Kilogram Of Fish Research Articles

Early life-history stages of the olive barb, Systomus sarana (Hamilton), and a key ontogenetic systematic character of Smiliogastrinae.

The current study aims to uncover the early life-history stages of Systomus sarana, a medium-sized smiliogastrin cyprinid important for aquaculture in South Asia. The fish were effectively bred in captivity by administering 0.25 mL of breeding hormone per kilogram of fish. The spawning occurred 8.54 ± 0.55 h after the injection, and the eggs were phyto-lithophilic with a pale yellow color and a diameter of 1.49 ± 0.04 mm. Hatching occurred 17 h after fertilization, and the yolk-sac larvae of 3.43 ± 0.08 mm total length (TL) were adhering to the plant parts and other substrata with the cement glands on the forehead. On the third day, with complete absorption of the yolk sac and the disappearance of the attachment organ, the pre-flexion larvae measured 5.3 ± 0.11 mm TL. On the eighth day, the flexion larvae measured 6 ± 0.4 mm TL with a well-inflated posterior swim bladder, and the post-flexion larvae, at 11 days post-hatching (dph), developed a two-chambered gas bladder. The juvenile stage, on day 21 post-hatching, was marked by the loss of the median finfolds and the appearance of black blotches on the caudal, subdorsal, and supra-anal regions. The commencement of squamation and the appearance of the rudiments of maxillary barbels distinguished the juvenile stage. The subadults measuring 4.6 ± 0.36 cm TL had finished squamation and completely lost the subdorsal and supra-anal blotches. We propose that the presence of subdorsal blotches is a distinctive ontogenetic and systematic feature of larval and juvenile forms of smiliogastrin barbs.

The emission intensity of the freshwater aquaculture production value chain in Georgia

This contribution assesses the greenhouse gas (GHG) emission intensity among two freshwater aquaculture sub-chains: both the carp and catfish and the trout and sturgeon sub-chains in Georgia. The data were derived from 155 semi-structured interviews conducted in Georgia in 2021. The GHG per kilogram of production and per Georgian Lari (GEL) of value added of specific farm types were calculated. Emission intensity per kg of production is similar for both sub-chains, while value-added differs more significantly. Our results show the existence of economies of scale in trout production due to the ability of larger farms to use less feed per kilogram of fish. From this perspective, increasing the production scale can lead to lower emission intensity and improved economic performance. In the case of the carp sub-chain, economies of scale are not present. Therefore, we recommend conducting research on increasing the scale of production through the use of larger ponds. This solution brings obvious economic benefits, but from an environmental point of view, it may pose certain threats. Moreover, the countereffects of scaling production, such as wild fish depletion, water pollution, and the spreading of fish diseases and the farmed fish escaping, must also be adequately addressed.

The Effects of Substituting Fishmeal Based-Diet With Plant Based-Diet on Nile Tilapia (Oreochromis niloticus) Fish Growth, Feed Efficiency and Production Cost-Effectiveness

Aquaculture started in The Gambia in 1979 but is still at a rudimentary stage. Many government and private interventions conducted on fish farming failed due to the high cost of feed. Fishmeal based diets are expensive thus using them makes many fish farming in the developing countries unprofitable businesses. There is a need to use locally available plant ingredients to develop fish feeds. This study was conducted to compare the growth, feed efficiency and production cost-effectiveness of the Nile tilapia (Oreochromis niloticus) fish fed on fishmeal-based diet (control diet) to that of the same fish fed on plant-based diet (test diet). The two isonitrogenous (30 % CP) experimental diets were tested on 0.81g Nile tilapia (Oreochromis niloticus) fry for a period of six (6) weeks. The control diet composed of fishmeal, soybean meal, cassava flour, and a blend of palm oil and fish oil premixed with mineral and vitamin supplements. The plant-based diet consisted of groundnut cake, wheat flour, brewery waste and rice bran supplemented with mineral and vitamin premixes. Regarding growth performance parameters, there were significant differences between the final mean weight, mean weight gain, percentage mean weight gain and the specific growth rate of Nile tilapia (Oreochromis niloticus) fish fed on the control diet and the plant-based diet. For feed efficiency parameters, there was significant difference between feed conversion ratio for fish fed the control diet and the plant-based diet. However, there was no difference between the fish fed the two diets with regards to the protein efficiency ratio or survival rate. The plant-based diet was inferior to the fishmeal-based diet in terms of growth and feed efficiency parameters of 0.81g Nile tilapia (Oreochromis niloticus) fry. When compared to the fish-meal based diet, the plant based-diet was more cost-effective in producing a kilogram of feed but less cost-effective in producing of a kilogram of fish. Therefore, a plant based-diet cannot replace a fishmeal based-diet without compromising Nile tilapia (Oreochromis niloticus) fish growth performance and production cost-effectiveness.

The Effects of Substituting Soybean Meal, Wheat Flour and Cassava Flour with Groundnut Cake, Poultry By-product Meal, Brewery Waste and Rice Bran on Growth and Body Composition of Tilapia Fry

An 8-week feeding trial was conducted to evaluate the effects of replacing soybean meal, wheat flour and cassava flour with groundnut cake, poultry by-product meal, brewery waste and rice bran on the growth and body composition of Oreochromis niloticus fry at 3.77 g initial mean weight. Four iso-nitrogenous (35 % CP) experimental diets (1 control, 3 substituted) were prepared and administered. Control diet (Diet 1) has fishmeal, soybean meal, wheat flour, cassava flour and a blend of palm oil and fish oil as macro-ingredients. Soybean meal, wheat flour and cassava flour in the control diet were replaced with groundnut cake, brewery waste, rice bran to form Diet 2. Those three ingredients in the control diet were replaced with poultry by-product meal, brewery waste and rice bran to form Diet 3. Finally, Diet 4 was formulated with a combination of groundnut cake and poultry by-product meal, brewery waste and rice bran to replace the three ingredients above. Value-wise, the best growth performances were observed from the fish fed on Diet 3 but there were no significant differences among all the treatments. Generally, the substitution of soybean meal, wheat flour and cassava flour with groundnut cake, poultry by-product meal, rice bran and brewery waste have no major effect on the body composition of the fish. Meanwhile, the substitution has a positive effect with respect to feed cost in producing a kilogram of feed and a kilogram of fish. The authors suggested that the substitution of soybean meal, wheat flour and cassava flour with groundnut cake or poultry by-product meal or the combination of groundnut cake and poultry by-product meal, brewery waste and rice bran is more cost-effective and economical for Nile tilapia farming.

Economic Study of Fisheries at North Sinia Governorate

The total fish production in North Sinai Governorate during the period from 2007-2018 was estimated at 5740.9 tons, with a relative importance estimated at 0.4% of the total Egyptian fisheries, including Lake Bardawil, it was estimated at 4146.2 tons, and that fish production in the Mediterranean Sea in North Sinai Governorate was estimated at 1594.6 Tons, and the relative importance of Lake Bardawil was estimated at about 72% in North Sinai, and the importance of the Mediterranean by about 28% in North Sinai, and the relative importance of fish varieties, crabs, shrimps, the puree family, other varieties, lot, were estimated at 30%, 21%, 16.3 %, 7.5%, 4.4% and 0.6%, respectively, with the Bardawil Lake fisheries, And that the total costs of the bear trade were estimated at 30,966 pounds, at a cost estimated at 13.3 pounds / kilo. Fish, and the average total production of the bear craft was estimated at 2325 kilograms of fish, and the total income was estimated at 69,750 pounds, and the bear craft achieved net income, estimated at 38,783 pounds. The total cost of the reed craft was estimated at 69,450 pounds, at a cost of 11 pennies / kilo. Fish, and the average total production of the reed craft was estimated at 6300 kilograms of fish, and the total income was estimated at 189,000 pounds, and the bear craft achieved a net income, estimated at 119549 pounds. As for the socio-economic survey of fishermen, it was possible to identify the relative importance of the profession of parents, the ownership of fishermen, and the quality of housing, and to identify the most important problems faced by the development of fish wealth within the fisheries of North Sinai Governorate, and the problems were numerous, including the problem of low income, and it occupied the first place With an estimated number of about 520 fishermen, and a relative importance estimated at about 93%, and in the last place, the problem of the role of cooperative societies came, with a relative importance estimated at about 27%, and an estimated number of about 150 fishermen.

The dilemma of opportunity in developing a life cycle assessment of emerging aquaculture systems - a case study of a Eurasian perch (Perca fluviatilis) hatchery recirculating aquaculture system.

Eurasian perch (Perca fluviatilis) has been identified as an aquaculture species that can contribute to supply and supplement wild stocks for niche markets in European alpine regions. As a species earmarked for expansion it is important to benchmark the environmental impact associated with its production. The case study site presented a dilemma of opportunity (the dilemma of carrying out a study to inform production processes, at the beginning or development of a product/system or to wait until it is established and in steady state). This dilemma is often a limiting factor in the assessment of emerging systems or products and as a result this site was data deficient in a number of areas (energy use, growth rate and water use) which required the use of an ab initio approach to overcome these gaps. Data for growth, oxygen and heating were modelled for one kilogram of fish to the farmgate for 2018. The generated data was investigated for environmental impact using life cycle assessment (LCA). Impact categories included in the study were global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), freshwater and marine ecotoxicity potential (FAETP and MAETP), cumulative energy demand (CED), net primary production use (NPPU) and water use. The results indicated that there was high variability between the inputs, outputs and impacts associated with the production of perch to the farmgate. The highest variability was observed in live feed use and energy inputs between the batches. This was related to egg quality and the survival rates of the batches. The nursery stage of production was found to have the greatest environmental burden of all stages. EP was dominated by emissions from the stock. Electricity use and feed were the greatest contributors to GWP, AP and FAETP. Electricity and heating had the greatest share of CED and MAETP. Water use (using the AWARE methodology) was dominated by feed production, fish culture and electricity generation. The result of this analysis echoes that of similar studies in that the dominant contributors to the life cycle impacts of RAS products are electricity and feed. This study constitutes the first LCA of perch production in RAS. In addition to this, the study also outlines a framework and methodology, which can be used to overcome the dilemma of opportunity when assessing the environmental burden of an emerging aquaculture system or species. This approach allows operators to overcome data deficits, which may exist and implement impact strategies prior to the finalisation of the process or system.

Immediate impact of COVID-19 across tropical small-scale fishing communities

The volume and value of fish catches by Indonesia's small-scale fisheries have declined significantly since national government restrictions on travel and social distancing were imposed in response to the COVID-19 pandemic. Using a digital data collection system (OurFish), that records purchases by fish traders from small-scale fishers, data was collected across 82 coastal communities in Southeast Sulawesi. We found that the number of active fishers and traders declined by more than 90% after the onset of the pandemic and the average weight of catch per fishing trip increased across fishers. Although the average price per kilogram of fish declined after the pandemic began, fishers that were able to maintain fishing had on average higher catches and therefore daily catch value was maintained. High value fisheries that usually enter export supply chains were more negatively impacted compared with lower value species that are commonly sold to local markets. We interviewed 185 small scale fishers and fish traders across 20 of the 82 communities in Southeast Sulawesi province, recording the perceived level of impact on local fisheries and the fish trade, causes of this impact and proposed coping strategies. Over 50% of both fishers and fish traders believed low demand for fish from traders and a decline in the price received for fish were disrupting their lives. Approximately 75% of both male and female fishers are coping by continuing to fish, highlighting that there were few alternative livelihoods available at the time of the interviews. Our results provide key insights into the vulnerability of small-scale fishing communities to impacts of the COVID-19 pandemic.

Scenarios of Sustainable Fishing in the Zapatosa Marsh (Colombia) Simulated with a System Dynamics Model

The Zapatosa marsh (ciénaga de la Zapatosa) is located in the Department of Cesar in Colombia. In 2018, the muddy complex of Zapatosa was declared a Ramsar wetland, for this reason, it is necessary to develop management strategies for the marsh that allow not only the conservation of the ecosystem. The objective of this work is to use System Dynamics as an evaluation tool for three possible management scenarios of artisanal fishing in the Zapatosa marsh. A qualitative causal diagram and a quantitative Stock and Flow diagrams were designed to describe the dynamics of fish and fishermen populations in the marsh. The initial model setting and parametrization derived from values gathered from different sources of information. The calibration of the model was carried out with reference data on total catch of kilograms of fish and population data from the Department of Cesar. The data obtained through the “Aquaculture and artisanal fisheries survey of the Department of El Cesar” in 2018 were reproduced in the model and then compared with 3 alternative management scenarios. Scenario 1 included strictly applying of the fishing stopover for the species Prochilodus magdalenae and for catfish (Pseudoplatystoma magdaleniatum, Pimelodus blochii y Sorubim cuspicaudus). Scenario 2 considered to apply the same prohibitions, but with a payment to fishermen for the care of the swamp at the time of prohibition. In Scenario 3 the fishermen under fishing stop will receive an income of a legal Colombian minimum monthly salary and will be engaged in practices of ecosystem services. Results showed that in some scenarios the economic situation of the fishermen is unable to meet the monthly family expenses in different periods of the year. On the other hand, there is greater economic stability and fish populations when adopting Scenario 3, but it is difficult to achieve in the short or medium term. Scenario 2 shows little recoveries in fish populations and a higher money availability to the local community than in Scenario 3, in certain months, presenting the best short-term management option. The presented model encourages further simulation scenarios of the Zapatosa Marsh.

Options to reuse sludge from striped catfish (Pangasianodon hypophthalmus, Sauvage, 1878) ponds and recirculating systems

This paper compares the quantity and quality of solid waste obtained from traditional ponds and recirculating aquaculture systems (RAS) for striped catfish and evaluates methane and compost production from these wastes. Striped catfish sludge was collected from four commercial ponds along the Mekong river and from three indoor RAS. The amount of sludge dry matter produced per kilogram of fish in ponds was 6 times higher than that in RAS. However, the concentration of nutrients in solid waste from RAS was much higher, with better compost quality and higher methane yield than that of sludge from ponds. Out of the collected 381 L biogas, the methane yield of striped catfish’s solid waste in RAS systems was 201 L per kg chemical oxygen demand (COD). In ponds, the collected 267 L biogas yielded 125 L CH4 per kg COD. The higher methane production from RAS sludge concurred with higher digestibility of COD: 58% for RAS versus 38% for ponds. The quality and quantity of methane from striped catfish sludge were lower than that for other animal manures, and the resulting electricity yield was low. Considering the higher nutrient concentration in RAS-sludge, we recommend the combination RAS and composting in reusing sludge, which is presently the best option for a more sustainable and cleaner striped catfish production system.

Economic Value A Dried Fish Business Development in Bengkulu City

The study aims to analyze the economic value of dried fish business by considering its added value of Hayami and marketing. This study uses primary data by surveying 55 dried fish producers in Bengkulu city. The results show that the average output price of dried fish is Rp6,586.61/kg. Using formula of Hayami’s added value, the average added value gained is Rp3,486.14/kg. This informs that every a kilogram of fresh fish processed into dried fish will create added value of Rp3,486.14. When labor under consideration, labor added value in fish dried industries is Rp651.37 informing that an average of labor income for every kilogram of fish dried produced. The research also found that there are four patterns of marketing channels. From weekly average production of dried fish, i.e., 4,345 kg, 43.73 % is distributed to big traders while the remaining, 56.27%, is consumed directly. From big traders, dried fish are then distributed through three channel, namely, (1) 43.11 % are marketed to the first intermediate trader, then, to intercity merchants, retailers and end customers in Bengkulu city, (2) 26.32% are distributed to second intermediate trader who then marketed to retailers and end customers; and (3) 31.58 % are marketed to third intermediate trader who, then, market to the intercity merchants and consumers. Marketing margins of this dried fish is Rp1,000/kg from producers to traders and Rp2,000/kg per kg of fish from traders to retailers.

Profitability analysis of catfish farming in Suleja local government area of Niger state, Nigeria

The problem of profitability and scale of production of catfish has not been properly addressed. This study was conducted in Suleja Local Government Area of Niger State to assess the profitability of catfish production. Forty (40) catfish farmers were selected from the study area using simple random sampling techniques. Structured questionnaire was used to collect data from the respondents. The analytical tools used include, descriptive statistics, net farm income analysis and profitability ratios and multiple regression functions. The result of the analysis showed that the average total cost per kilogram of fish was N321.23k and the average total revenue per kg of fish was N501.31. This gives a net farm income of N180.08k per kilogram of fish farmed. The study also showed that the sum total of elasticity of variables was less than one (0.994), this indicates that catfish farming in the study area is in stage II, which is the rational stage of production. Double-log functional model was chosen as lead equation. The value of R2 was 0.998. The number of ponds (X1) and number of fingerlings (X3) were significant at 1%, while labour(X5) was significant at 5% levels of significance. The F- ratio of 2964.370 was significant at P (< 0.01). This implies that all the explanatory variables taken together have significance on the dependent variable (Y), the output. Due to expensive nature of flow-through and re-circulatory ponds, earthen ponds were mostly preferred by majority (92.5%) of the fish farmers in the study area. The major problems faced by catfish farmers include; water, high cost of feed and capital.Key Words: cat fish, net farm income, profitability ratio

Economic values of growth and feed efficiency for fish farming in recirculating aquaculture system with density and nitrogen output limitations: a case study with African catfish (Clarias gariepinus).

In fish farming, economic values (EV) of breeding goal traits are lacking, even though they are key parameters when defining selection objectives. The aim of this study was to develop a bioeconomic model to estimate EV of 2 traits representing production performances in fish farming: the thermal growth coefficient (TGC) and the feed conversion ratio (FCR). This approach was applied to a farm producing African catfish (Clarias gariepinus) in a recirculating aquaculture system (RAS). In the RAS, 2 factors could limit production level: the nitrogen treatment capacity of the biofilter or the fish density in rearing tanks at harvest. Profit calculation includes revenue from fish sales, cost of juveniles, cost of feed, cost of waste water treatment, and fixed costs. In the reference scenario, profit was modeled to zero. EV were calculated as the difference in profit per kilogram of fish between the current population mean for both traits (µt) and the next generation of selective breeding (µt+Δt) for either TGC or FCR. EV of TGC and FCR were calculated for three generations of hypothetical selection on either TGC or FCR (respectively 6.8% and 7.6% improvement per generation). The results show that changes in TGC and FCR can affect both the number of fish that can be stocked (number of batches per year and number of fish per batch) and the factor limiting production. The EV of TGC and FCR vary and depend on the limiting factors. When dissolved NH3-N is the limiting factor for both µt and µt+Δt, increasing TGC decreases the number of fish that can be stocked but increases the number of batches that can be grown. As a result, profit remains constant and EVTGC is zero. Increasing FCR, however, increases the number of fish stocked and the ratio of fish produced per kilogram of feed consumed ("economic efficiency"). The EVFCR is 0.14 €/kg of fish, and profit per kilogram of fish increases by about 10%. When density is the limiting factor for both µt and µt+Δt, the number of fish stocked per batch is fixed; therefore, extra profit is obtained by increasing either TGC, which increases the annual number of batches, or by decreasing FCR, which decreases annual feed consumption. EVTGC is 0.03 €/kg of fish and EVFCR is 0.05-0.06 €/kg of fish. These results emphasize the importance of calculating economic values in the right context to develop efficient future breeding programs in aquaculture.

AN ECONOMIC STUDY FOR PRODUCTION AND CONSUMPTION OF FISH IN EGYPT

The Fisheries is considered an important source of national income. Fish product is one of important component in the agricultural production. the problem of this study determined in increasing fish food gap with about 319 thousand tons in 2012. The study aimed to description and analysis of fish production in Egypt in terms of domestic production, imports, exports, consumption, the food gap, the proportion of self-sufficiency, the average per capita available amounts for consumption, In addition, studying the factors that effect on the production and consumption of fish in Egypt. The study should be verification the following results The fish production in Egypt is growing annually by about 55.9 thousand tons during the period average (1995-2012), which represents about 6.4% of the annual average, Imports of fish increase during the study period by about 4.5 tons by about 33.6 million pounds per year, and fish exports are increasing annually by about 0.68 tons by about 5.3 million pounds annually while the production of fish according to different sources show that fish farming ranked first by about 55.3% of the average amount of production, and the total northern lakes ranks second at about 14.7%, while the production of the Sea (White, Red ) ranked third by about 14.1%, and the River Nile is ranked fourth by about 10.2 and inland lakes and coastal ranked fifth and sixth by about 5.2%, 0.5% respectively during the study period . Nevertheless, the results show that there are statistically significant differences between the indicators during the period average (2008-2012). In addition, the results show that tilapia ranked first with an average production of about 646.4 thousand tons representing about 52.1%, While the average production of mullet, carp, catfish, reaches about 181.9, 142.1, 43.1 thousand tons respectively, representing about 14.7%, 11.5%, 3.5% respectively of the average total fish production during the period (2008-2012). The study also indicate that the most important economic factors that affecting on the fish production in Egypt is the amount of fish imports, the quantity of available fish, the partial elasticity of them are about -0.294 and 1.2, which indicates that an increase in the quantity of imports by about 1% leads to the decline of fish production by about 0.3%, increase the amount of fish consumption by about 1% lead to increase the amount of production by about 1.2%. However, the results show that the most important factors affecting on the amount of fish consumed in Egypt is the population and the average price of a kilogram of fish. Therefore, the study recommended the development of fisheries sector and set up of collection centers for the production of fish near fish farms, Moreover, the necessity of expansion in aquaculture to fill the fish food gap.

RETRACTED: Energy direct inputs and greenhouse gas emissions of the main industrial trawl fishery of Brazil

This study provides first-time estimates of direct fuel inputs and greenhouse gas emissions produced by the trawl fishing fleet operating off southeastern and southern Brazil. Analyzed data comprised vessel characteristics, landings, fishing areas and trawling duration of 10,144 fishing operations monitored in Santa Catarina State from 2003 to 2011. Three main fishing strategies were differentiated: 'shrimp trawling', 'slope trawling' and 'pair trawling'. Jointly these operations burned over 9.1 million liters of diesel to land 342.3 million kilograms of fish and shellfish. Annually, 0.023-0.031 l were consumed for every kg of catch landed. Because all fishing strategies relied on multispecific catches to raise total incomes, estimates of fuel use intensity were generally low but increased 200-900% if only nominal targets were considered. In nine years, trawling operations emitted 6.69 GgC to the atmosphere, between 2300 and 3300 tons CO2 per year.

Comparative Economics of US Catfish Production Strategies: Evidence from a Cross‐sectional Survey

AbstractUnderstanding the effects of specific management strategies on yields and economic outcomes on commercial catfish farms could provide useful guidance to catfish farmers on the most profitable sets of production practices. Data from the U.S. Department of Agriculture–National Animal Health Monitoring System (USDA–NAHMS) 2009 survey of production practices on catfish farms in Alabama, Arkansas, Louisiana, and Mississippi were used to identify five clusters of catfish farms that use various stocking densities, channel versus hybrid catfish, different aeration levels, and utilize automated oxygen sensors. The lowest production costs ($1.96/kg) were found in cluster 1 and were followed in order of increasing costs per kilogram of clusters 2 and 4 ($2.16/kg) and cluster 5 ($2.73/kg); the highest cost corresponded to cluster 3 ($2.84/kg). The lowest risk levels corresponded to the clusters with the lowest production costs per kilogram of fish and the highest risk levels to the highest production costs. This analysis demonstrated that different types of management models can achieve similar levels of production costs ($/kg), and it appears that there is not one single economically optimum way to raise catfish. The key to least‐cost production is to balance the use of inputs, their associated costs, and the yield produced to achieve economic efficiency within the farm's overall business and management model.

Farinha de folha de leucena (Leucaena leucocephala Lam. de wit) como fonte de proteína para juvenis de tambaqui (Colossoma macropomum CUVIER, 1818)

O tambaqui (Colossoma macropomum) é um peixe onívoro, natural da bacia amazônica, que possui elevado valor comercial. Características de rusticidade e desempenho produtivo destacam esta espécie para criação em cativeiro. Contudo, em criações comerciais de peixes, os custos com alimentação podem corresponder de 60 a 80% dos custos totais de produção, sendo a proteína o nutriente mais caro da dieta. O objetivo deste trabalho foi avaliar o desempenho produtivo de juvenis de tambaqui alimentados com rações contendo farinha de folha de leucena como fonte protéica. 240 juvenis foram distribuídos em 12 aquários experimentais (350 L), em um delineamento experimental inteiramente casualizado com quatro tratamentos (0%, 8%, 16%, 24% de inclusão de farinha de folha de leucena na ração) e três repetições. Foram determinados o ganho de peso, conversão alimentar aparente, taxa de crescimento específico, taxa de eficiência protéica e custo de produção do quilograma de peso vivo ganho. Para as variáveis estudadas, não houve diferença significativa (p>0,05) entre os tratamentos, indicando que é possível incluir até 24% de farinha de folha de leucena em rações para juvenis de tambaqui, sem comprometimento das variáveis estudadas, embora a substituição não tenha representado redução no custo de produção do quilograma de peixe.

SENSORY ORGAN DISCOVERY DEMYSTIFIES RORQUAL WHALE FEEDING

![Figure][1] The rorqual whale family is composed of the largest animals on Earth with a unique way of eating their prey: they dive into aggregations of small crustaceans and fish at great depths and lunge with their mouths wide open, engulfing kilograms of fish in a single mouthful. The

Output of organic material from land-based juvenile Atlantic cod (Gadus morhua) tanks

A mass balance experiment was conducted in which dry mass, dissolved organic carbon, total nitrogen, lipid classes, and fatty acids were quantified in the inflow and outflow of land-based juvenile Atlantic cod (Gadus morhua) tanks. The inflow contained 89.9 ± 15.4 g/day of dry mass that increased to 187 ± 39 g/day in the outflow. Correction for the inflow indicated 96.8 ± 33.8 g/day of excess feed and faeces left the tanks amounting to a feed to waste conversion ratio of 25 %. The amount of feed in the waste was estimated to be 3 %. The breakdown indicator free fatty acid (43.1 ± 9.5 % total lipid), the markers of zooplankton and subsequent indicators of the feed, 20:1ω9 and 22:1ω11, and the essential fatty acid docosahexaenoic acid (DHA) were all significantly higher (p < 0.020) in the outflow compared to the inflow. The output from the entire aquaculture facility was calculated from the experimental tanks and gave 1,060 ± 370 g/day dry mass and 1.5 ± 0.4 g/day DHA, which could support 0.44 tonnes of mussels assuming an average weight of 5.31 g/mussel. Additionally, the output data were calculated per kilogram of fish and used to estimate potential output for operational Atlantic cod farms. An 1,880 tonne farm would produce 3,170 ± 870 kg/day dry mass and 4.7 ± 1.7 kg/day of DHA, which could theoretically support 1,400 tonnes of mussels. Natural mussels and those grown in co-culturing systems could assimilate such valuable compounds that would otherwise be lost.

Evaluation of a Low‐head Recirculating Aquaculture System Used for Rearing Florida Pompano to Market Size

A low‐head recirculating aquaculture system (RAS) for the production of Florida pompano, Trachinotus carolinus, from juvenile to market size was evaluated. The 32.4‐m3 RAS consisted of three dual‐drain, 3‐m diameter culture tanks of 7.8‐m3 volume each, two 0.71‐m3 moving bed bioreactors filled with media (67% fill with K1 Kaldness media) for biofiltration, two degassing towers for CO2 removal and aeration, a drum filter with a 40‐µm screen for solids removal, and a 1‐hp low‐head propeller pump for water circulation. Supplemental oxygenation was provided in each tank by ultrafine ceramic diffusers and system salinity was maintained at 7.0 g/L. Juvenile pompano (0.043 kg mean weight) were stocked into each of the three tanks at an initial density of 1.7 kg/m3 (300 fish/tank). After 306 d of culture, the mean weight of the fish harvested from each tank ranged from 0.589 to 0.655 kg with survival ranging from 57.7 to 81.7%. During the culture period, the average water use per kilogram of fish was 3.26 or 1.82 m3 per fish harvested. Energy consumption per kilogram of fish was 47.2 or 22.4 kwh per fish harvested. The mean volumetric total ammonia nitrogen (TAN) removal rate of the bioreactors was 127.6 ± 58.3 g TAN removed/m3 media‐d with an average of 33.0% removal per pass. Results of this evaluation suggest that system modifications are warranted to enhance production to commercial levels (&gt;60 kg/m3).

Custos e rentabilidade da produção de juvenis de tilápia-do-nilo em tanques-rede utilizando-se diferentes densidades de estocagem

Neste trabalho foi realizada a análise econômica da produção de juvenis de tilápia-do-nilo em tanques-rede utilizando-se diferentes densidades de estocagem. O experimento foi desenvolvido em área aquícola, em delineamento de blocos casualizados, com quatro densidades de estocagem (100, 200, 300 e 400 peixes m-3), avaliadas com seis repetições, em dois períodos de criação: de março a abril de 2005 (52 dias - peso inicial de 43,08 ± 2,98 g e peso final de 262,14 ± 47,86 g) e de março a abril de 2006 (58 dias - peso inicial de 43,16 ± 5,34 g e peso final 314,24 ± 73,30 g). Foram avaliadas as seguintes variáveis econômicas: custo da ração mais custo do juvenil dividido pela biomassa, em R$ kg-1; porcentagem do custo da ração por quilo de peixe produzido sobre o preço de venda; porcentagem do custo do juvenil por quilo de peixe produzido sobre o preço de venda e; porcentagem dos custos da ração mais do juvenil por quilo de peixe produzido sobre o preço de venda. Da menor densidade de estocagem (100) para a maior (400), ocorreu diminuição no ganho de peso diário e elevação do índice de conversão alimentar aparente, mas essa redução não comprometeu a taxa de sobrevivência. Entretanto, o ganho de biomassa aumentou com o adensamento de peixes. As maiores receitas líquidas foram obtidas nas densidades de estocagem de 100 e 200 peixes m-3. Os preços não remuneraram os custos operacionais (efetivo e total) em maiores densidades (300 e 400 peixes m-3). Os melhores resultados para a produção de juvenis de tilápia-do-nilo foram obtidos com densidades de até 200 peixes m-3.