Increasing economic and environmental sustainability of aquaculture production systems through aquatic plant culture

Increasing economic and environmental sustainability of aquaculture production systems through aquatic plant culture

Summary

Aquaculture in the Northeast is dominated by three primary production technologies: raceways, recirculating systems and ponds. These systems are relatively expensive to operate and are faced with increasing environmental regulations associated with effluent management. Species diversification, shifting to higher value species, integrating additional crops and polyculture are all useful strategies for farms to improve profitability. Aquatic plant culture for ornamental and restoration markets has proven to be an emerging industry with high value crops. In addition, aquatic plants can be an important means of nutrient uptake. Delaware State University (DSU), University of Maryland and West Virginia University are collaborating to demonstrate the potential economic and environmental benefits of integrating aquatic plant culture with aquaculture.

This project will provide aquaculture producers in the Northeast an opportunity to understand the variety of aquatic plant species and their market potential; learn how to integrate plants into their production systems through tiered workshops, training and applied research and demonstration projects utilizing the three productions systems: raceways or flow-through (WVU) , recirculating tank systems (UMD) and ponds (DSU); understand the economic potential by review of economic analyses of each demonstration project; and receive implementation support through targeted technical support programming.
The three system projects will be directly applicable to over 420 fish producers in the Northeast who employ one of the three culture systems, and secondarily to state and federal fish hatcheries. Through a series of milestones, including plant market surveys, workshops and training, tours, and implementation instruction and support, Farmers will be able to evaluate this integration approach for integrating aquatic plant production in their operations and increase farm income through plant sales and reduce nutrient concentration of their farm effluent. In 2007, the integrated fish/plant demonstration projects were conducted for a second year in all three states. Information on project objectives, plant species and markets, and 2007 preliminary results were presented at three workshops and directly to farmers and others touring the systems.

Objectives/Performance Targets

Of the 420 aquaculture producers in the Northeast who utilize either raceways, ponds or recirculating systems and are included in project activities, 15 will implement aquatic plant culture in their operations reducing nutrient concentration in culture system effluent and increasing farm income through sales of plants. By adding aquatic plant component to their operations, farmers will benefit by: a) wisely utilizing nutrients from aquaculture effluent typically considered a liability, but instead will serve as fertilizer for aquatic plants; b) increase farm diversity by the additional sales of marketable aquatic plants which in turn will; c) increase farm sales and enhance profitability, especially since aquatic plants achieve a greater profit margin than foodfish; d) reduce the off-farm nutrient discharge thereby being more environmentally sustainable; and e) produce plant species that are used for food, ornamentals in water gardens or in mitigation projects in urban or construction areas.

Accomplishments/Milestones

Information on the project objectives, plant species, integrated system design and benefits, and plant market survey results were presented at three workshops in early 2006. These locations included Delaware, Maine and West Virginia with over 120 people attending. The three integrated system demonstration projects were conducted from May to October and production results were analyzed and presented to 44 people in early December at the Northest Aquaculture Confenrece and Exposition held in Mystic, Conneticut. Tours of the demonstration systems have been provided to over 100 people in 2006.

Impacts and Contributions/Outcomes

The plant market survey identified that over 125 species as either tubers, bare root or potted in 4 and 6 inch or gallon pots, are sold as ornamentals in the water garden markets. Wholesale prices for these products ranged from $2.00 – 19.00 depending on size and quantity.
Over 270 species of plants (some of the same species sold as ornamentals)are sold for restoration or mitigation projects. For this market plants are sold as 2 inch plugs, pint or 4-6 inch pots. Wholesale prices ranged from $0.27-3.50 depending on size and quantity.

Prelimary results form the three individual demonstration projects are as follows:

Delaware –
DSU researchers evaluated the effectiveness of integrating two aquatic plant species, Swamp Hibiscus (Hibiscus moschuetos) and Iris (Iris versicolor), into pond based baitfish (Fundulus heteroclitus) aquaculture, one of three pilot scale research/demonstration systems. Plant and fish growth, water quality, plant nutrient uptake, and cost of operation were monitored for use in the development of an economic analysis. For our pilot scale project, water from one baitfish production pond was diverted through six aquatic plant channels.

Weekly water samples were collected from each plant channel inlet and outlet, and analyzed for nutrients. Plant growth was assessed monthly via wet weight measurements. In addition, initial and final plant tissue samples were collected and tested for nitrogen (TN) and phosphorus (TP) to determine nutrient uptake rates.

Although the changes in nutrient levels between plant channel in-flow and out-flow were not large enough to be statistically significant, there was a clear trend towards a reduction in total phosphorus as affected by plant uptake. Similarly, both the Swamp Hibiscus and the Iris appeared to thrive in the integrated system, increasing in weight by more than 50% and 55%, respectively.

Maryland-
A pilot-scale demonstration project including culture of two brackish water plant species integrated with a recirculating tank system producing striped bass was operated from May to mid September 2006 to evaluate the effect of the aquatic plants on nutrient remediation of the fish effluent. Plant and fish growth, plant influent and effluent water quality (ammonia, nitrate, plants were floated using rafts in shallow plant channels allowing bare root contact with water to maximize nutrient uptake. Plant biomass of 3.6 and 4.1 kg/m2 was observed with Hibiscus and Spartina respectively which is approximately twice values observed in improved/restored marshes. Nitrogen and phosphorus uptake for Spartina was also twice that of restored marshes and hibiscus was observed to uptake 40.6 and 44.3% more nitrogen and phosphorus than spartina. The six plant channels removed approximately 15.4% of the nitrogen and 9% of the phosphorus applied in fish feed.

West Virginia-
Aquaponics is part of the WVU aquaculture system at the Reymann Memorial Farm near Wardensville, WV. Effluent flowing out of the last raceway is pumped to an adjacent greenhouse where it is distributed via a manifold to the plant channels. The greenhouse permits growth of plants throughout the year and protects them from insect pests.

During the experiment, the system supported 6000 to 8000 lb of brook trout fed a commercial diet (42% protein, 16% fat) six days a week. Solid waste from raceway quiescent zones was diverted directly to the pond.

Both iris and hibiscus grew slowly in this system. Nutrient removal was negligible. This was most likely due to low nutrient concentrations in the water and low water temperature. Plants most suitable for this type of system appear to be those hardy to zone 4 and those most productive early in the year when temperatures are low. Other experiments have shown that cool season crops such as watercress and lettuce grow well in this system.

Collaborators: