Showing papers in "Journal of The World Aquaculture Society in 1993"

Importance of Docosahexaenoic Acid in Marine Larval Fish

Abstract: Marine finfish require n-3 HUFA such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as essential fatty acids (EFA) for their normal growth. But it remained unclear as to which of the n-3 HUFA, either EPA or DHA, was important. Unlike the freshwater species, the EFA efficiency of EPA and DHA may vary in marine fish. The developing eggs rapidly utilize DHA either for energy or for production of physiologically important substances like prostaglandin. This report reveals that in marine larval fish DHA is superior to EPA as EFA. In the case of red seabream, feeding rotifers incorporating EPA and DHA or an n-3 HUFA mixture prevented many of the ill-effects observed when the rotifers were low in n-3 HUFA. Apart from the best growth and survival in an activity test for the larvae fed on DHA-rotifer, the incidence of hydrops seemed to be totally prevented dietetically by DHA. Similar results were obtained in larval yellowtail, striped jack, striped knifejaw and flounder. There seems to exist a functional difference between EPA and DHA.

A Review of Cannibalism and its Implications in Fish Larviculture

Abstract: A review of cannibalism is presented with particular emphasis on the role that this phenomenon plays in applied larviculture. Cannibalism is more ubiquitous than previously assumed and its implications under larviculture conditions are significant. The review is focused primarily on the two principal causes of sibling cannibalism. These are genetic and behavioral, the latter being influenced directly by environmental factors. Cannibalism is regarded as an alternative feeding strategy, more likely to be adopted by larvae and early juveniles which are carnivorous, when resources become limiting. Agonistic behavior induced mortality, the causes of which are identical to those of cannibalism, is also dealt with. Experimental results on the effects of several important environmental factors are presented and evaluated, and suggestions are made to reduce mortality rates under larviculture conditions.

Effect of Water Exchange Rate on Production, Water Quality, Effluent Characteristics and Nitrogen Budgets of Intensive Shrimp Ponds

Abstract: Water exchange is routinely used in shrimp culture. However, there are few, if any, systematic investigations upon which to base exchange rates. Furthermore, environmental impacts of pond effluent threaten to hinder further development of shrimp farming in the U.S. The present study was designed to determine effects of normal (25.0%/d), reduced (2.5%/d) and no (Oo/o/d) water exchange on water quality and production in intensive shrimp ponds stocked with Penaeus serverus at 44 postlarvae/m2. Additional noexchange ponds were stocked with 22 and 66 postlarvae/m* to explore density effects. Water exchange rates and stocking density influenced most water quality parameters measured, including dissolved oxygen, pH, ammonia, nitrite, nitrate, Kjeldahl nitrogen, soluble orthophosphate, biochemical oxygen demand, phytoplankton and salinity. Reduced-exchange and no-exchange treatments resulted in reduced potential for environmental impact. Mass balance of nitrogen for the system indicates that 13-46% of nitrogen input via feed is lost through nitrification and atmospheric diffusion. Growth and survival were excellent in ponds with normal exchange, reduced exchange, and a combination of low density with no water exchange. A combination of higher stocking density and no water exchange resulted in mass mortalities. Mortalities could not be attributed to a toxic effect of any one water quality parameter. Production was 6,400 kg/ha/crop with moderate stocking density (44/m2) and reduced (2.5%/d) water exchange and 3,200 kg/ha/crop with lower stocking density (22/m2) and no water exchange. Results indicate that typical water exchange rates used in intensive shrimp farms may be drastically reduced resulting in a cost savings to farms and reduced potential for environmental impact from effluent.

Marine Fish Larvae Feeding: Formulated Diets or Live Prey?

Abstract: In the rearing of larval marine fish, any diet that reduces dependance on live prey production is of technical and economic interest. Weaning juveniles with a completely developed digestive tract to a conventional diet, (i.e., “late weaning”) can be successful in any marine fish species. For example, weaning one-month-old sea bass (20 mg) to the study's reference diet, Sevbar, resulted in over 85% survival (40% from hatching) and 1.25 g fish at day 90 (at 19 C) In contrast, “early weaning” of larvae to special microdiets during the first month is still difficult. The best way to reduce live prey utilization in sea bass is to wean larvae at about 3–4 mg in size (day 20). If weaning could be accomplished 15 days earlier, Artemia savings could be as high as 80%. However, this introduces risks relative to growth retardation (30% weight loss) and lower juvenile quality, including greater size variability and skeletal abnormalities. Similar results have been obtained with commercial microparticles (Fry Feed Kyowa) and experimental microbound diets (MBD) made from raw materials (alginate MBD) or preferably from freeze-dried protein sources (zein MBD). Total replacement of live prey is still impossible in marine fish. Sea bass larvae fed formulated diets exclusively from first feeding (0.3 mg larval wet weight), or even from their second week of life onwards, exhibited low survival and poor growth. Better results can be obtained when formulated diets are used in combination with live prey from first feeding, although the optimal ratio of live prey to formulated diet is still to be specified.

Larval nutritional physiology: studies with Clarias gariepinus, Coregonus lavaretus and Scophthalmus maximus.

Abstract: Studies on the nutritional physiology of larval fish should provide the basis for defining the length of the larval period and for understanding the quantitative and the qualitative feed requirements of the larvae. For these purposes, it is necessary to perform both descriptive investigations on the ontogenesis of structures and functions as well as experimental investigations on adaptive strategies of the larvae under changing feeding regimes. In the present communication, examples of both approaches are discussed comparing three species: African catfish Clarias gariepinus, whitefish Coregonus lavaretus, and turbot Scophthalmus maximus. At the onset of exogenous feeding, the digestive system of all three species is sufficiently developed to ensure efficient utilization of live food, but not of dry food. A major event during the subsequent development is the differentiation of the stomach. Evidence exists that for turbot and catfish, a functional stomach is necessary to utilize dry feeds as efficiently as live feeds. Therefore, from a nutritional point of view, in those two species the larval period, during which a special larval diet has to be given, ends with the completion of stomach differentiation. The capacity of the larvae to acclimate physiologically to different nutritional conditions seems to be limited. Using general nutritional indices such as protease activity, RNA/DNA ratio, midgut cell height or nuclear diameter of hepatocytes, larvae of the three species show partly starvation symptoms when reared on dry food. This effect can be explained to some extent by quantitative considerations, i.e., lower food consumption and digestibility is less for dry diets than for live diets. The contribution of the qualitative factors involved in the different performance of larvae reared on dry or live food is presently not well understood. Future studies should: 1) investigate why utilization of dry diets depends on presence of the stomach; 2) define more precisely the quantitative feed requirements of larvae; and 3) search those diet-induced qualitative differences of larval metabolism which affect growth performance.

Nutritional mechanisms involved in the occurrence of abnormal pigmentation in hatchery-reared flatfish

Abstract: The mass depigmentation (albinism) in the ocular side of flatfish, which resulted from the deficiency of pigments, has widely occurred in the process of seedling production. Although many researchers have investigated the mechanisms of depigmentation, little is known in this field. The author found that depigmentation resulted from nutritional deficiencies when 10 d old larvae were fed experimental microparticulate diets. This paper suggests that the rhodopsin formation of eye retina was hindered when vitamin A, docosahexaenoic acid and phospholipid were deficient in foods, resulting in the interruption of black pigment (melanin) formation.

Feeding larval red drum on microparticulate diets in a closed recirculating water system

Abstract: A feeding protocol was developed for red drum larvae based on combining a commercial microparticulate diet (Kyowa Fry Feed) with live prey (rotifers) in a closed, water reuse system. In five trials, growth and survival were measured on larvae reared on a combination of live and microdiet for 1–5 d and then microdiet alone. Results in each trial were compared to control larvae reared on live rotifers Brachionus plicatilis and brine shrimp nauplii Artemia salinas. The most satisfactory combination was feeding live food and microdiet together for the first five days and then completely discontinuing live prey, eliminating the need to feed brine shrimp to the larvae. Growth rates of larvae fed progressively larger sizes of the microdiet were as good as larvae reared on live prey. Both groups metamorphosed to the juvenile stage at less than one month. Survival rates on the five day live food and microdiet combination were a remarkable 60% from egg to the juvenile stage. The successful weaning of red drum to microdiets paves the way to produce a semipurified diet to test nutrient requirements of larval fish.

Acute Toxicity of Copper Sulfate and Chelated Copper to Channel Catfish Ictalurus punctatus

Abstract: Channel catfish fingerlings Ictalurus punctatus were exposed to copper sulfate or a commercial chelated copper product in a series of static toxicity tests conducted using waters with a wide range of total alkalinity and hardness values. Estimates of mean 96 h LC50 values were 0.05, 0.73, 0.95, and 0.98 mg/L as Cu for copper sulfate and 0.06, 1.51, 1.97, and 1.74 mg/L as Cu for the chelated copper product in waters having total alkalinities of 16, 76, 127, and 240 mg/L CaCO3 respectively. On a copper basis, the chelated product was significantly (P < 0.05) less toxic to fish than copper sulfate in all waters except that of the lowest total alkalinity. Highly significant (P < 0.01) linear relationships were found between LC50 values for copper from copper sulfate and pH, log [total alkalinity], and log [total hardness], of test waters. These results cast doubt on the validity of the formula commonly used to calculate practical copper sulfate pond treatment rates, which is based upon a simple linear relationship between application rate and total alkalinity.

A review of feeding practices, growth and nutritional physiology in larvae of the catfishes Clarias gariepinus and Clarias batrachus.

Abstract: A comparative study of larval growth in the different species of the genus Clarias in different regions revealed that in spite of strong differences in egg and larval size, the growth potential was quite similar. Differences in growth between species and regions were strongly correlated with the applied feeding strategy, the applied growth parameter and period of measuring. To evaluate feeding strategies, standardized procedures for measuring growth are needed. Recalculating the results of the mentioned study according to these standardized procedures revealed that both in India and Indonesia, the growth rate of C. batrachus larvae was too low. This is probably due to low feeding levels in India and premature weaning in Indonesia. The basic biology and nutritional physiology of the larvae of C. gariepinus have been studied extensively. At the start of exogenous feeding, the larvae have an advanced digestive system with a functional pancreas, liver and nutrient absorption capabilities, but lack a functional stomach. The advanced digestive system is further exemplified by the development of the enzymatic complex. Probably because of the rapid development of the digestive system, feeding live food organisms is mostly practiced for a few days only and is soon replaced by wet and/or dry diets. It is hypothesized that the requirement of live food or specific larval diets during the first days of exogenous feeding is related to the absence of pepsin digestion during this period. Further optimization of the feeding strategies should focus on this conclusion.

Nutritional factors affecting stress resistance in the larval mahimahi Coryphaena hippurus

Abstract: Recent improvements in enriching Artemia make mahimahi culture possible without using copepods. Mahimahi survive better when cultured copepods Euterpina acutifrons are used, especially when the larvae are under stresses such as high stocking density, cold weather, or the rigors of metamorphosis. This study looked at some differences between copepods and enriched Artemia.This study tested stress resistance by holding postlarval (PL) mahimahi out of water in a hand net for varying periods of time. Recovery from this stress shock was higher in PLs whose diet was higher in docosahexaenoic acid (DHA). DHA appeared to play an important role in stress resistance. High eicosapentaenoate (EPA) or high HUFA did not confer stress resistance when DHA levels were low. Copepods contained higher levels of many essential amino acids in addition to higher levels of DHA compared with enriched brine shrimp. Larvae sickened by disease appeared to lose fat, including DHA, but they conserved DHA relative to other fatty acids. Even when sick, mahimahi larvae fed a copepod diet resisted stress better than larvae fed an enriched brine shrimp diet. Optimal Artemia enrichment levels of DHA for mahimahi have not been reached and this may explain why it has been difficult for others to raise this fish consistently. E. acutifrons is relatively easy to culture, but may not be practical for commercial hatcheries, due to low yield (less than 10 g per 100 L per week).

Seasonal Changes in Water Quality in Commercial Channel Catfish Ponds in Mississippi

Abstract: Selected water quality variables were measured at monthly intervals for 1 yr in 10 commercial channel catfish ponds in northwest Mississippi. Temporal changes in most variables appeared to be related to seasonal periodicity of phytoplankton abundance. Phytoplankton standing crops and total organic matter were highest in summer months when primary production was favored by warm water temperatures, high solar irradiance, and large inputs of nutrients resulting from high summer fish feed allowances. As day length, water temperature, and feed inputs decreased in autumn and winter, phytoplankton abundance and organic matter concentrations decreased. Seasonal changes in total nitrogen and total phosphorus concentrations were similar to phytoplankton abundance because much of the total nitrogen and phosphorus was contained within phytoplankton cells. Contrasting to the seasonal trend for total nitrogen, concentrations of dissolved inorganic nitrogen were lowest in the summer and highest in the cooler months. Rapid assimilation by phytoplankton served to maintain relatively low concentrations of dissolved inorganic nitrogen during the summer despite highest nitrogen loading rates during that period. Low water temperatures and generally less favorable conditions for phytoplankton growth decreased rates of nitrogen assimilation in the winter and ammonia, nitrite, and nitrate accumulated. Soluble reactive phosphorus concentrations were low throughout the year because physico-chemical processes, such as precipitation and adsorption to bottom muds acted to continually remove inorganic phosphorus from the water column.

Response of Penaeus vannamei to Dietary Calcium, Phosphorus and Calcium: Phosphorus Ratio

Abstract: Two experiments, consisting of 7 d conditioning periods and 33 d feeding trials, were conducted to evaluate the response of juvenile Penaeus vannamei to dietary calcium, phosphorus and the effects of the calcium to phosphorus ratio on growth and tissue mineralization. In both experiments, the main effects, calcium and phosphorus, and their interaction significantly affected growth and survival of the shrimp. In the absence of supplemental calcium, the basal diet containing 0.35% phosphorus was adequate to maintain good growth and survival of shrimp. In the presence of replete phosphorus, supplementation of 1.0 and 2.0% calcium to the diet depressed survival and did not appear to increase the nutritive value of the diet, indicating that a dietary calcium supplement is not required under these conditions. In the presence of 1.0 and 2.0% supplemental calcium, supplementation of 0.5–1.0% phosphorus and 1.0–2.0% phosphorus, respectively, were required to maintain normal growth of the shrimp. At high levels of calcium supplementation, poor growth was observed at the levels of phosphorus supplementation evaluated. Although the calcium and phosphorus content of the hepatopancreas and the carapace responded to dietary supplementation, there was no clear correlation of tissue mineralization to shrimp growth.

A Comprehensive Program for the Evaluation of Artificial Diets

Abstract: The evaluation of artificial diets for marine fish larvae involves much more than feeding trials. Information on the diet in the water column (buoyancy, leaching, etc.), the digestive capabilities and requirements of the larvae, and the fate and uptake of the diet inside the larval digestive tract are all necessary to the understanding of the success or failure of a given artificial diet. Interdisciplinary teams of investigators are required to fully evaluate and formulate artificial diets.

Reproductive Quality Evaluation of Male Penueus stylirostris from a Grow-Out Pond

Abstract: Several male Penucus stylirostris were selected from a 3 ha commercial earthen pond and were individually evaluated for reproductive performance. Indicators measured were compound spermatophore weight, sperm count, and sperm abnormalities. It was found that spermatophore quality was significantly better for 30–40 g shrimp than for 20–30 g shrimp (P < 0.05). The higher frequency of abnormalities measured in younger males and the inverse relationship between abnormalities and sperm count indicate that the vas deferens could be the tissue responsible for producing highly abnormal immature semen. It is proposed that male maturation has at least three independently controlled levels of organization: testes maturation, vas deferens maturation, and spermatophore synthesis. The individual evaluation showed that each male followed a particular response in reproductive quality. Changes in spermatophore weight were not an indicator of sperm density within spermatophores. Male reproductive tract degenerative syndrome (MRTDS) and male reproductive system melanization (MRSM) did not develop in any shrimp during these experiments.

Sperm Quality of Pond‐Reared and Wild‐Caught Penaeus monodon in Thailand

Abstract: Sperm quality, as determined by visual examination and by reaction with “egg-water” was not significantly different (P > 0.05) for sperm obtained by electro-ejaculation from ablated or non-ablated pond-reared Penaeus monodon. Nor was sperm quality different between pond-reared and wild-caught prawns. Normal sperm, determined by appearance, ranged from 17.1 to 21.0%, while reactive sperm ranged from 1.5 to 3.0%. There were, however, significant correlations (P 60% for newly inseminated females to near zero after 30 days post-insemination, indicating spermatophore depletion and/or deteriorated sperm quality during spermatophore storage in the thelycum. The findings of the present study indicate that electro-ejaculation and artificial insemination are relatively simple and practical methods for improving captive reproduction performance of closed-thelycum prawns such as P. monodon, and that pond-reared and wild-caught males produced sperm of similar quality.

Evaluation of the Dietary Zinc Requirement of Penaeus vannamei and Effects of Phytic Acid on Zinc and Phosphorus Bioavailability

Abstract: Experiments were conducted to determine the dietary zinc requirement of Penaeus vannomri and evaluate the effects of phytate on zinc bioavailability. Prior to initiation of the growth trial, 20-day-old P. vonnamei postlarvae (mean weight 0.0032 g) were fed a casein-gelatin based semi-purified diet lacking zinc supplementation but containing 18 mg Zn/kg diet for one week. Subsequently, juveniles (mean weight 0.058 g) were fed one of seven diets containing either supplemental zinc (0, 15, 30, 60 mg/kg diet) without phytate or supplemental zinc (0, 60, 200 mg/kg diet) with 1.5% phytate for 33 days. Weight gain was greatest in shrimp fed 15 mg supplemental Zn/kg diet. In the absence of dietary phytate, zinc concentrations in the hepatopancreas of shrimp were maximized when zinc was supplemented at levels greater than or equal to 15 mg Zn/kg diet (33 mg total Zn/ kg). Supplementation of 1.5% phytate to the diet did not have a significant effect on growth or zinc concentrations in the carapace; however, it did depress zinc levels in the hepatopancreas. Supplementation of 200 mg Zn/kg diet was required to overcome the depressed bioavailability of zinc caused by the presence of dietary phytate and return zinc levels of the hepatopancreas to that observed when phytate was not present. Based on apparent digestibility values phytate phosphorus was unavailable to the shrimp and the presence of phytate depressed the bioavailability of phosphorus and zinc.

Development and Deterioration of Spermatophores in Pond‐Reared Penaeus vannamei

Abstract: Spermatophore deterioration in pond-reared Penaeus vannamei was studied, and spermatophore quality was evaluated and improved. Sperm production of males collected from grow-out ponds was increased by two techniques: eyestalk ablation using a fresh frozen maturation diet (13% body weight); and laboratory culture using a diet of the formulated feed Nicovita Plus (3% body weight/ d) and frozen squid (2%). Findings are complementary to previous reports that eyestalk ablation improves quality of spermatophores in young (25.7 g) males. The timing of eyestalk ablation for activation of the endocrine mechanism, leading to improved spermatophore quality was also explored. After eyestalk ablation, performed between postmolt and intermolt stages, 26 g males required a minimum of three spermatophore regenerations or 42 d to significantly increase spermatophore size and sperm count. On the other hand, the laboratory culture (2.5 mo) technique improved the quality of spermatophores in successive regenerations for non-ablated males. In the present study, subadult P. vannamei produced spermatophores which, if not transferred or manually ejaculated, gradually deteriorated (successive stages are described), while a new compound spermatophore was being synthesized.

Preliminary Comparisons of the Native Penaeus setiferus and Pacific P. vannamei White Shrimp for Pond Culture in South Carolina, USA

Abstract: Two pond experiments were conducted at the Waddell Mariculture Center to compare production characteristics of the native Penaeus setiferus and Pacific P. vannamei white shrimp in South Carolina. In 1985, 7–9 day old postlarval P. setiferus were stocked in one 0.1 and one 0.25 ha ponds, while P. vannamei of the same age were stocked in one 0.1 and one 0.25 ha ponds, while P. vannamei of the same age were stocked in one 0.1, one 0.25, and one 0.5 ha ponds. Both species were stocked at 12 shrimp/m2. The shrimp were fed a 25% protein commercial food and harvested by draining after 147 d. Sarvival in all ponds was > go%, but growth and production of the P. setiferus were considerably lower than values obtained for P. vannamei: 12.8 g and 1,555 kg/ha/crop for P. satiferus versus 19.7 g and 2,477 kg/ha/crop for P. vannamei. In 1989, duplicate 0.1 ha ponds were stocked with P. setiferus and P. vannamei at 60 shrimp/m2, and two additional 0.1 ha ponds were stocked with P. setiferus at 40/m2. The P. setiferus postlarvae were produced at the Waddell Center from captive-reared and wild South Carolina brood stock. Rearing procedures involved paddlewheel aeration (10 hp/ha), regular water exchange (averaging 16–21%/d in all ponds), and use of a 40% protein feed. Due to the availability of postlarvae, the various treatments were stocked at different times. Both P. setiferus treatments were reared for 145 d, while the P. vannamei were reared for 165 d. P. setiferus at the 40/m2 density attained mean size, survival, and standing crop biomass at harvest of 13.5 g, 97.5% and 5,259 kg/ha/crop, respectively. The 60/m2P. setiferus treatment was stocked 2 wk earlier and yielded 15.2 g mean weight, 87.5% survival, and 7,995 kg/ha/crop at harvest. The P. vannamei 60/m2 treatment, which was stocked 3 wk earlier than any of the P. setiferus, produced mean size, survival and standing crop biomass at harvest of 17.1 g, 69.5% and 7,187 kg/ha/crop. Both survival and production levels would have been higher had not one replicate experienced a partial mortality due to a feeding accident. The 1989 study yielded what is thought to be the highest production levels yet achieved with P. setiferus in pond culture. These results suggest that P. setiferus may be a viable alternative to P. vannamei for intensive cultivation in the continental U.S. when P. vannamei are unavailable. Further evaluation of this potential is needed.

Experimental and Practical Diet Evaluations with Juvenile Hybrid Striped Bass1

Abstract: Culture of hybrid striped bass has been expanding in the United States and further growth has been predicted, however, several problem areas exist, including a lack of nutritional information. This series of studies offered reciprocal cross juvenile hybrids several of the commercially available feeds and several different types of purified experimental diets. Weight gain and feed efficiency of fish fed the commercially available feeds formulated to meet the general requirements of salmonids were better than fish fed feeds formulated to meet the nutritional requirements of catfish. Experimental diets containing casein as the primary protein source were unpalatable regardless of the level of fish oil added (6 or 12%) but were accepted if 10% menhaden fish meal was added. Addition of lower levels of fish meal resulted in decreasing degrees of acceptance. Thus, the minimum level of fish meal that elicited a feeding response appeared to be between 510% of the dry diet. A crystalline amino acid test diet was palatable, and weight gain of fish fed that diet was 65–91% of the weight gain recorded for fish fed the positive control diets. Addition of L-arginine, L-methionine or L-cystine to a purified diet containing casein did not result in dietary acceptance. Whole-body proximate composition offish revealed a general trend toward increased lipid levels with increasing levels of dietary lipid. All fish exhibited microvessicular hepatopathy, regardless of diet fed. Hepatocytes contained both glycogen and lipid in the cytoplasm.

An Intensive Approach to Atlantic Halibut Fry Production

Abstract: The larval stage is regarded to be the main bottleneck of halibut production. Halibut eggs were obtained from captive broodstock both by stripping and by natural spawning. Artificial photoperiods were used to increase the total spawning season. Yolk sac larvae are presently produced either in small stagnant units or in large flow through systems. A major consideration is to avoid stress of the larvae, caused by mechanical disturbances of the larvae and by high bacterial load or high ammonia levels in the water. The experiments showed that halibut larvae began to ingest algae earlier than rotifers Brachionus sp. Supplementation of algae to first feeding tanks resulted in enhanced survival and growth rate of the larvae. Both rotifers and Artemia can be enriched with very high levels of highly unsaturated n-3 fatty acids (n-3 HUFA). Enriched live feed, containing high levels of n-3 HUFA and total lipids, enhanced both survival and growth of the halibut larvae. The highest growth rates were obtained with wild zooplankton and addition of algae, but enriched cultivated feed combined with algae resulted in growth of the same magnitude as with wild zooplankton.

Riboflavin Requirement of Fingerling Red Hybrid Tilapia Grown in Seawater

Abstract: Red hybrid tilapia Oreochromis mossambicus×O. niloticus fingerlings were fed diets containing 0, 2.5, 5.0, 10.0, 20.0 and 40.0 mg/kg, and 0, 2.5, 5.0, 7.5, 10.0 and 20.0 mg/kg of riboflavin in separate 8 and 12 wk feeding studies, respectively. The dietary riboflavin level required to provide maximum growth and survival, and prevent deficiency symptoms in red hybrid tilapia fingerlings was found to be approximately 5 mg/kg of diet. In both trials, fish fed the diet devoid of supplemental riboflavin exhibited anorexia, reduced growth and nervous symptoms after 4–6 wk. Mortality began to occur after the sixth week. None of these abnormalities were observed during the first 6 wk in fish fed the riboflavin supplemented diets. However, by the seventh week, fish fed the diet supplemented with 2.5 mg/kg of riboflavin showed reduced appetite and growth rate. In both experiments, short body dwarfism was observed during week 8 for fish fed the diet without riboflavin supplementation. In experiment 1, fish fed the riboflavin-deficient diet had lens cataracts at week 8. This deficiency sign was not observed in experiment 2. Histological studies of liver, kidney, spleen, lateral muscle, gill and gastrointestinal tract revealed no major histopathological changes.

Evaluation of Distillers Dried Grains with Solubles as an Ingredient in Diets for Pond Culture of the Freshwater Prawn Macrobrachium rosenbergii

Abstract: Distillers dried grains with solubles (DDGS) were evaluated as an ingredient in practical diets for pond culture of the freshwater prawn Macrobrachium rosenbergii. Juvenile prawns averaging 0.66 ± 0.47 g were stocked into nine 0.02 ha ponds at 19,760/ha. Three isonitrogenous diets (29% crude protein) containing 0, 20, or 40% DDGS were fed to shrimp in triplicate ponds. Average yield, survival, individual weight, and feed conversion did not differ significantly (P > 0.05) among treatments. When averaged over the three diets, results were: yield, 833 kg/ha; survival, 75%; individual weight, 57 B; and feed conversion, 3.1. It appears that DDGS is a suitable ingredient for use in practical diets for freshwater prawns at levels of up to 40% of the total formulation, when prawns are stocked at the densities used in this study.

Recent Advances in Nutrition of Penaeus monodon

Abstract: This paper provides a brief summary of information on recent advances in the nutrition of Penaeus monodon. The nutritional requirements of P. monodon have been little known despite its importance in aquaculture. Recent findings indicate a noticeable difference between some important nutrient requirements of P. monodon and P. japonicus, the most studied shrimp species. For example, the thiamin requirement for P. monodon was estimated to be 14 mg/kg diet, while for P. japonicus it is 60-120 mg/kg diet for juveniles and 40-80 mg/kg diet for larvae. The same contrast was also observed in the requirements of riboflavin (22.5 mg/kg in juvenile P. monodon vs. 80 mg/kg in larval P. japonicus), niacin (6.4 mg/kg vs. 400 mg/kg) and vitamin C (2,000-2,500 mg/kg vs. 10,000 mg/kg). Research efforts to understand the lack of ability for shrimp to effectively use dietary crystalline amino acids have resulted in the development of a microencapsulated amino acid that can be assimilated by P. monodon which is incapable of utilizing the essential amino acid in crystalline form. This development enables the quantification of requirements of the amino acid and other essential amino acids for shrimp. A study using cellulose-acetate-phthalate encapsulated arginine indicated that the arginine requirement of postlarval P. monodon is 5.47 g/100 g protein (2.50 g/100 g diet). Other aspects concerning the importance of digestive enzymes, dietary requirements of protein, carbohydrate, lipid and vitamin, energy and larval feeding for P. monodon were reviewed.

Growth Trial with the American Oyster Crassostrea virginica Using Shrimp Pond Water as Feed

Abstract: This study was conducted to quantify the potential of Crassostrea virginica biculture using marine shrimp pond water. It was envisioned that this biculhre could avoid cost and reliability problems associated with the mass production of algae as oyster feed. Such problems contributed to the failure of previous attempts to commercialize oyster culture. Oysters were reared in each of two flow through 310 L tanks receiving shrimp pond water from selected commercial semi-intensive shrimp ponds. In each tank, pond water was delivered to the upper trays and flowed downward through each of two seven tray stacks. For both tanks, mean oyster growth rate (2 g/wk) and survival (79%) from seed (0.04 g) to market size (55.0 g) compared favorably with previous reports and for the first time approximated the growth projected in a 1968 engineering study by American Cyanamid (Calbo et al. 1968). Oyster growth within and between tanks indicated a relationship between biomass and exchange rates. During a 65 d controlled monitoring period mean oyster growth rates of 3.7 g/wk were achieved in upper trays of both tanks. Data are provided to estimate optimum pond water flow rate and oyster biomass relationships. The prospects for shrimp and bivalve co-culture appear promising.

Control of Reproduction of the Shrimp Penaeus kerathurus Held in Captivity

Abstract: The control of the reproductive cycle of the shrimp Penueus kerathurus, held in captivity from early juvenile stages without eyestalk ablation, was attempted in two sets of experimental conditions during two successive years. In the first set of experiments, light regime, sex ratio and presence of sand substratum were assessed in relation to ovarian maturation and successful mating. Examination of thelyca obtained from cast exoskeletons showed that 40–82% successful mating had taken place. A sex ratio of 2:l female/male gave a higher percentage of fertilized females than a ratio of 1:l. The induction to full ovarian development was observed for every treatment except the tank without sand substrate, where no mated females were observed. In the second set of experiments, the role of diet, in particular the role played by a polychaete Nereis diversicolor, was assessed as a nutritive stimulator to induce maturation and spawning. With the same purpose, a parallel experiment in smaller aquaria was also conducted to assess the relative importance of mussel, squid, ragworm and crab and four composite diets consisting of two or three of the said food organisms. Nereis worm seemed to have a determinant role on the induction of shrimp ovarian maturation and spawning. The possible role of its fatty acids on shrimp reproduction is discussed. The experimental results suggest the possibility for extended control of the reproductive cycle of P. kerathurus in a controlled environment provided that proper food is available.