bluuebunny/crossref_metadata_2025 huggingface dataset:
The reproductive biology of Scleropages formosus (Müller & Schlegel) (Osteoglossomorpha, Osteoglossidae) in Malaya, and the morphology of its pituitary gland
Authors: Scott D. B. C. , Fuller J. D.
Published: January 2006

This is a study of the reproductive biology and morphology of the pituitary gland of the osteoglossid fish Scleropages formosus (Müller & Schlegel). The fish spawn in the Tasek Bera waterways of Pahang, Malaysia during the rainy season beginning in August. Young fish are incubated in the mouth of the male parent until free‐swimming. Males mature in their 2+ year, when 30–45 cm in length. In mature specimens the testis is small, and little sperm is produced. Some females mature in their 2+ year, although at that time, most have only reached the stage of secondary oocyte production. The chorion and follicular granulosa of secondary oocytes are deeply invaginated into the cytoplasm. All fish spawn in their 3+ year, when 45–60 cm in length. The single ripe ovary contains 20–30 ova, each 1.9 cm in diameter. No fish of 4+ years were caught, which may be the result of mortality or emigration, or due to extraneous causes such as selectivity in the fishing techniques used.

The pituitary gland accords with the generalized teleost pattern and embryonic development. There is no saccus vasculosus. Adrenocorticotropic cells predominate in the proadenohypophysis, and somatotropic and luteotropic cells occur here. The mesoadenohypophysis contains gonadotropic and somatotropic cells; the former grow large in ripe specimens, so that the mesoadenohypophysis becomes much enlarged. The metaadenohypophysis contains relatively few cells, much neurohypophyseal ramification, and is deeply penetrated by the third ventricle of the brain.
Observations on the age, growth, reproduction and food of the pike Esox lucius (L.) in two rivers in southern England
Authors: Mann R. H. K.
Published: January 2006

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.
Age, growth and length‐weight relationship of brown trout Salmo trutta (L.) in the Loch of Strathbeg, Aberdeenshire
Authors: Treasurer James W.
Published: January 2006

Most age and growth studies on brown trout in British lakes have been restricted to highland or moorland areas. In the unusual environment of a coastal dune lake (Loch of Strath‐beg, Aberdeenshire) the trout population was short‐lived with few fish surviving longer than three years. Growth was rapid compared with other naturally‐stocked lakes. Growth in length and weight differed between 1–and 2–migrants. Faster growth in the burn was the factor causing early migration by 1–migrants (71% of population), but both groups grew at the same rate on entering the loch. The effect of gill‐net selection on the estimation of the length‐weight relationship was demonstrated. A small difference was found in the length‐weight relationship among the mature stages. Factors responsible for rapid growth and small age‐range of the population are discussed.
The host specificity of Lepeophtheirus pectoralis (Müller, 1776) (Copepoda: Caligidae)
Authors: Boxshall G. A.
Published: January 2006

The host specificity of Lepeophtheirus pectoralis (Müller) was examined experimentally by exposing different fish species to infection by artificially reared copepodid larvae. Copepodids which were hatched from eggs of adults parasitic on plaice (platessae copepodids) preferred plaice to all other fishes tested, whereas copepodids which were hatched from eggs of adults parasitic on flounder (flesi copepodids) preferred flounder to all other fish species. These behavioural differences suggest that two strains of L. pectoralis exist, one (platessae) adapted to plaice as its host and the other (flesi) to flounder. Comparison of an experimentally derived order of host preference with a table of occurrence obtained from the literature, suggests that a third strain of L. pectoralis, adapted to dab as its host, might also occur.

The process of infection by L. pectoralis copepodids is also described. It comprises a host location phase, during which the copepodid enters the habitat of its flatfish hosts and locates a host individual, and an attachment phase. The host location phase appears to be governed by changes in the activity of the copepodid and by its positively rheotactic response to water currents produced by the host. The attachment phase is probably based on the response of the copepodid to chemical factors produced by the host.
The distribution and pathogenicity of larvae of Eustrongylides (Nematoda) in brown trout Salmo trutta L. in Fernworthy Reservoir, Devon
Authors: Kennedy C. R. , Lie S. F.
Published: January 2006

Infections of brown trout Salmo trutta L. by larvae of the nematode Eustrongylides sp. were studied over a period of two years in Fernworthy Reservoir, Devon. The parasite, here as elsewhere in Britain, is acquired only in the lake itself and not in the streams feeding it. Both native and introduced brown trout were infected but not rainbow trout which did not survive sufficiently long in the reservoir. The parasite showed a preference for female fish and for fish over 20 cm in length. Since these latter were approaching the end of their natural life span in the lake, there was insufficient time for the parasites to accumulate in older fish. No seasonal changes in infection levels or size composition of the parasite population were recorded. The larvae occurred in capsules, the majority of which were attached to the stomach wall. No local pathological effects associated with the capsules were observed and infested fish were of similar length, weight and condition to uninfected ones. The absence of harmful effects upon the trout in Fernworthy Reservoir is compared and contrasted with the effects of the parasite in other localities. It is concluded that although Eustrongylides can occasionally cause damage to some species of fish, there is no conclusive evidence that it does so to trout. but its unsightly appearance and harmful effects on birds renders it an undesirable parasite in any fishery.
The hepato‐renal syndrome in cultured turbot (Scophthalmus maximus L.)
Authors: Anderson C. D. , Roberts R. J. , MacKenzie K. , McVicar A. H.
Published: January 2006

The histopathology of biliary hyperplasia and renal calcinosis, associated with infections of two parasites, Myxidium incurvatum and Rhabdospora thelohani, is described in turbot, Scophthalmus maximus (L.), from Scottish marine fish farms and wild populations. Liver and kidney lesions were divided into four, and parasite infections into five grades of severity. A few of the fish examined were not parasitized, but every one showed some evidence of pathological change, even the apparently normal individuals from all populations. Although there is a positive association between the parasitic and pathological data, parasitism is not considered to be the principal cause of either the hepatic or renal lesion; the evidence suggests rather a secondary opportunist role for the parasites. The general severity of the condition in captive stocks suggests that the cause may lie in the fundamentals of present techniques of turbot husbandry, but no specific agent has been identified. A case is put forward for considering Rhabdospora to be a parasite rather than a specialized host cell.
Lymphocystis disease in Baltic herring (Clupea harengus var. membras L.)
Authors: Aneer Gunnar , Ljungberg Olle
Published: January 2006

Lymphocystis disease has been demonstrated in herring from three different areas of the Baltic Sea. An investigation was made from April 1971‐December 1973 in the fishing grounds near the Askö Laboratory. A total of 2629 herrings from randomly selected samples were examined, 14 of which were found to be affected with lymphocystis disease. The relative incidence of the disease varied from 0–2.7% in different samples, and was higher in 1972 (1%) than in 1971 (less than 0.1%). Of 42 diseased herrings with skin lesions 12 also had lesions in internal organs. The lymphocystis cells were usually single in the skin as well as in internal organs, and had a diameter of 1–2 millimetres. They were histologically similar to lymphocystis cells described from other species. Virions with a mean diameter of 300 nm, morphologically similar to earlier descriptions of lymphocystis virus, were also demonstrated.
Cost of egg production in the three‐spined stickleback (Gasterosteus aculeatus L.)
Authors: Wootton R. J. , Evans G. W.
Published: January 2006

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.
Multiple globins and haemoglobins in the bass, Dicentrarchus labrax (L.) (Serranidae: Teleostei)
Authors: Perez Julio E. , Maclean Norman
Published: January 2006

The haemoglobins and globins of bass, Dicentrarchus labrax (L.) have been studied by starch and polyacrylamide gel electrophoresis. Five haemoglobin components were found. These haemoglobins appear to result from the combination of four different globin monomers. The molecular weight of the pooled haemoglobin is about 54 400, confirming its tetrameric form. The evolutionary significance of multiple haemoglobins is discussed.
Comparative studies of inorganic substances in the blood of fishes from the Scagerac Sea
Authors: Fäunge Ragnar , Lidman Ulf , Larsson ÅKe
Published: January 2006

The concentrations of the main plasma inorganic electrolytes Na+, K+, Ca2+, Mg2+, Cl‐ and and PO43‐ have been determined for different orders of marine fishes. For Na+ and Cl‐ a typical decrease was found when passing from cyclostomes, holocephalans and elasmobranchs to teleosts. The concentrations of K+, Ca2+ and Mg2+ showed a similar trend except that there was a rise in the teleost group, which showed a large range of variation for these three ions. In the case of PO43‐ no significant differences between groups were found.
Osmotic stress and mortality in adult American shad during transfer from saltwater to freshwater
Authors: Leggett William C. , O'Boyule Robert N.
Published: January 2006

Thirty‐five adult American shad (Alosa sapidissima) were moved quickly (2.5 h) from saltwater to freshwater. Changes in the levels of osmotically active blood constituents and of mortality were observed during and after the transfer. These were compared with levels of corresponding constituents and of mortality in 20 shad maintained in saltwater under similar conditions and to 44 shad sampled immediately after capture in saltwater and in freshwater (40 km from the saltwater‐freshwater interface). Sodium and chloride levels in theblood of the transferred group declined sharply during and after transfer. Calcium, glucose and lactic acid levels increased, and potassium and magnesium levels remained stable. Transferred shad experienced heavy mortality beginning 5 h after the initial reduction in salinity associated with movement into freshwater. No mortality was experienced in the group held in saltwater.

It was concluded that the extensive meandering exhibited by adult shad at the upper limit of the salt‐freshwater interface during their spring migration in the Connecticut River is a behavioural response designed to slow the transition from the saltwater to the freshwater environment, thereby minimizing the physiological stress involved and/or allowing full recovery from this stress before proceeding upriver.
Effects of exposure to sublethal levels of cadmium upon water‐electrolyte status in the goldfish (Carassius auratus)
Authors: McCarty L. S. , Houston A. H.
Published: January 2006

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.
Increased oxygen consumption in blennies (Blennim pholis L.) exposed to their mirror images
Authors: Wirtz P. , Davenport J.
Published: January 2006

The sight of its mirrored image increases the oxygen consumption of Blennius pholis. This is due to an increased metabolic rate and an increased activity. For schooling species, the opposite effect has been reported in the literature and has been termed the ‘group effect’. The B. Pholis response is discussed in relation to species specific preferences of the social environment. The hypothesis is put forward that deviations form the preferred social environment cause an activation of the individual.
Abnormalities of the gonads of carp
Authors: Gupta S. , Meske CH.
Published: January 2006

Cyprinus curpio is usually dioecious, with well–developed paired gonads (ovaries or testes) of which the two parts are approximately equal in weight. However, a few instances of abnormal development have been observed. In one male fish, the right testis developed normally to maturity, while the left testis was vestigial. In a female fish, only the right component of the ovary was present. Some monoecious, synchronous hermaphrodite specimens have also been observed, and self fertilization demonstrated experimentally. It has been shown (Kossmann, 1971) that the progeny of such synchronous hermaphrodites may also have this characteristic. These studies demonstrate that even such a highly evolved teleost as the Carp may retain the primitive characteristic of hermaphroditism.
The effects of temperature and salinity on Tilapia rendalli Boulenger 1896
Authors: Whitfield A. K. , Blaber S. J. M.
Published: January 2006

Temperature and salinity tolerances of Tilapia rendalli were determined experimentally. Results indicate that they are tolerant over a wide range of temperatures (11‐37°C), but are incapable of surviving in salinities above 19‰ The maximum salinity tolerance is at temperatures between 20–28°C. The osmotic concentration of the blood rises from 255 mosmol/1 in freshwater to 340 mosmol/1 in a salinity of 19‰T. rendalli is restricted to the warmer waters of the Zambezi river system in central Africa and southwards to the Pongolo river, as well as certain tropical and subtropical brackish water lagoons and lakes. Evidence from these experiments suggest that the distribution of T. rendalli isgoverned by both temperature and salinity.
A high power pulse generator for electric fishing – revised circuit
Authors: Weiss D. M.
Published: January 2006

A circuit for a pulsed d.c. fishing machine is described which represents substantial advantages over a previously published design. The present circuit has been fully field tested and is giving satisfactory service in routine fish population sampling in high conductivity water (up to at least 2000 μS/cm).
Sea trout in North Argyll sea lochs: II. diet
Authors: Pemberton R.
Published: January 2006

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.
A method of comparing the efficiencies of electric fishing operations*
Authors: Cross D. G.
Published: January 2006

A method is described whereby the efficiencies of two electric fishing machines may be compared by fishing a closed population on eight occasions at short intervals, the two fishing machines being used alternately. A practical example is given and the merits of the method are discussed.
Parasites and diseases of striped bass, Morone saxatilis (Walbaum), from the lower Chesapeake Bay
Authors: Paperna I. , Zwerner D. E.
Published: January 2006

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.
Oxygen consumption by sticklebacks (Gasterosteus aculeatus L.) exposed to zinc
Authors: Brafield A. E. , Matthiessen P.
Published: January 2006

The rate of oxygen consumption by sticklebacks has been studied by long‐term continuous‐flow respirometry. Exposure to 1 p.p.m. zinc in calcium‐free water causes wide variations in individual responses, but oxygen uptake tends to rise and then become extremely erratic, before declining as death approaches. Behavioural abnormalities such as increased ventilation rate, loss of balance, and long periods of inactivity alternating with spasmodic swimming also occur. Exposure to 6.5 p.p.m. zinc in high‐calcium water generally causes a rise in oxygen consumption, followed by fluctuations in the rate of uptake, but no behavioural abnormalities occur and deaths are rare even after exposure for 400 h. If restored to zinc‐free water after 40 h exposure to zinc, recovery is generally complete, although fluctuating rates of oxygen uptake persist. These results are discussed in relation to previous work on the effects of heavy metals on fish respiration.
The basis of food selection in some estuarine fishes. Eels, Anguilla anguilla (L.), whiting, Merlangius merlangus (L.), sprat, Sprattus sprattus (L.) and stickleback, Gasterosteus aculeatus L.
Authors: Moore J. W. , Moore I. A.
Published: January 2006

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.
Precipitating activity in the sera of plaice, Pleuronectes platessa L. to a helminth antigen
Authors: Harris J. E. , Cottrell B. J.
Published: January 2006

An antigen abstract of Proleptus obtusus an intestinal nematode of the common dogfish has been shown to precipitate with a serum component of plaice. As the parasite has never been shown to infect plaice it is suggested that perhaps the serum component might be C–reactive protein (CRP). However, characterization of the component revealed that it was specific immunoglobulin analagous to antibody of the IgM class. It is suggested the helminth antigen involved is cross–reacting with a common antigen to which the plaice is normally exposed.
Movements of brown trout Salmo trutta L. in a chalk stream
Authors: Solomon D. J. , Templeton R. G.
Published: January 2006

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.
Use of electroanaesthesia with freshwater teleosts: some physiological consequences in the rainbow trout, Salmo gairdneri Richardson
Authors: Madden Jane A. , Houston Arthur H.
Published: January 2006

Electroanaesthesia prompts both immediate and longer term alterations in the physiological status of the rainbow trout. These are not, by comparison with the related brook trout, more extensive than those associated with tricaine methane sulphonate (MS 222) anaesthesia. Changes in haemotological indices are minimized, while the spontaneous resumption of cardiovascular‐respiratory activity, and the character of variations in plasma electrolyte levels suggest that blood gas tensions and acid‐base status may be less affected by electroanaesthesia than by chemical anaesthesia. Moreover, recovery, in the control levels proceeded more rapidly in several instances. It is concluded that electroanaesthesia offers a useful alternative to chemical methods of anaesthesia.
Studies on Ligula intestinalis (L.) effects on a roach population in a gravel pit
Authors: Sweeting R. A.
Published: January 2006

The effects of the plerocercoids of Ligula intestinalis were studied on a population of roach, Rutilus rutilus in a gravel pit. The incidence of the cestode fell from 92% in 0+ roach in April to 25 % in January of the succeeding year. The fall in the number of parasitized fish was due to predation, mainly by pike, Esox lucius. Observations indicated most of the parasitized fish failed to become sexually mature although the actual growth rate of the fish was not markedly reduced. The plerocercoids of L. intestinalis grew more rapidly during the summer. The author recommends roach of less than 9 months of age should not be introduced into confined water such as a gravel pit, since after this period they appear to be much less likely to be parasitized.
Morphology of androgenetic and gynogenetic grass carp, Ctenopharyngodon idella (Valenciennes)
Authors: Stanley Jon G. , Jones Jack B.
Published: January 2006

Crosses between female carp x male grass carp resulted in androgenetic grass carp and hybrids. Fertilizing grass carp eggs with carp milt that had been irradiated with ultraviolet light for 15 min at 1.0 mW/cm2 produced gynogenetic grass carp. We compared the morphology of experimental progeny with that of the parental species to determine if inheritance was strictly matroclinous in gynogenesis and strictly patroclinous in andro‐genesis. Dorsal and anal fin rays, lateral line scales, gill rakers, pharyngeal teeth, and the relative length of the dorsal fin all suggested that gynogenetic grass carp were identical with the maternal species and androgenetic grass carp with the paternal species. Hybrids were intermediate between the parents except that the number of anal rays was identical with that in carp. The number of dorsal rays, the body depth, and the pharyngeal teeth in hybrids were more like those in carp than in grass carp, whereas the number of gill rakers was more similar to that in the paternal species.
Long‐term changes in the size of the Pomphorhynchus laevis (Acanthocephala) population in the River Avon
Authors: Kennedy C. R. , Rumpus A.
Published: January 2006

Samples of Gammarus pulex and dace, Leuciscus leuciscus, taken from the River Avon, Hampshire, at intervals over a period of 9 years were examined for the presence of the acanthocephalan. Pomphorhynchus laevis. Changes in the incidence and intensity of infection of P. laevis in dace and in G. pulex and in the frequency distribution of P. laevis in dace were used as indicators of the population size of the parasite. Throughout the period of observation, the parasite showed a similar pattern of distribution along the length of the river, although at some sites its abundance varied from year to year. Levels of both incidence and intensity of infection of P. laevis in both hosts at one specific locality remained fairly constant over the 9‐year period, and the annual variations fell within the natural range of monthly variation over any 12‐month period. The frequency distribution of P. laevis in dace also exhibited a similar pattern throughout the period. It was thus concluded that the population size of P. laevis had not changed to any great extent over the 9 years. The factors responsible for this constancy are discussed in the light of conclusions drawn from earlier work.
The food and feeding habits of the catfishes, Chrysichthys walkeri (Gunther), Chrysichthys filamentosus (Boulenger) and Chrysichthys nigrodigitatus (Lacépède) in theLekki Lagoon, Nigeria
Authors: Ikusemiju Kola , Olaniyan C. I. O.
Published: January 2006

A total of 1436 specimens were examined in the study of the food habits of the three Chrysichthys species in Lekki Lagoon. Certain differences were found in their food habits. Chrysichthys walkeri fed mostly on insects, Chrysichthys filamentosus on crustaceans and Chrysichthys nigrodigitatus on molluscs. It is suggested the observed diversity in feeding habits might be due to an active response to interspecific competition.
Control of whirling disease (Myxosoma cerebralis): effects of drying, and disinfection with hydrated lime or chlorine
Authors: Hoffman Glenn L. , O'Grodnick Joseph J.
Published: January 2006

Thorough air drying of contaminated mud killed the spores of Myxosoma cerebralis. Treatment of simulated earthen ponds with hydrated lime with up to 4550 g/m2 on the wet mud did not kill all of the spores. Treatment of simulated earthen ponds with up to 1200 p.p.m. chlorine did not kill all of the spores, however, treatment of contaminated water with 10 p.p.m. chlorine did kill the spores.
Age, growth and natural mortality rates of some cichlid fishes of Lake Malawi
Authors: Tweddle D. , Turner J. L.
Published: January 2006

The growth rates, lengths at maturity, fecundity and natural mortality of several cichlids of importance in trawl catches in Lake Malawi are described. Growth rates were determined by analysis of length frequency data from trawl catches. The breeding season for each species was determined by monthly examination of the gonads, and fecundity determined by egg counts from ripe ovaries. Lengths at maturity were calculated from the proportion of mature fish during breeding seasons. Natural mortality rates were determined from length frequency data from an unfished area of the lake. Values of the growth constant K ranged from 0.487 to 0.671. The ratio of length at maturity to asymptotic length varied from 0.56 to 0.82. Growth parameters are compared with those of other cichlids. Most species mature in their third year. Fecundity was proportional to the square of the length in four of the five species. The species studied appeared to produce only one batch of eggs per breeding season. Instantaneous natural mortality rates ranged from 0.92 to 1.69.
Renal excretion in channel catfish following injection of quinaldine sulphate or 3‐ trifluoromethyl‐4‐nitrophenol
Authors: Allen J. L. , Hunn J. B.
Published: January 2006

Channel catfish, Ictalurus punctatus Rafinesque, injected intraperitoneally with 2‐methyl‐quinoline sulphate (QdSO4) or 3‐trifluoromethyl‐4‐nitrophenol (TFM) eliminate most of the dose of these compounds by extra‐renal routes. Patterns of renal excretion of Na+, K+, Ca2+, Mg2+, and Cl− (ρEq kg−1 h−1) appeared to be associated with the ‘stress’ of the urine collection technique rather than with the elimination of either compound. Concentrations of Na+, K+, Ca2+, Mg2+, and Cl− (mEq/1) were determined in urine, plasma and gall bladder bile.
Studies on the ichthyo‐fauna in Plover Cove Reservoir, Hong Kong: I. Sequence of fish population changes
Authors: Man Hanson S. H. , Hodgkiss I. J.
Published: January 2006

Gill‐net surveys were made weekly from May 1971 to April 1974 in Plover Cove Reservoir, Hong Kong and the results analysed to determine the fish species composition in the reservoir, the seasonal fluctuation of catches and the length frequency distribution of some major species.

Over 20 species were represented in the fish fauna including almost all the naturally occurring species as well as the stocked species. Of the twenty species, some were collected regularly in gill‐net samples while others occurred rarely. Sarotherodon (Tilapia) mossam‐bicus (Peters) was the dominant species and contributed the main bulk of the catch. This species also showed distinct age groups in the reservoir and modal changes occurred seasonally. Thus, among the fish species studied only S. mossambicus showed a steady and progressive increase in abundance in the reservoir and the full development of this fish population with its wide range of feeding habits should be beneficial.
Mycobacteriosis in hatchery–confined chinook salmon (Oncorhynchus tshawytscua Walbaum) in Australia
Authors: Ashburner L. D.
Published: January 2006

An increasing incidence of fish mycobacteriosis was detected in Chinook salmon held in fresh water at the Snobs Creek Hatchery. This Mycobacterium sp. infection has been passed on to the Fl generation possibly through an ovarian pathway, either by the egg or more likely through infected ovarian fluid. There is no evidence that the diet was the source of infection.
Behavioural, haematological and histological studies on acute toxicity of bis(tri‐n‐butyltin oxide on Salmo gairdneri Richardson and Tilapia rendalli Boulenger
Authors: Chliamovitch Y.‐P. , Kuhn C.
Published: January 2006

In acute toxicity tests based on the loss of positive rheotaxis, the relationship between exposure time and bis (tri‐n‐butyltin) oxide concentration was determined for Salmo gairdneri and Tilapia rendalli. This relationship may be represented by two superimposed rectangular hyperbolas (X‐d) (Y‐b)=c corresponding to two poisoning mechanisms. The 24‐h EC50 is 30.8 μg/1 for trout and 53.2 μg/1 for T. rendalli. A histopathological study on S. gairdneri shows concentrations from 5.85 to 0.0117 mg TBTO/1 resulted in damage to the gill epithelium. At low concentrations a degeneration of the cornea and damage to the epithelial cells of bile ducts were also observed. Prior to a loss of positive rheotaxis and with concentrations from 0.023 to 1.17mg/l, the packed cell volume, the haemoglobin concentration and erythrocyte count increased. Determination of the mean cell volume showed swelling took place at 1.17 mg/1 but shrinkage was observed at 0.053 mg/1. These results indicate that TBTO interfered with the process of respiration. A ‘safe level’ (0.1 μg/1) is proposed for schistosomiasis control.
Studies on the ichthyo‐fauna in Plover Cove Reservoir, Hong Kong: feeding and food relations
Authors: Man Hanson S. H. , Hodgkiss I. J.
Published: January 2006

The feeding biology of the fish species in Plover Cove Reservoir, Hong Kong has been investigated with special reference to Sarotherodon mossambicus (Peters). The food spectra of various fish species were analysed and compared and the results indicated that S. mossambicus played an important role in the ecology of this reservoir since all major food sources were exploited.
Gyrometra kunduchi n.sp., a cestodarian from Plectorhinchus pictus (Thunberg, 1792) from the Indian Ocean
Authors: Khalil L. F.
Published: January 2006

Gyrometra kunduchi n.sp. from the body cavity of Plectorhinchus pictus from the Indian Ocean, off the coast of Tanzania is described and figured. The new species is differentiated from G. albotaenia, the only species of the genus, by the absence of an apical pit, the extent of testes and vitellaria and measurements of the various organs.
Effects of fish size and ration level on the growth and food conversion efficiency of rainbow trout, Salmo gairdneri Richardson
Authors: Wurtsbaugh Wayne A. , Davis Gerald E.
Published: January 2006

The growth rates of rainbow trout, Salmo gairdneri, which ranged in size from 0.6 to 5.2 g and were provided rations of three different sizes, were measured during a 15‐day study. The relative maintenance rations (food/gram of fish at zero growth rate) decreased with increases of fish size. Consequently when fish were kept at low ration levels the growth rates and gross efficiencies of food conversion of ‘large’ fish were greater than those of ‘small’ fish. However, as ration level increased, the effects of fish size grew at the same rates or slower than small fish. With increases of ration to the highest levels (9–12%/day) gross efficiency values for large fish began to decline while those for small fish continued to increase.
Observations on morphological and biochemical features of some cyprinid hybrids
Authors: Child A. R. , Solomon D. J.
Published: January 2006

Roach, rudd and bream and hybrids between roach x rudd and roach x bream have been examined morphologically and by electrophoretic separation of their serum proteins. Identification by both methods agree and it is suggested biochemical methods of identification may be of value in cases of difficulty when distinguishing hybrids by morphological methods.
Spawning characteristics of brown trout and sea trout Salmo trutta L. in Kirk Burn, River Tweed, Scotland
Authors: Campbell J. S.
Published: January 2006

The upstream spawning migrations of brown trout and sea trout were studied using stationary traps placed in Kirk Burn, a tributary of the upper Tweed. The sea trout spawning period extended from early November to the first week of December, while that of brown trout occurred from the middle of October to the third week of December. Sea trout were predominantly maiden spawners of ages 2.1+ and 3.1+ while brown trout were mostly age 2+ and 3+. Male‐female sex ratios approximated 1:1.4 in sea trout but 6 : 1 in brown trout. Brown trout males participated in the spawning activities of sea trout. Low water conditions in Kirk Burn hindered the upstream movement of spawning sea trout, while sudden increases in water level appeared to stimulate the upstream migration of both brown trout and sea trout. The suggestion is advanced that the freshwater resident brown trout of the Tweed which migrate upstream into the smaller tributaries to spawn is wholly, or at least partially, the progeny of anadromous parents.
Intensive culture of grass carp, Ctenopharyngodon idella, in circular tanks
Authors: Shireman J. V. , Colle D. E. , Rottmann R. W.
Published: January 2006

Fingerling grass carp (Ctenopharyngodon idella) were cultured in 380 1 circular fiberglass tanks at stocking densities of 0.53, 1.06, 1.59 and 2.11 fish/1. Fish were fed duckweed (Lemna minima) to satiation. Fish grew from 2.7 g to a maximum mean weight of 72.7 g in 88 days. Fish stocked at 0.53 fish/1 grow more rapidly than those stocked at higher densities. Mean daily consumption rates were strongly correlated with oxygen levels and when oxygen levels dropped below 4 mg/1 consumption was reduced approximately 40%. High biomass, growth, and survival rates obtained during this study indicate grass carp are well suited for intensive tank culture.
Approaches to the analysis of energetic costs of intraspecific competition for space by rainbow trout (Salmo gairdneri)
Authors: Li Hiram W. , Brocksen Robert W.
Published: January 2006

Two approaches of estimating energy expended by rainbow trout (Salmo gairdneri) on density‐dependent activities were tested. Metabolic rates were obtained from growth experiments in laboratory systems. Increases in metabolic rates at higher population densities were attributed to three factors: (1) starvation, (2) increased levels of exercise by subdominant fish were forced to maintain stations in fast water due to saturation of territories of more dominant trout, (3) higher planes of excitation. It was observed that variance of energetic factors of routine metabolism, growth rate, consumption rate, and growth efficiency tended to increase with density. These responses seem to be a good indication of intraspecific competition. Little correlation was observed between density and average daily ration, or density and aggressive behaviour.

Dominant trout, as a group grew faster, grew more efficiently, and contained greater lipid content than the rest of the population at each density. However, strictly defined, energetic advantages were not conferred on a ‘peck‐right’ basis. At higher densities, dominance conferred less benefits than was observed at lower population levels. Space limitation per se was not an influential factor affecting growth rates. Methods used to estimate density‐dependent energy costs are evaluated. Both methods give nearly identical estimates.
Epidermal lesions and fungal infection on the perch, Perca fluviatilis L., in Windermere
Authors: Pickering Alan D. , Willoughby L. G.
Published: January 2006

An account is given of the histological changes associated with epidermal lesions on the Windermere perch, Perca fluviatilis L., between the months of January and March, 1976. During the later stages of the development of the lesions an apparent succession of fungal colonization was observed. A total of five genera of fungi were identified with Leptomitus lacteus appearing early in the infection and Achlya tending to dominate the more advanced lesions. The initial cause of the lesions has not been identified but the possibility of Argulus damage is discussed.
Effect of photoperiod on the incorporation of 3H‐thymidine into the gonads of Carassius auratus
Authors: Yadav M. , Ooi S. Diana
Published: January 2006

Gldfish, Carassius auratus of varying sizes were conditioned in continuous light or darkness f or 10, 20 and 30 days and the incorporation of 3H‐thymidine into the gonads was investigated to attempt to develop a bioassay for fish gonadotropins.

The 24‐hour gonadal 3H‐thymidine of 10‐day conditioned fish was significantly less at the dose level of 0.5 μCi 3H‐thymidine/fish compared to 1.0, 2.0 and 3.0 μCi/fish which gave gonadal activities not significantly different from each other. Thus, for all subsequent work the dose of 1.0 μCi/fish was used.

Photoperiod of continuous light or darkness had little effect on fish weighing less than 11 g but in fish 11‐15 g conditioned for 20 days in darkness and fish greater than 16 g conditioned for 10 days in darkness, depression in gonadal 3H‐thymidine incorporation occurred. In fish 11‐15 g, prolonged conditioning for 30 days in darkness induced more gonadal activity than was observed at 20 days.

The effect of injection of Channa striatus pituitary extract at doses of 1 mg/10 g body weight and 5 mg/10 g body weight induced a significant increase in 3H‐thymidine incorporation in the gonads over saline injected controls. The results suggest the potential of using photoperiod as a means of inducing regression of gonads of suitable fish in a bioassay of gonadotropins.
Adaptation of the dark muscle of cod to swimming activity
Authors: Love R. Malcolm , Munro Lesley J. , Robertson Ian
Published: January 2006

After cod (Gadus morhua L.) had been exercised in a channel, the intensity of pigmentation of the dark muscle was shown to be greater than in unexercised controls. A well‐marked seasonal cycle in pigmentation occurs in cod caught near Aberdeen with a summer maximum suggesting maximal feeding activity. The possibility of using the observation to identify stocks of fish is considered.
Aspects of the reproductive biology of Hippopotamyms pictus from Lake Kainji, with notes on four other mormyrid species
Authors: Blake B. F.
Published: January 2006

A method is described for the assessment of fecundity in mormyrid fish. In all species examined a tri‐modal egg size distribution was found in the mature pre‐spawning ovary. These modes represented one oocyte and two ova components. The significance of the presence of two sizes of ovum is discussed in relation to breeding periodicity in Hippopotamyrus pictus. Size and age at first maturity are estimated for this species. The probable effects of the formation of the lake on the breeding behaviour of mormyrids is discussed.
Relationships between food and cellulase activity in freshwater fishes
Authors: Prejs Andrzej , Blaszczyk Mieczyslaw
Published: January 2006

The food and cellulase activity of five cyprinid and one salmonid species were examined. All Cyprinidae species showed cellulase activity. No activity was found in pelagic Coregonus albula (Salmonidae). Cellulase activity showed a positive correlation with the amount of highly processed plant detritus in the gut. No correlation was found between the activity level and the amount of fresh fragments of macrophytes and filamentous algae.
NADP‐isocitrate dehydrogenase polymorphism in the Atlantic salmon Salmo salar
Authors: Cross T. F. , Payne R. H.
Published: January 2006

Electrophoretic variation of Atlantic salmon NADP‐isocitrate dehydrogenase in liver extracts of material from Ireland is interpreted in terms of two loci, IDH‐A and IDH‐B, coding for cytoplasmically‐located isozymes. The IDH‐A locus is polymorphic with qIDH‐A1=0.18 and qIDH‐A2=0.82. This polymorphism is of potential value for investigating the population genetics of the two races of Atlantic salmon in Ireland. An additional, monomorphic band which appears in heart extracts may be a mitochondrial enzyme coded by a third locus.
Acute Toxicity of water‐borne dimethylnitrosamine (DMN) to Fundulus heteroclitus (L.)
Authors: Ferraro Linda A. , Wolke Richard E. , Yevich Paul P.
Published: January 2006

Acute (120h) toxicity of the water‐borne carcinogen, dimethylnitrosamine (DMN) to adult Fundulus heteroclitus (L.) at 20°C and 20.2%0 salinity in natural seawater was determined. The LC‐50 values were 8300 mg/1 at 24 h, 5500 mg/1 at 48 h, 4700 mg/1 at 72 h, 3300 mg/1 at 96 h and 2700 mg/1 at 120 h.

Gross lesions consisted of peritoneal and cephalic ecchymoses. Microscopic lesions included necrosis and sloughing of the gastrointestinal mucosa, haemorrhage and necrosis of the liver, and necrosis of taste buds, with severity and incidence being a function of DMN concentration. Acute pathological effects of DMN on Fundulus heteroclitus conformed closely to those reported in other species exposed to this compound by respiratory, oral or parenteral route. DMN concentrations used in this experiment greatly exceeded those expected to be found under natural conditions, and this report is intended both to improve our understanding of DMN‐induced pathology in marine fishes and to provide further evidence of the consistency of acute lesions induced by DMN, regardless of test organism or mode of exposure.
Some aspects of the biology of Petenia krausii Steindachner (Pisces: Cichlidae) in Lake Valencia, Venezuela
Authors: Infante O. , LaBar G. W.
Published: January 2006

Petenia kraussii Steindachner (Pisces: Cichlidae) was collected from Lake Valencia, Venezuela from April 1973 to April 1974. A total of 457 specimens were examined for stomach contents, and 471 were analyzed for length‐weight relationship, sexual condition including fecundity and parasitism. P. kraussii is primarily a plankton feeder when small and utilizes benthic invertebrates after attaining about 10 cm standard length. The larvae of a benthic ephemeropteran, Campsurus sp. (Hexigenidae) was the most important single food item with gastropods and fish eggs also being found consistently in stomachs. No mature male fish were found, and only 17 of 471 fish could be identified as males, while 157 were females. Gravid females contained an estimated mean of 6266 eggs and matured at about 18 cm standard length and 100 g live weight. It was not possible to determine age from either scale or otoliths.