bluuebunny/crossref_metadata_2025 huggingface dataset:
Infestation of the jack mackerel, Trachurus declivis (Jenyns), with the cymothoid isopod, Ceratothoa imbricatus (Fabricus), in south eastern Australian waters
Authors: Maxwell J. Garrey H.
Published: January 2006

The tongue biter, Ceratothoa imbricatus, a cymothoid isopod, commonly found on a number of Australian inshore temperate fish species, was recorded in the pelagic jack mackerel, Trachurus declivis, in 26 of 43 trawls. The infestation rate was low (1·76%) in the 26 trawls where the association was noted. It is suggested that infestation occurs at an early age and that subsequent growth by the isopod is mediated by the host. Estimates of the growth parameters indicate that the isopods are long lived, and can remain for at least nine years on the host fish. Protandrous hermaphroditism, common in the Cymothoidae, is found in C. imbricatus with females attaining a large size in the bucco‐pharyngeal cavity while the male, with suppressed growth, is restricted to the branchial arches.

Although cymothoid isopods are commonly described as parasites, observable damage on the jack mackerel was restricted to the tissues at the points of attachment of the isopods. The effect of the isopod on the jack mackerel may not be as debilitating as might be expected and it is argued that the relationship may best be described as commensalism.
Physiological observations on developing rainbow trout, Salmo gairdneri (Richardson), exposed to low pH and varied calcium ion concentrations
Authors: Nelson J. A.
Published: January 2006

The extinction of piscine populations in waters acidified by atmospheric fallout of pollutants and runoff from coal strip mines usually occurs through recruitment failure. To determine mechanisms of recruitment failure, several physiological parameters of developing rainbow trout were monitored while fish were exposed to conditions of low pH and varied calcium ion concentrations. Cardiac rate, ossification, growth, tissue calcium concentrations, protein maturation, hatching, and mortality were examined. Results indicate a decreased cardiac rate, decreased rate of ossification, slower growth, less pigmentation, delayed hatching and increased mortality under conditions of low pH. Cardiac rate, hatching and mortality varied with the external calcium concentration.
Reproductive biology of Gambusia affinis holbrooki Baird and Girard, Xiphophorus helleri (Gunther) and X. maculatus (Heckel) (Pisces; Poeciliidae) in Queensland, Australia
Authors: Milton D. A. , Arthington A. H.
Published: January 2006

The reproductive biology of three introduced Poeciliidae, Gambusia affinis holbrooki Baird and Girard, Xiphophorus helleri (Günther) and X. maculatus (Heckel) was studied over a 14‐month period in Brisbane, Queensland. Photoperiod and water temperature determined the length of the breeding season in G. affinis, which produced up to nine broods between August and March, with the peak of reproductive activity in October. Fecundity was linearly related to body weight in G. affinis (mean fecundity = 22.78 ± 1.02, range = 3–108 offspring per brood).

Xiphophorus helleri bred from August to May, producing eight to nine broods, with peak reproductive activity from October to December. Fecundity was curvilinearly related to body weight (mean fecundity = 60.15 ± 3.8, range = 7–183 offspring per brood. Xiphophorus maculatus bred between September and March, producing five to six broods during the study period. Fecundity was linearly related to standard length (s.l.) (mean fecundity = 27.27 ± 2.4, range = 3–92 offspring per brood). Although the reproductive strategy of the three species differs, all have the capacity to build up large populations in south‐eastern Queensland. Their present distributions and relative abundance are discussed.
The critical swimming speed of the sand smelt (Atherina presbyter Cuvier) in relation to capture at a power station cooling water intake
Authors: Turnpenny A. W. H. , Bamber R. N.
Published: January 2006

Critical swimming speeds (CSS) of sand smelt, Atherina presbyter, were measured in a laboratory flume. Individuals of all age classes (0+ to III +) found in the vicinity of Fawley power station, Hampshire, were tested at temperatures covering the seasonal range. The median CSS was 2.7 body lengths per second (bl s−1) at 5.8 °C, rising to 5.7 bl s−1 at 18.5°C.

A two‐variable (water temperature and body length) regression model was fitted to the data, and this was used to assess escape potential of fish coming into contact with the power station cooling water intake currents and the extent of possible bias in fish length data collected from this source. It is concluded that the sand smelt remains vulnerable to entrainment at the power station over its whole length range and over the full range of seasonal temperatures and that size‐dependent swimming performance will not lead to significant bias in sample length distributions.
The effect of starvation and subsequent feeding on the hepatocytes ofChanos chanos(Forsskal) fingerlings and fry
Authors: Storch V. , Juario J. V.
Published: January 2006

Excised liver sections of the milkfish,Chanos chanos, fry and fingerlings were studied by transmission electron microscopy. The hepatocytes underwent marked ultrastructural alterations in response to food deprivation of 10‐day starvation for fry and 2 months for the fingerlings. The prominent features characterizing the hepatocytes of starved fish were: a reduction of cell and nucleus size; apparent loss of nucleoli; condensation of chromatin material in fry; loss of stored glycogen; reduction of ER profiles; increase in the number of electron‐dense bodies containing large amounts of iron in fingerlings; and an increase in mitochondrial size. These changes were reversible following short periods of re‐feeding, i.e. 2 days for fry and 4 days for fingerlings, using natural food for the fry and formulated diet for the fingerlings.
Uptake and loss of nitrite from the blood of rainbow trout, Salmo gairdneri Richardson, and Atlantic salmon, Salmo salar L. in fresh water and in dilute sea water
Authors: Eddy F. B. , Kunzlik P. A. , Bath R. N.
Published: January 2006

The acute toxicity of nitrite (NO−2) to salmonids is strongly ameliorated by chloride (Cl−) ions rendering it almost harmless in most fresh waters apart from those with low Cl− content. In Cl− poor fresh water external NO−2 is concentrated in the blood plasma until it is at approximately the same molar concentration as haemoglobin (about 8 mmol) and at this point most of the haemoglobin has been oxidized to methaemoglobin this being a contributory cause of death.

Two theories are advanced to account for NO−2 concentration in the blood. The first supposes that gills are impermeable to NO−2 but allow its conjugate acid nitrous acid (HNO2) to diffuse into the blood where it dissociates according to the blood pH value. Thus NO−2 will accumulate in the blood plasma if it has a higher pH value than the water. The second supposes that the Cl− uptake mechanism in the freshwater gill has an affinity for NO−2 and accounts for the fact that NO−2 entry to the blood is suppressed when external Cl− is present in significant amounts.

The results also suggest that NO−2 and Cl− behave similarly as diffusing ions. Thus NO−2 diffusion into the blood of seawater fish and from the blood of NO−2 loaded freshwater fish occurs at approximately the same rate as the corresponding Cl− fluxes. Nitrite loss from seawater fish is thought to be mainly by diffusion although there is some evidence for the active Cl− extrusion mechanism having a weak affinity for nitrite.
Increased prevalence of larval Eustronglylides (Nematoda) in the mummichog, Fundulus heteroclitus (L.), from the discharge canal of a power plant in the Chesapeake Bay
Authors: Hirshfield M. F. , Morin R. P. , Hepner D. J.
Published: January 2006

The prevalence of larval Eustrongylides sp. in the mummichog, Fundulus heteroclitus, was compared for two populations, one in the vicinity of the intake and one in the discharge canal of a power plant at Chalk Point on the Patuxent River, Maryland. The parasite was four times as prevalent in female F. heteroclitus collected from the discharge canal as in those collected from the intake area. Almost all infected fish were 70 mm or greater in total length. The larvae occurred in capsules and free in the mesentery, or associated with the gut, liver, or gonad of the host; multiple infections were common. Infection by Eustrongylides resulted in pronounced negative effects on F. heteroclitus. The dry weight of somatic tissue was reduced 5% and ovary dry weight was reduced 50% in infected individuals, compared to uninfected individuals of the same length. The proportion of infected females carrying ripe eggs during the breeding season was less than half the value for uninfected females. It is hypothesized that the greater prevalence of the parasite in the discharge canal results from increased abundances of oligochaetes (suspected first intermediate hosts of the parasite), presumably as a consequence of elevated temperatures and organic enrichment from the power plant.
Haematocrit values in feral goldfish, Camssius auratus L., as indicators of the health of the population
Authors: Munkittrick K. R. , Leatherland J. F.
Published: January 2006

Haematocrits were measured in goldfish, Carassius auratus L., collected in early spring and late summer from two locations in southern Ontario, Canada. At one location (Hamilton Harbour) the goldfish population suffered an epizootic of haemorrhagic lesions resulting in chronic anaemia, and at the second location (Cambridge) the goldfish population was disease‐free; haematocrits of the feral fish were compared with values obtained from a commercial breeding stock (CBS), and with published haematocrit values for cyprinid fish. Haematocrits in males were larger than in females in all collections of feral fish except spring‐caught (7–15°C ambient temperature) fish from Cambridge; no sex differences were evident in the immature CBS fish. Haematocrits were higher in feral female goldfish collected from higher ambient temperatures (15–25°C) than in comparable fish collected from lower ambient temperatures (4–15°C) at both collection sites, and also in males collected from Cambridge. Conversely, the haematocrit in the CBS fish was significantly decreased in fish transferred from 12 to 21°C. Haematocrits of the healthy (Cambridge) population were significantly larger than in comparable fish from Hamilton Harbour.
Immune hypersensitivity in the channel catfish, Ictalurus punctatus (Rafinesque)
Authors: Pauley G. B. , Heartwell C. M.
Published: January 2006

Channel catfish, Ictalurus punctatus, exhibited passive cutaneous anaphylaxis (PCA) when sensitized with Flexibacter columnaris antiserum produced in channel catfish (the first record of PCA in any fish), but not when sensitized with homologous antiserum against channel catfish virus. Channel catfish did not give delayed skin hypersensitivity responses after immunization with either channel catfish virus or F. columnaris.
A radiographic method for feeding studies on fish using metallic iron powder as a marker
Authors: Talbot C. , Higgins P. J.
Published: January 2006

A novel method for studying trophic dynamics of fish is described which involves X‐raying animals which have been fed a diet labelled with metallic iron powder. Results of feeding studies on juvenile Atlantic salmon, Salmo salar L., are presented which demonstrate that food consumption and gastric evacuation rates can be measured without incurring the major disadvantages offeree feeding, starvation or autopsy which are associated with most of the established methods.
Age determination and growth rate of eels, Anguilla anguilla (L)
Authors: Moriarty Christopher
Published: January 2006

Measurements taken from a series of photographs of otoliths of 37 eels caught in a stretch of river of 150m length were used to prepare a growth curve based on back‐calculated measurements. Values of L∞= 1045 and K = 0.046 were determined. Mean incremental growth calculated as 33 mm per year agreed closely with increments determined from growth observed up to 4 years after tagging eels from the same location. Inconsistencies in results of age determinations based on burned otoliths are described but it is concluded that the technique yields results of sufficient reliability to be used in practical management situations.
Blood osmolality shift in juvenile red drum, Sciaenops ocellatus L. exposed to fresh water
Authors: Crocker P. A. , Arnold C. R. , DeBoer J. A. , Holt G. J.
Published: January 2006

Juvenile red drum, Sciaenops ocellatus, measuring 40–49 mm s.l. tolerated abrupt transfer from 28%osalinity sea water to fresh water (< l%o). A significant shift in blood osmolality from a level of about 350 mosmol l−1 in sea water to a new level of about 311 mosmol l−1 was experienced by fish after 48 h in fresh water. The shift was followed by a slight reduction in blood osmolality to a sustained level of 300 mosmol l−1 after 96 h exposure to fresh water. The overall effect of increased environmental calcium on blood osmotic pressure of young red drum was not significant at the level tested.
Maturity, fecundity, and breeding seasons of the major catfishes (suborder: siluroidea) in Lake Victoria, East Africa
Authors: Rinne J. N. , Wanjala B.
Published: January 2006

Three of the five major species of catfishes in Lake Victoria displayed continuous, protracted (fractional) spawning activity with half or more of the population in gonadal stages IV–VI. Pulses in reproductive activity occurred in all species and were generally positioned between the established, rainy seasons for East Africa. Although highly variable, relative fecundity was positively correlated with body length and weight of fish in all species. All five species matured sexually between their first and third year of life.
An investigation of factors controlling food intake in Arctic charr, Salvelinus alpinus L.
Authors: Jobling M. , Wandsvik A.
Published: January 2006

Digestibility values were determined for diets of varying protein content fed to Arctic charr. The use of these values, in conjunction with food intake data made possible the study of the effects of various parameters on the control of food consumption. Dietary energy content may be more important than protein content in regulating consumption. The regulation of food intake may be partially mediated through factors influencing gastric emptying coupled with mechanisms monitoring dietary metabolizable energy.
Pelagic records of the lumpsucker, Cyclopterus lumpus L.
Authors: Blacker R. W.
Published: January 2006

Since the development of mid‐water trawls in the mid‐1960s, the lumpsucker, Cyclopterus lumpus, has been found to occur frequently in mid‐water. Records from cruises of English research vessels show that lumpsuckers occur pelagically from the southern North Sea to about 80°N off Spitsbergen, usually in the upper 50–60 m, and often over abyssal depths of the Norwegian Sea and the north‐east Atlantic.
A new species of the deep‐sea fish genus Paraliparis Collett (Liparididae) from the eastern North Atlantic, with notes on its ecology
Authors: Merrett N. R.
Published: January 2006

A new species of liparidid, Paraliparis hystrix, is described from the slope waters (255–1140 m) to the west of Britain, in the area 49–59°N and 07–18°W. This pallid species is not uncommon, and is represented by a strong imbalance of females. Specimens close to ovulation have been collected in all seasons and have an estimated mean fecundity of 83 eggs.
The use of opercular muscle electromyograms as an indicator of the metabolic costs of fish activity in rainbow trout, Salmo gairdneri Richardson, as determined by radiotelemetry
Authors: Rogers S. C. , Weatherley A. H.
Published: January 2006

Averages of electromyogram (EMG) signals emanating from the levator arcus palatini, a small muscle involved in the operation of the operculum in rainbow trout, Salmo gairdneri, were analysed in terms of their relationship to the fish's oxygen consumption rates under various activity levels. The EMG signals were detected and transmitted with a radio‐telemetry system. The EMG values showed a good correlation with corresponding oxygen consumption rates for fish under forced‐swimming conditions but not when the fish was swimming spontaneously; this is attributed to an ability to regulate oxygen uptake at the gill surfaces by other means than increasing the ventilation volume, including alterations in the gill blood flow dynamics (e.g. secondary lamellar recruitment), and changes in the cardiac output. Under forced‐swim conditions, where the oxygen demands by the respiring muscles were higher, increased ventilation volume, as indicated by increased opercular muscle activity, was directly related to swimming speed and oxygen uptake.
Towards an explanation of specific dynamic action (SDA)
Authors: Jobling M.
Published: January 2006

Of the hypotheses proposed to explain specific dynamic action (SDA), it is suggested that the ‘protein synthesis/growth’ theory offers the best basis for further research. In the light of this, the relationships between rates of protein synthesis and metabolic rates are examined. Both of which are depressed with increasing periods of starvation and there appears to be a link between rates of protein synthesis and thyroid activity. SDA may represent a short‐term increase in rates of protein synthesis and turnover following feeding and the process is possibly regulated via plasma levels of thyroid hormones.
Salinity tolerance of the mosquito fish, Gambusia affinis (Baird and Girard)
Authors: Chervinski J.
Published: January 2006

Experiments were conducted to determine the adaptability of mosquito fish to various salt concentrations. Mosquito fish, Gambusia affinis, (total length (T.L.) 27–37 mm) were subjected to abrupt and gradual changes from fresh water to various salinities (S). Low mortality (10%) occurred when the fish were transferred from fresh water (S = 0·5‰) to 50% sea water (S = 19·5‰ Through gradual adaptation 65·0% of the fish were able to tolerate 100% sea water for 7 days. After a 7 ‐day stay in sea water, fish were readapted to fresh water during a 3‐h period. The results indicate that they were well able to tolerate the abrupt change. Through a gradual adaptation fish were also able to tolerate salinities ranging from 39·0‰ (100% sea water) to 58·8‰
A method for obtaining mitotic figures from blood leucocyte cultures of rainbow trout, Salmo gairdneri
Authors: Hartley S. E. , Horne M. T.
Published: January 2006

A method for obtaining dividing cells for chromosome analysis from blood cultures of the rainbow trout, Salmo gairdneri, is described. The effects of different phytohaemagglutinin and foetal calf serum concentrations, oxygenation of the cultures, and varying the initial volume of cell inoculum on the number of mitoses obtained are described and discussed.
An assessment of the angling fishery for yellowfin bream, Acanthopagrus australis (Günther), in Moreton Bay, Australia
Authors: Pollock B. R. , Williams M. J.
Published: January 2006

Yellowfin bream, Acanthopagrus australis, support an important angling fishery in Moreton Bay, a large estuarine system on the east coast of Australia. An analysis of the records of catches by anglers indicates that abundance and mean size of yellowfin bream have changed little in Moreton Bay during the period 1945 to 1980. Over the past 5 years substantial increases have occurred in the total angling effort for yellowfin bream at surf bar spawning areas in Moreton Bay. This has resulted in a decrease in mean catch per unit effort but no apparent decrease in total yield. Reclamation and development projects which cause degradation of the surf bar spawning areas have the greatest potential to cause reduction in abundance of yellowfin bream in Moreton Bay.
The pattern of distribution of dimethylbenz(a)anthracene in the Amazon molly, Poecilia formosa (Girard), after intraperitoneal injection*
Authors: Woodhead A. D. , Bornbusch A.
Published: January 2006

The present paper describes the distribution and accumulation of labelled dimethylbenz (a)anthracene (DMBA) in the Amazon molly after intraperitoneal injection. The study was made to see whether there was preferential accumulation of the compound in the spieen; the Undings showed that this was not the case. Two hours after injection, DMBA was present throughout the body, except in the brain and the ovary. There was enhanced deposition at four sites, in the macrophages of the atrium of the heart and the peritoneum, the liver and the exocrine pancreas. DMBA was taken up by reticuloendothelial macrophages for 78 h after injection, then it was lost. The accumulation and disappearance of radioactive labet seen in the liver and pancreatic cells probably represented the pattern of metabolism of the compound. By 400 h after injection there was little DMBA remaining. Label accumulated in the ameloblasts, which secrete the enamel capping of the teeth.
Lymphocyte culture for chromosome preparation
Authors: Blaxhall P. C
Published: January 2006

A technique is described using separated peripheral blood lymphocytes from fish which yields cultures giving good chromosome spreads suitable for convential karyotyping and the subsequent application of banding techniques.
Laboratory growth of larval lampreys (Lampetra (Entosphenus) tridentata Richardson) at different food concentrations and animal densities
Authors: Mallatt J.
Published: January 2006

Lampreys are important research animals. This study investigates some of the Parameters important for culturing the Suspension feeding larvae: food concentration, temperature and crowding. Large larvae (Lampetra (Entosphenus) tridentata Richardson) were used, weigh‐ing from l·5 to 3·0 g (wet). Two food types were employed: suspended yeast cells (Saccharo‐myces cerevisiae, 0–20 mg1 – (dry), or, in a few tests, a fine particulate fish food, Liquifry® (Interpet LTD, 0–13 mg l‐1). At both 14 and 4°C, yeast could sustain weight increases comparable to those in nature: >6% month‐1 for up to 6 months, the duration of the study. In a single lest, a vitamin Supplement failed to improve growth on yeast. Growth‐was fastest at 14°C (+41% month‐1, max. weight increase), although also substantial at 4°C (+11% month‐1, max). Growth could not be sustained at 20°C, due perhaps to difficulty in removing products of food decay from the aquaria. Food level being constant, growth rate varied inversely with animal density. It is suggested that larval lampreys release a growth‐inhibiting substance into the sand which they inhabit. Overall, the best growth was obtained at 14° C, with <0·05g of animal (wet weight) – aquarium water and average daily yeast concentrations between 4 and 13 mg –. Liquifry was associated with lowered growth rates when present continually above 4 mg (dry weight) – (14° C), although growth did occur at lower concentrations.
The food and feeding ecology of Gerreidae, Bleeker 1859, in the estuaries of Natal
Authors: Cyrus D. P. , Blaber S. J. M.
Published: January 2006

The food and feeding ecology of five species of Genes in the estuaries of Natal, were investigated from 1978 to 1980. The Kosi system, consisting of an estuary and three main lakes was selected as the main study area due to an abundance of Genes. Four other estuarine systems were sampled.

At Kosi polychaetes were important at the estuary, siphon tips (distal ±5 mm) of the bivalve Hiatula lunulata were most commonly taken in Lakes Makhawulani and Mpungwini, while chironomid larvae were important in Lake Nhlange. Ivlev's electivity test showed that Genes positively selected bivalve siphon tips when searching for food. The food taken by Genes from other estuaries was similar to that at Kosi, although the proportions of the different prey varied. At Kosi between three and five species occurred sympatri‐cally. Resource segregation was through differences in diet and feeding periodicity and a superabundance of food (H. lunulata siphon tips) during summer and autumn. During winter and spring when food may be limiting, most Genes leave shelf areas of the Kosi system, only G. acinaces remains in large numbers. Little is known of the diet of other fish which feed on benthic invertebrates in Kosi but there is probably little direct competition with Gerreidae, although Acanthopagrus berda and Pomadasys commersonni have been recorded feeding on the siphons of the bivalve Solen corneus, the former in Durban Bay and the latter at Kosi. In areas where the bivalve H. lunulata occurs it is suggested that Gerreidae have developed optimal foraging techniques which enhance resource partitioning.
Dual motor innervation in the axial musculature of fishes
Authors: Ono R. D.
Published: January 2006

A systematic survey of motor innervation in the myotomal muscle fibres in several groups of fishes was conducted to observe the extent of dual innervation, a phenomenon found within those myotomal muscle fibres with terminal innervation. It is concluded that the dually innervated myotomal muscle fibre is a primitive vertebrate feature. Furthermore, it is suggested that this particular form of polyneuronal innervation is retained in the course of neural evolution within the homogeneous white myotomal muscle fibre region in these fish groups in order to insure synchrony of firing during sudden, rapid locomotion. The findings are examined in light of current ideas regarding the direct adrenergic innervation in addition to cholinergic innervation of striated muscle fibres.
The effects of a settled industrial–domestic sewage works effluent from percolating filters on the survival and growth of various stages of rainbow trout, Salmo gairdneri (Richardson)
Authors: Fraser J. A. L. , Clark E. R.
Published: January 2006

Comparisons were made of the mortality, growth and condition factor over a 50‐day period of eleutheroembryos, alevins, 2‐month fry, 4‐month fry and 1 + rainbow trout, Salmo gairdneri, in water of three qualities–Birmingham tap‐water, 50% and 100% settled effluent from percolating filters (Minworth Effluent Treatment Works) when dissolved oxygen levels were maintained near 100% ASV.

There was no significant mortality among life stages in control tap‐water but the LT50 values of life stages in both 50% effluent and 100% effluent revealed significant differences. Inter‐treatment comparisons showed similar mortalities of eleutheroembryos, of 2‐month fry and of 1 + fish in the three treatments but LT50 values of 4‐month fry showed significant differences. Growth rates of 2‐month and 4‐month fry were suppressed in both effluents after 7 days and there was a significant deterioration in the K factor of these life stages after 14 days. Predicted toxicities (the sum of the proportions of the 48‐h LC50 of the individual poisons to rainbow trout) were compared with the observed toxicity in 50% and 100% effluent. The relevance of in vivo testing in comparison to predictive techniques is compared.
Effect of prey density and hunger state on capture of krill, Nyctiphanes australis Sars, by Australian salmon, Arripis trutta (Bloch & Schneider)
Authors: Morgan W. L. , Ritz D. A.
Published: January 2006

When hungry salmon were offered a simulated (unattainable) swarm of krill with high central density, the density of the region first attacked increased with increasing attack readiness (measured as snout contacts). When allowed to capture krill in a range of prey densities, hungry salmon captured krill most successfully (in terms of capture/contacts) in the lowest density and less efficiently with increasing densities. However, salmon still captured a greater number of krill in a given time in high compared to low densities. When salmon in three different hunger states were exposed to a simulated swarm of krill, those with the lowest hunger level most often attacked the lowest prey densities first. Salmon with a high hunger level most often attacked the highest prey density first. Those fish with a moderate hunger level chose an intermediate prey density. This behaviour can be interpreted as a hunger‐dependent feeding strategy. The ways in which swarming of the prey might influence capture by the predator are considered.
Effect of supersaturated water on fish in the River Nidelva, southern Norway
Authors: Heccbercet Tor G.
Published: January 2006

Fish mortalities in the River Nidelva, South Norway in 1978, were suspected to be caused by Gas Bubble Disease. In June 1980, the hydrological situation occumng in the Nidelva in 1978 was reconstructed, and the effects were analysed by keeping fish in cages. Examination of the dead fish showed that most were killed by Gas Bubble Disease. The results also showed that brown trout, Salmo trutta, was the least tolerant, and eel, Anguilla anguih, was the most tolerant to dissolved gas supersaturation. Only fish kept near the surface were killed while fish kept at 3 m depth were mildly affected due to hydrostatic pressure compensation. In contrast to the situation in 1978, few of the wild fish were killed during the experiment in 1980.
Differential habitat utilization by sexes of Sarotherodon mossambicus in Lake Valencia, Venezuela: significance for fitness
Authors: Bowen S. H.
Published: January 2006

Adult male and female Sarotherodon mossambicus in Lake Valencia, Venezuala select different littoral habitats. Males prefer areas with soft bottoms and high turbidity, while females favour areas with hard bottoms and low turbidity. Soft bottoms provide suitable sediment for male breeding site construction and high turbidity helps protect territorial males from visionally orientated predators, but the food available in this habitat is of poor quality and males feed relatively little. The hard bottom littoral provides food of superior quality and females feed in these areas. Condition factors are highest for subadult males, intermediate for adult females and lowest for adult males. Differential habitat utilization by sexes of S. mossambicus in Lake Valencia appears to contribute to individual fitness by providing males and females with specific requirements for reproduction.
Chitinase activity in the digestive tract of the cod, Gadus morhua (L.)
Authors: Danulat E. , Kausch H.
Published: January 2006

The study was made to determine if enzymatic degradation of chitin occurs in the digestive tract of the cod, Gadus morhua. The method employed corresponds to the end product measurement of Jeuniaux (1966), using ‘native’ chitin as the substrate. The following results were obtained.

Chitinolytic enzyme of high activity is present in enzyme solutions from the stomach contents, gastric mucosa and intestinal contents.

Lower chitinase activities are found in samples of the intestinal mucosa and the pyloric caeca.

The optimum pH ranges for the action of the enzymes in the stomach and the intestine differ: 4.5–5.1 and 5.1–6.5, respectively.

The role of chitin‐decomposing bacteria is discussed, based on bacterial numbers and pH conditions in the digestive tract. The existence of two different enzyme systems is indicated.
The status of flounders, Platichthys flesus L., as hosts of the Acanthocephalan Pomphorhynchus laevis (Müller) and its survival in marine conditions
Authors: Kennedy C. R.
Published: January 2006

The status of flounders as hosts of Pomphorhynchus laevis and its survival in both freshwater and marine habitats was studied in the wild and by means of laboratory investigations. Natural infections were found in flounders in the euryhaline regions of the River Avon but not in adjacent or distant regions of the English Channel. Pomphorhynchus laevis of freshwater origin survived and grew but did not become sexually mature in natural infections of flounders in the Avon or in flounders maintained in fresh water and sea water in the laboratory. The position of the parasite in the alimentary canal of its host changed in flounders but not in eels in response to the changing conditions within the flounder with increasing salinity. In the Baltic Sea P. laevis grew to a larger size, became sexually mature and occupied a different position, the rectum, in both flounders and plaice. It is suggested that marine and Baltic parasites constitute a different strain of P. laevis, one which completes its entire life cycle in the marine habitat and for which flounder is the preferred host. By contrast, flounders are not even a suitable host for the English freshwater strain of P. laevis although individual parasites may be carried to sea in this and other migratory fish and survive in this medium for varying periods. The sea appears to be a major barrier to dispersal of this freshwater strain, and this largely explains the restricted and discontinuous distribution of the parasite in Britain.
Osmotic changes during the development of eggs and larvae of the lumpsucker, Cydopterus lumpus L.
Authors: Kjörsvik E. , Davenport J. , Lönning S.
Published: January 2006

The demersal eggs of Cyclopterus appear to osmoregulate like the pelagic eggs of cod and plaice. Unfertilized eggs in ovarian fluid exhibited ovoplasm osmolarities similar to those of adult blood and ovarian fluid (356–359 mosmol kg−1). Yolk osmolarities remained virtually constant from fertilization and during development (356–366 mosmol), with a slight decrease near hatching (to 332 mosmol). Yolk and body fluids of larvae (338 mosmol) had osmoconcentrations similar to egg yolk values near hatching. Yolk osmoconcentration of unfertilized eggs remained unchanged during the first 12 h in sea water, with a slow increase thereafter. Fertilized eggs of bad quality cultures exhibited higher yolk osmoconcentrations than eggs of good quality. Cyclopterus eggs were found to develop normally and survive in 20–34%o salinity, larvae seemed to have the same salinity range.
Movements of brown trout, Salmo trutta L., in the River Gwyddon, South Wales
Authors: Harcup M. F. , Williams R. , Ellis D. M.
Published: January 2006

Movements of native brown trout, Salmo trutta, 1 + and older, were limited with up to 93% of recaptured marked fish occupying sites where previously caught. Movements > 50 m were rare with the majority < 15 m. Between sampling occasions, the population could be separated into a static component and a smaller mobile component but there was no evidence of a permanently mobile group. The proportion of mobile native fish increased after stocking with hatchery‐reared trout. Displaced native trout (1 + and older) showed the ability to home from 75 m upstream to 111 m downstream of a release site.
An electron microscopical study on the genesis of lipofuscin, melanin and haemosiderin in the haemopoietic tissues of fish
Authors: Agius C. , Agbede S. A.
Published: January 2006

The mode of origin of the pigments within the macrophages of the haemopoietic tissues of some fish species was studied with the electron microscope. Lipofuscin appears to be derived from damaged cellular components, such as effete mitochondria, through the peroxidation of their unsaturated lipids. Haemosiderin is almost certainly derived from the breakdown of haemoglobin from effete erythrocytes. Melanin appears to be derived from phagocytosis of melanin granules or their precursor organelles from melanin‐containing cells. Both lipid peroxidation and haemoglobin breakdown produce free radicals and cations which are potentially toxic. Melanin absorbs free radicals and has strong affinity for cations and it is probable that they are neutralized by the melanin in macrophages. The electron micrographs published here illustrate the association of the lysosomal apparatus with pigment formation in fish melano‐macrophages. These findings appear valid for all the species examined and may apply to all fish. It has been suggested that fish melano‐macrophage centres represent primitive analogues of the germinal centres of higher animals. This study reveals that melanocyte‐like cells outnumber melano‐macrophages in the kidney of rainbow trout, Salmo gairdneri. Moreover, like melano‐macrophages, these cells increase markedly in number during starvation.
The hardening process of the egg chorion of the cod, Gadus morhua L., and lumpsucker, Cyclopterus lumpus L.
Authors: Lönning S. , Kjörsvik E. , Davenport J.
Published: January 2006

When transferred to sea water the chorion of cod and lumpsucker eggs harden, reaching a resistance of about 150 and 2000 g respectively. In sea water this hardening process is independent of fertilization. Studies of eggs kept in artificial sea water with various ionic compositions indicated, in the lumpsucker eggs, that a cortical reaction seems to be a prerequisite for the hardening process. Calcium is necessary for the reaction both in unfertilized and inseminated eggs, whereas hardening takes place in the absence of potassium, magnesium or sulphate. Addition of barium or strontium as a substitute for calcium only caused hardening in the presence of activating spermatozoa. Activating spermatozoa were also necessary for hardening of lumpsucker eggs kept in ovarian fluid, but such hardening only occurred if calcium and/or magnesium were added. The hardening of lumpsucker eggs was associated with profound changes in the thickness and surface appearance of the chorion.
Tetrahymena pyriformis as a protective antigen against Ichthyophthirius multifiliis infection: comparisons between isolates and ciliary preparations
Authors: Dickerson H. W. , Brown J. , Dawe D. L. , Gratzek J. B.
Published: January 2006

Channel catfish, Ictalurus punctatus, were immunized with cilia from three isolates of Tetrahymena pyriformis and challenged with Ichthyophthirius multifiliis using a reproducible quantitative procedure. Two different methods of deciliation were used in antigen preparation. Results indicate that T. pyriformis cilia elicit an immune response in channel catfish against I. multifiliis, and that the protective ability of the cilia varies between T. pyriformis strains.
The effect of water‐soluble aromatic hydrocarbons on some haematological parameters of rainbow trout, Salmo gairdneri Richardson, during acute exposure
Authors: Zbanyszek R. , Smith L. S.
Published: January 2006

Rainbow trout were exposed to a model mixture of water‐soluble aromatic hydrocarbons (AH) at concentrations of 0.3–15.2 ppm for periods of 1–72 h. None of the parameters monitored except RBC changed at 0.3 ppm AH, while all constituents, except blood glucose, changed at 7.2 ppm AH. At 15.2 ppm, all fish died within 1 h. Haematological changes included increased haematocrit, haemoglobin concentration, erythrocyte counts, and blood clotting (prothrombin) times. Plasma Cl− concentration decreased significantly. Changes resembled a stress response except for the increased clotting times, which typically decrease, and lack of increase in blood glucose.
Seasonal variation in blood components of reared Baltic salmon, Salmo salar L.
Authors: Härdig J. , Höglund L. B.
Published: January 2006

Ranges in the means of blood measurements from 121 Baltic salmon taken on nine occasions spread over an annual cycle were: packed cell volume or haematocrit; blood haemoglobin; red blood cell counts including immature erythrocytes; mean corpuscular haemoglobin concentration; mean cellular haemoglobin content and mean cellular volume. Seasonal changes appeared in all blood variables. Ontogenetic differences occurred in RBC and mean cellular volume when comparing 1 + parr with 2 + smolts in August one year apart, and in haemoglobin, RBC and immature RBC when comparing 1 + parr with adults once in November 1976. This points to greater influence upon haematological variation by season than by age. Significant regressions found within age groups, between pairs of mutually independent blood variables, are presented.
Blood cells of Fundulus heteroclitus (L.)
Authors: Hightower J. A. , McCumber L. J. , Welsh M. G. , Whatley D. S. , Hartvigsen R. E. , Sigel M. M.
Published: January 2006

Much of the parenchyma of the normal pronephros of the adult Fundulus heterodilus, a euryhaline teleost, is haematopoietic tissue which was examined in cytocentrifuge preparations and plastic embedded thick sections. As we have not characterized many of the blood cells functionally, the terminology used is based on their morphological resemblance to similarly named cells in higher vertebrates. Approximately 80% of the non‐erythroid elements observed in the pronephros are mature eosinophilic granulocytes (48%), immature eosinophilic granulocytes (25%), or cells likely to be their precursors [e.g. small blast cells (6%) and large blast cells (2%)]. Although there are macrophages in the pronephros that are capable of endocytotic activity, the mature and immature granulocytes are not. The granulocytes are non‐specific esterase positive, PAS positive, acid phosphatase negative, and are capable of being mobilized by a RES activating agent, Ecteinascidia turbinata.
Biochemical changes occurring during final maturation of eggs of some marine and freshwater teleosts
Authors: Craik J. C. A. , Harvey S. M.
Published: January 2006

Biochemical changes which occur during post‐vitellogenic meiotic maturation of oocytes were investigated by measuring the concentrations of various phosphorus‐containing fractions of the ovaries and mature eggs of four marine species with pelagic eggs, plaice, Pleuronecles platessa, cod, Gadus morhua, haddock, Melanogrammus aeglefinus, and whiting, Merlangius merlangus, and three freshwater species with demersal eggs, rainbow trout, Salmo gairdneri, pike, Esox lucius, and powan, Coregonus lavarelus. In the former group, protein phosphate was deposited at normal vertebrate levels in the ovaries during vitellogenesis but was exhausted during maturation, its decrease correlating with the uptake of water which rendered the mature egg buoyant in sea water. In plaice, phospholipid phosphate declined slightly during maturation, while inorganic phosphate increased by an amount slightly less than that which disappeared from the protein fraction. No such changes occurred on maturation in these three fractions in the freshwater species, in which little or no water uptake occurred. In plaice, the approximately five‐fold increase in the water content of the oocyte was accompanied by a corresponding five‐fold increase in the amount of potassium, the major inorganic cation of the oocyte. These pelagic eggs appear to be unique among the eggs of vertebrates in their high water content (c. 92%) and in the fact that the protein phosphate is almost entirely utilized before fertilization, while, in those freshwater fishes and other oviparous vertebrates that have been examined, the egg is of much lower water content (50–70%) and most of the protein phosphate, like the other major yolk constituents, is used during embryonic growth. This utilization at such an early stage in the life cycle constitutes an extreme example of heterochrony.
A study of the migration of larval Anisakis simplex (Nematoda: Ascaridida) in the Chilean hake, Merluccius gayi (Guichenot)
Authors: Cattan P. E. , Carvajal J.
Published: January 2006

Hake were collected during four trips to investigate a possible migration from viscera to somatic musculature of larval Anisakis simplex. On each trip 150 hake were examined and separated in five groups of 30 hake. One group consisted of fish gutted immediately after capture; two other groups were gutted 15 h after capture, one of which had been left at environmental temperature, and the other put in ice; the remaining two groups (exposed to the same treatment) were gutted 30 h after capture. All fish flesh was digested (HCl‐pepsin digest); all nematodes found in the digest and in the viscera were counted. There was no increase of larval nematodes in flesh at 15 and 30 h. Temperature did not affect the migration of larvae. A regression test did not show significant differences between groups. Finally, there was no correlation between number of larvae in viscera and in musculature.
Polyembryony in teleostean fishes: double monstrosities and triplets
Authors: Laale H. W.
Published: January 2006

The scientific literature pertaining to both naturally occurring and experimentally induced polyembryony in teleosts is surveyed for fish culturists and fisheries naturalists. The survey, covering more than 100 references, provides a chronological historical introduction (17‐20th centuries) and a discussion of the causes underlying axial duplication in bony fishes.
Acclimation of the interrenal tissue of the brown trout, Salmo trutta L., to chronic crowding stress
Authors: Pickering A. D. , Stewart A.
Published: January 2006

Brown trout kept under chronically crowded conditions grew more slowly over a 110 day period than did uncrowded fish given similar rations. Crowding resulted in a significant elevation of plasma cortisol for at least 25 days but by day 39 the cortisol levels in both crowded and uncrowded fish were similar. After 110 days, plasma cortisol levels in both groups were low (<2ng ml−1) and no significant differences in interrenal histology were detected. It is concluded that prolonged growth rate suppression as a result of crowding is not mediated by a chronic elevation of plasma corticosteroids. Under the conditions of the present study, water quality deterioration due to crowding was not sufficient to account for any of the changes in interrenal activity of the fish. These findings are discussed in relation to social interactions between saimonid fish maintained at unnaturally high stocking densities.
Peritoneal inflammatory cells in plaice, Pleuronectes platessa L.: effects of stress and endotoxin
Authors: MacArthur J. I. , Fletcher T. C. , Pirie B. J. S. , Davidson R. J. L. , Thomson A. W.
Published: January 2006

When plaice were injected intraperitoneally with either oyster glycogen or live Vibrio alginolyticus an acute cellular inflammatory response was observed. The duration of these responses, 7 and 15 days respectively, exceeded the time course of the mammalian cellular inflammatory reaction. Peak leucocyte numbers were found at 2–3 days and neutrophils, which were phagocytic, were more numerous than macrophages. Although the increase in macrophage numbers was less marked, these cells appeared more actively phagocytic than neutrophils. Cortisol injections and environmentally‐induced stress caused a significant reduction in the extent of inflammatory cell infiltrates, while endotoxin significantly enhanced the response.
Collection and preparation of the channel catfish, Ictalurus punctatus Rafinesque, olfactory organ for scanning electron microscopy
Authors: Tarpley R. J. , Lewis D. H. , Marks J. E. , Sis R. F.
Published: January 2006

Lamellae in the olfactory organ of the channel catfish, Ictalurus punctatus, Rafinesque, possess delicate cilia on surfaces of sensory and non‐sensory epithelia. A technique is presented for examining the olfactory cilia by scanning electron micrography.
Evidence for crypsis in coho salmon, Oncorhynchus kisutch (Walbaum), parr: substrate colour preference and achromatic reflectance
Authors: Donnelly W. A. , Dill L. M.
Published: January 2006

The crypsis hypothesis of salmonid parr coloration and behaviour is evaluated in light of the criteria for protective resemblance. A review of the literature indicates that salmonid parr coloration and behaviour correspond to a cryptic interpretation. Experiments on coho salmon, Oncorhynchus kisutch, parr substrate colour preference indicate that the behavioural correlate of appropriate background choice is satisfied. Absorption spectrophotometry of diapositives of fish and experimental substrates suggests that background matching is achieved through achromatic reflectance and absorption of wavelengths by the silvery sides and parr marks, respectively.
Morphological comparisons of diploid and triploid hybrid grass carp, Ctenopharyngodon idella♀×Hypophthalmichthys nobilis♂
Authors: Cassani J. R. , Caton W. E. , Clark B.
Published: January 2006

Morphological and karyological comparisons of 25–28 hybrid grass carp from each of 3 year‐classes (1979–1981) indicated that diploid fish resulted during 1979 (82.1%) and 1980 (76.0%) the others being triploid. All of the fish tested from the 1981 year‐class were triploid. Most triploid fish differed from diploid fish by having a faster growth rate, fewer scales in the lateral line and transverse series below the lateral line, a relatively longer gut, and fewer deformities.