Hybrid Grouper: How to Produce A Tasty Yet Vulnerable Fish

By Heather Sadusky

Grouper ranks as one of the tastiest fish in the sea. Grouper sandwiches adorn the menus of restaurants on every coast of Florida and the fish is very common in the Caribbean. It is also highly demanded in Asia, where it is not only considered delicious but some species are prized for good luck or medicinal value.

This vast appetite has had a significant impact on grouper stocks globally, which generally speaking have taken a blow. They are large fish that take many years to reach reproductive maturity. Often the largest individuals are most prized by fishers, but we’ve since learned that they are also the best breeders, producing the most successful offspring, and should be kept in the ecosystem. With recreational and commercial limits, groupers are making a comeback, at least in the U.S. However, such restrictions also impose limits on consumption.

The aquaculture company Aqquua LLC has recognized the consumer demand for a delicious but vulnerable fish, and has taken on the challenge of optimizing grouper aquaculture production. They’ve decided the best grouper species for the aquaculture setting is a hybrid: male Epinephelus lanceolatus (giant grouper) and female Epinephelus fuscoguttatus (tiger or brown marbled grouper). The giant grouper is the largest reef-dwelling fish in the world according to IUCN. It occurs throughout Indo-Pacific range, and is considered rare and vulnerable to exploitation. Tiger grouper have been identified as capable of being cultured, but are still extensively taken from the wild. It is also a species inherently vulnerable to fishing according to IUCN. Both species are valued in the live fish trade, primarily in SE Asia and China.

The combination of these two grouper produces a fish that Aqquua calls king grouper. The venture has been launched in Thailand, where most aquaculture is extensive with limited technology and few controls on water quality. Aqquua is raising the standard, though, with the construction of a new hatchery that utilizes top of the line technology and aquaculture practices, as well as a high-tech RAS system. This is where they will determine if the hybrid is well suited for aquaculture, meaning a healthy fish that grows quickly.

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Hybrid grouper specimen (credit: Piyawut Mitrananda)

To help make this happen, a University of Miami graduate student is spending his summer in Thailand to determine the best feed for these king grouper. Piyawut Mitrananda is comparing three feeds to see which diet performs best in terms of fish growth and health by sampling growth during the nursery period when the fish are 10 to 50 grams. He tracks the size of the fish through total length, fork length and weight, taking these measurements once a week. Also of interest is the analysis of each diet – identifying how much protein, carbohydrates, fat, moisture, etc. are in a particular feed, and determining how those levels relate to growth performance. Piyawut will assess the feed conversion ratio (FCR) and fish-in fish-out ratio (FIFO) for each feed, which will tell him how much king grouper is produced for how much input. The more grouper that can be produced with less feed means a higher sustainability. Of course price will also be a factor in selecting one of the three feeds to be used to grow out the hybrid grouper.

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Feeding time for hybrid grouper in Thailand (credit: Piyawut Mitrananda)

Time to reach market size, which ranges from 600 – 700 grams depending where the fish is sold, is approximately 10 months from hatching. Aqquua currently has a sample batch of king grouper at market size, though they will not yet be sold. The company is exploring which markets are best to sell their king grouper, pending successful trials, and and has so far identified the live market in Hong Kong and fresh markets in North America as most promising. While it may be in the beginning stages, aquacultured king grouper has the potential to produce a delectable fish at a high level of demand. Keep an eye out, king grouper may be on a menu by you in the near future.


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