Full-Cycle Net Pen Studies
By Langley Gace
I am excited about the three small full-cycle net pens built and deployed by the ICA in Carlsbad, California in cooperation with Hubbs Sea World Research Institute and the American Soybean Association.
The ICA and its project partners are interested in the use of the small full-cycle grow-out nets for developing regions in Asia — and throughout the world. The trial pens are 2 x 2 x 2 m in dimension with 2 mm wire and a 6 mm mesh opening. Full scale pens are 3 x 3 x 3 m. Farmers can now stock juveniles (2 to 3 grams) that will grow to market-sized fish, eliminating the need for nursery nets. These pens were built on land. Two people built the third pen in less than 45 minutes. Workers connect the panels using traditional fasteners like nuts, bolts, and lock washers. The assembly requires only common wrenches. Small pen construction benefits intended users:
- All tools required to build the net pens are available in developing countries.
- Fasteners in the net pens are made with alloys similar to those used in the manufacturing of the pens, reducing corrosion.
- Minimal infrastructure is required to move or transport these pens.
Hubbs Sea World researchers are working with us, using hatchery fish to test how juvenile white sea bass (Atractoscion nobilis) will grow in the small mesh pens. This research is part of an ongoing white sea bass wild stock enhancement program initiated by the Institute. We are interested in how the small mesh will work in a marine environment. Hubbs scientists will measure water quality studies in addition to charting growth-rates, food conversion, and copper uptake in fish flesh. Scientists will test six cages; three of copper-alloy netting and three of traditional nylon netting used as controls. All data from this study will be peer reviewed, then published. See recent video of the full-cycle copper-net pens in Carlsbad, California.
Based on lessons-learned in the California trial, the ICA will initiate studies in Vietnam – a country that has a large quantity of fishery cooperatives consisting of small, family-run operations where in-water net cleaning devices are not available. Predator control presents a challenge in these markets as well. Rats chew through nylon nets placed on docks for cleaning on land. Because of its strength and durability, copper-alloy mesh protects fish inside the copper-net pens. This feature also makes Vietnam a viable choice for initial trials of copper-alloy netting.
In late September, the ICA began preliminary site investigations. We visited with government officials and farm trade associations to determine suitable species and sites for the trial. Similar trails are currently underway in Mozambique with tilapia. While tilapia is a freshwater fish, the ICA will conduct saltwater trials in Vietnam.