bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of body size and temperature on oxygen consumption of the European eel, Anguilla anguilla
Authors: Degani G. , Gallagher M. L. , Meltzer A.
Published: January 2006

The effect of temperature and body size on oxygen uptake of European eels, Anguilla anguilla, was studied. The mass specific oxygen uptake of large eels was lower at all temperatures than that of small eels. The effect of temperature on metabolism was greater on small eels than on large eels. The relationship between oxygen consumption and body size is described by the equation M = a Wb, where M is metabolism (O2h‐1), W is body weight (g), b is the slope of the function which describes the relationship between body weight change and metabolism, and a is the temperature‐dependent constant of the equation. In this study it was found that increased temperature caused an increase in a and a decrease in b.
A comparative study of the skin and gill structure in oviparous and viviparous freshwater fish larvae
Authors: Foscarini R.
Published: January 2006

Comparative scanning electron microscope studies have been performed on the skin of two oviparous and two viviparous freshwater fish embryos and larvae in order to investigate eventual morphological differences. In the early larval stages, temporary microvilli‐like structures (MVLS) were detected in oviparous fish larvae which were later replaced by raicroridge formations. In viviparous fish larvae, only‘fingerprint‐like’pattern microridge formations were observed. Light microscope slides showed that the disappearance of these MVLS were found to be chronologically related with the development of functional gill lamellae and yolk sac resorption.
Observations on siting, dimensions and structure of salmonid redds
Authors: Crisp D. T. , Carling P. A.
Published: January 2006

Redds of trout, Salmo trutta L., Atlantic salmon, S. salar L., and rainbow trout, S. gairdneri Richardson, were studied at sites in north‐east England, south‐west Wales and southern England (Dorset). Spawning females preferred gravels of 20–30 mm diameter and water velocities at 0·6 depth of 15 cm s‐1 and <c. 2·0 body lengths s‐1. After logarithmic transformation the major horizontal dimensions of redds could be related to one another by linear regressions, and redd tail length could, similarly, be related to female fish length. Egg burial depth in upland stony streams in north‐east England and south‐west Wales could be predicted from a linear regression of mean depth upon female length. Information is also given on gravel composition and redd structure.
Host‐constrained epidemiology of the fish tapeworm Ligula intestinalis (L.)
Authors: Wyatt R. J. , Kennedy C. R.
Published: January 2006

Investigations into the biology of the roach, Rutilus rutilus (L.), and Ligula intestinalis (L.) populations at Slapton Ley, Devon were carried out between October 1982 and December 1984, and additional data collected from the lake since 1977 have been re‐analysed. The Ligula population exhibited some unusual features: a limited specificity, a persistently low abundance and a scarcity of multiple infections. The population dynamics of the roach were also unusual in that the individual growth rate was one of the fastest in Britain, the survival was very poor and the year classes tended to alternate in strength. Whether the unusual epidemiology of Ligula could be explained by the unusual population dynamics of the roach is investigated.

The transmission period of Ligula to the roach was limited to their first few months of life, probably due to a limited period of feeding on copepods by the fry. This narrow transmission window was almost certainly the major factor that has prevented the abundance of Ligula plerocercoids attaining high levels in the fry or of increasing in subsequent years, and has resulted in their abundance being determined entirely by transmission events to the fry. The limited transmission period has also caused the life‐cycles of the roach and Ligula populations to become synchronized. At other localities, the abundance of Ligula is typically high, and can have a significant effect on the mortality of the host population, but, with the low abundance at Slapton, Ligula‐induced roach mortality was insignificant. The rapid growth of the roach fry was the most likely explanation for the limited period of feeding on copepods, and the large size, short life‐span and low abundance of the roach probably also constrained the build‐up of the Ligula population in the lake. The random frequency distribution and scarcity of multiple infections was not considered unusual in view of the very low plerocercoid abundance. The very low abundance of Ligula, the separation of the spawning of roach and rudd in time and space, and the scarcity of rudd may account for the absence of infection in this species. It was concluded that the Ligula population in Slapton Ley was being constrained by the atypical population dynamics of the roach, and not vice versa as theory predicts.
Hybrids of Abramis brama with Scardinius erythrophthalmus and Rutilus rutilus from Lake Volvi, Macedonia, Greece
Authors: Economidis P. S. , Wheeler Alwyne
Published: January 2006

Two specimens of the hybrid Abramis brama×Scardinius erythrophthalmus and a single specimen of the hybrid A. brama×Rutilus rutilus are reported and described from Lake Volvi, Macedonia, Greece. This is the first occurrence of either hybrid in Greek fresh waters.
Seasonal changes in the intestinal mucosa of winter flounder, Pseudopleuronectes americanus (Walbaum), from Passamaquoddy Bay, New Brunswick
Authors: McLeese J. M. , Moon T. W.
Published: January 2006

Winter flounder from Passamaquoddy Bay, N.B. undergo an annual fast from November to May which results in a decrease in the slope of the length‐weight relationship (3·17 to 2·54), in the condition factor (9 to 12%), in the liver (75%) and white muscle (24%) lipid contents, and an increase in muscle water content (2·4%). Winter flounder appear to have sufficient lipid reserves to support the winter fast, as muscle water content declined only at the onset of feeding.

The intestine could be divided into pyloric caeca (4), foregut, midgut and hindgut. Mucosal folding was reduced in all sections of the intestine during the fast. Goblet cell number declined, but little change in enterocyte ultrastructure was observed. Intestinal length remained the same, although the caeca shortened. Overall, mucosal mass declined by 57% from May to January, while surface area declined by 50%. This value is less than that in literature reports for a fast of shorter duration in freshwater rainbow trout. We propose that the continued need for salt and water transport for osmoregulation maintains the proximodistal gradient of mass and surface area and ameliorates the effect of starvation on mucosal mass and area.
Effects of different photoperiods on the reproduction of the barbel, Barbus barbus (L.), reared at constant temperature
Authors: Poncin P.
Published: January 2006

The role of photoperiod as an environmental factor controlling reproduction, particularly the duration and ending of the breeding season, in the barbel was investigated by tank experiments. The experiments used a population of barbel matured in captivity which were stripped of eggs at frequent intervals: 10–15 'spawnings’for each female were obtained at 15‐day intervals.

A decreasing photoperiod (16·5 light: 7·5 dark→8L: 16D), for an annual cycle contracted to 6 months duration, inhibited the spawning of both female and male fish. This allowed two periods of reproduction (February‐May and September‐November) within one year. Under natural or constant (10L: 14D) photoperiod conditions, spawning came to an end spontaneously. The rate (accelerated, slow or natural) of daylength increase did not affect the onset of spawning.
Genetic differences between populations of sardine, Sardina pilchardus, and anchovy, Engraulis encrasicolus, in the Aegean and Ionian seas
Authors: Spanakis E. , Tsimenides N. , Zouros E.
Published: January 2006

Genetic distances based on electrophoretic variation and multivariate analysis of several morpho‐metric and meristic characters suggest that populations of sardine and anchovy from the Aegean and Ionian seas do not form one panmictic population. The distinction between these two classes of populations emerges only as a statistical property, and for some characters the within‐sea variation is larger than the between‐sea variation. Thus, the reproductive isolation between populations inhabiting the two seas appears to be only partial. Our findings do not support the‘ pure‘ or‘ discrete‘ stock concept. Instead, they provide evidence for the dynamic population structure model according to which physical (e.g., hydrographic) or biological (e.g., predation or behaviour) factors impose a population structure maintained in a semi‐equilibrium state under the opposing influences of migration and selection. Such a dynamic state may not be stable in the long run, and it may not allow for the accumulation of genetic divergence necessary for the emergence of higher taxa. It must, nevertheless, be taken into account in the management of exploited natural populations.
Toxicity versus avoidance response of golden shiner, Notemigonus crysoleucas, to five metals
Authors: Hartwell S. I. , Jin J. H. , Cherry D. S. , Cairns J.
Published: January 2006

Avoidance thresholds and 96‐h LC50 values were determined for golden shiners, Noiemigonus crysoleucas, for five individual elements: chromium, Cr; copper, Cu; cadmium, Cd; arsenic, As; selenium, Se. The avoidance concentrations were 73, 26 and 28 μgl‐1 for Cr‐VI, Cu and As‐III, respectively. Cadmium and Se were not avoided at experimental concentrations up to 68 and 3489 μg1‐1, respectively. Acute flow‐through 96‐h LC50 values were Cr‐VI 55·0, Cu 84·6, and As‐III 12·5 mg 1‐1, which were more than two orders of magnitude above avoidance concentrations. The acute flow‐through 96‐h LC50 values for Cd and Se were 2·8 and 11·2 mg 1‐1, respectively. These concentrations are 31 and 2·2 times the highest concentration employed in the avoidance tests, neither of which were avoided by the test organisms. Thus, simple toxicity tests do not identify the environmental hazard of some elements, and the most toxic elements may not elicit a behavioural response. When used in concert with tests of organism function, more realistic indicators of environmental hazard or safety may be determined.
Testis‐testicular gland complex of two Tripterygion species (Blennioidei, Teleostei): differences between territorial and non‐territorial males
Authors: de Jonge J. , de Ruiter A. J. H. , van den Hurk R.
Published: January 2006

The morphological differences between the testis and testicular gland of territorial and nonterritorial males of Tripterygion tripteronotus and T. delaisi were examined and correlated with differences in reproductive behaviour. In territorial males of both species the testicular gland is much more developed than in non‐territorial males. Larger cellular and nuclear sizes in the territorial males indicate that the activity of the gland cells is enhanced. These cells contain SER, numerous lipid droplets and mitochondria with lamellar cristae. Absence of 3β‐HSD activity at these sites points to lack of a steroidogenic potency. In both territorial and non‐territorial fish, steroid‐producing Leydig cells have been demonstrated in the connective tissue betweeen the testis and the testicular gland, and around the collecting sperm duct. In addition, 3β‐HSD activity has been found in the scarce interstitial Leydig cells of territorial fish. Morphometric data indicate an enhanced activity of the Leydig cells in territorial fish.
Sound production by the river bullhead, Cottus gobio L. (Cottidae, Teleostei)
Authors: Ladich F.
Published: January 2006

Acoustic signals of Cottus gobio consist of knocking sounds produced as single pulses (48 ms) or as trains of 4–6 pulses (230 ms). Frequencies extend up to 3 kHz, but most sound energy is concentrated between 50 and 500 Hz in both sound types. Cottus gobio is solitary, maintains territories, and defends them by threat display, seldom by biting and fighting. Threatening consists of spreading gill covers and fins, darkening, and sound production. Calling is accompanied by a nodding movement of the head, during which the pectoral girdle and the skull are moved rapidly against each other. No difference in ability of sound production was observed between sexes, but males emitted significantly more sounds than females. In the laboratory an increase in vocalization activity was observed between night and day. An increase in the number of encounters and calls was noted when temperatures were raised from 8°C to 13°C. Sound production was registered throughout the year.
The influence of dietary and waterborne zinc on heat‐stable metal ligands in rainbow trout, Salmo gairdneri Richardson: quantification by 109Cd radioassay and evaluation of the assay
Authors: Spry D. J. , Wood C. M.
Published: January 2006

The 109Cd binding assay of Eaton & Toal was critically evaluated and then used to assess the induction of cytosolic metal‐binding ligands in rainbow trout exposed to Zn in the diet and/or in the water for 16 weeks. With purified rabbit Cd‐Zn metallothionein (MT), 109Cd binding and total Cd recovery in the assay were linear up to 5 μg of protein; gel chromatography revealed a single peak. With heat‐denatured extracts of gill, liver and intestine from control and Cd‐ and Zn‐injected trout, 109Cd binding was generally linear with sample size. Gel chromatography demonstrated that 109Cd was bound by a protein with the same apparent weight as MT (∼ 11000 daltons), but significant binding occurred also at three other regions [molecular weight (mol wt) >70 000, 30000 and <3000]. In the dietary/waterborne Zn exposure, induced 109Cd‐binding activity occurred not in the MT peak but in the low mol wt peak (< 3000). Activity in the gill rose in response to both dietary and waterborne Zn, but the liver did not respond. The maximum five‐fold elevation in the gill was primarily a waterborne effect. In the intestine, the maximum rise was 25‐fold due to both factors. The thresholds for induction were > 39 μg Zn| in water, and > 90 mg kg | in the diet, but only when waterborne Zn was also high. There was no correlation between 109Cd binding and acid soluble thiol levels, which tended to decline at higher Zn exposures.
Some aspects of the biology of the garfish Belone belone (L.) from southern Ireland
Authors: Dorman J. A.
Published: January 2006

An account is given of certain aspects of the biology of the garfish, Belone belone, captured by sea anglers from Courtmacsherry Bay, Co. Cork. Fish were aged by otoliths, and found to grow most rapidly in their first 2 years, females attaining a greater mean size than males. Most of the fish caught had already spawned. From examination of their gonads and lengths of juveniles collected in the neuston, spawning would appear to take place there mostly in the month of June.
Observations on the colours of lumpsuckers, Cyclopterus lumpus L.
Authors: Davenport J. , Thorsteinsson V.
Published: January 2006

Ripe unfertilized eggs derived from fish landed at two Icelandic ports were predominantly red and yellow‐red, but a small proportion were red‐purple. There was a significant difference between the frequencies of hues of eggs from the two landing places. During the phase of blastula formation, fertilized red‐purple eggs showed no discernible change in either hue or chroma. However, as the gastrula formed and covered the yolk, the chroma declined dramatically, although the hue remained unaltered. When the embryo formed, the chroma continued to decrease and the hue also began to change as the red‐purple pigment disappeared from the yolk and the orange‐yellow oil of the yolk became more visible.

The most common plasma colouration in male fish collected at Hafnarfjordur and Husavik was red, but the observed hues covered 60% of the visible spectrum, ranging from green to purple. No significant differences between Hafnarfjordur and Husavik males in terms of hue or value were discerned, but there was a significant difference in chroma score. Female plasma hues were almost as variable as the males (spanning 45% of the visible spectrum) but centred in the green‐yellow zone. Plasma, subcutaneous jelly and skin colours were closely linked.

Fish from the oceanic feeding grounds were all green in skin colour, whatever their age or sex; it is suggested that this colouration has a cryptic function in the near surface waters inhabited by lumpsuckers.
Larval competition for food between wild and hatchery‐reared ayu, Plecoglossm altivelis Temminck et Schlegel, in culture ponds
Authors: Uchida K. , Tsukamoto K. , Ishii S. , Ishida R. , Kajihara T.
Published: January 2006

To examine the larval competition between wild and hatchery ayu in the culture ponds, mixed rearing of 580 000 wild and 520 000 hatchery larvae was carried out in two 25‐m3 ponds for 3 months, in contrast to the control in which 860 000 wild larvae were reared in another pond.

The number of wild larvae in the mixed‐rearing treatments decreased rapidly 20 days after the start of mixed rearing, in contrast to hatchery larvae. Mortality of wild larvae was almost 100% at the end of the experiment (3 months), while the hatchery larvae showed the usual survival rate of 15–16%. In the control pond, however, 16% of the wild larvae survived. The wild larvae grew much slower (0.10mmday ‐1) than the hatchery larvae (0·26 mm day ‐1) in the mixed‐rearing ponds, whereas the wild larvae in the control pond showed almost the same growth rate (0·24 mm day ‐1) as hatchery larvae. On day 6 the gut fullness of wild larvae was only 30% of that of the hatchery larvae in the mixed‐rearing experiments. On day 46 the wild larvae occurred deeper in the mixed‐rearing ponds than the hatchery larvae. This depth difference in vertical distribution appeared to cause a disadvantage for the wild larvae in the competition with hatchery larvae, since the food was supplied at the surface. Thus, the wild larvae starved and died.
A review of genetic variation in Atlantic salmon, Salmo salar L., and its importance for stock identification, enhancement programmes and aquaculture
Authors: Davidson W. S. , Birt T. P. , Green J. M.
Published: January 2006

The increasing exploitation of Atlantic salmon as a food source and sport fish demands a better understanding of salmon genetics and the dynamics of Atlantic salmon populations. Surveys of salmon populations for protein electrophoretic variation reveal that the average heterozygosity in Salmo salar is low and that four gene loci account for more than 95% of the total electrophoretically detectable variation. Populations that have been studied by this means fall into one of three groups: Western Atlantic, Eastern Atlantic or Baltic. However, biochemical genetics involving starch gel electrophoresis cannot be used routinely to identify the continent of origin of an Atlantic salmon, let alone its native river. The mitochondrial genome can be used to identify North American or European salmon with the aid of restriction endonucleases that have six base pair recognition sites. Restriction endonucleases that recognize four base pairs appear to be able to identify salmon from a particular river system. There has been a move from protein variation to mitochondrial DNA variation and this will inevitably lead to more extensive studies on the nuclear genome. Chromosomal studies suggest differences between salmon from Europe and North America but these have been hampered by lack of good banding procedures. Preliminary studies using cloned segments of salmonid genomes suggest that repeated sequences such as the genes for ribosomal RNA will be most useful for identifying specific stocks of Atlantic salmon. The need for continued genetic studies on the Atlantic salmon and the relevance and importance of the results of this research for stock identification, enhancement programmes, aquaculture and basic science are discussed.
A morphometric study of the effects of tributyltin compounds on the gills of the mummichog, Fundulus heteroclitus
Authors: Pinkney A. E. , Wright D. A. , Hughes G. M.
Published: January 2006

The effects of tributyltin (TBT) compounds on gill morphology were examined in the mummichog, Fundulus heteroclitus, in 96‐h LC50 and 6‐week sublethal exposures. Morphometry was used for the identification and quantification of effects with the light microscope. A 96‐h LC50 of 17.2 μg 1 1 was determined. Morphometric analysis of gill tissues revealed hypertrophy of the lamellar epithelium in fish exposed to 17.2 μg 1–1. Relative diffusing capacity was significantly decreased (−41 %); (P<0.05, ANOVA, Bonferroni t‐test). At 35.6 μg 1−1, TBT exposure resulted in a significant reduction (− 40%) in the volume of the lamellar blood channels. Both of these observations occurred in fish that showed signs of acute poisoning including loss of equilibrium. In fish exposed to sublethal concentrations of 0.105–2.000 μg TBT 1−1 for 6 weeks, there were no pathological changes in the gill. There were no treatment‐related changes in the surface morphology of the gills of fish from both experiments upon scanning electron microscopic examination. Although gill pathology was observed in acutely toxic exposures, it does not appear to be a major mechanism of TBT toxicity.
Seasonal colour changes and shifting antipredator tactics in darters
Authors: Radabaugh D. C.
Published: January 2006

Dull coloured, non‐breeding males of the darter Etheostoma flabellare‘freeze’ in response to simulated predatory threat. As they enter breeding condition, colour changes are minor and antipredator behaviour does not change. Male E. blennioides, which develop bright green colours in the breeding season, also freeze in response to threats in both breeding and non‐breeding states. Male E. spectabile change colours dramatically when breeding, developing intense and contrasting orange, blue, yellow and red colours on their sides, fins and throats. In non‐breeding colouration, they freeze when threatened, but in breeding colouration they become less likely to freeze and more likely to flee. These results are discussed both with respect to the hypothesis that changing colours may require changing antipredator behaviour, and in terms of the probable degree of crypticity of these species. Details of the duration of immobility of ‘freezing’ fish and the pattern of subsequent recovery of activity level are also presented.
Differences in the sensitivity of brown trout, Salmo trutta L., and rainbow trout, Salmo gairdneri Richardson, to physiological doses of cortisol
Authors: Pickering A. D. , Pottinger T. G. , Carragher J. F.
Published: January 2006

Interspecific differences in the stress response of fish may be due, in part, to differences in the sensitivity of target tissues to cortisol. The relative response of brown and rainbow trout to a standardized dose of cortisol was assessed by monitoring condition (K factor), the number of circulating lymphocytes and mortality due to disease, following cortisol treatment. Cortisol implantation resulted in a significant decline in K factor and number of circulating lymphocytes in immature brown trout, but not in immature rainbow trout, despite plasma cortisol levels being similar in both cases. Cortisol implantation in mature brown and rainbow trout significantly increased the mortality rate due to bacterial and fungal infection compared with control fish. Furthermore, the mortality rate due to disease was significantly greater in brown trout than rainbow trout, despite both groups receiving similar doses of steroid.
Correlates of male reproductive success in Padogobius martensi (Gobiidae)
Authors: Marconato A. , Bisazza A. , Marin G.
Published: January 2006

Factors affecting male reproductive success were investigated in a natural population of Padogobius martensi, a small freshwater goby showing paternal care. Males were found to be polygynous and their mating success was related both to their body length and to the size of the nest occupied. Body size was a good predictor for the presence of eggs in the nest. The number of egg batches guarded by a male was highly correlated with the area of his nest. Mature males with a total length of 48 mm or less (1‐year‐old individuals) occupied nest sites in breeding areas but were never found with eggs in their nests. The components of sexual selection which may determine the variance in mating success are discussed.
Effects of feeding regime on food consumption, growth rates and tissue nucleic acids in juvenile Arctic charr, Salvelinm alpinus, with particular respect to compensatory growth
Authors: Mlglavs I. , Jobling M.
Published: January 2006

Juvenile Arctic charr responded to a change from restricted to satiation feeding by showing a growth spurt (compensatory growth). During this period of rapid growth the fish became hyper‐phagic and in the days immediately following transfer from restricted to satiation feeding showed improved food conversion efficiency compared to their counterparts raised on a liberal feeding regime. Tissue (liver and muscle) nucleic acid concentrations were influenced by feeding regime, and RNA : DNA ratios were low in both starved fish and those fed restricted rations. Following transfer from restricted to satiation feeding, tissue RNA : DNA ratios were rapidly restored to initial levels. The uses of tissue RNA: DNA ratios both in evaluating nutritional status and as growth indices are discussed.
The effects of feeding regime on proximate body composition and patterns of energy deposition in juvenile Arctic charr, Salvelinus alpinus
Authors: Miglavs I. , Jobling M.
Published: January 2006

Juvenile Arctic charr, Salvelinus alpinus, subjected to either food deprivation or restricted feeding showed reductions in relative sizes of both liver and viscera. With food deprivation, percentage lipid decreased and percentage water increased in the eviscerated carcass, which is in agreement with findings for several other fish species. Following transfer from a restricted to a satiation feeding regime, the relative sizes of both liver and viscera increased to levels exceeding those of fish fed continuously to satiation. At the end of the experiment the percentage liver lipid content of restricted‐satiation fed fish was higher than in fish fed to satiation. These differences in energy deposition patterns were, however, not sufficiently large to produce marked differences at the whole animal level, since whole body lipid energy: protein energy ratios and energy utilization efficiencies were similar for restricted‐satiation and satiation fed fish.
Endocrine responses of brown trout, Salmo trutta L., to acid, aluminium and lime dosing in a Welsh hill stream
Authors: Whitehead C. , Brown J. A.
Published: January 2006

Brown trout caged in an acidic, softwater, Welsh hill stream running through close‐canopy conifer forest and in an adjacent, circumneutral, moorland stream were studied after a natural rainfall event and after experimental acid and aluminium dosing of the forest stream. Endocrine (cortisol and thyroxine) and metabolic (glucose) stress responses occurred in fish held in the forest stream. Liming downstream of the acid zones mitigated these responses.
Time‐course effects of repetitive oestradiol‐17β and thyroxine injections on the natural spring smolting of Atlantic salmon, Salmo salar L.
Authors: Madsen S. S. , Korsgaard B.
Published: January 2006

The impact of thyroxine and oestradiol injections on the smolting process of Salmo salar was investigated over 39 days. The increase in the degree of silvering was advanced by thyroxine but inhibited by oestradiol, as compared to controls. Oestradiol treatment increased the level of total calcium in the plasma, the hepatosomatic index and the concentration of RNA in the liver, indicating the induction of vitellogenin synthesis. The level of plasma chloride and protein in the liver remained unchanged in all experimental groups. Gill Na+/K+‐ATPase activity was low initially in the control fish, but increased steadily during the 39 days. The enzyme activity was advanced in the thyroxine‐treated fish, but inhibited by oestradiol. Gill chloride cell number increased in control fish and in the thyroxine‐treated fish until 25 days after the hormone treatment was initiated. Oestradiol‐treatment induced a lower chloride cell number on days 25 and 39. Altogether the present study demonstrates a reciprocal action of exogenous thyroxine and oestradiol during smolting in S. salar.
The muscle twitch and the maximum swimming speed of giant bluefin tuna, Thunnus thynnus L.
Authors: Wardle C. S. , Videler J. J. , Arimoto T. , Franco J. M. , He P.
Published: January 2006

Sustained swimming of bluefin tuna was analysed from video recordings made of a captive patrolling fish school [lengths (L) 1.7–3.3 m, body mass (M) 54–433 kg]. Speeds ranged from 0.6 to 1.2 L s−1 (86–260 km day−1) while stride length during steady speed swimming varied between 0.54 and 0.93 L. Maximum swimming speed was estimated by measuring twitch contraction of the anaerobic swimming muscle in pithed fish 5 min after death. Muscle contraction time increased from the shortest just behind the head (30–50 ms at 20% L) to the longest at the tail peduncle (80–90 ms at 80% L) (all at 28°C). A fish (L = 2.26 m) with a muscle contraction time of 50 ms at 25% L can have a maximum tail beat frequency of 10 Hz and maximum swimming speed of 15m s−1 (54km h−1) with a stride length of 0.65L. With a stride length of 1 L a speed of 22.6 m s−1 (81.4 km h−1) is possible. Power used at maximum speed was estimated for this fish at between 10 and 40 kW, with corresponding values for the drag coefficient at a Reynolds number of 4.43 × 107 of 0.0007 and 0.0027.
Seasonal correlative changes between sex steroids and lipid levels in the freshwater female catfish, Heteropneustes fossilis (Bloch)
Authors: Singh P. B. , Singh T. P.
Published: January 2006

Circannual variation in plasma levels of testosterone (T), oestradiol‐17β(E2) and 17α‐hydroxy‐progesterone (17α‐OHPg) were measured in female, Heteropneustes fossilis. T and E2 levels increased during the preparatory phase, reached their peak in the early prespawning phase and fell during the late prespawning phase to reach their lowest levels post‐spawning. 17a‐OHPg was detected from the late preparatory to the late spawning phase showing its peak during the early spawning phase. The levels of free fatty acids (FFA), monoglycerides (MG), diglycerides (DG), triglycerides (TG), phospholipids (PL), free cholesterol (CF)and esterified cholesterol (CE) were estimated in liver, plasma and ovaries. The preparatory phase showed hepatic lipogenic activity while during the prespawning phase TG lipolysis was increased by FFA. Ovarian CF was depleted by enhancing plasma E, levels during the prespawning phase. The gonadosomatic index reached its peak during spawning.
Diel variation in density, length composition, and feeding activity of juvenile alewife, Alosa pseudoharengus Wilson, and blueback herring, A. aestivalis Mitchill, at near‐surface depths in a hydroelectric dam impoundment
Authors: Jessop B. M.
Published: January 2006

Catches ofjuvenile blueback herring in near‐surface (0 to 1.5 m depth) waters, although greater at night than during the day, did not exhibit a strict negative phototropism because catches increased significantly with increasing illumination level during the forenoon and decreased with decreasing illumination during the afternoon. Juvenile alewife were absent from near‐surface waters during daylight. Feeding activity by blueback herring increased between dawn and dusk and ceased or slowed overnight but was not strictly positively phototropic. Low power (1‐β) of statistical tests due to high sampling variability and low (in hindsight) sample sizes precluded conclusions about the absence of die1 and spatial differences in the pattern of density, length composition, and of feeding activity of juvenile Alosa in those cases where the null hypothesis could not be rejected. Acceptable statistical power would require substantially increased (perhaps impractically so) sample sizes aided by an increase in a (probability of a type I error) from 0.05 to 0.1.
Serum cholesterol and triglyceride levels in Scyliorhinus canicula (L.) during sexual maturation
Authors: Garcia‐Garrido L. , Muñoz‐Chapuli R. , de Andres A. V.
Published: January 2006

A study was carried out on the serum levels of cholesterol [total (TC) and that associated with high‐density lipoproteins (HDLC)] and triglyceride (TG) in 127 specimens of Scyliorhinus canicula. The values obtained were correlated with sex, size, liver weight and reproductive stage. Results showed that male dogfish have higher levels of TC and HDLC, and lower TG than female. In adult males, TC increased and HDLC decreased with both size and spermatogenesis. Females carrying capsulated eggs showed a noticeable increase in TG together with a decrease of the HDLC levels, which were apparently not related with size.
Migratory and reproductive behaviour of female adult Atlantic salmon, Salmo salar L., in a spawning stream
Authors: Baglinière J. L. , Maisse G. , Nihouarn A.
Published: January 2006

Migration and spawning behaviour of eight Atlantic salmon adult females were analysed by radio‐tracking in relation to the degree of sexual maturity in a spawning tributary of the R. Sélune. Six of them were grilse and four of them were ripe. All the fish migrated upstream until reaching their spawning site at a distance of 4–12 km from the trap. The daily migration rate up to this site was inversely correlated with the length of the female. Spawning occurred in all fish at the same time when the water temperature increased dramatically. Spawning lasted 1–10 days according to the fish. After spawning, females quickly moved downstream only small distances and then stayed in approximately the same location until death. This study concluded that ripeness did not influence behaviour on the spawning migration and describes certain characteristics of the reproductive phase in a spawning tributary.
Production of juvenile Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., within different sections of a small enriched Norwegian river
Authors: Bergheim A. , Hesthagen T.
Published: January 2006

Growth, density and production of juvenile Atlantic salmon and brown trout were studied in three different sections of the Kvassheimsåna River in south‐western Norway from 1979 to 1983. Section 1. in the upper part of the river, is located above a waterfall impassable for migratory salmonids and is surrounded by grazing land. Sections 2 and 3, in the middle and lower parts of the river, are influenced by agricultural activity. Total nitrogen concentration varied between 250 and 1000 μg l −1 in section 1 and 1500 and 2500 μg l−1 in sections 2 and 3. Total phosphorus (Tot‐P) concentrations also increased with decreasing altitude: 19–46 μg l−1 in section I and 31–101 μg l −1 in sections 2 and 3.

The number of 0 + salmon in sections 2 and 3 varied between 30.1 and 167.8 specimens 100 m −2, with means 90.2 and 95.2 specimens 100 m −2:, respectively; the density of 1 + salmon, with mean values of 16.3 and 51.0 specimens 100m−2 was significantly correlated with the original fry density. The growth rate of 0+ salmon was not inversely related to cohort density, but was significantly so for 1 + salmon. Mean annual salmon production in section 2 was 1595 g 100 m−2 year 1, and in section 3 was 841 g 100m−2 year 1. A logarithmic function gave the best curve fit between salmon production and mean annual biomass. Thus, production levelled off for the highest values recorded in section 2, and perhaps approached the carrying capacity of the stream. A multiple regression analysis showed that yearly variation in 1 + salmon density was the single factor accounting for most of the total variability in production (60%). Variation in water temperature and nutrient content were not significantly related to variation in fish production.

Densities of brown trout were low in all sections (<20 specimens 100m −2). Fry density was highest in section 3 and parr density in section 1. All age groups of sympatric brown trout grew significantly faster in sections 2 and 3 compared with allopatric brown trout in section 1.
Seasonal variations in biochemical and physicochemical properties of actomyosin and energy content of the liver, gonads and muscle of mature Argentine hake, Merluccius hubbsi Marini
Authors: Montecchia C. L. , Crupkin M. , Truccos R. E.
Published: January 2006

Seasonal variations in energy content of liver. gonads and muscle, and the condition factor (K) of mature hake, were investigated. High energy content values were found in the liver after spawning and during thegonadal restingperiod. Lowenergycontent valuesin liverand highenergycontent values in gonads were observed during the gonadal growth period. In some periods of the reproductive cycle, low values of energy content of muscle were found.

The condition factor profile was similar to the energy content profile of liver and muscle. Physicochemical and biochemical properties of actomyosin were monitored by reduced viscosity and Mg2+‐ATPase activity. The profiles of these properties were similar to that of the condition factor.
A field experiment on the effects of interspecific competition from roach, Rutilus rutilus (L.), on age at maturity and gonad size in perch, Percafluviatilis L.
Authors: Persson L.
Published: January 2006

The effects of interspecific competition from roach on gonad development in O+ and 1+ perch were studied in a pond experiment by varying the roach density between treatments. The proportion of mature O+ males first increased and, thereafter, decreased with increasing roach density and increasing somatic weight. O f females were immature and all I+ males were mature. The proportion of mature 1+ females decreased with increasing roach density and decreasing somatic weight. The gonad weight of O+ and 1+ males as well as 1+ females decreased with increasing roach density and decreasing somatic weight. For 1+ males, which were individually marked, both start weight as well as somatic end weight were positively related to gonad weight. One possibleexplanation for the hump shaped relationship between the proportion of mature O+ males and somatic weight is that behavioural interactions between O+ and I+ males in the absence of roach affected maturing in O+ males. This study supports previous suggestions that annual variation in resource availability may give rise to variance in fecundity‐body size relationships.
Diet composition and prey preference of tench, Tinca tinca (L.), common bream, Abramis brama (L.), perch, Perca fluviatilis L. and roach, Rutilus rutilus (L.), in two contrasting gravel pit lakes: potential trophic overlap with wildfowl
Authors: Giles N. , Street M. , Wright R. M.
Published: January 2006

The abundance of benthic macroinvertebrate taxa and the relative abundance of zooplankton taxa were compared with the diet of bream, tench. perch and roach from two gravel pit lakes during May‐July 1986 and 1987. Significant food preferences were demonstrated between species and between lakes. Chironomid pupae dominated the macroinvertebrate diet of perch, roach, ate predominantly either Spirogyra sp. (St Peters Lake) or Daphniu hyalina (Main Lake).

The Main Lake, bream fed largely upon chironomid larvae and the bivalve Sphuerium but in St Peters Lake they positively selected a variety of less abundant benthic invertebrate taxa. Bream switched from benthos to zooplankton in the Main Lake in 1986. Tench ate large numbers of Aselhs and showed positive selection of various macroinvertebrate prey in St Peters but ate D. hjulim in Main Lake. Tropic overlap for chironomids and other macroinvertebrate prey was demonstrated between perch, bream and tench, and potentially with wildfowl which used the gravel pits for breeding and wintering.
Seasonal and spatial microhabitat selection and segregation in young Atlantic salmon, Salmo salar L., and brown trout, Salmo trutta L., in a Norwegian river
Authors: Heggenes J. , Saltveit S. J.
Published: January 2006

Seasonal microhabitat selection by sympatric young Atlantic salmon and brown trout was studied by diving. Both species, especially Atlantic salmon, showed seasonal variation with respect to surface and mean water velocities and depth. This variation is partly attributed to varying water flows and water temperatures. In winter the fish sought shelter in the substratum. A spatial variation in habitat use along the river due to different habitat availabilities was observed. Both species occupied habitats within the ranges of the microhabitat variables, rather than selecting narrow optima. It is hypothesized that the genetic basis allows a certain range to the behavioural response. Microhabitat segregation between the two species was pronounced, with brown trout inhabiting the more slow‐flowing and partly more shallow stream areas. Atlantic salmon tolerated a wider range of water velocities and depths. Habitat suitability curves were produced from both species. It is suggested that habitat suitability curves that are based on observations of fish occupancy of habitat at median or base flow may not be suitable in habitat simulation models, where available habitat is projected at substantially greater water flows.
The staining of fish otoliths for age determination
Authors: Richter H. , McDermott J. G.
Published: January 2006

Attempts were made to find methods for the staining of fish otoliths which would give results comparable to those of the Christensen burning technique. A variety of different histological stains and otoliths of different species were experimented with. Otoliths of sole, turbot, brill and scad gave best results when sectioned and stained in acidified Neutral Red, whereas those of cod, hake, whiting, plaice and grey mullet showed up the annuli better when dyed in aqueous Aniline Blue or Toluidine Blue and then sectioned. Small, translucent otoliths such as those of pelagic species may be enhanced by staining in Eosin Y.
When galaxiid and salmonid fishes meet–a family reunion in New Zealand
Authors: McDowall R. M.
Published: January 2006

New Zealand's small freshwater fish fauna has been augmented by introductions of exotic species, primarily salmonids. Brown and rainbow trout have been successful and the chinook salmon has established anadromous populations. Although few explicit data are available, it appears that addition of large salmonids has had harmful impacts on some indigenous species, particularly several galaxiids; these appear to result from predation and competitive exclusion. Interactions may be chronic or catastrophic. It is difficult to determine causes of chronic interactions, many instances of which are likely to be occurring and escaping notice. Further, it is difficult to separate the effects of human‐induced habitat deterioration from inter‐specific interactions. Catastrophic interactions are much easier to observe but even here determining the nature of interactions and ascribing causes is fraught with difficulties.
Fish of the Amazonian IgapÔ: stability and conservation in a high diversity‐low biomass system
Authors: Henderson P. A.
Published: January 2006

Water depth in the Amazon basin can differ by more than 11 m between low and high water periods in the annual cycle. When the water is high, the forest streams inundate the surrounding low‐lying forest creating vast lakes. Where the water originates from the forest it is rich in humic acids and low in dissolved nutrients. Such waters are termed blackwaters. Igapó is the specialized inundation forest of blackwater regions. Until recently it was generally held that the blackwater fauna was impoverished and of low biomass. However, recent studies have shown that these waters hold a specialized fauna living within and upon allochthonous input from the forest. Within submerged litter banks a diverse ichthyofauna forming dense local populations has been found.

Information on the spatial organization, population density and food web of this fauna will be presented. It is argued that this community is highly vulnerable to deforestation and its long‐term future can only be assured if the forest is conserved. This is not to suggest that these fish are not adaptable to disturbance as the community has evolved to live with changing water levels and the loss of submerged wood and leaf‐litter habitat. It is a remarkable example of a climax community exhibiting high diversity and low total population sizes within a variable habitat. Its conservation is of economic importance to the local human population whose diet includes a high proportion of fish.
Threatened fishes in Australia–an overview
Authors: Pollard D. A. , Ingram B. A. , Harris J. H. , Reynolds L. F.
Published: January 2006

Considering the size of the continent, the Australian freshwater fish fauna is a relatively depauperate one, comprising only about 192 species (belonging to 34 families) which spend significant portions of their life cycles in freshwater habitats. Of these freshwater species, the latest (1989) analysis indicates that six can be classified as endangered, five as vulnerable, four as potentially threatened, two as indeterminate, 32 as restricted, and 16+ as of unknown status, totalling 65 + species. Thus approximately 34% of the entire Australian freshwater fish fauna falls within the above six conservation status categories, which were established by the Australian Society for Fish Biology in 1985. Conservation problems of these fishes, and particularly man‐made changes to their habitats, are discussed, and some possible management solutions outlined. Brief mention is also made of several marine species which may also fall into one or more of the above conservation categories, although not enough information is yet available to classify them accurately.
The population ecology of rare species
Authors: Gaston K. J. , Lawton J. H.
Published: January 2006

There is no general theory of rarity, although one is sorely needed both to understand population dynamics and to determine conservation priorities. Here we suggest some of the strands that might be woven into such a theory. They include relationships between local abundance, geographic range size and body size of species, and the determinants of minimum viable population sizes. In each of these areas much can still be learnt from the classical ‘compare and contrast’ approach using assemblages of species from a variety of taxa. Freshwater fish have contributed relatively little to the broad ecological literature in this respect. We perform some tentative analyses for this group of species, and speculate on how they might fit into our current understanding of rarity.
The endurance of endemism: the Mediterranean freshwater gobies and their prospects for survival
Authors: Miller P. J.
Published: January 2006

Gobies (Teleostei: Gobiidae), spawning in fresh waters of the Mediterranean catchment area, are listed, and their diagnostic features and relationships summarized. The species, by zoogeographic category, include (i) Mediterranean: Padogobius martensii (Günther, 1861) and P. nigricans (Canestrini, 1867) from the northern Adriatic and west‐central Italy, (ii) West Balkanian: Economidichthys pygmaeus (Holly, 1929) and E. trichonis Economidis & Miller, 1990, and (iii) Ponto‐Caspian: Prorerorhinus marmoratus (Pallas, 1811) and Knipowitschia caucasica (Kawrajsky, in Berg, 1916), from the northern Aegean area but otherwise widespread in the Ponto‐Caspian region, and the endemic Mediterranean K. punctatissima (Canestrini, 1864) (north‐eastern Italy) and K. thessala (Vinciguerra, 1921) (Thessaly). Scenarios for differentiation following the late Miocene Messinian salinity crisis are outlined. The vulnerability of these species is discussed, and their present status reviewed. Populations no longer exist at the precise type localities of E. pygmaeus (Lefkas) and K. thessala (Hasabali spring, Pinios river system). Special features of scientific and cultural interest are noted, and the biological capability for species recovery is assessed.