Research Index

Aquaculture of Cobia Rachycentron canadum in Closed Systems

Jeffrey M. Lotz, Ph.D.
John T. Ogle, M.S
James Ballard, M.S. Student

Aquaculture of cobia in offshore cages is a rapidly growing industry. The large marine fish, also known as lemonfish and ling, is a popular sport fish and menu item in restaurants. In the wild, cobia can grow to about 12 pounds and 25 inches in a year. Their natural habitat is over the continental shelf and offshore reefs as well as bays and estuaries. GCRL research is addressing a serious bottleneck to development of the fledgling industry in the United States, the lack of onshore marine aquaculture production systems that can supply the developing offshore industry.

Long-term research and development goals

• To develop spawning protocols to supply a reliable source of larvae
• To optimize larval rearing to supply fingerings for stocking offshore cages
• To develop an onshore grow-out system to produce market-sized cobia

Cobia at GCRL

• GCRL research has built a knowledge base about cobia age and growth, reproduction and seasonal movements.
  http://www.usm.edu/gcrl/fisheries_center/research.php
• GCRL efforts in captive spawning of wild-caught cobia date back to 1993
• Cobia have been raised to approximately 2 lbs (800 gram average) in 275 days at densities up to 40Kg/m 3 in a closed recirculating system.
• A new zero-exchange system is being developed at the Cedar Point campus to grow the fish to market size. Zero exchange is a closed system with no new water added during culture.

Funding partner

• The National Sea Grant College Program

Cobia fingerlings arriving at the GCRL from the Aquaculture Center of the Florida Keys
The cobia were shipped in one-cubic-meter hauling boxes that had approximately 200L of water in them. Four of these boxes were used to move the 5000 fish.
The fish were stocked in to 84-liter aquariums at five different densities with five replications of each density.
Fish were also stocked into five-foot-diameter circular tanks that were filled with 1000 liters of water. The tanks and aquariums were all recirculating on the same water supply.
Throughout the experiment the water quality in the system was maintained by both mechanical and biological filtration .
Eight water quality parameters were measured daily to ensure that there was no difference in water quality between densities. Differences in water quality may lead to false findings.
Fish were raised in the aquarium system for 240 days at which point they were averaging 500 grams and about 18 inches long. The small picture was the fish at time of stocking and the large one was taken at day 150.
On day 256 the fish were moved from the GCRL’s main campus to a newly designed system at the Cedar Point campus .
The new facility is a zero-exchange system that incorporates six 3000-gallon raceways. In this system we plan to grow the fish to market size.
The new filter system utilizes mechanical, chemical and biological filtration in order to maintain ideal water quality even under high loads .