bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative study of sexual cycles, oogenesis and spawning of two Soleidae, Solea lascaris (Risso, 1810) and Solea impar (Bennet, 1831), on the western coast of Brittany
Authors: Deniel C. , Le Blanc C. , Rodriguez A.
Published: January 2006

Two sand sole species, Solea lascaris and Solea impar, are common on the western coast of Brittany, France. Their reproduction (oogenesis and spawning) has been studied by following the gonadosomatic index, histological changes in ovary development, and oocyte diameter distribution. Both species have a prolonged spawning season, from spring to late summer. Each mature female breeds twice during the spawning season: in May and July for 5. lascaris, and in early June and July for 5. impar. Throughout the spawning season, several oocyte batches undergo vitellogenesis and there is a continuous recruitment of immature or primary oocytes into vitellogenesis. The two species are thus serial synchronous spawners. This, together with oocyte atresia late in the season (especially noticeable in S. impar) makes fecundity estimation difficult.
Induction of developmental abnormalities in larval goldfish, Carassius auratus L., under cool incubation conditions
Authors: Wiegand M. D. , Hataley J. M. , Kitchen C. L. , Buchanan L. G.
Published: January 2006

Compared with incubation at a constant 22° C, exposure of goldfish embryos and larvae to 13° C, under a variety of thermal protocols, caused increased frequencies of abnormal development and, in some cases, reduced survival to hatching. The low‐temperature incubation conditions were particularly deleterious when eggs were incubated at 13° C from the outset, regardless of the temperature at which the donor female ovulated and the eggs were fertilized. Significantly higher frequencies of developmental abnormalities were also noted when embryos were transferred from 22°C to 13°C at 6, 24, 128 and, in one case, 175 h after fertilization. In three of five experiments, subjecting embryos and larvae to diel fluctuations between 22 and 13° C, with a 5‐h hold at the lower temperature, caused an increase in development abnormalities. These results demonstrate that the thermal requirements of goldfish embryos and larvae necessitate a delay in ovulation and spawning until water is sufficiently warm. Developmental abnormalities can be induced by exposure to cool (13° C) conditions, at least up to the time that swimbladder inflation occurs.
Growth dynamics of myotomal muscle fibres in a carangid, Caranx malabaricus (Cuv. et Val.)
Authors: Kundu R. , Mansuri A. P.
Published: January 2006

The growth pattern of myotomal red, pink and white muscle and its relation to somatic growth in Caranx malabaricus are described. The growth pattern of red muscle was by an increase in fibre number in early size classes (< 22 cm f.l.) and thereafter mainly by increase in fibre diameter and partly by increase in fibre number. The growth of pink muscle was mainly by an increase in fibre diameter, but in smaller fish an increase in fibre number was also evident. White muscle growth was mainly by an increase in fibre diameter and partly by increase in fibre numbers in fish < 22 cm f.l., but only by an increase in fibre diameter from 22 cm f.l. onwards. Caranx malabaricus is a slow‐to‐moderate growing species and its fibre growth pattern matches with such somatic growth.
Size of prey ingested by whitefish, Coregonus sp., larvae. Are Coregonus larvae gape‐limited predators?
Authors: Ponton D. , Müller R.
Published: January 2006

The feeding ecology of whitefish, Coregonus, larvae in oligotrophic Lake Sarnen and eutrophic Lake Hallwil is presented, taking into consideration the size of the prey ingested in relation to the mouth size of larvae and to the availability of zooplankton.

When larvae grow from 10 to 16 mm their mouth width increases from 500 to 1000 μm while their gape height, with the mouth open at 45 and 90°, increases from 200 to 400 μm and from 400 to 700 μm, respectively, whichever lake is considered.

The differences found in the mean prey width between the two lakes arise in part from the composition of diets, and in part from differences in size of the available prey organisms. Whatever the origin of the larvae and the taxon we consider, larvae seem to ingest the most abundant prey size without selecting the biggest ones available even if, from a mechanical point of view, they would be able to ingest them.

Taking into account the generally low density of zooplankton in the uppermost layer of the lake, we conclude that whitefish larvae eat in the manner such as to decrease the cost of prey capture, in terms of energy and time, by choosing the more abundant prey available.
Direct and indirect evidence for polypeptide absorption by the teleost gastrointestinal tract
Authors: McLean E. , von der Meden A. C. , Donaldson E. M.
Published: January 2006

The ability of the gastrointestinal tract of chinook salmon, Oncorhynchus tshawytscha, to absorb polypeptides in vivo was investigated by reference to the appearance of orally administered adrenocorticotropic hormone (ACTH) within the blood of fish previously treated with dexamethasone (3μg g−l body weight) in order to suppress endogenous ACTH secretion. Further, since cortisol presence within plasma is dependent upon the availability of ACTH, dexamethasone blockade of endogenous ACTH secretion, in conjunction with subsequent measurements of plasma cortisol levels, provides a means by which biological patency of absorbed exogenous ACTH may be demonstrated. Levels of ACTH and cortisol in plasma of dexamethasone‐treated salmon were therefore measured for a period of 360 min immediately following oral intubation of ACTH (15μg g−1 body weight). Peak plasma presence of ACTH‐like immunoreactivity (676.6 ± 33.6 pg ml−1 plasma) and cortisol (227.1 ± 29.0 ng ml−1 plasma) were recorded 120 min after ACTH administration. Results from the experimental groups were compared to those of 15 control treatments. Since administration of ACTH to chinook salmon elicited a consistent and significant elevation in not only plasma ACTH but also cortisol presence, it is contended that the salmonid gut expresses an ability to absorb polypeptides of dietary origin. The significance of these findings with respect to the oral administration of biologically active peptides and proteins to fish of importance to aquaculture is discussed.
Using otolith weight to age fish
Authors: Pawson M. G.
Published: January 2006

The problem of determining and verifying ages of fish, from populations having a considerable variation in size at age, has been investigated using the relationship between otolith size and fish size, which has been shown by several authors to be influenced by growth rate. In such a population of Sardinella aurita Val. an index of age can be obtained for individual fish by calculating the equivalent otolith weight at a particular fish length, using the otolith weight–fish length relationship determined for each age group. This statistic not only permits a much greater proportion of fish to be assigned ages than is possible with otolith reading alone, but also enables the age groups to be verified as year classes. However, it is concluded that, although appropriate models based on otolith‐fish size relationships can predict age for groups of fish in which growth rates are known or can be assumed to be consistent, such techniques have a limited application in ageing fish from wild populations with highly variable growth rates.
Orientation of carp, Cyprinm carpio L., to free amino acids from Tubifex extract in an olfactometer
Authors: Saglio Ph. , Fauconneau B. , Blanc J. M.
Published: January 2006

We analysed the effects of L‐amino acid combinations, tested at the same relative concentrations as in 500 mgl1 of a filtrated Tubifex extract, on attraction and exploratory behaviour of juvenile carp, Cyprinus curpio L., in an olfactometer. Tubifex filtrate was significantly active in the range of concentrations tested (5 mgl−1, 50 mgl−1, 500 mgl−1, 5 gl−1). Maximum attraction was obtained in response to a concentration of 500 mg l−1. Soluble TCA fraction and a mixture of the 17 synthetic amino acids found in this fraction also showed significant effects on attraction and exploratory behaviour. Tests of the four chemical groups of amino acids gave the following results: acidic amino acids (aspartic and glutamic) did not produce significant activity. Basic amino acids (histidine, arginine and lysine) and polar, uncharged amino acids (glycine, serine, threonine, tyrosine, asparagine and glutamine) were ineffective as attractants but significantly increased exploration. Non‐polar amino acids (alanine, valine, leucine, isoleucine, phenylalanine, and methionine) showed significant effects on both attraction and exploration. In tests where different pairs of these amino acid groups were mixed it was shown that a combination of non‐polar amino acids and polar uncharged amino acids was the most effective in inducing both attraction and exploration. The simplest combination to have a significant effect on both attraction and exploration was alanine, valine and glycine.

These results are discussed in the light of recent data on the role of free amino acids in the behaviour of fishes.
A stereological method for estimating fish fecundity
Authors: Emerson L. S. , Walker M. Greer , Witthames P. R.
Published: January 2006

This paper describes the application and evaluation of a stereological method for counting fish oocytes. The method has been applied to herring, Clupea harengus L., Dover sole, Solea solea L., and mackerel, Scomber scombrus L., and compared with existing volumetric and/or automated particle counter methods. The stereological method has been shown to given similar results and to have a number of distinct advantages over the other methods.
The ornamental fish trade and fish conservation
Authors: Andrews C.
Published: January 2006

The global trade in ornamental fish and associated aquarium and pond accessories is in excess of U.S. $7 × 109 each year. Although the majority of freshwater fish involved in the trade are from captive‐bred sources, significant numbers are still removed from the wild. In addition, almost all of the marine fish in the trade are wild‐caught. Whilst habitat destruction, pollution and overfishing for food are the main threats facing fish populations in the wild, the ornamental fish trade may have adverse effects as a result of the introduction of nonnative organisms, and by the direct depletion of wild stocks. The ornamental fish trade is ideally placed to raise public awareness of, and actively support, fish conservation efforts, and must maintain a close liaison with legislative‐forming organizations seeking to impose further trade restrictions.
Conservation status of the North American fish fauna in fresh water
Authors: Williams J. E. , Miller R. R.
Published: January 2006

The status of the North American fish fauna includes 292 species of fishes in the categories of endangered, vulnerable, rare, indeterminate, and extinct. This constitutes 28% of the known fauna. The status of fishes and their habitats continues to decline, especially in the arid regions of western U.S.A. and northern Mexico. The Endangered Species Act is the most powerful tool currently available to protect rare fishes. While many fishes probably have been saved from extinction by this Act, surprisingly few have improved enough to be removed from under its protection.
Conservation of the huchen, Hucho hucho (L.), (Salmonidae) with special reference to Slovakian rivers
Authors: Holčik J.
Published: January 2006

The world's biggest salmonid, the huchen, Huchu hucho (L.), is now threatened with extinction, especially the nominate form—the Danubian huchen—which is confined to the basin of the River Danube. About 50 years ago the huchen occupied almost 12 000 km of river in Europe but it is now common in only about 33% of its former distribution, is rare in 28% and has disappeared from 39%. The continuous area formerly inhabited by the huchen is now disrupted into isolated sections. This large predatory fish has been pushed back to the submountain zone of rivers, and its density has decreased considerably. This is the combined result of increased regulation of streams, damming of rivers, industrial and agricultural pollution and other factors causing the destruction of the huchen's habitat. Protective measures have been applied, involving legal restrictions, restocking, the establishment of reserves and introductions into rivers not previously inhabited by the huchen. These measures have failed due to continuing pollution of rivers and the low numbers of fingerlings available for restocking.
Aspects of the reproductive biology of the bass, Dicentrarchus labrax L. II. Fecundity and pattern of oocyte development
Authors: Mayer I. , Shackley S. E. , Witthames P. R.
Published: January 2006

The European bass, Dicentrarchus labrax L., in common with most temperate marine teleosts, exhibits a distinct seasonal reproductive cycle. Its reproductive strategy is characterized by a high absolute fecundity (2‐25 × 105), both absolute and relative fecundity increasing with size and age. The cyclic pattern of oocyte development has been determined by histology and from oocyte size frequency analysis. Results show that the bass exhibits group‐synchronous oocyte development and is a ‘fractional spawner’, i.e. it spawns a number (3–4) of discrete clutches in quick succession, successive clutches containing fewer oocytes. All oocytes which are recruited into the secondary growth phase (> 110 μrn) are either spawned that season or become atretic, i.e. no secondary oocytes are held over for the subsequent reproductive season.
The fine structure of muscle fibres of roach, Rutilus rutilus (L.), and chub, Leuciscus cephalus (L.), Cyprinidae, Teleostei: interspecific differences and effects of habitat and season
Authors: Sänger A. M. , Kim Z. S. , Adam H.
Published: January 2006

Red and white axial muscle fibres from roach and chub were investigated by electron microscopy. Fish from three different localities were compared. Qualitative and quantitative analysis of myofibrils, mitochondria, lipid and subsarcolemmal cytoplasm with regard to muscle fibre type, species, season and habitat were made. Muscle fibre types differ significantly with the exception of the subsarcolemmal cytoplasm in roach. Within‐species lipid content of red fibres differs between seasons. However, the most marked effect on red muscle fibres within species and season as regards volume density of lipid and mitochondria can be attributed to the different localities. The results are discussed in relation to mode of life and differences in habitat.
Some morphological aspects of fertilization in tilapias
Authors: Bern O. , Avtalion R. R.
Published: January 2006

The relationship between the specific anatomy of tilapia gametes and their function was studied in the sequence of events which follow artifical fertilization. Scanning electron microscopic observations showed that some events of the fertilization process, involving spermatozoon migration through the micropylar canal until reaching the villous plasma membrane of the eggs and its penetration into the egg cytoplasm, occur very rapidly (fractions of a second). However, the spermatozoon tail remains outside for about 1–2 min. Then, following the zygote formation and the elevation of the chorion after its separation from the plasma membrane, numerous sperm cells could be found in the vicinity of the micropyle. This cell mass, which seemed to be trapped by a network of microfilaments, was suggested to be the result of the evacuation of excess sperm cells throughout the micropylar canal. The significance of these results for sperm and egg plasma membrane interaction and for prevention of polyspermy are discussed.
A taxonomic reappraisal of the Atlanto‐Mediterranean soles Solea solea, S. senegalensis and S. lascaris
Authors: Ben‐Tuvia A.
Published: January 2006

Examination of morphometric characters of Solea aegyptiaca shows that it cannot be separated from Solea solea. Diagnostic characters are given to separate this species from S. senegalensis. The available data show that Solea impar and S. nasuta are junior synonyms of S. lascaris. Meristic characters of S. solea and S. lascaris vary greatly according to the geographical origin of the examined fishes, indicating the influence of temperature on the number of vertebrae and fin rays. A key is provided for the identification of the four species of the genus Solea known in the Atlanto‐Mediterranean region.
Opsonic effect of antiserum and complement on phagocytosis by macrophages from the peritoneal cavity of the Japanese eel, Anguilla japonica
Authors: Kaige N. , Miyazaki T. , Kubota S. S.
Published: January 2006

Macrophage exudates in the Japanese eel, Anguillu japonica, were induced by intraperitoneal injection with a mixture of Edwnrdsiella bacterin, proteose peptone and liquid paraffin, and the opsonic effect of antiserum and complement on the phagocytic activity of the macrophages was studied.

The macrophages contained a round nucleus with a nucleolus, and an agranular cytoplasm with projecting processes. These cells showed phagocytosis of sheep red blood cells (SRBC). An opsonic effect of antiserum was recognized in terms of a significant increase of macrophage phagocytic activity against SRBC treated with antiserum relative to that against SRBC treated with inactivated normal serum. Complement, however, did not enhance the phagocytic activity of macrophages.
Transfer of antibody activity from immunized mother to embryo in tilapias
Authors: Mor A. , Avtalion R. R.
Published: January 2006

Antibody activity specific to antigens (PSA, DSA and BGG) which served for immunization of mothers could be measured in extracts of 0‐9‐day‐old embryos spawned by these mothers, using a modified ELISA. The level of antibody activity in embryos varied according to the interval of time between mother immunization and spawning. This activity peaked between 14 and 37 days post‐immunization, then it underwent a significant gradual decrease. The activity of the extract was found to be specific only to the antigen which served for the mother immunization and could be adsorbed only by these antigens. The need of mother immunization against selected pathogens for the prevention of larvae and fry mortality is discussed.
Scale morphology and squamation patterns in cichlids (Teleostei, Perciformes): A comparative study
Authors: Lippitsch E.
Published: January 2006

Problems in cichlid systematics call for new characteristics to be exploited. Scale surface morphology and squamation patterns could provide novel and useful information. A comparative study comprising 105 African, 10 American, and eight outgroup species was conducted to identify the most useful scale and squamation characters within the family and to clarify their phylogenetic significance. A great number of obviously genetically fixed characters were established. At least IS scale granulation types could be identified, proving to be ofparticular value for systematic purposes. Squamation patterns on the head, breast and fins were also found to be of interest in this context. Different character states are described and their distribution is reviewed, together with a discussion of their plesiomorphic status. From the results it can be concluded that for the Cichlidae scale and squamation studies can be valuable tools in investigating phylogenetic relationships.
Spatial organization and population density of the fish community of the litter banks within a central Amazonian blackwater stream
Authors: Henderson P. A. , Walker I.
Published: January 2006

Results of a study of the fish community of the leaf litter banks in the lower reaches of the Taruma‐Mirim, a small central Amazonian stream is presented. The Taruma‐Mirim is an acidic, blackwater, forest stream which flows through igapo forest and enters the Rio Negro close to Manaus. The commonly held view that these blackwaters hold an impoverished ichthyofauna is challenged. The studied litter banks hold about 20 species of fish, all of which were found to live within distinct subregions of the habitat. Average fish density was about 100 individuals m−2. Absolute population sizes were found to be remarkably small; within a 200 m2 area the most abundant species had a population size of about 104 and the least abundant <102 individuals. It is argued that high species richness linked to specialized habitat requirements and small population size indicates considerable population stability. The factors leading to the evolution of such species richness are discussed.
Functions of the testicular gland in two blenniid fishes, Salaria (=Blennius) pavo and Lipophrys (= Blennius) dalmatinus (Blenniidae, Teleostei) as revealed by electron microscopy and enzyme histochemistry
Authors: Lahnsteiner F. , Richtarski U. , Patzner R. A.
Published: January 2006

The functions of the testicular gland in two different blenniid fishes, Salaria pavo and Lipophrys dulmutinus, are described by fine structural and enzyme histochemical methods. In the testes of the two fishes no mature spermatozoa are found. Sperrniogenesis occurs only until the spermatidal stage. Spermatids are released into the testicular gland. During the spawning period the testicular gland functions in differentiation of spermatids, nutrition of spermatids, and secretion of sialomucins. After spawning, the testicular gland has phagocytotic functions in resorbtion of remaining spermatids, which are transformed into lipids in the gland cells. During the interspawning period the testicular gland is a storage reservoir for lipids and phospholipids which are re‐transformed into testicular gland secretion in the next reproductive season. Testicular gland cells themselves do not have steroidogenetic functions, but steroids are synthesized by interstitial cells homologous to Leydig cells in other fish. Possible explanations for the reduction of the testis in L. dalmatinus and implications of the testicular gland in taking over testicular functions are discussed.
Temperature requirements for growth and survival of larval vendace, Coregonus albula (L.)
Authors: Luczynski M.
Published: January 2006

Water temperatures from 15.0 to 20.0° C are recommended as the most suitable for sustained production of larval vendace, as indicated by the developmental rates, the instantaneous rates of growth, mortality, and the net biomass gain of larvae reared at eight constant temperatures from 4.8 to 22.1° C. The recommended temperatures are optimal when the available food and photoperiod are not the limiting factors. Temperatures higher than 22.0° C will cause increased mortality, whereas temperatures lower than 15.0° C, although advisable when food is limited, will retard larval growth and development.
Polymorphism of myofibrillar proteins in histochemically identified myotomal muscle fibre types of Heteropneustes fossilis (Bloch) and Labeo rohita (Hamilton)
Authors: Jasra P. K. , Talesara C. L. , Kiran Shashi
Published: January 2006

Myofibrillar proteins in the myotomal muscle fibre types of two freshwater teleosts, Heteropneustes fossilis (Bloch) and Labeo rohita (Hamilton), were investigated. The fibre types were identified histochemically based on the reactivities of the enzymes SDH and m‐ATPase. Electrophoretic analysis revealed distribution patterns of myosin light chains, tropomyosin, troponin, c‐ and m‐protein; specific to the muscle fibre types. The results correlate well with the general pattern of myofibrillar protein distribution found in the skeletal muscles of higher vertebrates. The significance of the present findings are discussed with regard to histochemical, biochemical as well as functional properties of the muscle fibre types.
Growth in four populations of Leporinus friderici (Bloch, 1794) (Anostomidae, Teleostei) in French Guiana
Authors: Boujard T. , Lecomte F. , Renno J.‐F. , Meunier F. , Neveu P.
Published: January 2006

The growth rates of Leporinus friderici (Bloch, 1794) in four populations from four rivers of French Guiana are compared. According to a statistical analysis of growth curves using the method of maximum likelihood with the Gauss–Markardt algorithm, a marked difference is observed in the growth of the different samples which is attributed to the year of capture rather than to the geographical origin of fishes. It is demonstrated that the main factor affecting growth performances is the length of the rainy season, which corresponds for this species to the feeding period.
Coupling of heart rate and locomotor activity in sole, Solea solea (L.), and bass, Dicentrarchus labrax (L.), in their natural environment by using ultrasonic telemetry
Authors: Sureau D. , Lagardére J.‐P.
Published: January 2006

Field measurements of distance moved and heart rate in sole, Solea solea (L.) and bass, Dicentrarchus labrax (L.) using ultrasonic telemetry revealed two different strategies. Heart rate in the sole increases during activity, accurately reflecting fluctuation in metabolic rate and so can be used as a measure of metabolic rate in the field. In contrast, the relatively stable value of the heart rate in bass during the whole tracking period whatever the activity level suggests that in this species heart rate in the field cannot be associated with metabolic rate determination.
Effects of group size on the responsiveness of zebrafish, Brachydanio rerio (Hamilton Buchanan), to alanine, a chemical attractant
Authors: Steele C. W. , Scarfe A. D. , Owens D. W.
Published: January 2006

Previous studies have examined the effects of grouping on the locating (search) phase of foraging and feeding behaviour in fishes. Few studies have examined whether schooling in fishes may facilitate individual foraging by enhancing a group's responsiveness to food odours. The purpose of the current study was to assess the effect of increasing group size on the responsiveness of zebrafish, Brachydanio rerio (Hamilton Buchanan), to L‐alanine, an amino acid which is an important constituent of prey odours for many fishes. Based on the results of previous studies, either an increasing or decreasing linear relationship or a unimodal (convex or concave) relationship between responsiveness and group size was expected; the results, however, were bimodal. Groups of four fish were most responsive to alanine, as determined by the mean percentage of occurrences of fish in the area of a behavioural arena (an octagonal fluviarium) into which alanine was infused (at 10−3, 10−4, or 10−5 M). Groups of two, six and eight fish were significantly less responsive (P < 0.05) than either groups of four fish or individual fish. The responses of groups of two, six and eight fish were not significantly different from each other.
Hierarchical response to prey stimuli and associated effects of hunger and foraging experience in the fifteen‐spined stickleback, Spinachia spinachia (L.)
Authors: Croy M. I. , Hughes R. N.
Published: January 2006

Responsiveness of fifteen‐spined sticklebacks, Spinachia spinachia (L.) to motility (rotating or still). size (larger or smaller), colour (red or green), shape (rectangular or tapered) and location (near bottom or surface of water) was investigated by presenting fish with binary choices of artificial prey, constructed from frozen mysids, trimmed, dyed and fixed to adjustable, motorized rods. Responsiveness was in the order movement > size > colour > shape = location. In natural situations, movement may distinguish edible from inedible objects, while size indicates profitability and feasibility for attack. Colour, shape and location are more specific stimuli. Sticklebacks familiar with Artemia are more responsive to red coloration, tapered shape and pelagic location, as opposed to green, rectangular and benthic characterizing Gammarus.
Stock and recruitment and inversely density‐dependent growth of salmon, Salmo salar L., in a Scottish stream
Authors: Gardiner R. , Shackley P.
Published: January 2006

For the 6 years for which detailed data are readily available, estimates of the survival of emergent fry of Atlantic salmon, Salmo salar L., to the first and second autumns at a site on the Shelligan Burn are consistent with the dome‐shaped Ricker model with about 11 emergent fry m−2 maximizing recruitment. The data are not satisfactorily fitted by the asymptotic Beverton and Holt model. A possible mechanism, which results from the observed inversely density‐dependent growth, is discussed briefly.
Effects of impoundment on populations of bullhead Cottus gobio L. and minnow, Phoxinus phoxinus (L.), in the basin of Cow Green Reservoir
Authors: Crisp D. T. , Mann R. H. K.
Published: January 2006

The distribution, growth and reproduction of bullhead, Cottus gobio, L., and minnow, Phoxinus phoxinus (L.), were studied at Cow Green Reservoir, Upper Teesdale, for 10 years following impoundment in 1970. Comparisons were made with pre‐impoundment results. The length‐for‐age of bullheads increased after impoundment. The length‐for‐age of minnows decreased. In winter both species were confined mainly to deep water or to the stone facing of the earth dam. In summer they were found throughout the reservoir though bullheads were scarce in the littoral zone. Female bullheads became sexually mature at an earlier age (84% at age‐group I) than before impoundment (33% at age‐group I) but no change was apparent amongst males (67–62% in age‐group I). The post‐impoundment sex ratio did not differ from 1:1 and individual fecundity did not change after impoundment. There was a significant reduction in individual fecundity of the minnow. The mean instantaneous rate of mortality (Z) for bullhead of age‐groups II to IV was 0.96 ± 0.34 year−1, compared with 0.85 ± 0.29 year in the Tees before impoundment.
Embryonic and larval development of brown trout, Salmo trutta L.: exposure to trace metal mixtures in soft water
Authors: Sayer M. D. J. , Reader J. P. , Morris R.
Published: January 2006

Freshly fertilized ova of brown trout, Salmo trutta L., were exposed to all possible mixtures of Al (6000 nmol 11), Cu (80 nmol 1−1), Pb (50 nmol 1−1) and Zn (300 nmol 1 1). In a separate experiment, newly hatched brown trout yolk‐sac fry were exposed to Mn (1500 nmol 1−1), Fe (2500 nmol 1 1), Ni (200 nmol 1−1) or Cd (4 nmol 1 1), separately, and in mixtures with either Al or Cu. Both experiments were conducted in flowing, artificial softwater media nominally at pH 5.6 [Ca] 20 μmol 1 1 and 10° C.

Mortalities were high in fry subjected to treatments which contained both Al and Cu (31–72%), and to the Cu + Fe treatment (78%) compared with those from the other trace metal mixtures (0–22%). In all the treatments tested, fry exposed to trace metal mixtures containing Al and/or Cu had reduced whole body Ca, Na and K content, and seriously impaired skeletal calcification. Whole body Mg content was variable. In trace metal mixtures which contained Cu but not Al, the effects on fry survival and whole body mineral content were in general more deleterious than the corresponding mixtures but with Al present rather than Cu. The presence of Pb and/or Zn in mixtures with Al and/or Cu had a slight ameliorative effect in terms both of fry survival and whole body mineral content.
Year‐class fluctuations in vendace, Coregonus albula (Linnaeus): Who's got the upper hand in intraspecific competition?
Authors: Sandlund O. T. , Jonsson B. , Naesje T. F. , Aass P.
Published: January 2006

The vendace Coregonus albula (L.) populations in the lakes Mjøsa and Osensjøen exhibited fluctuating year‐class strength. In Mjøsa, a strong year‐class emerged every third year, except for the four year period between the strong year‐classes 1969 and 1973. The difference between the strong and weak year‐classes decreased from the 1960s, through the 1970s to the 1980s. The Mjøsa vendace matured sexually at age 2 +, and more than ten sexually mature age‐groups were present in the population. Growth ceased at maturation, and asymptotic length was 23.6 cm. In Osensjøen, one strong year‐class (1969) dominated the population during the period 1976–1987. The Osensjøen vendace matured sexually at age 3, and more than 15 sexually mature age‐groups were present in the population. Growth ceased at maturation, and asymptotic length was 28.4 cm. In both lakes, vendace fed on crustacean zooplankton in the epilimnion throughout summer and autumn. Our data indicate that regular year‐class oscillations occur as a result of the juvenile survival being negatively correlated to the number of adults.
Growth rate and tissue magnesium concentration in adult freshwater tilapia, Oreochvomis mossambicus (Peters), fed diets differing in magnesium content
Authors: van der Velden J. A. , Spanings F. A. T. , Flik G. , Zegers C. , Kolar Z. I. , Bongat S. E.Wendelaar
Published: January 2006

The growth rate and magnesium concentration in scales, bone and muscle of freshwater tilapia, Oreochronüs mossambicus (Peters), initially weighing between 70 and 300 g, were followed during low‐magnesium feeding. The growth rate decreased in fish on low‐magnesium diets, but no changes were observed in the magnesium concentration in the scales, bone or muscle. No changes were observed in calcium or sodium concentrations in these tissues. We conclude that adult tilapia fed a low‐magnesium diet manage, in contrast to other fish species, to maintain their magnesium balance and must therefore obtain magnesium from the water.
Effects of development, temperature and salinity on metabolism in eggs and yolk‐sac larvae of milkfish, Chanos chanos (Forsskål)
Authors: Walsh W. A. , Swanson C. , Lee C.‐S.
Published: January 2006

Oxygen uptake rates and yolk‐inclusive dry weiGhts were measured during the egg and yolk‐sac larval stages of milkfish, Chanos chanos (Forsskal). Oxygen uptake by eggs and yolk‐sac larvae was measured to assess the effects of four salinities (20,25,30,35 ppt) at 28°C. The effects of three temperatures (23,28,33°C) on oxygen uptake by yolk‐sac larvae were determined at a salinity of 35 ppt. Dry weights were measured throughout embryonic development at 28°C and the yolk‐sac stage at 23.28 and 33°C.

Oxygen uptake rates of eggs increased more than fivefold during embryogenesis (0.07±0.03 to 0.40 ± 03 μl O2 egg −1 h −1;blastula to prehatch stage). Larval oxygen uptake did not change with age but was affected by rearing temperature (0.33 ± 0.08, 0.44 ± 0.07 and 0.63 ± 0.13 μl O2 larva −1 h−1 at 23, 28 and 33°C, respectively; Q10= 1.93). Acute temperature changes from 28 to 33°C caused significant increases in oxygen uptake by embryos (Q 10= 1.69–3.58) and yolk‐sac larvae (Q 10=2.55). Salinity did not affect metabolic rates.

Dry weight of eggs incubated at 28°C decreased 13% from fertilization to hatching. Incubation temperatures from 23–33°C did not affect dry weights at hatching. Rearing temperatures significantly affected the rate of larval yolk absorption (Q 10= 2.25).
Influence of environment upon the life history of gudgeon, Gobio gobio (L.): a recent and successful colonizer of the Iberian Peninsula
Authors: Lobon‐Cervia J. , Montańges C. , De Sostoa A.
Published: January 2006

The growth and the reproductive tactics of gudgeon, Gobio gobio (L.) were assessed in three contrasting streams of the Iberian Peninsula: the Rivers Moros and Ucero, tributaries of the R. Duero, and the R. MatarrańGa, a tributary of the R. Ebro. The R. Duero gudgeon have spread in the last 50 years while their presence in the lower tributaries of the R. Ebro followed the construction of reservoirs in the mid 1960s. The life histories of the Moros and MatarrańnGa gudgeon are very similar; rapid growth in spring, early reproduction (1 ‐year‐old), high reproductive cost, short life‐span and trend to semelparity. Both populations are strongly influenced by the severe summer droughts that result in (I) reduction in the condition coefficient, (2) reduction in the growth rate (particularly in the River MatarrańGa), (3) single spawning and (4) no gonad development in the summer. The gudgeon in the Ucero delay maturity, grow slower, are multi‐spawners and have a longer life span. All the Duero populations come from the same genetic pool and they are actually connected through the populations living along this river basin, whereas the MatarrańGa population is not genetically linked, we hypothesize that the differences between these populations are environmentally induced.
Water quality during egg incubation influences yolk‐sac fry sodium kinetics in Atlantic salmon, Salmo salar L.: a possible mechanism of adaptation to acid waters
Authors: McWilliams P. G. , Shephard K. L.
Published: January 2006

Atlantic salmon (Salmo salar L.) fry hatched from eggs transferred from high‐Na to low‐Na water during the eyed stage of development had a significantly higher Vmax and lower Km (P <0.01) of the sodium uptake mechanism than fry hatched from eggs incubated entirely in low‐Na or high‐Na water.

Fry hatched from eggs transferred to acid, high aluminium water during the eyed stage of development had a similar Vmax and Km to fry hatched from eggs incubated entirely in high‐ or low‐Na water. Eggs incubated continuously in acid, high aluminium (low‐Na) water produced fry with significantly lower Km and Vmax values than fry hatched from eggs incubated continuously in low‐Na water. Eggs and fry in acid, high aluminium water continually lost sodium and mortality was 100% at 5 5 M O degree‐days (2–3 weeks after hatching).

The results are discussed with respect to the influence of perivitelline fluid ion activities in eggs in acid, high aluminium water on the kinetic characteristics of sodium uptake in yolk‐sac fry. A possible mechanism for the long‐term adaptation of teleosts in acidified natural waters is also proposed.
Population dynamics of lymphocystis disease in estuarine flounder, Platichthys flesus (L.)
Authors: Lorenzen K. , Des Clers S. A. , Anders K.
Published: January 2006

The population dynamics of viral lymphocystis disease in an age‐structured population of flounder, Plarichthys flesus (Linnaeus 1758), is studied with a mathematical model. For a single cohort the model illustrates the influence of host density and acquired immunity on length‐prevalence profiles. This case corresponds to a host population at demographic equilibrium. When the model is extended to several cohorts, seasonal recruitment of susceptible hosts is shown to drive seasonality in disease prevalence. In both cases, there is good qualitative agreement between model predictions and field data from the Elbe estuary, Germany.
Seasonal and annual variations in the abundance of the clupeid Limnothrissa miodon in Lake Kivu
Authors: Marshall B. E.
Published: January 2006

There was no clear seasonal cycle in the abundance of the sardine Limnorhrissa miodon in Lake Kivu hut average values suggest that the fish are most numerous in the south from October‐April and in the north from April4ctoher. The possibility that there may be a migration from south to north is considered. The catch per unit effort appears to be independent of the present level of fishing effort but may be determined by the annual rainfall two years earlier. In this respect, Lake Kivu is similar to Lake Kariba where nutrient supply is determined by river flow.
Mitochondrial DNA diversity among four sympatric morphs of Arctic charr, Salvelinus alpinus L., from Thingvallavatn, Iceland
Authors: Danzmann R. G. , Ferguson M. M. , Skúlason S. , Snorrason S. S. , Noakes D. L. G.
Published: January 2006

Restriction fragment length polymorphisms in mitochondrial DNA (mtDNA) were examined in progeny of four sympatric morphs of Arctic charr (Salvelinus alpinus L.) from Thingvallavatn, Iceland. The mtDNA analysis with 46 hexanucleotide restriction enzymes indicates that the Thingvallavatn morphs are very closely related. Sequence divergence was less than 0.2% between any of the five clones detected. Although not significant, the topology of the mtDNA UPGMA dendogram was similar to that from a previous allozyme survey. Icelandic Arctic charr show greater affinity to charr from the British Isles than those from North America supporting their current taxonomic distinction.
Induction and reversal of the non‐reproductive state in winter flounder, Pseudopleuronectes americanus Walbaum, by manipulating food availability
Authors: Burton M. P. M.
Published: January 2006

Reversal of the non‐reproductive slate of winter flounders was induced by improved feeding.
Isozyme criteria in the testing of phyletic relationships between species of Gobius and related eastern Atlantic‐Mediterranean genera (Teleostei: Gobüdae)
Authors: McKay S. I. , Miller P. J.
Published: January 2006

Horizontal starch gel electrophoresis was employed to investigate allozyme variation at 19 isozyme loci, in nine closely‐related Atlantic‐Mediterranean gobiid fish species, to assess genetic relationships, and to compare this with a phyletic hypothesis based on morphological apo‐morphies. The species examined were Gobius niger, G. auratus, G. cruentatus, G. paganellus, Mauligobius maderensis, Zosterisessor ophiocephalus, Thorogobius ephippiatus, Padogobius martensii and P. nigricans. Various phenetic and cladistic analyses were performed on isozyme and morphological data. The phenetic and cladistic results from morphological data, and the cladistic results from isozyme data, were largely comparable, with P. martensü and P. nigricans forming a sister group to all the other taxa, species of Cobius forming a crown group within the latter, and stem lines formed by Mauligobius, Zosterisessor and Thorogobius, respectively. The isozymic estimates of genetic distance differed from these chiefly in the relative positions of Zosterisessor and G. auratus, which appear less similar to other species of Gohius. G. auratus shows many alleles which are unique within the genus Gobius; possible explanations for this are put forward. The position of nigricans as congeneric with Padogobius martensü is confirmed by both phenetic and cladistic analyses of isozyme data.
Evidence of protandry in a subantarctic notothenid, Eleginops maclovinus (Cuv. & Val., 1830) from the Beagle Channel, Argentina
Authors: Calvo J. , Morriconi E. , Rae G. A. , San Roman N. A.
Published: January 2006

Gonads of Eleginops maclovinus (Cuv. & Val., 1830) from the Beagle Channel (Tierra del Fuego, Argentina) were sampled weekly throughout the year and histologically analysed. Gonads containing solely or mostly testicular tissue were predominant in each length class smaller than 40 cm (80 to 100%). Sex ratio was almost 1:1 in fishes ranging from 41 to 45cm. Females were dominant in specimens larger than 46cm (80 to 100%). Four testicular types are described according to maturation degree and absence or presence of female cells, one intermediate gonadal type and one typical ovarian type. It is concluded that this species is a protandrous hermaphrodite.
A biotelemetry system recording fish activity
Authors: Kaseloo P. A. , Weatherley A. H. , Lotimer J. , Farina M. D.
Published: January 2006

A biotelemetry system is described for obtaining, transmitting and recording the electromyograms (EMGs) produced in muscle activity of free‐swimming fish as quantitative indicators of overall fish activity. The radiotransmitters used come in the form of cylindrical packages having two sensing electrodes, all fully implantable in the fish body cavity. EMGs are transmitted as radio pulses with the intensity of muscular activity determining the intervals between pulses. The packages also contain temperature sensors and fish temperatures are transmitted with every 32nd pulse. Transmitted EMG pulses are detected, ‘measured’ and stored by a single portable receiver (Model SRX_400, Lotek). Data can be subsequently transferred to a computer (which can also be portable) for storage, processing and statistical analysis. Transmitter battery life can be in excess of 7 months, permitting laboratory or field studies of long duration. Transmitter package implantation surgery requires a mid‐ventral incision and internal securing of transmitter and sensing electrodes. Surgical silk, cyanoacrylate tissue adhesives, and polydioxanone (PD), a synthetic absorbable suture, were all tried as means of incision closure. The most effective was PD alone. Trials of the system consisted of forced swims by transmitter‐equipped rainbow trout Oncorhynchus mykiss Walbaum. The data obtained provided an inverse linear relation between forced swim speed and EMG pulse interval. Trials were conducted at intervals over periods up to 2 months. Fish showed neither distress, nor difficulty in swimming up to maximum speeds of 60 cm s −1 (fish lengths 41.0, 44.4 cm).
Constraints on prey size selection by the three‐spined stickleback: energy requirements and the capacity and fullness of the gut
Authors: Hart P. J. B. , Gill A. B.
Published: January 2006

An experiment was designed to study how gut fullness and encounter with 5‐mm Asellus aquaticus influenced acceptance or rejection of less profitable 8‐mm Asellus. 45‐mm sticklebacks were found to always accept 5‐mm prey whereas 8‐mm prey were accepted with an initial probability of about 0.9. This probability decreased as the gut filled. Fish of differing sizes and sex had similar daily energy intakes per unit body size, however the acceptance of 8‐mm prey was related to fish size. Whenever a fish orientated to a prey it was followed by pursuit and manipulation independently of prey size. The decision to accept or reject prey occurred after one manipulation, a criterion that was more variable for the larger prey. For one feeding session per day the total energy intake was almost constant despite the changing combination of prey sizes eaten. The fish ate prey with long handling times if the energetic contents of the stomach had not reached 450 J. Calculations were made of how many of each millimetre prey size group would satisfy the 450 J demand and how long the estimated number would take to handle. This showed that the best option is to consume 5‐mm prey if given the choice.
The effects of mass removal on the roach Rutilus rutilus (L.) stock of Lake Vesijärvi estimated with VPA within one season
Authors: Peltonen H. , Horppila J.
Published: January 2006

The effects of mass removal on a roach stock was estimated with a virtual population analysis (VPA) within one season. High F/M ratio justifies the use of VPA in short intervals. The high ratio made it possible to obtain robust estimates because the terminal fishing mortality and the estimate of natural mortality had a negligible effect on the stock‐size estimates. Trawling effectively removed almost all the roach from the trawling area. The instantaneous rate of fishing mortality reached values greater than 6.0 during the season in some age‐groups. The estimated stock size was identical with weekly and monthly steps. The biomass of the stock was about 90 kg ha in May before the trawling was started. The results indicate that VPA is a convenient stock assessment method in biomanipulation projects especially if the population cannot avoid fishing by using refuges.