Induction of ovulation in the loach (Paramisgurnus dabryanus) using pimozide and [D-Ala6, Pro9-N-ethylamide]-LHRH

The effects of intraperitoneal injections of [D-Ala⁶, Pro⁹-N-ethylaminde]-luteinizing hormone releasing hormone (LHRH-A) and pimozide (PIM), a dopamine receptor antagonist, on ovulation in loach were investigated. LHRH-A and PIM administered separately were ineffective in inducing ovulation. However, injections of PIM and LHRH-A simultaneously or the injection of PIM 2.5–3 h prior to LHRH-A were highly effective means of inducing ovulation. The simultaneous injection of PIM (1.0 μg/g body wt) and LHRH-A (0.05 μg/g body wt) resulted in a greater ovulatory response than injection of carp pituitary extract (1 pituitary/fish).     

Postlarval growth of the freshwater prawn, Macro-brachium australiense Holthuis, 1950 (Crustacea: Decapoda: Palaemonidae)

Growth of newly metamorphosed Macrobrachium australiense was monitored in individually vidually held and group held laboratory animals over 28 weeks. A breeding population was also established in a farm dam and the growth of young juvenile F₁ progeny was recorded for a similar time. Up to 26 moults were recorded in this period and intermoult periods increased with age. Prawns held in groups grew better than those held individually. Reproductive maturity was attained by some females in group held laboratory and farm dam animals within the observation period. Length—weight regression equations were calculated for laboratory maintained prawns, i.e., log W = 0.44+ 2.44 log L; log W = 0.45 + 2.46 log L for individually held males and females, respectively; log W = 0.27 + 2.70 log L for group held males and females.     

The growth of rainbow trout (Salmo gairdneri) given diets containing chitin and its relationship to chitinolytic enzymes and chitin digestibility

The growth of rainbow trout fed diets containing 4, 10 and 25% chitin, over a 12-week period, was significantly depressed (P < 0.001) when compared with controls fed diets containing 25% starch. There was no difference in growth rate between control fish and those fed diets containing 10% N-acetyl glucosamine (GlcNAc). Isotopically labelled amino sugars were shown to be oxidized when injected intraperitoneally into rainbow trout. Relatively high levels were found of chitinase activity in the stomachs and of chitobiase in the intestines. These enzyme activities were similar in all the trout, irrespective of the amount of chitin in their diets, except that chitobiase in the intestines of fish fed diets containing GlcNAc showed higher levels of activity than the controls (P < 0.05). Chitin was not significantly digested when fed at 10 and 30% of the diet but the apparent digestibility of pre-cooked starch was 50% when fed at either 15 or 25%, on the basis of the inert indicator (Cr₂O₃) method. Chitinase and chitobiase activities were not reduced in fish fed diets containing 10% chitin and an antibiotic (Tribrissen^®) although the alimentary microflora were completely eliminated. Enzyme activities were not enhanced when live chitinolytic bacteria (Vibrio alginolyticus) were incorporated into diets with 10% chitin; these bacteria were only recovered from the intestine. The evidence indicates an endogenous origin of chitinolytic enzymes in the trout gastro-intestinal tract. The presence of either antibiotic or bacteria in the diet had no effect on the digestibility of chitin.     

Effect of feeding frequency on growth and food conversion of Cyprinus carpio fry

Cyprinus carpio fry (173 ± 38 mg) were fed 6 times a day, 3 times a day, 2 times a day, once a day, once in 2 days, once in 3 days or given no food at all for a total period of 21 days. Food consumption by the group fed 3 times a day was maximum (45.6 gcal^*/meal) and the level of consumption per meal was very low in the remaining groups.

Feeding rate increased to a maximum (598.2 gcal g⁻¹ day⁻¹) in fry fed 3 times a day; a further increase in feeding frequency reduced the feeding rate. Feeding frequency influenced all bioenergetic parameters except absorption efficiency which remained constant at 97.7%. Although the growth efficiency did not change significantly in the groups fed very frequently (2 times a day or more), the growth rate was maximum in the group fed 3 times a day. With regard to both feeding and growth, a feeding schedule of 3 times a day seemed to be optimum and was suggested for practical nursery culture of Cyprinus carpio.     

Effects of feeding glandless or glanded cottonseed products and gossypol to Tilapia aurea

Seven isocaloric and isonitrogenous practical diets in which either glanded or glandless cottonseed products were substituted for soybean and/or peanut meals, and three purified diets containing graded levels of gossypol were fed to fingerling Tilapia aurea for a period of 10 weeks. Growth, feed conversion and survival data indicated that glanded and glandless cottonseed products were not as high in nutritive value for tilapia as are soybean and peanut meals. The inferior performance of fish fed cottonseed protein did not appear to be related to dietary gossypol. Carcass fatty acids generally reflected dietary fatty acids. An increase in palmitic and linoleic fatty acids was observed in fish fed fullfat, glandless cottonseed flour.     

Efficiency of local feeds for the common carp (Cyprinus carpio L.) in Saudi Arabia

The effects of feeding three local feeds (53%, 43% and 33% protein) on the growth and quality of the common carp (Cyprinus carpio L.) were investigated. The 43% protein feed proved most economical, with the highest biological value and has increased the protein and amino acid contents of the flesh but resulted in poor fish growth (0.10 g/day).     

Improvement in the feeding efficiency of larval,post larval and juvenile Dover sole (Solea solea L.) by the use of staining to improve the visibility of Artemia used as food

The feeding efficiency of larval, post larval and juvenile Dover sole (Solea solea L.) was studied by using Artemia stained with five different food colourings — brilliant blue, pink, lemon yellow, red “C” and black.The results show that the feeding efficiency is markedly improved by this treatment. The maximum feeding efficiency was found using black stained Artemia and minimum for the unstained control. This clearly suggests that the contrast perception of the food in relation to the illumination of the background is of major importance especially during the critical weaning period of the larval stage when feeding is being established.     

The influence of diet and fish density on apparent heat increment in rainbow trout, Salmo gairdneri

Rainbow trout were held in densities of 15, 35 or 50 fish per tank (2.48–8.27 kg m^?3) and fed one of six balanced diets varying in protein (34%, 48%, 58%) and lipid levels (7%, 23%). The elevation in oxygen consumption following feeding was attributed to apparent heat increment. Apparent heat increment tended to increase with dietary protein for each of the two lipid levels within each density of fish. A significant change in apparent heat increment relative to digestible energy was not demonstrable with dietary protein for each lipid level and fish density. When dietary lipid was high, the fraction of energy lost through apparent heat increment was improved and tended to decrease with dietary protein. Thus, a decrease in dietary protein with a concomitant increase in lipid provides for a more efficient utilization of dietary protein for growth. Apparent heat increment varied directly with rainbow trout density on the basis of equivalent weights and diets.     

Effects of container transparency and reflectivity upon oxygen consumption of hybrid lobsters

The effect of intra-specific visual communication on the rate of oxygen consumption of hybrid lobsters (Homarus americanus × H. gammarus) was tested in a partitioned metabolic chamber. Three partition linings were tested: opaque rubber, clear plexiglass, and glass mirror. Short-term mean oxygen comsumption rates observed for lobsters separated by rubber-lined partitions were 8% lower than those of lobsters separated by the clear partitions, and 29% lower than those of lobsters separated by mirrored partitions (P < 0.001).     

Cryogenic preservation of spermatozoa from Prochilodus scrofa and Salminus maxillosus

This paper reports an initial trial to cryopreserve semen from two freshwater South American fishes, the curimbatá (Prochilodus scrofa) and the dourado (Salminus maxillosus). Motility and duration of motility were observed in curimbatá and dourado fresh sperm. Semen mixed with extender (0.8% NaCl) was frozen using vials (1 ml) with subsequent storage in liquid nitrogen. Samples were thawed in 1% NaHCO₃ or in 0.8% NaCl solutions. Post-thawing motility and duration of motility were verified. A simple extender consisting of 0.8% NaCl plus 10% DMSO was able to initiate motility in fresh spermatozoa. The percentage of motile cells and duration of motility were similar in both thawing solutions, but lower than in fresh sperm.     

High density flow-through culturing of brine shrimp Artemia on inert feeds — Preliminary results with a modified culture system

A modified filter system is described for the intensive culturing of Artemia in a continuously renewed medium. Extrapolated to a 1 m³ tank, 25 kg live weight Artemia could be produced over a culture period of two weeks on a diet of micronized and defatted rice bran using the salt enriched effluent of an abandoned geothermal well as a culture medium.     

Early detection of triploidy in the larvae of Pacific oysters,Crassostrea gigas,by flow cytometry

Triploidy may provide a means to neuter the Pacific oyster, C. gigas, genetically thereby increasing survival and marketability during periods of reproduction. Pressure treatments administered 10 min after fertilization for 10 min duration at 6000–8000 psi consistently produced triploids. The highest proportion obtained was 57%. Triploidy was assayed in all experiments at the larval stage and again as spat (metamorphosed larvae) using flow cytometry. A technique to assay larvae as small as 250 μm is described. Results obtained by flow cytometry were verified by chromosome counts. Analysis of triploidy at the larval stage provides reliable estimates of the proportion of triploids, eliminating several weeks of culture time.     

Norwegian reference strains of Vibrio anguillarum

Strains of Vibrio anguillarum isolated from rainbow trout (Salmo gairdneri) and saithe (Gadus virens) have been studied and compared, and strains to be used for further investigations are described.     

An estimate of the dietary calcium requirement of fingerling Tilapia aurea reared in calcium-free water

Seven isocaloric and isonitrogenous semi-purified diets which contained graded levels of calcium ranging from 0.17 to 3.20% were fed to fingerling Tilapia aurea for a period of 11 weeks. The fish were maintained in a flow-through aquarium system supplied with calcium-free well water. Growth, feed conversion and bone composition data indicated that between 0.17 and 0.65% dietary calcium was adequate for optimum growth and normal bone mineralization.     

Effects of feeding diets containing an imbalance of branched-chain amino acids on fingerling channel catfish

A series of studies was conducted to investigate the effects of feeding diets imbalanced with respect to branched-chain amino acids on channel catfish. Basal diets contained casein and gelatin supplemented with crystalline L-amino acids to correspond to the amino acid pattern found in 24% whole egg protein except for the branched-chain amino acids. Basal diets were formulated to be deficient in either leucine, isoleucine, or valine. Excess levels of either leucine, isoleucine, or valine were added to the appropriate basal diet. Growth and feed efficiency data demonstrate that excess leucine depressed growth of fish fed diets deficient in isoleucine or valine, but not in diets adequate in branched-chain amino acids. The deleterious effects of excess leucine could be reversed by supplementation with the deficient amino acid, but not by the other branched-chain amino acid. Growth was also depressed in fish fed excess isoleucine but not valine in leucine-deficient diets. Serum levels of isoleucine and valine suggest that leucine may control the tissue uptake of these amino acids in the channel catfish.     

Effects of biotin deficiency in rainbow trout (Salmo gairdneri) fed diets of different lipid and carbohydrate content

The effects of variations in diet composition on biotin deficiency symptoms were studied in rainbow trout. Fish were fed one of six diets differing in lipid type, carbohydrate and biotin content. Fish given biotin-deficient diets gained less weight, and had inferior feed conversion ratios than the appropriate controls but did not suffer from anorexia nor were any pathological signs observed either by gross or microscopic analysis. Marked reduction in liver biotin concentration and activities of pyruvate carboxylase and acetyl CoA carboxylase, characteristic of biotin deficiency, were observed. Some less marked changes also occurred in the levels of other liver components and enzymes; these changes were influenced by diet composition as well as biotin intake. Hepatic lactate levels tended to increase in biotin deficiency when diets contained starch while the activities of citrate synthase and α-ketoglutarate dehydrogenase decreased, but these changes were reversed when diets lacked starch. Consequently, some secondary effects of biotin deficiency are related to diet composition. In certain treatments, palmitic and oleic acids in muscle triglycerides of biotin-deficient trout were significantly lower than in control fish; but there was no evidence among muscle lipids of chain elongation of linolenic acid in trout given biotin-supplemented diets.     

Serotonin stimulates ovarian maturation and spawning in the black tiger shrimp Penaeus monodon

Serotonin (5-hydroxytryptamine, 5HT) has been reported to induce ovarian maturation and spawning in the crayfish Procambarus clarkii and white Pacific shrimp Litopenaeus vannamei. The aim of this study was to explore the role of exogenous 5HT on the reproductive performance of the black tiger shrimp Penaeus monodon. 5HT solution was injected into domesticated P. monodon broodstock at 50 μg/g body weight and ovarian maturation and spawning were recorded. The presence of 5HT in the ovary and oviduct of P. monodon was also studied by immunohistochemistry and its levels in the ovary by enzyme link immunoabsorbance assay (ELISA). The 5HT-injected P. monodon developed ovarian maturation and spawning rate at the level comparable to that of unilateral eyestalk-ablated shrimp. Hatching rate and the amount of nauplii produced per spawner were also significantly higher in the 5HT-injected shrimp, compared to the eyestalk-ablated shrimp. 5HT-positive reactions were found in the follicular cells of pre-vitellogenic oocytes, in the cytoplasm of early vitellogenic oocytes and on the cell membrane and cytoplasm of late vitellogenic oocytes. 5HT in the ovary was present at 3.53 ± 0.26 ng/mg protein level in previtellogenic stage and increased to 17.03 ± 0.57 ng/mg protein level in the mature stage of the ovary. The results suggest a significant role of 5HT, possibly directly on the ovary and oviduct, on the reproductive function of female P. monodon.     

Nutritional studies on penaeid prawns: Protein requirements in compounded diets for juvenile Penaeus indicus (Milne Edwards)

The use of dried prawn meal as a high quality reference protein in the nutrition of juvenile Penaeus indicus was investigated through short term growth and feed efficiency trials. Complete substitution at the same level of crude protein gave significantly improved growth rates relative to a control fish meal ration. Live-weight gain at levels ranging from 21–53% crude protein was greatest with a 43% protein diet, although efficiencies of protein utilisation (recorded as P.E.R. values) declined with successive increases in dietary protein. A second experiment to assess the effect of partially replacing prawn meal with fish meal showed that isonitrogenous substitution could be effected to an apparent optimal ratio of 60% fish meal: 40% prawn meal protein. In terms of short term growth and feed efficiency results, this particular meal combination was superior to either prawn or fish meal alone.     

Seasonal and nutritional effects on the fatty acids of three species of shrimp, Penaeus setiferus,P. aztecus and P. duorarum

The fatty acids of three species of shrimp from the Gulf of Mexico, white (Penaeus setiferus), brown (P. aztecus), and pink (P. duorarum), were analyzed periodically for 1 year. The fatty acid patterns of varied species of shrimp collected at the same time of the year differed very little from each other. On the other hand, a slight but distinctive seasonal variation of the fatty acid composition, irrespective of Penaeus species, was observed. Saturated fatty acids increased during the warm seasons and decreased during the cold months, while the opposite behavior was exhibited by monoenoic and polyenoic fatty acids. When the variations in fatty acid levels were compared to the temperature of the water, there was a 2-month lag period between a change in water temperature and the corresponding variation in fatty acid composition. This slow alteration of the shrimp fatty acids suggests that the changes are effected through the food chain rather than by endogenous adjustment to an alteration in water temperature.Further studies were performed in which the fatty acid patterns of pond- and laboratory-reared shrimp were compared with those of their food. Evidence was obtained confirming the significant effect of diet on the fatty acids of shrimp lipids. Shrimp incorporated certain dietary fatty acids readily but showed little ability for the conversion of C₁₈ polyunsaturated fatty acids into C₂₀ and C₂₂ fatty acids of higher unsaturation. Thus, the C₂₀ and C₂₂ fatty acids which are essential for shrimp growth cannot be substituted in the diet by C₁₈ precursors.Considered in toto, these experiments suggest that diet exerts a strong influence on the composition of shrimp body lipids and that, contrarily, endogenous synthesis or modification occurs to a low degree.     

Suitability of the copepod, Acartia clausi as a live feed for Seabass larvae (Lates calcarifer Bloch): Compared to traditional live-food organisms with special emphasis on the nutritional value

Though artificial propagation of Asian seabass Lates calcarifer (Bloch) in captivity through induced breeding techniques is standardized under Indian conditions, larval and nursery rearing techniques including suitable nursery feeds have to be standardized to obtain better survival and growth. Feeding experiments in triplicate were conducted to evaluate the suitability of the marine copepod Acartia clausi as live prey for fourteen day-old seabass larvae (6.53 ± 0.06 mm; 8.58 ± 0.33 mg) and compared with the traditional live prey, rotifers and Artemia nauplii. While A. clausi and rotifers were mass produced using algae Isochrysis galbana, Chaetoceros affinis and Chlorella marina, Artemia nauplii were produced using cysts. Nutritional quality of cultured copepods was evaluated based on the proximate composition, amino acid and fatty acid composition, and compared with that of rotifers and Artemia nauplii. Proximate composition varied significantly (P < 0.05) among the different live feeds. A. clausi showed higher protein (63.12%) and lipid (16.65%) content than Artemia nauplii and rotifers. Total essential amino acids content was 2% lower in A. clausi compared to that in Artemia nauplii. Fatty acid profiles of the live feed organisms showed that A. clausi is a rich source of n − 3 fatty acids. The total n − 3 fatty acid content of A. clausi was 33.94%. Length, weight overall weight gain and survivorship were significantly (P < 0.05) different among the dietary treatments, and weight gain was comparatively higher in A. clausi fed larvae. Survival of seabass larvae fed A. clausi was obtained highest as 58.13% against the lower values of 39.93% and 41.62% in larvae fed rotifer and Artemia nauplii respectively. Final carcass composition of the larvae of L. calcarifer fed different live-food organisms showed significant differences (P < 0.05) among the dietary treatments. The fatty acid composition of the dietary treatments was reflected to a certain extent in the fatty acid composition of the seabass larvae. The present investigation revealed the nutritional value of calanoid copepod and thus underlining its usefulness as a suitable live-food organism for rearing larvae of the commercially valuable Asian seabass.