bluuebunny/crossref_metadata_2025 huggingface dataset:
Sequence of gonadal events and oestradiol levels in Sparus aurata (L.) under two photoperiod regimes
Authors: Kadmon G. , Yaron Z. , Gordin H.
Published: January 2006

Individually tagged Sparus aurata were kept in tanks with running sea water (21°± 2°C) during their second and third years of life. Gonads were biopsied and blood was sampled at monthly intervals. Thirteen of 50 fish in the second year and 24 of 35 fish in the third year were phenotypically females. Fish kept under 16L/8D photoperiod from July 1981 to August 1982 did not reach maturation; waves of initial ovarian growth alternated with waves of atresia. When photoperiod was shortened as from August 1982, gonadal development commenced within a month and proceeded at a rate higher than that of the control fish reared under natural photoperiod. Under natural photoperiod oestradiol serum levels (E2) were relatively low during the resting phase, May‐October (108 ± 11 pg ml−1), and during the late vitellogenic phase (502 ± 76 pg ml−1). High levels (1669 ± 312 and 1240 ± 172pg ml−1) occurred during the early vitellogenic and the maturational phases. The high level of E2 during the spawning season of S. aurata is explained by earlier reports indicating a prolonged breeding season with daily release of eggs, and alternating daily surges of E2 and 17α, 20β, dihydroxy‐4‐pregnen‐3‐one, possibly a ‘maturational progestin’ in this fish. In phenotypic males, E2 was highest during early spermatogenic phases (745 ± 142pg ml−1) but was low (155 ± 11 pg ml−1) in males with running sperm.
Walleye, Stizostedion vitreum, and northern pike, Esox lucius, populations in three Alberta lakes
Authors: Craig J. F. , Smiley K.
Published: January 2006

Results are presented from a survey of walleye and northern pike in Ethel, Marie and Wolf Lakes, Alberta conducted May‐September, 1983. Three types of experimental gill net were fished, mainly inshore. Northern pike were abundant in all three lakes but white sucker and yellow perch also were common. Walleye were caught in largest numbers in Wolf Lake. Age and growth of both walleye and northern pike were determined from examination of the opercular bones. The walleye in the three lakes were represented by a few strong year classes but there was no synchronism between the lakes. The strong 1975 year class in Ethel and Wolf Lakes may have been correlated with high spring precipitation and heavy run‐off. Although there were dominant year classes in the northern pike populations (especially the 1979 year class) the variability was not so marked as in the walleye. There were no significant differences between length‐at‐age for year classes of walleye in Ethel and Marie or northern pike in all three lakes. In Wolf Lake the 1978 and 1979 year classes grew faster than in previous years. Walleye and northern pike growth was well described by the von Bertalanffy growth model. Females of both species grew to a greater ultimate length and had a longer lifespan than the males. Fecundity data are presented for walleye from Wolf Lake (log10 absolute fecundity = 0.856 + 2.441 log10 length) and northern pike from Marie Lake (log10 absolute fecundity =−2.671+4.052 log10 length). The stomach contents of both species were examined during May and June. The majority of walleye had empty stomachs. Walleye and northern pike in Ethel and Wolf Lakes fed on a variety of fish and invertebrate species but both fed mainly on fish (in particular whitefish) in Marie Lake. The similarity of diet suggests competition for prey species. A walleye yield to commercial fishermen of c. 0.69 kg ha−1 year−1 in Wolf Lake has made up 8% of the total catch. Since 1970/71 when mesh size of nets was increased, the yield has been reduced to c. 0.30 kg ha−1 year−1. Anglers remove an additional c. 0.48 kg ha−1 year−1 walleye from Wolf Lake. Northern pike yields to commercial fishermen have been c. 2.00 kg ha−1 year−1 in Wolf Lake. Ethel and Marie Lakes have yielded only poor catches of walleye and northern pike. A yield model was used to illustrate that faster‐growing northern pike have higher potential yields than walleye. Walleye produce higher yields in Wolf Lake than in Marie Lake, the reverse being true for northern pike. It is suggested that northern pike could be cropped at a higher rate in Marie and Wolf Lakes with a possible improvement in walleye stocks.
Effects of advanced photoperiod cycle on the epidermis and gonadosomatic index of 2‐year‐old rainbow trout, Salmo gairdneri R., reared at natural temperature
Authors: Nakari T. , Soivio A. , Pesonen S.
Published: January 2006

Sexual dimorphism was shown in the epidermis of 2‐year‐old rainbow trout. The changes in the epidermis which appear normally at the spawning time can be timed earlier by advancing the normal annual photoperiod cycle by three months.

The epidermis of the advanced fish was significantly thicker than that of the control fish during the winter preceding spawning. For most of the year the epidermis of the males was thicker than that of the females, but females had more mucous cells in the epidermis than males. The maximum concentration of plasma testosterone coincided with the epidermal thickening.
Food and feeding habits of Ilisha africana (Bloch) (Pisces: Clupeidae) off the Lagos coast, Nigeria
Authors: Marcus O.
Published: January 2006

A total of 2215 specimens of Ilisha africana (Bloch) were examined for the food habits of the species off the Lagos coast, Nigeria. Their food consisted mainly of crustaceans, fish and molluscs; less important in the stomach contents were insects, annelids, chaetognaths, coelenterates, urochordates and phytoplankton. The incidence of nematodes in the stomachs was low. Monthly variation of food as well as variation with fish size and water depth were examined, as was the relationship of food composition to components of the plankton fauna. Feeding habits of I. africana were compared with those Sardinella maderensis (Lowe), Galeoides decadatylus (Bloch), Brachydeuterus auritus (Val.) and Vomer setapinnis (Mitchill); there was an overall diversity in the diets of these fish species.
The influence of simulated aquatic macrophytes on the zooplankton consumption rate of juvenile roach, Rutilus rutilus, rudd, Scardinius erythrophthalmus, and perch, Perca fluviatilis
Authors: Winfield I. J.
Published: January 2006

Laboratory experiments showed that, of zooplanktivorous roach, rudd and perch, in the absence of any environmental structure roach were the most efficient feeders, but high densities of simulated submerged marcrophytes elevated perch to this position; rudd matched the performances of perch and roach only at intermediate structure densities. These changes in efficiency rankings with increased structure were the result of overall decreases in the performances of roach and rudd. Simulated water lilies and emergent reeds had their own influences on consumption rate. These effects were largely mediated through relationships between structure density and swimming speed; roach and rudd, not perch, showed reduced swimming speeds in the more structured environments. Observations of the routine behaviour of the fish suggest that their assessment of predation risk may be an important factor in determining their activity level and hence foraging strategy.
Visual cues determining prey selection by the turbot, Scophthalmus maximus L.
Authors: Holmes R. A. , Gibson R. N.
Published: January 2006

By presenting juvenile turbot, Scophthalmus maximus L., with models and natural prey, Crangon crangon, standardised for size, some of the visual characteristics that elicit a predatory response have been determined. By far the most important stimulus was overall body movement, but appendage movements of the crustacean and a ratio of vertical to horizontal dimensions lower than about 1:5 were also of significance. The body shape of a prey was not of great importance. Evidence was obtained for the heterogeneous summation of stimuli.
Chemo‐attraction between juveniles of two sympatric stocks of Arctic charr, Salvelinus alpinus (L.), and their gene frequency of serum esterases
Authors: Olsén K. H.
Published: January 2006

Juvenile Arctic charr, Salvelinus alpinus (L.), from two spawning locations, Åbränna stock and Holderströmmen stock, in Lake Torrön, Sweden, were used crosswise as odour donors and receivers in fluvarium tests concerning attraction to stock‐specific odours. The momentary positions of the odour‐receiving charr were recorded with a film camera and filtered flash light (no transmittance < 670 nm). One test fish at a time was placed in the test area to choose in darkness between two water qualities, viz. (i) control tests were run with pure water all over the test yard; (ii) pure water and water having passed 20 specimens of their own stock; (iii) pure water and water conditioned by the presence of 20 specimens of the sympatric stock; (iv) water conditioned by passing 20 specimens of either stock. Specimens of both stocks were attracted to water scented by either stock. The åbränna (AB) but not the Holderströmmen stock (HO) showed significantly stronger attraction to scent of their own stock than to the sympatric stock. This was supported in tests with simultaneous supply of AB and HO‐scented water, when AB significantly preferred the water having passed specimens of its own stock, while HO did not prefer any water quality. Out of 300,65 specimens from each stock were analyzed as to the gene frequency of serum esterases. The HO sample, in contrast to AB, was heterogeneous as the frequency of heterozygotes was lower than that expected under Hardy‐Weinberg equilibrium. No heterogeneity in gene frequencies was observed between AB and HO. The results of both odour attraction tests and the gene frequency analysis points to AB, in contrast to HO, as being offspring from a discrete stock.
Physiological and social constraints on growth of Arctic charr, Salvelinus alpinus L.: an investigation of factors leading to stunting
Authors: Jobling M. , Reinsnes T.‐G.
Published: January 2006

When stunted (runt) Arctic charr, Salvelinus alpinus, were reared together in small groups growth rates were low. Contrary to expectation, there did not arise a rapidly growing despot within each group. It is suggested that the narrow size range offish within groups prevented the rapid formation of clear‐cut dominance hierarchies. Fish reared in isolation had significantly higher and more variable rates of growth than those held in groups, demonstrating that social interactions between individuals were responsible for growth suppression of grouped‐reared fish. There were no significant differences in growth rates between fish allowed visual contact with conspecifics and those held in visual isolation, indicating that visual contact is insufficient to cause growth depensation in Arctic charr. Despite the fact that growth rates of stunted (runt) Arctic charr improved when they were held in isolation, the growth rates recorded were substantially lower than those of normal individuals reared under hatchery conditions. It is concluded that physiological (genetic) factors are important in the determination of the slow growth rates of stunted (runt) Arctic charr and that this trend is exacerbated by social interactions with more rapidly growing siblings.
Some aspects of the biology of the red bass, Lutjanus bohar (Forsskal), from the Tigak Islands, Papua New Guinea
Authors: Wright A. , Dalzell P. J. , Richards A. H.
Published: January 2006

The growth rate, food, reproduction and mortality rates of the red bass, Lutjanus bohar, are described for fish associated with coral reefs in the Tigak Islands of Papua New Guinea. Spawning intensity by month was investigated by examination of gonad maturation stages. The length–at–maturity of female L. bohar was estimated from the relationship between changes in gonad index with increasing size. Female fish matured at about 45–0 cm fork length. The Petersen method was used to obtain age–at–length data from length frequency data of L. bohar captured by hook–and–line fishing. The growth of L. bohar was described by a von Bertalanffy growth curve with the parameters AT=0.27 and L∞= 81.7 cm. There was a positive correlation between water depth (D) and the length of L. bohar (L) that was described by L= 318–8+ 3.050 D. The mortality rates (Z) of L. bohar from shallow (≤30m) and deep (≤80m) water were estimated from length converted catch curves and were 1–181 and 0–64 respectively. The high Z value for the shallow water population of L. bohar was ascribed to the migration of larger specimens into deeper water. The deep water population of L. bohar remains unfished and the estimate of Z was believed to be equivalent to the natural mortality rate (M). An empirical method of calculating M gave an estimate of 0.59. Lutjanus bohar is a carnivorous piscivore that feeds throughout the water column.
A cytochemical and light microscopical study of the peripheral blood leucocytes of Oreochromis mossambicus, Cichlidae
Authors: Doggett T. A. , Wrathmell A. B. , Harris J. E.
Published: January 2006

The morphological characteristics of the peripheral leucocytes of the cichlid O. mossambicus were studied using light microscopy. Cytochemical procedures and phagocytic studies were employed. Four main types of leucocytes could be recognized: lymphocytes, thrombocytes, monocytes and granulocytes. Two distinct types of granulocyte were identified. Monocytes and one type of granulocyte were found to be phagocytic.
An analysis of the primary and secondary antibody response in intact and thymectomized rainbow trout, Salmo gairdneri Richardson, to human gamma globulin and Aeromonas salmonicida
Authors: Tatner M. F. , Adams A. , Leschen W.
Published: January 2006

The antibody response to human gamma globulin (HGG) and Aeromonas salmonicida (AS) in control and long‐term thymectomized rainbow trout was individually monitored in 120 fish. The fish responded poorly to HGG and no memory response was observed. There was no difference in response between control fish and fish which had been thymectomized for 5 months before immunization. However, 9‐month thymectomized fish had lower titres than controls. The response to AS was vigorous and significant memory was demonstrated after a second injection. There was no difference in response between control and thymectomized fish. The individual variation in response was not related to body size, antigen dose, sex or reproductive state. The results are discussed in terms of the thymus dependency or independency of antigens in fish, and the role and life span of T cell subsets, such as ‘helper’ and ‘;suppressor’ cells.
The influence of sand on the estimation of resting metabolic rate of juvenile sole, Solea solea (L.)
Authors: Howell B. R. , Canario A. V. M.
Published: January 2006

The influence of a sandy substrate on the estimation of the resting metabolic rate of juvenile sole was determined using a static type of respirometer. Oxygen consumption of fish deprived of sand was almost double that of fish provided with sand.
Modulation of the mitogenic PHA response of carp, Cyprinus carpio L., by extracellular products of Aeromonas salmonicida
Authors: Pourreau C. N. , Koopman M. B. H. , Hendriks G. F. R. , Evenberg D. , van Muiswinkel W. B.
Published: January 2006

The influence of bacteria‐free supernatants from cultures of atypical virulent (V234/81, auto‐agglutinating. A‐layer positive) and avirulent (126/68, non‐agglutinating, A‐layer negative) strains of A. salmonicida, obtained after different culture times in yeast‐tryptone broth at 20°C, was tested on the PHA response of carp pronephric leucocytes in vitro. Supernatants from virulent cultures modulated the response, whereas avirulent supernatants had no effect. The response was enhanced (400%) by supernatant from early virulent cultures (20 h), but severely depressed (<3%) by later ones (96 h). The effects were dose‐dependent. Inhibitory activity of 96‐h supernatant was lost by heating (70°C, 30 min), suggesting that the inhibiting factors are all proteinaceous.

Heated 96‐h supernatant was as stimulatory as early supernatant. Stimulation of leucocytes also occurred in the absence of PHA with early and heat‐treated 96‐h supernatants, but at a tenth of the level, suggesting that only stimulated cells (blasts) might respond to the substance(s) present in supernatants. Membrane fragments from virulent and avirulent bacteria, and purified LPS from virulent bacteria, were stimulatory with or without PHA. Endotoxin‐free, heat‐treated, 96‐h culture supernatants were also stimulatory, suggesting that an additional mitogenic factor(s), other than LPS, is present in the supernatants. The modulating in vitro effects of extracellular products from A. salmonicida might explain the immunosuppression seen during later stages of erythrodermatitis in vivo.
Occurrence of Haemogregarina bigemina (Protozoa: Apicomplexa) in Blennius pholis (Pisces: Blenniidae) along the Portuguese west coast
Authors: Eiras J. C.
Published: January 2006

The occurrence of Haemogregarina bigemina in Blennius pholis was studied at four localities on the Portuguese west coast. Prevalence ranged from 2.9 to 78.6% and was significantly different (P< 0.01) at the various localities. Intensity of infection in individual fish was usually low (< 0.01 % of erythrocytes infected) but one specimen was heavily parasitized (2.8% erythrocytes infected). The smallest infected fish was 3.2 cm long; all 7.0 cm and longer fish were infected. Development was not seen outside erythrocytes or within leucocytes. Some erythrocytes (< 0.01%) in one fish were unusual in containing four mature gametocytes. Circumstantial evidence indicates that prevalence was higher in polluted waters. Possible transmission routes for the parasite are discussed.
The survival of larval perch, Perca fluviatilis L., under different combinations of acidity and duration of acid conditions, analysed with a generalized linear model
Authors: Hildén M. , Hirvi J.‐P.
Published: January 2006

Naturally‐occurring acidified water was used in a factorial experiment to study the effects of acidity and duration of acidic conditions on short‐term survival of late larvae of perch. The analysis demonstrated that both factors influenced probability of survival. When the duration of acidic conditions exceeded 2 days, acidity alone could be used as a predictor of survival. At pH values below 4.5, and durations of 6–24 h, unexpectedly high survival rates were observed. Analyses of the concentration of total and soluble aluminium suggested that aluminium chemistry played a significant part in determining the observed survival pattern.
The effects of acid and acid/aluminum exposure on circulating plasma cortisol levels and other blood parameters in the rainbow trout, Salmo gairdneri
Authors: Goss G. G. , Wood C. M.
Published: January 2006

Softwater (Ca2+=50, Na+= 50(μequiv. l−1) acclimated rainbow trout were fitted with chronic arterial catheters to allow for repetitive blood sampling. After 48 h recovery they were then exposed to either control (pH 6.5, Al = 0μg l−1), acid (pH 4.8, Al = 0μg l−1) or acid plus aluminum (pH 4.8, A1 = 112 μg l−1) conditions for 72 h. Parameters measured included blood glucose, lactate, haemoglobin, haematocrit and plasma Na+, Cl−, protein and cortisol.

Exposure to pH 4′8 alone caused no mortality, a moderate ionoregulatory disturbance and a transient elevation in plasma cortisol. All other parameters were not significantly different from controls. Addition of aluminum to this exposure caused 100% mortality with a mean survival time of only 27.0 h. There was a marked decrease in plasma ions, hyperglycemia, lactate accumulation, haemoconcentration, red cell swelling, and a sharp rise in plasma cortisol becoming greatly increased as the fish neared death. The mechanism of toxicity of acute acid/aluminum exposure, the role for cortisol under such conditions, and the validity of cortisol and glucose as indicators of stress in fish are discussed.
Normal ranges of some blood chemistry parameters in adult farmed Atlantic salmon, Salmo salar
Authors: Sandnes K. , Lie Ø. , Waagbø R.
Published: January 2006

Blood samples from healthy adult Atlantic salmon fed an optimal diet in net sea pens were collected at intervals from October to May. Haematological determinations and biochemical serum analyses were carried out on 20 fish in each of seven samples. The ranges of haemato‐logical values for sample means were: haematocrit 44–49%, haemoglobin 8.9–10.4 g 100ml−1, red blood cell count 0.85–1.10 × 1012 l−1, MCV 441–553 × 10−15 1, MCH 94–106 × 10−6 g, MCHC 19.4–21.7 g 100ml−1 and leucocrit 0.43–0.96%. The ranges of enzyme activities in serum, for sample means, were: alkaline phosphatase 647–988Ul−1, aspartate aminotrans‐ferase 202–351 Ul−1 and alanine aminotransferase 4–8 Ul−1. The ranges of the other parameters analyzed in serum were: total protein 41.6–56.6 gl−1, albumin 18.3–24.3 gl−1, albumin/total protein ratio 39.3–44.0%, creatinine 26–46 μmol, triglycerides 2.53–4.98 μmol and cholesterol 9.3–12.8 μmol. These values are considered to be the normal ranges in healthy fish. Variations due to seasonal changes, and the clinical significance of the selected parameters, are discussed. Data showing the reproducibility of the biochemical analyses in serum are presented.
Determination of the age of young American eels, Anguilla rostrata, in fresh water, based on otolith surface area and microstructure
Authors: Michaud M. , Dutil J.‐D. , Dodson J. J.
Published: January 2006

The time elvers of the American eel, Anguilla rostrata, spend in an estuary prior to their migration into fresh water was assessed. A distinct mark was formed on elvers' otoliths during their first 2 to 3 weeks in the river estuary. This mark was used to distinguish between growth in fresh water and in salt water. Migrating eels collected at a falls 4 km from the estuary exhibited bimodal length and weight distributions. Frequency distributions showed that eels collected in the estuary were smaller and had smaller otoliths than eels collected at the falls, indicating that elvers do not reach the falls in the same year as they enter the estuary. The three modal groups most probably represent three age–classes. However, the otoliths of elvers collected in the estuary had only the mark of transition whereas eels in the first and second mode at the falls usually had two rings (1–4) and four rings (3–6) per otolith, respectively, in addition to the mark of transition, as viewed under SEM. The possibility that ring formation is not annual means that the use of otoliths for the age determination of eels in this study has not been validated.
Morphological changes in the oesophageal epithelium during adaptation to salinities in Oreochromis mossambicus, O. niloticus and their hybrid
Authors: Cataldi E. , Crosetti D. , Conte G. , D'Ovidio D. , Cataudella S.
Published: January 2006

Morphological changes in the oesophageal epithelium of Oreochromis mossambicus, O. niloticus, and O. mossambicus x O. niloticus hybrids were studied during adaptation to sea water. In fresh water, the epithelium is stratified and rich with mucous cells. In salt water, modifications occur in the oesophagus of O. mossambicus and of the hybrid: mucosa folds are more vascularized and covered with a monolayered epithelium, alternating with a multilayered one. The oesophagus of O. niloticus does not seem to be affected by salinity but this species survives only for brief periods in sea water. These observations underline the close relationship between the oesophagus morphology and salinity tolerance in tilapias.
Haematological, haematopoietic and biochemical responses to thermal stress in an air‐breathing freshwater fish, Channa punctatus Bloch
Authors: Dheer J. M. S.
Published: January 2006

Results of experiments on fishes maintained at three different temperatures (25, 30 and 35° C), compared with a control group maintained at 14° C, are presented. Fishes showed obvious signs of stress at 30 and 35° C, as indicated by loss of weight and increase in mortality rate. On the other hand, those at 14 and 25° C gained weight steadily and showed normal growth.

Biochemical studies confirm the stress symptoms, as there was a steady, statistically significant fall in blood glucose level and depletion of glycogen reserves in liver and muscle within the first week at 35° C and by the fourth week at 30° C.

These results were further confirmed by haematological investigations. All the parameters tested indicated deviation from the normal healthy conditions seen at 14 and 25° C. The deviations in most of the parameters at 35° C were statistically significant from about the second week, and at 30° C by the fourth week. Erythrocytic polycythemia accompanied by an increase in haemoglobin content and haematocrit values were indicative of thermal stress. Leucopenia was mainly contributed by neutrophil decrease, but a relative increase in thrombocytes was recorded.

Correlated erythropoietic studies indicated an increase both in the initial (small lymphoid haemoblast) and penultimate (mature reticulocyte) stages in red cell development, although the intermediate stages decreased in number. Similar trends in the different stages of neutrophil development were observed. The significance of these changes in the context of homeostatic phenomena is discussed.
Ecomorphological adaptation to oxygen deficiency in Amazon floodplains by serrasalmid fish of the genus Mylossoma
Authors: Saint‐Paul U. , Soares G. M.
Published: January 2006

Serrasalmids of the genus Mylossoma are obligate gill‐breathers that are encountered in the floodplain lakes of Amazonia, even when the oxygen concentrations there are below 0.5 mg l−1. It was shown by experiments that fish of these species are capable of utilizing the oxygen‐rich surface layer of the water for respiration, in order to survive periods of habitat‐induced hypoxia. This so‐called aquatic surface respiration entails an increase in locomotory activity and an ecomorphosis involving the formation of a dermal extension on the lower jaw, that apparently has a hydrodynamic function for using the surface layer for gill respiration; when the water is aerated, it retrogresses to its original size. Histological examination showed that the extension is formed by edematous processes in the stratum spongiosum.
The effects of sublethal concentrations of cadmium on haematological parameters in the dogfish, Scyliorhinus canicula
Authors: Tort L. , Torres P.
Published: January 2006

Dogfish were subjected to sublethal cadmium exposure (25 mg l−1) for 24 and 96 h. The effects of this treatment on some blood parameters were analysed. Decreases of haematocrit, leucocrit and mean corpuscular volume and increases of haemoglobin concentration, red blood cell count and mean corpuscular haemoglobin concentration were observed after 24‐h exposure. Most parameters which had changed values at 24 h returned to control values at 96 h, whereas some parameters which were unchanged at 24 h showed a significant variation at 96 h (plasma glucose and lactate levels). The causes of these alterations and the patterns of recovery are discussed.
Histological changes in the gonad, skin, intestine and olfactory epithelium of artificially‐matured male American eels, Anguilla rostrata (LeSueur)
Authors: Sorensen P. W. , Pankhurst N. W.
Published: January 2006

Migratory (silver) male American eels were injected weekly for 5 weeks with human chorionic gonadotropin (hCG), salmon pituitary extract, hydrocortisone 21‐hemisuccinate (cortisol), or saline to determine the effects of induced maturation on the histology of their gonads, skin, intestines and olfactory epithelia. Treatment with hCG induced full sexual maturity, salmon pituitary evoked only limited spermatogenesis, and neither hydrocortisone nor saline had any effect on the gonad. Eels injected with hCG and salmon pituitary experienced no changes in skin morphology, but the epidermal thickness of saline‐ and hydrocortisone‐treated fish decreased. Intestinal morphology did not change in any of the treatment groups. Both the presumed sensory and non‐sensory portions of the olfactory epithelium of hCG‐ and pituitary‐treated males exhibited a decrease in thickness, structural degeneration, and non‐significant reductions in mucous cell density. Some of these changes in maturing male eels are similar to those previously observed in maturing females but others are different; it appears likely that maturing Anguilla are sexually dimorphic and that these changes are adaptive and not artifacts of the hormone treatments.
The cause of extreme year class variation in a population of roach, Rutilus rutilus L., from a eutrophic lake in southern England
Authors: Wyatt R. J.
Published: January 2006

Investigations into the biology of the roach population at Slapton Ley, Devon, U.K. were carried out between October 1982 and December 1984 and data collected from the lake since 1977 have been re‐analysed to assist interpretation. The roach population has been characterized in recent years by extreme year class variation and a tendency for year classes to alternate in strength. The survival of the roach was very poor, and the spawning population therefore consisted largely of 2‐and some 3‐year‐old fish. Consequently, the size of the spawning stock was small and dependent on the strengths of the year classes that it contained. Recruitment to many year classes was probably limited by the size of the spawning stock. The occurrence of a poor year class in the population would therefore set up an autonomous cycle of poor recruitment to alternate year classes in a manner similar to many tropical marine fisheries. Observation of other British roach populations showed that a short life‐span may be associated with conditions that promote very rapid growth rates. The growth rate of individual roach at Slapton was found to be one of the fastest in Britain, and this was apparently due to the very high productivity of Slapton Ley together with the persistence of the roach population at very low densities.
Evidence for the assignment of Dolichopteryx brachyrhynchus Parr to the genus Bathylychnops Cohen (Pisces, Opisthoproctidae)
Authors: Badcock J.
Published: January 2006

The rare opisthoproctid genus Bathylychnops has previously been regarded as containing a single species, B. exilis, known from the transition waters of the eastern North Pacific and, questionably, from the North Atlantic. While the post‐larval and juvenile material reported here reaffirms the occurrence of the genus in the North Atlantic, and extends its range into the Indian Ocean, the lower vertebral and higher pelvic ray counts of specimens denies their reference to B. exilis. The systematics of the closely‐related genus Dolichopteryx are poorly known, distinction from Bathylychnops resting mainly upon Dolichopteryx having multiserial, as opposed to uniserial, vomerine teeth and lacking an accessory scleral lens to the eye. The species D. brachyrhynchus, known from a single, damaged Atlantic specimen, shows marked similarities with Bathylychnops in pigmentation and the relative positions of fins, anus and dorsal adipose fin, thereby differing from all its congeners. Although the holotype of D. brachyrhynchus lacks an accessory scleral lens, perhaps through damage, it has uniserial vomerine teeth. This latter character and those of similarities in meristics, morphometrics and pigmentation shown with Atlantic‐Indian Ocean Bathylychnops (contra B. exilis) are considered sufficient evidence to regard the two species as synonymous and hence transfer D. brachyrhynchus to the genus Bathylychnops.
Blood coagulation factors in the freshwater fish Oreochromis mossambicus
Authors: Smit G. L. , Schoonbee H. J.
Published: January 2006

Blood coagulation in Oreochromis mossambicus was evaluated by determination of whole blood clotting times for traumatic and atraumatic blood samples and of intrinsic and extrinsic coagulation factors. Results indicate that this process is similar to mammalian coagulation, although clotting times were much reduced. In addition, species specificity to prothrombin activator was also indicated, which was not affected significantly by increased temperatures.
Salinity effects on cytometrical parameters of the kidney in the euryhaline teleost Oreochromis mossambicus Peters
Authors: Hwang P. P. , Wu S. M.
Published: January 2006

Study of the effects of environmental salinity on the glomerular areas and the nuclear areas of the renal tubules in tilapia showed significant differences (P < 0.001 or 0.05) between seawater‐ and freshwater‐adapted fish. Upon seawater adaptation, there were decreases in the glomerular areas and the nuclear areas in the main segments of the nephron: glomerular, −24.1%; 1st proximal, −17.1%; 2nd proximal, −21.5%; distal, −9.1%; collecting, −26.5%. These cytometrical changes are discussed in relation to the different osmoregulatory functions of euryhaline teleosts adapted to sea water and to fresh water.
Morphology and histology of the swimbladder and infrastructure of respiratory epithelium in the air‐breathing catfish, Pangasius sutchi (Pangasiidae)
Authors: Zheng W. B. , Liu W. S.
Published: January 2006

The swimbladder of Pangasius sutchi is made up of fibrosa, collagenic fibre walls and mucosa; its walls extend into the lumen to form dense respiratory alveoli, with the inner surface covered by a highly vascularized respiratory epithelium. The thin epithelial cells have the structural characteristics and function of type I and type II cells of lung alveoli in higher mammals. These cells and the endothelial cells compose the barrier through which gases must pass in the exchange between blood and air. The study shows that the swimbladder of P. sutchi is an important accessory respiratory organ.
Biochemical changes in longear sunfish, Lepomis megalotis, associated with lead, cadmium and zinc from mine tailings
Authors: Dwyer F. J. , Schmitt C. J. , Finger S. E. , Mehrle P. M.
Published: January 2006

Longear sunfish were collected from a stream contaminated with mine tailings rich in lead (Pb), cadmium (Cd) and zinc (Zn). Blood samples were analysed for δ‐aminolevulinic acid dehydratase (ALA‐D) activity and Pb concentration. Vertebrae were tested for bone strength and composition, and Pb, Zn, and Cd concentrations were determined in muscle tissue. ALA‐D activity was negatively correlated with blood Pb concentration (r=–0.66), and enzyme activity was significantly higher and blood Pb significantly lower at the reference site than at the contaminated sites. Blood Pb was highly correlated with Pb in muscle tissue (r= 0.72), and the concentrations of Pb and Cd in muscle tissues were themselves correlated (r= 0.64). In fish from contaminated sites, two of the mechanical properties of the vertebrae measured (elastic limit and modulus of elasticity) were significantly different from values in fish from the reference site. These properties and one other (stress) were weakly correlated with muscle Cd concentration (0.42 < r < 0.46). Biochemical differences among fish from different sites were also evident; concentrations of calcium, phosphorus and collagen were lower in the vertebrae of fish from some of the contaminated sites than at the reference site, and bone phosphorus was negatively correlated with concentrations of Pb in both muscle (r=– 0.62) and blood (r=– 0.75). Collectively, these results indicate that, in addition to the well‐documented effects of Pb on haem synthesis, other important biochemical pathways may be disrupted by continuous low‐level exposure to elemental contaminants.
Recruitment and maximal diameter of axial muscle fibres in teleosts and their relationship to somatic growth and ultimate size
Authors: Weatherley A. H. , Gill H. S. , Lobo A. F.
Published: January 2006

Growth of white axial muscle fibres of ten species of freshwater teleosts from five families (Cyprinidae, Centrarchidae, Percidae, Salmonidae, Esocidae) possessing widely different growth rates and ultimate sizes have been studied. The dynamics of muscle increase (i.e. increase in fibre numbers and/or diameter) appears to determine the ability for rapid somatic growth and large ultimate size in teleosts. Thus, the largest and fastest growing species (smallmouth bass, lake whitefish, rainbow trout, muskellunge) show evidence of sustained recruitment of muscle fibres to a large size, in contrast to the smaller and slower growing species (bluntnose minnow, longnose dace). Pumpkinseed, bluegill and yellow perch are all intermediate in fibre growth dynamics, growth and ultimate size between the smaller and larger species. Moreover, the ability of teleosts to grow rapidly and attain a large ultimate size is dependent on the body length at which recruitment of new muscle fibres into the growing axial muscle ceases. The regression equation, y=– 0.29 + 2.26 (x), showing the relationship (r = 0.95) between ultimate body length, x, and fork length at cessation of recruitment, y, indicated that for these teleosts, recruitment tends to cease when the fork length reaches about 44% of the ultimate body length. Possible mechanisms to account for this relationship are proposed, and the role of the ultimate fibre diameter in posing limits to the ultimate size of the species is discussed.
Ichthyoplankton entrainment
Authors: Dempsey C. H.
Published: January 2006

A 12‐month study was carried out to quantify the numbers of fish eggs and larvae taken into Fawley Power Station on Southampton Water. Fourteen species of fish and the eggs of four species were identified. Estimates are given of the total annual entrainment in immediate numbers and adult equivalents. Findings of previous studies are confirmed showing a diurnal effect and that a degree of avoidance of entrainment by larvae is possible. It is concluded that entrainment of early life stages by Fawley Power Station does not significantly adversely affect local fish populations.
A morphometric analysis of the spinal motor pool in relation to its target muscle during growth in the trout, Salmo gairdneri Richardson
Authors: Alfei L. , Bertoncello G. , Gelosi E. , Parvopassu F.
Published: January 2006

The relation between number and size of spinal motoneurons and the dimension of myotomal muscle has been investigated in trout at different stages of embryonic, larval and postlarval development (body length 1–15 cm). Three spinal segments have been analysed (cervical, trunk and caudal) and the following parameters were determined by means of a Micromeasurements Image Analyzer: (a) mean cross‐sectional myotomal area; (b) mean soma size of principal (or dorsomedian, DM) and secondary (or ventrolateral, VL) motoneurons; (c) DM and VL motoneuron density per segment. Myotomal muscle and motor pool growth was evaluated by percent increments of a, b and c parameters at each stage. Their relationships were denned by equations of computed regression lines.

The analysis provided evidence that: (1) a continuous exponential growth of mean myotomal area takes place in the three segments, with the same trend and with the lowest values in the caudal segment; (2) DM and VL motoneuron size and density per segment also increase during development, with the least value in the caudal segment, VL parameters being of lesser value than DM; (3) motoneuron pool and its target myotomal muscle parameters bear a linear relationship as defined by equations of computer regression lines; (4) motoneuron number percent increment at early eleutherembryonic stage precedes myotomal area increment which takes place during late eleutherembryonic stage.

It is apparent that spinal motor pool and target myotomal muscle grow at the same rate in the trout during the considered stages. The discussion links this fact with the hypothesis of a neuronal influence on muscle fibre type differentiation.
A key to the identification of larval bream, Abramis brama, white bream, Blicca bjoerkna, and roach, Rutilus rutilus
Authors: Mooij W. M.
Published: January 2006

Intra‐ and interspecific differences in pigmentation between finfold larvae of the three most abundant cyprinids in Dutch eutrophic waters, bream, white bream and roach, were studied, using laboratory‐raised larvae in the length range 8–11 mm. Because the internal pigmentation of the larvae has been used for identification, some attention is paid to the effects of different ways of fixation and preservation on transparency. The size and the shape of the melanophores, as described in the literature, could not be used as identification characters because of too much intraspecific variation and the effects of light conditions at the moment of fixation. Three characters proved to be significant for the identification of the larvae of the three species. Roach can be distinguished from bream and white bream by the pattern of melanophores on the belly. A second character is the pigmentation of the ventral aorta, which is only found in white bream. Lastly bream shows an irregular pattern of melanophores on the dorsal side, in contrast to roach which has a regular pattern.
Biological and ecological effects of a Ligula intestinalis (L.) infestation of the gudgeon, Gobiogobio (L.), in Lough Neagh, Northern Ireland
Authors: Bean C. W. , Winfield I. J.
Published: January 2006

A study was made of the effects of a Ligula intestinalis infestation on the biology and distribution of gudgeon in Lough Neagh, Northern Ireland. During the summer months, when the majority of the gudgeon population was restricted to the inshore areas of the lough, Ligula was present in all age (size) classes of the host although levels of infestation were highest in the oldest individuals. While there was no significant effect on the length‐weight relationship of the gudgeon, the presence of the parasite did adversely affect gonad size in both sexes. Ligula also influenced the distribution of the gudgeon population by decreasing the swimming depth of infested individuals and by delaying their autumnal migration to the deeper offshore parts of the lough.
The effects of water hardness upon the uptake, accumulation and excretion of zinc in the brown trout, Salmo trutta L.
Authors: Everall N. C. , Macfarlane N. A. A. , Sedgwick R. W.
Published: January 2006

The effects of water hardness (9 and 220 mgl−1 as CaCO3) upon zinc exchange in brown trout exposed to 0.77 μmol Zn 1−1 have been investigated using artificial soft water (<49.9 μmol Ca l‐1, <40.1 μmol Mg 1−1) and mains hard water (1671.7 μmol Ca 1−1, 493.6 μmol Mg 1−1) of known composition. Both hard and soft water‐adapted fish exhibited a bimodal pattern of net zinc influx. Net zinc influxes during both fast and slow uptake phases were significantly greater (P<0.001) in soft (82.9 and 6.2 μmol Zn 100 g−1 h−1) than in hard water (46.3 and 2.4 μmol Zn 100 g h−1). Zinc efflux (‐ 0.2 μmol Zn 100 g−1 h−1) was enhanced only in hard water during the slow net influx phase.

Brown trout exposed to zinc in hard water and placed in metal‐free media exhibited a greater net efflux (‐ 25.6 μmol Zn 100 g−1 h−1) of the metal than did fish in soft water (‐4.2 μmol Zn 100 g−1 h−1) treated in the same manner. Tissue 65Zn activities reflected both the differences in uptake and excretion rates of the metal between hard and soft water fish. During zinc exposure (0.77 μmol Zn 1−1) high water hardness reduced tissue burdens of the metal by reducing net branchial influx, and enhancing efflux of the metal in hard water fish.
An appraisal of anglers’catches in the River Severn, England
Authors: North E. , Hickley P.
Published: January 2006

Angling competition catch data were gathered by postal questionnaire during 1975–1986 for three sections of the R. Severn. Angling success and species composition were analysed relative to both water temperature and year. The importance of barbel increased rapidly from 5° C to 15° C then levelled. Roach, chub and gudgeon showed peaks in the ranges 7–12, 10–15 and 9–16° C, respectively. Dace, bleak, eel and bream displayed consistent increases in contribution to catch with rising temperature. Year‐to‐year variations in angling success differed according to river section and for the most part could be explained by changes in the importance of species. The percentage of anglers with catch during the period June‐November ranged from 50 to 91% and catch rates from 66 to 121 g man 1 h 1.
Dose‐related effects of 17βoestradiol (E2) on liver weight, plasma E2, protein, calcium and thyroid hormone levels, and measurement of the binding of thyroid hormones to vitellogenin in rainbow trout, Salmo gairdneri Richardson
Authors: Flett P. A. , Leatherland J. F.
Published: January 2006

Administration of 17β‐oestradiol (E2) to rainbow trout, in the form of hydrogenated coconut oil implants produced a stable, long‐term elevation in plasma E2 levels. The elevation was doserelated (over the range 1–10mg kg‐1 body weight) both 4 and 8 weeks after implantation. Dose‐related increases were also observed with respect to liver weight‐body weight ratios and plasma protein levels. Plasma T3 and total calcium levels were depressed and elevated, respectively, by E2 treatment but the responses were not linearly related to the dose of E2 administered; there was no significant effect of E2 on plasma T4 levels.

E2 induced a shift in the binding of T3 to plasma proteins, with T3 binding to smaller molecular weight proteins; neither T4 nor T3 bound to vitellogenin which was present at high levels in the plasma of E2‐treated fish.
Morphology of central compartment and vasculature of the gills of Lepidosiren paradoxa (Fitzinger)
Authors: Morgan M. , Wright D. E.
Published: January 2006

The four paired gill arches of the South American lungfish Lepidosiren paradoxa contain single branchial arteries directly connecting dorsal and ventral arteries. In gill arches 3 and 4 the branchial arteries also supply looped arlerioles and capillaries to much‐reduced gill filaments. Regulation of blood between these routes is thought to be by alteration of vascular resistance. Within the filaments, extensive subepithelial capillary networks and numerous small pumps connect lymphatic vessels in the central connective tissue compartment with venules which, in turn, drain to paired branchial veins.

The features of the endothelium of many of the filament blood vessels suggest extensive transporting, haematolytic and granulopoeitic functions. Large numbers of macrophages pack the connective tissue. Many contain extensive quantities of haemosiderin.
The effects of hypoxia and paraquat on the superoxide dismutase activity in different organs of carp, Cyprinus carpio L.
Authors: Víg É. , Nemcsók J.
Published: January 2006

The effects of hypoxia and paraquat (PQ) were investigated on the superoxide dismutase (SOD) activity in carp gill, liver and brain. Increases in SOD activity occurred in these organs following exposure to both PQ and hypoxia. PQ administration under hypoxic conditions significantly increased the SOD activity in the gill as compared to the level in animals in an hypoxic state without PQ treatment. No such change was observed in the liver or brain.
The interactions of water hardness and pH with the acute toxicity of zinc to the brown trout, Salmo trutta L.
Authors: Everall N. C. , Macfarlane N. A. A. , Sedgwick R. W.
Published: January 2006

Exposure of brown trout, Salmo trutta, to zinc under continuous flow conditions over 96 h showed that both water hardness and pH exert major influences on the toxicity of the metal. 96‐h LC50 values for total zinc ranged from <0.14mg 1−1 in alkaline soft water (pH 8; lOmg 1−1 as CaCO3) to 3.20 mg 1−1 in acidic hard water (pH 5; 204 mg 1−1 as CaCO3). A variable reduction in zinc toxicity in hard water compared with soft water over the pH range 4–9 was attributed to high external calcium. Zinc toxicity was positively correlated with decreasing acidity over the pH range 5–7, the metal being most toxic at pH 8–9 where metal complexes predominate. Below pH 5 metal toxicity also increased, irrespective of hardness. Water hardness and pH interacted with zinc toxicity in a complex manner, apparently dependent on physical and chemical transformations of the metal, and as changes in uptake. detoxification and excretion by the fish.