Pregled akvakulture u Izraelu

Due to the severe water constrictions in Israel (60% of the country is a desert with less than 80 mm rainfall per year), the aquaculture practices in the country have had to rely on innovative methods designed to overcome the water shortage. These include: the extended use of saline water not suitable for other agricultural crops yet very suitable for fish culture; dual use of irrigation reservoirs for fish culture and intensive production ponds in which the fish yields per cubic meter of water are extremely high. Pelleted fish feeds of high quality, especially designed for the different cultured fish species are used in all the ponds. The main edible fish cultured in freshwater are tilapia and carp. In the marine water sea bream and European sea bass are the main cultured species. In addition there is a growing sector of ornamental fish these include cold water fish such as koi carp and warm water tropical species such as guppies. Bird predation of fish is major problem and a number of methods are utilized in order to overcome the problem. These include various scaring devices such as: noise makers, scarecrows of different shapes and colors, self propelled small airplanes in the shape of predatory birds and nets

Perifiton kao delimična zamena komercijalne hrane u organskom gajenju tilapije u Izraelu

Cena hrane čini jednu od najvećih stavki u tekućim troškovima proizvodnje u akvakulturi. Usled potrebe za korišćenjem samo organskih sastojaka, cena koncentrovane hrane za uzgoj organske ribe je izuzetno visoka. Tokom petogodišnjeg perioda rađeni su eksperimenti kako bi se ispitala mogućnost upotrebe različitih supstrata za indukciju rasta perifitona koji bi služio kao prirodna hrana za tilapiju različite veličine, od mlađi do naprednih uzrasnih stadijuma. Kao supstrat, procenjivan je različit poljoprivredni otpad - plastične cevi, najloni i mreže. Različiti supstrati dali su različite prinose perifitona u zavisnosti od njihove površine (glatka ili hrapava) i boje. Rezultati rasta pokazali su da je ušteda hrane od 40% u naprednim fazama rasta dovela do svega 10% redukcije stope rasta tilapije u odnosu na kontrolna jezera, dok je u mladičnjaku moguće smanjiti količinu koncentrovane hrane do 50% bez ograničenja rasta riba. Ovo smanjenje količine hrane od 30-40% dovelo je do poboljšanja koeficijenta konverzije hrane (FCR) od barem 30% u jezerima sa perifitonom (45% u mladičnjacima). Zaključak: upotreba supstrata hrapavih površina za indukciju rasta perifitona može pomoći u recikliranju otpadnih materijala i značajno redukovati troškove hrane u organskoj akvakulturi

Color Enhancement in the Ornamental Dwarf Cichlid Microgeophagus ramirezi by Addition of Plant Carotenoids to the Fish Diet

The present research examined the effects of adding carotenoids from oleoresin paprika to fish feeds for ornamental dwarf cichlid, Microgeophagus ramirezi. The growth rate, survival, carotenoid accumulation level, and color intensity were evaluated. Post larvae and near-adult (three months old) fish were tested to determine when carotenoids are better assimilated. The addition of carotenoids had no effect on the growth rate or survival in either life stage, however, they had a clear effect on color enhancement. After 45 days, near-adult fish that consumed carotenoid-supplemented diets at 60, 120, or 240 mg/kg had significantly higher levels of carotenoids (72.19±4.55, 84.81±5.29, and 86.55±4.50 μg/g dry matter, respectively) than con- trol fish (33.69±1.06 μg/g), with no significant differences between treatments. After 75 days, post larvae that consumed 240 mg/kg carotenoids accumulated significantly more carotenoids in their body (59.34±3.93 μg/g dry matter) than fish that consumed only 60 mg/kg carotenoids (40.53±2.37 μg/g dry matter) or no supplemental carotenoids (29.18 μg/g dry matter). Visual examination revealed a strong correlation between level of pigment accumulation and color appearance in the fish. Results indicate that addition of 60 mg oleoresin paprika per kg diet is sufficient to obtain good coloration in M. ramirezi

Effects of addition of a bird repellent to fish diets on their growth and bioaccumulation

The effects of adding the nonlethal bird repellent methyl anthranilate (MA), at levels of 100 and 1000 mg/kg, to fish feed on the bioaccumulation and growth of juvenile (10 g) hybrid striped bass (Morone chrysops x M. saxatilis) and juvenile (1g) African cichlid fish Aulonocara jacobfreibergi were investigated under laboratory conditions. The bird repellent did not have any effect on the fish growth or survival over a period of 6 weeks. MA residues at low levels of 11.2 ± 2.6 mg/g were found in lipophili tissues (liver) of MA-fed fish. Control fish, which had no MA added to their diet, had a much lower level of 0.6 ± 0.3 mg/g MA in their liver. Fish muscle was found to contain negligible MA residues, while the outer body surface mucus did not contain any MA. Following a 6-week depuration period, during which the previously MA-fed hybrid striped bass were fed a feed to which no MA was added, the levels of MA residues detected were reduced by one order of magnitude

Comparison of Periphyton Grown on Different Substrates as Food for Organic Tilapia Culture

Regulations regarding organic tilapia culture result in increased feed costs. To reduce such costs, experiments were conducted to enhance the natural production of periphyton, on which tilapia feed. Strips of substrates of different textures and colors were placed in the water column of tilapia culture ponds to induce periphyton growth. Some strips were placed in cages to protect them from fish grazing and some where placed in the open pond, accessible to the fish. Periphyton development was evaluated by the contents of chlorophyll, dry matter (DM), and ash free dry matter (organic matter) and by an autotrophic index. The first experiment tested growth on substrates of different textures including natural (palm leaves) and artificial (agricultural nets, plastic surfaces) materials. The second experiment tested the effect of different colored nets. The differences between periphyton grown in cages and in the open pond indicate that tilapia grazed on the periphyton. Palm leaves decomposed too quickly to be of practical use in large- scale aquaculture. Periphytic material seemed to be more easily dislodged from smooth plastic substrates than from rough nets, changing the structure of the residual attached periphyton. Growth was greater on nets with a fine mesh (5.3-9.6 mg/cm2 DM) than with a coarse mesh (3.7- 4.0 mg/cm2 DM) or on smooth plastic surfaces (1.4-2.6 mg/cm2 DM). The color of the substrate did not affect the chlorophyll content of periphyton but did affect its dry and organic matter con- tent. The white substrate had 40% more dry matter (11.5 vs 7.9-8.2 mg/cm2) and 50% more ash free dry matter (2.1 vs 1.4 mg/cm2) than the blue and black substrates

Evaluation of organic tilapia culture in periphyton-based ponds

The introduction of hard surfaces in the water column to induce the growth of biofilms and peri- phyton on these surfaces is a method used to increase natural productivity of the water body and food for cultured aquatic organisms. In periphyton-based systems in Africa and Asia, substrate introduction and consequent periphyton development positively affected water quality and pro- duction of the target species. In Israel, this technology is being evaluated in the culture of organ- ically produced tilapia. Among other restrictions imposed by organic standards, fish stocking densities must be low and only organic feeds and manures must be supplied. Organic pelleted feeds cost twice as much as regular aquaculture feeds. Since feed constitutes the major pro- duction expense, economic viability is hampered by using costly organic feeds. An experiment was performed at the Dor Aquaculture Station to explore methods of improving natural food pro- duction for tilapia and reducing added feeds. Submerged plastic surfaces equivalent to 40% of the pond surface area were immersed in polyculture ponds containing 85% hybrid tilapia (Oreochromis niloticus x O. aureus), together with a reduction of 40% of the amount of pelleted feed. The treatment improved nitrification and saved 40% of the feed costs, with only a 10% reduction in the tilapia growth rate and yield. These results indicate that periphyton-based aqua- culture is an appropriate technology for reducing production costs and allowing economically viable organic tilapia production

Rearing White Grouper (Epinephelus aeneus) in Low Salinity Water: Effects of Dietary Salt Supplementation

The white grouper (Epinephelus aeneus) is native to the Mediterranean Sea and the eastern Atlantic Ocean. It is an important species in fisheries of this region, having high market value. Our project of white grouper domestication in brackish water systems aims at developing culture methods for local conditions. The study evaluates the potential of culturing white grouper in low salinity water and the effect of an NaCl-enriched diet on this species. The results of a three-month culture period, conducted at a commercial farm, demonstrate that white grouper can grow in 3 ppt salinity and that 3% dietary salt supplementation can significantly improve its growth. However, the overall growth performance in low salinity was below expected for this species and further research is needed to develop culture practices for white grouper

Transcript quantification of intestinal neutral amino acids and oligopeptides transporters in European sea bass (Dicentrarchus labrax) reared in fresh water and fed fish and plant protein sources.

Oligopeptides and free amino acids are absorbed along the intestinal tract by specialized membrane transporter proteins. Di- and tri-peptides are transported via the H+/coupled peptide transporter (PEPT1), which is located in the brush border membrane of intestinal epithelial cells. Free amino acids are absorbed by a variety of Na+- dependent and independent membrane transporters, frequently referred to as \u201csystems\u201d. Among the amino acid transporting proteins, the neutral amino acid transporter SLC6A19, also called system B(0) neutral amino acid transporter AT1 (B0AT1), is an integral plasma membrane protein responsible for the uptake of a broad range of neutral amino acids across the apical membrane of enterocytes and renal cells. In humans, the B0 system is associated with a severe neutral aminoaciduria known as Hartnup disorder. The objective of the present study was to examine the effect of diets with descending fish meal (FM) inclusion levels and the addition of salt to the diet containing the lowest FM level on growth performances, food conversion ratio, and intestinal SLC6A19 and PEPT1 transcript levels, in freshwater adapted European sea bass (Dicentrarchus labrax). We have firstly isolated by molecular cloning and sequencing a fulllength cDNA representing the neutral aminoacid transporter SLC6A19 in sea bass. The cDNA sequence was deposited in GenBank database (accession no. KC812315). The 12 transmembrane domains and the de novo prediction of the three-dimensional structure of SLC6A19 protein (634 amino acids) are presented. We then analysed diet-induced changes in the mRNA copies of SLC6A19 and PEPT1 genes in different portions of sea bass intestine using realtime RT-PCR. Sea bass were fed for 6 weeks on different diets, with ascending levels of fat or descending levels of FM, which was replaced with vegetable meal. The salt-enriched diet was prepared by adding 3% NaCl to the diet containing 10% FM. SLC6A19 mRNAs in anterior and posterior intestine of sea bass were not modulated by dietary protein sources and salt supplementation. Conversely, including salt in the diet containing low FM percentage, upregulated the mRNA copies of PEPT1 in hindgut. Fish growth correlated positively with the content of FM in the diets. Interestingly, the addition of salt to the diet containing 10% FM improved food intake, as well as specific growth rate and food conversion ratio

Culture Of The Australian Red-Claw Crayfish (Cherax Quadricarinatus) In Israel Crayfish Incorporation Into Intensive Tilapia Production Units

This study tested the suitability of the Australian red-claw crayfish Cherax quadricarinatus for rear- ing in an intensive culture system as a supplement to Oreochromis niloticus. Fish were grown in twelve 5.5 m3 tanks at high density (33/m3) for 133 days, alone or with crayfish at two stocking den- sities (10/m2 and 20/m2) with added shelters or with crayfish at the lower density (10/m2) without shelters. Tilapia survival ranged 90.3-95.0% with no significant differences among treatments. The growth rate of the tilapia raised with crayfish (2.05 g/day) was significantly higher than that of tilapia grown alone (1.88 g/day) probably because the fish were feeding on part of the crayfish pellets. Among treatments, there were no significant differences in fish yield. Crayfish survival was extremely low in the ‘no shelter’ treatment (2.9±2.7%) but reasonable (approximately 60%) when raised with shelters. The growth rate of the crayfish raised with shelters was significantly higher at the lower density (0.21 g/day) than at the higher density (0.18 g/day). Further research is needed on rearing tilapia and crayfish to market size in intensive systems, to establish the economic prof- itability of this culture strategy