Showing papers in "Journal of Fish Biology in 1976"
TL;DR: The lympho-reticular tissues in the plaice were investigated for their phagocytic properties on colloidal carbon after its intraperitoneal injection and the possible significance of phagocyte aggregations, including melano-macrophages, in association with lymphoid elements in the kidney and spleen is discussed in the context of immune mechanisms.
Abstract: The lympho-reticular tissues in the plaice were investigated for their phagocytic properties on colloidal carbon after its intraperitoneal injection. Fish were killed at intervals ranging from 10 min to 25 days after injection. Although peritoneal macrophages constituted a large population of phagocytic cells, most of the carbon apparently gained access to the circulation as free particles and phagocytosis was performed predominantly by the ellipsoids of the spleen, the network of reticulo-endothelial (RE) cells throughout the haemopoietic tissue of the kidney, and by the RE cells occupying intermuscular spaces in the atrium of the heart. The cardiac macrophages rapidly emigrated from the organ while the carbon containing macrophages in the kidney and spleen formed aggregates in the lymphoid areas, either within or outwith pre-existing aggregates of melano-macrophages.
The possible significance of phagocyte aggregations, including melano-macrophages, in association with lymphoid elements in the kidney and spleen is discussed in the context of immune mechanisms.
249 citations
TL;DR: Following long-term exposure to ammonia there were severe histopathological changes in gill structure and oxygen uptake may have been seriously impaired, and a high incidence of disease was also observed.
Abstract: Gill structure has been studied in fish exposed to various ammonia concentrations. Gill damage resulting from exposure to acutely lethal concentrations was relatively minor and unlikely to have been a primary cause of death. Alternative toxic mechanisms have been discussed. Following long-term exposure to ammonia there were severe histopathological changes in gill structure and oxygen uptake may have been seriously impaired. A high incidence of disease was also observed.
178 citations
TL;DR: Stress produces a haemoconcentration, elevated blood lactate, increased glucose concentrations and alters the plasma electrolyte balance in two groups of the northern pike, Esox leucius L., after one month's starvation.
Abstract: Stress produces a haemoconcentration, elevated blood lactate, increased glucose concentrations and alters the plasma electrolyte balance in two groups (brackish- and freshwater) of the northern pike, Esox leucius L., after one month's starvation. A method for dorsal aorta catheterization and a receptacle for cannulating fish is described.
The blood glucose level of the freshwater pike was twice that of the brackish-water group, and the plasma sodium and magnesium concentrations in the brackish-water pike were significantly higher. The haematocrit, haemoglobin and blood lactic acid concentrations were higher in freshwater pike. The plasma potassium and calcium concentrations in the two groups did not differ.
Haemoconcentration due to stress by handling for 1.5 min was shown by changes in haematocrit and haemoglobin values. The haemoglobin concentration returned to normal in freshwater pike after 4 h but in brackish-water pike after 12 h.
As a result of handling, the blood lactic acid level rose steeply and required 12 h to return to normal.
The blood glucose concentration rose to its maximum value within 1 h of handling and required two days to return to normal.
The plasma sodium level remained stable after handling, but the potassium level was erratic. In brackish-water, the potassium concentration of the pike remained high for 12 h after stress, but in the freshwater group, after a rise, the concentration fell to below the initial level within 4 h. The changes of the potassium concentrations in relation to sampling time are discussed. The changes in the divalent ion concentrations were marked and similar in the two groups; with an increase lasting 1–4 h and then a fall below the initial level, which was regained after two days.
155 citations
TL;DR: The location of lysozyme in fresh plaice tissues was studied using an immunofluorescent technique and the distribution of ly sozyme in the skin and secreted mucus was affected by the method of killing the fish.
Abstract: The location of lysozyme in fresh plaice (Pleuronectes platessa L.) tissues was studied using an immunofluorescent technique. An antiserum to a homogeneous sample of plaice serum lysozyme was prepared in rabbits and was shown to be monospecific by immunodiffusion and inhibition studies. This preparation, used in conjunction with fluorescent labelled sheep anti-rabbit immunoglobulin, demonstrated lysozyme in plaice neutrophils, peritoneal macrophages, gill cartilage and epithelium, spleen, kidney, skin and mucus. The distribution of lysozyme in the skin and secreted mucus was affected by the method of killing the fish.
149 citations
TL;DR: The leucocytes and related cells of the blood of plaice were examined morphologically and their various functions assessed using a number of procedures to identify phagocytosis histochemical reactions and antibody responses.
Abstract: The leucocytes and related cells of the blood of plaice were examined morphologically and their various functions assessed using a number of procedures to identify phagocytosis histochemical reactions and antibody responses. Four morphologically different types of thrombocytes were identified in addition to lymphocytes, plasma cells, monocytes, macrophages and one type of granulocyte which histochemically resembled the mammalian neutrophil. The evolution and development of the cells was also investigated and the various stages described.
142 citations
TL;DR: The results indicate that pike are well adapted for periods of prolonged starvation and that hepatic and extra-hepatic lipid and glycogen stores serve for metabolic needs during food shortage, while body protein is conserved.
Abstract: The effects of starvation and force-feeding on certain tissue and blood constituents were studied in the Northern pike, Esox lucius L Starvation resulted in a reduction of liver and muscle glycogen and liver lipid Blood glucose concentration and haematocrit were reduced, total plasma cholesterol levels were increased, while the levels of plasma free fatty acids (FFA), amio acid nitrogen and protein remained unaltered No significant changes were observed in either muscle protein, muscle water or the response to amino acid loading during the starvation period
The force-feeding of pike starved for 3 months resulted in liver lipid and muscle glycogen being increased to levels higher than those observed in freshly-captured fish Liver glycogen, however, increased to values only slightly higher than those of starved animals Furthermore, while force-feeding had little effect on plasma FFA or protein concentrations, blood glucose, plasma cholesterol and haematocrit returned to the levels found in freshlycaptured fish and those of amino acid nitrogen were higher
The results indicate that pike are well adapted for periods of prolonged starvation and that hepatic and extra-hepatic lipid and glycogen stores serve for metabolic needs during food shortage, while body protein is conserved The endocrine basis for these changes in the tissue and blood constituents is discussed
129 citations
TL;DR: The leucocytes of plaice were examined and, at a morphological level, in addition to their response to the injection of carbon particles, they could be divided into four main types; monocytes and thrombocytes were the only cells to take up appreciable amounts of the carbon.
Abstract: The leucocytes of plaice were examined and, at a morphological level, in addition to their response to the injection of carbon particles, they could be divided into four main types. Unlike previous reports, monocytes were seen. The neutrophil granules resembled the third granule type described in mammalian neutrophils. Monocytes and thrombocytes were the only cells to take up appreciable amounts of the carbon.
116 citations
TL;DR: The experiments dealt primarily with routine metabolic rates of schooling juvenile Atlantic menhaden, Brevoortia tyrannus (Latrobe), in flowing-water respirometers and were designed to obtain baseline data for energy flow models and studies on the effects of sublethal stresses.
Abstract: The experiments dealt primarily with routine metabolic rates of schooling juvenile Atlantic menhaden, Brevoortia tyrannus (Latrobe), in flowing-water respirometers and were designed to obtain baseline data for energy flow models and studies on the effects of sublethal stresses. The relationship of body weight to oxygen consumption as well as the effect of temperature (10–25°C), salinity (low, 5–10 p.p.t. and high, >28 p.p.t.), time since last fed and darkness on the routine metabolic rate was examined. The effect of salinity on growth of menhaden larvae into juveniles was also measured.
114 citations
TL;DR: The factors influencing the selection of food by flounders, Platichthys flesus (L.), have been investigated by analysing collections made in the Severn Estuary for 1 year and the results of experiments.
Abstract: The factors influencing the selection of food by flounders, Platichthys flesus (L.), have been investigated by analysing collections made in the Severn Estuary for 1 year and the results of experiments. Flounders measuring between 6–0 and 35 cm fed heavily on the polychaete Nereis diversicolor in February and on the amphipod Gammarus salinus between February and April. Thereafter these species were replaced by the mysid Neomysis integer with the decapod Crangon vulgaris. Flounders shorter than 6.0 cm, fed mainly on Neomysis integer regardless of month. Numerous factors were involved in the choice of the food including (1) the maximum and minimum length of prey, (2) its spatial distribution in the water column, (3) its degree of concealment, (4) its motility and ability to escape predation, (5) conditioning of the flounders for certain foods, (6) the fish's swimming speed and (7) the turbidity and temperature of the water.
Although the average length of ingested prey remained unchanged as the fish grew in size, an increase in the maximum and minimum lengths was observed. The percentage of stomachs that contained no identifiable remains in flounders greater than 6–0 cm averaged 80–95 % during part of the winter and 60% in the summer and between January and March. These changes partly reflected the influence of low water temperature on the metabolic rate and availability of prey. The dry weight of the stomach contents in flounders longer than 6–0 cm was lowest in winter but high values were recorded in the spring. This latter feature was probably because the rate of feeding was greater than that of digestion. During the summer, under more normal feeding conditions, the weight of the stomach contents remained relatively low compared to other fish populations. Flounders shorter than 6–0 cm always contained more food in their stomachs on a unit weight basis than larger individuals, reflecting metabolic rate and hunting efficiency.
109 citations
TL;DR: Growth rates were similar to those published for chub in other European waters, but the Stour chub were longer-lived and attained a greater ultimate size, and female chub grew faster than the males.
Abstract: Opercular bones from 399 chub from the River Stour, Dorset were used for age and backcalculated growth measurements. Scales were only used to aid the interpretation of difficult operculars. Annuli were laid down through the period mid-April to mid-June. Growth in length was minimal between October and March. Growth rates were similar to those published for chub in other European waters, but the Stour chub were longer-lived and attained a greater ultimate size. Female chub grew faster than the males. Spawning occurred from late May into June and elaboration of the gonads took place between September and May. Immature chub had an annual cycle of condition; the 0 group having a maximum in August and older immature fish reaching their maximum in June. Both categories had a minimum condition in early spring. The cycle of gonad development affected the condition of mature fish. The numbers of eggs in chub of lengths 359–467 mm ranged from 27 000–65 000. Some females attained sexual maturity at age V or VI, but most by age VII. The majority of males matured at age V, though some at ages III or IV. Growth rates and year-class strengths varied from year to year but independently of one another. Thirty-one per cent of chub aged II and over belonged to the 1959 year class. Young chub ate insect larvae and small crustacea, but the occurrence of fish and macrophytes was greater in the diet of older fish.
107 citations
TL;DR: Values for blood glucose and blood lactate were found to be lower in cyclostomes, holocephaleans and elasmobranchii than in most teleosts, and higher blood glucose levels were observed in the more active teleost species.
Abstract: Marine fishes caught in the Skagerrak, 27 different species representing various groups of fishes (Cyclostomi, Holocephali, Elasmobranchii and Teleostei), were examined for the following haematological and biochemical blood parameters: haematocrit, haemoglobin, mean corpuscle haemoglobin concentration, total plasma protein, blood glucose and blood lactate. Interspecies variations as well as variations within some species were observed. The haemoglobin values for all species showed a positive correlation to the corresponding haematocrit values. Relatively low values for haematocrit and haemoglobin were found in cyclostomes, holocephaleans and elasmobranchii compared to the majority of teleosts. Within the teleost group, the haematocrit and haemoglobin levels were positively correlated with the activity of the fish species. The cyclostome Myxine glutimsa L. had a total plasma protein content in the same range as most teleosts, whereas holocephaleans, elasmobranchii and the deep-water teleost Coryphaenoides rupestris Gunnerus showed comparatively low values. Among teleosts some relationship seemed to exist between the total plasma protein level and the activity of the fish species. In addition, a correlation between plasma protein content and levels of blood lipids were noted. Values for blood glucose and blood lactate were found to be lower in cyclostomes, holocephaleans and elasmobranchii than in most teleosts. Higher blood glucose levels were observed in the more active teleost species.
TL;DR: Observations on spawning and movements of trout over 7.5 km of chalkstream indicate five discrete stages of the life history with respect to migrations, reflecting the juxtaposition of areas suitable for all stages.
Abstract: Observations on spawning and movements of trout over 7.5 km of chalkstream indicate five discrete stages of the life history with respect to migrations. (1) Downstream movements from area of hatching to nursery areas, to 6 months of age. (2) Downstream again from the nursery areas to areas of adult growth between 6 months and 15 months of age. (3) A stage of very limited movements by adults between 15 months old and spawning. (4) Upstream spawning migration. (5) Downstream movements following spawning. These movements are similar in principle to those in upland systems though are relatively more local, reflecting the juxtaposition of areas suitable for all stages.
TL;DR: Changes in fat and moisture content of the body, however, were such that Kin terms of energy utilization was independent of body size when the fish were feeding at the same level, and provides a base-line for comparison with the performance of other more complicated systems.
Abstract: Three size classes (3 g, 200 g, 1–3 kg) of rainbow trout, Salmo gairdneri Richardson, were each fed five rations ranging from zero to a ‘maximum’ ration and the relationships among body size, food ration, metabolism and growth examined. Water temperature was constant at 11–4°C. The gross growth efficiency in wet weight, K, increased asymptotically with increasing ration but decreased with increasing body size. Changes in fat and moisture content of the body, however, were such that Kin terms of energy utilization was independent of body size when the fish were feeding at the same level. This result was not apparent when wet weight values only were considered and use of a constant to convert wet weight offish to calorific values can lead to errors in interpretation of results. Assimilation efficiency averaged 71 -7 % over all feeding groups and was independent of body size and food ration. Total metabolic expenditure, however, increased with increasing body size and feeding level, but at any given feeding level a similar proportion of the energy of the assimilated ration was used for metabolism. At a single feeding level, therefore, the percentage utilization of energy in each category of the energy budget remained similar over all body sizes. Such a result can only be expected under laboratory conditions but it provides a base-line for comparison with the performance of other more complicated systems.
TL;DR: It is concluded that the presence of M. cerebralis is not an important limiting factor in salmonid fanning per se but only limits methods of production.
Abstract: The literature describing the biology and control of Myxosoma cerebralis (whirling disease) is reviewed. New data on the world distribution of the parasite are presented. It is concluded that the presence of M. cerebralis is not an important limiting factor in salmonid fanning per se but only limits methods of production.
TL;DR: It is likely that a strain resistant to a pH below 4.1, the previously recorded lower limit, can be developed by selective breeding.
Abstract: Survival time of brook trout (Salvelinus fontinalis Mitchill) at low pH was directly related to size, and inversely related to temperature. Between pH 2.50 and 3.25 an increase in pH by increments of 0.25 each led to a 2–3 fold increase in survival time. At higher pH's (3.25–3.75) elevations in pH by the same increments each produced a 3–5 fold increase. Brook trout tested at pH 3.35 and 3.50 showed maximum survival times in June-August. Members of seven inbred lines of brook trout were tested for acid tolerance; the lines differed markedly providing strong evidence that acid tolerance is hereditary. Tests involving either intercrossed or backcrossed offspring of tolerant or intolerant parentals demonstrated intermediate survival in 12.5% of all experiments and heterosis in 66.7% of the tests. Differences in survival of inbred lines were the most marked at pH 3.25. Exposure for 1 week at pH 3.75 resulted in a 20–25% decrease in survival time of 18 fish tested at pH 2.50 and 3.00. Out of a total of 24 trout (17 g) tested at pH 3.75 two highly tolerant individuals were still alive after 6.1 weeks. Thus it is likely that a strain resistant to a pH below 4.1, the previously recorded lower limit, can be developed by selective breeding.
TL;DR: Pike growth in the two rivers was comparable with the fastest growth in other waters, though Frome pike grew slightly faster than Stour pike, while the percentage of empty stomachs was highest in Stour samples taken during the summer, shorter digestion times and longer feeding periods in this period are suggested as reasons for the apparent anomaly.
Abstract: Opercular bones of 261 pike from the River Stour and 117 from the River Frome were used for age and back-calculated growth determinations. The annuli were laid down during late April and early May and most growth occurred between May and September. Pike growth in the two rivers was comparable with the fastest growth in other waters, though Frome pike grew slightly faster than Stour pike. Spawning occurred from the end of March into May. Elaboration of the ovaries commenced in September and was virtually completed by February, whereas the testes reached their maximum weight in October and maintained it until spawning. Immature pike had an annual cycle of condition reaching a maximum in May and a minimum during the winter. The gonad cycle affected the condition of mature females which had their minimum condition in mid-summer. The fecundity of Stour pike is expressed by the formula: log10 egg number =3.56 log10 fish length (mm) – 5.40. Approximately 75% of all Stour pike were sexually mature by age II and these fish were, on average, larger than immature pike of the same age. The most numerous items in the diet of pike were small cyprinids, 30–80 mm fork length, although pike over 700 mm long ate larger fish. Few salmonids appeared in the diet of either Frome or Stour pike. The percentage of empty stomachs was highest in Stour samples taken during the summer, shorter digestion times and longer feeding periods in this period are suggested as reasons for the apparent anomaly.
TL;DR: A theoretical approach to the factors regulating fish production from river systems is proposed which gives an estimate of annual yield of 530 000 t of fish at present levels of catch, which resembles a theoretical figure derived from the basin area.
Abstract: The factors regulating fish production from river systems remain poorly studied and understood. Rivers conform to physical and chemical laws which determine their morphology. From these laws relationships are calculated which estimate the total length and number of streams of different order on the African continent. Edaphic factors very less than morphological ones and the chemical and physical conditions in the major river channels tend to resemble each other closely. The present catch from African rivers, evaluated from catch statistics, by country and by river system, resembles a theoretical figure derived from the basin area. However, these statistics are drawn only from major fisheries and there remain a very large number of smaller streams whose production does not enter into this calculation. A theoretical approach to this problem is proposed which gives an estimate of annual yield of 530 000 t of fish at present levels of catch. Deviations from the theoretical yield in individual river systems arise from differences in both edaphic and morphological characteristics.
TL;DR: Review of the biomedical literature suggests the observed effects of sodium lauryl sulphate on gill cells correspond to the two mechanisms by which detergents cause death in isolated cells.
Abstract: The pathological effects often lethal concentrations of the anionic detergent, sodium lauryl sulphate, on the gills of Salmo trutta L. have been studied by light and electron microscopy. At concentrations to 120 mg/1 (medium survival times >1 h), epithelial cell death is associated with lysosome formation. Acute inflammation of the gill tissue, extensive detachment of the epithelium and, except at the lowest concentrations, collapse of the pillar cell system occur. At concentrations above 120 mg/1 (medium survival times <1 h) very rapid lysis of cells results in the complete disruption of cellular and tissue structure. Changes in the gross structure of the gills are explainable in terms of the rate and nature of toxic action at the cellular level. Review of the biomedical literature suggests the observed effects of sodium lauryl sulphate on gill cells correspond to the two mechanisms by which detergents cause death in isolated cells. These are autolysis, i.e. lysis by the action of the cell's own enzymes, induced by an initial lesion in the cell membrane whose precise nature is not known; and rapid lysis by the direct action of the detergent on the cell constituents.
TL;DR: The objectives of the study were to determine the chemical constituents of rainbow trout during the first 14 months of life, to study the effects of starvation on the body composition of trout, and to measure organ weights during the early years of life.
Abstract: The objectives of the study were to determine the chemical constituents of rainbow trout (Salmo gairdneri) during the first 14 months of life, to study the effects of starvation on the body composition of trout, and to measure organ weights during the first 14 months of life.
Body fat and protein content as a percentage of body weight increased with age, the water content declined, and the ash content remained constant during the first 14 months of life. There were no significant differences in body composition between immature male and female rainbow trout. Total body ions as a proportion of ash content decreased until the 10th month and then began to increase. During starvation, fat was used as the primary source of energy while water and ash content increased and protein content remained constant as a percentage of body weight.
The gall bladder, liver, and air bladder remained relatively constant as a percentage of body weight during the first year of life. As body weight increased, the relative weight of brain, heart, and digestive system decreased while the gonad and spleen weight increased.
TL;DR: 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.
Abstract: 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.
TL;DR: Sea trout sampled by shore seining in the sea lochs of the west coast of Scotland between 1970 and 1974 supported the evidence from smolt trapping and beach seine catches that, in the first post-migration year, the smolts migrate from the rivers from late March to early May, they then migrate to the seaLochs in May and June and return in late summer and autumn.
Abstract: Sea trout were sampled by shore seining in the sea lochs of the west coast of Scotland between 1970 and 1974, This area is of special interest because of the indentation of the coastline and the varying degree of freshwater and marine influence in the sea lochs The majority of fish caught were in their first year after smolt migration These post-smolts were caught mainly in May and June, after which the number of trout present was low until fish at the ‘whirling’ stage appeared in the catches at the end of August, continuing through to the following spring An additional recruitment of mainly unsilvered young trout from the rivers to the sea lochs was found in the autumn Age and sex composition of both spring and autumn recruits, and of mature fish, were investigated and compared
A total of 3228 sea trout were tagged, with 311 recaptures These recaptures supported the evidence from smolt trapping and beach seine catches that, in the first post-migration year, the smolts migrate from the rivers from late March to early May, they then migrate from the sea lochs in May and June and return in late summer and autumn
TL;DR: This comprehensive review by Dr Michael Gardner collates and summarizes the findings of investigations from the turn of the century to the present day and provides an objective assessment of several hypotheses relating to the reasons for the diverse behaviour patterns of the salmon.
Abstract: The many enigmatic factors in the life cycle of the Atlantic salmon have long fascinated and long frustrated those working on this subject. This comprehensive review by Dr Michael Gardner collates and summarizes the findings of investigations from the turn of the century to the present day. The author also provides an objective assessment of several hypotheses relating to the reasons for the diverse behaviour patterns of the salmon.
TL;DR: Forty-five species of parasitic organisms from viruses to Metazoa were recognized from striped bass and heavy infections by some were associated with definite pathological conditions.
Abstract: A survey to determine presence of parasitic and disease organisms and their effect on estuarine populations of striped bass, Morone saxatilis (Walbaum), was conducted monthly from May 1972 to May 1973. A total of 514 fish over 1 year old and 140 young-of-the-year were examined using standard necropsy and histological procedures. Other species of fishes were studied to determine the specificity of striped bass parasites and to determine if other fishes were reservoirs for striped bass pathogens. Forty-five species of parasitic organisms from viruses to Metazoa were recognized from striped bass. Heavy infections by some were associated with definite pathological conditions.
TL;DR: In the interval between successive spawnings, female sticklebacks consumed approximately their own wet weight of Tubifex, and total production (the summation of egg production and somatic growth) was a function of the amount of food consumed.
Abstract: In the interval between successive spawnings, female sticklebacks consumed approximately their own wet weight of Tubifex. On average, for 100 cal of food consumed, 26 cal of eggs, 3 cal of somatic growth and 11 cal of faeces were produced. In the absence of somatic growth, the efficiency of egg production was estimated as nearly 30%, and it was predicted that in the absence of egg production, the efficiency of somatic growth would range from 20% for a fish of 0.8 g wet weight to 3% for 2 g fish.
The weight of eggs produced at a spawning was a function of the weight of the female but not of the amount of food consumed. If food consumption was not sufficient to cover the cost of egg production, the fish lost weight. Total production (the summation of egg production and somatic growth) was a function of the amount of food consumed.
TL;DR: Evidence is discussed which shows that the bulbus arteriosus in teleosts is morphologically and biochemically distinct from the ventral aorta, and is probably of cardiac origin rather than an expansion of the posterior end of the aorte as generally supposed.
Abstract: The rate of expansion in volume of the bulbus arteriosus with increase in pressure is measured. From this it is calculated the elastic rebound of the bulbus can account for approximately 25 % of blood flow in the ventral aorta; this proportion decreases as cardiac output increases. The structure of the wall of the bulbus is shown to consist of a compact outer layer with a series of separate longitudinal elements on the inner surface. These elements are connected to the compact layer by numerous radial fibres. This structure equalizes strain in all the structural elements of the wall during large changes in volume. Evidence is discussed which shows that the bulbus arteriosus in teleosts is morphologically and biochemically distinct from the ventral aorta. The bulbus is probably of cardiac origin rather than an expansion of the posterior end of the aorta as generally supposed.
TL;DR: It is concluded that most of the caesium accumulated by the brown trout from water enters other than by the gut, probably through the gills, but as with plaice and ray, the main source of theCaesium, possibly 90%, must come from the food.
Abstract: The patterns of accumulation of caesium-137 from water by the tissues and organs of the freshwater teleost, the brown trout (Salmo trutta) are described. Estimates of the biological half-times and steady-state concentrations are derived, using a simple exponential equation. In all tissues and organs examined, other than muscle, the rate processes of the trout fall between those of the plaice and the ray. It is concluded that most of the caesium accumulated by the brown trout from water enters other than by the gut, probably through the gills, but as with plaice and ray, the main source of the caesium, possibly 90%, must come from the food. Despite differences in the levels of accumulation, the ratios of the tissue to blood steady state concentrations are very similar in all three species. The steady state caesium concentration of the blood appears to be directly related to the red blood cell count of the fish.
TL;DR: The diet of sea trout in some of the sea lochs of the west coast of Scotland was investigated and availability of food was the main factor influencing the presence or absence of trout.
Abstract: The diet of sea trout in some of the sea lochs of the west coast of Scotland was investigated. The contents of 986 sea trout stomachs from the Loch Etive area (1970–1973), and 291 stomachs from the Loch Eil area (1964–1973), were examined and the composition of the diet, seasonal changes and the effect of trout size were analysed using frequency of occurrence, dry weight and number of organisms methods. Benthic feeding (crustacea and annelids) was more important in winter while midwater and surface organisms (young fish and insects) were preferred in summer. Young fish (mainly clupeids and sand eels) featured more in the diet of larger trout (≤21 cm) than in the smaller size range (≥21 cm). Surveys of 24-h were completed in June and September, 1972, and indicated that availability of food was the main factor influencing the presence or absence of trout. Bottom feeding was greatest during the day while the amount of midwater and surface feeding tended to increase between sunset and sunrise.
TL;DR: Goldfish exposed to sublethal levels of cadmium for periods of 25 and 50 days exhibited significant deviations in plasma sodium and chloride levels as well as in tissue sodium and water content, and these parameters may provide useful indices of Cadmium effects at sublethal concentrations.
Abstract: Goldfish were exposed to sublethal levels of cadmium (means of 44.5 and 380 μg Cd++/l) for periods of 25 and 50 days, and their water-electrolyte status evaluated by reference to plasma and muscle levels of sodium, potassium and chloride and muscle water content. Significant changes in plasma chloride, tissue potassium and tissue water content were observed after 25 days in both test solutions. Specimens held at the more dilute cadmium concentration were apparently able to compensate for most of the initial cadmium effect and, after 50 days exposure, were characterized only by a continuing depression in plasma sodium level. This suggests that the cadmium MATC value for this species under the conditions employed is probably less than 45 μg Cd++/l. Goldfish exposed to 380 μg Cd++/l for 50 days exhibited significant deviations in plasma sodium and chloride levels as well as in tissue sodium and water content, and these parameters may provide useful indices of cadmium effects at sublethal concentrations.
TL;DR: The reef–dwelling goat–fishes, Pseudupeneus maculatus (Bloch) 1793 aand Mulloidichthys martinicus (C. & V.) 1829, form a small, but valuable, component of fish–trap catches in the Caribbean Sea and adjacent regions.
Abstract: The reef–dwelling goat–fishes, Pseudupeneus maculatus (Bloch) 1793 aand Mulloidichthys martinicus (C. & V.) 1829, form a small, but valuable, component of fish–trap catches in the Caribbean Sea and adjacent regions. Investigations of these species in Jamaican waters have covered relative and absolute growth rates, spawning seasons, sizes at maturity, distribution patterns, size compositions of populations, relative abundances and mortality rates. Previous literature concerning the biology and ecology of these species is reviewed.
TL;DR: The factors influencing the selection of food by eels, Anguilla anguilla, whiting, Merlanglus merlangius, sprat, Sprattus sprattus, and stickleback, Gasterosteus aculeatus have been investigated by analysing collections made in the Severn Estuary for 1 year.
Abstract: The factors influencing the selection of food by eels, Anguilla anguilla, whiting, Merlanglus merlangius, sprat, Sprattus sprattus, and stickleback, Gasterosteus aculeatus have been investigated by analysing collections made in the Severn Estuary for 1 year. Non–migratory (yellow) eels measuring from 19–5–56–5 cm in length fed mainly on either the decapod Crangon vulgaris or on the mysid Neomysis integer during the warmer months but ceased to feed in the winter. Whiting measuring between 2–5 and 15 cm fed almost exclusively on C. vulgaris, N. integer and the sand goby, Pomatoschistus minutus. Sprats fed chiefly on either the arnphipod Gammarus salinus or N. integer. Sticklebacks seldom contained any food in their stomachs despite the presence of large quantities of suitable prey and the high level of hunting efficiency.
Gammarus salinus, although normally abundant in the environment, was usually ingested in disproportionately small quantities by all fishes except sprats reflecting its concealment among floating weeds and a selection against small (less than 1 cm) organisms. Because of the limitations of size and the unusually efficient escape reaction of larger animals, only young representatives of Crangon vulgaris were captured. The isopod Eurydice pulchra was rarely eaten by any of the fishes even though it was common in the environment. Burrowing polychaetes, mainly Nereis diversicolor, were never utilized possibly due to the difficulty involved in removing these organisms from the substrate. Neomysis integer was the most frequently consumed organism. Although the average length of prey ingested by the whitings increased with the size of fish, this was not the case for the other species. The proportion of non–feeding eels and the dry weight of stomach contents of this species depended on the temperature of the water but were not related to the availability of prey and tidal conditions whereas the feeding of whiting could not be related to any environmental parameter.