Aquaculture in Singapore can be categorized as land-based and sea-based. In 2019, Singapore produced...
Fish Farming in Land-Based Closed-Containment Systems
The Aquaculture Innovation Workshop #5 – An International Summit on Fish Farming in Land-Based Closed-Containment Systems was hosted by The Conservation Fund Freshwater Institute, Tides Canada (TC), the Gordon and Betty Moore Foundation (GBMF) and the Atlantic Salmon Federation (ASF) at the National Conservation Training Center (NCTC) in Shepherdstown, WV, 4-6 September 2013. This international summit provided an opportunity for aquaculture producers, scientists, engineers, aquaculture industry suppliers, regulators and investors to communicate progress on the technical, biological and economic feasibility of culturing fish – particularly salmon – to food-size in land-based closed-containment systems.
Over 130 participants from industry (the largest contingent), academia, non-government organizations (NGOs), and government attended to share scientific results and commercial experiences, identify opportunities to advance the use of technology and address industry myths. High interest in this timely and relevant topic meant attendees traveled from far corners of the globe, with speakers representing Norway, Denmark, Australia, Canada, Chile, Israel, the Netherlands, Germany and additional attendees traveling from Ireland, Poland, Switzerland, South Africa, Sweden, and throughout North America. The Summit included land-based aquaculture producers, representatives from large international salmon farming companies, engineers from the design industry and representatives of groups intending to build closed-containment systems to farm food-size salmon.
As a collective group, the Summit attendees are pioneering the technologies necessary to increase finfish aquaculture production in a manner that is more environmentally sustainable and economically viable. A major outcome was that emerging aquaculture technologies were highlighted for attending senior-level decision makers in government, industry, the financial community and philanthropy. Across the diverse participants, this catalytic meeting brought together a community of stakeholders and created a focused communication space critical for increasing the adoption of land-based closed-containment systems using water recirculating aquaculture system (RAS) technologies.
The two-day Summit consisted of invited sessions discussing innovations and challenges surrounding food-fish production, particularly salmon, in land-based closed-containment systems. Session topics included:
- salmon health and performance in land-based closed-containment systems (4 presentations)
- eliminating off-flavor from fish produced in closed-containment systems (2 presentations)
- denitrification and microbiology (4 presentations)
- assessment of alternate production systems for salmon farming (3 presentations)
- closed containment project updates (6 presentations)
- lessons learned while engineering and building commercial RAS (3 presentations)
- creating value from the waste stream (2 presentations)
- design innovations and opportunities in land-based closed-containment systems (3 presentations, plus panel).
There was also a presentation on research advances towards more sustainable alternative Atlantic salmon feed by William Wolters from the U.S. Department of Agriculture Agricultural Research Service (USDA ARS) and an update on the Department’s aquaculture research strategies and priorities by Jeffrey Silverstein (USDA ARS), the Department’s National Program Leader in Aquaculture.
Salmon Health and Performance in Closed-Containment
A presentation by Bendik Fyhn Terjesen of Nofima, Norway opened this session with the new findings about the effects of water salinity and exercise on post-smolt Atlantic salmon in land-based closed-containment systems. Fish performance indicators can be significantly improved when Atlantic salmon smolt are cultured to 1 kg at salinities of 12 ppt when compared to full-strength seawater. This presentation was followed by a discussion from Jeff Richards (University of British Columbia, Canada) about the University of British Columbia’s InSEAS Research program to determine optimal salmon rearing conditions in RAS. InSEAS new, replicate state-of-the-art water recirculating systems can be operated in a nearly closed-manner at various temperatures and salinities. Coho salmon and Atlantic salmon post-smolt performance studies are imminent, with temperature and salinity two of the initial variables to be studied at this new facility.
The final two talks in this session were from Christopher Good and Steven Summerfelt, both from The Conservation Fund Freshwater Institute (TCFFI, USA). Dr. Good discussed the effects of water exchange rate and water treatment processes on hormones (cortisol, testosterone (T), 11-ketotestosterone (11-KT), progesterone, and estradiol) in RAS containing sexually maturing Atlantic salmon. Findings of this USDA ARS-funded research suggest that, under the conditions of this study, the quantified hormones (except for T) do not accumulate in lower exchange water recirculating systems, and that, aside from 11-KT, the system’s unit processes do not impact hormone concentration.
Dr. Summerfelt closed the session with a synopsis of TCFFI’s several Atlantic salmon grow-out trials in land-based, freshwater, closed-containment systems. Last year, 23 mt of food-size Atlantic salmon were produced at the Freshwater Institute; this was an extremely large-scale research undertaking, albeit a tiny fraction of commercial production goals at sites like the ‘Namgis First Nation’s salmon farm (Canada) or Langsand Laks (Denmark). In TCFFI’s most recent growout trial, Atlantic salmon were reared under near ideal water quality conditions to a mean harvest size of 4.3 kg by 22 months post-hatch and a mean harvest size of 5.6 kg by 27 months post-hatch. Feed conversion during the production trial averaged 1.07 and, importantly, no major negative fish health events occurred (no viruses, sea lice, or kudoa parasites) despite zero employment of vaccines, formalin, antibiotics, or pesticides. Overall mortality accounted for about 7% of the population during the grow-out production phase, which included fish culled due to fungus. These studies suggest it is technically and biologically feasible to raise Atlantic salmon to food-size in closed-containment systems, even in freshwater at locations remote from the ocean.
Eliminating Off-Flavor from Fish Produced in Closed-Containment Systems
Two presentations described technologies and practices to eliminate earthy/musty off-flavors sometimes encountered in RAS-produced fish. Niels Jorgensen (University of Copenhagen, Denmark) presented procedures for reduction of off-flavors caused by MIB and geosmin in rainbow trout from RAS in Denmark. John Davidson (TCFFI, USA) reported on three studies examining depuration procedures to mitigate off-flavor from harvest-size Atlantic salmon. The depuration process for these fish was optimized by using standard operating procedures that provided clean and relatively biofilm-free systems during a 7 to 14-d depuration period. Biofilter media should not be used within depuration systems due to off-flavor bacteria and compounds present in associated biofilms. In addition, pre-disinfection of depuration systems using 250 mg/L H2O2 appears to enhance offflavor removal.
Denitrification and Microbiology in Closed-Containment Systems
Four presentations focused on the water quality issues of denitrification and microbiology within land-based closedcontainment systems. Lars-Flemming Pedersen (DTU Aqua, Denmark) opened the session with a discussion of microbial interactions (particularly nitrifying bacteria) with RAS water quality. The session then shifted towards denitrification with Keiko Saito (University of Maryland, USA) describing anaerobic waste treatment to remove nitrate and biosolids within zero-flushing land-based closed-containment systems for marine warm-water species. Likewise, Jaap van Rijn (Hebrew University of Jerusalem, Israel) described the importance of an anaerobic treatment stage for removing nitrate, phosphate, and off-flavor compounds. Both scientists described actual facilities that use innovative technologies to operate with practically no water flushing or waste discharge. Although they presented different technologies, both scientists described processes used to digest and hydrolyze biosolids (i.e., manure, waste feed, sloughed biofilm) within the RAS to generate organic acids that serve as a carbon source to fuel heterotrophic denitrification. These technologies mitigate nitrate accumulation without flushing the system with new makeup water.
TOP, FIGURE 1. Hoop building installation in April 2013 at the 100 mt land-based steelhead model aquafarm at Taste of BC in Nanaimo, British Columbia (Photo: Steven Summerfelt/The Conservation Fund). BOTTOM, FIGURE 2. The ‘Namgis First Nation’s “Kuterra” land-based salmon farm uses five 500-m3 dual-drain culture grow-out tanks connecting to a central water treatment system (Photo: J.R. Rardon).
Dr. Saito also described how the University of Maryland process could be used to produce hydrogen sulfide to drive chemoautotrophic denitrification. Volumetrically the anaerobic digestion basin described by Jaap van Rijn might equal approximately 20 percent of the total RAS volume and, in addition to nitrate removal, phosphate is deposited within this basin largely as hydroxyapatite [Ca5(PO4)3(OH)]. Moreover, geosmin and MIB are strongly bound to the anaerobic sludge in the basin and the sludge’s internal biological activity removes these off-flavor compounds. In the final denitrification talk, Laura Christianson (TCFFI, USA) described nitrate removal using relatively low-cost and simple woodchip bioreactors. Such bioreactors have been used to treat agricultural tile drainage but are now being trialed for treatment of RAS discharge in TCFFI research funded by the USDA ARS and Tides Canada. The woodchips provide a surface area for the growth of heterotrophic bacteria that utilize the wood’s carbon to fuel denitrification.
Assessment of Alternate Production Systems for Salmon Farming
Brian Vinci (TCFFI, USA) and Trond Rosten (SINTEF, Norway) co-presented a comparative economic and environmental analysis of land-based versus net-pen salmon production for a 3,300 mt/y Atlantic salmon model production facility. This volume is approximately 1 percent of the Atlantic salmon consumed in the U.S. annually. The land-based system was based on grow-out trials conducted at TCFFI, whereas the net-pen model was based on conservative estimates using data sets from Norway and an investment plan for establishment of a 3,300 mt/y production (headon gutted; HOG) open pen facility (small-scale open-pen farm). Findings indicated the cost of production was approximately equal for land-based and net-pen production at US$ 4/kg of head-on gutted product. Fixed capital investments associated with building facilities were greater for the land-based system, but the required site license costs in Norway brought the overall costs of the two options more in line. The 10-year net present value analysis showed that rates of return were approximately equal (15 percent) under likely scenarios where land-based produced salmon achieved a price premium. A life cycle assessment indicated that land-based production would have a larger carbon footprint than net-pen production if the former were sited to use electricity provided by a typical US mix of fossil fuels. However, if fossil fuels are replaced with hydropower, the carbon footprints of the two production options were approximately equal. Net-pen salmon production in Scandinavia followed by airfreight export to the US had a slightly larger carbon footprint than land-based salmon production in the US using fossil fuels. The environmental value of escapee prevention, fish pathogen exclusion, and disease minimization was not quantified, but could potentially benefit a land-based system. It is likely that a variety of technologies, including hybrids of the options compared here, will be used in the future.
Following this comparative analysis, Andrew King (University of Tasmania, Australia and University of St. Andrews, Scotland) presented an evaluation of production expansion options for the Tasmanian salmon industry. The use of land-based closedcontainment systems for at least a portion of the Tasmanian production period could reduce production costs and risks associated with existing production methods.
Svein Martinsen (Nekton AS / Smola Hatchery and Smolt Farm, Norway) closed the session with an assessment of floating closed-containment Atlantic salmon farming systems. His company is investing in a floating bag technology to rear Atlantic salmon smolt from 100 g to 1 kg. This technology aims to draw water to pass through the bag from far below the water surface to minimize sea lice infestations and provide
Read the rest of this article in the March 2014 issue of World Aquaculture Magazine here
About Steven Summerfelt and Laura Christianson
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