bluuebunny/crossref_metadata_2025 huggingface dataset:
In vivo and in vitro effects of oestradiol‐17β on lipid metabolism in Notemigonus crysoleucas
Authors: De Vlaming V. L. , Shing J. , Paquette G. , Vuchs R.
Published: January 2006

The effects of oestradiol‐17β on the gonosornatic index, liver size, hepatic and body lipid levels in the cyprinid teleost, Notemigonus crysoleucas, were investigated. Administration of oestradiol to female TV. crysoleucas during the gonadal preparatory and prespawning seasons stimulates increases in ovarian size. During the early spawning season oestradiol therapy results in a reduction of ovarian gonosomatic index. Oestrogen treatment of males causes a suppression of testicular growth. In female fish exposed to long (15‐5L/8‐5D) or intermediate (12L/12D) photoperiods oestradiol increases body fat reserves. At short photoperiods (9L/15D) oestrogen treatment of females results in body fat store depletion Low doses deplete and high doses of oestradiol increase body lipid reserves in male fish. The hepatosomic index increases in both male and female fish following oestrogen treatment. Oestradiol therapy during the gonadal preparatory season, but not during the prespawning season, increases total liver lipids. The in vitro effects of oestradiol on liver lipid and carbohydrate metabolism were also examined. Under the conditions used in these experiments, lipid depletion was observed in liver slices incubated with or without oestradiol. Pretreatment of fish with oestradiol before liver tissue was removed drastically reduced in vitro lipid depletion. Oestradiol retards the gluconeogenesis and glycogenesis seen in liver slices incubated in a hormone‐free medium.
The effect of temperature on routine metabolism in Tilapia rendalli boulenger
Authors: Caulton M. S.
Published: January 2006

Using a continuous flow respirometer it was shown that young Tilapia rendalli had three distinct phases of oxygen consumption over the temperature range of 17–40° C. In the first phase (17–28° C) the metabolic energy demand followed the normal logarithmic increase with increasing temperature. Between 28 and 37° C the increased oxygen uptake was suppressed and showed a relatively small increase with increasing temperature. This feature was believed to be a significant energy saving function important to the growth of these fish which feed in the warm eulitoral margins of lakes during the day. The final phase shows a return to the original logarithmic increase in oxygen consumption. These results were related to, and compared with, actual changes in biomass at various temperatures and the theoretical and actual biomass changes were found to compare favourably.
Variation in the susceptibility of sockeye salmon Oncorhynchus nerka to infectious haemopoietic necrosis virus
Authors: Amend Donald F. , Nelson John R.
Published: January 2006

Each of 16 mature female sockeye salmon Oncorhynchus nerka from two river drainages were spawned with individual males, and the progeny from each pair were later challenged with virulent infectious haematopoietic necrosis (IHN) virus. At each of 4 monthly challenges, distinct differences were detected in the susceptibility of the fish to IHN from each family. Average percentage mortality was 98 or more in highly susceptible families, in families of intermediate susceptibility, 85 and in resistant families, 52. Furthermore, the mean time to death was only 9.8 days for fish from the susceptible families but 17.9 days for fish from the more resistant families. These results were similar at each monthly challenge. Challenging the fish at various virus‐dosage levels did not change total mortality, but high dosages hastened the onset of mortality. A genetic basis for resistance is proposed to explain these results.
Growth, survival and production of juvenile salmon and trout in a Scottish stream, 1966–75
Authors: Egglishaw Henry J. , Shackley P. E.
Published: January 2006

Investigations of the growth, survival and production of young salmon Salmo salar, brown trout and sea trout S. trutta in sections of a stream in Scotland were made during 1966–75. At the end of the growing season, in autumn, the size of the 0+ salmon ranged from a mean weight of 1.12 g in 1966 to 2.82 g in 1973, and the size of the 0+ trout ranged from a mean of 2.20 g in 1966 to 3.56 g (68.0 mm) in 1974. Growth rates of 0+ salmon between July to September were similar from year to year, as was the case with the 0+ trout. The greater size attained in their first year by trout, resulted from the longer feeding season, provided by earlier emergence of fry and ability to continue growing in colder weather in autumn. The lengths attained by 0+ salmon and 0+ trout in September were related to the population densities of 0+ salmon and the number of days above 0° C from 1 December. There was no discernible relationship between lengths of 0+ trout and the population densities of 0+ trout. Salmon and trout lost weight during the winter, which was made up by April. The densities of 0+ salmon in June varied between 2–12m –2. Rates of decrease of the population densities in their first year were related to their densities at the beginning of the season, and, more closely, to the densities of salmon and trout combined. At the end of the second year's growth there were between 0.06 and 0.25 salmon m –2. Size of the trout populations varied less from year to year than those of salmon. The life of a year class of salmon and trout could be divided into several stages characterized by different rates of decrease of the population.
A method for assessing factors influencing‘false check’formation in fish scales
Authors: Ottaway Elisabeth M. , Simkiss K.
Published: January 2006

Scales are widely used to determine both the growth rates and the age of fish. Their use in this method of scale reading is however complicated by the occurrence of false checks. It has been difficult to investigate the particular environmental factors that normally cause these interruptions in growth because it usually takes many weeks before a check can be detected and the growing scale is a complex system. A technique has therefore been devised in which a scale is isolated from the fish and used to measure its metabolism of radioactive glycine. This gives a measure of protein synthesis which correlates well with the normal growth of the scale and of the whole fish. It is, however, a measurement of the‘instantaneous growth rate‘of the fish instead of one compounded over a long period of time and it thus opens up the possibility of investigating specific environmental factors that might cause changes in growth. The effects of handling, low oxygen levels, starvation, light and temperature changes have been studied by this technique. It has been shown that handling has the most marked effect but that oxygen levels and starvation also have direct effects that could induce false checks.
Tissue depletion and energy utilisation during routine metabolism by sub‐adult Tilapia rendalli boulenger
Authors: Caulton M. S.
Published: January 2006

The amount of fat and protein used by young Tilapia rendalli during starvation can be quantitatively assessed and correlated to the condition of the fish. It was shown that fish in good condition used fat in preference to protein during catabolism, irrespective of the time period of starvation, but this rapidly reversed as condition declined and fish in medium and poor condition utilised more protein than fat to maintain routine metabolism. The amount of energy required during routine metabolism was not affected by the ratio of fat to protein used and a mean energy requirement for these fish (varying between 40 and 60 g in mass) was estimated as 45.03 J g‐1d‐1 at 23°C. This estimate of routine metabolic energy requirement can be equated to oxygen consumption using an oxy‐energy coefficient of 13.68 J mg O2‐1.
The dynamics of infection of Diphyllobothrium dendriticum (Nitzsch) and D. ditremum (Creplin) in the char Salvelinus alpinus (L.) in Sweden
Authors: Henricson Jan
Published: January 2006

A total of 654 char, Salvelinus alpinus (L.), from Lake Bjellojaure, Sweden, were examined for plerocercoids of Diphyllobothrium dendriticum (Nitzsch, 1824) and D. ditremum (Creplin, 1825) from September 1969 to December 1974. Plankton samples showed that the dominating copepod species in the lake were Eudiaptomus graciloides (Lilljeborg), Cyclops scutifer Sars and Heterocope appendiculata Sars. E. graciloides passed the winter as adults and C. scutifer as copepodids while H. appendiculata was restricted to a short period in the summer. Copepods occurred in the stomachs in September‐October and to a certain extent in April‐May, but only cyclopids and Heterocope sp. were found. C. scutifer is proposed to be the main first intermediate host of both D. dendriticum and D. ditremum. The potential final hosts were thecommon gull, Larus canus L., for D. dendriticum and the black‐throated diver, Gavia arctica (L.), for D. ditremum. One common gull was experimentally successfully infected with plerocercoids of D. dendriticum. The parasites showed no seasonal cycle in incidence of infection.
Relationships between dietary sodium chloride, food intake and food conversion in the rainbow trout
Authors: MacLeod M. G.
Published: January 2006

The addition of up to 8.5 % sodium chloride to the diet of rainbow trout Salmo gairdneri had no significant effect on either food intake or food conversion efficiency. Over a range of rations from 4 % to 38 % of dry weight per week, there was a rectilinear relationship between ration and growth rate. The weight maintenance requirement and rate of weight loss during fasting were estimated from this relationship. Food conversion efficiency (K) increased from 0.00 at 4% dry weight per week food intake (x) to 0.19 at 38%, according to the equation K=0.21‐0.77/x.
Observations on effects of feeding level on growth and reproduction in haddock, Melanogrammus aeglefinus (L.) in captivity
Authors: Hislop J. R. G. , Robb A. P. , Gauld J. A.
Published: January 2006

Individual haddock, Melanogrammus aeglefinus (L.) were maintained at different feeding levels in an aquarium from November until the completion of spawning. The mean duration of spawning was 33.2 days (range 19–59) during which an average of 16.6 (range 10–25) batches of eggs were produced. The size and dry weight of the eggs declined during the spawning period. Egg production and feeding level were correlated positively. There was some suggestion that when female haddock received low rations (< 5 kcal day‐1) a lower proportion spawned, and the dry weights of the eggs were lower compared with females on high rations (> 13 kcal day ‐1). The relation between daily growth in wet weight, g, and daily surplus energy intake, kcal, was: G=(0.295E)— 0.328. When food energy is restricted, haddock appear to achieve a balance between somatic growth and reproduction.
The importance of habitat temperatures for growth in the tropical cichlid Tilapia rendalli Boulenger
Authors: Caulton M. S.
Published: January 2006

Like many cichlids living in shallow tropical freshwater systems of Africa, Tilapia rendalli exhibit a marked daily movement into warm shallow water during the day and return to cooler, deeper water at night. Such movements have an important impact on the growth of juvenile fish. Growth is enhanced by this movement and is predicted to be optimal if the fish occupy water with a temperature of 30°C during the day but retire to nocturnal habitats with temperatures of 18°C. The reasons for this phenomenon are discussed using a bio‐energetic model incorporating measurements of feeding intensity, metabolic energy demands and assimilation efficiencies at temperatures ranging from 18°C—3°C and the ecological implications discussed using examples from natural systems.
Bacteriological aspects of fin erosion in mullet exposed to crude oil
Authors: Giles Robert C. , Brown Lewis R. , Douglas Minchew C.
Published: January 2006

An investigation was undertaken to determine the effect of two types of crude oil on mullet (Mugil cephalus). The data presented in this report establishes a relationship between the exposure of the mullet to crude oils and the outbreak of fin rot. The data also indicates that the diversity of the microflora on the exterior of the mullet was reduced from 5‐6 to 1‐2 colonial types, one of which was consistently a species of the genus Vibrio.
Protein yolk synthesis in Blennius pholis L.
Authors: Shackley S. E. , King P. E.
Published: January 2006

Acrylamide gel electrophoresis indicates the presence of a group of proteins in the blood serum and liver of the female fish which are probably responsible for the accumulation of the proteid yolk in the ovary. Immunological tests confirm that these high molecular weight proteins are the protein yolk precursors synthesized in the female liver and transported by the blood serum to the ovary where they accumulate in the developing oocytes.
Investigation on carp, Cyprinus carpio L. gynogenesis
Authors: Nagy A. , Rajki K. , Horvárth L. , Csárnyi V.
Published: January 2006

A reliable method for gynogenetic mass‐production has been developed in carp (Cyprinus carpio L.). The effect of different cold shock treatments applied after fertilization were examined. The yield of viable diploid gynogenetic animals could be significantly increased when the cold shock was applied 5 min or 15 min after fertilization. A negative correlation has been found between the effectiveness of these two treatments, so both were used on separate batches of eggs. By means of gynogenesis, the crossover frequency and map distance of the transferrin locus have been determined. Successful pilot experiments were made on grass carp (Ctenopharyngodon idella Val.) and sheatfish (Silurus glanis L.) with respect to gynogenetic mass production.
Accumulation of heavy metals in rainbow trout Salmo gairdneri (Richardson) maintained on a diet containing activated sewage sludge
Authors: Singh S. M. , Ferns Peter N.
Published: January 2006

Rainbow trout were fed for 10 weeks with a nutritionally balanced diet containing 30% by weight of activated sewage sludge. The whole body concentrations of nine heavy metals (Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb), together with four major cations (Ca, Mg, Na, K) were determined at the beginning and end of the experiment and at three intermediate stages. Fish fed on the diet containing sewage sludge had significantly elevated levels of Cr, Fe, Ni, Pb and reduced levels of Na and K compared with controls, though the values obtained for all groups fell within the range reported for uncontaminated fish. The Ni and Zn showed a marked increase towards the end of the experiment, suggesting that they might have continued to rise after 70 days.
Effects of dilution and temperature of analysis on blood serum values in rainbow trout, Salmo gairdneri
Authors: Warner M. C. , Diehl S. A. , Tomb A. M.
Published: January 2006

Albumin, cholesterol, glucose, inorganic phosphorus, and total protein analyses were not affected by temperatures between 20 and 38°C nor by dilution with either 0.65% or 0.85% NaCl. Additionally, blood urea nitrogen, calcium and creatinine were unaffected by dilution. Alkaline phosphotase, cholinesterase, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, α‐hydroxybutyrate dehydrogenase, lactic dehydrogenase, and phosphohexose isomerase were all affected by temperature. Results of dilution tests were generally inconclusive, while results of enzymatic reactions indicate that reaction temperatures must be closely controlled to produce comparable results.
The reproductive biology of the dab Limanda limanda (L.) in the North Sea: gonosomatic index, hepatosomatic index and condition factor
Authors: Htun‐Han M.
Published: January 2006

Measurements have been made of the annual cyclical changes in gonosomatic index (GSI), hepatosomatic index (HSI) and condition factor (K) in male and female dab Limanda limanda (L.). There is a direct correlation between HSI and K, and an inverse correlation of these factors to GSI but with a three month lag. It was also found that the lower (‘ventral’) ovaries were invariably heavier than the upper (‘dorsal’) ovaries at all times, and a similar relationship was found in testes prior to and during the spawning season.
Studies of the ecology of fish populations in the Rye Meads sewage effluent lagoons
Authors: White R. W. G. , Williams W. P.
Published: January 2006

The ecology of populations of roach, chub and perch in shallow lagoons forming part of a sewage works was studied over a period of two years. The fish were netted, identified, measured and scales taken for ageing, except in the case of perch of which a limited number were killed and their opercular bones collected. The chub and perch grew faster than those from other waters and the growth rate of the roach equalled that of the best European populations. Breeding success was irregular, particularly with the chub, and a relatively low population density and the high potential productivity of the lagoons could explain the rapid growth rate.
Some histopathological effects of Aroclor 1254 on the liver and gonads of rainbow trout, Salmo gairdneri and carp, Cyprinus carpio
Authors: Sivarajah K. , Franklin C. S. , Williams W. P.
Published: January 2006

Sexually mature ♂ and ♀ rainbow trout (Salmo gairdneri Richardson) and carp (Cyprinus carpio L.) were injected intraperitoneally with Aroclor 1254 (25 mg kg−1 body weight in 1 ml of arachis oil) once weekly for four weeks. Arachis oil was used as the control. At the end of the fourth week, samples of the liver, testis and ovary were taken from treated and control fish and examined by light and electron microscopy. The light microscope study indicated that there was general vacuolation of the hepatocytes of trout but not carp; fragmentation of the developing oocytes but no observable changes in the testis. Electron microscopy study showed that there was enlargement of the rough endoplasmic reticulum of the hepatocytes, some damage to spermatozoa and proliferation of the smooth endo‐ plasmic reticulum of the oocytes.
Effects of 6‐hydroxydopamine and 5‐hydroxydopamine onlthe teleost melanophores innervation
Authors: Junqueira L.C.U. , Salles L. M. M.
Published: January 2006

Intraperitoneal injections of 6‐OH‐dopamine (80 mg kg−l) promote, in toad fish, killifish, lsummer and winter flounders, a darkening of their colour and loss of capacity to adapt tolthe colour of the background. This condition persisted for three weeks after which thelanimals gradually returned to normal. The study of the skin of 6‐hydroxydopamineltreated killifish showed degenerative lesions in the fine nerves and synapses of its melanophores, 124 h after the administration of the drug. These lesions progressed and 4 days later, lno synaptic structures could be detected in these cells. This condition persisted up to thel20th day. These results suggest that melanophores have a single monoaminergic innervaion.
Fine structure of the spermatozoon of the viviparous teleost, Cymatogaster aggregata
Authors: Gardiner D. M.
Published: January 2006

The approximately 50 μm long sperm of Cymatoguster aggregata is composed of an elongate head (4 μm), an elongate mitochondria1 midpiece (3.5 μm) and a tail flagellum (roughly 40 μm). The sperm lacks an acrosome. Contained within depressions on one surface of the compressed head are a proximal centriole and a distal centriole separated by an electron dense, intercentriolar body. The anterior portion of the tail flagellum originates at the basal body (distal centriole) and is contained within an extracellular, flagellar tunnel within the mitochondria1 midpiece. The morphological similarity of C. uggregutu sperm to sperm of other internally fertilizing fishes supports the hypothesis that spermatozoan morphology is related to the mode of fertilization and that an elongate head and midpiece are specializations for internal fertilization.
Genetic control of melanophore ultrastructure in Poecilia reticulata
Authors: Nayudu P. L. , Hunter C. R.
Published: January 2006

A melanic mutant form, Nigrocaudatus II, of the guppyfish Poecilia reticulata has been found to have a melanophore distribution different from, and a melanosome size significantly larger than, the wild‐type guppyfish. This is the first observation of differences in melanosome size for a teleost fish and the first for a genetically known colour variant in lower vertebrates.
Vascular effects of acetylcholine, catecholamines and detergents on isolated perfused gills of pink salmon, Oncorhynchus gorbuscha coho salmon, O. kisutch and chum salmon, O. keta
Authors: Bolis L. , Rankin J. C.
Published: January 2006

Acetylcholine caused vasoconstriction whilst adrenaline and isoprenaline caused vasodilation in isolated perfused Pacific salmon gills. The detergent LAS produced concentration dependent vasodilation when present in the perfusate in concentrations of 0.6 to 3 mg 1−1. The effect of LAS was partly blocked by propranalol suggesting the involvement of β‐adrenergic receptors. The maximum responses obtained with acetylcholine, adrenaline or LAS were all much greater in sea water or pre‐spawning freshwater fish than in spawning fish.
The histology of the excretory kidney of the paddlefish, Polyodon spathula
Authors: Georgi T. A. , Beedle Dennis
Published: January 2006

Kidney tissue from the freshwater chondrostean fish, Polyodon spathula, was examined by light microscopy. P. spathula has a glomerular excretory kidney. The tubule leading from the glomerulus, based on a variety of stain reactions, is composed of two major cell types. Also based on stain reactions, it appears that ion reabsorption, hence conservation, occurs in distal portions of the tubules. Also observed were stain reactions of arteriole walls, similar to renin producing cells in other vertebrates.
Gut ph and digestive strategies in estuarine grey mullet (Mugilidae) and tilapia (Cichlidae)
Authors: Payne A. I.
Published: January 2006

Tilapia guineensis, which feeds on leafy material, and Sarotherodon melanothron, which utilizes blue‐green algae, were both capable of producing a pH 2 or less in the stomach which could contribute to the lysis and digestion of blue‐green algae and bacteria. Of the grey mullets investigated, Liza falcipinnis had a gastric pH 3.3–4.5, which may not be low enough to cause cell lysis, whilst Liza dumerili, Mugil cephalus and Mugil curema all had stomach, caecal and intestinal pH's of 7–8.5. Grey mullet appear to have a different digestive strategy to tilapia and may rely upon the establishment of a ‘colloid mill’ in the stomach.
Cadmium uptake by rainbow trout, Salmo gairdneri eggs and alevins
Authors: Beattie J. H. , Pascoe D.
Published: January 2006

The uptake of cadmium by eggs and alevins of rainbow trout from water concentrations of between 0.01 and 50.0 mg Cd 1−1 was investigated. The cadmium content of eggs and alevins increased with time and with exposure concentration. Lower cadmium levels were detected in alevins than in eggs. Most of the cadmium (98%) in the eggs was found to be associated with the egg membrane or chorion. This explains the considerable reduction in cadmium concentration observed in alevins after hatching. Alevins hatching from eggs which had been exposed to cadmium survived longer in cadmium than alevins not exposed as eggs. This suggests that the pretreatment of eggs with cadmium serves some protective function. Behavioural and pathological signs of cadmium poisoning such as erratic swimming and blood clotting in alevins were observed.
The use of infra‐red light and closed circuit TV to validate records from automatic fish counters*
Authors: Beach M. H.
Published: January 2006

Infra‐red light was used to provide ‘dark’ illumination for a TV surveillance system to check the performance of an automatic migratory fish counter. The transmission characteristics of water and infra‐red filters was examined together with the response of TV camera tubes and fish to radiation at infra‐red wavelengths.
Food and feeding ecology of piscivorous fishes at Lake St Lucia, Zululand
Authors: Whitfield A. K. , Blaber S. J. M.
Published: January 2006

The food and feeding ecology of piscivorous fish in Lake St Lucia was monitored for two years. Piscivorous fishes feed predominantly on the planktivorous Gilchristella aestuarius and Thryssa vitrirostris but a wide range of prey species was recorded. Numbers of the predominant piscivores, Argyrosomus hololepidotus and Elops machnata, in an area appear to be related to the densities of their major prey, T. vitrirostris and G. aestuarius. Large piscivorous fishes are restricted to the deeper portions of the lake, whereas small piscivores such as Johnius belengerii and Terapon jarbua feed predominantly on small fishes in the littoral zone. The highly significant correlation between the composition of prey fish species in the lake and prey fish species in the diet of piscivorous fishes, indicates that piscivores are feeding in a density dependent manner. However, factors such as habitat, fish size and swimming speed of prey species are shown to be important in prey selection. Juvenile fish of species such as Sarotherodon mossambicus, Liza macrolepis and Acanthopagrus berda remain in shallow marginal areas, thus avoiding large piscivorous fishes. However by frequenting shallow areas these species become vulnerable to bird predators, especially egrets and herons.
The effects of Lernaeocera branchialis on the Merlangius merlangus population in the Medway Estuary
Authors: van den Broek W. L. F.
Published: January 2006

Whiting entering estuarine waters during autumn are largely free from the copepod Lernaeocera branchialis (L.). Infection soon follows and, between 1973 and 1975, an average 40.4% whiting were infected. The parasite's effects on fish weight over this period are assessed and, in a separate study, its effects on the host's lipid biochemistry determined. Mature adults of L. branchialis caused a significant reduction in body weight. Liver lipid content was also lower in these individuals, by more than 50%. Phospholipid levels were lower but cholesterol readings were greater in infected fish. Fatty acid composition of liver lipids appeared unaffected.
Depth equilibration of a shallow‐water cichlid fish
Authors: Hill B. J. , Ribbink A. J.
Published: January 2006

The cichlid Melanochromis exasperatus has a natural distribution which is restricted to a single island in Lake Malawi, Africa. Diving observations indicated that it does not occur below 4.5 m depth. Measurements of depth equilibration in a pressure tank showed that males can equilibrate to a depth of 25 m and females to 18 m. Mean maximum sustained rate of depth equilibration was 2 m day−1. M. exasperatus survived a pressure decrease of 40% every 12 h from the maximum equilibration depth to the surface. The fish swim actively during the day but rest on the bottom at night when they are equilibrated to a depth 1 m deeper than ambient. Reduced activity at night is reflected in a drop in oxygen consumption to nearly half of the daytime active value.
Long‐term survey data (1965‐1972) on the occurrence of Anisakis larvae (Nematoda: Ascaridida) in herring, Clupea harengus L., from the North Sea
Authors: van Banning Paul , Becker Herman B.
Published: January 2006

The occurrence of larval Anisakis in North Sea herring was examined during the period 1965‐1972 using a sampling method which yielded comparable data for all eight years. Data on abundance of infestation in several herring stocks pointed to remarkable fluctuations over the study period with an increase in the period 1966‐1968 followed by a decrease in the period 1968‐1972. Of various hypotheses that may explain this situation, it is concluded that changes in the migration behaviour of the herring may be responsible. Other data and statistics are discussed with special reference to variations in infestation level in different samples and to the occurrence of adult nematodes in marine mammals.
Cells, proteins, and certain physical‐chemical properties of brook trout (Salvelinus fontinalis) blood
Authors: Christensen G. M. , Fiandt James T. , Poeschl Barbara A.
Published: January 2006

Laboratory brook trout were used to evaluate, refine, or develop biochemical procedures for the analysis of fish blood. Analytical values were obtained for the following blood properties: total and differential leucocytes and erythrocytes; erythrocyte and plasma proteins (by electrophoresis); plasma refractive index; erythrocyte sedimentation rate; erythrocyte osmotic fragility; blood surface tension and density; haemoglobin; and packed cell volume. These blood factors are discussed with reference to fish health and disease and to changes caused by deleterious quantities of water pollutants.
Scale‐eating habits of the marine teleost Terapon jarbua (Forskål)
Authors: Whitfield A. K. , Blaber S. J. M.
Published: January 2006

Terapon jarbua, a marine teleost attaining a length of 25 cm, is abundant in the estuaries of the tropical and subtropical Indian Ocean. Fish scales removed from living fish are the most important food and represent the utilization of a niche previously unrecorded in the marine environment. Laboratory experiments show that T. jarbua can digest fish scales which have a relatively high energy content of 2cal mg−1 and further that the scales are removed only from living fish and not collected off the bottom or from dead fish. The scales are taken under natural conditions from fish larger than T. jarbua and slow swimming species are favoured. T. jarbua always attacks the lateral surface of the prey species and scales are removed mainly from the posterior region of the body, particularly around the caudal peduncle. A variety of species are attacked. The black longitudinal stripes of T. jarbua fade during feeding but in the presence of conspecifics darken. This colour pattern, which is unique among south east African estuarine fish, together with the small size of T. jarbua scales, may prevent autopredation. It is suggested that the scale‐eating habit of T. jarbua arose as a modified form of predation or as an extension of ‘cleaning’ ectoparasites from the scales of larger fish. Ectoparasites are relatively common in the diet of T. jarbua.
Studies on the biology of Eubothrium salvelini and E. crassum in resident and migratory Salvelinus alpinus and Salmo trutta and in S. salar in North Norway and the islands of Spitsbergen and Jan Mayen
Authors: Kennedy C. R.
Published: January 2006

Samples of Eubothrium salvelini and E. crassum were obtained from resident and migratory Salvelinus alpinus and Salmo trutta and from S. salar at sea from North Norway and the islands of Spitsbergen and Jan Mayen. Scolex dimensions proved an unsuitable character for identifying these two parasite species, and use of alternative characters confirmed that E. salvelini is specific to Salvelinus and E. crassum to Salmo. Distributions of both species are co‐extensive with their hosts, but levels of infection in any locality relate to the abundance of zooplankton. E. salvelini exhibits seasonal maturation and incidence cycles in char. It is recognised as being a freshwater parasite, although some individuals can survive the period of marine migration of sea char. Returning migrant char may contain such individuals together with small plerocerciform parasites acquired almost immediately upon their re‐entry to freshwater. No evidence for marine infections with E. salvelini was found. The presence of plerocerciform and gravid adult E. crassum in salmon caught at sea confirms the existence of a marine life cycle and a marine race in this species. In salmon moving from one medium to the other the marine and freshwater races replace each other, but in sea trout, which spend shorter periods at sea, complete replacement may not occur and at any one time fish may harbour individuals of both races. Recognition of the existence of two races clarifies much of the confusion surrounding the biology of this species.
Karyotypic analysis of the gobiid fish genus Quietula Jordan and Evermann
Authors: Cook Peter C.
Published: January 2006

The karyotypes of the two species of the gobiid fish genus Quietula, Q. y‐cauda (Jenkins & Evermann) and Q. guaymasiae (Jenkins & Evermann), are reported for the first time. The karyotypes contained equal numbers of chromosomes (2n=42) but differed in chromosome morphology. Quietula y‐cauda has 42 acrocentric chromosomes. Quietula guaymasiae has six metacentric, four submetacentric, and 32 acrocentric chromosomes. It is suggested the karyotype of Q. guaymasiae might have been derived from that of Q. y‐cauda. In addition, from comparison of the species' karyotypes of the genera Quietula and Gillichthys, it is possible the karyotype of Q. y‐cauda might have been derived from that of Gillichthys mirabilis.
Effect of methallibure on gonad development and carotenoid content of the fins of Sarotherodon mossambicus (Tilapia mossambica)
Authors: Lanzing W. J. R.
Published: January 2006

Juvenile Sarotherodon mossambicus were exposed to a daily dose of 1 or 2 p.p.m. of the antigonadotropic drug methallibure for a period of seven weeks. The control fish all showed well‐developed gonads and a considerable concentration of astaxanthin in the dorsal fins. The dominant male showed a much higher astaxanthin value than the other fishes. Methallibure completely prevented gonad development. Nevertheless, some astaxanthin deposition did occur in the drug‐treated fish.
A sterile sea water circulating system for the jar culture of developing fish eggs
Authors: Shackley Susan E. , King P. E.
Published: January 2006

A sterile sea water circulating system for the jar culture of developing fish eggs is described. An ultra–violet filter unit is used to sterilise the water and the system is one of a double‐circulation the advantages of which are discussed. This is an effective method for maintaining the developing embryos of Blennius pholis L. under controlled conditions, and would be applicable to studies on other demersal fish species or marine organisms.
The comparative feeding behaviour of brown trout, Salmo trutta L. and Atlantic salmon, Salmo salar L. in Llyn Dwythwch, Wales.
Authors: Pedley R. B. , Jones J. W.
Published: January 2006

A detailed comparative study of the diets of natural brown trout and stocked Atlantic salmon in Llyn Dwythwch, North Wales, was carried out over a period of 13 months. The annual and seasonal composition of both diets was calculated by number, volume and occurrence methods. Food in relation to fish size was compared by Spearman rank correlation. Interspecific competition was only significant during the summer months when food was abundant. The bottom fauna was classified according to accessibility, and utilization of the fauna and electivity is discussed for each species. The similarity of diet between the salmon stocked into Llyn Dwythwch and those in Welsh rivers implies that the former is the result of inheritance rather than from interactive segregation with the lake trout.
The frequency, distribution, and pathology of three diseases of demersal fishes in the Bering Sea
Authors: McCain Bruce B. , Myers Mark S. , Gronlund William D. , Wellings S. R. , Alpers Charles E.
Published: January 2006

During September and October, 1975, bottom‐dwelling fish from the Bering Sea were examined for diseases. The three most commonly observed diseases and their frequency of occurrence were epidermal papillomas of rock sole (Lepidopsetta bilineata Ayres), 1‐0%; lymphocystis of yellowfln sole (Limanda aspera Pallas), 2‐1 %; and epidermal tumours of the pseudobranch of adult Pacific cod (Gadus macrocephalus Tilesius), 7‐4%. Both the appearance and the histological characteristics of epidermal papillomas on rock sole resembled those found on several species of flatfish in Puget Sound. The frequency of tumour‐bearing rock sole ranged from 0‐23%, with the highest occurrence at sampling stations around the periphery of the Bering Sea in water depths of 20‐30 fathoms (36‐54 m). The virus‐caused lymphocystis lesions were usually on the ‘blind’ side fins and skin surfaces of yellowfin sole, the largest lesions being found on the operculum, and the most common site of infection was the pectoral fin. The frequency of lymphocystis was 0‐15 %, with a gradual increase of prevalence from the northern to southern sampling stations. The Pacific cod tumours were always bilateral, and contained remnants of normal‐appearing pseudobranchial tissue on the surface or deep inside the tumours. Portions of some tumours were necrotic and liquefied. Tumour‐bearing cod were most commonly found in the south and south‐eastern Bering Sea and the frequency of affected cod ranged from 0‐100%.
Efficacy of certain disinfectants against infectious pancreatic necrosis virus
Authors: Elliott Diane G. , Amend Donald F.
Published: January 2006

The virucidal properties of iodophor, chlorine (sodium hypochlorite), formalin, thimerosal (organic mercurial compound), malachite green, and acriflavine were tested on infectious pancreatic necrosis virus (IPNV). Iodine and chlorine showed good activity, but efficacy depended on the concentration of virus, the presence of organic matter (calf serum), and water pH. Water hardness (0‐300 mg 1−1 as CaCO3) did not affect virucidal activity. In a 5 min exposure, 4 mg 1−1 available iodine inactivated 103.9 TCID50 m1−1 IPNV but 16 mg 1−1 iodine were needed for inactivation of 106.3TCID50m1−1. The addition of 0‐5% calf serum significantly reduced the iodine concentration and the virucidal activity. In comparison, 4 mg 1−1 chlorine were needed to inactivate 1046 TCID50 m1−1 IPNV in 5 min. However, the addition of 0‐07 % serum greatly reduced the chlorine concentration and extended the virucidal contact time to 30 min or more. IPNV at 106.3 TCID60 m1−1 was not inactivated by exposures for 60 min to 0‐2% formalin, 10 min to 0‐2% thimerosal, 60 min to 5 mg 1−1 malachite green, or 20 min to 500 mg 1−1 acriflavine. However, acriflavine at 0‐5 mg 1−1 in cell culture media prevented the development of cytopathology caused by IPNV and may be useful in the treatment of the disease.
The effects of salinity and temperature on the development and survival of fish parasites
Authors: Möller H.
Published: January 2006

In brackish water the variety of marine and freshwater parasite species is considerably reduced. The distribution in brackish water of most marine endoparasites is restricted by the salinity tolerance of their hosts, most of the parasite species are more tolerant than their hosts. The influence of salinity and temperature on nine species has been examined; first stage larvae of Contracaecum aduncum develop in 0‐32‰ salinity; Cryptocotyle lingua proved to be infective at salinities down to 4‰. The greatest resistance was found in Anisakis larvae from herring Clupea harengus, which survived for more than half a year. Parasites in the fish intestines appear to be unaffected by changing water salinities, as the osmolarity in the intestines stays nearly constant. Marine ectoparasites (Acanthochondria depressa, Lepeophtheirus pectoralis) survive about three times longer than freshwater species (Piscicola geometra, Argulus foliaceus) when salinity is 16‰. High temperature increases the effects of adverse salinities on parasites. There is evidence that none of these ecto‐parasitic species can develop within the range of 7‐20‰ salinity.
The effects of the anaesthetic quinaldine on oxygen consumption in an intertidal teleost Blennius pholis (L.)
Authors: Dixon R. N. , Milton P.
Published: January 2006

The effects of the anaesthetic quinaldine on oxygen consumption in an intertidal teleost Blennius pholis (L.) were investigated. Oxygen consumption generally decreases with increasing quinaldine concentration in environmental water. However, at low concentrations, oxygen consumption of smaller specimens is slightly increased. Generally, smaller specimens have their oxygen consumption affected less by a given quinaldine concentration than do larger specimens, as the former appear to be at less depressed stages of anaesthesia. This is thought to be due to smaller B. pholis becoming saturated with quinaldine more rapidly but simultaneously being afforded more rapid removal, because of their greater relative gill area per unit body volume. The reduction of oxygen consumption at high concentrations of quinaldine is great.
Comparative observations on the growth rate and year class strength of roach Rutilus rutilus L. in two Cheshire lakes, England
Authors: Goldspink C. R.
Published: January 2006

In this study some comparative data on the growth rate and year class composition of roach in two Cheshire meres (Rostherne and Tatton) are given. The populations are characterised by year class instability and high growth rates, both of which are most extreme in Tatton Mere. The growth of roach in Tatton Mere is the highest yet recorded from Britain.

The concurrence of two (1969, 1973) strong year classes in both lakes, suggests that climate is an important factor which conditions year class strength. However, although there is some correlation between year class strength and the water temperature index (>14° C) the ultimate cause of year class variability remains obscure. There is no evidence to suggest that year class failure is due to parasitic infestation by Ligula intestinalis or to predation by perch upon roach fry. Year class failure may be due to the mortality of eggs related to the time of spawning. The observed difference in growth rate between the two populations may be attributed to a difference in density caused by the disparity of year class representation in Rostherne Mere and Tatton Mere. However, despite these differences, the net biomass achieved (36–39 kg ha−1) may be similar in both lakes. Superimposed on the effects of density an influence of temperature is noted.
Ictalurus melas (Rafinesque, 1820) and I. nebulosus (Lesueur, 1819): the North American catfishes in Europe
Authors: Wheeler Alwyne
Published: January 2006

The greater part of the literature on European fishes reports the widespread occurrence of an introduced North American catfish and identifies it as Ictalurus nebulosus. Study of the literature reporting critical determinations and of specimens from Europe and Great Britain reveals the presence of two species, I nebulosus and I melas. These fishes are widely used in experimental studies, usually being obtained through aquarium‐fish dealers indirectly from continental Europe. Mostly they are incorrectly identified as I nebulosus. There is reason to believe that I melas is the more commonly imported catfish in Britain; both species occur feral in mainland Europe.
A note on the failure of vitamin A to influence the epidermis of the brown trout, Salmo trutta L.
Authors: Pickering Alan D.
Published: January 2006

Three groups of hatchery–reared brown trout were fed for 32 weeks with synthetic diets containing 0, 18 and 100 i.u. vitamin A palmitate g−1. Vitamin A levels in the liver of the fish at the end of the experiment were 3,50 and 300 i.u. g−1 respectively. The growth rate was not significantly different between any of the three groups of fish. At all times during the investigation epidermal thickness andgoblet cell concentration were similar in the three groups but there were significant changes in goblet cell concentration within each group during the experimental period. Sexually mature males in all three groups offish contained significantly fewer epidermal goblet cells than immature fish of either sex.
Seasonal changes in thyroidal status in the plaice, Pleuronectes platessa L.
Authors: Osborn R. H. , Simpson T. H.
Published: January 2006

A chemically specific analysis for plasma thyroid hormones has been used to disclose a seasonal bimodality in the concentrations of thyroxine (T4) and triiodothyronine (T3) in the plaice; maxima in both hormone levels occur in winter and in summer. The ratio of T4 concentrations to T3 varies seasonally being at a minimum in summer. A highly significant correlation of T4 plasma levels with the landings per unit fishing effort for the same area has been observed.
Use of radio telemetry for studying upriver migration of adult Atlantic salmon (Salmo salar)
Authors: McCleave J. D. , Power J. H. , Rommel S. A.
Published: January 2006

This paper describes and evaluates a 50 mHz radio telemetry system for studying river movements of adult Atlantic salmon (Salmo salar). In fresh water for most applications radio telemetry is preferable to ultrasonic telemetry, because the receiving element (antenna) can be above water, and radio signals are scarcely affected by turbulent, weedy or ice‐covered water. Within the range of 10–200 mHz higher frequencies are preferred, since the efficient antenna size is inversely proportional to frequency, and attenuation of signals is independent of frequency. Transmitters were cylindrical (6.5–9.6 cm long * 1.9 cm diam) with a 0.5 wavelength antenna trailing from one end. Each emitted pulsed signals on one of 20 crystal‐controlled channels between 49.100 and 49.385 mHz. Transmitters were placed in the stomachs of salmon and the antenna trailed out the last gill slit. Receivers were portable 20‐channel manual or automatic scan models, and antennas were 48 cm diam capacitor tuned loops. Some salmon regurgitated transmitters. Two salmon were recaptured and showed no ill effects from carrying transmitters for 32 and 42 days. Pulse rate had little effect on known transmitter life under natural conditions. Known tag life was variable, but averaged 70 days for transmitters with 1000 mah batteries. The range of transmission of transmitters to a receiving system in an airplane at 410 m altitude was about 10 km, and to a boat about 1 km. Range to a land vehicle was variable depending on obstructions. From the airplane transmitters can be located within a radius of about 50 m.
Ultrasonic tracking of the movements of atlantic salmon smolts (Salmo salar L) in the estuaries of two Scottish rivers
Authors: Tytler P. , Thorpe J. E. , Shearer W. M.
Published: January 2006

Ultrasonic telemetry was used to follow the movements of two groups of smolts in the estuaries of two small Scottish rivers. Hatchery reared smolts released into a typical wedge flow, partially mixed estuary had movements which were dominated by the influence of tide on the direction of water flow. The net movements of wild native smolts in a two layer flow estuary, in which freshwater flow dominated, was downstream but were intermittent consisting of short steps and numerous long pauses. The hatchery reared smolts escaped from the estuary within a tidal cycle, moving out on an ebb tide. The wild smolts remained in the estuary for periods up to 108 h, none escaping within one tidal cycle.
Seasonal changes in reproductive function of the rainbow trout (Salmo gairdneri)
Authors: Whitehead C. , Bromage N. R. , Forster J. R. M.
Published: January 2006

The sequential changes in serum oestradiol 17β (measured by specific radioimmunoassay), vitellogenin (measured by phosphoprotein phosphorus content) and total calcium (measured by fluorimetry) in male and female rainbow trout under a simulated natural photoperiod cycle were investigated. Resting levels of 130 pg/ml serum oestradiol in both male and female fish were found in April and May. In the female, levels reached a peak of 4800 pg/ml in October, and almost returned to resting levels just prior to spawning in mid‐January. No significant change from resting levels was seen in the male fish.

In both male and female fish levels of 25 μg/ml serum phosphoprotein phosphorus and 10–14 mg % total serum calcium were found from April to July. Coincident with the rise in oestradiol 17β, in the females serum levels of phospho‐protein phosphorus and total calcium increased to 400 uβg/ml and 58 mg% respectively just prior to spawning. In the males no significant change in either of these values was observed throughout the cycle. These results strongly support the hypothesis that photoperiod is the major factor in the environmental control of reproductive activity in the rainbow trout.