bluuebunny/crossref_metadata_2025 huggingface dataset:
Enzyme activities of plasma and selected tissues in rainbow trout Salmo gairdneri Richardson
Authors: Gaudet M. , Racicot J.‐G. , Leray C.
Published: January 2006

This paper describes the determination in rainbow trout of the normal levels in the plasma of eight enzymes known to be significant in animal pathology. Some relationships between plasma enzyme levels and the enzyme activities in selected tissues are discussed. For LDH which is ubiquitously distributed, we chose, by way of saturation tests, the optimum concentrations of pyruvate and NADH in the assay medium. The LDH ‘isoenzyme ratio’ was determined for heart tissue, liver, and white muscle. When blood was withdrawn from caudal vessels, we observed a net increase of plasma enzyme activities, mainly of CPK and LDH, which was demonstrated to originate from surrounding muscle. Thus cardiac sampling was the only suitable way of obtaining blood for this kind of study. Slightly haemolyzed blood appeared suitable for enzyme determinations except for Alk Pase which is about 50 times more concentrated in erythrocytes than in plasma. CPK was highly concentrated in the heart and the muscle, GOT was concentrated in the heart while the liver appeared to be a valuable source of GDH (as well as the kidney) and GPT.
The surface area of mudfish
Authors: Hattingh J.
Published: January 2006

The surface area of two closely related mudfish species have been determined by coating the animals with masking tape. The results indicate that Labeo capensis specimens above 95 g body weight have a larger surface area than corresponding L. umbratus animals. The same is true for the fin surface area above 50 g body weight. Below these weights L. umbratus specimens have higher surface areas. The body surface area of L. capensis is always lower than that of L. umbratus in the range studied.
A study of the karyotype of a population of banded killifish (Fundulus diaphanus) from the Hudson Rive
Authors: Arcement Reese J. , Rachlin Joseph W.
Published: January 2006

Studies were carried out to find appropriate techniques for securing a suitable karyotype from a population of Fundulus diaphanus in the Hudson River and to compare it with a published karyotype of a population of the same species from the New Haven, Connecticut area. A modification of the basic method of Denton & Howell proved to be a simple, effective and inexpensive approach for acquiring numerous and distinct chromosomal spreads for detailed karyotype analyses. The two karyotypes were identical in modal number, arm number and number of submetacentrics; however, they differed in numbers of acrocentrics and secondary constrictions. These differences may indicate incipient chromosomal evolution with the two distinct environments acting as selective agents. Preliminary work was carried out with banding techniques; the modified Denton & Howell method with banding appears to be an effective and promising direction for fish cytogenetics.
Ultrastructure of the liver in channel catfish Ictalurus punctatus (Rafinesque)
Authors: Hinton David E. , Pool Charlotte R.
Published: January 2006

Livers of 38 channel catfish were studied by light and electron microscopy and the morphology of hepatocytes, endothelial cells, Kupffer cells, fat‐storing cells, macrophages, exocrine pancreatic cells, and epithelium of bile pre‐ductules and ducts was described, Hepatocytes contained large peri‐canalicular bodies which showed acid hydrolase activity. A comparison between catfish liver and that of other teleosts was made. The applicability of the findings to pathobiological studies of teleost liver is described.
Food and feeding of three Citharinus species in Lake Kainji, Nigeria
Authors: Arawomo G. A. O.
Published: January 2006

This paper provides information on the food and feeding habits of three Citharinus species in Lake Kainji. A total number of 2357 specimens made up of 1628 Citharinus citharus, 705 C. distichodoides and 24 C, latus were examined. The majority of the fish caught by gill‐netting had empty stomachs unlike those caught by cast‐netting and electrofishing. The main food items were planktonic and epipelic blue‐green and green algae. All the three species had similar feeding habits and also fed on the same items; their food varied with the seasons. Citharinus spp. have high gut length/standard length ratios which are adaptations to the microphagous and planktivorous feeding habits.
Experimental study on population dynamics in the guppy, Poeclia reticulata (Peters). Effect of shelters on the increase of population density
Authors: Yamagishi Hiroshi
Published: January 2006

To study mass culture of the guppy, Poecilia reticulata (Peters) for use in mosquito control, the population dynamics of the fish were studied in 10001 polycarbonate tanks with and without shelters for fry, under conditions of constant temperature and filtration of water, and sufficient food supply. In the tank with shelters, the maximum density attained was 5.84 fish per 1 at the 77th week, when the initial population had been 25 males and 25 females. After this period the density began to decrease and dropped to 1.04 fish per 1 at the 105th week. Conversely, in the tank without shelters, almost no increase in number took place when the population started with either 50 adult fish or 25 fry. The sex ratio of the guppies in the 10001 tank with shelters varied. In particular, females increased in. relation to male when the fry which had been produced in large quantities became sexually mature. The intervals between spawning averaged 38 days with a range of 26 to 90 days. An equation, log Y=0.0443X‐0.2968 expresses the relationship between the number of young in the brood and the body length of the females.
The fish populations in inshore waters of the west of Scotland. The Biology of the Norway Pout (Trisopterus esmarkii)
Authors: Gordon J. D. M.
Published: January 2006

Norway pout (Trisopterus esmarkii) were collected during a trawling survey of inshore waters of the west coast of Scotland. 0–group fish were first taken by the bottom trawl in late summer and since there was no evidence of local spawning it was inferred that a migration from the open sea had occurred. The distribution and age composition of the stock was related to depth. The young fish migrated from the shallower stations during their first winter but persisted for a second winter at some of the deeper stations.

There was a marked seasonal variation in the quality of the diet and in the intensity of feeding. The most important food organisms were copepods, decapod larvae, mysids and euphausiids. Diurnal variations in the intensity of feeding were minimal in August but the quality of the food in the stomachs was dependent on the time of sampling. The converse was observed in January when feeding was at a maximum between dusk and dawn but the quality of the food remained fairly constant.
Observations on saprolegniasis of adult sockeye salmon, Oncorhynchus nerka (Walbaum)
Authors: Neish Gordon A.
Published: January 2006

Some observations on the mycology and pathology of saprolegniasis of maturing sockeye salmon are reported. Saprolegnia spp. were isolated from all lesions examined. Some isolates did not produce oogonia and could not be identified further. The other isolates have affinities to the S. diclina‐S. parasitica complex. Observations on the gross and histo‐pathology of the lesions show the fungi can be active pathogens. It is hypothesized that increased levels of plasma corticosteroids and depletion of ascorbic acid reserves in the fish increase the probability that Saprolegnia spp. will initiate infections, either alone or concurrently with other opportunistic parasites.
Effects of temperature and ration level on the growth and food conversion efficiency of Salmo gairdneri, Richardson
Authors: Wurtsbaugh Wayne A. , Davis Gerald E.
Published: January 2006

The effects of temperature and ration size on the growth rate and gross efficiency of food conversion of juvenile rainbow trout Salmo gairdneri were evaluated during 25‐day seasonal experiments. Rations ranged from near‐starvation to repletion levels. Test temperatures were 3 and 6°C higher than the controls which fluctuated dielly and seasonally. At rations near maintenance, elevated temperatures decreased trout growth. As the feeding rate increased the detrimental effect of temperature on growth was ameliorated. At repletion feeding levels, elevated temperature up to 17°C improved trout growth by increasing the maximum food consumption rate. With a temperature increase from 6.9 to 22.5°C maintenance rations increased from 2.2 to 7.5 % body weight per day. Gross efficiency was dependent upon ration level and temperature. As the food consumption rate increased, efficiency increased to a maximum, then generally declined at repletion levels. Elevated temperatures resulted in reduced efficiencies at low consumption rates but temperatures had little effect at high ration levels. A field study provided estimates of the food consumption relationships established in the laboratory, suggested any substantial increase of stream temperature without a concomitant increase of food abundance would result in decreased trout production.
Peracute vibriosis in juvenile turbot Scophthalmus maximus
Authors: Horne M. T. , Richards R. H. , Roberts R. J. , Smith P. C.
Published: January 2006

An outbreak of an acute oedematous disease characterised by orbital and abdominal swelling, and high mortality, in young turbot, was studied. The clinical and pathological picture was consistent with a circulating toxaemia principally affecting the heart, orbit and kidney. Vibrio anguillarum, virtually identical with type strain NCMB6, was isolated in pure culture from all organs of all fish. Therapy was only marginally successful using antibiotics but in a small group subjected to temperature reduction below 10°C, losses were reduced from 20 % to 5 % compared with the controls.
The functional roles of different muscle fibre types identified in the myotomes of marine teleosts: a behavioural, anatomical and histochemical study
Authors: Mosse Peter R. L. , Hudson Richard C. L.
Published: January 2006

The histochemical profiles of the major myotomal muscle fibre types and the proportion of red muscle in the myotome of a number of teleost types has been investigated in relation to their observed swimming behaviour. A direct relationship exists between the proportion of red muscle present and the ability to sustain swimming. The red muscle fibres were found to be metabolically adapted for this role, whilst the white muscle fibres were better adapted for more vigorous activity. The possible roles of the pink and other fibre types are discussed. The histochemical investigation revealed no differences between the teleost types except that the deep white muscle of a pelagic species may have a higher aerobic capacity than that of other species.
Some effects of temperature, meal size and body weight on gastric evacuation time in the dab Limanda limanda (L)
Authors: Jobling M. , Gwyther D. , Grove D. J.
Published: January 2006

Gastric emptying time in the dab, Limanda limanda, has been studied using an X‐ray technique. The addition of 25 % barium sulphate to a test meal did not significantly affect the transit time. Lowering the experimental temperature from 16.4 to 8.5°C markedly decreased gastric evacuation time. An increase in ration size led to an increase in the time required to empty the stomach and also to increase the amount of food digested per unit of time. For any given ration size, expressed as per cent body weight, the larger the animal the longer is the time required for evacuation of that meal. We suggest that the food intake per day, as a percentage of live body weight, will be smaller for larger L. limanda in the wild.
Density‐dependent mortality of trout fry (Salmo trutta L.) and its relationship to the management of small streams
Authors: Mortensen Erik
Published: January 2006

The natural mortality rate of trout fry and the impact of weed cutting and cleaning out of weeds, branches and twigs from the stream‐bed upon the mortality rate of trout fry was studied on several reaches in small streams. Above an initial density of 3.1 fry m–2 natural mortality rate was found to be density‐dependent in the first few months of life. In reaches where weed cutting and cleaning out of the stream‐bed had taken place the mortality rate was higher than that found under natural conditions in undisturbed reaches. The results support the suggestion that stream management works which make the stream more uniform will be in conflict with sound fishery management.
An analysis of the metazoan parasitocoenoses of brown trout Salmo trutta from British Lakes
Authors: Kennedy C. R.
Published: January 2006

The composition of the parasite fauna of brown trout Salmo trutta in nine British lakes from varying geographical locations has been analysed with regard to several selected physico‐chemical parameters of the lakes. Significant correlations existed between the size of the lake and the number of parasite species harboured by trout and between the altitude of the lake and the number of parasite species present. No significant relationships were found between the number of parasite species and the geographical position, age, degree of isolation or CaCO, levels of the lakes. Similarly no relationships existed between the proportions of the parasites with different life cycles and the parameters examined, or between the presence or absence of a particular species of parasite and the lake's limno‐logical features. It is concluded that the parasites of brown trout have been, and still are, capable of rapid and widespread dissemination throughout mainland Britain, and their occurrence in any lake is a result of the combination of a number of local factors. The predictive value of the conclusions is tested and discussed with special reference to the parasite fauna of trout in reservoirs.
The production of juvenile Atlantic salmon, Salmo salar in the upper Wye, Wales
Authors: Gee A. S. , Milner N. J. , Hemsworth R. J.
Published: January 2006

The production of juvenile Atlantic salmon (Sulmo salur L.) was investigated in 16 study sites in the upper Wye catchment during the period February 1975 to November 1976. The population structure was characterised by large numbers of 0+ fish whose abundance decreased with respect to time so that the numbers of each of the older year‐classes was a function of the year‐class strength of the original fry. The range of parr densities was similar to that recorded for other rivers: the estimates of 2+ smolts did not exceed about 0.04 m−2. Production ranged from 0.3 to 11.0 gm−2 a−l; Of and 1+ fish contributed over 72% and 3+ fish less than 1 % of the total annug production. The relationship between production P (gm−2 a−1) and mean biomass B (gm−2) for all yeatclasses considered separately and in combination can be expressed by the relationship P=aB̄b. The values for a vary with age‐composition and season but the values for b are not significantly different. Differences in growth rate of salmon between sites are small and differences in production result principally from differences in standing crop (biomass density). In most cases low values for salmon production can be attributed to poor spawning.
Fishes taken by the beach seines fishing at Lumley, Freetown (Sierra Leone)
Authors: Okera W.
Published: January 2006

From July 1974–May 1976, observations were made on the catches of beach seines fishing at Lumley, Freetown. The larger species caught were counted and the abundance of the smaller species was qualitatively assessed. Sixty‐four species were recorded. The pelagic species Sardinella eba (juvenile and young stages), Cybium tritor, Caranx carangus, Caranx senegalus and Caranx crysos dominated the catches. Chloroscombrus chrysurus, V. setapinnis and B. auritus were caught in large quantities during the rainy season (May‐October) and they were also present during February. Young Sphyraena piscatorum and Caranx senegalus also appeared during the rainy season and they probably represented broods spawned during the preceding months of September to February.
Effect of population density and feeding rate on the fathead minnow (Pimephales promelas)
Authors: Smith Helen T. , Schreck Carl B. , Maughan O. Eugene
Published: January 2006

Juvenile fathead minnows (Pimephales promelas) were stocked in tanks at different densities and different ration levels, in two experiments, to determine effects on final population density, growth and fecundity. Length and weight of fish increased with increased food availability. Egg size was exponentially related to growth and perhaps directly to ration level. High population density appeared to limit growth and gamete development regardless of food abundance. Additionally, water volume appeared to limit numbers (tolerance density) of fish which can be supported in a specific volume of water.
Aspects of the biology of the spotted dragonet Callionymus maculatus Rafmesque‐Schmaltz from the west coast of Scotland
Authors: Gibson R. N. , Ezzi I. A.
Published: January 2006

The biology of a Scottish population of the spotted dragonet Callionymus maculatus was studied from February 1975 to September 1976. The data were taken from monthly samples totalling over 700 fish trawled in 18–36 m on a soft mud bottom. Neither otoliths nor radial bones were found to be suitable for age determination, but evidence from other sources suggested that most growth takes place in the first two years of life and that males grow faster, but do not live as long (at least 3 years) as females (at least 5 years). Examination of the gonads showed that the spawning season probably lasts from April to September, that females mature earlier in life than males and are serial spawners. The males may reach first maturity at different ages. The sexes are markedly dimorphic. The rays of the dorsal, anal and caudal fins grow isometrically in females but growth of these organs in males is allo‐metric after maturity has been achieved. The fish feeds predominantly on polychaetes and amphipods, although bivalve molluscs, macruran decapods and ophiuroids also occur frequently in its diet. There is some difference in the diet between length classes, smaller fish taking fewer polychaetes and more amphipods than the larger individuals. The species is finally compared with other dragonets whose biology is known.
Gastric evacuation in plaice, Pleuronectes platessa L.: effects of temperature and fish size
Authors: Jobling M.
Published: January 2006

Using a volume dependent model of gastric evacuation, the effects of temperature and fish size were examined. Rates of gastric evacuation were unaffected by fish size but increased with increasing temperature. The relationship between maximum stomach volume and fish weight was found to be a linear one. From information of gastric evacuation rates and stomach volume, the amount of food evacuated from the stomach per day was calculated for different size classes of fish. Daily food evacuation increased in proportion to body weight to the power 0·68. Assuming these methods give a crude estimate of daily food intake, the results are discussed in relation to published work on food intake in fishes.
A histochemical and ultrastructural study of the development of the propulsive musculature of the brown trout, Salmo trutta L., in relation to its swimming behaviour
Authors: Proctor C. , Mosse P. R. L. , Hudson R. C. L.
Published: January 2006

The differentiation of the myotomal muscle types in the propulsive musculature of Salmo trutta has been investigated histochemically and ultrastructurally from late embryonic to free‐swimming fish at 5° months post fertilisation and related to observed changes in swimming behaviour. A histochemical and ultrastructural characterisation was also made of the major myotomal muscle fibre types in fingerling and yearling S. trutta. Two distinct populations of muscle cell types can be recognised prior to hatching. The early development of the white fibre population is related to the short, burst‐type swimming activity at early stages. The later increase in the development of the red fibre population is directly related to the appearance of sustained swimming activity. The swimming performance of freeswimming alevins has been investigated and the results are discussed in comparison to adult fish.
Ultrastructure of the liver of the fingerling rainbow trout Salmo gairdneri Richardson
Authors: Chapman G. B.
Published: January 2006

Portions of the livers of fingerling rainbow trout were studied by light and electron microscopy. The histology, cytology and ultrastructure of mesothelial cells, serosal fibroblasts, hepatocytes, sinusoidal endothelial cells, endothelial cells of central veins and blood cells were described. Mesothelial cells and fibroblasts constituted a very thin capsule. Hepatocytes contained extensive areas of rough surfaced endoplasmic reticulum, consisting mainly of parallel cisternae and pools of glycogen. One or two nuclei and numerous mitochondria occurred in the areas of endoplasmic reticulum, but never in the pools of glycogen. Hepatocyte surface possibilities included hepatocyte to hepatocyte, hepatocyte to bile canaliculus, hepatocyte to space of Disse and hepatocyte to serosa. The trout liver was compared compared to channel catfish liver and to rat liver. Functional implications of the structural features were discussed.
Communities of metazoan parasites in open water fishes of Cold Lake, Alberta
Authors: Leong T. S. , Holmest J. C.
Published: January 2006

Communities of metazoan parasites in ten species of fishes from Cold Lake, Alberta are described and compared. Relative abundances in the overall community of parasites in the lake were estimated using data on abundance in each host species, plus estimates of the relative abundances of the species of hosts. Parasites of the numerically dominant salmonid fishes dominated the overall community, with over half of the individual parasites being Metechinorhynchus salmonis. Exchange of parasites between host species was greatest between related and/or abundant host species. Parasite communities in cisco and whitefish, Coregonus spp., were relatively rich in species and diverse (Simpson's index) compared with communities in those species in other lakes in North America; communities in lake trout, Salvelinus spp., and the non‐salmonid fishes were poor in species and low in diversity compared with communities in other lakes. Parasite species overlaps (Jaccard index) between related host species in Cold Lake were greater than overlaps within host species between lakes. The same pattern is seen in data from some other lakes. These features support the hypothesis of Wisiewski (1958); that the parasite community within an ecosystem is characterized by parasites of the numerically dominant hosts.
A new species of hagfish of the genus Myxine, with notes on other eastern Atlantic myxinids
Authors: Fernholm B.
Published: January 2006

Myxine ios sp. nov. is a seven‐gilled hagfish occurring on the continental slope in the eastern North Atlantic, off West Africa and southwest Ireland. The two populations overlap in morphometric and meristic character, but the Irish population is distinguished by having a white head and a whitish middorsal or midventral line. More material and collections from intermediate localities are needed before it can be determined if the two populations are distinct at the specific or subspecific level. The northern (Irish) population of M. ios is believed to occur in the same geographical range as M. glutinosa but to live at greater depths. Myxine ios is compared with M. glulinosa L. and M. capensis Regan, the other two eastern Atlantic Myxine species; new data are given for these species, both of which are regarded as valid.
Infestations by Gyrodactylus sp. of Atlantic salmon, Salmo salar L., in Norwegian rivers
Authors: Heggberget T. G. , Johnsen B. O.
Published: January 2006

Young Atlantic salmon, Salmo salar, brown trout, Salmo trutta, and Arctic char, Salvelinus alpinus, from eight rivers in North and Mid Norway were examined for Gyrodactylus. The fish were collected from 1975 to 1980. A Gyrodactylus salaris type was observed infecting salmon from six of these rivers. No trout or char were infected. A high frequency and intensity of infection of salmon were observed in all but one of the rivers surveyed. In the Saltdalselva, only one specimen of Gyrodactylus infecting one fish was observed. No subsequent mortality of salmon was observed in this river while there were signs of a high mortality of salmon in the other rivers. The salmon parr were more frequently attacked than the fry, the mortality of salmon seemed to have happened in most of the rivers one year after the first observations of Gyrodactylus were made. The mortality of salmon and the high infection rate of Gyrodactylus in these rivers appears unique, and as far as known to the authors there are no other described cases of mortality due to Gyodactylus in Atlantic salmon in natural waters. The reasons for the outbreak of Gyrodactylus in these rivers are not known. Two theories are discussed: one that the fish were weakened by environmental factors and the other that Gyrodactylus was introduced from some of the infected salmon hatcheries in Scandinavia.
The morphology of the trout, Salmo gairdneri Richardson, thymus: some practical and theoretical considerations
Authors: Tatner Mary F. , Manning Margaret J.
Published: January 2006

An electron microscope study of the thymus in trout, Salmo gairdneri, showed that the membrane separating the thymus gland from the extenal water current was not specialized, but merely a continuation of the pharyngeal epithelium. This is discussed in relation to the evolution of the thymus in vertebrates, and to the possible effects on the thymus during hyperosmotic infiltration, a technique used for immunization.
Lipid mobilization during starvation in the rainbow trout, Salmo gairdneri Richardson, with attention to fatty acids
Authors: Jezierska B. , Hazel J. R. , Gerking S. D.
Published: January 2006

Rainbow trout, Salmo gairdneri, were fed pelleted food ad libitum for 35 and 50 days. Lipid deposits were determined in the viscera, liver and muscle (epaxial and hypaxial). Most of the lipid accumulated in the viscera, but the lipid content of liver and epaxial muscle also increased. Hypaxial muscle lipid content remained the same throughout the feeding period. Upon starving the fish for 27 and 48 days following 50 days of feeding, visceral lipid contributed most to energy metabolism among the depots investigated. Muscle also contributed a considerable share while the absolute amount derived from the liver was much smaller.

Patterns of fatty acid mobilization during starvation were also investigated. Saturated acids were preferentially mobilized from the viscera, resulting in a rise in the percentage of monoenes and polyunsaturates. In liver, the percentage of saturates remained relatively constant whereas the percentage of monoenes declined and polyunsaturates increased. In muscle, a substantial increase in saturates was caused by a decline in monoenes; polyunsaturate content remained constant. As a result of these shifts in relative fatty acid composition the U/S (unsaturates to saturates) ratio rose in viscera and liver and decreased in muscle. The UI (unsaturation index) responded in essentially the same way. Possible explanations for preferential fatty acid utilization are discussed in terms of energetics and structural relationships.
The influence of river flow on pelagic sardine catches in Lake Kariba
Authors: Marshall B. E.
Published: January 2006

The nutrient level of Lake Kariba is governed by the Zambezi river which provides about 70% of its water supply. Other tributaries are richer in nutrients and have an appreciable local effect. This is shown by the catches of Limnothrissa miodon which increase after strong flows in the Sanyati river. This is in contrast to natural lakes such as Lake Tanganyika and may be an important management factor in Lake Kariba and other man‐made lakes. Possible periods of poor rainfall could thus reduce the Limnothrissa yield in Lake Kariba.
Growth and food habits of hybrid carp, Ctenopharyngodon idella×Aristichthys nobilis, from aerated and non‐ aerated ponds
Authors: Shireman J. V. , Aldridge F. J. , Rottmann R. W.
Published: January 2006

Hybrid grass carp fry (Ctenopharyngodon idella×Aristichthys nobilis) were stocked into 0·04 ha ponds with and without paddlewheel aeration. Fish in the paddlewheel and non‐paddlewheel pond, preyed upon identical organisms, but in different proportions. Fish in the paddlewheel ponds grew at significantly greater rates.
Maturation and spawning of a gobiid fish, Oligolepis acutipennis (Cuv. & Val.), from the south‐west coast of India
Authors: Geevarghese C. , John P. A.
Published: January 2006

The breeding biology of Oligolepis acutipennis (C. & V.), a gobiid fish abundant in the estuaries and brackish water tracts of the south‐west coast of India was studied. Data on the intra‐ovarian development of ova, the breeding season, spawning frequency, size at first maturity and sex‐ratio were based on observations for 1 year. The size distribution of ova showed no significant variation between different regions of the ovary. The gonads were classified into five maturity stages. The sequence of development of ova to maturity indicated two batches of ova developed in a single ovary in a year. The minimum size at first maturity of females was less than that of males. Seasonal variation in gonad weight and the percentage occurrence of various maturity stages of gonads showed that the fish has a protracted breeding period in which two seasons can be recognized. The females dominate over males in numbers except in the non‐breeding months.
Reproduction effort versus the environment; case histories of Windermere perch, Perca fluviatilis L., and pike, Esox lucius L.
Authors: Craig J. F. , Kipling C.
Published: January 2006

The theoretical limits of net reproduction rates for perch, Perca fluviatilis L. and pike, Esox lucius L, have been estimated from the upper and lower limits of fecundity, growth, mortality, age of maturity and biomass of parental stock, observed in Windermere over 40 years. Differences in egg numbers due to changes in fecundity were for perch × 1.5, for pike × 2. Assuming the same mortality, a fast growing cohort would produce more eggs during its lifespan than a slow growing, for perch × 2, for pike × 9. Changes in mortality from high to low resulted in more eggs, for perch × 7, and for pike (where high mortality includes natural and fishing mortality) × 10. Change in age at first maturity from 3 to 2 years was unimportant. Biomass of parental stock varied by × 6 for perch and × 3 for pike, and number of eggs laid varied by x2 for perch and × 5 for pike. The number of recruits at age 2 years varied by × 300 for perch and × 7 for pike. It was concluded that temperature in the first summer of life and predation were of major importance in regulating the number of recruits. Ricker recruitment curves and a simple model showed that perch, but not pike, could produce maximum recruitment from minimum parental stock. For perch, but not pike, compensatory density dependent mortality increased with increased parental stock. It was concluded that responses by the perch and pike populations to a changing environment can not be of sufficient magnitude to prevent wide fluctuations in recruitment.
Smoltification in the net‐pen culture of accelerated coho salmon, Oncorhynchus kisutch Walbaum: prediction of saltwater performance
Authors: Saxton A. M. , Iwamoto R. N. , Hershberger W. K.
Published: January 2006

Prediction of the success of coho salmon, Oncorhynchus kisutch, in making the transition from fresh water to salt water was investigated by the use of statistical comparisons between several freshwater variables and several measures of saltwater performance. Data were collected from two consecutive broodyears of coho salmon that were derived from a nested mating design, grown under enhanced rearing conditions, and raised in marine net‐pens. Equations were developed that could successfully predict percentage smolts and saltwater growth from morphological measurements taken in fresh water. However, saltwater survival was not predictable from these measurements. Criteria for predictive equations and the value of these calculations, as well as directions for future research, are discussed.
Annual variation in lymphocystis infection frequency in flounder, Platichthys flesus (L.)
Authors: Reiersen L.‐O. , Fugelli K.
Published: January 2006

The infection frequency of the virus induced lymphocystis disease has been registered in flounder from the Oslofjord, Norway, during a 4 year period. The disease has a clear regular seasonal variation, and also an annual variation. The percentage infection in the summer was 1–10%, and in the winter up to 57%. The possibility that the high pollution level of the inner Oslofjord could be the reason for the high frequency of lymphocystis disease, is discussed.
Some observations on autumn‐spawning charr, Salvelinus alpinus L., in Windermere, 1939–1982
Authors: Kipling C.
Published: January 2006

Every year from 1939 to 1982 autumn‐spawning charr, Salvelinus alpinus L., have been monitored in the north basin of Lake Windermere. Gillnets of mesh 32 mm bar were used. Up to 1974 the nets were set in Low Wray Bay, but, because of interference by the public, from 1975 they have been set at Thompson Holme, a less accessible site. The results from the two sites are not directly comparable. The main spawning time is November, and catch per unit effort (net day) in November has been calculated. From 1944 to 1974 the catch per unit effort showed an increasing trend, and from 1975 to 1982 it has been relatively stable. Growth was similar in the 1940s and 1970s. It is suggested that the increase in numbers of charr could be due to reduced predation by pike.
Effects of sublethal concentrations of zinc and benzene on striped bass, Morone saxatilis (Walbaum), infected with larval Anisakis nematodes
Authors: Sakanari J. A. , Moser M. , Reilly C. A. , Yoshino T. P.
Published: January 2006

Young of the year striped bass, Morone saxatilis, were exposed to sublethal concentrations of zinc and benzene and infected with larval Anisakis nematodes to determine the effects of these stressors on various physiological parameters. Results indicated that both pollutants and parasites significantly decreased haematocrit values. Parasites alone increased the liver somatic index, decreased haematocrits and, in the initial phase of the experiment, lowered antibody titres. Pollutants alone did not appear to significantly affect antibody titres, nor was there any difference in zinc and benzene uptake in the livers of infected and non‐infected fish.
The influence of food availability, breeding seasons and growth rate on commercial catches of Limnothrissa miodon (Boulenger) in Lake Kariba
Authors: Cochrane K. L.
Published: January 2006

Commercial catches of Limnothrissa miodon in Lake Kariba show clear seasonal fluctuations. Recruitment to the pelagic fishing areas was investigated. A von Bertalanffy growth curve for the species was calculated and the breeding season determined from the calculated hatching dates of observed alevins and juveniles. Distribution of the different size classes was determined by a horizontal transect. Analysis of body composition showed a decrease in total lipids at the time when catches were dropping. This was shown to be due to a decline in triglyceride fat reserves apparently resulting from food stress and possibly resulting in increased natural mortality. Recruitment to the fishing areas and the total mortality rate are believed to cause the seasonal fluctuations in catch. The annual cycle of production may be caused by the summer inflow of nutrients from the rivers. Growth is apparently stunted in comparison to the species’ growth rate in Lake Tanganyika, probably due to the lower nutrient status of Lake Kariba.
Diploid gynogenesis induced by hydrostatic pressure in rainbow trout, Salmo gairdneri Richardson
Authors: Lou Y. D. , Purdom C. E.
Published: January 2006

Diploid gynogenetic fry of rainbow trout, Salmo gairdneri, were produced by treating eggs activated by UV‐irradiated sperm with hydrostatic pressure. Treatments for l0 min at 40 min after activation with 55 000 kPa (8000 psi) pressure resulted in high hatching rates and yields of heterozygous diploid gynogenomes of up to 81%. Attempts to produce homo‐zygous diploid gynogenomes by the suppression of the first mitotic division ofthe eggs failed. Ether treatment alone did not induce diploid gynogenesis.
Development of lamellar epithelial hyperplasia in gills of pantothenic acid‐deficient rainbow trout, Salmo gairdneri Richardson
Authors: Karges R. G. , Woodward B.
Published: January 2006

Two semisynthetic diets differing in the levels of pantothenic acid (PA) supplementation (0 or 40 mg kg−1 diet) were fed to rainbow trout, Salmo gairdneri Richardson, initially weighing 0.7 g fish−1. Each diet was fed to two tanks of fish and, at the start of the feeding trial, each tank contained 200 animals. The experiment was conducted for 28 days during which time, every 2 days, gill tissue was sampled and food consumption was determined. Lamellar hyperplasia was first detected in the gills of deficient fish on the 12th day sample, while reduced feed intake was first manifest at 16 days. Hyperplasia first appeared in the distal regions of the gill filaments, but the lesion rapidly progressed in a proximal direction and 35 of 40 fish examined on days 22–28 exhibited hyperplasia on more than 75% of the filament surface. Gill lamellar hyperplasia is a sensitive indicator of PA deficiency in the rainbow trout. Moreover, the lesion is specific to PA deficiency since its developmental pattern differs histologically from the lamellar hyperplasia of the non‐nutritional gill diseases.
Growth and respiration of two pleuronectiform juveniles from a western Mediterranean bay
Authors: de Morais L. Tito
Published: January 2006

Growth and respiration of juveniles of two pleuronectiforms (Buglossidium luteum and Arnoglossus thori) were studied. The first species has a single period of benthic recruitment (April), a growth pause in winter, and a very low winter metabolism (at 11°C). The second species has two peaks of recruitment (May–June and September–October), an exponential growth with no significant pause in winter, and little reduction of metabolism at 11°C.

Such differences are important factors allowing the sharing of the same biotope by these small benthic predators.
Observations on the food and feeding of the angler‐fish, Lophim piscatorius L., in the northern Irish Sea
Authors: Crozier W. W.
Published: January 2006

Stomach contents of angler‐fish caught monthly throughout the year were examined. Stomach fullness data suggested that maximum feeding activity occurred during the autumn/winter period. Gadoids, in particular whiting and Norway pout, and also Nephrops were the main identifiable prey items. A wide range of other species contributed to the remainder of the diet. Size‐related differences in stomach contents were observed, Nephrops, cod and whiting being favoured by adult angler‐fish. Seasonal variability in the dietary occurrence of herring and Nephrops was noted, apparently related to differences in availability rather than selective feeding by angler‐fish.
A note on the production and use of antisera for the detection of part‐digested sticklebacks in predator stomach‐content samples
Authors: Giles N. , Phillips R. S.
Published: January 2006

Preliminary experiments indicate that serological techniques provide a useful method of identifying specific prey antigens from the stomach contents of fish predators. Problems with cross‐reacting antigens from different prey species can be reduced by absorbing anti‐sera with tissue extracts of the cross‐reacting species. Very small volumes of part‐digested prey tissue are sufficient for identification of the prey species when using agarose diffusion plates (Ouchterlony tests).
Factors governing the production of juvenile Atlantic salmon in Scottish streams
Authors: Egglishaw H. J. , Shackley P. E.
Published: January 2006

Data are presented to show how the number and growth of juvenile salmon in streams in the Scottish Highlands are influenced by various physical (temperature, water chemistry, depth and velocity, type of substratum) and biotic (food resources, competition, recruitment) factors.
A pike management strategy for a trout fishery
Authors: Mann R. H. K.
Published: January 2006

The efficiency of pike removal from a chalkstream trout fishery, by an angling society using electrofishing, was estimated over five successive autumns using mark‐recapture methods. It averaged c. 50% for pike aged 1+ years or more. Numbers of 3+ and older pike decreased from 3.7 ha‐1 (1980) to 1.4 ha‐1 (1984), but there was no corresponding reduction in recruitment success. Both pike immigration and an inverse relationship between natural and fishing mortality could have reduced the effect of the pike culls. The mean weight of 0+ pike increased from 19.4 g to 48.2 g over the 5 years, but there was no change in the growth rates of older pike. Only the larger pike were able to eat the larger trout stocked, and the reduction in numbers of 3 + and older pike appears to have reduced the predation pressure on the trout population. Angling effort increased more than three‐fold over the 5 years studied and rod‐catches more than doubled, but catch‐per‐unit‐effort was extremely variable between years. The increased rod catch occurred despite the decrease in numbers of large (> 33 cm) trout stocked in the spring and early summer. Compared with pre‐cull years, the angling society saved about ş850 (present day prices) by stocking fewer trout.
Cytogenetic studies on the origin and species differentiation of the Philippine medaka, Oryzias luzonensis
Authors: Formacion M. J. , Uwa H.
Published: January 2006

The origin and species differentiation of the Philippine medaka, Oryzias luzonensis, was studied by means of karyotype analyses and interspecific hybridyzations. The karyotype revealed 2n = 48 consisting of 24 pairs of biarmed chromosomes (NF = 96). Characteristic C‐bands were found in three sub‐metacentric pairs. Nucleolar organizer regions (NORs) were detected on the short arms of the satellited sub‐metacentric pair. Estimated DNA‐value was 1.9 pg per nucleus. Interspecific crosses revealed that O. luzonensis was allied most closely to O. latipes (biarmed chromosome type), less closely to O. celebensis (fused chromosome type), and least closely to O. melastigma and O.javanicus (monoarmed chromosome type), which are distributed in east Asia, the Sulawesi, and south‐west Asia and west side of south‐east Asia, respectively. The external appearance of O. luzonensis was also more similar to that of O. latipes. From these results, we concluded that O. luzonensis is a member of the biarmed chromosome group and the nearest relative to O. latipes. Thus, the Philippine medaka seems to be of east Asiatic origin, having migrated to northern Luzon from the China continent via Formosa.
Distribution of N‐methyl‐N‐nitrosourea in the Amazon molly, Poecilla formosa (Girard), after a single intraperitoneal injection*
Authors: Woodhead A. D. , Cao E.‐H. , Melgar T.
Published: January 2006

The distribution and accumulation of labelled N‐methyl‐N nitrosourea (MNU) has been described in the Amazon molly following intraperitoneal injection. Two hours after injection the label was present throughout the body, with enhanced deposition in the macrophages of the atrium of the heart, the kidney and the spleen; about half of the liver cells were labelled. The compound was taken up by the cells of the renal excretory tubules, and certain cells in the optic tectum and corpus cerebelli of the brain. By 6 h, the distribution picture had changed radically. There was little label remaining, except in a few macrophages in the heart and kidneys, and in the nuclei of the renal tubule cells. There was a slight decrease in the numbers of cells in the brain that were labelled, but the amount of material that the individual cells had accumulated had increased. By 48 h there was further loss and only brain cells were labelled. Our findings indicate preferential accumulation of MNU in undifferentiated, pluripotential cells of the optic tectum and corpus cerebelli.
Gastric evacuation in the sandbar shark, Carcharhinus plumbeus
Authors: Medved R. J.
Published: January 2006

Sandbar sharks maintained in an enclosure in the natural environment were fed meals of soft blue crab, Callinectes sapidus, or menhaden, Brevoortia lyrannus, and were sacrificed at intervals after feeding to measure rates of gastric emptying. Regression analysis was used to evaluate the adequacy of various models in describing the decrease in stomach contents with time after feeding. A Gompertz growth curve provided the best fit to the data for both food types. This model suggests that gastric emptying is characterized by an initial lag phase during which evacuation rate increases, a period of maximal evacuation, and a decreasing evacuation rate during the later stages of digestion. Passage of food from the stomach was slow relative to other species of fish studied. The time required to evacuate 98% of a meal was 92–3 and 70–7 h for sharks fed menhaden and blue crab respectively. Evacuation rates did not differ between day and night periods.
A simple method for the preparation of fish chromosomes applicable to field work, teaching and banding
Authors: Rivlin K. , Rachlin J. W. , Dale G.
Published: January 2006

A method is described which has broad application for field acquisition of fish karyotypes for research and teaching. The benefits of the method include: low initial skill level, relatively inexpensive equipment and supplies, simplicity and speed, and the high quality of preparations. The technique was applied to a field study of Apogon maculatus which was shown to contain 34 chromosomes, 2 nucleolar organizing regions (NOR's), and resolvable G‐bands.
Thermal acclimation in selected tissues of the fathead minnow, Pimephales promelas rafinesque
Authors: Tatakis T. A. , Hart R. G.
Published: January 2006

Environmental variables besides temperature such as length, weight, sex, and photoperiod were shown to affect the metabolic rate in gill and white muscle tissue. This required statistical adjustment to account for these factors. Oxygen consumption rates for gill tissue were greater following cold acclimation at all determination temperatures. This suggests thermal compensation had occurred. Metabolic rates for white muscle tissue showed inverse compensation between 7 °C and 15 °C, but little compensation was evident between 15 °C and 23 °C. Both gill and white muscle tissue had Q10 values ranging between 1–00 and 2–00. These are lower than values previously recorded for fathead minnows.