the sea trout had an average abundance of 3·5 ±0·25 and 3·3 ±0·28 lice 29 days post infection at 9° C. No differences in development of lice, of either sex, were detected between the groups. As host groups were naive to sea lice at the start of the experiment, this suggests that there was a significant difference in susceptibility to sea lice infection between them, which may be genetically determined.
Microhabitat segregation in three rocky intertidal fish species in Portugal: does it reflect interspecific competition?
Authors: Faria C. , Almada V.
Published: April 2005

Recruits of Lipophrys pholis, Coryphoblennius galerita and Gobius cobitis spend the low tide under water in pools, and in the case of G. cobitis also in channels. The pools used by the two blenniids show greater similarity than those used by G. cobitis. Larger juveniles and adults of C. galerita continue to use the same type of pools, which are temporarily abandoned by the males during the breeding season when they use emersed holes and crevices as nests. The much faster growing L. pholis and G. cobitis leave the pools in their first autumn, when they are c. 7 cm long. Whereas G. cobitis >7 cm move to channels and large upper pools, with a smooth substratum, sand and boulders, L. pholis begin to use emersed crevices where they spend low tide often in large groups. When L. pholis or C. galerita were added or removed selectively from pools, their numbers returned to pre‐experimental levels after 2 weeks, suggesting that, although intraspecific competition may be strong, interspecific competition was unlikely to explain these results fully.
Influence of habitat on grouper abundance in the Florida Keys, U.S.A.
Authors: Sluka R. D. , Chiappone M. , Sealey K. M. Sullivan
Published: April 2005

There was a significant inshore to offshore pattern in grouper species composition and density on Florida Keys coral reefs. Red grouper Epinephelus morio and black grouper Mycteroperca bonaci were most abundant on inshore patch reefs. Graysby Cephalopholis cruentata was most abundant on offshore reef types. Density among sites ranged from 0 to 0·43, 0 to 0·26 and 0 to 1·23 100 m−2 for red grouper, black grouper, and graysby, respectively. Grouper density exhibited no consistency among sites within similar reef types. The densities of red and black grouper were correlated significantly with either physical or biotic habitat parameters. Graysby were observed in microhabitats with whose benthic features differed significantly from the surrounding habitat. This species was observed in high‐relief areas with significantly less octocoral species and colony densities. Larger graysby were observed in areas of higher relief and less octocorals than smaller graysby. Habitat was one of several important factors influencing the distribution of groupers among coral reefs types in the Florida Keys.
The influence of growth rate on the size of migrating female eels in Lake Ellesmere, New Zealand
Authors: Jellyman D. J.
Published: April 2005

Lake Ellesmere, a large coastal lake in the South Island of New Zealand, supports an important commercial eel fishery, based mainly on migrating (silver) male Anguilla australis. Lengths of silver female eels from samples collected in 1942, 1974–1982 and 1998–1999 showed an initial decline between 1942 and 1974 but an increase from 1979 onwards. Back‐calculated growth rates of 50 female silver eels caught in 1998 showed that most (90%) exhibited a period of accelerated linear growth commencing at lengths between 380 and 660 mm (mean 598 mm); this accelerated growth coincided with a change in diet to piscivory. The onset of maturity was more closely associated with length than age, condition, or growth rate. The increase in average length of female silver eels of 250 mm over the past 20 years is consistent with the hypothesis that female eels adopt a size‐maximizing growth strategy to ensure maximum fecundity; this is the first time this hypothesis has been demonstrated from temporal changes within a single population.
Regional variation and the effect of lake: river area on sex distribution of American eels
Authors: Oliveira K. , McCleave J.D. , Wippelhauser† G. S.
Published: April 2005

Silver phase American eels, Anguilla rostrata, were collected while migrating from five rivers in Maine, U.S.A. Sex ratios varied from 49 to 98% male for these rivers and had a range of 46% over a 30 km distance between the mouths of three rivers. The proportion of male eels was inversely related to the amount of lacustrine habitat in the five drainage areas (r=−0·95, P=0·014). A combination of these sex ratios and published data from two Nova Scotia rivers showed large variation in the proportion of male eels within 1° of latitude. Thus, the hypothesis from the literature that the distribution of the sexes is dependent upon distance of larval transport was not supported. Eels migrating from lacustrine habitats within a river were predominately female, while eels migrating from fluvial habitats were predominately male, regardless of upstream distance. Apparently river habitat influences the distribution of the sexes and may play a role in sex determination.
Genetic markers for identification of Patagonian toothfish and Antarctic toothfish
Authors: Smith P. J. , Gaffney P. M. , Purves M.
Published: April 2005

Fillet samples of the toothfish Dissostichus eleginoides and D. mawsoni can be distinguished readily by muscle proteins revealed by isoelectric focusing and mitochondrial DNA markers. The proteins also distinguish toothfish from other species marketed under similar trade names.
Genetic introgression between wild and stocked brown trout in the Douro River basin, Spain
Authors: Almodóvar A. , Suárez J. , Nicola G. G. , Nuevo M.
Published: April 2005

The genetic diversity of Spanish brown trout is currently threatened by stocking with exogenous brown trout from Central and Northern Europe. In the Douro River basin 25% of the analysed populations in the present study showed introgression by genes of hatchery origin. The mean introgression estimated by the single locus approach (S) varied from 0 to 22% among populations, with a mean value of 3%. The hatchery allele markers were absent in populations where stocking ceased in 1993. However, the introgression effect was observed in all populations stocked until 1998. It seems that cessation of stocking is a good measure for restoring native populations. A thorough review of published and present data of genetic interactions between wild and stocked brown trout in Spanish rivers indicates different levels of introgression between basins. The absence of a clear geographical pattern in the introgression level suggests that ecological interactions and local stocking programmes may play an important role in stocking success. Finally, several guidelines are provided for conservation and management of native brown trout populations in Spanish rivers.
Creating and destroying species: the ‘new’ biodiversity and evolutionarily significant units among New Zealand's galaxiid fishes
Authors: Ling N. , Gleeson D. M. , Willis K. J. , Binzegger S. U.
Published: April 2005

Morphological and genetic analyses of populations of two non‐diadromous galaxiid species, the black mudfish and Neochanna heleios, the dwarf inanga Galaxias gracilis confirm the presence of a cryptic species, Neochanna heleios, within the geographic range of N. diversus, and indicate three distinct evolutionarily significant units (ESUs) in the latter species. Comparisons between G. gracilis and its parent taxon, G. maculatus, reveal that the former is not monophyletic and derives from three separate founding events. Significant morphological divergence between these two species is the result of ontogenic shifts in landlocked lacustrine populations and long‐term morphological convergence in populations of G. gracilis.. Corresponding incipient changes are recognized in other younger landlocked populations of G. maculatus in New Zealand. These populations and the three groups within G. gracilis should be given the status of ESUs and managed accordingly by conservation agencies.