Cobia (Rachycentron canadum), a species of large pelagic finfish found in warm waters worldwide, is poised to become the “tropical salmon” for marine aquaculture. These delectable sashimi-grade fish are solitary and non-schooling so until recently, availability for human consumption was limited to sport fishing and accidental by-catch. Global wild-caught cobia in 2007 totaled only 10,484 metric tons as reported by sixteen countries. Although the cobia species has been reared experimentally for decades, large-scale commercial production has only emerged within the past ten years. Cobia have been farmed in Taiwan since the late 1990s, and recently farming operations have been developed in Panama and Belize as well as throughout parts of Southeastern Asia. In the last four years, China has surpassed Taiwan as the leading producer of farmed cobia. China first reported a harvest of 16,481 metric tons in 2003. In 2007, China produced 25,855 metric tons, more than six times Taiwan’s production of 3,998 metric tons for the same year. The combined production for 2007 was only 29,859 metric tons.
The widespread use of trash fish in feed is one of the most serious problems associated with cobia cage aquaculture in Asia. In China, Taiwan and Southeast Asia, cages are usually clustered in congested and pollution-prone urban areas near shore. Human waste constitutes another source of pollution where artisanal fisherfolk families live aboard the floating cages and pens. However, early breeding and farming success with cobia in floating pens and cages near shore has propelled the development of the improved concept of “open ocean” closed cage cultivation.
There are numerous advantages to farming fish in a high-energy open ocean environment including increased water flow, reduced accumulation of waste products, and decreased reliance on shore-based infrastructure and fewer user conflicts. Oceans span 70 percent of the Earth’s surface minimizing territorial competition. With sustainable “open ocean” farming technologies, cobia is expected to become a global commodity on a scale comparable to farmed salmon. Farmed cobia possess many advantages over salmon and other marine carnivores, including impressive growth rates and the potential to thrive on a diet low in fishmeal. Lethargic farmed cobia accumulate fatty acids so well that producers consider it to be a different product from wild cobia, which naturally has a lower fat content. Wild-caught broodstock adapt well to confinement and accept formulated feeds. Female cobia possess high fecundity producing more than 5 million eggs at a time and is some regions of the world they spawn naturally nearly year-round. In hatcheries constant spawning can be environmentally or hormonally induced for a reliable and steady supply of juveniles. Protein is the most expensive component of commercial aqua feeds representing more than half the variable costs of farm production. Plant-based protein sources are being investigated as a sustainable and cost-effective substitute or supplement to traditional fishmeal protein. Sources of plant-based feed substitutes, such as soy-based protein, are the most promising because of their nutritional profile, low cost and consistent availability.
Alternative protein sources already provide from one to two-thirds of the dietary protein in commercial cobia feed that is supplied during grow-out. Research has confirmed that soy-based protein can provide up to 40% of dietary protein in cobia feed without significantly affecting the feed conversion ratio, the protein efficiency ratio, or the net protein utilization. In the laboratory, 100% replacement of fishmeal protein in cobia feed has been achieved, but it is not yet considered cost effective for commercial-scale production. With the ascendancy of the tropical salmon, consider the descending $10 billion Atlantic salmon farming industry experiencing a 20 percent shortfall this year. Disease decimated the 31 percent salmon share produced by about 700 farms in Chile and a major environmental movement is undermining top producer Norway with 33 percent of global production. Citing unsustainable practices, the Target chain of stores recently stopped selling farmed salmon products nationwide. The public is becoming more aware that salmon farms have become excessively dependent upon pesticides and antibiotics to combat disease that are rampant in highly concentrated near-shore penned fish – not unlike industrial-scale hog, poultry and cattle on land. Consider the opportunity for a new paradigm with the “open ocean” sustainable farming of a species with three times the growth rate of the Atlantic salmon, with a food conversion ratio that allows them to thrive on soy feeds yet packs a whopping 1,880 mg of Omega 3s per serving – the tropical salmon.