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Sustainable Fisheries

Sustainable Fisheries

Aquaculture System Overview: Hybrid Striped Bass in Earthen Ponds


Hybrid striped bass (HSB) are a cross between the freshwater white bass and the anadromous striped bass. They are considered as a small component of the US aquaculture industry but attracting significant investment in recent years—in 2018, 4,344T of foodfish were sold, valued at nearly $33M. HSB are raised in recirculating systems (RAS), open ponds, and cages. Like any agriculture production system, HSB operations require inputs including capital, land, and water resources.  They also require development of output markets that have been thoroughly sourced and researched.  Identifying and evaluating output market demand with respect to product quantity and product characteristics is a critical element of aquaculture financial planning.  A “MARKET FIRST” approach can help investors maximize aquaculture business opportunities by developing an integrated business plan that matches production resources, species, and systems with output market requirements.

Organism: Hybrid Striped Bass

Overall HSB aquaculture operations are divided into two or three phases. In a three-phase-system, fry are stocked into a hatchery pond and raised to fingerlings with average weight of 1g (0.035oz). The second step is to grow the fingerlings to advanced fingerlings with a weight of 125-225g (4.4-7.9oz). These fish are then grown to market size in the third step. The two-phase-system, or “directstock,” eliminates the second step by stocking 3g (0.1oz) fingerlings directly into grow-out ponds.

HSB tolerate a wide spectrum of temperatures (39-86℉). Growth occurs above 59 with an optimum temperature of 77-80℉. Fish spawn at 64-68 and stop feeding at 48℉. The fish will endure dissolved oxygen levels as low as 1 ppm but the optimum range is 6-12 ppm. Desired water quality parameters include pH of 7.0-8.5 and hardness/alkalinity >100 ppm.

During hatchery phases, fish are fed 40-45% protein #3 crumbles and increasing to a 3/16-inch pellet as the fish grow. Progressively, pellet size is increased to 1/8-inch and 3/8-inch, still at the high protein levels. For the end of the growth period, fish are shifted to a ¼-inch pellet of 38-40% protein. Reported food conversion ratios (FCRs) cover a wide range from 1.5 to 5.7.

Harvest size is generally at an individual weight of 1-2 pounds (450-900 g), requiring 15-20 months depending on the harvest weight. Gilled and gutted fish dress-out at about 85% while dress-out for skinless fillets is 32%. In the directstock method, fish are stocked at a density for grow-out of 3,750-4,000 fingerlings per acre.

Production Methods: Earthen Ponds

Earthen ponds are one of the most common and oldest ways of raising fish. Ponds impound water—water sources being ground water, surface water, or wells. Water may be delivered by gravity or pumping. In nearly all cases the intent is to establish a static environment that is optimal for the fish being cultured. The success of the pond operation is highly dependent upon the selection of the site to build the pond—water of a suitable quality and quantity, good quality impermeable soils, and a topography that minimizes construction costs. Construction costs at well-chosen sites will range from $3,000-5,000/acre—with costs reaching or exceeding $8,000/acre at more challenging locales. Water costs may be important with evaporation the major loss from well-built ponds—estimates of losses ranging from 1-3in/week at good sites.

Earthen levees must be well built; depending on local conditions, sometimes with built-in features to minimize leakage. However, lining ponds (e.g., with clay or plastic) is very costly both in terms of initial costs and maintenance and must be carefully assessed before using. The footprint of the levee must be considered when determining the land area ended to build a pond of a desired water-surface area. For example, a levee with an average height of 8ft and a crest width of 12 feet will have a footprint of 50-60ft2 for every linear foot of levee. Pond draining may be done by gravity or by pumping. There are a variety of drainage structures, some constructed of concrete and other using PCV pipe.

Pond size and number will depend upon the management scheme planned for the facility.  If hatchery operations are undertaken on the farm, there will need to be several relatively small nursery ponds to supply stocks for larger grow-out ponds. Ultimately the harvest will be determined by the surface area of these grow-out ponds and their capacity needs to be tied to the market. Growers often expect yields of 4,000-5,000lbs/acre.

Unique to Oregon

HSB have been previously introduced into Oregon ( ). However, culture permits are required from the Oregon Department of Fish and Wildlife ( ). For outdoor pond culture, temperature is a crucial factor. Seasonal temperatures at the farm site are important—days with temperatures below 60℉ will result in little if any growth. Since aquaculture is a conditional use in Oregon, it is necessary to check with local and state authorities. Similar homework is necessary regarding water use. The interface for land and water is the watershed; both at the local and basin levels. For operators purchasing HSB fingerlings, out-of-state seed suppliers are available (seed suppliers). For out-of-state purchases, there will likely be additional regulations. HSB feeds can be purchased from several mills (feed mills). HSB, though a relatively new product for Oregon markets, seems to be a versatile protein source ( ).

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Authored by John Moehl (2021)