Trash Fish Feed Research Articles

The effect of giving commercial feed, beloso trash fish (Saurida tumbil), kurisi trash fish (Nemipterus nematophorus), and mixed trash fish on growth of cantang grouper (Epinephelus fuscoguttatus-lanceolatus) in floating net cage

An experiment was conducted to observe the effect of commercial feeding, and trash fish feed supplement on cantang grouper fish growth in floating net cages at Situbondo, Indonesia. The method used in this experiment was designed with 4 treatments and 3 replications. Samples (26.49 ± 0.81 cm) were a stocking density of400 fish/cage and maintenance for 30 days. The treatments used were P0;commercial pellets, P1;100% beloso trash fish (Saurida tumbil), P2; 100% kurisi trash fish (Nemipterus nematophorus) and P3; mixed wasted fish; 50% beloso trash fish + 50% kurisi trash fish, with four replicates. The best treatment result is that P0 quantitatively has significant effect on feed growth, survival, and efficiency compared to other treatments; SGR (0.5618%), SR (85%), FCR (3.69), and EPP (27.08%) compared to other treatments. The best treatment result is that P0 quantitatively has significant effect feed on growth, survival, and efficiency feed utilization of cantang grouper (E. fuscoguttatus-lanceolatus) compared to other treatments.

The Effect of Diet on Ovarian Development and Nutritional Tissue Composition of Portunus trituberculatus

This study investigated the effects of feeding trash fish (TF), formulated diet (FD), and mixed diets (MD) on ovarian development, fattening performance, and nutritional quality of P. trituberculatus. Formulated diet treatment resulted in lower gonadosomatic index, hepatosomatic index, meat yield, and total edible yield than the other treatments. It also showed lower protein (7.88%), lipid, and ash content in hepatopancreas and muscle, compared to the other treatments. Different diets significantly affected the contents of C16:0, C18:1n9, C18:2n6, C18:3n3 and C20:5n3 of hepatopancreas. FD treatment resulted in lower essential amino acids and non-essential amino acid contents in the muscle compared to TF and MD treatments. The highest and the lowest essential amino acids scores were found in the TF and FD treatments, respectively. In conclusion, these results indicated that FD is not suitable and requires further development for sub-adult crabs, while MD would be the recommended for fattening female P. trituberculatus.

Protein Profile and Ammonia Excretion of Mud Crab Scylla serrata with Recirculation System.

Mud crabs have a high level of cannibalism so as to increase the growth of maximum mud crab and reduce the level of stress it is necessary environmental manipulation that supports it as a container maintenance with dark and bright conditions. This study aimed to determine the optimum container condition for survival and growth of mud crab by protein profile and ammonia excretion. Mud crab derived from the fisherman Pasuruan East Java with initial weight 45-65 g kept in containers (60×40×30 cm3) in recirculation systems for 42 days with feeding trash fish restricted by 5% twice daily. The study was conducted with two treatments and three replications of bright containers and dark containers. Several stress indicators including protein retention, total serum protein, ammonia secretion were determined and growth performance of the mud crab was also evaluated. The dark container resulted in optimum condition for mud crab indicated by the highest survival 30±6%, specific growth rate 0.44±0.02%/day, absolute longevity 1.29±0.03 cm, absolute weight growth 10.5±0.31 g, protein retention 15.59±0.46% and feed conversion ratio 6.38±0.27. This study concluded that better growth performance was observed in dark container for nursery of mud crabs.

IMPACT OF NURSERY USING DIFFERENT PHYSICAL FILTRATION SYSTEM ON HEMOLYMPH GLUCOSE LEVEL AND SURVIVAL RATE OF SPINY LOBSTER JUVENILE Panulirus homarus

The problems in culture of early juvenile phase of spiny lobster Panulirus homarus is low survival rate of the seed. One of strategies to improve production is using filtration system during nursery of spiny lobster. The aim of this study to evaluate differentation of physical filtration system on responsse stress and survival rate of juvenile P. homarus. Experimental design of this study consisted of four treatments and two replications. The treatments were using flow through system without protein skimmer and filter (K), filtration system with protein skimmer (SK), filtration system with top filter (F) and filtration system with combinations of protein skimmer and top filter (SKF). P. homarus with initial weight 0.18+0.01 g were cultured for 60 days with density 250 lobster/tank. During maintenance, P. homarus were fed trash fish with feeding rate 20% of body weight. Parameters of glucose hemolymph were evaluated to determine stress response. Stress response was determined at day 0, 6, 20 and 60. Parameters of survival rate were determined at the end of experiment. The result showed that the treatment of filtration system with combination of protein skimmer and top filter (SKF) decreased stress responsse by decreasing glucose hemolymph of juvenile P. homarus during maintenance. Survival rate also higher (P<0.05) in treatment SKF (33.2%) than other treatments. It is concluded that SKF was the best physical filtration system for juvenile period of spiny lobster P. homarus Keywords: filtration system, glucose hemolymph, spiny lobster, survival rate

A comparison study on flesh quality of large yellow croaker (Larimichthys croceus) cultured with three different modes

To compare the flesh quality of large yellow croaker cultured with three different modes, enclosure culture (EC), cage culture with feeding trash fish (CCF) and cage culture with feeding formula diet (CCD), thirty six fish individuals of EC (484.6 ± 79.8 g), CCF (432.7 ± 87.9 g) and CCD (416.9 ± 49.5 g) were sampled to measure body color, flesh water holding capacity, flesh proximate composition, amino acids and fatty acids composition, and collagen and inosinic acid contents. The analysis showed that there was no significant difference in the yellowness of skin and the contents of crude protein and inosinic acid between CCD and EC (P >0.05), and the two modes showed higher values than CCF (P 0.05). EC and CCD had higher contents of collagen, free AA and lower drip loss than CC (P < 0.05). In polyunsaturated fatty acids, EC showed significantly higher levels of C20:5n-3 and C22:6n-3 than CCF and CCD (P < 0.05), but CCD had significantly higher C18:2n-6 than CCF and EC (P < 0.05). In conclusion, the flesh quality of CCD fish is similar to EC fish, and these two modes have better flesh quality than CCF.

Penetapan Kebutuhan Harian Pakan Ikan Rucah untuk Penggemukan Kepiting Bakau Scylla paramamosain di Keramba Jaring Dasar

&lt;strong&gt;Determination of Daily Requirement of Trash Fish Feed to Fatten The Mangrove Crab Scylla paramamosain in Bottom Net Cages.&lt;/strong&gt; Mangrove crab fattening is part of the crab farming activities that attracts the interests of the farmers due to its relatively short period, i.e. 14–21 days per cycle. Trash fish is a natural feed for Mangrove crabs that is easily available at an affordable price. Scientific information on the daily requirement of trash fish feed to fatten the Mangrove crabs is still scarce. The accessable scientific information on the amount of daily feeding is still limited to the rearing of the crabs. Hence, the scientific study on the daily requirement of trash fish feed for crab fattening needs to be done. Probolinggo is one of the producing districts for Mangrove crabs and is a potential area for development of crab aquaculture. Therefore, Probolinggo was chosen as the site of this research. Crab samples utilized had a carapace width of 8–13 cm and a weight of 115–500 g. Crabs were reared in bottom net cages measuring 5 x 5 m2 with a density of 16 crabs/cage and the sex ratio of 1: 1. The study consisted of 4 treatments with 3 repetitions. The daily feeding percentages given were 10, 15, 20, and 25% of the body weight of the crabs. The parameters observed during the 13 days of experiment were growth, survival rate, and the percentage of already fatter crabs. The results showed that the daily feed ration of trash fish, as much as 10% dan 15% of the body weight of the crab, gave the best yield for crab fattening. The survival rate obtained was 70% of the initial density of 0.64 crabs/m2, with a total weight gain of 14% during the study. &lt;br /&gt;&lt;br /&gt;

Enhancements of non-specific immune response in Mugil cephlus by using seaweed extract protection against Vibrio alginolyticus (BRTR07)

Objective: To focus on the growth rate and feed utilization of fish by using trash fish feeds supplement with marine seaweeds. Methods: Selected seaweed was extracted using hot-water and its extract was mixed with trash fish feed at different concentrations (0.5%, 1% and 2% for 1-30 days) and the non- specific immune response in fish was studied and challenged with Vibrio alginolyticus at 1 × 10 6 CFU/fish. The hot-water extract of seaweeds was analysed by gas chromatography-mass spectrometry. Results: The average body weight (5.320 ± 0.018), percent weight gain (227.66 ± 0.28), specific growth rate (2.080 ± 0.015), hepatosomatic index (1.197 ± 0.00) and viscerosomatic index (4.421 ± 0.150) were significantly increased in the fish feed with seaweed containing 5% of Sargassum wightii (S. wightii) when compared with other seaweeds and control diet. Hot- water extract of S. wightii (1%) was significantly enhanced the immune response in fish when compared with other diets (0.5% and 2%). S. wightii showed good immunostimulation properties. Gas chromatography-mass spectrometry result showed that the hot-water extract of S. wightii seaweed contained fatty acids. Conclusions: Trash fish feed will reduce the production cost and also provide evidence that aqueous leaf extract of S. wightii (1%) was added to a formulated fish diet which could activate the non-specific immune response and disease resistance against Vibrio alginolyticus in Mugil

Effect of Selected Diets on the Growth and Survival of Snakehead Fish (Channa striatus) Fry

Twenty-five days feeding trial was conducted to evaluate the growth and survival of Channa striatus fry fed with three types of fresh foods (bloodworm, trash fish and Acetes shrimps). Ten fry were stocked in each aquarium (46x46x37 cm) and fed ad libitum twice a day (1000 and 1700 h). All treatments were triplicate. The fry fed trash fish showed a significantly (p<0.05) higher weight gain percentage (376.50±20.74%) than those fed with Acetes shrimp (233.05±10.18%) and bloodworm (199.08±17.25%). The final mean total lengths of fry fed with trash fish, bloodworm and Acetes shrimps were 7.91±0.23, 7.28±0.23 and 7.21±0.17 cm, respectively. Fry fed with trash fish also showed the best Specific Growth Rate (SGR) value (6.24±0.17% day-1) followed by Acetes shrimp (4.81±0.12% day-1) and bloodworm (4.33±0.22% day-1). The best Food Conversion Ratio (FCR) value (3.63±0.27) was found among fish fed with trash fish compared to those fed Acetes shrimp (7.41±0.88) and bloodworm (11.48±1.51). It could be concluded that trash fish was an excellent feed for C. striatus fry in term of growth, weight gain and FCR.

Pengaruh Pemberian Kombinasi Pakan Ikan Rucah dan Pakan Buatan (Pelet) terhadap Pertumbuhan dan Laju Sintasan Rajungan (Portunus pelagicus)

The aim of this experiment was to find out the data and information of effect on feeding of combination of trash fish and pellet to the growth and survival rate of swimming crabs ( Portunus pelagicus ). The research was conducted in the research station of Research Institute for Coastal Aquaculture, Maros, South Sulawesi for 40 days. Nine aquaria were used in this research and the dimention were 60 x 40 x 40 cm. Experimental disign used the Complete Randomized Design, The treatments were applied of trash fish and artificial feed (pellet) i.e. A; 100% trash fish ( Clupea sp), B; 100% artificial feed (pellet), and C; 50% trash fish + 50% pellet, with three replicates, respectively, Crablet were applied average size of 5,2 + 0,2 mm in charapace width and 0,04 + 0,02 g in body weigth. Feeding were conducted of three times a day, with dosage 15 % of total body weight a day. During the experiment, the determined parameters were body weight, charapace width, and survival rate. The result showed that artificial feed/pellet of 42% protein contain could be used as feed in swimming crabs rearing and not significant different on the growth of charapace width, body weight and survival rate (P>0.05) with the other treatment.

Upaya Penurunan Tingkat Kanibalisme Udang Windu (Penaeus monodon) dengan Penambahan Dosis Suplemasi TriptofanYang Berbeda

The aim of this experiment was to find out the suitable dosage of tryptophan mixed in diet of trash fish were fed and to decrease canibalism levels of tiger prawn ( Penaeus monodon ) reared in the aquarium. The research was conducted in research station of Research Institute for Brackishwater Aquaculture Maranak, Maros South Sulawesi for 28 days.Twelve aquaria were used of this research and the dimention of 60 x 40 x 40 cm. Tiger prawn seed of post larva of 35 th from hatchery were used to this research and the dimention of 1,4 ± 0.1 cm body length and 0,01 ± 0.01 g body weight. Twentyfive pieces of tiger prawn seed were spreaded on the each aquaria. The treatments were applied of dosage of tryptophan were mixed in the trash fish ( Sardinella sp) as much as (A): 0 % of biomass total, (B): 0,5 %, (C): 1,0 % and (D): 1,5 % of biomass total with three replicates respectively. Variables monitored growth of body weigth, canibalism levels, survival rate of twentyfive tiger prawn seed and water quality. Experimental design used complate randomized design. During of rearing were fed trash fish with frequency of twice a days of dosage 15 % of total body weight. The result showed that the tiger prawn seed fed the diet with additional 0,5 - 1,5 % tryptophan had significantly lower (P<0.05) cannibalisms compared to the tiger prawn seed feed the control diet. The tiger prawn seed fed the diet with additional 1,5 % tryptophan had significantly higher (P<0.05) survival rate compared to the crablet fed the control diet. However, there were not significantly different specific growth rate among the treaments. Based on this result that additional 0,5 - 1,5 % tryptophan could be decrease cannibalisms of tiger prawn seed during experiment.

Growth and Survival of Indian Salmon Eleutheronema tetradactylum (Shaw, 1804) in Brackish Water Pond

This study was conducted to assess the growth performance and survival rate of a commercially important finfish Eleutheronema tetradactylum in 100 m-2 of sandy clay brackish water earthen ponds. Wild 36.14 g of E. tetradactylum juveniles were stocked at 0.5 individuals m-2 and cultured for 45 days by feeding trash Muraenesox sp. (pike eel) at 12 h intervals. Average body weight of E. tetradactylum was found 75±5.6 g for treatment ponds and 65±3.57 g for control ponds at the end of experiment. Feed Conversion Ratio (FCR) was 2.3 with the survival rate of 70-80% at the end of the culture in the experimental culture ponds. The results of the present study suggest that the production of four finger thread fin could still be increased up to the marketable size if it is done for 5-6 months culture period by feeding trash fish.

Reproductive performance, egg and larval quality and egg fatty acid composition of hatchery-reared Spotted Babylon (Babylonia areolata) broodstock fed natural and formulated diets under hatchery conditions.

A 120 day feeding trial was conducted to evaluate the reproductive performance, egg and larval quality and egg fatty acid composition in Spotted Babylon (Babylonia areolata) broodstock fed with natural food (fresh meat of carangid fish, Seleroidesleptolepis,) and one of four experimental formulated diets containing 5 or 15% of dietary lipid from either tuna oil or a mixture of tuna oil and soybean oil (6:4) labeled as 5% TO, 15% TO, 5% MO and 15% MO respectively. Using trash fish as a control food resulted is the lowest levels of in 20:5 n - 3, 22:6 n - 3 and 20:4 n - 6 fatty acids compared to those of all experimental diets, while the highest contents of those fatty acids were found in the 5% TO diet. Statistically significant differences in reproductive performance between dietary treatments with the best reproductive performance were found only for females fed the 5% TO diets, but egg and larval quality showed no variability among females fed trash fish and all experimental diets. No significant differences were observed in the survival duration in the starvation tolerance test for females fed trash fish or any of the experimental diets. However, the fatty acid profile of egg capsules was significantly affected by the dietary treatments. The levels of major fatty acids (20:5 n - 3, 22:6 n - 3 and 20:4 n - 6) in egg capsules produced from females fed diets containing 5% tuna oil (5% TO) was significantly higher than those from females fed trash fish or other experimental diets. We therefore conclude that formulated diets resulted in successful reproduction and high essential fatty acids in egg capsules comparable to the use of trash fish. Key words: Babylonia areolata, broodstock diet, reproductive performance, egg and larvae quality.

Persistent Halogenated Hydrocarbons in Fish Feeds Manufactured in South China

Persistent halogenated hydrocarbons (PHHs), including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs), in fish feeds (including trash fish and compound feed) manufactured in South China, were analyzed. PHHs were ubiquitous in fish feeds, with the concentrations of OCPs, PBDEs, and PCBs at the upper, mid, and lower levels of the global range. Trash fish generally contained higher concentrations of DDXs (sum of o,p'- and p,p'-DDT, -DDD, and -DDE and p,p'-DDMU), especially p,p'-DDT and low-brominated PBDEs, while compound feeds had higher concentrations of highly brominated BDEs, e.g., BDE-209. In addition, no concentration difference of HCHs and PCBs was found between trash fish and compound feeds. The habit of direct use of trash fish as fish feeds has induced the accumulation of DDXs in aquatic species in China, and trash fish collected in South China seemed to be slightly hazardous to wildlife because of the concentrations of DDXs. The results from the present study suggest that the use pattern of fish feeds in China may have to be adjusted to minimize contamination of fishery products and wildlife by PHHs. Use of compound feeds produced with controlled procedures should be encouraged, whereas that of trash fish should be restricted, at least for now.

EFFECTS OF DIFFERENT TYPES OF FEED ON GROWTH, SURVIVAL AND DIGESTIVE ENZYME ACTIVITY OF EARLY JUVENILE-STAGE MARBLE GOBY, Oxyeleotris marmoratus

The stable mass seed production technique of marble goby, Oxyeleotris marmoratus has not yet been established due to high mortality occurring on the early juvenile stage and/or after 40 days after hatching (d AH). In order to establish the mass seed production technique, O. marmoratus juveniles of 40 d AH were reared for 60 days to determine growth, survival and digestive enzyme activity at different types of feed (trash fish, artificial feed and Artemia sp. nauplii). Specific growth rate (5.32) and survival rate (91.3%) in juveniles fed Artemia sp. nauplii showed significantly higher (P&lt;0.05) than those of juveniles fed trash fish and artificial feed. At the end of the experiment, the mean specific trypsin, amylase and lipase activities of juveniles fed Artemia sp. nauplii were recorded as 0.04 mU mg protein-1m-1, 0.114 mg maltose mg protein-1h-1 and 9.58 m Units, respectively, and they were significantly higher than those of juveniles fed trash fish and artificial feed. In the present study it was shown that O. marmoratus early juveniles had more efficient digestibility and absorption the nutrient when fed with Artemia.

Management of marine cage aquaculture

Marine cage aquaculture produces a large amount of waste that is released directly into the environment. To effectively manage the mariculture environment, it is important to determine the carrying capacity of an aquaculture area. In many Asian countries trash fish is dominantly used in marine cage aquaculture, which contains more water than pellet feed. The traditional nutrient loading analysis is for pellet feed not for trash fish feed. So, a more critical analysis is necessary in trash fish feed culturing areas. Corresponding to FCR (feed conversion rate), dry feed conversion rate (DFCR) was used to analyze the nutrient loadings from marine cage aquaculture where trash fish is used. Based on the hydrodynamic model and the mass transport model in Xiangshan Harbor, the relationship between the water quality and the waste discharged from cage aquaculture has been determined. The environmental carrying capacity of the aquaculture sea area was calculated by applying the models noted above. Nitrogen and phosphorus are the water quality parameters considered in this study. The simulated results show that the maximum nitrogen and phosphorus concentrations were 0.216 mg/L and 0.039 mg/L, respectively. In most of the sea area, the nutrient concentrations were higher than the water quality standard. The calculated environmental carrying capacity of nitrogen and phosphorus in Xiangshan Harbor were 1,107.37 t/yr and 134.35 t/yr, respectively. The waste generated from cage culturing in 2000 has already exceeded the environmental carrying capacity. Unconsumed feed has been identified as the most important origin of all pollutants in cage culturing systems. It suggests the importance of increasing the feed utilization and improving the feed composition on the basis of nutrient requirement. For the sustainable development of the aquaculture industry, it is an effective management measure to keep the stocking density and pollution loadings below the environmental carrying capacity. The DFCR-based nutrient loadings analysis indicates, in trash fish feed culturing areas, that it is more critical and has been proved to be a valuable loading calculation method. The modeling approach for Xiangshan Harbor presented in this paper is a cost-effective method for assessing the environmental impact and determining the capacity. Carrying capacity information can give scientific suggestions for the sustainable management of aquaculture environments. It has been proved that numerical models were convenient tools to predict the environmental carrying capacity. The development of models coupled with dynamic and aquaculture ecology is a requirement of further research. Such models can also be useful in monitoring the ecological impacts caused by mariculture activities.

Effects of defatted soybean protein levels on growth performance and nitrogen and phosphorus excretion in Asian seabass ( Lates calcarifer)

The effects of defatted soybean meal protein levels in Asian seabass diets on growth, feed utilization, protein digestibility and nitrogen and phosphorus excretion were investigated. Six isonitrogenous diets were formulated to contain defatted soybean meal to replace fish meal at 0, 10%, 20%, 30%, 40% and 50% of fish meal protein, respectively. Trash fish was also used in the experiment. The fish were cultured in aerated flow-through 81 l aquaria filled with 54 l of seawater. Each diet was fed twice daily to satiation to three replicate groups of juvenile seabass with an average initial weight of 0.95 ± 0.04–0.99 ± 0.02 g/fish for 12 weeks. Growth of fish fed diets 1 and 2 (0 and 10%) was significantly higher than that of fish fed diets 3–6 (20–50%) and trash fish. Fish fed diet 6 had the lowest weight gain and specific growth rate but, was not significantly different from those of fish fed diet 5 and trash fish. Feed conversion efficiency (FCE), protein efficiency ratio (PER) and productive protein value (PPV) of fish fed diets 1, 2 and 3 were significantly higher than those of the other diets, particularly the trash fish fed groups. The ammonia excretion of fish fed experimental diets peaked at 10 and 12 h after the first meal and was lowest for fish that were fed diet 1. On the other hand, ammonia excretion of fish fed trash fish was the highest. Fish fed diet 1 had the highest phosphorus excretion, whereas fish fed trash fish had the lowest. Loss values calculated from supply and gain confirmed data obtained through excretion measurements. Furthermore, replacing fish meal with soybean meal in the diets tended to increase nitrogen loss. Feed costs for production of 1 kg of fish was also determined. The cost of diet 2 with soybean meal replacing 10% of fish meal protein was 34.20 baht (US$0.81)/kg of fish whereas that of diet 6 with soybean meal replacing 50% of fish meal protein was the highest at 40 baht (US$0.95)/kg of fish. The results of the present study indicated that soybean meal can replace fish meal at the level of 10% of fish meal protein in diets for Asian seabass with good growth and feed utilization. In addition, replacing fish meal with soybean meal at the stated levels resulted in a reduction of nitrogenous waste in comparison with trash fish.

Feeding trashfish Odonus niger lipid enriched Artemia nauplii on growth, stress resistance and HUFA requirements of Penaeus monodon postlarvae

Artemia franciscana nauplii (A to E) were enriched with different concentrations of emulsified Odonus niger liver oil (0–4%). These enriched Artemia nauplii were fed to postlarvae (PL5–PL20) of Penaeus monodon and assessed the survival, growth, stress resistance and HUFA requirement. Maximum specific growth rate of 24.55±0.287% was recorded in diet D and the minimum of 22.67±0.237% in diet A fed individuals. Survival of P. monodon fed with lipid enriched Artemia nauplii was higher than the control diet (A). The salinity stress resistance (0 ppt) of P. monodon revealed that the individuals fed with diet D were more stress-resistant (50 min) than those that received other diets (40–45 min). At high salinity (50 ppt), diets D and E fed individuals survived up to 480 min, whereas in other diets (A, B and C), the larvae survived up to 420 min. In both low and high salinities, a cumulative mortality index (CMI) of 121±0.816 and 91.66±0.942 was recorded for diet A fed groups and it was reduced by 15.14±0.930% and 21.44±0.450% for those fed diet D. The fatty acid profile of the Artemia nauplii enriched with selected concentrations (0–4%) of O. niger liver oil was varied remarkably. The PUFA showed an increasing trend in enriched Artemia nauplii ranging from 32.41% (by weight) in control (A) to 46.16% (by weight) in 3% (D) lipid. Similarly, the PUFA of P. monodon postlarvae (PL5–PL20) fed with the lipid enriched Artemia nauplii were increased from 29.72% (by weight) in control (A) to 44.13% (by weight) in postlarvae received 3% (D) lipid enriched Artemia nauplii. The overall performance of growth enhancement, stress tolerance and fatty acid profile of P. monodon revealed that P. monodon postlarvae fed with D (3% lipid) were more efficient than the other groups.

Replacement of fish meal by animal by-product meals in a practical diet for grow-out culture of grouper Epinephelus coioides

A feeding trial was conducted to evaluate the potential of replacing fish meal with processed animal by-product meals, meat meal and blood meal (4:1 ratio), in practical diets for juvenile grouper ( Epinephelus coioides). Eight isonitrogenous diets were formulated to contain 45% protein and 12% lipid. Fish meal was replaced by 0%, 10%, 20%, 30%, 40%, 60%, 80%, and 100% of meat meal and blood meal (4:1) mixture (diets 1–8). The diet with 100% fish meal (diet 1) or trash fish as feed (diet 9) were used as controls. Grouper juveniles were reared in 250-l circular fiberglass tanks maintained in a flow-through seawater system. Each dietary treatment was tested in quadruplicate groups of 25 fish per tank arranged in a completely randomized design. Fish were fed the diets twice per day at a daily feeding rate of 5–6% of biomass and trash fish at 10–12% of biomass for 60 days. Percentage weight gain, specific growth rate (SGR), survival, feed conversion ratio (FCR) and body composition of grouper juveniles were measured. There were no significant differences ( P>0.05) in growth performance among fish fed diets 1–7 (0–80% fish meal replacement) with those fed diet 9 (trash fish as feed). However, fish fed diet 3 had significantly higher ( P<0.05) growth than those fed diet 8 (100% fish meal replacement). Survival among fish fed the experimental diets did not significantly differ (96–100%) but was significantly higher ( P<0.05) than survival (90%) of fish fed trash fish. These results showed that up to 80% of fish meal protein can be replaced by processed meat meal and blood meal coming from terrestrial animals with no adverse effects on growth, survival, and feed conversion ratio of E. coioides juveniles.

Management of marine fish farming in the sub-tropical environment: a modelling approach

Two deterministic models were applied to simulate hydrographic and water quality conditions within a sub-tropical marine fish culture site, where trash fish is used as feed. A two-dimensional, two-layer hydrodynamic model of tidal flows and salt transport calculated the water level, velocity and salinity in each grid cell of 50 m square in each layer within the culture area approximately every 30 s during a tidal cycle. Results from this flow model provided hydraulic data for input into a three-dimensional tidal water quality model, which was run to simulate water quality due to specified pollutant loadings from the marine fish culture operations. Simulated output from the models agreed reasonably well with observed field data, except for dissolved oxygen and nitrate levels in surface waters. This could be due to a conservative estimation of re-aeration rates in the model system. In applying the models to sub-tropical waters of Hong Kong, the simulation predicted the extent of pollution and area affected under varying fish stock and pollutant loadings. It was shown that impacts of fish culture activities on water quality at the test culture site were localized owing to strong advection by tidal residual flows. The higher simulated level of organic nitrogen in the bottom waters over the year at the test fish culture site was due to increased release of organic nitrogen through decay of wasted feed from the sea bed and from trash fish feed. Models of marine fish culture and environmental effects have applications in determining acceptable stocking levels, and the effects of changing feed and culture species, and for locating suitable culture sites in coastal areas.

Effects of broodstock dietary lipid on fatty acid compositions of eggs from sea bass ( Dicentrarchus labrax)

Samples of sea bass ( Dicentrarchus labrax) eggs from broodstock which had been fed either a formulated pelleted feed, containing fish and corn oil, or a local trash fish, bogue ( Boops boops) were analysed for lipid class compositions, fatty acid compositions of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) and wax ester and fatty alcohol compositions of wax esters. The pelleted feed contained 1.3 mg g −1 of arachidonic acid (20:4n-6; AA) and an AA/eicosapentaenoic acid (20:5n-3; EPA) ratio of 0.1 while the trash fish contained 4.8 mg g −1 AA and an AA EPA ratio of 0.7. Docosahexaenoic acid (22:6n-3; DHA) concentrations were similar for both diets (about 23 mg g −1). The fatty acid compositions of PC, PE and PI from eggs of fish fed trash fish contained significantly more AA, 22:5n-6 and DHA compared to fish fed the pelleted feed. The AA EPA ratios in these phospholipids were around five-fold higher in the trash fish-fed group compared to those fed the fish and corn oil containing diet. In PI, which contains characteristically high levels of AA, the AA EPA ratios were 1.5 and 8.6 for eggs derived from broodstock fed the pelleted diet and the trash fish, respectively. Determination of lipid class compositions of sea bass eggs revealed the presence of high levels of wax esters which were previously unrecorded in this species. The use of broodstock diets containing blends of corn oil and Northern hemisphere fish oils may be undesirable in that they contain high levels of 18:2n-6 and have low ratios of DHA EPA and of AA EPA . In an effort to improve egg quality and larval viability, efforts should be directed towards establishing the best ratio of DHA/EPA/AA in formulated feeds such that requirements for neural function and visual performance are maximised and that production and efficacy of eicosanoids are adequate to permit physiological functions to operate efficiently.