Histopathology of leech, Austrobdella bilobata Ingram, infestation on the yellowfin bream, Acanthopagrus australis (Günther), in northern New South Wales

Abstract. The histopathology of leech, Austrobdella bilobata , infestation on the upper palate and pelvic fin of the yellowfin bream, Acanthopagrus australis (Günther), is described. The feeding site was often haemorrhagic and swelling surrounded the attachment site. Histological examination revealed massive cellular infiltration (predominantly lymphocyte and macrophage) in the submucosa beneath the feeding and attachment sites. The latter also had a complete erosion of the integument beneath the parasite. Localized proliferation of connective tissue fibres and zones of necrosis and oedema were present in some cases.     

Allozyme variation and stock structure in the black bream, Acanthopagrus butcheri (Munro) (Sparidae) in southern Australia: implications for fisheries management, aquaculture and taxonomic relationship with Acanthopagrus australis (Günther)

An investigation of allozyme variation at 32 loci in the black bream, Acanthopagrus butcheri (Munro), and the yellowfin bream, Acanthopagrus australis (Günther), revealed heterozygosities (H) equal to 0.035 and 0.065, respectively, and polymorphism (P_0.95) equal to 0.067 and 0.200, respectively. The genetic data confirm the very high level of genetic similarity previously found between the two species, but nevertheless also support their recognition as separate species. The finding of only limited allozyme differentiation at three polymorphic loci amongst six black bream samples from south-eastern Australia is consistent with the existence of a single panmictic population in this region. This would require that adult black bream have a greater capacity to survive in near-shore marine environments than previously realised and that dispersal between estuaries is more extensive than was shown by tagging studies. In contrast, significant differences were found at two loci between black bream from south-eastern Australia and a sample from south-western Australia. The degree of genetic divergence between stocks in south-eastern and south-western Australia suggests that only local brood stock should be used for aquaculture or re-stocking as a precaution until further investigations with DNA-based techniques are conducted. The genetic divergence detected supports separate management for populations in Western Australia and Victoria.     

Histopathology caused by Caligus epidemicus Hewitt (Copepoda: Caligidae) on captive Acanthopagrus australis (Günther) (Pisces: Sparidae)

Abstract. Highest densities of copepodids (≤5.3 cm ^-2), chalimus (≤8.5 cm ^-2) and redundant filaments (≤6.7 cm^-2) of Caligus epidemicus were found on the anterodorsal and anteroventral flanks, head and pectoral fins of Acanthopagrus australis (Günther). Copepodids eroded the epidermis and usually attached their frontal filament to the basement membrane on the inter-ray region of fins, as well as the fin rays or scales. Chalimus stages were associated with a healed epidermis and little tissue response. The most extensive tissue response was associated with the redundant frontal filament, and was characterized by infiltrating macrophages, multinucleated giant cells, and epidermal and fibroblast proliferation. No significant pathology could be attributed to either pre-adult or adult copepods.     

Influence of terminal rig configuration on the anatomical hooking location of line-caught yellowfin bream, Acanthopagrus australis

Abstract  Experiments were carried out to test the dependence of anatomical hooking location on terminal rig configuration, and identify strategies by which hook ingestion can be minimised to reduce post-release mortality of angled yellowfin bream, Acanthopagrus australis (Günther). Eighty-five anglers targeted yellowfin bream using different designs and sizes of circle and J hooks and recorded technical, environmental and biological data for each landed fish. Considerably fewer fish (16.6 and 8.5%, respectively) ingested hooks than those hooked in the mouth (82.1 and 88.6%), and a greater percentage of J hooks were ingested than circle hooks or a J hook modified with a 15-mm horizontal bar. Irrespective of hook type, the rate of ingestion also declined with increasing hook weight and decreasing fish size. In cage experiments, significantly more hooks baited with natural soft baits (e.g. intestines and cephalopods) were ingested than those baited with artificial baits, crustaceans or teleosts, while in the field fewer hooks were ingested using artificial bait (e.g. bread and pellets) than terrestrial animals, teleosts, crustaceans, teleost or terrestrial animal intestines, cephalopods or polychaetes. Similarly, rigs with floats, short traces or a sinker only on the hook, along with angling in environments with at least some current reduced ingestion. Based on this study, anglers targeting yellowfin bream should be encouraged to use circle or modified J hooks and, regardless of the hook design, the largest hook size possible attached to short traces or a sinker only and hard baits.     

Histopathological and ecological aspects of Henneguya and Myxobolus (Myxosporea) infections in Acanthopagrus australis (Günther) (Pisces: Sparidae) from Moreton Bay, Australia

Abstract. Sporulated plasmodia of Henneguya sp. infected the gill filaments, interhemibranch septum, gut and other microhabitats of Acanthopagrus australis in Moreton Bay, southern Queensland, whereas Myxobolus sp. infected only the gut. There was usually no inflammatory response, but some plasmodia in the gill filaments were associated with a granulomatous, predominantly lymphoid, response that was not determined by either parasite maturity, or sex and size of fish or season. There was a microhabitat shift in branchial Henneguya infection from predominantly gill filament in juvenile bream to gill septum in older fish. The highest prevalences of Henneguya were in the southern part of Moreton Bay, but trends in seasonal infection and prevalences in relation to size and sex of fish were similar in the western and southern parts of the bay. This suggested a widespread distribution of the putative annelid alternate host in Moreton Bay, with highest densities in the southern part. Myxobolus infection was most prevalent in young male fish at the winter spawning grounds on eastern surf bars.     

Digestibility studies in juveniles of the Mexican cichlid, Cichlasoma urophthalmus (Günther)

Abstract. A simple trial is described to determine the effects of brown fish meal, solvent extracted soybean meal, raw wheat meal, raw starch and dextrin on diet digestibility in juveniles of the Mexican cichlid, Cichlasoma urophthalmus (Gümher). The effects of possible anti-nutrients in the feedstuffs used were assessed with the purpose of designing practical diets. The results did not show any effect attributable to anti-nutrients, but showed that high dietary fibre levels reduced digestibility. The carbohydrates of soybean meal were poorly digested compared with the other sources utilized. These results suggest that the substitution of fish meal by soybean meat and other plant proteins could be increased to reduce costs of practical diets for this species.     

Temperature and salinity tolerances of yellowfin sea bream, Acanthopagrus latus, at different salinity and temperature levels

Abstract Yellowfin sea bream Acanthopagrus latus (Houttuyn) (0.98 ± 0.27 g) were examined for temperature and salinity tolerances at nine different environmental regimes (0.3, 15 and 33 ppt combined with 10, 25 and 32 °C), in which the fish were subjected to gradual and sudden changes in temperature and salinity respectively. The 50% CTMax (critical thermal maximum) and the UILT (upper incipient lethal temperature) were in the range of 34.8–38.2 °C and 32.8–36.4 °C respectively. The 50% CTMin (critical thermal minimum) and the LILT (lower incipient lethal temperature) were in the ranges of 4.9–9.4 °C and 7.1–17.6 °C respectively. The 50% CSMax (critical salinity maximum) and the UILS (upper incipient lethal salinity) were in the ranges of 54–69‰ and 9–44‰, respectively. The fish at lower temperature (10 °C) and salinity of 33‰ tolerated temperature as low as 6 °C when the temperature was decreased gradually. The fish at 33 and 15‰ and lower temperature (10 °C) tolerated salinity as high as 66–67‰, whereas those at freshwater salinity level (0.3‰) and 32 °C tolerated salinity to 50‰ when salinity was increased gradually. The relationships among UILT, LILT, 50% CTMax, 50% CTMin, UILS, 50% CSMax, salinity and temperature are given.     

Biochemical responses of matrinxãBrycon cephalus (Günther, 1869) after sustained swimming

Juvenile matrinxã, Brycon cephalus, were submitted to sustained swimming for 72 days at 1.0 body length s^?1. Exercised fish (EF) grew more than non‐EF and their feed conversion ratio (FCR) improved; haematological responses demonstrated a decrease in haemoglobin and mean cell haemoglobin contents and increase in the mean cell volume. In the plasma, sodium, ammonia and amino acid concentrations increased; plasma triglycerides decreased while free fatty acids increased. Liver glucose, free amino acids, ammonia, the rate protein per fish weight and total lipid content increased, while the glycogen per fish ratio declined. Glutamate dehydrogenase (GDH) activity increased while pyruvate kinase (PK) and lactate dehydrogenase (LDH) decreased. White muscle glucose, lactate, the glycogen per fish‐weight ratio and total lipid content exhibited a decrease in their values; ammonia, free amino acids and the protein per fish‐weight ratio increased. GDH and PK decreased their activities. In the red muscle glycogen store, the glycogen per fish‐weight ratio and glucose were reduced. Juvenile matrinxãs, under sustained swimming, were physiologically and biochemically adapted to exercise as indicated by improved blood flow, transport and oxygen uptake, FCR, amino acid and protein incorporation and growth. Continuous exercise is a good practice for B. cephalus cultivation.     

Mycotic dermatitis in a freshwater gizzard shad, the bony bream, Nematalosa erebi (Günther), in the River Murray, South Australia

Abstract. The lower Murray population of bony bream is subject to an annual epidemic of the oomycete Saprolegnia (principally S. parasitica ) and the bacterium Aeromonas hydrophila. The epidemic is species-specific; it mainly affects adults whose susceptibility may be increased by stress due to winter cold. Lesions occur on the mid-flank and are characterized by an external mycelium, epidermal erosion, scale loss, hypodermal and muscular oedema, haemorrhage, myofibril degeneration and by the presence of Saprolegnia hyphae at all stages of infection. Although A. hydrophila is common in advanced lesions there is no significant systemic bacterial infection. This appears to be a primary mycotic dermatitis and is noteworthy because Saprolegnia is best-known as a secondary pathogen.     

Histopathology of vitamin C deficiency in a cichlid, Cichlasoma urophthalmus (Günther)

Abstract. This paper describes the histopathological changes observed in the Mexican native cichlid Cichlasoma urophthalmus (Günther) when try with an initial weight of between 160 and 170 mg were fed with diets deficient in vitamin C for 90 days. The epidermis showed an extensive inflammatory response, with spongiosis and also degenerative changes in the basal cells. Muscle showed a range of pathological changes including inflammation, changes in the number and position of the nuclei, vacuolation and necrosis, granular degeneration, and fibre loss. Gills showed thickening of the primary lamellae, oedema, hyperplasia, telangiectasis and atrophy of the bony supporting structures. Ganglia and neurones of nervous tissue were abnormal with changes which ranged from slight inflammation to central chromatolysis. The hepalopanereas was also affected and focal necrosis of the hepatocytes was frequently observed. The pancreas showed major changes with shrinkage of the acinar cells and reduction of zymogen granule content. Fish fed diets containing 0 and 40 mg vitamin C kg^-1 of diet were infected with Mycobacterium sp. and miliary tuberculosis was found affecting kidney, spleen, choroid gland, stomach, heart and muscle. The association between fish tuberculosis and vitamin C deficiency is discussed.     

Acute toxicity of Trichlorfon (Dipterex) to fry of Cichlasoma urophthalmus Günther

Abstract. Fry of Cichlasoma urophthalmus Günther were exposed to various concentrations of the organophosphate pesticide Trichlorfon, ranging from 1·25 to 80 mg/l in laboratory conditions. Mortality reached 100% in the highest concentrations (60 and 80 mg/l) in the first 24h. The intermediate concentration (40 mg/l) resulted in 50% mortality after 24h, and no mortality was observed in lower levels of the pesticide. LC50 at 24, 48 and 72h were 26·5, 23·7 and 17·2 mg/l respectively.
Some of the surviving fish were transferred to clean fresh water for a post-treatment growth trial. All the fish grew well with no apparent adverse effects as judged by their growth indices after 8 weeks.     

A study on Flexibacter columnaris infection in loach, Misgurnus anguillicaudatus (Bleeker, Günther)

Abstract. Infectivity of Flexibator columnaris to loach, Misgurnus anguillicaudatus (Blecker, Günther), was studied with variation conditions and the presence of other bacteria in the water medium. Invasion of fish by the poathogen varied with different water conditions. The highest prevalence of infection was observed in an experimentally formulated water containing 0·03% NaCl 0·01% KCl, 0·002% CaCl₂2H₂O and 0·004% MgCI₂ 6H₂O. The percentage of infection in tap water was similar to that of the formulated water. The infeetion rate was low in the individual salt solutions, and no infection occurred in distilled water. Even in the formulated water, the pathogen failed to infect the fish when Citrobacter freundii, Aeromonas hydrophila or Pseudomonas fluorescens were present at densities 100 times that of F. columnaris. However, in such cases, the numbers of F. columnaris in the mucus of the fish body surface did not increase much throughout the experimental period. In contrast, F. columnaris suceessfully invaded the fish in the presence of either Streptococcus sp., Flavobacterium flavescens or Flavobacterium fuscum , even when the numbers of these bacteria were 1000 times that of F. columnaris. In this ease, F. columnaris gradually increased its numbers on the fish body surface.     

Phosphorus and calcium requirements in the diet of the American cichlid Cichlasoma urophthalmus (Günther)

An experiment was carried out with Cichlasoma urophthalmus (Günther) juveniles to determine the phosphorus requirement and its interaction with dietary calcium. Twelve isoenergetic and isoproteic diets were prepared using a basal artificial diet containing vitamin-free casein, dextrin, starch, corn oil, fish oil, vitamin mixture and a mineral mixture free of calcium and phosphorus. Calcium and phosphorus levels were determined in the casein. To the basal diets were added different concentrations of phosphorus as potassium monophosphate (0.5, 1.0, 1.5 and 2.5 g kg^–1) and calcium as calcium carbonate (0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0 and 4.0 g kg^–1). These concentrations resulted in varying Ca–P ratios (1:1, 1.33:1, 1.5:1, 1.6:1 and 2.0:1). Calcium and phosphorus concentrations in the water were 84 mg kg^–1 and 0.003 mg kg^–1, respectively. The diet with 0.5 g kg^–1 phosphorus resulted in deficiency signs such as reduced growth, high conversion ratio, high fat content and low bone mineralization. Increased levels of dietary calcium and phosphorus both gave improved growth and mineralization. Mineralization continued to increase with dietary phosphorus levels above that required for maximum growth. The optimum level of phosphorus in the diet was 1.5 g kg^–1, the optimum calcium level was 1.8 g kg^–1 and the optimum Ca–P ratio was 1.3. Carcass lipid levels were inversely related to dietary phosphorus.     

Effects of anaesthetics on the oxygen consumption rates of platyfish Xiphophorus maculatus (Günther)

This study was carried out to find out the effects of anaesthetics, 2-phenoxyethanol. quinaldine sulphate. MS-222 and metomidate. at various dosages, on the oxygen consumption rates of two size groups of platyfish. Xiphophorus maculatus (Günther) at three temperatures. The results show that the oxygen consumption by the platyfish of both size groups was temperature dependent, being higher at higher temperature, but not size dependent. The effects of anaesthetics on the oxygen consumption rates of platyfish were dosage dependent and temperature dependent, especially for 2-phenoxyethanol, the effect always being significantly greater at lower temperature. Small and large fish did not show much difference in their responses to anaesthetic treatments. However, with 2-phenoxyethanol, the effect on the large platyfish was always better than on the small ones at 20-25°C. At 220-440 ppm and at 20°C, 2-phenoxyethanol was more effective than the other anaesthetics in suppressing oxygen consumption by the platyfish.     

Effects of controlling temperature and light duration on seed production in tilapia, Oreochromis spilurus (Günther)

An experiment was conducted to compare the seed production of tilapia, Oreochromis spilurus (Günther), under ambient water temperature and photoperiod, and under controlled water temperature (29.0 ± 2.0 °C), and photoperiods of 13 and 14 h day^?1. Male and female breeders with average weights of 155.4 and 78.7 g, respectively, were stocked in nine 1.04 X 1.04 X 0.40 m (L X W X H) fibreglass tanks. Each tank was stocked with two males and six females. Seed collection was carried out biweekly for 300 days. The results showed that the seed kg^?1 female day^?1, seed m^?2day^?1, total seed production per tank and spawning rates of females were highest during the 14 h day^?1 photoperiod (112.4, 77.4, 24 724 and 42.1%, respectively), followed by ambient spawning conditions (104.0, 57.9, 18 356 and 36.6%, respectively), and lowest during the 13 h day^?1 photoperiod (49.5, 36.5, 12 021 and 25.7%, respectively). Under ambient spawning conditions, peak spawning occurred in May. Monthly seed production was affected by changes in temperature and light duration. In both controlled photoperiods, the peak of seed production was observed during the first month after stocking. In all treatments, spawning declined gradually after the peak, which can be attributed to exhaustion of the breeders. The findings of this study indicate that seed production of O. spilurus in Kuwait can be extended beyond the restricted spawning season of 6-7 months by maintaining water temperature at 29.0 ± 2.0 °C and photoperiod at 14 h day^?1.     

Using Efinol®L during transportation of marbled hatchetfish, Carnegiella strigata (Günther)

The objective of this experiment was to test the efficacy of a probiotic (Efinol^®L) during transportation of marbled hatchetfish, Carnegiella strigata . Wild specimens were captured from a small stream and transported for 24 h in plastic fish boxes with a probiotic (10 mg L⁻¹) and probiotic-free water. The boxes were sampled at 3, 12 and 24 h of transport. At the end of the experiment, the survival rate was close to 100% in both treatments. Dissolved oxygen diminished with time in both treatments, but the probiotic group had significantly higher levels. Conductivity, pH and ammonia increased significantly during the transport, demonstrating higher levels in the probiotic-free group. Fish from both treatments presented very high net Na⁺ and K⁺ effluxes after 3 h of transport. At 24 h, net K⁺ effluxes in fish of the probiotic treatment reached values close to zero and a significantly lower Na⁺ efflux was observed. Cortisol levels in both treatments at 3 and 12 h were significantly higher than that in control samples. Higher body cortisol levels were observed in the probiotic-free group than that in the probiotic group at 3 and 12 h. The results demonstrate that addition of a probiotic during fish transport improves water quality and leads to fish presenting a lower stress response intensity.     

Overwintering tilapia, Oreochromis spilurus (Günther), fingerlings using warm underground sea water

Abstract.
The study was conducted to develop guidelines for high-density overwintering of tilapia in tanks using warm underground sea water. Seawater-acclimated fish of 20 g were stocked in 36 tanks at 250, 500 and 750/m³. Water flow was regulated at 0.1 and 0.2 l/kg fish/min. Fish were fed at the rates of 0.75% and 1.0% of biomass per day.
After 135 culture days, the mean individual weight gain and specific growth rate decreased, whereas feed conversion increased significantly ( P <0.0001) with the increase in stocking density. The condition factor at 500 and 750 fish/m³ was significantly lower ( P <0.0005) than at 250 fish/m³. However, stocking density had no significant effect on the survival rate. Significantly better specific growth rate, condition factor and feed conversion were observed at a water flow rate of 0.2 l/kg fish/min than at 01 l/kg fish/min. Significantly higher mean individual weight gain, specific growth rate, and survival rate were observed at 1.0%/day than at the 0.75%/day feeding rate. The findings indicate that the optimum stocking density for overwintering tilapia in tanks using warm underground sea water is 750 fish/m³ with a water flow rate of 0.1 l/kg fish/min and a feeding rate of 0.75%/day.     

Sperm motility and seminal plasma characteristics in Barbus sharpeyi (Günther, 1874)

Spermatozoa concentration, ionic composition, osmolality, glucose and total protein contents of seminal plasma and sperm motility were determined in Barbus sharpeyi (Cyprinidae, Teleosotei). Spermatozoa concentration ranged from 9.77 to 20.20 × 10⁹ spermatozoa mL^?1. Osmolality (mOsmol kg^?1) and ionic contents (mM L^?1) of the seminal plasma were 274.5±9.0, 70.0±3.4 Na⁺, 28.8±0.9 K⁺, 101.7±3.1 Cl^?, 0.9±0.1 Mg²⁺ and 2.1±0.1 Ca²⁺ respectively. Total protein and glucose were 5.3±0.2 g L^?1 and 76.7±4.3 mM L^?1 respectively. Sperm motility was initiated in a hypo‐osmotic condition, composed of either an ionic (KCl or NaCl) or a non‐ionic (sucrose) activation medium. Duration of sperm motility was very short: <2 min after activation in distilled water. Percentage of motile spermatozoa was significantly higher in an activation medium containing NaCl compared with that of distilled water. An activating medium containing NaCl or KCl higher than 150 mM or sucrose higher than 275 mM totally inhibited the activation of sperm motility. Immediately after sperm activation, wave(s) propagated along the flagellum, but waves were restricted to the proximal part of the flagellum (close to the head) at 1 min post activation. Studied characteristics in the present study were compared with those of other cyprinids for understanding inter‐species differences.