National Marine Aquaculture Intiative Project Summaries for 2004

High Rate Algal Systems for Sustainable Marine Bivalve Seed and Shrimp Co-Production

State: SC

Principal Investigators: D E. Brune, A.G. Eversole, Kendall Kirk, and Antonio Aranguren, Clemson University

Abstract: The Clemson University Partitioned Aquaculture System (PAS) was combined with a Suspended Culture, Extended Aeration, Nitrification/De-nitrification (SEA-N) reactor for control of ammonia-nitrogen concentration in a shrimp culture system fed at sustained levels approaching 750 lb. feed/acre day, at a shrimp carrying capacity in excess of 250 shrimp/m2. The combination of photosynthesis and chemoautotrophic nitrification offers a number of advantages for application to zero-discharge, aquatic animal production systems. Algal growth allows for solar driven oxygen production and nitrogen uptake. The added nitrification function provides ammonia detoxification capacity during extended cloudy periods, and an expanded capacity to remove ammonia production at rates far exceeding photosynthetic capacity (greater than 12 gm C/m2 day, corresponding to 350 lb. feed /acre day). The addition of de-nitrification capacity to the system provides further advantage in countering alkalinity destruction from the nitrification reaction, and in addition, preventing excessive accumulation of nitrate-nitrogen concentrations within the system. The PAS/SEA-N technique offers the advantages of "greenwater production" at productivities far in excess of conventional intensive aquaculture systems, while avoiding the high cost of fixed-film, or media intensive, biofiltration techniques.

The combined PAS/SEA-N process was operated (in the 2004 growing season) for culture of the Pacific White Shrimp (Litopenaeus vannamei) at densities ranging from 250 to 300 animals/m2. Feed application rates reached 750 lb. of 35% protein feed/acre day, with projected standing crops ranging from 20,000 - 25,000 lb. shrimp/acre. System dissolved oxygen levels ranged from 3 to 6 mg/l, while total ammonia-nitrogen concentrations averaged 1.5 mg/l with peaks of 2.0 mg/l. Nitrite-nitrogen concentrations averaged 0.5 to 1.0 mg/l, with peaks of 1.5 mg/l. System total nitrate-nitrogen levels reached a maximum of 100 mg/l. System salinity averaged 12 gm/l. Secchi disk visibility was maintained within a range of 10 to 15 cm by use of continuous water exchange (at one day detention in each shrimp unit) between three shrimp units and a single Nile tilapia unit (Oreochromis nilotica). System pH ranged from a minimum of 7.0 to 7.5 at maximum feed application rates. Freshwater was added to balance evaporative losses however, water was never discharged from the system.

In addition to using tilapia for algal density control, the potential use of oysters for control of algal standing crop was also investigated in 2004. The primary limiting factor in using the eastern oyster (Crassostrea virginica) to control algal density in this modified PAS operation was found to be the high algal and bacterial cell densities (100 to 150 mg/l volatile solids), and the need for frequent and aggressive cleaning of excessive oyster pseudofeces. A solution to the algal density and cleaning issue was found in control of hydraulic detention time in containerized populations of oysters, employing a cyclic, automated, dumping of water from the containers, followed by use of an aggressive, automated, rotating spray bar to wash attached solids from the oysters, with wash-water discharge into a settling tank. Algal uptake kinetics of the containerized oysters was quantified, with estimated preliminary uptake rates as high as 1000 mg algal C /kg hour at 28o C.

Demonstrating hatchery and offshore growout technology for production of Cobia (Rachycentron canadum) and Florida Pompano (Trachinotus carolinus) from egg to market.

State: FL, PR, Bahamas, Brazil

Principal Investigators: PI: Daniel D. Benetti; Co-PI: M. Refik Orhun; Collaborators: Ruth Francis-Floyd, Kenneth Riley, Brian O'Hanlon, and Philippe Douillet.

Abstract: User conflicts and pollution concerns suggest that major environmental benefits are to be gained by moving cage aquaculture operations further offshore. Emerging technology is being used to demonstrate the environmental sustainability and economic viability of raising hatchery-reared cobia (Rachycentron canadum) in collaboration with the private sector (Snapperfarm, Inc. and AquaSense LLC) using submerged cages in exposed sites in Puerto Rico (US) and the Bahamas.

Sampling stations were set up both near and far and both upstream and downstream from fish cages in the Bahamas and Puerto Rico. Possible eutrophication of the local environment was evaluated monthly by measuring dissolved nitrogen and phosphorus, phytoplankton biomass, epiphyte growth potential, sinking flux of organic matter into sediment traps, organic content of the sediments, and benthic microalgal biomass. In all cases, no significant differences were found between near and far or between upstream and downstream sampling stations. Environmental data from Puerto Rico and the Bahamas indicate that the current regime and resulting dilution of nutrients from the submerged cages do not lead to a significant change in the ecosystem near the cages.

Cobia exhibit extraordinary growth (4-6 kg/12 months), yielding 1 kg of fish biomass when fed 1.8 kg of pellets containing 50% fish meal (FCR = 1.8). Taking into account that energy loss between trophic levels in nature (90%) results in ecological efficiency of only around 10%, our data shows that using fish meal to produce high-value fish for human consumption in aquaculture can be 3.7 times more efficient than this transformation in nature. Results suggest that growing cobia in exposed sites with adequate depth and currents can produce high yields of seafood for human consumption with low environmental impact.

Aerial photo of hurrican eye over research site.

Photos of the Aquapod cage system beneath the surface and just above the surface.

December 2006 Update

Environmental and technical assessment of alternative shellfish production methods.

State: Washington

Principal Investigators: Dan Cheney and Ralph Elston (Pacific Shellfish Institute), Jonathan David (Taylor Resources Inc.), Robin Downey (Pacific Coast Shellfish Growers Association), Carter Newell (Great Eastern Mussel Farms), John Richardson (Blue Hill Hydraulics), Tessa Getchis (Connecticut Sea Grant Extension Program), Dror Angel (Massachusetts Institute of Technology) and Mark Luckenbach (Virginia Institute of Marine Science).

Abstract: This project assesses environmental and technical aspects of cage and bag-on-bottom, bag-on-rack or bottom suspended oyster and clam culture, net-protected or enhanced clam culture methods. Specific guidance for modifications and improvements will be determined for these methods. The project also assesses the effects of these practices on Submerged Aquatic Vegetation (SAV). All research is to be conducted by collaboration between representatives of the East and West Coast shellfish researchers and industry participates and will meet the 2010 Goals. Specifically, high priority goal 4.3.2, "Identify gaps in current understanding of shellfish ecology specific to West Coast ecosystems and pursue research to fill those gaps. The final goal is to gain a clear understanding of the ecological impacts associated with: Oyster and Clam culture. The proposed work will also satisfy the research priorities of the Northeast Regional Aquaculture Center and the East Coast Shellfish Growers Association.

Objectives include:

Characterize and quantify the effects of alternative shellfish culture methods on eelgrass.
Assess and compare benthic infauna and epifauna species, juvenile salmonids, shrimp and crab diversity, density, and biomass within and adjacent to shellfish culture and reference sites.
Determine sediment and water column interactions associated with culture method and compare with undisturbed conditions.
Model carrying capacity, phytoplankton concentrations, and sedimentation for different submerged and floating aquaculture methods and planting densities.
Evaluate existing culture methods in terms of environmental impact and develop recommendations and guidelines for modifications to existing growing methods in order to reduce adverse impacts, maximize positive environmental effects and improve production efficiency.

Tasks completed to date (September to December 2004):

Collected fall samples of macro-infauna, macro-epifauna and priority epibenthic organisms for 5 separate culture techniques at 2 Washington sites.
Applied for species collection permits through Washington Department of Fish and Wildlife, NMFS, and USFWS.
Developed modeling needs worksheet for the duration of the project.
Initiated collection of site information of Washington, Virginia, and Connecticut sites.

An Assessment of the Environmental Impacts of Marine Shellfish Aquaculture In the USA (Poster in PDF 231 KB)

Beneficial floating reef effects of marine finfish mariculture.

State: Pacific Northwest

Principal Investigators: Jack Rensel, Rensel Associates Aquatic Science Consultants; John Forster, Forster Consulting Inc. Graduate Student: Henry Valz

Abstract: The objective is to identify and measure the extent of colonizing plants and animals that occur on nets, lines and floats at a marine finfish farm in North Puget Sound. These facilities provide a unique floating reef habitat for many organisms which we are classifying into food-web functional groups. Fish assemblages are also being qualified with respect to general location and diet preferences. These data will compliment existing information about impacts and/or benefits of floating aquaculture systems to benthic macrofauna populations.

Specifically :

Performing estimates of seasonal plant and animal abundance and biomass, with emphasis on the late spring through summer algal growing and invertebrate recruitment season.
Qualifying colonization patterns on clean nets, floats and line substrates by periodic sampling and underwater photography.
Estimating wet weights, dry weights, and carbon-nitrogen content of many repetitive sets of biofouling specimens that will be the basis of a standing stock estimate of biomass.
Beginning to assess the use of stable isotope analyses of nitrogen and carbon to discern the relative importance of wastes from the farm for biofouling organism subsistence.
Performing a qualitative, relative abundance estimate of fish species occurring adjacent to the fish farm.

Since starting in July 2004, accomplishments include:

Deployment of a separate reference-float assembly complete with clean floats, anchor lines, and netting strips for colonization study.
Removed or cleaned in situ many walkway floats or sections of nets for colonization study.
Monthly underwater photographic documentation of colonization for all types of substrates noted above.
Intensive sampling of the biofouling standing stock in late summer of fish containment netting with different sun exposure aspects and copper content.
Similarly intensive sampling of walkway floats including different exposure to currents and light.
Limited sampling of anchor lines and anchor locator (crown) lines from multiple depths.
Digital underwater video documentation of all surfaces and biofouling of predator netting biofouling during summer months.
Enumeration of several hundred thousand individual specimens with concurrent wet and dry weight estimates.
Preservation of samples from treatment and reference locations for stable isotope analysis.

Pictures show sampling of walkway float (left) and replacing netting after sampling (right).

Executive Summary PDF (155KB)

Caprellid shrimp removed from netting (photo by Michael Womer).	Wet weight colonization results for invertebrates and algae on net pen floats.	Underwater photograph of caprellid shrimp on netting. Jassa spp. amphipods are present in high numbers too, but too small to show in most photographs.
Prolific growth of Costaria costata on walkway float in summer 2004.	Mean seasonal biomass for algae versus invertebrates on differing substrates.	Dense biocolonization of sabellids tube worms on a anchor “crown” line that had been in place for several years. (Svein Weise Hansen, farm co-manager alongside line).

Measurement of the benthic loading and the benthic impact from an open-ocean fish farm in tropical waters.

State: PR, FL

Principal Investigators: Patrick D. Rapp* and Wilson R. Ramírez, University of Puerto Rico; Larry E. Brand, University of Miami; José A. Rivera, NOAA Fisheries PR; Daniel D. Benetti, University of Miami

Abstract: This proposal is concentrated on the measuring the environmental impact of the Snapperfarm cages west of Culebra. There are 2 objectives. (1) monitoring the benthic loading and the benthic impact at Snapperfarm site, extending the environmental baseline previously established. (2) Pilot scale testing of new monitoring methodologies. For loading, use of sediment traps with aspect ratio greater than eleven. For impact, utilize rapid response of benthic microalgae (abundant in the tropics) to an infusion of nutrients. Pilot tests in both sediment and benthic water. Goal is to demonstrate that in the tropics microalgae signal eutrophication much earlier than the usual benthic monitoring techniques, at substantial cost savings. Further, to establish quantitative endpoints suitable for NPDES process.

We establish a transect along tidal axis, in current direction, out to 100m. Four stations; take 4 samples at each station: 2 in the sediment and 2 in the water, relate organic loading to algal impact. In the sediment, dual cores, one for algae and one for composition analysis. In the water, epiphyte monitors and sediment traps. Far distant from the transect are "garden plots," small areas deliberately seeded with known feed densities, to obtain response curves. Sample monthly.

For open-ocean mariculture, environmental impact sets a limit, and relevant impact is in the benthos. The EPA proposed rule focuses strongly on the benthic footprint. Continual monitoring is an essential Best Management Practice. The NPDES process allows the permit writer to use Best Professional Judgment. The usual benthic chemical analysis is not available at the remote Snapperfarm site (Culebra). These novel monitoring methodologies, based on high-aspect ratio traps and rapid microalgae response to loading, could enable NPDES permits in tropical waters, establishing that monitoring protocols may be very different at different locales. Wherever applicable, the rapid microalgae response will be much quicker to alarm for eutrophication, at greatly reduced cost.

The Hawaii offshore aquaculture research project phase IV: Scale up to carrying capacity in the offshore environment.

State: HI

Principal Investigators: Charles W. Laidley, (PI) University of Hawaii; Charles E. Helsley, University of Hawaii; and John Randall Cates, (Commercial Collaborator),

Abstract: It is now well recognized that natural fisheries in the U.S. and around the world can no longer meet increasing demands for fish and fishery products. The DOC and NOAA have identified research into offshore aquaculture as a top priority to address sustainability of U.S. fisheries, and to provide new economic opportunities for the responsible use of ocean resources. In 1999, the University of Hawaii (UH) teamed up with the Oceanic Institute (OI) and Safety Boats Hawaii with support from the State of Hawaii's Aquaculture Development Program to initiate the Hawaii Offshore Aquaculture Research Project (HOARP). In earlier phases of this collaborative project, researchers successfully addressed many of the initial biological, economic, and environmental issues relating to the suitability of offshore aquaculture in Hawaii. Further, this effort led to the establishment of Cates International, Inc. (CII; a derivative of Safety Boats Hawaii), the first offshore fish farm in the U.S. which currently produces weekly around 5000 lbs of market size Pacific threadfin, also known as moi (Polydactylus sexfilis). The two major priorities for continued development of the offshore aquaculture industry are (1) to secure commercial scale numbers of marine finfish fingerlings (>2M/yr) through advanced hatchery technologies, and (2) to determine the environmental effects (if any) and carrying capacity of open ocean cage farms for use in development of best management practices and regulatory oversight. Further, these two priorities are inextricably linked, as it is not possible to address issues of environmental sustainability and carrying capacity without achieving commercial scale fingerling supplies to the offshore cages. These efforts are critical to making marine finfish aquaculture both economically and environmentally sustainable in the U.S.

The following work plan addresses multiple program priorities including research, demonstration, local and national regulatory issues, education and outreach. The main objectives of this project are to:

1) Resolve bottlenecks in hatchery production to meet fingerling requirements for economically viable scale commercial operation
2) Provide critical environmental data around sea cages operating at full commercial scale to provide information on the carrying capacity of offshore cage operations
3) Transfer derived technologies and information to industry and governmental agencies.

Fingerling production efforts will focus on current bottlenecks in the marine finfish hatchery that have led to an undersupply of fingerlings for stocking in offshore cages. Focus will be on the Pacific threadfin (Polydactylus sexfilis) since it is the only species being farmed in multiple offshore cages. Resulting technologies will also be applicable to other marine finfish species. Critical areas include disease prevention, high-density live feeds production, improved larval survival and reduction in postlarval size variation that leads to cannibalism. With a growing requirement for fingerlings, and an immediate need to start up new marine finfish hatcheries, it is crucial to develop and demonstrate modern hatchery technologies similar to that used in the high-output European seabream and seabass industries.

The first area of focus is prevention of vertical pathogen transmission from egg to hatchery. Egg disinfection will be examined as a practical and easily scalable method to prevent pathogens (bacteria, viruses, parasites) from transfer from broodstock to fingerlings. Disease-related losses during early hatchery are particularly difficult to detect due to the small size of marine finfish larvae. Small-scale experiments have demonstrated the efficacy of hydrogen peroxide in egg disinfection but the approach requires validation and optimization prior to application in the commercial setting.

There is also a need to implement more efficient hatchery technologies that allow the scale-up of production and the realization of critical economies of scale without increasing hatchery size, water requirements, effluents, and labor. The first requirement is the implementation of continuous high-output algal and rotifer production systems to efficiently and reliably meet the live feeds requirements of commercial hatcheries. There is also a compelling requirement to examine larval rearing protocols to increase overall hatchery survival including examination of first feeding protocols and optimization of the early larval rearing environment. Finally significant improvements in overall hatchery yield are likely to be gained through Artemia replacement diets. Improve larval nutrition would reduce size variability leading to lower rates of cannibalism in the late hatchery and early nursery phases. The project will also examine the application of water recirculation technology to increase nursery density and reduce water use and disposal requirements. Increased hatchery yields will allow offshore cage operations to attain the needed scale of operation and provide incentive for private industry to invest in hatchery facilities.

Environmental monitoring around the cage will consist of three activities focused on gathering environmental data around the CII fish farm. The monitoring efforts include water quality monitoring at the Zone of Mixing boundary and in the near-field and within the cages as the fish population grows; monitoring total organic carbon of the sediments and the infauna of the sediments under the cages, in the near-field (~100 meters from the cages), and in the far-field (~500 meters from the farm); and study of the particulate discharge from the farm (begun under HOARP phase III) using an array of sediment traps.

Water quality measurements will continue to be made quarterly to provide assurance that increased farm size is not providing a significant impact to the water column. At the present time, all stations more than 500m from the cage are indistinguishable from the background. This project will continue to examine the physical and chemical characteristics of the discharge plume downstream of the farm. These data provide information about the diffusion of the discharge plume as well as its vertical mixing downstream of the cages.

Benthic studies will assess the nature of the changes that are occurring beneath and around cages. During the proof of concept phases of HOARP (Phases I and II) changes were observed that correlated with presence or absence of fish in the cages, with original conditions being reestablished within 6 months of the end of the experiment. During Phase III, under conditions of a continuously operating farm, systematic changes to the benthic biota from an assemblage characteristic of nutrient impoverished environment to an assemblage characteristic of nutrient enriched environments were observed beneath the cages. Systematic monitoring will continue as fish biomass increases at the site and at additional sites shoreward of the cages in order to establish the extent of changes in the bottom assemblage. Sediment traps have been deployed and this monitoring will continue in order to determine the particulate flux coming from the cages. The goal is to determine the proportion of particulates derived from sources including feces, fines and uneaten feed, and organic debris shed from the cage by natural processes or from cage cleaning.

Technology transfer beyond manuscripts, presentations and reports will include a stakeholder meeting convened at the new OI Information Technology & Training Facility to convey research results to end users, determine continuing industry needs and assist in regional planning and prioritization of future efforts.

AQUACULTURE INFORMATION CENTER - DOC/NOAA