Horizontal and vertical movement of Mekong giant catfish <Emphasis Type="Italic">Pangasianodon gigas</Emphasis> measured using acoustic telemetry in Mae Peum Reservoir,Thailand

Abstract:   The horizontal and vertical movements of eight immature hatchery-reared Mekong giant catfish Pangasianodon gigas were monitored using acoustic telemetry in Mae Peum Reservoir, Thailand between 2003 and 2004. The fish were monitored for between eight days and more than 9 months. All of the fish moved over the entire reservoir within approximately 40 days after release. Subsequently, the home range became small approximately 40 days after release. The fish preferred deep areas in the reservoir. The fish displayed diel horizontal and vertical movement patterns. The fish showed larger-scale horizontal movement during the daytime than at night. The fish repeatedly showed active vertical movement during the day, whilst there was little variation in swimming depth at night. Our results imply that the vertical movements of the fish were related to the environmental condition of the reservoir.     

Use of full-fat winged bean Psophocarpus tetragonolobus seed meal as a protein feedstuff in fish-meal free diets for African catfish Clarias gariepinus

Mature winged bean Psophocarpus tetragonolobus seeds were quick-cooked and the full-fat meal derived was used to completely replace menhaden fish meal as a dietary protein source for the African catfish Clarias gariepinus . Five dry practical diets (400 g crude protein kg⁻¹ and 17.5 kJ gross energy g⁻¹ dry diet) containing menhaden fish meal (diet 1) or winged bean meal with or without graded levels of supplemental L -methionine (diets 2, 3, 4 and 5; 0, 5, 10 and 15 g kg⁻¹, respectively) were fed to catfish fingerlings (5.8  +  1.2 g) for 70 days. Weight gain, growth rate, feed conversion and protein utilization by catfish fed a winged bean meal diet without L -methionine supplementation (diet 2) was inferior ( P  > 0.05) to that in catfish fed the other diets, where performance differed nonsignificantly. Carcass protein of catfish was lower ( P  < 0.05) while liver protein was higher ( P  < 0.05) in catfish fed the winged bean meal diet without methionine supplementation. Results suggest that winged bean meal cannot replace fish meal as a protein source in catfish diets except with a minimum supplementation with 5 g L -methionine kg⁻¹ diet.     

Swimming performance of wild and F1-hatchery-reared Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) smolts

Abstract –  The swimming performance of wild and hatchery-reared smolts of two salmonid species was investigated. Wild Atlantic salmon smolts (WS) and brown trout smolts (WT) of equal size were caught in fish traps during migration. Hatchery-reared smolts of both species (HS and HT for salmon and trout respectively) were first generation offspring from wild broodstock. The swimming performance of individual smolts from the four groups (WS, HS, WT, HT) was tested three consecutive times using a swimming flume with water flowing at a start rate of 0.16 m·s⁻¹ and a constant acceleration rate of 0.167 cm·s⁻² (10 cm·s⁻¹·min⁻¹). Wild caught smolts of both species performed significantly better than those reared in hatchery conditions. The WS group were observed to maintain an average swimming speed ( U _burst) that was 30% faster than the HS group, whereas the wild trout smolts were superior to HT by approximately 25%. Repeated measures revealed species-specific exhaustion patterns. Brown trout smolts maintained consecutive U _burst indicating significant stamina compared with Atlantic salmon smolts that were found to be exhausted by the initial trial.     

Recreational catfish harvest in reservoirs in the USA

The recreational catfish harvest was classified in 349 reservoirs larger than 200 ha distributed over 40 states of the contiguous USA. Harvesting occurred in 282 reservoirs, averaged 2.8 kg ha⁻¹ year⁻¹ and represented 15.6% of the total fish yield. The genus Ictalurus contributed most to catfish fisheries (mean = 2.0 kg ha⁻¹), followed by Ameiurus (1.1 kg ha⁻¹) and Pylodictis (0.4 kg ha⁻¹). Five distinct clusters of reservoirs were identified, differing relative to geographical distribution, catfish harvests, angler favouritism towards catfish and physicochemical characteristics. Reservoir clusters across the northern USA had low harvests and essentially featured reservoirs in the upper periphery of the native range of catfish. Harvesting in reservoirs in the south-west of the country, where catfish have been introduced, was higher than in the north, yet yield remained low. Within their native range, three overlapping clusters included one with medium and another with high harvests, both types dominated by Ictalurus, and a cluster with very high harvest dominated by Ameiurus . Variability in harvests was attributed to zoogeography, reservoir physicochemical characteristics and fishing effort. Management of catfish fisheries of the three less-productive clusters may focus on enhancement through habitat manipulation and stocking; the two more productive clusters offer the greatest flexibility for management through regulation of harvest.     

Effects of the probiotic, Lactobacillus acidophilus, on the growth performance, haematology parameters and immunoglobulin concentration in African Catfish (Clarias gariepinus, Burchell 1822) fingerling

This experiment was carried out to evaluate the effects of the probiotic, Lactobacillus acidophilus , on the growth performance, haematology parameters and immunoglobulin concentration in African catfish Clarias gariepinus fingerling. Two experimental diets were formulated to contain 35 g kg⁻¹ crude protein and 10 g kg⁻¹ lipids accordingly and fed three times daily for 12 weeks to 25 C. gariepinus fingerlings per fibreglass tank in 12 replicates each. The control diet was prepared with no probiotic supplementation whereas the second diet was prepared supplemented with a probiotic, L. acidophilus , containing about 3.01 × 10⁷ colonies/g of diet. The results show that growth performance [specific growth rate (SGR) and relative growth rate (RGR)], nutrient utilization [protein efficiency ratio (PER) and feed conversion ratio (FCR)] and survival were significantly ( P <0.05) higher in fish maintained on the probiotic-supplemented diet compared with those on the control diet. Haematology parameters (packed cell volume, haemoglobin, erythrocyte sedimentation rate, red blood cell and white blood cell, total serum protein, Ca²⁺, Mg²⁺, Cl⁻, glucose and cholesterol) and total immunoglobulin concentrations were also significantly better in fish fed the probiotic-supplemented diet than in the control. Although the water quality parameters monitored were better in the fish fed the probiotic-supplemented diet than in the control, the parameters were not significantly different ( P >0.05). From the results of this experiment, we conclude that L. acidophilus can be used as a probiotic agent in African catfish culture, to enhance fish health, survival and better feed efficiency and growth performance.     

Metabolic costs of changing the cation–anion difference in the diet of juvenile African catfish Clarias gariepinus (Burchell)

The influence of dietary cation–anion difference (CAD, Na⁺ + K⁺– Cl^–, mEq kg^–1) on energy metabolism and nitrogen losses in juvenile African catfish Clarias gariepinus (Burchell) was examined in fish exposed to different dietary CAD levels (–146, 116, 497, 713 and 828 mEq kg^–1 diet). The experiment was conducted in open circuit balance respiration chambers over a 3-week period. Five 24-h monitoring periods were carried out at 3-day intervals during the experimental period with O₂ consumption, ammonia and nitrate + nitrite (NO_x) and CO₂ production being measured at 5-min intervals for each chamber. The negative dietary CAD (–146 mEq kg^–1) resulted in the highest energy expenditures (83 kJ kg^–0.8· d^–1). With increasing dietary CAD levels, heat loss gradually decreased to minimum values of 56 kJ kg^–0.8 day^–1 at a dietary CAD level of 713 mEq kg^–1. Consequently, metabolizable energy utilization efficiency (MEU, percentage of retained energy over metabolizable energy) quadratically ( P  < 0.05) increased and reached a maximum at a dietary CAD of 713 mEq kg^–1.     

Behaviour of immature yellowtails (Seriola quinqueradiata) observed by electronic data-recording tags

The long-term behaviour of immature yellowtails, Seriola quinqueradiata , was studied using electronic data-recording tags in Sagami Bay, Japan, during the autumn and early winter. Temperature or depth data were continuously recorded for 5–69 days on six yellowtails. The temperature recorded from the 0-year-old yellowtails showed only small variations (<0.5°C day⁻¹) around the SST on the coast, indicating the 0-years stayed in the immediate coastal area with little horizontal movement. The 1-year-old yellowtail showed larger temperature variations that reached 3°C day⁻¹, which implies distinctly larger horizontal movements than the 0-year-olds. Depth records showed the 0-years stayed around 10 m while the 1-year yellowtail swam in deeper water (mainly 10–30 m) with large variations. The latter often dived to 40 m in the daytime, but shallower than the depth of the thermocline. Both temperature and depth records showed apparent diurnal patterns. Comparing the fish data with environmental conditions, it is suggested that 1-year yellowtails stay close to the coast during the night, move at dawn to feed in the daytime and return at dusk via a frontal zone. In addition, wind stress could change yellowtails' behaviour.     

Histopathology, electron microscopy and isolation of channel catfish virus in experimentally infected European catfish, Silurus glanis L.

Abstract Two groups of European catfish, Silurus glanis L., fingerlings were infected with channel catfish virus (CCV) by either intraperitoneal injection with 10⁵ TCID₅₀ of CCV, or bathing in water containing 10⁵ TCID₅₀ of CCV per 1·0 ml. The virus was isolated from spleen, intestine and brain of CCV-injected fish at day 1 and the titres ranged from 10^2·1 to 10^3·3 TCID₅₀/g. However, the tissue distribution of CCV was irregular and no virus was isolated after day 3 post-exposure. In CCV-bathed fish, the virus was isolated only from the liver of one specimen at day 3 post-exposure. No clinical signs of CCV disease developed in any of the fish. Specimens in each regime from all sampling periods showed some minor histopathological changes, but there were no differences between treatments. Lesions included oedema and focal haemorrhage in the liver and the spleen was congested. Electron micrographs of tissue samples showed the presence of a few virus particles around the nuclei of kidney, spleen and intestinal cells, and in or around a myelinated nerve within the optic lobes of infected fish during the first 4 days of infection.     

Individual variability of diel vertical migrations in European vendace (Coregonus albula) explored by stationary vertical hydroacoustics

Abstract –  Diel vertical migration (DVM) is a widespread behavioural pattern in populations of aquatic animals. Its adaptive value is explained by a trade-off between the protection against visually feeding predators in the dark hypolimnion during daytime, and a higher food uptake in the upper food-rich layers during the night. Whereas vertical migration patterns of entire populations have been frequently described, less is known with respect to individual variability of DVM within fish populations. Here, individual migration patterns of European vendace ( Coregonus albula ) are described, obtained by stationary vertical hydroacoustics in Lake Stechlin (Germany) during the dusk and dawn phases of 2 months in 2004. The variability of speeds of depth change was high, with only a few fish rising or falling faster than 1 cm s⁻¹. Swimming activity was not dependent on fish size. There was some evidence that variability of echo strengths was highest in those fish which showed the greatest three-dimensional swimming distances which might indicate a limited swimbladder compensation during vertical migrations. However, migration seems to be performed mainly in a saltatory mode with vertical swimming always interrupted by phases of constant depth. It is suggested that these phases are used for pressure compensation by fish with the consequence that overall the frequency distribution of target strengths deviates only slightly between the start and the end of the recordings. Stationary hydroacoustics proved to be a useful tool for studying individual fish swimming behaviour.     

Habitat use and movement of river blackfish (Gadopsis marmoratus R.) in a highly modified Victorian stream, Australia

Abstract –  Movement and habitat use of river blackfish ( Gadopsis marmoratus R.) was studied in a highly modified central Victorian stream (Birch Creek), Australia, using radio telemetry ( N  = 10) and mark–recapture ( N  = 113) between October 2001 to May 2002, and November to December 2002 respectively. Blackfish had a small home range of 10–26 m with strong affinity to a pool. However, small movements within a pool were common which resulted in relatively large cumulative movements. At a diel scale there were no significant differences in blackfish movement between day and night (Kruskal–Wallis test, P  = 0.95). Six of seven blackfish translocated 40 m upstream or downstream of their original positions returned within 48 h, suggesting strong affinity not only to a pool, but also to a small region within a pool. Blackfish utilised slow flowing (0–20 cm s⁻¹) and deep waters (40–60 cm). Blackfish were strongly associated with the instream cover habitats of undercut banks and boulders. Significant differences were recorded in instream cover and water velocity used by blackfish between day and night (Kruskal–Wallis test, P  = <0.01). At night blackfish used open areas with high water velocities whereas during the day blackfish used complex undercut banks with low water velocities.     

Vaccination of Mixed and Full-Sib Families of Channel Catfish Ictalurus punctatus Against Enteric Septicemia of Catfish With a Live Attenuated Edwardsiella ictaluri Isolate (RE-33)

These studies were conducted to evaluate the efficacy of a live attenuated Edwardsiella ictaluri vaccine against enteric septicemia of catfish. In one study channel catfish fingerlings (72 d of age post hatch) were immersed for 30 min in water containing E. ictaluri RE-33 at dosages of 1 × 10⁶, 1 × 10⁷ and 2 × 10⁷ CFU/ML of water. No mortalities were observed following vaccination. Following exposure to virulent Edwardsiella ictaluri the cumulative mortality of fish vaccinated with dosages of at least 1 × 10⁷ CFU/mL were significantly lower than that of non-vacccinated fish in both laboratory and field challenges. Vaccination with 1 × 10⁶ CFU RE-33mL provided some protection during the laboratory challenge but failed to protect fish under field conditions. In a second study, vaccination of 6 full-sib families of channel catfish at a vaccine dosage of 1 × 10⁷ CFU/mL resulted in a relative percent survival among families ranging from 67.1 to 100%. Significant differences in mortality were found among families and between vaccinated and unvaccinated groups, but there was no family by vaccine interaction. Families with the highest mortality after vaccination were also shown to have the highest mortality without vaccination (r = 0.82; P = 0.04).     

Enrichment of African catfish with functional selenium originating from garlic

We wanted to create functional seafood with high concentrations of organic selenium (seleno-methyl-selenocysteine and γ-glutamyl-seleno-methyl-selenocysteine) with anti-carcinogenic properties for human consumers. Garlic containing high concentrations of these organic selenium compounds was used as a selenium source in five experimental feeds for African catfish (1.9, 2.8, 3.9, 5.1 and 8.5 mg kg⁻¹ Se); a sixth experimental feed was formulated without garlic (1.9 mg kg⁻¹ Se). The experimental feeds were fed to African catfish [initial mean (SD) weight 100.7 (2.7) g] for 43 days with three replicates per treatment. Whole fish fillets were sampled for total selenium analysis (start and end) and selenium speciation (end). We found a positive linear relationship between dietary and fillet concentrations for total selenium and selenomethionine. The dietary total selenium concentration of 8.5 mg kg⁻¹ resulted in a total selenium concentration of 0.9 mg kg⁻¹ in the fillet (wet tissue). The majority of the selenium compounds recovered in an extract made from the fillet consisted of selenomethionine, considered to be important from a nutritional point of view. Seleno-methyl-selenocysteine, one of the organic selenium species to which superior anti-carcinogenic properties are attributed, was detected in the fillet but could not be quantified.     

Perception of light intensity by Haliotis discus discus based on locomotor activity patterns

ABSTRACT:   An apparatus to measure the locomotor activity of aquatic benthic organisms at variable low light levels was developed and the diurnal behavioral pattern of the abalone Haliotis discus discus was measured at various low light intensities. During the experiment, abalone were exposed to 12 h light–dark cycles of complete darkness, 0 µmol/m²/s throughout the 12 h dark cycle and, during periods I (days 1–8) and III (days 19–26), the 12 h light cycles were set at 10 µmol/m²/s. During period II (days 10–17), abalone were exposed to a light level during the 12 h light cycles of 1 × 10⁻⁵, 1 × 10⁻⁶, 1 × 10⁻⁷ or 1 × 10⁻⁸ µmol/m²/s and the changes in locomotor activity assessed. At daytime levels of 1 × 10⁻⁵ µmol/m²/s, typical behavioral patterns were observed of high locomotory activity during the night-time cycle. However, at lower light intensities, the distinction between day and night activity patterns became less clear and, at intensities lower than 1 × 10⁻⁷ µmol/m²/s, the difference between activity during the light and dark cycles became negligible. Based on this, we conclude that the threshold of light level perception in relation to locomotor activity is approximately 1 × 10⁻⁷ µmol/m²/s. The significance of these results in relation to the entrainment of behavior in abalone is discussed.     

Evaluation of diquat against an acute experimental infection of Flavobacterium columnare in channel catfish, Ictalurus punctatus (Rafinesque)

A trial was performed to evaluate the efficacy of diquat (6,7-dihydrodipyrido[1,2-a:2',1'-c]pyrazinediium dibromide) against an acute experimental infection of Flavobacterium columnare in channel catfish, Ictalurus punctatus . Diquat is an Environmental Protection Agency-approved herbicide and has the potential to be legally and practically used against columnaris. Channel catfish were challenged, by cutaneous abrasion, and waterborne exposure to F. columnare and treated once at 22-h post-challenge with 2.5, 5.0, 10.0 and 15 mg L⁻¹ of diquat active ingredient for 6 h. At the conclusion of the trial, 21-day post-challenge, diquat at 5.0, 10.0 and 15 mg L⁻¹ significantly ( P  < 0.05) reduced the mortality of infected fish from 95% in the challenged non-treated fish to 68%, 59% and 49%, respectively. In vitro , the minimum inhibitory concentration (MIC) of 23 isolates of F. columnare was assayed. The majority of the isolates had an MIC value of 5 μg mL⁻¹ (15 of the 23 isolates). Infected fish exhibited acute clinical signs similar to a natural infection. The skin had severe ulcerative necrotizing dermatitis and the muscles had severe necrotizing myositis. The gills had severe multifocal necrotizing branchitis. The results demonstrate that diquat would reduce mortalities caused by an acute columnaris infection.     

Effects of dietary protein to metabolizable energy ratios and total protein concentrations on the performance of yellow perch Perca flavescens

Juvenile yellow perch Perca flavescens were fed semipurified diets with varying protein to metabolizable energy ratios (PME, g protein MJ⁻¹ metabolizable energy) and nutrient densities in three experiments to determine recommended dietary protein and energy concentrations. Experiment 1 fish (18.6 g) were fed diets containing 450 g crude protein kg⁻¹ dry diet and 14.5–18.8 MJ ME kg⁻¹ dry diet for 10 weeks. No differences were found in the growth of experiment 1 fish fed the different diets. Experiment 2 fish (21.9 g) were fed diets containing 15.7 MJ ME kg⁻¹ dry diet and 210–420 g crude protein kg⁻¹ dry diet for 8 weeks. Fish fed the diet containing 340 g kg⁻¹ protein (diet PME = 22) exhibited the greatest weight gain. Experiment 3 fish (27.1 g) were fed diets with a PME of 22 and varying nutrient density (yielding 205–380 g crude protein kg⁻¹ dry diet) for 8 weeks. No differences were found in the growth of experiment 3 fish. Yellow perch fed the semipurified diets exhibited increased liver fat content, liver size and degree of liver discoloration compared with fish fed a commercial fish meal-based diet. Liver changes may have resulted from high dietary carbohydrate levels. We conclude that a protein level of 210–270 g kg⁻¹ dry diet is suitable for juvenile yellow perch provided that the dietary amino acid profile and carbohydrate content are appropriate for yellow perch.     

Effect of water temperature on the growth performance and digestive enzyme activities of Chinese longsnout catfish (Leiocassis longirostris Günther)

The present study was carried out to investigate the influence of water temperature on the growth performance and digestive enzyme (pepsin, trypsin and lipase) activities of Chinese longsnout catfish. Triplicate groups of Chinese longsnout catfish (35.6±0.48 g, mean±SE) were reared at different water temperatures (20, 24, 28 and 32 °C). The feeding rate (FR), specific growth rate (SGR) and feed efficiency ratio (FER) were significantly affected by water temperatures and regression relationships between water temperature and FI, SGR as well as FER were expressed as FR=−0.016 T ²+0.91 T −10.88 ( n =12, R ²=0.8752), SGR=−0.026 T ²+1.39 T −17.29 ( n =12, R ²=0.7599) and FER=−0.013 T ²+0.70 T −8.43 ( n =12, R ²=0.7272). Based on these, the optimum temperatures for FR, SGR and FER were 27.66, 26.69 and 26.44 °C respectively. The specific activities of digestive enzymes at 24 or 28 °C were significantly higher than that at 20 or 32 °C. In addition, there was a significant linear regression between FR or SGR and specific activities of pepsin and lipase, which indicated that pepsin and lipase played important roles in regulating growth through nutrient digestion in Chinese longsnout catfish.     

Effect of population density on the growth, feed and protein conversion efficiency and biochemical composition of a tropical freshwater catfish, Mystus nemurus (Cuvier & Valenciennes)

Abstract. Six groups of tropical freshwater catfish, Mystus nemurus (Cuvier & Valenciennes)(mean weight. 20·45 ± l·5g), were reared in 0·34m³ fibreglass tanks at different stocking densities (105, 195, 285, 375, 465 and 555 specimens/m³ water) for 84 days. The objective of the study was to determine the effect of various stocking densities on the growth, nutrition, biochemical composition and survival of M. nemurus. The lowest growth rate appeared in fish at the highest density and the highest was observed in fish stocked in moderate density of 285 and 375 fish/m³ water. Fish production was also lower at relatively low stocking densities of 105 and 195 fish/m³. Food conversion ratio (FCR), protein efficiency ratio (PER) and biochemical composition of M. nemurus indicate that there exists an optimum stocking density which lies between 285 and 375 fish/m³.     

Evaluation of lipid spray beads for the delivery of water-soluble materials to a marine suspension-feeder, the Manila clam Tapes philippinarum (Deshayes 1853)

We describe the development and evaluation of a new microparticle for delivering low-molecular weight, water-soluble materials to suspension feeders. Spray beads successfully incorporated materials dissolved in an aqueous phase or as dry particulate, within a triacylglyceride bead composed of tripalmitin, 600 mg g⁻¹ tripalmitin/400 mg g⁻¹ triolein, or 600 mg g⁻¹ tripalmitin/400 mg g⁻¹ fish oil.
Riboflavin was successfully incorporated (up to 44 mg g⁻¹ lipid) and retained (up to 98% over 24 h in seawater) as dry particles in all three mixtures of lipid. Aqueous oxytetracycline hydrochloride or polymeric dye were incorporated (45.6 mg g⁻¹ lipid and 18.1 mg g⁻¹ lipid, respectively) and retained best (99% and 94%, respectively) in spray beads composed of tripalmitin. The addition of triolein or fish oil to the lipid bead reduced incorporation and retention efficiencies for aqueous core materials by up to 75%.
Manila clam seed readily ingested and digested lipid microparticles, spray beads and lipid-walled microcapsules. Microparticles composed of tripalmitin were excreted with their payloads intact. Intact microparticles composed of 600 mg g⁻¹ tripalmitin/400 mg g⁻¹ fish oil were largely absent in faecal strands suggesting successful release and delivery of microparticle contents to clams.
Spray beads composed of tripalmitin softened with 400 mg g⁻¹ fish oil represent an effective microparticle type for delivering low-molecular weight, water-soluble materials to aquatic suspension feeders.     

Diel vertical migration of myctophid fishes (Family Myctophidae) in the transitional waters of the western North Pacific

The diel vertical migration patterns of adult myctophid fishes were determined in the transitional waters of the western North Pacific off Japan, using day–night sampling from 20 to 700 m depths with a commercial otter trawl in the summer of 1995. A total of 12 species belonging to 9 genera were collected. Four patterns were recognized in the diel vertical migration of 11 of the 12 species. (1) Migrants showing clear day–night habitat separation with peak abundance above 200 m at night: Symbolophorus californiensis, Tarletonbeania taylori, Notoscopelus japonicus, Diaphus theta, Ceratoscopelus warmingi, and Diaphus gigas. (2) Semi-migrants, in which part of the population often remains in the daytime habitat at night. The distribution depths of migratory and nonmigratory individuals do not overlap: Stenobrachius leucopsarus . (3) Passive-migrants, in which there is no separation of day–night habitats, but the upper limit of daytime distribution depth shifts to a shallower layer at night, probably as the fish follow migratory prey: Lampanyctus jordani . (4) Nonmigrants: Stenobrachius nannochir, Lampanyctus regalis (> 140 mm SL), and Protomyctophum thompsoni . The day–night habitat temperature ranges are also given for the 11 species. No remarkable east–west differences were seen in the vertical migration patterns compared with previous knowledge of eight of these species in the eastern Pacific. The diel migration patterns are newly described for three other species endemic to the western Pacific. The standing stock of myctophids in the study area was conservatively estimated at 18.5 ± 4.7 g m⁻² (avg. ± SD).