Natural Food Organisms Research Articles

Potentiality of natural live food organisms in shrimp culture: A review

The aquaculture industry is growing quickly due to increased fish consumption and a decline in wild fish catch. About half of the world's seafood demand for human consumption is now met by farmed seafood. The aquafeed market is expanding along with the aquaculture sector. Some of the elements in shrimp feed are derived from terrestrial plants and low-value forage fishes (fish meal). It is impossible to produce more fish meals since doing so would harm the ocean's environment and sustainability. The reduction in shrimp feed cost can also be done by introducing low-cost, environment-friendly ingredients in shrimp feed formulation. Therefore, new and ecologically friendly shrimp (Litopenaeus vannamei) feed component sources must be created. Live food organisms are a preferable option for this since they provide a variety of essential amino acids and beneficial triglycerides like fat, vitamins, and colors in their cell metabolites. Microalgae biomasses also represent feasible ingredients for shrimp feed sources. Their distinctive variety of bioactive chemicals can enhance color and pellet quality, act as a bulk element in shrimp feed, and boost the viability of farmed species. Live food organisms have a great economic potential since they have the highest biomass productivity of all photosynthetic organisms. In addition to giving farmers and exporters a better choice for feeding their fish, the availability of on-grown live food would also open up the prospect of improving the performance and quality of the fish and shrimp through bioencapsulation. This review study examines the possibility of generating natural food biomass as a component in shrimp feed.

Effect of natural food consumption on the first phase of pirarucu grow-out in ponds and cages

ABSTRACT Pirarucu, Arapaima gigas is a fish species of great social and economic importance in the Amazon region, where they are often farmed in earthen ponds. Intensive cage aquaculture has been growing in Brazil, which could be an alternative means to farm pirarucu, reducing costs and increasing productivity. We evaluated the contribution of natural food organisms in semi-intensive (ponds) and intensive (cages) production systems, and their effect on pirarucu growth and economic performance during the first phase of grow-out. Four ponds (300 m2) and four cages (4.0 m³) were stocked, respectively, with 120 (0.4 fish m-²) and 160 (40 fish m-³) juvenile pirarucu (28.03 ± 6.34 g, 11.75 ± 0.80 cm). The study was conducted for 105 days and fish were fed with commercial feed. Fish growth and plankton intake were evaluated every two weeks. Survival rate, standard length, weight gain and final weight were higher in fish reared in earthen ponds than in cages. Feed conversion of fish kept in ponds was lower (0.96 ± 0.06) than in cages (1.20 ± 0.11). The consumption of natural food organisms was observed, despite artificial feed being fed in both systems. The relative abundance of zooplankton and insects in stomachs was directly proportional to fish weight gain in ponds, and inversely proportional in cages. Higher economic efficiency rate and lower average production cost were calculated for earthen ponds. Our results indicate that the cost-benefit of the first phase grow-out of A. gigas is better in earthen ponds.

Assessment of Tilapia–Freshwater Prawn Co-Culture Schemes in Tanks and Lake-Based Cages for Increased Farm Production

The technical viability of tilapia (I-ExCEL strain Nile or red) and giant freshwater prawn (GFP) co-culture in cages-within-tanks was evaluated while appropriate feeding protocols for tilapia-GFP co-culture in cages in a eutrophic lake were determined. Specifically, production parameters in all test species grown for five months in tank co-culture (where only tilapias were fed) were compared, while the best feeding protocol from among the following treatments: (a) Tfed—fed tilapias; (b) GFPfed—fed prawns and (c) T-GFPfed—both species fed, were defined. I-ExCEL Nile tilapias grew faster in tank co-culture whether reared singly or otherwise. However, red tilapia-GFP tank co-culture gave the best results considering key production traits in all test species (red tilapia —2.52%/day specific growth rate or SGR, 83.3% survival; GFP—1.17%/day SGR, 72.85% survival). Lake-based co-culture was technically feasible at stocking densities of 12.5/m2 for tilapia and 2.4 to 4/m2 for prawns even when only tilapias were fed; prawns grew to desired marketable sizes by thriving mainly on detritus and natural food organisms in the lake. However, further refinements can still be made to optimise the co-culture schemes to make them more sustainable and provide artisanal fish farmers options in increasing farm yields through multi-species aquaculture.

EFFECT OF SUGARCANE BAGASSE AND SUPPLEMENTARY FEED ON EGG AND SPERM QUALITY OF CATFISH, HETEROPNEUSTES FOSSILIS (BLOCH)

In modern aquaculture, feed is one of the major components affecting the cost of production. In most traditional aquaculture practices, herbivorous or omnivorous species have been preferred as they feed on natural food organisms, the growth of which can be enhanced through fertilization and water management (Pillay, 2001). But carnivorous species generally need a high protein diet and are therefore, considered to be more expensive to produce, even though the costs will depend largely on local availability and price of the required feed stuffs. To compensate the feeding costs, most carnivorous species command higher market prices. Such species generally have greater export markets and therefore, attract substantial investments. In the present study, investigations were carried out to evaluate the egg and sperm quality of the catfish, Heteropneustes fossilis in sugarcane bagasse substrate medium. This species was selected due to its ability to adapt in fresh and brackish waters with very low oxygen and could grow under generally poor environmental conditions, make these fishes extremely valuable for small and large scale rural fish farming (Pillay, 2001). Substrate-based farming practices are considered viable low-cost technologies as they help in sustainable aquaculture production (Dharmaraj et al., 2002). Sugarcane bagasse is the fibrous residue remaining after sugarcane stalks are crushed to extract their juice, generated in large quantities and is currently used as a renewable resource in the manufacture of pulp and paper products and building materials.

Influence of a Feed Additive in the Carp Diet on its Exterior Parameters

During fish farming, significant attention should be paid not only to the quantity, but also to the quality of marketable carp, primarily its physiological condition and high adaptive plasticity. Recently, increasing importance is attached to fish farming by industrial methods using various types of feed. A characteristic feature is the almost complete absence of natural food organisms. Significant success has been achieved in the creation of various starter compound feeds that can replace live feed when the larvae switch to exogenous nutrition [1]. During the development of artificial rations, attention was paid to the balance of basic structural elements of nutrition and, to a lesser extent, to various biologically active substances. For the majority of farmed fish, the need for protein and essential amino acids, fat and certain fatty acids, carbon and minerals has been established, on the basis of which, starter and production feeds, as well as various vitamin and mineral premixes, were developed [2]. However, natural food contains a wider range of biologically active components that are the regulators of many metabolic processes of body. Therefore, live food in fish nutrition, even in small proportion, can supplement the energy components of artificial feed and thereby significantly increase the balance of the diet [3].
 Keywords: aquaculture, probiotic, exterior, aquatic organisms, bacteria, fatness ratio, diet

Insect attractants and plant biomass as natural food complements in pond culture of stock chub (Squalius cephalus)

The chub, Squalius cephalus (L.), is an important stocking fish in European rivers. This study investigates sustainable measures for culturing chub in earthen ponds. Two novel treatments were applied to enhance utilisation of natural pond food resources: yellow plates used as insect attractants (YIT) and plant biomass supplementation (PB) as a substrate supporting the development of natural food organisms. While no significant differences were recorded for most environmental variables, average macrozoobenthos biomass was significantly higher (p < 0.05) in the control (61.51 g.m−2) compared with PB (29.3 g.m−2) and YIT (36.8 g.m−2). However, fish from YIT ponds had significantly higher (p < 0.05) mean body weight gain (34.7 g) and SGR (1.60 g.day−1) compared to the PB (28.65 g and 1.50 g.day−1) or control (25.64g and 1.43 g.day−1) ponds. Diet analysis indicated a higher amount of animal food (mainly zooplankton, zoobenthos, terrestrial insects and fish) in YIT and PB treatments, while a higher amount of plant (mainly macrophytes) and emergency food (detritus) was observed in the control ponds. Differences in diet were reflected in the fatty acid profile of fish from different treatments, with YIT fish having significantly (p < 0.05) higher n-3 PUFA, n-3 HUFA and n-3/n-6 ratio, compared to PB fish and controls. Our results confirm that YIT use in pond aquaculture significantly enhances the role of natural food resources in the diet of cultured chub, thereby contributing to its sustainable production.

Variasi Pemberian Bioton terhadap Kelimpahan Moina sp.

Fish after the egg-bag absorption phase require external feeding, in the form of fresh natural food organisms, such as phytoplankton, zooplankton, or aquatic insect larvae. These natural food organisms are limited in number. The business of mass production of natural food is still limited to several types originating from marine or brackish waters. For this type of natural freshwater fish feed, it is still limited to experimental materials. This study aims to determine the best dosage of Bioton liquid fertilizer added to the maintenance medium to the rate of population abundance of Moina sp. The research was conducted at the Wet Laboratory of Fisheries Cultivation Study Program, Faculty of Agriculture, Ahmad Yani University, Banjarmasin. The method used in this study was an experiment with a completely randomized design of 4 treatments and 3 replications. The treatment applied was 4 treatments with 3 repetitions, with the following treatment of Bioton liquid fertilizer: A = 5 ml / 3 l water, B = 10 ml / 3 l water, C = 15 ml / 3 l water, and D = without Bioton liquid fertilizer (control). The results showed that the abundance of Moina sp in treatment A = 4,333 ind / l, B = 3,633 ind / l, C = 2,700 ind / l and D = 3,034 ind / l. The ANOVA test results of all treatments were very significantly different, so accept H1, namely giving bioton with different doses had a significant effect on the abundance of Moina sp. The results of the LSD test of all treatments had a very significant difference in abundance, except for treatment D to treatment C which was significantly different, with the best treatment being a dose of 5 ml / 3 l of water (treatment A).

Raising Fish in a Purpose‐Built Conservation Aquaculture Facility Using Conservation Aquaculture Management

AbstractThe naturalized conservation aquaculture unit (refugium) at Los Lunas Silvery Minnow Refugium is the first purpose‐built, large‐scale conservation aquaculture mesocosm. The refugium is 0.2 ha in area, with 0.11 ha of interconnected water habitats, including a stream with sand bars, five ponds, shelves, marshes, attached bars, and overbank areas that can be inundated to create floodplains. The key components of conservation aquaculture management in the refugium are as follows: (1) no artificial feed is used, so that the fish develop the foraging strategies that will be needed in the wild and do not develop maladaptive behaviors associated with feeding; (2) the production of natural food organisms is based on indirect fertilization; (3) fish are subjected to managed predation, so that when stocked they are not behaviorally naïve; and (4) low stocking rates are used to mimic population densities in the wild. Results from 6 years of management and the lessons learned about facility design and conservation aquaculture management are discussed.

Living under the State and Storms: The History of Blood Cockle Aquaculture in Bandon Bay, Thailand

(ProQuest: ... denotes non-US-ASCII text omitted.)IntroductionCoastal aquaculture around Bandon Bay, in Surat Thani Province of Southern Thailand, developed in the context of state development projects implemented as part of the government's anti-Communism policies. The government further promoted intensive aquaculture when neighboring countries declared a 200-nautical-mile exclusive economic zone off their coasts at the end of the 1970s.11 Since then, the Bay has become the main aquaculture area of Thailand and, according to 2000-04 aquaculture production statistics, one of the most concentrated aquaculture areas in Southeast Asia (Campbell 2011, 31). The main products of the Bay can be divided into two groups according to the method and area of cultivation. The first is intensive cultivation of marine shrimp, or prawns, in ponds constructed on land along the riversides and coast. Production depends on these controlled and artificial settings in order to ensure a stable supply for the export market. The second is extensive aquaculture in natural marine settings that relies not only on the local climate and water quality but also on natural food organisms (ibid., 6). In Bandon Bay, this extensive aquaculture includes the cultivation of blood cockles (hoi kraeng, Anadara nodifera, Anadaragranosa), oysters (hoi takrom, hoi nangrom), and green mussels (hoi maeng phu).Pond cultivation of shrimp accounted for more than half of the total aquaculture area in Bandon Bay during 2000-10 (Fig. 1). Blood cockle production was ranked second after shrimp.2) Unlike shrimp cultivation, which is an export-oriented industry, blood cockles are produced mainly for the domestic market. Although Surat Thani has a significant share of the domestic market, blood cockles are not a major product for the province,3 and the government does not consider it significant because it is not an export product. As cockle cultivation relies heavily on local climate and water quality, cockle farmers have to adapt farm management to minimize the risks from climate variability and pollu tion. They have expanded their farms 3 kilometers out from the shore into areas outside the zone legally approved by the government. This expansion has challenged the marine usage rights of poor local fishermen, as rich local fishermen are able to illegally convert common marine areas into their own private assets thanks to their political influence. As a result, conflicts between artisanal fishermen and blood cockle farmers over the use of resources have repeatedly erupted in recent years, not only in Bandon Bay but also in the Bay of Pattani and Phetchaburi Province.Studies on the development of coastal aquaculture in Thailand focus primarily on conflicts over coastal resource management. Thai academicians pay attention to the ways in which sociocultural norms of local communities can enhance the roles of local actors in dealing with resource conflicts. This analysis framework gained popularity as a tool in case studies of water and forest resource management in Northern Thailand. As for studies on coastal resources, most emphasize case studies of local fishery communities in the lower southern parts of Thailand, including the east (Gulf of Thailand) and west (Andaman Sea) sides. Such communities are found in Songkhla, Pattani, and Phagnga (Anan 2000; Chalita 2000; Watthana 2001; Lertchai et al. 2003; Lertchai and Narit 2009).Among studies on coastal aquaculture, studies on coastal shrimp farming are extraordinarily ubiquitous. That is because shrimp is the most commonly farmed seafood in coastal Thailand, and shrimp has been the export item that triggered the most widespread attention on the standardization of food safety when compared with other kinds of coastal aquaculture. Notably, most studies on coastal shrimp farming emphasize sustainability. Since the origination of shrimp farming in the early 1970s and throughout the next four decades, shrimp farmers have employed various cultivation strategies and technical innovations to expand farms and products. …

Study of phytoplankton in a natural hypersaline lagoon in a desert area (Bardawil Lagoon in Northern Sinai, Egypt)

Bardawil is a shallow hypersaline lagoon, with salinity ranging between 38.18 and 62.40 PSU. It is a source of good quality fish and wildlife. The phytoplankton was evaluated seasonally (summer 2013 to spring 2014), at 12 stations. A total of 186 taxa from 95 genera and seven classes, namely, Bacillariophyceae, Dinophyceae, Chlorophyceae, Cyanobacteria, Euglenophyceae, Rhodophyceae and Chrysophyceae were recorded. The phytoplankton community was dominated by Bacillariophyceae followed by Dinophyceae. The Shannon–Wiener Diversity Index (1.75–3.30) classified Bardawil Lagoon as being a not stressed environment. Differences in the phytoplankton community structure and abundance between previous results and the present study showed significant changes with the change in salinity. Seasonal differences in the quantitative and qualitative composition of the phytoplankton communities in the different sites were marked. The phytoplankton annual succession was characterized. No sign of eutrophication was observed, and most of the dinoflagellate species detected have been described as harmful or able to occur at high biomass. The study showed that Bardawil water is still oligotrophic, free of contaminants, so we suggest the need to add fertilizers to accelerate the production of natural food organisms to increase fish and crustacean production. Before the addition of any fertilizer, it must dig two or three canals to facilitate exchange of water between the Mediterranean Sea and the lagoon to prevent undesirable harmful algae bloom.

Supplemental effects of mixed ingredients and rice bran on the growth performance, survival and yield of Nile tilapia, Oreochromis niloticus reared in fertilized earthen ponds.

Unaffordability of commercial feeds to semi-intensive Nile tilapia, Oreochromis niloticus farmers has led to reliance on supplemental feeding and fertilization for nutrition of their fish without a scientific basis. This study compared the growth, survival, condition factor and yield performance of O.niloticus fed on mixed ingredients (MI) and rice bran alone (RB) diets reared in fertilized earthen ponds in small scale farmers’ ponds. The study also determined phytoplankton composition, biomass and abundance in the experimental ponds. Quadruplicate ponds were stocked with O. niloticus and African sharptooth catfish, Clarias gariepinus at a stocking ratio of 1:3. The initial mean weights of O. niloticus and C. gariepinus were 14.62 ± 0.61 and 20.34 ± 1.44 g respectively. The fish were fed on MI and RB diets with protein content of 184.74 and 126.06 g kg−1 respectively for 270 days. The results showed that growth performance, survival rate and condition factor of O.niloticus were not affected by either feeding with MI or RB diet (p > 0.05). Moreover, there were no significant differences obtained in phytoplankton biomass and abundance in O.niloticus ponds fed on the two diets (p > 0.05). Furthermore, feeding O.niloticus either on MI or RB diet did not affect the net and gross fish yields (p > 0.05). The study revealed that the use of either MI or RB diet does not significantly affect the performance of O.niloticus cultured in semi-intensive earthen ponds where natural food organisms are an integral part of the culture system. Rice bran could be used for semi-intensive culture of O.niloticus in fertilized ponds to boost the production based on its availability and low cost.

Chemical profiling with modeling differentiates Ictalurid catfish produced in fertilized and feeding ponds

Abstract Elemental analysis (Al, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, P, S, Se, and Zn) of fillets of channel catfish Ictalurus punctatus and hybrid catfish (♀ I. punctatus × ♂ blue catfish Ictalurus furcatus) from fertilized ponds and of hybrid catfish that received feed was performed using an inductively coupled plasma atomic emission spectrometry (ICP-AES). Fillets of samples of hybrid and channel catfish in fertilized ponds did not differ in composition for most of the elements analyzed. Multivariate statistical methods including principal component analysis (PCA), canonical discriminant analysis (CDA) and k-nearest-neighbor analysis were used to separate Ictalurid catfish to the two culture methods based on chemical composition. The three methods each demonstrated that fillets from fish that received feed could be differentiated from fillets of fish cultured in fertilized ponds. Fish from fertilized ponds rely on natural food organisms in the same manner as wild-caught fish. This study demonstrated the potential of chemical profiling combined with multivariate statistical methods for verifying method of production – aquaculture versus wild-caught.

Growth, survival and proximate body composition of Labeo rohita larvae fed artificial food and natural food organisms under laboratory condition

This investigation was carried out to study the effect of different live feed and dry feed on growth and survival of Labeo rohita at a stocking density of 20 larvae per trough having 10 L of water. The increase in weights and lengths were used as measures of growth. The duration of the experiment was 30 days. Seven dietary treatments were tested viz. Artificial diet with 45% protein (LFr1), rotifers like Asplanchna and Brachionus (LFr2), wild zooplankton (LFr3), bioenriched zooplankton (raised on Chlorella , cod liver oil and vitamin C) (LFr4), Artemia (LFr5), Chironomous (LFr6) and Oligochaetes (LFr7). Among the different treatments, larvae fed with diet LFr4 resulted in the maximum body weight gain (BWG) (13.18 ± 0.13 mg) which was significantly (P < 0.05) higher than all the treatments which followed the order of preference as: LFr5 (12.31 ± 0.10 mg), LFr3 (9.75 ± 0.08 mg), LFr2 (7.85 ± 0.10 mg), LFr7 (6.49 ± 0.15 mg), LFr6 (5.66 ± 0.13 mg) and LFr1 (4.99 ± 0.14 mg). The diet LFr4 recorded maximum survivability (92.0 ± 2.0%). All the values recorded for the BWG and survival were found to be significantly different (P < 0.05) among others. Protein and lipid content of the prawn after the treatment was found to be highest for LFr5 and LFr4, respectively.

Effect of feeding regimes on growth and survival of Clarias gariepinus larvae: replacement of Artemia by a commercial feed

TheAfrican cat¢sh, Clarias gariepinus (Burchell1822) is one of the most important species currently being farmed. Clarias gariepinus is a native species of tropical and subtropical fresh waters. It has been widely farmed in heated waters outside its natural range (Hecht & Appelbaum 1987), mainly in intensive culture in recirculating systems. The rapid growth even at high density, ability to breathe air and to withstand poor water quality and low food requirement make C. gariepinus an excellent ¢sh for aquaculture. In recirculating systems, larval rearing is the bottleneck in C. gariepinus production (Verreth 1994), although great progress has been made on the development of larval diets (Hecht, Ollermann & Verheust 1996). Larvae of African cat¢sh are generally weaned with natural food organisms that seem to be a prerequisite for the early larval rearing, and Artemia is often described as a reference diet in larval nutrition studies. Using natural food is costly, time consuming and not always available for the ¢sh breeder. Production of live food also needs adapted structures. Recently, an alternative to Artemia live food was developed for the marine hatchery market. This new generation of starter feed is described as more digestible, metabolizable and with better formulation (Gemma micro s , Skretting, commercial prospectus). The objective of the present investigation was to assess the possibility to replace partially or totally live food (Artemia nauplii) by a commercial arti¢cial food. Larvae of C. gariepinus were obtained by arti¢cial reproduction with captive breeders reared in the Aquaculture Research and Education Centre of the University of Lie' ge. Larvae were reared in 50-L aquaria in a recirculating system at 28.0 0.1 1C, pH57.6 0.2, with constant aeration (O255 0.8 ppm) and renewal rate (0.5 Lmin ). Concentrations of total ammonia and nitrites were 0.68 0.26 and 0.22 0.26mgL . The experiment was conducted in two phases: during the ¢rst 13 days post ¢rst feeding (feeding begin 48 h post hatching), larvae were fed with or without A. nauplii andwith diierent feed (six feeding regimes in duplicate, Table 1) at 500 ¢sh/50-L aquaria. Two commercial larval feed were used: ‘Gemma micro s ’ Skretting (particles size 150^300 mm), a marine larval feed or ‘Lucky Star s ’ (particles size 150^300 mm), a freshwater larval feed. Compositions are presented in Table 2. Fish were fed ad libitum six times a day from 09:00 to 17:00 hours.When necessary, excess feed was removed from the aquaria at the end of the day. In the second phase, from D13 to D32, larvae weaned with the diierent regimes were reared at 200 ¢sh/50-L aquaria and fed with the same feed (Lucky Star s , particles size 300^500 mm) to evaluate the eiect of ¢rst feeding regimes on growth and survival after the weaning period. At the end of each phase, biomass was measured and 50 ¢sh were individually weighed. Speci¢c growth rate SGR, food conversion ratio FCR and survival rate were calculated according to the formula: SGR5100 (lnW2 lnW1) (t2 t1) whereW2 andW1 are mean body weight (g) at day t2 and t1, FCR5C (¢nal biomass initial biomass) 1 where C is total food Aquaculture Research, 2010, 1^4 doi:10.1111/j.1365-2109.2010.02709.x

Growth, Survival and Proximate Body Composition of M. dayanum Larvae Fed Artificial Food and Natural Food Organisms under Laboratory Conditions

Growth, Survival and Proximate Body Composition of M. dayanum Larvae Fed Artificial Food and Natural Food Organisms under Laboratory Conditions

Growth performance of blue shrimp, Litopenaeus stylirostris in self-cleaning microcosm tanks

Outdoor microcosm tanks were used to grow the penaeid blue shrimp, Litopenaeus stylirostris, in Brunei Darussalam. The tanks were cylindrical, free standing fiber glass tanks of 1827 L water holding capacity and had a self-cleaning mechanism. In three eight-week feeding trials, juvenile shrimp of 0.9–4.3 g were stocked at a density of 28 shrimp/m 2. At the end of each trial, survival rates exceeded 80%. Growth rates ranged from 1.19 to 2.46 g/week. Water quality remained stable and within suitable ranges for L. stylirostris growth in all trials. The tanks had algae and bacterial floc developing within a few days of starting the trials. Fourteen commercial shrimp feeds, each containing more than 40% crude protein, were tested in the trials. In spite of the presence of natural food organisms, significant feed-related differences among treatments were found in each trial. In conclusion, microcosm tanks support excellent growth and survival of L. stylirostris and are appropriate for conducting trials to evaluate feeds for pond growout.

Effect of green and clear water and lipid source on survival, growth and biochemical composition of Pacific white shrimp Litopenaeus vannamei

Despite the shrimp ability to obtain additional nutrients from food organisms endogenously produced within the green water system has been suggested as one of the causes for the better performance of Pacific white shrimp reared in green water in comparison with clear water, the nutritional components responsible for these effects have yet to be determined. The present study aims to understand the importance of natural food organisms in zero-water exchange systems as source of essential fatty acids for the Pacific white shrimp Litopenaeus vannamei. Five treatments were tested: two conducted in mesocosms systems with shrimp-fed diets containing either fish oil (FO) or olive oil, and another three conducted in clear water with shrimp-fed diets containing either olive oil, a docosahexaenoic acid (DHA)-rich oil or an arachidonic acid (ARA)-rich oil. The presence of higher levels of fatty acids 16:1n-7, 17:1, 20:4n-6, 20:3n-3 and 22:5n-6, characteristic of floc lipids, in shrimp reared in mesocosms denoted their assimilation from the floc. Substitution of FO by olive oil in diets for shrimp reared in mesocosms did not affect growth or survival. Survival and growth of shrimp reared in mesocosms was better than those reared in clear water and fed an olive oil diet, whereas DHA or ARA enrichment of non-fish oil (NFO) diet improved survival of shrimp reared in clear water. Higher survival rate, triglyceride and DHA content in whole body and eyes of shrimp fed a DHA-rich diet suggests that under these conditions, in clear water, it is necessary to include at least 4.8 g kg )1 DHA in diet dry weight. ARA enrichment seemed to negatively affect growth. The nutritional contribution of the floc to shrimp in mesocosm culture reduces or eliminates the need for a dietary source of FO and illustrates the importance of DHA and ARA to enhance shrimp survival in clear water conditions.

Evaluation of Decapsulated Artemia Cysts in Hatchery Diets for Channel Catfish Ictalurus punctatus Fry and Effects on Subsequent Fingerling Production

Abstract.— Two 10‐d hatchery growth trials were conducted to determine if differences in growth, body composition, and survival existed among catfish fry Ictalurus punctatus fed a diet of 100% catfish‐starter (CS) or CS in combination with decapsulated Artemia cysts (DAC) at 25%, 50%, or 75% of diet weight. A 120–d production trial was undertaken immediately following the first hatchery trial to evaluate the effects of diet on production characteristics (survival, length, weight, feed conversion ratio, and total yield) of fingerling catfish produced from hatchery‐raised fry. Fry fed diets containing DAC weighed 61–98% more (P &lt; 0.05) than fry fed only CS. The size differential of DAC‐fed fry was maintained through 120 d of growth in simulated nursery ponds (0.001‐ha earthen‐bottom pools). The increased growth of fry fed DAC might have been related to differences in dietary lipid content, amino acid composition, or digestibility of CS and DAC. Body weights of fingerlings produced under simulated production conditions from fry fed hatchery diets containing 50% and 75% DAC were 17% and 25% higher, respectively, 130 d post‐hatch, than fingerlings produced from fry fed only CS. In addition, the total yield of fingerlings produced from fry fed 75% DAC was 17% greater that that of fingerlings produced from fry fed only CS. The increased performance of fingerlings produced from DAC‐fed fry could have resulted from their larger size at stocking, since larger fry might be capable of capturing natural food organisms and ingesting prepared diets more effectively than smaller fish. CS‐DAC diet combinations could be used to increase weight gain of hatchery‐raised fry if the cost‐benefit ratio of adding DAC to the standard hatchery diet warrants its use.

Forage-Based Feeding in Commercial Red Claw Ponds in Ecuador

Red claw crayfish, Cherax quadricarinatus, are perhaps the first tropical species of crayfish to be cultured commercially. Culture traits and high market value could allow semi-intensive culture. Feeding strategies used in extensive crayfish ponds in temperate climates may not be the most appropriate for semi-intensive culture systems where year-round growth is possible. The following study was conducted to evaluate differences between using a pellet-based system versus a pellet-plus-forage-based system. The study was conducted in 14 0.3-ha ponds on a commercial farm in Ecuador. Juvenile red claw (1-2 g) were stocked into all ponds at a rate of 4/m2. All ponds received pelleted shrimp rations at a rate of 3% per day. Seven ponds also received dried hay at a rate of 100 kg/ha/mo during the 3-month study. At harvest, red claw weights were similar (30-34 g), but survivals were significantly higher in ponds receiving pellets and hay (65%) than in ponds receiving pellets only (50%). Yields in pellet-fed ponds averaged 594 kg/ha, while red claw receiving pellets plus forage averaged 889 kg/ha. The addition of dried forage was thought to provide a larger variety of natural food organisms throughout a greater area of the pond bottom and provided additional substrate for dispersal and hiding. Addition of grasses from outside the pond is recommended over production of grasses grown within the pond.

Functional response and particle size selection of Halteria cf. grandinella, a common freshwater oligotrichous ciliate

In laboratory experiments, we studied the growth and feeding characteristics of Halte- ria cf. grandinella, a common and widespread oligotrichous ciliate in freshwater plankton. Particle- size-dependent feeding rates were measured with fluorescent latex micropheres (0.22 to 4.23 µm diameter) and natural food organisms (bacteria, Synechococcus sp., Chlorella minutissima) in short- term feeding experiments. H. cf. grandinella ingested all but the smallest (0.22 µm) particles offered and demonstrated a concentration dependent type-2 functional response. Maximum clearance rates were obtained with 2.76 µm latex beads (0.6 µl h -1 ). Clearance rates declined for smaller and larger particle sizes but even with the suboptimal size classes, 0.47 and 1 µm, high maximal ingestion rates were measured (19 and 13 beads ciliate -1 min -1 , respectively). The maximum clearance rates for bac- teria and algae were close to those of similar sized latex beads, and no discrimination of particles based on properties other than size could be detected. The physiological state of the ciliates did not seem to have an impact on the relative pattern of the particle-size-dependent functional response curves, but the absolute feeding rates decreased nearly 10-fold after prolonged starvation. The experiments demonstrated that this small filter-feeding ciliate is an omnivorous species which is able to efficiently exploit the planktonic prey size spectrum from 0.5 to 5 µm, covering heterotrophic and autotrophic pico- and nanoplankton in the diet.