bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of fasting on glycogen metabolism and activities of glycolytic and gluconeogenic enzymes in the mudskipper Boleophthalmus boddaerti
Authors: Lim A.L.L. , Ip Y.K.
Published: January 2006

During starvation, muscle glycogen in Boleophthalmus boddaerti was utilized preferentially over liver glycogen. In the first 10 days of fasting, the ratio of the active‘a’form of glycogen phosphorylase to total phosphorylase present in the liver was small. During this period, the active‘I’form of glycogen synthetase increased in the same tissue. In the muscle, the phosphorylase‘a’activity declined during the first 7 days and increased thereafter while the total glycogen synthetase activity showed a drastic decline during the first 13 days of fasting.

The glycogen level in the liver and muscle of mudskippers starved for 21 days increased after refeeding. After 6 and 12 h refeeding, liver glycogen level was 8·5 ± 2·3 and 6·9 ± 4·5 mg·g wet wt 1, respectively, as compared to 5·8 ± l·6mg·g wet wt 1 in unfed fish. Muscle glycogen level after 6 and 12 h refeeding was 0·96±0·76 and 0·82 ± 0·50 mg·g wet wt 1, respectively, as opposed to 0·21 ± 0·12 mg·g wet wt 1 in the 21‐days fasted fish. At the same time, activities of glycogen phosphorylase in the muscle and liver increased while the active‘I’form of glycogen synthetase showed higher activity in the liver. Since glycogen was resynthesized upon refeeding, this eliminated the possibility that glycogen depletion during starvation was due to stress or physical exhaustion after handling by the investigator.

Throughout the experimental starvation period, the body weight of the mudskipper decreased, with a maximum of 12% weight loss after 21 days. Liver lipid reserves were utilized at the onset of fasting but were thereafter resynthesized. Muscle proteins were also metabolized as the fish were visibly thinner. However, no apparent change in protein content expressed as per gram wet weight was detected as the tissue hydration state was maintained constant. The increased degradation of liver and muscle reserves was coupled to an increase in the activities of key gluconeogenic enzymes in the liver (G6Pase, FDPase, PEPCK, MDH and PC). The increase in glucose synthesis was possibly necessary to counteract hypoglycemia brought about by starvation in B. boddaerti.
Whiting migration in the Bristol Channel: a predator‐prey relationship
Authors: Henderson P. A. , Holmes R. H. A.
Published: January 2006

The relationship between whiting, Merlangius merlangus (L.), and the common shrimp, Crangon crangon L., in the Bristol Channel and Severn Estuary was investigated. The whiting population was found to comprise 0‐group juveniles which only remain in the region for about 10 months before moving offshore. While within the estuary, the distribution and abundance of the two species were found to be clearly related. It is hypothesized that the whiting depends on the common shrimp because it is the only abundant prey species in the winter. Both the whiting and shrimp populations were found to not follow any long‐term trend in numbers. It is suggested that the whiting population is stable because it is constrained by shrimp abundance which is, in turn, limited by physical constraints. Similar predator‐prey relationships may be common to many European estuaries.
An attempt to estimate the predatory pressure exerted by the lesser weever, Trachinus vipera Cuvier, in the southern North Sea
Authors: Creutzberg F. , Witte J. IJ.
Published: January 2006

In order to evaluate the impact of the lesser weever on the ecosystem of the southern North Sea, geographical distribution, density, growth, production and food requirements have been estimated. High densities were found on and around the Brown Ridge, an area with high tidal current velocities, medium grain‐size of the sediment and a poor benthic fauna. Growth is restricted to the months of June October. During the winter cessation of growth a considerable loss of weight (about 20%) takes place. Mortality has been estimated by using the average size frequency distribution of all catches made from 1972 to 1984. The resulting convex type of survival curve indicates a high survival rate of the II to IV‐group fishes. The production (estimated with Allen's graphical method) of a population of 100 individuals including all age groups (0‐VI) amounts to 123.7 g AFDW‐year‘. In areas with highest densities, consequently, production amounts to 0.018–0.078 g AFDW‐m2 ‐year‐1. With an assumed transfer efficiency of 10% through the year, food requirements amounts to 0.18–0.78 g AFDW‐m 2 ‐year ‐1. Since the lesser weever feeds mainly on fish (85.6%), almost exclusively on gobies (Pomatoschistus sp.), and with an assumed transfer efficiency of approximately 10%, the indirect predatory pressure exerted by it may amount to 1.6 6.7g AFDW‐m 2.year ‐1. A possible feeding by gobies on pelagic organisms (calanoids, mysids) is discussed.
Gastric evacuation rates and daily ration of piscivorous coho salmon, Oncorhynchus kisutch Walbaum
Authors: Ruggerone G. T.
Published: January 2006

Effects of temperature and meal size on gastric evacuation rates of juvenile coho salmon, Oncorhynchus kisutch, consuming sockeye salmon, O. nerka, fry were examined and used in the estimation of daily meal, daily ration and number of fry consumed by coho in Chignik Lake, Alaska. Evacuation of fry by coho was best described by a negative exponential model (average R2= 0.93). A square root model also provided a good fit (average R2= 0·93), but the y‐intercepts deviated more from the expected value than did the y‐intercepts of the exponential model. The effect of temperature (T, 5–13° C) and meal size (MS, 0·166–0·367 g) on the exponential evacuation rate (re, h‐1) could be described as

image

In the lake, coho fed continuously during the 24‐h period in early June 1986 and 1987. Estimates of daily meal and ration of coho calculated by the Eggers method and the geometric mean of prey weight ranged from 0·224 to 0·435 g (2.1–4.4% body wt) depending on location and year. The Elliott & Persson method provided similar estimates of food consumption, whereas estimates based on the Pennington method and square root evacuation of prey differed from the exponential models. Sockeye fry represented 93% of the total prey weight. The average number of sockeye fry consumed per coho per 24 h, based on the arithmetic mean of prey weight, was 3·0–3·9 fry.
Electrophoretically detectable genetic data for fifteen southern African cichlids
Authors: Van der Bank F. H. , Grant W. S. , Ferreira J. T.
Published: January 2006

Gene products of 40 loci in 15 species of the cichlid genera Chetia, Hemichromis, Oreochromis, Pharynogochromis, Serranochromis and Tilapia were examined by horizontal starch‐gel and vertical polyacrylamide‐gel electrophoresis. Electrophoretic analysis of the loci, using aqueous extracts of brain, eye, gill, heart, kidney, liver, serum, stomach muscle, testis and white muscle, revealed the products of 40 loci for routine analysis. Genetic variation within species was observed at 18 loci and average heterozygosities ranged between 0.021 and 0.047 which is less than previous estimates based on fewer loci and smaller sample sizes for the same species. Interspecific variation exists and can be used to identify the species studied. Gene expression is similar among all species studied.
Sibling recognition in juvenile Arctic charr, Salvelinus alpinus (L.)
Authors: Olsén K. H.
Published: January 2006

Juvenile Arctic charr, Salvelinus alpinus (L.), from two full sibling groups were studied concerning the possible existence of chemical cues with information about kinship. Each full sibling group was divided into two groups with the same number of specimens and placed in two separate aquaria. The division coincided with the start of exogenous feeding. Preference tests were performed about 7 and 10–13 months after the division. Due to the increasing size of experimental fish, two different sizes of apparatus were used. The first series of experiments was performed in a small Y‐maze fluviarium and the second series in the large standard fluviarium. The momentary positions of one fish at a time in the test area were recorded by time‐lapse photography with a 16‐mm film camera and filtered flashlight (no transmittance <670 nm). The fish were given a choice between two water qualities; thus the following comparisons were made: (i) unconditioned water ν. water scented by siblings from the same aquarium; (ii) unconditioned water ν. unfamiliar non‐siblings; (iii) siblings from the same aquarium ν. unfamiliar non‐siblings; (iv) siblings from a separate aquarium ν. unfamiliar non‐siblings; (v) siblings from the same aquarium ν. siblings from a separate aquarium. The test fishes preferred water scented by siblings over non‐siblings, even though the siblings were taken from a separate aquarium. Nevertheless, they were attracted to water scented by unfamiliar non‐siblings in preference to unconditioned water. No preference was shown between chemical cues from siblings taken from the same and a separate aquarium.
Ligula intestinalis(L.) (Cestoda: Pseudophyllidea): plerocercoid‐induced changes in the spleen and pronephros of roach,Rutilus rutilus(L.), and gudgeon,Gobio gobio(L.)
Authors: Taylor M. , Hoole D.
Published: January 2006

The effects of the plerocercoid ofLigula intestinalis(L.) (Cestoda: Pseudophyllidea) on the major lymphoid organs, the spleen and pronephros, of roach,Rutilus rutilus(L.), and gudgeon,Gobio gobio(L.), are described. The spleen of ligulosed roach showed a significant decrease in weight. Differential cell counts suggested this was due to a reduction in erythrocytes, despite significant increases in macrophages and vacuolated granulocytes. The spleen of gudgeon, which consisted almost entirely of erythrocytes, showed a slight reduction in weight in ligulosed fish. In both roach and gudgeon this decrease was independent of parasite burden. Differential cell counts of the pronephros from ligulosed roach revealed a significant decrease in neutrophils and increase in vacuolated granulocytes. In the pronephros of gudgeon, however, cell counts were unaffected by ligulosis. Ultrastructural observations included an apparent disintegration of vacuolated granulocytes and increased pinocytic activity in specialized endothelial cells in the spleens of ligulosed roach. Also, melano‐macrophage centres and melano‐macrophages increased in the spleen of ligulosed roach and gudgeon, respectively. The marked changes in spleen weight and differential cell counts in ligulosed roach and lack of such changes in ligulosed gudgeon correlate with the differential response to the parasite by these two fish species.
Genetic differentiation between freshwater resident and anadromous brown trout, Salmo trutta, within watercourses
Authors: Skaala Ø. , Nævdal G.
Published: January 2006

Freshwater resident and anadromous life history forms of brown trout, Salmo trutta L., sampled from each of three watercourses were analysed for biochemical genetic variation. Ten enzyme systems encoded by a putative 30 loci were analysed. Significant genetic differences were found between the two life history forms in all three watercourses. Further, significant genetic differences were also found between the three anadromous populations analysed, although two of them are separated by a distance along the shore line by less than 2 km. The findings focus on the need to reconsider the conservation and management practice of wild and hatchery‐reared stocks.
Discontinuous distributions of the fish acanthocephalans Pomphorhynchm laevis and Acanthocephalus anguillae in Britain and Ireland: an hypothesis
Authors: Kennedy C. R. , Bates R. M. , Brown A. F.
Published: January 2006

The current distributions of the freshwater fish acanthocephalans Pomphorhynchus laevis and Acanthocephalus anguillae are described and shown to be discontinuous and mutually exclusive, both regionally and locally, in the British Isles. An hypothesis is erected to account for this pattern. It is suggested that as the continental freshwater cyprinids colonized post‐glacial mainland Britain via the eastward‐flowing rivers and the Thames‐Rhine link, they brought with them both species of acanthocephalan. The present, more extensive distribution of P. laevis in the British Isles and Ireland is explained by (1) early formation of a marine strain that colonized the Baltic and North Sea and estuaries of North Sea rivers, (2) later transfers of infected barbel to other English rivers from the R. Thames by man, and (3) transfers to Ireland of infected cyprinids from England by man. Different and restricted availability of preferred definitive and intermediate hosts subsequently resulted in the formation of distinct strains in England and Ireland. The distribution of A. anguillae can be explained by similar anthropogenic influences, but since its definitive and intermediate hosts are more widely available, strain formation has not yet been detected. Competitive interactions between the two parasites in the intestine of the definitive hosts are thought to be responsible for their mutual exclusiveness.
The effects of brief exposure to aromatic hydrocarbons on feeding and avoidance behaviour in coho salmon, Oncorhynchus kisutch
Authors: Purdy J. E.
Published: January 2006

Two experiments determined the effects of exposure to aromatic hydrocarbons on feeding and avoidance behaviour in coho salmon, Oncorhynchus kisutch. Subjects received brief exposure to different concentrations of a mixture of seven aromatic hydrocarbons dissolved in acetone and sea water. Exposure to a low concentration decreased feeding. At a higher level, all fish stopped feeding for 3 days and one fish stopped feeding for 10 days. Salmon exposed only to acetone fed normally. Experiment 2 subjects were trained to avoid electric shock. Exposure to a low level of pollutant caused an initial reduction in avoidance response. Exposure to the high level caused a greater reduction and a longer reaction time to the conditioned stimulus. Results suggested that exposure to these levels of aromatic hydrocarbons could limit a fish's ability to survive.
Further study of the embryonic development of Oreochromis niloticus (Cichlidae, Teleostei) using scanning electron microscopy
Authors: Galman O. R. , Avtalion R. R.
Published: January 2006

The chronology of development of Oreochromis niloticus embryos was examined by scanning electron microscopy (S.E.M.) and the external structures which evolved during the embryonic period were analysed. Twenty‐four stages of embryonic development of this fish at 25°C are described with emphasis on the cleavage phases and morphogenesis of external organs and tissues. Because the development of internal organs could not be observed under S.E.M., the necessary investigation was completed by light microscopy.
Reproductive and growth strategies of the red roach, Rutilus arcasii (Steindachner, 1866), in two contrasting tributaries of the River Duero, Spain
Authors: Rincon P. A. , Lobon‐Cervia J.
Published: January 2006

The life‐histories of red roach were assessed in the R. Moros and the R. Ucero, two contrasting tributaries of the R. Duero. Growth occurred from April to October and Ucero red roach were larger than those in the Moros from their second year onwards. Condition increased with gonad development and abruptly decreased after spawning in both populations. The condition of Ucero fish recovered during the summer, but that of the Moros fish remained low. The same year classes (1980 and 1982) dominated both populations. River Moros red roach spawned in a 4‐week period between the end of April and early June, while the spawning season of Ucero red roach lasted until August. The length to fecundity relationship was similar for both populations, and fecundity and ovum size increased with fish length. The life‐history traits of these red roach populations are discussed in relation to current life‐history theories.
Ultrastructure of the peripheral blood leucocytes of Oreochromis mossambicus
Authors: Doggett T. A. , Harris J. E.
Published: January 2006

Peripheral blood leucocytes were examined for their fine structure and their in vivo response to colloidal carbon particles and bacteria, Aeromonas salmonicida. Four main types of leucocyte were identified: lymphocytes, thrombocytes, monocytes and granulocytes. Previously, two types of granulocyte had been identified but at the electron microscope level a third type could be distinguished in the peripheral blood. Monocytes and the type 1 and type 3 granulocytes were found to be phagocytic.
Mortality and production of 0+ perch, Perca fluviatilis L., in two Scottish lakes
Authors: Treasurer J. W.
Published: January 2006

Mortality of 0+ Eurasian perch was measured directly from the decline in catch in a high‐speed plankton sampler and described by a negative exponential model. A mean mortality of 0.063 day 1 (range=0.020–0.089) was calculated; for 0+ juveniles it was 0.021 day 1. Mean larval production was 0.85–1.30 mg dry weight m−2 day−1 in Loch Kinord and 0.08–0.12 in Loch Davan. Annual production of 0+ juveniles was 1.97–7.55 kg wet weight ha −1 at L. Kinord and 1.01 kg at L. Davan. The contribution of 0+ perch, including the egg stages, to total perch production was 88–96%. Availability of food items on transition to exogenous feeding and through the larval period did not limit survival. Cannibalism by adults accounted for most of larval mortality, and predation by pike and adult perch were responsible for the majority of juvenile losses. The population structure of adult perch, for 12 year classes, was stable at L. Kinord, while year classes at L. Davan exhibited fluctuations in abundance and in two sampling years were eliminated in the first summer. Survival in the eleutheroembryonic phase was variable at L. Davan and observed to be low compared with L. Kinord. It is suggested that this was a result of water turbulence on the exposed and shallow spawning areas at L. Davan.
The maturation of anadromous female Atlantic salmon, Salmo salar L., stocked in a small pond in urban St John's, Newfoundland, Canada
Authors: O'Connell M. F. , Gibson R. J.
Published: January 2006

Anadromous Atlantic salmon swim‐up fry were stocked into a small pond (surface area 4.0 ha; maximum depth 3.6 m; mean depth 1.9m) in urban St John's, Newfoundland, Canada. The outlet from the pond was placed underground about 15 years ago. The growth rate of young salmon in this pond was two to five times as fast as in populations in insular Newfoundland. Females matured after a size at which they should have smolted and emigrated to sea. Growth, fecundity, and egg size of transplanted females are compared with those of the donor stock and with those reported for populations of landlocked salmon in insular Newfoundland. The evolutionary implications of the study are discussed.
Some Spanish cestode fish parasites
Authors: Durán M. L. Sanmartín , Alonso P. Quinteiro , Rodriguez A. , Fernándeez J. A.
Published: January 2006

Cestode fish parasites were studied in 569 fish of 13 species, comprising 72 specimens of Hyperoplus lanceolatus caught between April and July 1987 and 497 other fish caught between December 1986 and March 1987 at 42° 45′ N, 9° 26′ W (Table I).

Bothriocephalus was found for the first time in H. lanceolatus, though its prevalence was very low. The presence of these larvae in a species that forms part of the turbot's Scophthalmus maximus food chain suggests that they may infect the turbot via H. lanceolatus as well as via copepods. Dupond & Gabrion (1986) and Robert et al. (1988)
Cortisol and thyroid hormone responses to acid stress in the brown trout, Salmo trutta L.
Authors: Brown J. A. , Edwards D. , Whitehead C.
Published: January 2006

Individual cannulated brown trout monitored during exposure to acidic water showed increased plasma cortisol after 3 h at pH 4.0 with low (0.05 mm) or high (2.8 mm) calcium (Ca) content, and after 2 days in acidic water with a high Ca content. Most fish did not survive for 2 days in acidic water with a low Ca content. Non‐cannulated fish showed a similar increase in mean plasma cortisol after 2 days in high‐Ca acidic water (pH 4.0–4.6), but not in acidic water of a low Ca content. After 7 days of exposure to acidic water, plasma cortisol appeared to recover when there was a high Ca content but increased 20‐fold when Ca content was low. In cannulated fish severe acid stress resulted in a marked and rapid thyroid response. Plasma thyroxine (T4) was elevated after 3 h exposure to acidic water of both low and high Ca content and remained elevated for 2 days of acid exposure with high Ca. In non‐cannulated fish an increase in mean T4 was apparent only after 7 days in low‐Ca acidic water. Plasma triiodothyronine (T3) levels were not significantly altered by any of the acid regimes. Plasma glucose of cannulated fish was elevated within 3 h of acid‐exposure and remained elevated after 2 days in high‐Ca acidic water.
Seasonal and regional infestation characteristics of three ectoparasites of whiting, Merlangim merlangus L., in the North Sea
Authors: Pilcher M. W. , Whitfield P. J. , Riley J. D.
Published: January 2006

Whiting collected from 36 stations in the North Sea in August 1985 and February 1986 were examined with reference to the prevalence, intensity and microhabitat utilization of three ectoparasites, namely Lernaeocera branchialis (Copepoda: Pennellidae), Clavella adunca (Copepoda: Lernaeopodidae) and Diclidophora merlangi (Monogenea: Polyopisthocotylea). Maximum prevalences and mean intensities, at any one station, for the three parasites were 74,45.48,60% and 1.07,0.56 and 1.30, respectively.

At the stations sampled, infestation levels with L. branchialis and C. adunca were significantly higher in the winter than in the summer, with winter mean parasitic intensities being between five and eight times higher than those in summer. A converse situation applied with D. merlangi, with summer mean intensities being over four times larger than those in winter.

Pooled winter and summer parasitic infestation data, from the 36 stations, enabled large‐scale zoogeographical parasitization patterns to be recognized. Both L. branchialis and C. adunca are rarely seen on whiting in the North Sea north of latitude 56° N. South of this latitude, prevalences and intensities of L. branchialis are higher on the eastern than on the western side of the sampling zone, while those of C. adunca are similar on both sides of the North Sea. D. merlangi's infestation exhibits a striking latitudinal cline in the study area, with prevalences and intensities increasing steadily from south to north.

All three ectoparasites were non‐randomly distributed within the whiting gill and/or buccal cavities and showed marked microhabitat preferences. Possible explanations for the seasonal and geographical variations in the parasitic infestations are discussed.
A meristic, morphometric and biochemical investigation of Atlantic menhaden, Brevoortia tyrannus (Latrobe)
Authors: Epperly S. P.
Published: January 2006

Juvenile Atlantic menhaden, Brevoortia tyrannus, were collected from estuarine waters of the Atlantic coast of the United States. Those collected north of latitude 40°N had lower numbers of total and trunk vertebrae, ventral scutes and interhaemal spines, and shallower heads, smaller eyes, shorter predorsal lengths, and lower frequencies of the fastest allele observed at the transferrin locus than those collected south of Long Island. Although the evidence is still inconclusive, the potential for at least two subpopulations still exists: one which spawns in the spring and early summer and is responsible for the primary recruitment in the northern North Atlantic area, and one which spawns in the autumn and winter and contributes the majority of recruitment in the middle and southern North Atlantic areas of the United States.
Behavioural and growth responses to the intensity of intraspecific social interaction among medaka, Oryzias latipes (Temminck and Schlegel) (Pisces, Cyprinodontidae)
Authors: Ruzzante D. E. , Doyle R. W.
Published: January 2006

When access to food is restricted, faster growing fish may be those whose behaviour is relatively unaffected by the presence of nearby conspecifics. Behavioural experiments were carried out to determine the relation between growth and motor activity levels in crowded and uncrowded conditions, and measures of aversion/attraction to groups of conspecifics. Two experimental groups of Or)‐ius laripes (Temminck and Schlegel) were grown for several weeks in two environments manipulated so as to maximize differences in social interactions. In the high interaction environment (HI), food was provided inside a floating cork ring. In the low interaction environment (LI), food was spread over the container's surface. Fish were measured at the end of the growth period and tested for their activity levels in the presence of conspecifics and for their preference for, or tolerance of crowded conditions. The correlation between motor activity and growth was significantly more positive in the HI environment than in the LI environment. The relationship between preference for crowded conditions and growth was negative for both groups of fish, although less so for HI than for LI. We conclude that artificial selection for faster growth may produce more aggressive fish only under very high levels of forced social interaction (competition), if at all. Under conditions of reduced social interaction, the social‐aversive or socially indifferent fish grow faster.
Plasma levels of gonadotropin and 17α,20β‐dihydroxy‐4‐pregnen‐3‐one in relation to spawning behaviour of rainbow trout, Oncorhynchus mykiss(Walbaum)
Authors: Lilley N. R. , Rouger Y.
Published: January 2006

Manipulation of the opportunity to spawn was used to investigate the relationship between endocrine events, egg viability and spawning behaviour in female rainbow trout. Females were prevented from spawning by isolating them from males and gravel for up to 21 days after ovula‐ tion. Blood samples were taken before pairing with a male, at the onset of nesting activity, and at the completion of spawning. Plasma hormone levels of gonadotropin (GtH) and 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17,2OP) were measured by specific radioimmunoassays. There were no qualitative or quantitative differences in the spawning behaviour of females paired on the day of ovulation or 7. 14, or 21 days after ovulation. There was a general decrease in the viability of eggs with increasing retention times. In females paired on the day of ovulation, or after 7 or 14 days, GtH levels increased with the onset of nesting behaviour and declined as fish reached the post‐spawning condition. By day 21, GtH levels before pairing were significantly higher than prepairing levels in the other three treatment groups, and did not increase at the onset of nesting, or decrease in post‐spawning fish. Plasma 17,20P remained high in prepairing and nesting samples of all four groups and declined to low levels in fish in post‐spawning condition. In females paired on the day of ovulation there was a significant increase in 17,20P from the prepairing to the nesting stage. These results suggest that 17,20P plays a key role in the synchronization of behavioural and maturational events at the time of spawning.
The identification of Pomatoschistus minutus (Pallas) and Pomatoschistus lozanoi (de Buen) (Pisces, Gobiidae)
Authors: Hamerlynck O.
Published: January 2006

Sand gobies areextremely abundant in coastal waters and estuaries. Pomuroschistus lozunoi tends to be overlooked due to identification problems. This paper summarizes the characteristics to distinguish P. lozanoi from P. minutus and presents a new distinctive feature that allows identification of juveniles from 15‐20 mm standard length onward. The known geographic distribution of P. lozanoi is extended northward to 53°30′ N and southward to 40°N on the coast of Europe. In northern Europe P. loxmoi seems better adapted to the estuarine habitat than previously thought.
The disruption of sodium balance in brook charr, Salvelinus fontinalis (Mitchill), by manganese and iron
Authors: Gonzalez R. J. , Grippo R. S. , Dunson W. A.
Published: January 2006

A primary toxic action of manganese to brook charr, Sulvelinusjonfinalis, at concentrations near or above the 96 h LC50 was the disruption of sodium regulation. Body and plasma sodium concentrations of brook charr declined by 52 and 40%, respectively, during exposure to 10.9 mM manganese (in 250 PM CaCI), and all fish died within 36 h. Sodium balance was less severely affected by 2.7 and 5.5 mM manganese. An increase in the external calcium concentration from 0.05 to 1.0 mM raised the LC50 for manganese from 4.9 to 5.8 mM, and a further increase to 2.5 mM calcium almost doubled it to 10.2 mM. An examination of stable manganese uptake by the gills revealed that accumulation was inversely correlated with body sodium concentration (r =−0.77). Radioactive J4Mn entered the bloodstream in low levels and accumulated in the liver. Thus manganese may have systemic effects as well as those attributable to surface binding on the gill. Studies of the mechanism ofdissolved iron toxicity were less conclusive, but it did not appear to involve extensive disruption of sodium balance. There was about a 15% drop in body sodium concentration when the trout were exposed for 48 h to the 96 h LC50 level of iron, but plasma sodium was unaffected. Also, an iron concentration at twice the LC50 did not escalate the loss of body sodium, and increasing the water calcium concentration did not raise the LC50.
A comparative study of the epidermis of the common carp and the three Indian major carp
Authors: Singh S. K. , Mittal A. K.
Published: January 2006

A comparative study has been made of the mucogenic epidermis of the common carp, Cyprinus carpio var. communis, and the three Indian major carps, Catla catla, Labeo rohita and Cirrhina mrigala: on the basis of epidermis structural organization, these species are easily differentiated.

The epithelial cells in the superficial layer, as in most fishes, show secretory activity, evidenced by positive histochemical reactions, which is high in C. carpio var. communis, moderate in C. catla and low in L. rohita and C. mrigala. The epithelial cells in the underlying two or three layers also give positive reactions, though their intensity is relatively weak.

The mucous cells in C. carpio var. communis are distributed in large numbers arranged in several superimposed layers in the outer regions of the epidermis, whereas in C. catla they are fewer in number and are widely separated in the surface layers as well as in the deeper layers of the epidermis; in both species the mucous cells appear rounded, large, and open on the surface by wide pores. In contrast, in L. rohita and C. mrigala the mucous cells are smaller, restricted mainly to the superficial layer, close together in a single row, and open on the surface by narrow pores. The overall density of mucous cells in L. rohita and C. mrigala, as in C. catla, is much lower than in C. carpio var. communis.

In the epidermis of C. carpio var. communis there are a large number of mucous cells, and the few club cells are restricted to the deeper layers. In contrast, in the epidermis of the three Indian major carp the overall density of the mucous cells is much lower and the club cells are very numerous. It is suggested that the high density of club cells compensates an overall low density of mucous cells as an adaptation for an effective defence mechanism.

Increased mucus production in the epidermis of C. carpio var. communis, as evidenced by a large number of mucous cells in outer regions and high secretory activity of superficial layer epithelial cells, is associated with increased precipitation of mud held in suspension, needed as an adaptation to the species’peculiar bottom‐scooping habits.

The varied density of the taste buds in the epidermis of the four carp is associated with their feeding habits.
Age, growth and reproduction of the cyprinid Rutilus lemmingii (Steindachner, 1866) in the River Huebra, Central Spain
Authors: Velasco J. C. , Rincón P. A. , Lobón‐Cerviá J.
Published: January 2006

Age, growth and reproduction of the R. lemmingii population of the River Huebra, Duero basin are analysed. Females dominated older age classes and lived up to 6 years (5+) while males only reached 5 years (4+). The growing season extended from April to September; growth rates were similar for both sexes. 0+ fish condition increased during their first summer and spring. In older fish, condition cycle was related to gonad development and showed some differences between sexes. The number of females reaching maturity at age 1 + almost doubled that of males; females also matured at smaller size. Both fecundity and egg size increased with female length: mean egg counts varied between 974 for 1 + individuals and an estimated 10491 for 5+ fish. Eggs were produced as a single batch, but were released fractionally during April and May.
Isolation of leucocytes from the anterior kidney and spleen of rainbow trout in a self‐generating density gradient
Authors: Congleton J. L. , Greenlee A. R. , Ristow S. S.
Published: January 2006

Separation of leucocytes from tissues and enrichment of specific types of leucocytes are essential first steps in studies of leucocyte function. We describe a simple and rapid method for separating and enriching leucocytes from the anterior kidney and spleen of rainbow trout. Leucocytes were separated on self‐generating density gradients of Sepracell‐MN, a colloidal silica‐based medium. Recovery of leucocytes from the gradients was near 100% and was not affected by procedural variables such as cell suspension: Sepracell‐MN ratio (separation ratio), initial temperature, centrifugation time, or number of cells per gradient. Two bands of leucocytes formed at separation ratios of 1 : 1, 1:1.5, 1:2 and 1 : 3. Recovery of selected leucocyte types could be maximized, and contamination by other cell types reduced, by selection of the appropriate separation ratio and cell band. Recovered leucocytes were responsive in assays of functional capability (adherence, phagocytosis, superoxide anion production). Leucocyte populations that adhered to glass were enriched for macrophages, but some neutrophils and lymphocytes (paricularly spleen lymphocytes) were also adherent. The most abundant leucocytes in the anterior kidney and spleen of the experimental fish were lymphocytes (respectively, 47 and 88%, including thrombocytes), neutrophils (35 and 7%), and macrophages (11 and 3%).
Response of rainbow smelt, Osmerus mordax (Mitchill), eggs to low pH
Authors: Geffen A. J.
Published: January 2006

The eggs of rainbow smelt were incubated at pH c. 4.5, c. 5.5 and control (c. 6.8) for durations of 2–14 days to assess their vulnerability to acid precipitation. These eggs are likely to be exposed to marked pH depressions during their incubation in small streams owing to run‐off from snow melt and spring rains. Survival after 48 h exposure was not related to pH, although longer exposure to low pH significantly decreased survival. The developmental stage at initial exposure was also important in determining survival. Overall egg survival varied from 0–87% at pH c. 4.5,0–89% at pH c. 5.5, and 44–100% at control pH levels, (c. 6.8).
Lysozyme activity in rainbow trout, Oncorhynchus mykiss (Walbaum), stressed by handling, transport and water pollution
Authors: Möck A. , Peters G.
Published: January 2006

Blood lysozyme activity was determined in rainbow trout that were stressed by handling and transport, or suffered from acute ammonia poisoning. To optimize the lysoplate assay, the pH dependence of the lysozyme activity was studied. For serum and kidney lysozyme, the pH optimum was 5.5 to 6.0. Ventilation frequency and plasma glucoseconcentration of the fish were used as stress indicators. Less severely stressful situations, such as 30 min of handling, brought about either a stimulation or a suppression of the lysozyme activity. Strong stressors, such as transport lasting 2 h or acute water pollution, reduced the lysozyme level significantly. The decrease of lysozyme activity due to handling and transport persisted for 24 h, but the activity returned to normal within 2 weeks following confrontation with the stressor.
Seasonal changes in growth and standard metabolic rate of juvenile perch, Perca fluviatilis L.
Authors: Karaås P.
Published: January 2006

The maximum growth rate of juvenile perch, PercaJuviatilis L., at different constant temperatures and in naturally changing day‐lengths was studied in the laboratory. Standard metabolic rate was studied in starvation experiments at constant temperatures under short‐ and long‐day conditions. Growth occurred in temperatures above 8 to 10°C. In winter, from mid‐October until mid‐April, maximal growth was considerably reduced and was relatively slow but constant. The standard metabolic rate was reduced c. 50% under short‐day conditions. The seasonal change in metabolic rates, presumably controlled by an endogenous rhythm, was considered to be an adaptation to low food availability during the short winter days.
Tolerance, behaviour and oxygen consumption in the sand goby, Pomatoschistus minutus (Pallas), exposed to hypoxia
Authors: Petersen J. K. , Petersen G. I.
Published: January 2006

Behavioural and metabolic reactions of Pomatoschistus minutus (Pallas) exposed to various degrees of hypoxia were studied. At 15°C and 20‰ mortality was 50% at 15.2% oxygen saturation. Avoidance and oxygen saturation showed a linear inverse relationship. At levels lower than 60% saturation increased activity occurred; avoidance was significant at 30% saturation. Active, routine and standard MO2 correlated linearly with weight at 6 and 15°C (salinity = 19‰). During hypoxia at 15°C routine MO2 rose significantly at 60–50% and 40–30% saturation expressed either as MO2 during longer periods at night or MO2 at shorter intervals during the day. Standard MO2 was unaffected by hypoxia at 15°C. Haemoglobin concentration was significantly increased when P. minutus was acclimatized to 35% saturation.
Predation on adult Atlantic salmon, Salmo salar L., by otters, Lutra lutra (L.), within the River Dee system, Aberdeenshire, Scotland
Authors: Carss D. N. , Kruuk H. , Conroy J. W. H.
Published: January 2006

Predation on adult salmon, Salmo salur L., by otters, Lurra lutra (L.), varied seasonally on the R. Dee, Aberdeenshire, Scotland, being highest during the spawning season in winter. Predation is described for some tributaries of the river. Male fish were caught by otters more often than females, and it is suggested that they were most vulnerable during their extensive excursions up and down stream, particularly as they negotiated shallow riffles. Otters appeared to prey upon healthy fish rather than those infested with Saprolegnia sp. but there was no difference in the size, freshwater‐ or sea‐age offish killed by otterscompared with ‘kelts’ which had died non‐violently. At least some of the otters obtained most of their daily food requirements by catching a single salmon per night.

Considerable numbers of adult salmon may be killed by otters during the spawning period but it is suggested that, because most are males, this is unlikely to affect the breeding success of the salmon population. Most predation occurs outside the fishing season and so is unlikely to reduce the numbers of salmon caught by anglers.
Tidal movements of shallow water fishes in Kuwait Bay
Authors: Wright J. M. , Clayton D. A. , Bishop J. M.
Published: January 2006

The intertidal migrations of shallow water fishes in Kuwait Bay were studied during two 24 h periods using an otter trawl. Most species wereconcentrated at a location corresponding to Low Low Water mark. At the other tidal levels some fishes migrated with the tide to High High Water mark through a horizontal distance of up to 2 km. Any effect of day and night on the catch was masked by the effect of tidal condition.

Leiognarhus decorus (de Vis) was typically concentrated at Low Water but a proportion of the population followed the rising tide toward the shore. There was a die1 effect whichmay have been due to fish moving to shallower water at night compared with the day. Length‐frequency distribution changed slightly with tidal state so that larger fish were not captured at High Water during the day. Of the fishes captured at high tide, the largest individuals of L. decorus were captured at a depth of 2.0 m deep. Solea elongata Day did not migrate with tidal fluctuations and was captured in large numbers only at Low Water. Arius tenuispinis Day was captured in shoals at or around Low Water.
Modelling of unexploited and exploited populations of eels, Anguilla anguilla (L.), in the Thames Estuary
Authors: Naismith I. A. , Knights B.
Published: January 2006

Eels were fyke‐netted in different zones of the Thames Estuary at various times of year and subsamples sexed, aged and stomachcontentsexamined. Instantaneous mortality coefficients (Z) were calculated for each 3 cm length class for eels > 30 cm and used to construct a compartmental model to assess effects of natural and fishing mortality and migration on different life stages of males and females. Growth rates were good and fishing mortality effects low and masked by effects of emigration/immigration (and, possibly, local migrations). Density‐dependent mortality appeared to be having minor effects. Males dominate freshwater sites, females the more saline zone and possible implications of food availability and density are discussed. It is concluded the stock is not being over‐exploited but that elver recruitment is relatively low. Means of increasing exploitation are discussed, as are ways of increasing production of females to enhance elver recruitment to the Thames and other European rivers.
A culture system for the maintenance and proliferation of shark and sting ray immunocytes
Authors: Grogan E. D. , Lund R.
Published: January 2006

A method designed to support the in vitro maintenance and proliferation of elasmobranch peripheral blood leucocytes (PBLs) has been developed. This method includes protocols for leucocyte isolation, the preparation of media, and culturing conditions. Leucocytes were isolated from whole blood using a Ficoll‐hypaque density gradient followed by nylon wool filtration. Recovered cells were washed and incubated at a density of 0.054 × 106 cells per well of a microtitre plate using a novel medium designed for shark cells. Incubation was carried out at 17 and 37° C. These media represent a modification of RPMI1640 or DMEM to account for isotonic and isoosmotic differences between mammalian and elasmobranch blood via the addition of trimethylamine‐N‐oxide, urea and sodium chloride to the RPMI or DMEM.
Differences in growth between maturing and non‐maturing male Atlantic salmon, Salmo salar L., parr
Authors: Rowe D. K. , Thorpe J. E.
Published: January 2006

Sibling male Atlantic salmon parr that matured tended to be the larger fish in January, but their monthly specific growth rates between January and July did not differ from those of non‐maturing fish. Maturing fish had lower condition factors in March, but greater increases in condition factor during April, exceeding those of non‐maturing males by May. In maturing males, feeding rates between July and September, and specific growth rates in August and September, were lower than those of immature fish. Consequently, the mean size of immatures equalled or exceeded that of maturing males by October. Maturation rates were strongly correlated with increases in mean condition factor only during April.
Preference of Tilapia rendalli (Boulenger) for some species of aquatic plants
Authors: Chifamba P. C.
Published: January 2006

Preference of juvenile red‐breasted bream, Tilapia rendalli (Boulenger), for the macrophytes Ceratophyllum demersum L., Lagarosiphon ilicifolius (Oberm), Najas pectinata (Magnus) and Valisneria aethiopica (Frenzl) was determined. Fish were offered a mixture of the four macrophytes in equal quantities to determine selection. Preference was shown for V. aethiopica, whilst C. demersum was least selected. This preference order was checked by examination of stomach contents of fish from the same population in the wild and the differences are discussed.
Small marine pelagic fish and the threat of fishing; are they endangered?
Authors: Beverton R. J. H.
Published: January 2006

Evidence of the collapse and recovery of major marine fisheries for pelagic fish species is reviewed, distinguishing the influence of fishing compared with natural (environmental) effects. In one only of the best documented cases (Icelandic spring‐spawning herring) has the stock failed to reappear, after 20 years. Several others, e.g. California sardine, have persisted at 1/000th or possibly less of their peak size for some years before beginning to recover. Fishing has been the main cause of collapse in most but not all cases, due initially to the escalation of catchability as stock size decreases–a phenomenon characteristic of fisheries for pelagic species due to their shoaling habit, ease of detection and vulnerability to modern fishing methods. It is concluded that although the threat of fishing to the continuity of the species is remote, excessive depletion (although avoidable by firm and timely management) is potentially able to cause temporary disappearance of local stock and disruption of the ecosystem.
Habitat alteration and its effects on native fishes in the upper Tennessee River system, east‐central U.S.A.
Authors: Neves R. J. , Angermeier P. L.
Published: January 2006

The upper Tennessee River drainage, which includes portions of the States of Virginia, North Carolina, and Tennessee, supports an exceptionally diverse fish fauna. Recent reductions in abundance and geographic ranges of several freshwater fishes have promulgated the imposition of protective measures for about 115 species among the three states, with nearly half of those species occurring in the upper Tennessee River. Most protected species are darters (Percidae: Etheostomatinae) or minnows (Cyprinidae), and are typically small, benthic invertivores. Major impacts on the fish fauna have resulted from dams, introduced species, toxic spills, mining and agriculture. An important cumulative effect of these impacts is fragmentation of the watershed; nearly 40% of the riverine habitat in major tributaries is either impounded or altered by tailwater discharges. The isolation and stress imposed on tributaries of the river have caused and will continue to cause extirpations of fishes, mussels and other aquatic fauna. Numerous federal, state, and private organizations are co‐operating in efforts to protect rare species and habitats, improve agricultural and coal‐producing practices, and enforce regulations for industrial and municipal effluents.
The conservation and status of threatened fishes in southern Africa
Authors: Skelton P. H.
Published: January 2006

The conservation status of 24 threatened freshwater fishes and seven estuarine fishes from southern Africa is discussed against the background of natural and anthropogenic environmental factors. The majority of threatened species are endemic temperate forms with restricted ranges. Major threats include introduced alien fishes and a wide spectrum of environmentally destructive causes. Research on threatened species includes distribution surveys, biological and ecological studies and methods of artificial propagation. Long‐term remedies based on ecosystem conservation are also being promoted. The perceptions and attitudes of nature conservation authorities are adjusting to the new challenges offish conservation. The number of threatened fishes in Africa is likely to increase in the face of escalating problems of habitat destruction and degradation.
Sturgeons (Pisces: Acipenseridae); threats and prospects
Authors: Rochard E. , Castelnaud G. , Lepage M.
Published: January 2006

Life histories of 24 species of sturgeons are briefly summarized and threats to their existence are reviewed. The most important of these are fishing and physical disturbance of rivers (barriers; fluctuating water levels; gravel extraction). Conservation measures to limit and compensate for these impacts are reviewed. In Europe the common sturgeon, Acipenser sturio, is an endangered species; it has been the object of a conservation programme in France since 1982.