James E. Rakocy's research while affiliated with University of the Virgin Islands and other places

Publications (16)

Research
Full-text available
Tilapia were grown in 1m^3 cages and production evaluated for daily weight gain, specific growth rate, net production, FCR, survival rate, and dressing percentage for various product forms.
Article
Aquaponics is an integrated fish and plant recirculating production system. The University of the Virgin Islands' raft aquaponic system uses a cylindro-conical clarifier as a primary solids removal device; however, a swirl separator may offer advantages. The objectives of the 8-wk experiment were to compare water quality parameters, Nile tilapia, O...
Article
Full-text available
Aquaponics is an integrated fish and plant recirculating production system. Solid fish waste must be removed from the production system to maintain optimal water quality parameters for fish and plant health. The University of the Virgin Islands (UVI) raft aquaponic system’s primary treatment device for solids removal is a cylindro-conical clarifier...
Article
Use of farm by-products is seen as an opportunity to achieve environmentalfriendly productions and abate costs. In the aquaponic facility at the University of the Virgin Islands a consistent amount of fish wastes are reduced into a solid state. Good levels in nutrients suggest the use of this material as a substrate in lieu of traditional commercia...
Article
Intensive recirculating aquaculture systems discharge effluent containing organic matter and nutrients daily. Managing discharged effluent will require innovative management approaches. Geotextile technology used in combination with polymers has been proven effective for dewatering aquaculture effluent. Composting the solids retained in the geotext...
Article
Full-text available
production of basil and okra. Tilapia were harvested every 6 weeks from one of four 7.8-m3 rearing tanks. Nile and red tilapia were stocked at 77 and 154 fish/m3, respectively. During the last 20 harvests, production of Nile and red tilapia averaged 61.5 and 70.7 kg/m3, respectively. Mean harvest weight was 813.8 g for Nile tilapia and 512.5 g for...
Article
This is the first controlled experiment to quantify the effect of introduced tilapia on indigenous species. This experiment was conducted in small earthen ponds (100 m2) to assess the impact of mixed-sex or all-male Nile tilapia (Oreochromis niloticus) on small indigenous species (SIS) commonly found in south Asia, mola (Amblypharyngodon mola), che...
Article
Aquaponic (AP) and greenwater tank culture (GW) systems have been developed at the University of the Virgin Islands for the intensive production of fish. Aquaponics is the combined culture of fish and hydroponic plants in recirculating systems. Greenwater tank culture utilizes a mixed suspended growth process involving autotrophic and heterotrophic...
Article
Aquaponics is the combined culture of fish and hydroponic plants in recirculating systems. Aquaculture effluent provides most of the nutrients required by plants if the optimum ratio between daily feed input and plant growing area is maintained. An experiment was conducted in an outdoor, commercial-scale aquaponic system on 0.05 ha of land in the t...
Article
Full-text available
A 200-m3 circular tank was evaluated in production trials stocked with sex-reversed Nile tilapia (Oreochromis niloticus) at 20 and 25 fish/m3 in Trial 1 and 2, respectively. Water treatment methods consisted of aeration, water circulation (mixing), solids removal and nitrification in the water column. The fish were fed ad libitum twice a day with a...
Article
The Caribbean has excellent potential for mariculture, yet insufficient information is available to describe the culture performance of indigenous finfish. Captured, wild palometa, Trachinotus goodei, (mean initial weight ± SE of 85 ± 5 g), were stocked into 2-nr flow-through tanks (10 fish/tank) and fed four formulated (pelleted) diets for 112 day...
Article
An outdoor, commercial-scale aquaponic unit for the production of red tilapia and leaf lettuce was in continuous operation at the University of the Virgin Islands for 2.5 years. The unit consisted of four fish rearing tanks (4.4 m 3 each, water volume), two cylindro-conical clarifiers (1.8 m 3 each), four rectangular filter tanks (0.7 m 3 each) con...
Article
Full-text available
A commercial-scale aquaponic system for the production of fish and vegetables was developed over 25 years at the University of the Virgin Islands (UVI). The UVI system, which has produced tilapia and a variety of vegetable crops, serves as a successful design model for the nascent aquaponics industry. The system consists of four fish rearing tanks...

Citations

... With such a low-pressure system, microscreen filters and bead filters usually aren't compatible since they require high flow rates to be effective. Therefore, the primary solids filters used in recirculating raft aquaponics include radial-flow, baffle, swirl separator, and screen-filters, which rely on gravimetric separation to be effective (Danaher, Shultz, Rakocy, & Bailey, 2011;Rakocy et al., 2006;Timmons & Ebeling, 2007). However, the removal efficiency of these filters is relatively low due to the differences in densities between settleable (>100 μm) and fine (1-100 μm) solid waste particles as well as infrequency of cleaning which allows settled solids to re-suspend and move downstream (Timmons & Ebeling, 2007). ...
... An understanding of the balance between fish-stocking rates, the amount of fish food used, and the number or plants in a system is important to optimize nutrient dynamics. As a result, the research on feeding rate ratios [2,23] includes numerous case studies addressing growth and other response variables for different combinations of plants, fish, and types of hydroponic grow beds [13,[23][24][25][26][27][28][29][30]. Most of these studies have analyzed commercial fish food. ...
... The integration of fish culture and plant production can provide several opportunities for farmers or producers, including sustainable agriculture, marketing versatility, and generation of multiple income streams. Environmentally, plant growth and yield in aquaponics can meet, or in some cases surpass, output values of either hydroponics or soil-based agriculture (Pantanella et al. 2011, Savidov et al. 2005. The shared core concepts of efficient water and land use, the ability to intensify crop production year round, and use in geographic areas not suitable for traditional agriculture has driven a recent increase in the popularity of aquaponics . ...
... Circular economies require new business models that substantially decrease environmental impact, reduce resource pressures, and produce a beneficial influence on society and the environment. Due to the necessity to change the essential components of the business and diverge from dominant business concepts, new circular business models are not yet widely used in practice [33,34]. It is generally accepted that the innovation process needs guidelines and a solid structure to define and focus ideas in order to help the business model design [35][36][37]. ...
... High removal efficiencies of over 92% of volatile solids, 98% of chemical oxygen demand, and 81% of total suspended solids were further demonstrated in an upflow anaerobic sludge blanket reactor for the digestion of brackish aquaculture sludge from an RAS (Mirzoyan et al., 2013). The use of aquaculture sludge as a fertilizer by direct land application (Bergheim et al., 1993;Yeo et al., 2004) or its use for compost production (Adler and Sikora, 2004;Danaher et al., 2011) both appear to be more sustainable alternatives, as long as the heavy metal content and salinity issues of the sludge are resolved. A vermicomposting technique was used to compost the effluent solids from an RAS together with shredded cardboard (Marsh et al., 2005). ...
... Aquaponics aims at remediating aquaculture effluents by combining aquaculture with hydroponics in a recirculating system where fish effluents are mineralized by beneficial microorganisms, including nitrifying bacteria, to provide nutrients for plant growth and clear the water of toxic elements for fish [141]. The development of microbial communities is promoted by the presence of a biofilter-a well-oxygenated compartment in which a large surface area allows colonization by microorganisms [142]. Aquaponics can thus be seen as a variant of bioponics, with fish effluents as the organic fertilizer. ...
... Ammonium-N removal efficiencies of 86% to 98% were reported from a constructed wetlands system receiving aquaculture wastewater (Lin et al., 2002). Each square meter of hydroponic growing area removed 0.83 g of total N and 0.17 g of total P per day (Rakocy, 1997 The ammonium preference of aquatic plants is substantial. For example, when Elodea nuttallii was placed in a mixture of equal parts ammonium and nitrates, the plant removed 75% of the ammonium within 16 hours while leaving the nitrates virtually Only when the ammonium was gone, did the plant begin to take up nitrates (Frank, 1991 and Hageman, 1980). ...
... Operational data on the commercial aquaponic system was collected from UVI through interviews with the facility manager and previous publications on the system (Rakocy et al., 2004(Rakocy et al., , 2009. Infrastructure inputs were collected through facility records denoting materials required to replicate the system. ...
... The water consumption in aquaponic systems is significantly lower than in traditional soil cultivation [8]. Aquaponic systems produce higher yields in less space, which is a huge advantage over traditional agriculture [9]. ...
... The subsystem will have more solid waste in the system; it can be faeces or the excess fish food. Excess solid waste increases oxygen demand leading to hypoxic conditions in the rhizosphere, and may generate toxic concentrations of ammonia and nitrite (Rakocy, 2012;Danaher et al., 2013).Therefore, proper solids management is necessary to maintain the oxygen gradient around the plant roots allowing for colonization of PGPMs and preventing phytopathogen growth. ...