bluuebunny/crossref_metadata_2025 huggingface dataset:
Deficit of didocosahexaenoyl phospholipid in the eyes of larval sea bass fed an essential fatty acid deficient diet
Authors: Bell M. V. , Mcevoy L. A. , Navarro J. C.
Published: April 2005

Larval sea bass Dicentrarchus labrax of 27 days old were reared on Artemia enriched with Super Selco©, Tuna Orbital Oil or Yeast. The first diet is commonly used in mariculture for larval rearing, the second diet was designed to deliver an optimal docosahexaenoic acid (22: 6n‐3) to eicosapentaenoic acid (20: 5n‐3) ratio, and the third diet was deficient in docosahexaenoic acid (22: 6n‐3). The eyes of these larvae were analysed after 28 days and the molecular species of the three main phospholipid classes, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) determined. Eyes from larvae fed Artemia enriched with yeast showed large decreases in molecular species containing 22: 6n‐3 compared to those supplemented with tuna orbital oil, most notably in 16: 0/22: 6n‐3 PC which fell from 10.6 to 0.4%, in 22: 6n‐3/22: 6n‐3 and 18: 1/22: 6n‐3 PE which fell from 29.6 to 0.3% and from 10.8 to 1.1% respectively, and in 22: 6n‐3/22: 6n‐3 PS which fell from 34.3 to 1.7%. Molecular species containing all other fatty acids, and especially 20: 5n‐3, were elevated in eyes from the yeast‐supplemented fish. In larvae fed Artemia enriched with Super Selco, amounts of eye 22: 6n‐3/22: 6n‐3 phospholipid were slightly lower in all three phospholipid classes compared to eyes from the tuna orbital oil‐supplemented larvae. There was also a trend of decreased saturated fatty acid/22: 6n‐3 and monounsaturated fatty acid/22: 6n‐3 molecular species in all classes from the Super Selco‐supplemented fish, the deficits being made up with molecular species containing 20: 5n‐3 and 22: 5n‐3. These results are discussed in relation to larval viability with particular respect to visual function.
Ventilatory mechanisms and the effect of hypoxia and temperature on the embryonic lesser spotted dogfish
Authors: Thomason J. C. , Davenport J. , Le Comte E.
Published: April 2005

Small, intermediate and large‐sized embryos of the dogfish Scyliorhinus canicula utilize different ventilatory methods; small and intermediate embryos rely on body movement alone to stir either the jelly or sea water in the capsule, large embryos use conventional pharyngeal pumping to pump water through the case. The effects of environmental changes in O2 tension (0.5–100% air saturation) and temperature (6–18°C) upon ventilatory mechanisms in the developing embryo in situ were studied using non‐invasive ultrasonography. All three embryo classes increased ventilation rate with rising temperature: for small embryos, y=2.02x+3.295 (P<0.01); for intermediate embryos, y=3.51x+0.395 (P<0.01); and for large embryos, y=3.81x+9.39 (P<0.01); where y=ventilatory frequency (tail beats min−1 or pump cycles min−1) and x=temperature (°C). Q10 (6–16°C)=5.0, 2.45, and 2.08 for small, intermediate and large embryos, respectively; corresponding Q10 (8–18°C) values were 2.09, 2.62, and 2.02. It is suggested that the extreme response of small embryos to 6°C is related to a different state of development in either chemoreceptors or muscle blocks. There was no significant change in ventilatory frequency induced by chronic (2 h) hypoxia. Dogfish embryos are oxyconformers at 8°C but oxyregulators at higher temperatures. Water flow through an eggcase occupied by a large embryo was studied also. Water enters the open eggcase of a large embryo, drawn in by the buccal/opercular pump of the respiring embryo, via holes at the posterior end of the eggcase. Expired water exits holes at the anterior end of the eggcase. The mean residence time for water in the case is 50 s at 8°C, giving a transit velocity of 1.36 mm s−1.
Validation of back‐calculation formulae for cod otoliths
Authors: Smedstad O. M. , Holm J. C.
Published: April 2005

This paper tries to determine the best back‐calculation formula (BCF) for cod otoliths. The cod were tagged individually and measured regularly throughout a 3‐year period. Six different BCFs were compared: (1) Fraser–Lee with an intercept estimated from a linear regression of fish length (L) on otolith length (S), (2) Fraser—Lee with an intercept estimated from a symmetrical regression line of L on S; (3) the ‘body proportional hypothesis’ (BPH) for linear relationship; (4) the ‘scale proportional hypothesis’ (SPH) for linear relationship; (5) the BPH for non‐linear relationship; and (6) the SPH for non‐linear relationship. The ‘body proportional hypothesis’ seems to be more correct than the ‘scale proportional hypothesis’, and the non‐linear BCF seems to give the best results for cod otoliths.
Antioxidant enzyme activities in embryologic and early larval stages of turbot
Authors: Peters L. D. , Livingstone D. R.
Published: April 2005

The antioxidant enzymes superoxide dismutase (SOD; EC 1.15.1.1), catalase (EC 1.11.1.6), selenium‐dependent glutathione peroxidase (SeGPX; EC 1.11.1.9), glutathione reductase (EC 1.6.4.2) and DT‐diaphorase (EC 1.6.99.2), plus total GPX activity (sum of SeGPX and Se‐independent GPX activities), were studied in 13 500 g supernatants of embryos and 3‐day and 11‐day post‐hatch larvae of turbot Scophthalmus maximus L. SOD activity decreased progressively during development from embryos to 11‐day‐old larvae, indicative of a decreased need to detoxify superoxide anion radical (O2−). In contrast, catalase, SeGPX and glutathione reductase activities increased progressively from embryos to 11‐day‐old larvae, indicative of an increased need to metabolize hydrogen peroxide (H2O2) and organic peroxides. Consistent with the latter changes, levels of lipid peroxides (i.e. thiobarbituric acid reactive substances) increased 13‐fold from embryos to 3‐day‐old larvae, whilst total peroxidizable lipid was indicated to decrease. Increases were seen for NADPH‐dependent DT‐diaphorase (after hatching) and total GPX (between 3 and 11 days post‐hatch) activities, whilst no change was found in NADH‐dependent DT‐diaphorase activity. Overall, the results demonstrate a capacity for early life‐stages of S. maximus to detoxify reactive oxygen species (O2− and H2O2) and other pro‐oxidant compounds (organic peroxides, redox cycling chemicals). Furthermore, qualitative and quantitative antioxidant changes occur during hatching and development, possibly linked to such events as altered respiration rates (SOD changes) and tissue reorganization and development (catalase, SeGPX, lipid peroxidation).
Red coloration and male parental behaviour in the threespine stickleback
Authors: McKinnon J. S.
Published: April 2005

In an anadromous population of the threespine stickleback, male red coloration was correlated with agonistic and egg care behaviour of parental males, but not with hatching success. When one male took over a neighbour's territory, the dominant male had more intense red coloration.
Diel variation in branchial calcium uptake by the rainbow trout
Authors: Tahara D. , Mugiya Y.
Published: April 2005

Branchial Ca uptake varied dielly with a nadir at 1000 hours and two peaks at 1600 and 0400 hours in rainbow trout. This variation profile essentially reflected Ca uptake through the arterio‐arterial circulation.
The relationship between first vertebra width and body length of Atlantic salmon differs between parr and smolts
Authors: Armstrong J. D. , Stewart D. C.
Published: April 2005

The relationship between the width of the first vertebra (WV) and the fork length (LF) of Atlantic salmon differs between parr and smolts. The previous use of the first vertebra to reconstruct the diets of predators from the bone remains of ingested prey will have underestimated the size of smolts and probably also their frequency of occurrence in the diet. Using the ratio WV:LF provides potential for differentiating between intact parr, smolts and pre‐smolts in the diet.
Physiological responses to handling in the turbot
Authors: Waring C. P. , Stagg R. M. , Poxton M. G.
Published: April 2005

Turbot Scophthalmus maximus were cannulated via the afferent branchial artery and were either net‐confined in sea water or in air for 9 min to monitor the stress response of a hatchery‐reared marine flatfish. No mortality was observed. Aerial exposure appeared to mobilize plasma free fatty acids and stimulate the interrenal tissue but had no effect on circulating glucose or lactate levels. This pattern was qualitatively similar to that induced by net‐confinement in sea water, although the magnitude and duration of the changes were more marked in the turbot handled in sea water. Aerial exposure had no effect on plasma osmolality, protein, or Cl− concentrations and only a minor effect on plasma Na+ concentrations, which was in sharp contrast to the ionoregulatory disturbance noted in turbot which were net‐confined in sea water. However, plasma K+ and cortisol concentrations were similarly elevated by both handling procedures. The results from these experiments suggest that whilst similarities with the salmonid physiological stress response are apparent, the lack of a plasma glucose response may represent a fundamental difference in turbot stress physiology.
Carlin tag recoveries as an indicator of predation on salmon smolts by goosanders and red‐breasted mergansers
Authors: Feltham M. J. , MacLean J. C.
Published: April 2005

Between 1984 and 1990 a total 221 Carlin tags used to mark salmonSalmo salarsmolts in the River North Esk, NE Scotland, were recovered from the stomachs of goosandersMergus merganserand red‐breasted mergansersM. serrator. Both Carlin‐tagging and adipose‐clipping affected the predation of salmon smolts by sawbill ducks. The mean (± S.D.) sizes of tagged smolts taken by both species were similar (117 ± 3 mm) and significantly smaller than the mean sizes of smolts in the river, possibly due to a reduction in the swimming performance of small smolts bearing tags. Large adipose‐clipped smolts (±mean smolt size) were predated significantly more than unclipped smolts, but no such difference was observed for small smolts (<mean smolt size). Data suggested that some ducks cued into smolt release sites where they took a disproportionately high number of tagged smolts on or near the day of release and continued to do so for several days. Although tag recoveries are commonly used to estimate the impact of piscivores on fish stocks, our study suggests that some predators respond to the presence of tagged fish in ways that directly reflect the tagging procedure and that caution should be exercised when extrapolating conclusions based on such data to untagged fish.
Marine post‐smolt growth and age at maturity of Atlantic salmon
Authors: Friedland K. D. , Haas R. E.
Published: April 2005

The annual variation in sea‐age of maturation for a hatchery dependent stock of Atlantic salmon was compared to variation in post‐smolt growth as evidenced by circuli spacing patterns. The proportion of returns of 1‐seawinter (1 SW) and 2 SW salmon and the fraction of the smolt year class or cohort that maturated as 1 SW fish, were compared to seasonal growth indices determined from circuli spacing on the scales of smolt class survivors returning as 1 SW and 2 SW spawners. Using image processing techniques, we extracted inter‐circuli distances from scales from 2244 recaptured fish. Spacing data for the first year at sea were collected and then expressed as seasonal growth indices for the spring period, when post‐smolts first enter the ocean; the summer, when growth appears maximal; and winter, when growth appears to be at a minimum. In general, circuli spacings were wider for 1 SW than for the 2 SW returns of the same smolt cohort. The 1 SW fraction was significantly and positively correlated with late summer growth, suggesting that growth during this season is pivotal in determining the proportion of a smolt class that matures early.
Onset and development of cannibalistic behaviour in early life stages of yellowtail
Authors: Sakakura Y. , Tsukamoto K.
Published: April 2005

The onset and development of cannibalistic behaviour were observed in early life stages of yellowtail Seriola quinqueradiata. Cannibalistic behaviour was divided into four actions, i.e aim, chase, nip and ingestion. The frequency of chase was used as an index of cannibalistic behaviour because it always appeared in every sequence of cannibalism, although a sequence of cannibalistic behaviour sometimes stopped before nip or ingestion. No cannibalistic behaviour was observed during the larval phase until day 22 after hatching (when fish were 9.6mm T.L.) either in a rearing pond or in experimental tanks. The onset of cannibalistic behaviour was observed on day 23, coinciding with metamorphosis from the larval to juvenile phase, and it developed until day 39, with a tentative decrease between day 33 and day 36. This inverted peak corresponded roughly to the development of schooling behaviour after day 33, which was determined by distance to the nearest neighbour. In the rearing pond, suffocation of a cannibal by its prey, appeared from day 23. Field observation of juvenile yellowtails aggregating around floating seaweeds showed that cannibalism occurred in three out of 10 schools, in which six cannibals were found among 194 fish. Cannibalistic behaviour in early life stages of yellowtail may occur as a final phase of inter‐individual interference and may have a role for size selection of a School member.
Growth and development of a bimodal length‐frequency distribution during smolting in a wild population of white‐spotted charr in northern Japan
Authors: Yamamoto S. , Nakano S.
Published: April 2005

Smolt age and size, and individual growth during smolting were examined in a wild population of white‐spotted charr, Salvelinus leucomaenis, in a small stream in northern Japan. Smolt size (110–210 mm F.L.) differed neither between sexes nor among age cohorts of 2–7 years. Back‐calculation of riverine growth of smolts using otoliths showed a gradually increasing discrepancy in fork lengths of these age cohorts in both males and females, the faster‐growing individuals smolting at an earlier age. A mark—recapture study on individually‐identified fish revealed that the initial (spring‐summer) length‐frequency distribution of parr was unimodal, but became slightly skewed to the larger side in autumn, resulting in a bimodal distribution being evident by the following spring, with the upper modal group primarily composed of smolts. However, closer examination revealed that both male and female potential (subsequent) smolts were larger than the potential parr in the previous spring, the minimum lengths of the former being around 90–100 mm f.l. Specific growth rates of the potential smolts remained relatively high after summer through to the following spring, whereas those of the potential parr decreased after summer, despite having been similar between the two groups during the previous spring and summer. These observations revealed that the developmental triggering of smelting possibly occurs in or following the summer season.
Preliminary survey of egg envelope morphology in the Macrouridae and the possible implications of its ornamentation
Authors: Merrett N. R. , Barnes S. H.
Published: April 2005

The eggs of only 13 macrourid species have been reported hitherto, eight identified from free buoyant eggs and five from ripening oocytes. Eggs of 11 species had raised, hexagonally patterned ornamentation on the envelope, while two species bore only partial ornamentation. Ripening oocytes of a further eight species showed that, overall, the eggs of 13 species had characteristic hexagonal ornamentation and three partial ornamentation, but four were smooth. Fertilized eggs of Coryphaenoides (Coryphaenoides) rupestris were found with smooth envelopes, while ornamented eggs have been reported for this species also. Little taxonomic significance could be attached to these results. Some correlation was found between the three categories of egg envelope ornamentation and species' bathymetric distributions. A recent model of egg development in a slope dwelling trachichthyid species suggested analagous potential ecological advantage for ornamentational variation in macrourids.
Spatial and temporal variation in dissolved oxygen in natural egg pockets of chum salmon, in Kennedy Creek, Washington
Authors: Peterson N. P. , Quinn T. P.
Published: April 2005

The effects of dissolved oxygen (DO) on incubating salmonid embryos have been studied extensively in the laboratory but there is little information on levels experienced by salmon embryos in complex natural channels. We monitored 33 natural egg pockets of chum salmon Oncorhynchus keta, from shortly after spawning until emergence, and found that DO levels varied considerably among and within egg pockets over time. Egg pocket DO levels varied from 2–10 mg l−1 at the time of spawning and generally declined during incubation but the declines did not occur in all pockets and were not always steady. Much of the variability may be attributed to local channel topography. Pool tailouts had the highest and least variable DO levels whereas levels in lateral bars were generally lower and more variable. Levels in glides and riffles tended to be intermediate between those in pool tailouts and lateral bars. In spite of the variation in DO levels and habitats used by chum salmon, DO levels were not correlated with egg pocket sediment composition (per cent of the sample<1.0 or 4.0 mm diameter) or with the egg pocket's depth.
The effects of kinship on the growth of juvenile Arctic charr
Authors: Brown G. E. , Brown J. A. , Wilson W. R.
Published: April 2005

The effect of kinship on growth and growth variability was studied by rearing young‐of‐the‐year Arctic charr in full‐sibling, mixed‐sibling or non‐kin groups for 11 weeks. Both weight and length were found to be significantly greater among full‐sibling v. mixed or non‐kin groups. Also, variance in weight and length of the individuals within groups was found to be significantly lower in full‐sibling v. mixed or non‐kin groups. These data suggest that relatedness of group members has a significant effect on both the growth rate and variation in growth of juvenile Arctic charr.
Genetic polymorphism of a haemoglobin chain and adenosine deaminase in European shads: evidence for the existence of two distinct genetic entities with natural hybridization
Authors: Alexandrino P. J. , Ferrand N. , Rocha J.
Published: April 2005

The degree of genetic differentiation between European shads, Alosa alosa and A. fallax, was studied in populations from different Portuguese hydrographic basins. Using isoelectric focusing, polymorphic variation was detected in a haemoglobin (HB) chain and in adenosine deaminase (ADA). These polymorphisms are shared by the two species but show significant differences in their gene frequency distributions. Individuals with intermediate morphological characteristics were found to exhibit intermediate allele frequencies. While not completely excluding introgression, our results strongly support the existence of two distinct species that can hybridize.
Physiological mechanisms of buoyancy in eggs from brackish water cod
Authors: Thorsen A. , Kjesbu O. S. , Fyhndr H. J. , Solemdal P.
Published: April 2005

Newly fertilized eggs of brackish water (Gotland, Baltic Sea) and marine (Lofoten, Norway) cod were investigated with regard to specific gravity, wet and dry weight, water content, chorion weight, and content of protein, free amino acids (FAA), and ions. The eggs had neutral buoyancies equivalent to a salinity of 14.3% (range 11.5–16.2%) in brackish water, and 33.0% (range 31.8–34.5%) in the marine environment. A buoyancy model was developed and showed that this difference was mainly caused by differences in egg water content which was 96.6 ± 0.47% and 92.7 ± 0.45% in the brackish and marine eggs, respectively. The higher water content of the brackish eggs resulted from increased water uptake during final oocyte maturation due to higher intracellular contents of FAA, Cl – and NH4+. SDS polyacrylamide gel electrophoresis of eggs and oocytes, and measurements of egg protein content suggested that the FAA pool of both egg types originated from hydrolysis of specific yolk proteins. The main contributor seemed to be a protein with a molecular weight of 100 kDa.
Histological study of the development and sex differentiation of the gonad in the European eel
Authors: Colombo G. , Grandidr G.
Published: April 2005

The histological structure of the gonads was studied in yellow eels sampled from a coastal lagoon and from stocks reared in an aquaculture plant showing different sex ratios. Gonad development related to body size rather than to age and underwent an intermediate stage characterized by a structure of an early testis but containing oogonia and oocytes. This gonad was called the Syrski organ and the stage juvenile ambisexual. Ovaries were found in eels from 22–30 cm in length, possibly derived from undifferentiated gonads or from Syrski organs. Fully differentiated testes were found in eels >35 cm, derived from Syrski organs. These observations support the results of previous research. From elvers and in eels up to 15–16 cm in length, growth of the gonadal primordium is due to primordial germ cell migration. In eels > 15 cm multiplication of primordial cells begins. Oogonial clones were found in eels > 18 cm in length, whilespermatogonium B clones were observed in eels >30 cm in length. The dynamics of sex differentiation was different among stocks with different ultimate sex ratios: ovaries were found in shorter eels in stocks with a prevalence of females, in longer eels in stocks with a prevalence of males. This result supports the hypothesis of a metagametic (environmental) sex determination. The somatic cells in contact with germ cells and those in the interstitium appeared early during gonad development and preceded germ cell differentiation. This suggests that somatic cells are the targets of the environmental factors influencing sex differentiation.
A flat‐bed passive integrated transponder antenna array for monitoring behaviour of Atlantic salmon parr and other fish
Authors: Armstrong J. D. , Braithwaite V. A. , Rycroft P.
Published: April 2005

A system for monitoring automatically the movements of individually identified small fish in natural habitats is described. The system incorporates novel flat‐bed antennae to detect the passage of miniature passive integrated transponders.
The effect of body size on the standard metabolic rate of the lesser spotted dogfish
Authors: Sims D. W.
Published: April 2005

Standard metabolic rates were measured as the rate of oxygen consumption in 33 Scyliorhinus canicula, ranging in weight from 3–929 g. The amount of oxygen consumed per hour (Vo2) changed predictably with body size according to the relationship Vo2=0–104 W0.855, where W represents fish weight in g. On a weight specific basis, the level of standard metabolism in juvenile dogfish (5 g) was nearly double that measured in adults (500 g).
Effects of mammalian gonadotropin‐releasing hormone analogue, pimozide, and the combination on plasma gonadotropin levels in different seasons and induction of ovulation in female catfish
Authors: Tharakan B. , Joy K. P.
Published: April 2005

In the catfish Heteropneustes fossilis, 0.5μg g‐1 B.W. mGnRH‐A alone or the low dose of 0.05 μg g‐1 B.W. in combination with pimozide [a dopamine (DA)‐receptor antagonist, 5 or l0μg g‐1 B.W.], caused a preovulatory surge in plasma gonadotropin (GTH) and induced a high rate of ovulation. The ovulatory response of the catfish to the low dose of mGnRH‐A when given alone was not effective in the early (July) but was effective in the late spawning season (August). Plasma GTH response to these treatments showed seasonal variations. Pimozide administration potentiated the response to mGnRH‐A in a season‐dependent manner, being effective only in the prespawning and spawning phases. Pimozide treatment alone did not affect plasma GTH. These observations suggest that the release of GTH from the pituitary is subject to seasonal differences in the sensitivity of the GnRH system and the degree of its modulation by dopamine.
Growth rate and age at migration of Anguilla anguilla
Authors: Poole W. Russell , Reynolds J. D.
Published: April 2005

The length, age and growth rate were investigated for downstream migrating male and female eels in the unexploited Burrishoole system, western Ireland. Significant differences were found in the age and length at migration with the larger, older female eels also showing faster annual growth as early as the first year in fresh water. Female eels normally migrated at lengths from 40.5 cm, exceptionally to 92.9 cm, and male eels at lengths between 28.9 and 46′0 cm. Back‐calculation showed an irregular pattern of fast and slow annual growth. Mean annual growth increments were almost always greater for females than for males.
Evidence of thermolabile sex determination in pejerrey*
Authors: Struussmann C. A. , Moriyama S. , Hanke E. F. , Cota J. C. Calsina , Takashima F.
Published: April 2005

Temperature regimes of 17 ± 1°C and 21 ±1°C early in development of pejerrey Odontesthes bonariensis produced nearly all females, whereas at 25 ± 1°C variable, sometimes male‐biased sex‐ratios were obtained. The critical period of thermolabile sex determination seemed to occur between 25 and 50 days post‐hatch (about 11 and 21 mm s.i.) at low temperatures (17–20°C) and between 0 and 25 days (about 7 and 15 mm) at high temperatures (22–25°C). The likelihood of expression of temperature‐dependent sex determination in natural populations and the possible adaptive significance of environmental sex determination in pejerrey are discussed.
Fin abnormalities of pikeperch in coastal areas off the Finnish south coast
Authors: Wlklund T. , Bylund G.
Published: April 2005

Pikeperch Stizostedion lucioperca from two different water areas off the Finnish south coast were affected by three types of fin abnormalities: fin anomalies, acute fin erosion (fin rot) and healed fin erosion. Fin erosion occurred at high prevalences at both areas, while fin anomalies occurred mainly in the area polluted by sewage.
Growth depensation and aggression in laboratory reared coho salmon: the effect of food distribution and ration size
Authors: Ryer C. H. , Olla B. L.
Published: April 2005

Groups of recently emerged coho salmon fry Oncorhynchus kisutch were reared for 3 months on food that appeared either asynchronously at a single location (localized) or synchronously and spatially dispersed (dispersed). Groups were further subdivided into those receiving low (1%) or high (3% body weight per day) rations, with five replicate groups for each treatment combination. At low ration there was greater growth depensation, i.e. growth variation, in groups receiving localized as compared to dispersed food. At high ration there was no difference. There was no effect of food distribution upon mean fish weight, but groups receiving high rations had greater mean fish weights than groups receiving low rations. There was no overall difference in the frequency of chasing between any of the treatment combinations. However, in localized food groups, dominants defended positions close to where food entered the tank, giving them greater access than subordinates. In dispersed food groups, while dominants also defended particular areas, this did not result in greater access to food. These results demonstrate that although feeding methodology may not directly influence the frequency of aggressive interactions, feeding methods which facilitate food monopolization by dominants can accelerate the growth of these individuals at the expense of subordinates. In aquacultural applications where greater size is desirable, or otherwise selected for, this may result in the unintentional selection for increased aggressiveness.
Mitochondrial DNA cytochrome b gene variation reveals different largemouth bass genealogies
Authors: Whitmore D. H. , Craft C. M.
Published: April 2005

A mitochondrial DNA character set based on cytochrome b gene variations is described that may be used in conjunction with established nuclear gene differences to assess largemouth bass Micropterus salmoides population structure and dynamics. Alignment of known cytochrome b sequences revealed two regions where the functional constraints of the molecule appear to be sufficiently reduced to allow several amino acid substitutions. Restriction analysis was used to probe nucleotide variation within one of these evolutionary hotspots, resulting in the discovery of fixed largemouth bass subspecific cytochrome b haplotypes. Application of two molecular character sets, one founded on fixed allelic variation in nuclear genes and the other on mtDNA cytochrome b diversity, revealed that in several Texas populations, where the Florida subspecies was introduced into extant populations of northern largemouth bass, hybridization was evident. The direction of the introgression vector could be determined through the combination of both character Sets.
Environmental determination of sex in Apistogrammai (Cichlidae) and two other freshwater fishes (Teleostei)
Authors: Römer U. , Beisenherz W.
Published: April 2005

Environmental sex determination by temperature could be revealed significantly in 33 Apistogramma‐species and in Poecilia melanogaster. In some, but not all, Apistogramma‐species pH also influences the sex ratio, whereas neither temperature nor pH affect the sex ratio of Pseudocrenilabrus multicolor victoriae. The sex in offspring of A. trifasciata is determined within a sensitive period of about 30 to at least 40 days after spawning.
Sexual behaviour of immature male eastern mosquitofish: a way to measure intensity of intra‐sexual selection?
Authors: Bisazza A. , Pilastro A. , Palazzi R. , Marin G.
Published: April 2005

Immature males of eastern mosquitofish Gambusia holbrooki start to be sexually active well before their copulatory organ (gonopodium) has completely developed and before they become able to transfer sperm. Sexual activity of males, consisting of copulatory attempts tending to bypass female acceptance, is intense (one attempt per minute) and is likely to be energetically very costly. The sexual behaviour of immature males relative to their maturation stage is described and tested against two possible adaptive explanations. Sexual activity was present in males from the beginning of the development of their gonopodium and increased during the following stages of maturation. Two to three weeks before gonopodium development was completed, sexual activity of immatures was as high as that of adults. Adult males showed aggressive behaviour against a male attempting a copulation, irrespective of the maturity of the latter. Since previous studies have shown that the reproductive success in this species is negatively correlated with male size when male–male competition is low (i.e. when the sex ratio is female biased), but decreases with male size when competition is high, the hypothesis was tested that sexual activity of immature males functions as a way to predict their future reproductive success if they mature at a given size. A second hypothesis tested was that precocious sexual experience improves the efficiency of copulatory attempts. Results were more in agreement with the first hypothesis, since size at maturity of males was influenced by the sex ratio experienced during maturation and precocious experience gave very little advantage.
Limia vittata as host species for the Amazon molly: no evidence for sexual reproduction
Authors: Schlupp I. , Parzefall J. , Epplen J. T. , Schartl M.
Published: April 2005

DNA fingerprinting demonstrated no sexual reproduction of the gynogenetic Amazon molly Poecilia formosa with Limia vittata as host species, in contrast with a single report that claims to have found sexual reproduction with such matings.
Sticklebacks from Greenland
Authors: Bergersen R.
Published: April 2005

Greenland freshwater sticklebacksGasterosteus aculeatuswere low‐plated. Length distribution of 1 + and 2+ fish peaked at 33 and 46 mm, in early July. Pre‐reproductive fish including 1 + fish were infected withSchistocephalus solidus. The diet consisted of chironomid larvae and pupae. Infected individuals ate smaller prey than non‐infected ones, on one occasion where competition for food was likely to occur. Infected fish had lower stomach fullness, and the parasite compressed the stomach in heavily infected fish. The other fish species was charr, and the stickleback seemed to occupy a wide range of habitats.
Description of the digestive tract and feeding habits of the king angelfish and the Cortes angelfish
Authors: Pérez‐España H. , Abitia‐Cárdenas L. A.
Published: April 2005

Morphologically, the digestive tracts of the king angelfish Holacunthus passer and the Cortes angelfish Pomacanthus zonipectus are similar, yet the king angelfish intestine is almost 30% longer than that of the Cortes angelfish. Both pomacanthids have a small mouth with villiform teeth, a short oesophagus, a well‐defined stomach, and a terminal sac at the end of the digestive tract. The terminal sac, the acid pH in the stomach, and the long intestine may facilitate efficient use of seaweed nutrients. Stomach contents were analysed to determine diets and interspecific overlap. Seventy‐one species were found in the stomachs of the king angelfish and 53 in the stomachs of the Cortes angelfish. Because of the wide range of species in their diets, both angelfish must be regarded as omnivorous. The most frequent foods were seaweed and sponges, but for the king angelfish, crustaceans were also important. A cluster analysis was done to determine whether the diets of these fish were similar by sex, size, or season. No similarities were found. Dietary overlap is high in relation to other pomacanthids.
Predation risk and feeding patterns of crucian carp
Authors: Paszkowski C. A. , Penttinen O.‐P. , Holopainen I. J. , Tonn W. M.
Published: April 2005

As part of an experimental study of the direct and indirect effects of piscivory on prey fish, the diets of crucian carp Carassius carassius were compared across sections of a divided pond; two sections were stocked with crucian carp alone and two with crucian carp plus perch Perca fluviatilis. Analysis of crucian gut contents indicated that the composition of invertebrate prey did not differ in the presence v. absence of perch. However, crucians, particularly small individuals (<10cm) that were most vulnerable to predation, displayed a lower intake of invertebrate prey in sections with perch. Although diet composition differed between crucians caught in inshore v. offshore habitats (with habitat use being related to crucian size and the presence or absence of perch), no clear pattern existed between habitat and total food intake. Overall, the major effects of predators on the diet of crucian carp appeared to be caused by increased ecological density (resulting from confinement of small crucians inshore) and reduced activity levels, rather than simple shifts to safer habitats.
Volatile fatty acids and anaerobic fermentation in temperate piscivorous and omnivorous freshwater fish
Authors: Smith T. B. , Wahl D. H. , Mackie R. I.
Published: April 2005

Endproducts of anaerobic fermentation, volatile fatty acids (VFAs), occur in the intestines of fish but no direct comparisons exist between VFA levels in fish with differing feeding ecologies during different seasons. We measured intestinal concentrations of six types of VFA in the upper and lower intestines of two freshwater omnivores (Cyprinus carpioi and Dorosoma cepedianum), and one piscivore (Micropterus salmoides) during the spring, summer and autumn. Acetate occurred in all species, and was highest in M. salmoides. In all species, concentrations were similar between upper and lower guts and higher during the summer. All three species contained anerobic bacteria and C. carpio and D. cepedianum contained cellulolytic types. Scanning electron microscopy revealed extensive colonization and suggested microbial breakdown of digesta in M. salmoides. In radio‐tracer experiments, C. carpio dosed orally with [2–14C] acetate contained label in liver, muscle and blood tissues. Amounts of intestinal VFA did not appear to increase in species with refractile diets, and low VFA in D. cepedianum suggests fermentation plays a minimal role in the nutrition of this species. Low levels of intestinal VFA during cool seasons are consistent with the hypothesis that temperature limits fermentation in these Species.
Reproductive phenology of the Azorean rock pool blenny a fish with alternative mating tactics
Authors: Santos R. S. , Hawkins S. J. , Nash R. D. M.
Published: April 2005

Both male and female Parablennius sanguinolentus parvicornis were ready to mate by the end of May. Seventy‐five per cent of the 1‐year‐old males were mature, but only 25% of the females reached maturity at this age. In females, gonads formed an increasingly greater proportion of the total weight with age, but in males the proportion decreased. A bimodal distribution of gonadosomatic indices classes was observed in 2‐year‐old males (intermediate size), which reflected the lower opportunity that intermediate size males have to spend the ejaculates than have the younger and older males. The liver played an important role in the storage of energy before the reproductive season and reserves were utilized during the breeding season. Physical condition was at its lowest in July in both sexes, but in May, just before the breeding season began, large maturing females had significantly lower eviscerated condition than males. This could be due to females investing in oocyte development, while the priority for the males was to reserve their energy for the parental activities to come. In both males and females, older and bigger animals had lower hepatosomatic and body conditions than younger ones.
How feeding performance and energy intake change with a small increase in the body size of the three‐spined stickleback
Authors: Gill A. B. , Hartf P. J. B.
Published: April 2005

Changes in the foraging behaviour due to variation in the body size of the three‐spined sticklebackGasterosteus aculeatuswere investigated. All sizes of fish had a high probability of attacking prey whenever encountered. The probability of eating the prey increased with the size of the fish, as the larger fish had larger jaws and a greater stomach capacity. Therefore, as fish increased in size there was an increase in the probability of successful prey capture. The level of satiation did not have an effect on the prey handling time, which is contrary to other studies and is probably a result of the large prey sizes. The physical size of the prey meant that the handling times were long regardless of the motivational level of the fish. The larger fish took in more energy and at a faster rate, although the time to reach satiation was similar for all fish sizes. The advantage that large fish appear to have in successfully gaining large prey is negated by their greater metabolic requirement. The changes in feeding performance induced by small increases in body size could have important consequences for intraspecific competition, habitat Use and risk of predation.
Influence of maturity status on the annual cycles of feeding and growth in Arctic charr reared at constant temperature
Authors: Tveiten H. , Johnsen H. K. , Jobling M.
Published: April 2005

Temporal changes in feeding and growth of immature (1 +), maturing male (1 +), and mature male and female (3+) Arctic charr were studied by monitoring feed intake and growth of individually‐marked fish for over 1 year. The fish were held at a constant temperature (4°C) under conditions of liberal feed supply. Feed intake and growth remained low in the period December‐April, with only 20–60% of the fish having fed on each occasion that feed intake was monitored. Feed intake and growth increased markedly during the late spring and summer, but the increases were delayed by approximately 1–2 months in the immature fish compared with their maturing counterparts. Maturing fish decreased feeding during the late summer and by September there had been an almost complete cessation of feeding. This was reflected in changes in fish body weight and condition, both of which declined from August‐September onwards. By contrast, the immature fish peaked in weight and condition in September, and weight loss during the autumn tended to be less rapid than observed for the maturing fish. The fish appeared to reduce feeding once a‘threshold condition’ of 1–4—1–5 had been attained. It is suggested that the fish may become anorexic once there has been replenishment of the energy reserves required for overwintering and, in the case of maturing individuals, for the completion of gonadal growth and Spawning.
Growth of swimming muscles and its metabolic cost in larvae of whitefish at different temperatures
Authors: Hanel R. , J. Karjalainen  , Wieser W.
Published: April 2005

The temperature relationship of routine metabolic rate (Rr) of non‐feeding, non‐growing Coregonus lavaretus larvae between 2 and 15°C is characterized by Q10‐values ranging from l.8‐2.45. The rate of growth, based on weight determinations, of first‐feeding larvae amounted to 3.5, 7.6 and 9.4% day‐1 at 5, 10 and 12°C respectively, from which Q10‐values between 4.0 and 4.8 can be calculated. The rate of increase of muscle mass between 5 and 10°C, based on the determination of the cross‐sectional area of inner muscle fibres, resulted in a Q10‐value of 4.5. Water temperature influenced the pattern of growth of the inner muscle fibres. At hatching, after 360 day degrees, total muscle mass of larvae reared at 4 and 8°C was independent of temperature, but at 4°C the rate of mass increase owed more to hyperplasia (increase in fibre number) than to hypertrophy (increase in fibre mass), whereas at 8°C the opposite was the case. The calculation of power budgets (including the metabolic cost of growth) of first‐feeding larvae yielded net conversion efficiencies (K2) increasing with temperature from 46.3% at 5°C to 54.7% at 12°C. Comparing our data with literature data two general conclusions can be drawn. (1) In first‐feeding larvae the net, but not the gross, conversion efficiency of food energy increases with temperature. This is due to net energy input being characterized by a much higher Q10‐value than energy expenditures. (2) In embryos of freshwater fish so far investigated hyperplasia plays a greater role in the increase of fibre mass than hypertrophy at the lower temperature, whereas in embryos of marine fish hyperplasia prevails at the higher temperature. It is suggested that this discrepancy correlates with the high concentration of free amino acids in the eggs of marine species which provide an additional, easily available, source of metabolic energy absent in freshwater species.
Visual acuity and feeding in larval Premnas biaculeatus
Authors: Job S. D. , Bellwood D. R.
Published: April 2005

Ontogenetic change in the visual acuity of Premnas biaculeatus larvae was determined both behaviourally and anatomically. Visual acuity improved substantially between early feeding (day 3 post‐hatch) and the pre‐settlement (day 10 post‐hatch) larvae but, at both ages, the anatomically‐measured visual acuity was greater than that determined behaviourally. It appears that estimated anatomical visual acuity values substantially over‐estimate the functional visual acuity realized under normal conditions. The distribution of the reactive angles indicated that most frequently prey within 0 to 9° of the longitudinal larval axis elicited a feeding response at both larval ages. This suggests that stereoscopic vision is used extensively during feeding in this species. The prey capture success with rotifers ranged from 96% at 3 days post‐hatch to 100% at 10 days post‐hatch. These values differ markedly from previous studies on temperate species and highlight the well developed abilities of larval P. biaculeatus at a given
Intra‐ and interspecific life history differences in sympatric grayling and brown trout in a Norwegian reservoir
Authors: Haugen T. O. , Rygg T. A.
Published: April 2005

GraylingThymallus thymallusin Lake Aursjøen, Norway, showed a remarkably uniform growth pattern throughout life, whereas brown troutSalmo truttashowed far more variation. In addition, a narrower age‐length interval of maturation was found in grayling. The restricted life history variation in grayling is discussed and it is suggested that all grayling of Lake Aursjøen experience similar environmental conditions as juveniles, which induces low phenotypic variation. In contrast the existence of several spawning populations, adapted to as many as 28 different tributaries, may have created large life history variation in Aursjøen trout. Logistic models revealed that both age and length had significant, simultaneous effects on the maturation of both species. Furthermore, the sexes of trout differed in maturation patterns, i.e. males matured earlier and at smaller sizes than female conspecifics, but no difference was found between the sexes of grayling. In addition, larger sex‐specific growth differences were found in trout. An absence of early maturing males in grayling and their presence in trout is discussed as a possible explanation of the restricted life history variation found between sexes of grayling. Male grayling experienced a larger mortality rate than did females, whereas no such differences were found in trout. It is suggested that grayling males invest more in reproduction than do females, due primarily to large investments in breeding behaviour. The equal mortality rates found for both sexes of trout, albeit males starting to spawn earlier than females, is probably explained by a female‐selective fishing mortality.
Light intensity and schooling behaviour in larval gulf menhaden
Authors: Hlggs D. M. , Fuiman L. A.
Published: April 2005

Schooling behaviour was examined in larval gulf menhaden Brevoortia patronus under decreasing and increasing light intensities and related to movements of retinal photoreceptors and pigment. Nearest neighbour angles and nearest neighbour distances between fish were inversely related to light intensity and were independent of the direction of intensity change. Swimming speeds of individual fish were directly related to light intensity when intensity was decreased but did not increase when intensity was raised. The changes in nearest neighbour angles and distances more closely paralleled movements of retinal pigment cells than cone cell migration, suggesting that rod photoreceptors play a greater role than cones in determining the threshold light intensity for schooling. A general model is developed relating the threshold light intensity for schooling to eye diameter for a number of different species and the implications of this relationship are discussed.
The effect of pineal removal on circulating melatonin levels in Atlantic salmon parr
Authors: Porter M. J. R. , Randall C. F. , Bromage N. R.
Published: April 2005

Nocturnal melatonin levels showed a significant decrease in pinealectomized Atlantic salmon parr in comparison with intact control and sham‐operated fish.
The relationship between smolt density and fry density in salmonids
Authors: Elliott J. M.
Published: April 2005

If the Ricker stock–recruitment model describes the relationship between egg density and survivor density at different stages of the life cycle, then the relationship between smolt density and fry density is not simple. Using data from a long‐term study (1966–1990) of a sea trout populationSalmo trutta, the relationship between density of potential smolts and fry densities in late M ay/early June or late August/early September is shown to be a reflexed curve with zero origin, so that there are two smolt densities for each fry density. A linear relationship is obtained only when the exponential parameter in the Ricker model is constant for the different life Stages.