bluuebunny/crossref_metadata_2025 huggingface dataset:
Cadmium exposure of rainbow trout, Salmo gairdneri Richardson: effects on immune functions
Authors: Thuvander A.
Published: January 2006

Differential leucocyte counts, phagocytosis, humoral antibody response and the in vitro blasto‐genetic response to mitogens (lipopolysaccharide and Concanavalin A) and to an antigen (Vibrio anguillarum) were studied in rainbow trout exposed to 0,0.7 or 3.6 μg Cd 1−1 for 12 weeks.

Although the fish did not exhibit any clinical or histological changes, cadmium exposure was found to affect two of the immune parameters measured. The cellular response of fish immunized with V. anguillarum to the homologous antigen was significantly lower for splenocytes obtained from fish exposed to cadmium for 9 weeks (3.6 μg Cd 1−1 group) than for splenocytes obtained from non‐exposed fish. Conversely, the humoral antibody response to V. anguillarum O‐antigen was higher in the 3.6 μg Cd 1−1 group than in the non‐exposed group. Protective immunity of fish vaccinated against V. anguillarum was equally as good in the cadmium‐exposed group as in the non‐exposed group. No cadmium‐induced changes in differential leucocyte counts or in the proportions of phagocytic cells were observed.
Post‐glacial colonization of brown trout, Salmo trutta L.: Ldh‐5 as a phylogeographic marker locus
Authors: Hamilton K. E. , Ferguson A. , Taggart J. B. , Tómasson T. , Walker A. , Fahy E.
Published: January 2006

The Ldh‐5 locus, which codes for the eye‐specific lactate dehydrogenase in brown trout, has been shown to be polymorphic for two codominant alleles, Ldh‐5 (100) and Ldh‐5 (90). The Ldh‐5 (100) allele is present in 11 other salmonid species and is therefore likely to be the ancestral one, whereas the unique brown trout Ldh‐5 (90) allele would seem to be the result of a mutation in that lineage. The Ldh‐5 (90) allele appears to have arisen in north‐west Europe during or after the last glaciation, with allelic substitution taking place under the action of natural selection. The Ldh‐5 (90) allele can be used as a phylogeographic marker to trace the post‐glacial spread of the populations possessing it. Examination of the current distribution of the two alleles suggests that, in the formerly glaciated area of north‐west Europe, there have been two post‐glacial colonizations by brown trout. The first was by an ‘ancestral’ race fixed for the Ldh‐5(100) allele. This was later replaced by, or introgressed with, the later‐arriving ‘modern’ race characterized by the Ldh‐5 (90) allele, except where physical barriers prevented colonization by this latter form. Artificial stocking has resulted in ‘genetic contamination’ of many populations of the ancestral race and there is an urgent need to conserve the remaining pristine populations, especially in view of the likely genetic propensity for longevity and ultimate large size exhibited by this race.
Long‐term changes in strontium‐90 concentrations within a freshwater predator‐prey system
Authors: Beddington J. R. , Mills C. A. , Beards F. , Minski M. J. , Bell J. N. B.
Published: January 2006

It proved possible to determine the levels of Sr‐90 in the opercular bones of individual pike, Esox Iucius, and in pooled samples of bones from perch, Perca fluviatilis. Results from both species from Windermere demonstrated that Sr‐90 levels rose from below the detection limits in the 1940s to a peak in the 1960s, followed by a decline in the subsequent two decades. This decline was slower than would have been expected from the decline in northern hemisphere Sr‐90 fallout, indicating the likelihood of recycling within the environment. Sr‐90 levels were consistently lower in pike than in perch, their main prey fish. Thus, there is no concentration of Sr‐90 up this part of the aquatic food chain. Tracking Sr‐90 in bones taken in successive years from ages 3 to 8 for a single cohort of pike showed that the quantity of Sr‐90 was closely related to opercular bone (and hence fish) weight. No significant increase in Sr‐90 concentration in the bone with increasing age was demonstrated.
Profiles of enzyme activity in larvae of two cyprinid species with contrasting life styles (Cyprinidae; Teleostei)
Authors: Hlnterleitner S. , Thurner‐Flür J. , Wieser W. , El‐Flky N.
Published: January 2006

Growth and the development of gills, muscle fibres and 10 enzymes serving different metabolic functions were studied in larvae of Rutilus rutilus (L.) and Chalcalburnus chalcoides (Agassiz, 1832). R. rutilus starts swimming and feeding one to three days after hatching, whereas in C. chalcoides this process is delayed by about 10 days. This difference in behaviour is reflected in the time‐course of growth, the differentiation of the red muscle fibres and the activity of the enzymes of aerobic energy metabolism. On the other hand, the activity of the enzymes of anaerobic energy metabolism increases steadily throughout the period of observation (up to 60 days post‐hatch), this trend being more pronounced in C. chalcoides than in R. rutilus. A weight‐independent and a weight‐dependent phase of development can be distinguished in the enzymes of aerobic energy metabolism. It is suggested that, in accord with previous findings, the early phase of locomotor activity of cyprinid larvae is fuelled mainly by aerobic processes, and that the central muscle mass of the larvae is more aerobic than the white muscle fibres of the adults. The delayed development of aerobic enzyme activity in C. chalcoides is compensated by the accelerated development of anaerobic enzyme activity, particularly of creatine kinase and lactate dehydrogenase. This difference between the two species studied suggests differences in the metabolic basis of burst activity.
In vitro evidence for the ionoregulatory role of rainbow trout mucus in acid, acid/aluminium and zinc toxicity
Authors: Handy R. D. , Eddy F. B. , Romain G.
Published: January 2006

Rainbow trout body mucus dialysed with acidified distilled water at pH 7,5 and 3 experienced ion depletion which was greatest at pH 3 and minimal between pH 7 and 5. Mucus Na+ loss is exacerbated in the presence of 1 mg I−1 aluminium as A12(SO4), at pH 5 and 7. Al2(SO4), causes greater depletion of Na+ from mucus than A1C13. A lethal level of zinc (2 mg 1−1) does not deplete mucus Na− or K+, unlike a lethal level of aluminium (1 mg 1−1) at pH 7. The results are discussed in terms of the ionoregulatory role of mucus in heavy metal and acid toxicity.
Big is better: the importance of size for reproductive success in male Pomatoschistus minutus (Pallas) (Pisces, Gobiidae)
Authors: Magnhagen C. , Kvarnemo L.
Published: January 2006

The sand goby, Pomatoschistus minutus, was used in aquarium experiments to study the importance of body size for the ability of males to gain access to nest sites and mates. When several male and female P. minutus were allowed to reproduce together, on average, half of the males built nests, and half of those males obtained eggs in their nests. Males with nests were significantly larger than males without nests, and nests with eggs belonged to males larger than the males with empty nests. In another experiment, when two males were competing for one nest, the largest male occupied the nest when both fish were put into the aquarium simultaneously. However, when the smaller male had been allowed to establish a nest before the larger male was introduced, the small male could usually retain the nest. Males with a body length < 50 mm did not build nests at all in the early part of the breeding season. In female choice experiments, no preference for larger males was found. Thus, male‐male competition for nest sites and behavioural differences between different sized males seem to be the main factors influencing the non‐random mating success in male P. minutus.
The effects of temperature, pH and water hardness on winter starvation of young‐of‐the‐year smallmouth bass, Micropterus dolomieui Lacepede
Authors: Shuter B. J. , Ihssen P. E. , Wales D. L. , Snucins E. J.
Published: January 2006

Year‐class strength in northern populations of smallmouth bass is strongly influenced by winter starvation of young‐of‐the‐year. We examined starvation among young bass under both winter and summer light and temperature conditions. During starvation, body condition declines to a specific level and then the fish dies. Body condition at death is a well defined function of body size that remains relatively constant over a wide range of environmental conditions. Starvation rate varies systematically with body size, temperature, pH and water hardness. Available stored energy increases more rapidly with body size than starvation rate. Therefore, lifetime under starvation conditions tends to increase with increasing body size. The Q10 for starvation rate over the temperature range 2.5‐8° C is 2.2. Starvation rate increases as pH declines from 7.0‐4.9: the rate at pH 4.9 is ∼ 1.25 times the rate at pH 7 Starvation rate decreases as Ca concentration increases from 1 mgl−1 to 80mgl−1: the rate at 80 mg Ca 1−1 is ∼0.80 times the rate at 1 mgl−1.
Identification of the Lake Malawi Oreochromis (Nyasalapia) spp. using multivariate morphometric techniques
Authors: Turner G. F. , Pitcher T. J. , Grimm A. S.
Published: January 2006

With the aim of reliably distinguishing these commercially important species on the basis of external characteristics alone, morphometric techniques were employed on a sample of the four species of Oreochromis (Nyasalapia) described from Lake Malawi: O. karongae, O. lidole, O. saka and O. squamipinnis. Univariate analysis of variance on the ratios of 23 variables to standard length indicated many differences among all species, but there was considerable individual variation, and consequent overlap. Residuals from a regression of each variable on length were employed for multivariate analysis. Cluster analysis on the means of the residuals was used to construct a phenogram which formed the basis for denning a series of dichotomous discriminant analyses. In each discriminant analysis, variables were successively eliminated in the reverse order of the magnitude of their correlation with the discriminant function. The combination of variables producing 95% accuracy of classification was selected, and the discriminant function equations for each step calculated. Some further variables were eliminated by checking for redundancy through analysis of correlations. The resulting equations enable O. karongae to be separated using eight measurements, O. lidole using 10, and O. saka and O. squamipinnis to be distinguished by a combination of 13 measurements.
Individual variability in the epidermis of prespawning inshore winter flounder, Pseudopleuronectes americanus
Authors: Burton D. , Burton M. P. M.
Published: January 2006

Prespawning winter flounder, Pseudopleuronectes americanus Walbaum, manifest epidermal thickening as a secondary sexual characteristic, but with considerable individual variability. The correlation between epidermal thickness and fish size in post‐spawned flounder is less apparent in prespawning flounders due to factors associated with sexual maturation. Thus, epidermal thickness in individual prespawning flounder displays significant correlation with gonadosomatic index and. in females, with the degree of final maturation of vitellogenic oocytes. However, both epidermal thickness and gonadosomatic index of individual flounders also display significant correlation with condition factor. It is proposed that body size and condition factor represent important primary physiological determinants influencing individual variability in seasonal epidermal thickness, and that factors associated with sexual maturation represent a secondary physiological determinant.
The selection of suitable indices for the measurement and analysis of fish condition
Authors: Bolger T. , Connolly P. L.
Published: January 2006

A survey of the studies published in two leading fisheries journals revealed that the analysis and measurement of condition, based on length‐weight data, has been performed using a wide variety of indices and statistical procedures. Eight forms of index were identified which can be categorized into those which measure the condition of individual fish, i.e. condition factors‘, and those which measure the condition of subpopulations as a whole, i.e. regressions of log, 10 weight on log, 10 length and the parameters of such regressions. Analysis of a test data set indicated that both the form of index and properties of the data set size can dictate the patterns of condition observed. The various indices were reviewed in terms of appropriateness, simplicity and statistical correctness. It was concluded that an index should be selected only after a detailed examination of both the underlying assumptions of the index and the properties of the data set.
Behavioural responses of salmonid fry to low amino acid concentrations
Authors: Mearns K. J.
Published: January 2006

The behaviour of start feed brown trout, Salmo trutla, and Atlantic salmon, Salmo salar, fry was observed in response to 5, 50 and 500 nM concentrations of L‐alanine, L‐proline, L‐arginine and glycine. In addition, salmon fry were tested with dilute concentrations of shrimp extract. Five behaviour patterns (snap, yawn, dart, twitch movements and active swimming) were shown in response to all amino acid and shrimp extract concentrations. Snapping, darting and active swimming increased in both species as a function of amino acid concentration, and in the salmon fry as a function of increasing shrimp extract concentration. Otherwise, the salmon showed twice as much yawning and more twitch movements than the trout, but the trout showed more active swimming than the salmon. Both species showed an increase in activity in response to L‐proline at 5 nM, and the salmon also responded to L‐arginine and glycine at this concentration. Both species first responded to L‐alanine at 50 nM, but the trout did not respond to glycine until a concentration of 500 nM was presented. The salmon fry responded to shrimp extract at c. 10 14g l‐1, but no differences in their activity were observed in response to concentrations between c. 10‐12 and 10‐6gl‐1.
An isozyme study of the natural cyprinid hybrid Alburnus alburnus×Rutilus rubilio in Greece
Authors: Berrebi P. , Dupont F. , Cattaneo‐Berrebi G. , Crivelli† A. J.
Published: January 2006

The intergeneric hybridization of two Greek cyprinids reported by Crivelli & Dupont (1987) using morphological criteria is described here on the basis of 24 enzyme loci. This hybridization was rarely found to go beyond the first generation (backcrosses: 0–2 per 1000). Various statistical coefficients indicate that the hybrids correspond to an entity that is exactly halfway between the two parent species
Death rate, recapture frequency and changes in size of tagged eels
Authors: Dekker W.
Published: January 2006

From 475 eels individually marked with floy tags, of which 180 had an additional spot of alcian blue, 142 tags were recovered during a 2‐year release‐recapture programme, but alcian blue spots were not detected. The marked population declined by c. 95% per year (either through death or tag loss); tagged eels did not grow but lost weight; no trap avoidance could be detected. It is concluded that these tagged eels in poor condition did not suffer from winter mortality, and that during summer they moved around very actively.
Enzyme activities in the blood plasma of grayling, Thymallus thymallus (Linn.), in the breeding season
Authors: Hlavová V.
Published: January 2006

Activities of alanine aminotransferase, aspartate aminotransferase, glutamate dehydrogenase and creatine kinase were determined in the blood plasma of grayling, Thymallus thymallus, in the pre‐spawning, spawning and post‐spawning periods. Enzyme activities increased to a maximum in the spawning period and then successively decreased, after spawning, to values close to the initial ones. Only in the case of aspartate aminotransferase did the increased activity level persist after spawning. The temporary but large increase in enzyme activity levels in the plasma of grayling appeared to be a natural and physiological phenomenon accompanying the spawning process.
Surface absorption of aluminium by gill tissue and body mucus of rainbow trout, Salmo gairdneri, at the onset of episodic exposure
Authors: Handy R. D. , Eddy F. B.
Published: January 2006

Rainbow trout were exposed to an episode of artificial soft water at pH 5.4 containing 0.95 mg 1 ‐1 of aluminium for 1 h and gill, skin, body mucus and blood aluminium concentrations were determined. Skin and blood showed no significant increase in aluminium content, whereas whole gill tissue and body mucus showed significant increases. The results are discussed in terms of the gill and body mucus being major sites of aluminium absorption, and a tentative mechanism for aluminium absorption is discussed.
Leucocytes and leucopoietic capacity in thermally acclimated goldfish, Carassim auratus L.
Authors: Dunn S. E. , Murad A. , Houston A. H.
Published: January 2006

Goldfish acclimated for minimum periods of 3 weeks to 5, 15, 25 and 35°C exhibited significant changes in circulating leucocyte types and numbers. Total leucocyte, lymphocyte, neutrophil and eosinophil levels increased significantly between 5 and 25°C, as did their relative contributions to the total leucocyte population. Thrombocyte and blast cell counts increased non‐significantly, while variations in monocyte and basophil levels were inconsistent. Between 25 and 35° C, lymphocyte numbers fell sharply, while neutrophil concentrations remained essentially constant as did those of thrombocytes. Response to an intraperitoneally administered mitogen, phytohaemagglutinin, was delayed and reduced at 5° C compared with 25° C.
Immunological importance of the second gut segment of carp. I. Uptake and processing of antigens by epithelial cells and macrophages
Authors: Rombout J. H. W. M. , van den Berg A. A.
Published: January 2006

Uptake and transport of soluble (ferritin) and particulate (Vibrio anguillarum) antigen from intestinal lumen to mucosal macrophages was studied using immunocytochemical and electron‐microscopical techniques. Both antigens were taken up by epithelial cells of the second gut segment, reached the supranuclear vacuoles and were finally transported to large intraepithelial macrophages. In contrast with particulate antigen, antigenic determinants of ferritin were demonstrated in the basal part of the epithelium and appeared to be released at the mucosal site.

After anal intubation many small macrophages penetrated the intestinal epithelium, took up antigen and after 24 h disappeared again from the intestinal mucosa. This feature was antigen independent and also occurred after anal PBS‐intubation. The larger, less mobile macrophages stayed in the intestinal epithelium and finally exposed antigenic determinants (of both antigens) at their outer surface, suggesting an antigen‐presenting function. Whether these large macrophages can induce a local or mucosal immune response and whether the smaller mobile macrophages are involved in a systemic response is discussed.
Diel and seasonal locomotor activity patterns in Arctic charr, Salvelinm alpinus (L.)
Authors: Linnér J. , Brännäs E. , Wiklund B.‐S. , Lundqvist H.
Published: January 2006

One‐year‐old Arctic charr, Sulvelinus alpinus (L.), of the Hornavan strain were tested from February 1985 to January 1986 in an attempt to get an increased understanding of the annual rheotactic behaviour as well as the die1 and seasonal locomotor activity pattern. An annular stream tank equipped with photocells was used to measure the direction of swimming movements as well as the number of passings. From February to late May the locomotor activity was low but increased in July and peaked in September. After November the locomotor activity was again at low winter levels. During the activity peak from July to November the majority ofall movements was directed against the current while no preference for direction was noted during the rest of the year. The high level of swimming movements directed against the current in late summer and autumn may be related to an innate habitat change. From February until June, the charr exhibited a bimodal diurnal activity pattern. In July activity was evenly spread over the whole 24‐ hour period and in August and September activity was again mainly diurnal with a bimodal pattern. In October and November the activity was mainly nocturnal and in December and January activity was concentrated in the short light period. Both annual and die1 activity are discussed in relation to earlier findings in general locomotor activity in Arctic charr and other salmonids.
Biology of carpione, Salmo carpio L., an endemic species of Lake Garda (Italy)
Authors: Melotto S. , Alessio G.
Published: January 2006

Biological and ecological aspects of Lake Garda carpione, Salmo carpio L., are reported. This study reports lower catches and it is suggested that fewer carpione are now in this lake. Opercula and scales have been used for ageing fish and determining the growth rates. Life expectancy does not exceed five winters. Males became sexually active at 2 years (=winters) of age and females at 3 years of age, however, full spawning capability is achieved only in the following year. Our data confirm that carpione have two spawning seasons: winter (a long period) and summer (a shorter one). Carpione are not exclusively planktivorous but adapt their feeding habits to the environment and change the manner and time of their feeding.
Interpopulation variation in reproductive traits of anadromous female brown trout, Salmo trutta L.
Authors: L'Abee‐Lund J. H. , Hindar K.
Published: January 2006

We studied reproductive traits in nine anadromous brown trout, Salmo trutta L., populations in seven Norwegian rivers. Within populations we found a positive significant correlation between fish length and fecundity in all populations, and between fish length and egg diameter in five populations. There were significant differences in these relationships between populations from different rivers, and between populations from different locations within rivers. When adjusted for variation in fish length, mean fecundity and mean egg diameter showed a negative significant correlation among populations. The ratio of gonadal weight to somatic weight (gonadosomatic index) varied significantly among populations but was not associated with variation in fish length. Comparatively few large eggs were found in brown trout populations co‐existing with several other fish species.
Patterns of parasitic infections of fishes in a water body with constant temperature
Authors: Bauer O. N. , Karimov S. B.
Published: January 2006

Patterns of parasitic infections of Schizothorax intermedius in two water bodies of North Tadjikistan (Central Asia), one with constant temperature during the whole year, the other with normal annual seasonal range of temperature fluctuations, have been studied. It has been shown that in the first water body fluctuations in occurrence of the parasites are insignificant and are not under the influence of water temperature.
Intraspecific genetic differentiation of Leporinus friderici (Anostomidae, Pisces) in French Guiana and Brazil: a genetic approach to the refuge theory
Authors: Renno J.‐F. , Berreb P. , Boujard T. , Guyomard R.
Published: January 2006

A genetic study was carried out on a neotropical fish species to illustrate the refuge theory, whose main principles are summarized. The geographical structure of the anostomid species Leporinus friderici was analysed in French Guiana and Brazil by horizontal starch gel electrophoresis. Fifteen enzymatic systems corresponding to 21 loci were studied, revealing the following particularities: (1) specimens of fish from six independent coastal rivers of French Guiana form two groups geographically situated on either side of the Kourou River; (2) two alleles can serve as geographic markers, Ldh2(l30) showing an affinity between the populations in eastern French Guiana and Brazil, and Me 1(300) being specific to the west.

These observations are probably related to the refuges that were formed in the Quaternary in South America, especially on the Guiana Shield. We consider that the populations of French Guiana are separated into two groups at the boundary between the two migratory flows, one arising in the west from the refuge of the Guiana Shield and the other in the east from a nearby undetermined Amazonian refuge.
Effect of actinomycin‐D on gill Na+‐K+ ATPase of juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum)
Authors: Beckman B. R. , Zaugg W. S.
Published: January 2006

Actinomycin‐D reduced gill Na+‐K+ ATPase activity of chinook salmon Oncorhynchus ishawytswha (Walbaum), smolts and saltwater‐adapted juveniles but had no significant effect on the enzyme activity of parr in fresh water. The similarity in response suggests that even though smolts are found in fresh water, their enzyme system is more characteristic of saltwater‐adapted juveniles than freshwater‐dwelling parr. A greater reduction in enzyme activity was found when fish were treated with actinomycin‐D in salt water than in fresh water, suggesting that the enzyme degradation rate wasgreater in salt water than in fresh water.
Antigen‐induced blastogenesis of salmon, Salmo saluv L., head kidney leucocytes to modified Aeromonas salmonicida antigens: a preliminary evaluation method for potential vaccine antigens
Authors: Tatner M. F.
Published: January 2006

Various Aeromonas salmonicida antigen preparations were tested in an antigen‐induced blasto‐genesis assay on the kidney leucocytes of Atlantic salmon. The ECP antigens that had been particularized onto polystyrene beads were the most effective in control fish, and this was further enhanced in fish thymectomized 1 week prior to the assay. The use of this assay for screening potential vaccine antigens is discussed.
Recovery of an extremely proteolytic form of Serratia liquefaciens as a pathogen of Atlantic salmon, Salmo solar, in Scotland
Authors: McIntosh D. , Austin B.
Published: January 2006

During 1988, heavy mortalities were observed in three discrete populations of Atlantic salmon in Scotland. From moribund and dead animals, dense pure culture growth of an extremely proteolytic bacterium was recovered, which did not correspond to the description of any of the validly described fish pathogens. The organism, which was initially considered to have characteristics intermediate between Aeromonas veronii and Serratia liquefaciens, was eventually equated with the latter, i.e. S. liquefaciens, after seeking the advice of the Centers for Disease Control, Atlanta, U.S.A. The pathogenicity mechanism appears to involve the production of proteolytic extracellular products.
Distribution of aldehyde dehydrogenase and alcohol dehydrogenase in summer‐acclimatized crucian carp, Carassius carassius L.
Authors: Nilsson G. E.
Published: January 2006

The tissue distribution of aldehyde dehydrogenase (ALDH) and alcohol dehydrogenase (ADH) in summer‐acclimatized crucian carp showed almost the same exceptional pattern as previously found in winter‐acclimatized specimens. There was a nearly complete spatial separation of ALDH and ADH; in other vertebrates these enzymes occur together. This exceptional enzyme distribution is probably an adaptation to the extraordinary ability of Carassius to produce ethanol as the major metabolic end product during anoxia. Since the crucian carp is less likely to encounter anoxia during the summer, the present results suggest that the crucian carp is unable to switch over to a ‘normal’ ALDH and ADH distribution in the summer. However, it is also possible that there is an advantage for the summer‐acclimatized crucian carp in keeping ALDH and ADH separate, because of occasional anoxic periods.
Otolith and somatic growth rates in Atlantic salmon parr, Salmo salar L: evidence against coupling
Authors: Wright P. J. , Metcalfe N. B. , Thorpe J. E.
Published: January 2006

It is often assumed that otolith growth is in some way dependent on somatic growth (i.e. that the two processes are coupled). We examined the relationships between sagitta radius and fork length in 0+ Atlantic salmon parr that would subsequently smolt aged 1 + (UMG fish) or 2+ (LMG fish). Repeated measurements of fork lengths of individually marked parr, taken over a 211‐day period from first feeding, were compared to sagitta radii on the same measuring dates (obtained by analysis of daily increments). The results showed that there was a linear relationship between fork length and otolith radius in UMG parr. However, this was not true for LMG parr. These fish enter a state of natural anorexia in their first autumn (despite excess food), but their otoliths continued to grow at the same rate despite the virtual cessation of somatic growth; they had therefore developed disproportionately large otoliths by the end of the study period. The relative growth rates of soma and otoliths first changed in LMG fish in late July/early August; this is the most precise estimate yet obtained of the timing of divergence in the developmental pathways of UMG and LMG parr. The rate of sagitta accretion was consistently lower in LMG parr, possibly indicating a lower metabolic rate in these fish. The results are discussed in relation to previous theories of the relationship between otolith and somatic growth.
Distribution of fingerling brook trout, Salvelinus fontinalis (Mitchill), in dissolved oxygen concentration gradients
Authors: Spoor W. A.
Published: January 2006

A self‐recording linear gradient tank and procedures are described in which individual brook trout fingerlings unstressed by recent transfer, unaccustomed surroundings or the presence of an observer could move freely in 16 oxygen concentration gradients within the limits of 1 and 8.9 mg O21−1. They avoided oxygen concentrations below 4 mg 1−1 most of the time and preferred 5 mg 1−1 or higher more than half the time, which supports the field‐derived belief that fish avoid oxygen concentrations below 5 mg l−1 in the natural environment if they can.
Interactions between natural and farmed fish populations: information from genetic markers
Authors: Skaala Ø. , Dahle G. , Jørstad K. E. , Nævdal G.
Published: January 2006

Studies on genetic changes in farmed fish populations are reviewed, and the potential interactions between wild and farm escapee, and between wild and stocked, fish populations are discussed. Examples of the application of genetic markers in studies concerning survival and reproduction of stocked fish, and genetic and ecological interactions between stocks, are given for brook trout, Salvelinus fontinalis, brown trout, Salmo trutta, rainbow trout, Salmo gairdneri, cod, Gadus morhua, Guadalupe bass, Micropterus treculi, walleye, Stizostedion vitreum vitreum and chum salmon, Oncorhynchus keta. The various studies produced different results. Evidence for successful reproduction and genetic interactions between released and wild stocks have been found in a few cases. Stocked genetic material sometimes had a lower reproductive success than wild material. In one case the transplanted genetic material failed to acclimatize, and was apparently lost from the genepool in two generations. Investigations on the genetic and ecological interactions between wild and farmed populations are of great importance to the preservation of wild populations and their genetic resources.
Maximum daily ration of juvenile fish fed on living natural zooplankton
Authors: Marmulla G. , Rösch R.
Published: January 2006

Juveniles of five species of cyprinids of body length 15–90 mm as well as juvenile perch, Perca fluviatilis L., were fed on living natural zooplankton over periods of 2 or 3 days. For all species the correlation of the daily ration (% body weight) with body weight showed a maximum curve. The maximum was reached at a body weight (wet weight) of 0.6 g for Leuciscus leuciscus (L.) and 0.1 g for a group consisting of varying numbers of Rutilus rutilus (L.), Abramis brama (L.) and Alburnus alburnus (L.). For L. leuciscus, the maximum was 220% body weight (wet weight), corresponding to 40% on a dry weight basis. For the mixed species group the maximum was about 500% (wet weight) and about 140% on a dry weight basis. The highest daily ration coincided with the occurrence of the spring bloom of zooplankton.
The fish community structure in Tjeukemeer in relation to fishery and habitat utilization
Authors: Lammens E. H. R. R. , van Densen W. L. T. , Knijn R.
Published: January 2006

The fish community in Tjeukemeer was monitored from 1971 to 1988 by trawling, and during the summer of 1988 the distribution of the more abundant species was determined in relation to size and location. Bream, pikeperch and smelt were the most dominant fishes, whereas roach, white bream, perch and ruffe comprised <10% of the total catches. After the termination in 1977 of the intensive gillnet fishery both pikeperch >50 cm and bream >30 cm increased in biomass, but roach >15 cm and perch >15 cm virtually disappeared and pikeperch <50 cm substantially decreased. Only smelt, ruffe, white bream and bream <30 cm hardly changed in biomass. Bream, pikeperch, perch and smelt were restricted to the open water zone, but roach <15 cm and 0 + bream were confined to the littoral zone. White bream and ruffe did not show a distinct habitat preference. Because the recruitment of smelt is largely dependent on immigration from the IJsselmeer, a feed‐back between the smelt and pikeperch population is lacking. Because the carrying capacity of the pikeperch population is mainly determined by smelt, the other fish <15 cm are very vulnerable to predation when the smelt population is consumed, before a new year‐class of smelt is recruited, or when the smelt fails to recruit. The vulnerability to predation of the different species and their feeding habits are discussed in relation to their distribution.
Spatial and temporal dispersion patterns of golden perch, Macquaria ambigua, larvae in an artificial floodplain environment
Authors: Gehrke Peter C.
Published: January 2006

Golden perch larvae were stocked into a pond and inundated floodplain system in south‐eastem Australia to determine movement patterns of the larvae onto and off the floodplain area. A total of 428 larvae were caught moving from the floodplain into the pond whereas only 18 were collected moving in the reverse direction. Thirty one larvae were caught at open water sites in the pond and floodplain, but only three were collected from sites on the floodplain which provided shade, timber or water flow. Transect samples from the pond also yielded more larvae than samples from floodplain transects, indicating a distinct spatial dispersion pattern in favour of the pond.

Spatial dispersion patterns of golden perch larvae appear to correspond with gradients in water quality between the pond and floodplain habitats. Stratification occurred in the pond but did not develop on the floodplain. Water on the floodplain was cooler, harder and contained less oxygen than surface water from the pond. Die1 oscillations occurred in water temperature, pH, dissolved oxygen, carbon dioxide and acidity, but there was no significant corresponding pattern in the distribution of larvae.

Dispersion of golden perch larvae between pond and floodplain habitats is not random, and may be actively influenced by local‐scale variations in water quality.
Diel changes of larval drift among amphidromous gobies in Japan, especially Rhinogobius brunneus
Authors: Iguchi K. , Mizuno N.
Published: January 2006

Larvae of amphidromous gobies migrate to the sea as passive drift. In order to identify the diel drift pattern (DDP) of each species, we conducted 24 hour collections in different sections ofthree rivers. The DDPs ofdifferent species at each sampling station were almost identical, but the DDP of each species varied among stations, depending on the topographical features of water‐courses. Downstream migration occurred throughout the day in steep water‐courses while it was nocturnal with a peak in number soon after sunset in gentle gradients in the plain and was also nocturnal with a small amount of day time drifting between the two gradients. It is suggested that the larvae drifting from the upper parts of the river in daytime halted their migration in a pool with low flow rate until twilight.
Reproduction and development of two angel sharks, Squatina squatina and S. oculata (Pisces: Squatinidae), off Tunisian coasts: semi‐delayed vitellogenesis, lack of egg capsules, and lecithotrophy
Authors: Capapé C. , Quignard J. P. , Mellinger J.
Published: January 2006

Distribution, sexual maturity, fecundity, genital asymmetry, cyclic vitellogenesis and gestation are described in the angel sharks Squatina squatina (L., 1758) and S. oculata Bonaparte, I840 from Tunisian waters. With embryonic nutrition being purely lecithotrophic, lack of egg capsules, block of oocyte growth at the beginning of gestation, and inability to ovulate soon after parturition, Squatinidae can be compared to Torpedinidae and to Centroscymnus (Squalidae), except that their vitellogenesis starts again at mid‐gestation. This new, special feature has been termed ‘semi‐delayed vitellogenesis’ with regard to the delayed vitellogenesis of Torpedinidae and
Centroscymnus.
A search for introgressive hybridization in the rudd, Scardinius erythrophthalmus (L.), and the roach, Rutilus rutilus (L.)
Authors: Thompson D. , Iliadou K.
Published: January 2006

Rudd, roach and their hybrids from an interbreeding population at Norwich were examined electrophoretically for seven enzymes; an examination of pharyngeal teeth supplemented the data. The rudd were compared to rudd from Lake Trawsfynydd, Wales, a lake free from roach. No differences were observed between the rudd from the two localities and no evidence was found of introgression within the fish from Norwich.
Arteriosclerosis in steelhead trout, Oncorhynchus mykiss (Walbaum): a developmental analysis
Authors: Kubasch A. , Rourke A. W.
Published: January 2006

Arteriosclerosis in Oncorhynchur mykiss has been examined histologically in parr, smolts, spawning adults and post‐spawning adults captured during downstream migration. All stages of fish from the Clearwater River in Idaho are characterized by the presence of lesions in the main vessel on the bulbus arteriosus. The incidence is lowest in parr, increases significantly in smolts, and is present in 100% of spawning fish. Regression of lesions was not observed in either hatchery or wild fish after spawning.
The population biology of tench, Tinea tinea (L.), in two gravel pit lakes
Authors: Wright R. M. , Giles N.
Published: January 2006

The populations of tench from two gravel pit lakes of contrasting habitat type were studied. The population density of tench from St Peter's Lake, which has abundant aquatic vegetation was 176 individuals ha−1 (102.2 kg ha−1) compared to 0.3 individuals ha−1 (0.5 kg ha−1) in the Main Lake which has very little aquatic vegetation. The results of ageing tench by scales, opercular bones and otoliths were compared; all three structures gave similar results up to 9 years of age, but thereafter there were difficulties in ageing using scales and care was needed in counting annuli. The oldest tench caught was 15 years old. Growth of male and female tench was similar and fitted the von Bertalanffy model; for female tench L∞= 573 mm, K=0.122 and for male tench L∞= 586 mm, K=0.114. Recruitment was variable and strong year classes occurred in years with warm summers.
Genetic comparisons of New and Old World coregonid fishes*
Authors: Bodaly R. A. , Vuorinen J. , Ward R. D. , Luczynski M. , Reist J. D.
Published: January 2006

The genetic relationships among New and Old World coregonid fishes were studied by electrophoresis. The genetic composition of 60 populations, representing perhaps nine commonly recognized species of Coregonus and Stenodus from Europe and North America was determined for 37 genetic loci. Six distinct genetic groups were evident. The first contained only populations of the inconnu, Stenodus leucichthys (Güldenstadt). The Nei genetic distance between Stenodus and Coregonus was 0.305, a relatively small value as compared to other salmonid inter‐generic comparisons. The second genetic grouping contained the Arctic cisco, C. autumnalis (Pallas), the N. American lake cisco, C. artedii Lesueur, and the Irish pollan, C. autumnalis pollan Thompson. These three taxa appear to be conspecific on the basis of genetic distances. The third genetic grouping contained the European whitefish, C. lavaretus (L.), and the N. American lake whitefish, C. clupeaformis (Mitchill). European and lake whitefish may be conspecific. Lake whitefish from northwestern N. America were more closely related to European whitefish (genetic distance 0.038) than to lake whitefish from central N. America (genetic distance 0.098). The fourth group contained the broad whitefish, C. nasus (Pallas), which is perhaps more closely related to the European/lake whitefish groups than other coregonids. The fifth genetic grouping contained only the Asian endemic, C. peled (Gmelin), and the sixth contained the least cisco, C. sardinella Valenciennes, and vendace, C. albula (L.), which also appear to be conspecific. The widespread genetic groupings obtained for ciscoes indicate that they do not constitute a single closely related group within the genus Coregonus.
The effect of androgen treatment on the epidermis of post‐spawned winter flounder, Pseudopleuronectes americanus (Walbaum)
Authors: Burton D. , Everard B. A.
Published: January 2006

The effect of androgen treatment on the thin epidermis of post‐spawned winter flounder, Pseudopleuronectes americanus (Walbaum), freshly collected from an inshore population was investigated. Over the duration of the experiment, control flounders displayed epidermal thickening and increased goblet cell frequencies associated with captivity in this species. Treatment of males with 11‐ketotestosterone induced significantly more differential thickening of the blindside epidermis. Compared with the controls testosterone treatment did not induce additional thickening of male epidermis, but it did increase differential thickening on the blind side of females.
Age, growth and reproduction of the greenback mullet, Liza subviridis (Valenciennes), in an estuary in Southern Iraq
Authors: Al‐Daham N. K. , Wahab N. K.
Published: January 2006

Age, growth, length‐weight relationship, sex ratio, stages of maturity and fecundity of the greenback mullet in Shatt Al‐Basrah Canal, an estuary in Southern Iraq, were studied from February 1985 to January 1986. Age and growth determinations were made from scales from 538 fish ranging from 145 to 310 mm total length. Females (age groups I to VI) were slightly longer than males (age groups I to IV) and their growth, analysed by length‐weight relationship, followed very closely the cubic‐law for isometric growth, but males grew more slowly. The annual average male: female sex ratio was 1.0: 1.4. Monthly examinations of stages of maturity produced abundant gravid fish in February. The maximum values for the gonadosomatic index were obtained in February and March. The smallest mature male and female were respectively 137 and 142mm long. The fecundity ranged between 133 224–295 065 for fish ranging from 182 to 243 mm total length. Although eggs or newly hatched larvae were not found in the Canal, fry 27–40 mm in length were captured from April to June. Spawning appears to occur in the Arabian Gulf, not far from Shatt Al‐Basrah Canal.
Eel, Anguilla anguilla (L.), muscle modifications induced by long‐term exposure to 101 ATA hydrostatic pressure
Authors: Simon B. , Sebert P. , Barthelemy L.
Published: January 2006

Fibre area, water and protein concentrations have been measured in red and white muscle of eels exposed for 1 month to hydrostatic pressure [HP = 101 atmosphere absolute (ATA)]. Comparison of the results with those from control fishes (1 ATA) shows that there is no variation of the measured parameters in red muscle. However, white muscle exhibits a significant decrease (P < 0.01) in protein concentration with a concomitant decrease (P < 0.001) in fibre area. It is proposed that long term exposure to HP = 101 ATA induces metabolic and/or morphological modifications which are dependent on muscle type.
Daily ration of juvenile Coregonus lavaretus (L.) fed on living zooplankton
Authors: Troschel H. J. , Rösch R.
Published: January 2006

Juvenile whitefish, Coregonus lavaretus (L.), wet weight 0.04 to 5.2 g, from Lake Constance were kept at 10, 12 and 16° C water temperature, respectively and fed with living zooplankton. The experimental duration lasted 72 to 120 h. Daily rations were defined as the amount of zooplankton remaining subtracted from the amount of zooplankton added after a 24 h interval. The mortality of the zooplankton was determined in parallel experiments without fish. Relative daily ration (zooplankton weight/fish weight) v. fish weight increased up to a fish dry weight of approximately 0.12 g and then decreased steadily. The maximum daily ration was about 270% of fish body wet weight (wet/wet) corresponding to 75% of body dry weight (dry/dry), respectively. In fishes of a dry weight higher than 0.12 g (wet weight 0.65 g) a significant difference in food intake was found between 12 and 16° C. The specific growth rate ranged from nearly 0 up to 33% per day. No correlation was found between daily ration and specific growth rate.
Population structure, ecological segregation and reproduction in non‐anadromous Arctic charr, Salvelinus alpinus (L), in four unexploited lakes in the Canadian high Arctic
Authors: Parker H. H. , Johnson L.
Published: January 2006

Land‐locked populations of Arctic charr in four lakes on Northern Ellesmere Island (80° N) were found to consist of two distinct sizes: ‘dwarf’ and ‘normal’ charr. Both groups attained sexual maturity but differed in appearance and habitat. The smaller fish, occupying the more marginal habitats, retained their parr‐markings; the larger group had the general characteristics of smolts, being more silvery and without parr‐marks. In their juvenile stages, the charr destined to attain the larger group were indistinguishable from members of the smaller group. Although fish in the larger group were capable of cannibalism, this was rarely observed. In general, the fish in the larger group were older than the smaller ones but great variation in size at a given age resulted in certain age classes containing representatives of both groups. The population structure varied considerably between lakes; a high proportion of ‘normal’ charr correlated well with a high growth rate in the first few years of development. It is postulated that the two groups live in dynamic equilibrium where the advantages of progenesis (retention of juvenile characters by adults) in the smaller type are traded against the larger proportion of the energy resources available to the larger type. The concept of heterochrony in an ecological setting is introduced.
The taxonomy of East African Nile Perch, Lates spp. (Perciformes, Centropomidae)
Authors: Harrison K.
Published: January 2006

The type specimens of Lates albertianus, L. macrophthalmus, L. niloticus rudolfianus and L. niloticus longispinis are contrasted with each other, with riverine L. niloticus niloticus and with a collection of Nile Perch from Lake Victoria. Contrary to current belief L. niloticus niloticus was found to differ both from L. albertianus and from L. niloticus rudolfianus, but no significant difference was found between L. albertianus and L. niloticus rudolfianus. The Lake Victoria collection was found to differ from all other taxa, suggesting that the characters currently used in the taxonomy of Lates are inappropriate for this purpose. It is recommended that a reappraisal of Nile Perch taxonomy be made using more modern techniques and that studies are initiated to discover how characters change during development under differing environmental conditions.