Marine Shrimp in Indoor Tanks
Interest in tank-based shrimp production systems has been increasing in recent years in North America. Factors driving this trend include proximity to markets and the ability to offer fresh product to consumers. This strategy also encourages competitiveness by reducing cold chain costs and markups imposed by intermediaries, both of which drive up the cost of product for consumers in most parts of the U.S.
In temperate regions, buildings can be retrofit for shrimp production from other uses but electrical distribution and outlets must be upgraded for outdoor conditions and with ground-fault interrupt circuits. Floors can be as simple as sand and gravel or concrete with trough drains, but in temperate areas walls and ceilings must be highly insulated. Adequate ventilation, and preparation and sealing of indoor structural surfaces, are also crucial to reduce damage from mildew and humidity.
When considering raising shrimp in indoor tank systems, both technical and economic factors must be addressed. Many functional configurations exist but profitability depends on capital costs, operating costs, survival rates, growth rates and market conditions. Equipment options and management expertise impact both technical and economic feasibility. In North America, some successful operations are extremely limited in size, but to be competitive most small-scale producers need to offer a comparatively large product (>20g or 0.7 oz. average weight).
Small-scale indoor shrimp producers are utilizing both recirculating aquaculture systems (RAS) and biofloc systems (relying on a suspended ‘floc’ of bacterial colonies to process nitrogenous wastes). Both approaches require salinities of 15 to 20 parts per thousand resulting from mixing salts to create artificial seawater). Both approaches allow growers to conserve water (and the associated costs for heating and salt) over the course of the production cycle. Harvest rates in RAS in the U.S. typically range from 4 to 7 kg (9 to 16 lb.) per m3 per cycle.
The nursery phase for tank-cultured shrimp currently uses 2000 – 3000 post-larvae (P-L’s) per m3. Feed (a crumble diet formulated for shrimp) is offered at 15% of the weight of the shrimp per day – spread out over 16 to 24 hours. This amount is decreased to roughly 3% by the end of the first month, but shrimp biomass will be increasing as the feeding rate is decreasing. Over the past decade post-larvae have been available from several hatcheries in the U.S. but there are usually only a few to buy from at any given time. Sourcing P-L’s has been especially difficult in recent years due to hurricane impacts on hatcheries and temporary USDA closures due to disease issues.
When shrimp reach 1 gram they are moved to grow-out tanks at 250 per m3, and 80% survival is a reasonable goal. An average growth rate of 1.5 g per week is typical, requiring some 12 to 13 weeks to attain a premium size of 20 g. With more variable yields, biofloc may provide better feed conversion under some conditions but the RAS approach is generally more energy efficient, easier to manage and exhibits more stable water quality on day-to-day and seasonal bases. Biosecurity has occasionally been cited as a problem in RAS, as is increased vulnerability to equipment failure and the resulting back-up equipment requirements.
Although there are many unique configurations currently in operation, certain ‘typical’ characteristics are emerging as the U.S. industry grows. Concentration and removal of solids is required, as is some form of biofiltration. Some less expensive tank options such as above-ground swimming pools may not be sufficiently durable for long-term use, and some of these can also contain toxic compounds intended to prevent the growth of mildew or algae. High costs associated with ready-made fish culture tanks can preclude profitable production, but in almost any part of the country suitable tanks can be constructed in-house using a variety of local materials. If HDPE liners are available tanks can be constructed of lumber or welded wire with fitted liners. Many designs, photos and illustrations can be found on-line.
Energy efficient regenerative blowers and uninterrupted electrical service are essential for both RAS and biofloc shrimp production. Blower performance curves must provide sufficient volume for operating depths. Aeration should be sufficient to prevent solids from settling on the tank bottom and to maintain 5 ppm of DO at all times, with roughly 200 lpm of air for every kg of daily feed. Similarly, pumps should be installed based on total operating head (which must be calculated on a case by case basis) and required flow rates, with a cushion of 20% to accommodate any unforeseen requirements. And while modest levels of excess capacity are usually desirable, when plumbing both air and water systems configurations should allow for back-pressure to be alleviated to prolong the usable life of blowers and pumps.
In temperate zones, a constant temperature of 27 C represents a trade-off for heating costs, growth and reduced stress. Ground-coupled heat pumps or water heaters with closed PEX loops work well to circulate warm water through submerged hoses. Salinity of 20 ppt is also a good trade-off for water quality maintenance, shrimp health and operating costs. Salt can be mixed from various components on-site, at lower overall cost than pre-packaged mixes.
Ventilation must be designed to conserve heat during the winter, while still controlling moisture levels to prevent mold and corrosion. Carbon dioxide often accumulates in poorly ventilated buildings and this can impact the health of both the shrimp and the farm staff. If a building is well insulated, heating the air instead of the water will also help reduce humidity and moisture–related problems.
Lighting should be installed in such a way as to allow for gradual brightening and dimming to avoid startling and stressing shrimp. Most growers appear to prefer LED lighting with a spectrum suitable for growing plants, and recent research suggests continuous lighting can improve growth, survival and feed conversion efficiency.
While commercial sources of P-L’s generally have excellent bio-security practices and shipments can be expected to arrive free of any diseases of concern, health problems can still arise during grow-out as a result of poor water quality or rough handling. This issues can be minimized through regular monitoring of the shrimp and the system performance, and remedial measures can often reduce or limit losses.
Although by no means a complete list, the 2018 USDA Census of Aquaculture reported marine shrimp farms in 13 states. Although farms were reported from Florida (11), Hawaii (10), Texas (4) and Alabama (1), the total included 13 indoor farms in temperate regions such as Colorado and Minnesota.
When planning an indoor marine shrimp farming facility it will be necessary to calculate the carrying capacity of the system in order to estimate capital costs, projected production, revenues and input requirements (especially P-L’s and feed). At this point, an evaluation can begin in order to determine if the operation will be large enough to generate profits and if so, a market analysis can be undertaken. Markets must be available to accommodate production when it is ready for harvest because maintaining shrimp beyond a premium harvestable size requires excessive feed, labor and energy costs as well as unproductive use of facilities and capital.
In some states, a number of regulatory issues must be addressed before undertaking this form of aquaculture. Most states have strict licensing and permitting requirements for culture and sale of aquatic species. Transport of shrimp to live markets in other states may also require special permits for every state that will be crossed along the way.
Live markets, especially in Asian communities, are a potentially lucrative outlet for live shrimp, but problems with handling and transport mortality make this marketing strategy particularly problematic. For most indoor shrimp producers, a more practical approach has involved selling whole animals on ice. This avoids a number of regulatory questions governing processing and sales of shrimp that have been processed in any way.
Developing and maintaining committed relationships with both suppliers and buyers will be crucial. Potential markets include restaurants, wholesalers and direct sales to consumers. No matter what the scale of production will be, shrimp producers must provide value through quality control, grow-out / harvest scheduling and superior customer service. In turn, customers must also be willing to provide reliable outlets for marketable shrimp when the producer needs to move them.
Projected costs (variable, fixed, marketing and opportunity costs) must be compared to prevailing market prices for the sizes and quality of the shrimp that will be produced. However, in many cases there will not be any comparable local product in terms of fresh, premium head-on shrimp. Keep in mind that smaller operations will tend to have higher per-shrimp costs and will require a number of small-volume, local markets that are willing and able to pay higher prices. When a small operation loses a customer, alternatives may be limited or nonexistent.
Input suppliers (feed, P-L’s and equipment) must be reliable and trustworthy, even when larger customers are competing with your operation. Considerable attention must be paid to projected feed requirements – who will supply it, at what cost, and in what quantities will it be delivered? Bulk delivery will only make sense if the entire quantity can be used before its quality begins to deteriorate, a scenario that will be uncommon at this point in the development of the industry. However buying feed in bags will invariably raise production costs.
The key to marketing success for indoor shrimp producers in areas far removed from traditional commodity shrimp suppliers will be the ability to offer large, high quality, never-frozen, head on product on a consistent basis. This product is unique and can be marketed in such a way as to completely avoid competition from imported commodity shrimp, but advertising and promotion will be necessary as harvests begin in order to make potential customers aware of the product’s availability.
Prepared by C. Greg Lutz, Louisiana State University Agricultural Center