Aquaculture: Cobia

A fish capable of growing to 6 feet, 132 pounds, and living as long as 12 years may sound like a difficult animal to grow, but aquaculture of the cobia, Rachycentron canadum, has been very successful because of this fish’s fast growth rates and excellent quality of flesh. China is the main producer of farmed cobia, but cobia aquaculture is expanding in the west with operations in the United States, Mexico, and the Caribbean.

A female cobia which will be used for broodstock, photo: Dr. Daniel Benetti, NOAA Photo Library.

Cobia are large, predatory fish that inhabit warm marine waters around the world. They are usually countershaded, with dark brown backs and white bellies. A dark band, bordered by two lighter bands, extends from the eye to the tail fin along the side of the body, which resembles a slightly flattened cylinder.

Cobia broodstock were initially captured from wild populations. Now, 1.5 -2-year-old cobia are chosen from existing stocks for spawning. Cobia broodstock are kept in recirculating or flow-through tank systems where they spawn year-round. Fertilized eggs are collected and transferred to nursery ponds to hatch, and the larvae are fed small crustaceans called copepods or microscopic animals called rotifers. As cobia grow, they are introduced to feed pellets. Weekly, the cobia are sorted by size to reduce cannibalism and ensure survival of stocks. At around 75 days old, cobia are transferred to near-shore or offshore grow out cages where they are kept until harvest. Challenges facing cobia aquaculture include overloading the surrounding environment with nutrients, disease, and escape of stocks.

The process of culturing cobia, from: http://www.fao.org/fishery/culturedspecies/Rachycentron_canadum/en

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links please go to ocean.tamu.edu and click On the Ocean.

Script Author: Danielle DeChellis

Contributing Professor: Dr. Lisa Campbell

Editor: James M. Fiorendino

Featured Image: https://www.fisheries.noaa.gov/species/cobia

Aquaculture: Tiger-Tail Seahorse

The Tiger tail Seahorse, Hippocampus comes, is one of the most visually striking creatures in the ocean. Consequently, they are a prime target for the aquarium trade. Unfortunately, these animals are also collected and processed into pills to be sold in China to address a variety of maladies. 20 million seahorses may be caught each year to support the health supplement market in China. In addition to overfishing, habitat destruction also threatens populations of tiger tail seahorses. Import and export of tiger tail seahorses has been regulated since 2004 by the Convention on International Trade in Endangered Species.

Tiger tail seahorses grow to just over 6 inches long and make their homes on corals or sponges in the western central Pacific Ocean. They are usually yellow or black in color, with alternating stripes running down the length of their body. This pattern of stripes makes them difficult for predators to see clearly.

The above flowchart shows the process of culturing Tiger Tail Seahorses, from: http://www.fao.org/fishery/culturedspecies/Hippocampus_comes/en

Currently, tiger tail seahorses are grown in Vietnam to supply both the aquarium trade and health supplement market in China. Aquaculture of tiger tail seahorses begins with the collection of broodstock from wild populations, which are kept in cages in calm waters. During spawning, females transfer their eggs to male seahorses’ pouches. Baby seahorses, called fry, are born after 10-20 days. Seahorse fry are collected and moved to small indoor tanks where environmental conditions can be extensively monitored and controlled. In these tanks, fry are fed copepepods and brine shrimp for around 40 days. Next, fully-grown tiger tail seahorses are transferred to larger indoor tanks or back to cages in bays. They are allowed to grow to acceptable for sizes for sale, usually about 3 inches, which takes approximately 3 months.

Tiger Tail Seahorse fry being grown in a tank. From: http://www.fao.org/fishery/culturedspecies/Hippocampus_comes/en

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links please go to ocean.tamu.edu and click On the Ocean.

Script Author: Arthus Copeland

Contributing Professor: Dr. Lisa Campbell

Editor: James M. Fiorendino

Featured Image: https://www.earth.com/animals/tiger-tail-seahorse-hippocampus-comes/

Aquaculture: Atlantic Salmon

Salmon runs are a major event in Alaska and the Pacific North West, when these anadromous fish return to the rivers where their lives began to spawn. Once, salmon runs were common on the East coast of North America, as well. The Atlantic salmon, Salmo salar, could once be found in almost any river north of the Hudson River in New York; aggressive commercial fishing severely depleted populations of Atlantic Salmon before their closure in 1948. Today, only a handful of wild United States Atlantic Salmon can be found in rivers in Maine. Canadian and European populations of Atlantic Salmon are declining, as well, and all Atlantic salmon sold commercially comes from aquaculture. 

from: http://www.fao.org/fishery/culturedspecies/Salmo_salar/en

Salmon eggs are obtained from broodstock, a population of adult fish reserved for reproduction. Once fertilized, atlantic salmon eggs are incubated at a nursery until they hatch. Newly hatched salmon, called fry, are closely monitored and given vaccinations to preserve their health as they grow into parr. At about 18 months, parr undergo considerably physiological changes that allow them to survive in salt water. At this stage they are about 5 inches long and are called smolts. Smolts are moved to floating nets in mid-April or May. Open-water pens are a practical way of maintaining Atlantic salmon stocks in salty water they need to survive, and the exchange of water in the pens with the surrounding environment removes waste and supplies oxygen-rich water for the salmon.

Though there has been considerable success in farming Atlantic Salmon, many challenges remain. In particular, salmon aquaculture may threaten wild populations and the surrounding environment through excessive nutrient loading and pollution or the transmission of diseases should any stocks escape.

Atlantic salmon production, from: http://www.fao.org/fishery/culturedspecies/Salmo_salar/en

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click On the Ocean. 

Contributing Professor: Dr. Lisa Campbell

Script Author: Judson Riley

Editor: James M. Fiorendino

Featured Image from:

Aquaculture: Nori

Nori is the Japanese name for seaweed and a common component of sushi. Nori is made using red algae belong to the genus Porphyra; it is shredded and dried into sheets which are used to wrap sushi rolls.

Dried sheets of Nori, as would commonly be used to wrap sushi rolls. From: https://upload.wikimedia.org/wikipedia/commons/b/be/Nori.jpg

Porphyra grows on rocky coasts around the world. They are capable of surviving periods of total dryness, and are often found at the upper edges of intertidal zones. Blades can range from less than an inch to several feet in length.

Porphyra have a complex life cycle; The thallus, or body, of Porphyra you can see in a tide pool, produce male and female cells which are released into the surrounding water. Male cells fertilize the female cells, forming spores, which are themselves released into the water before settling and boring into shells, where they grow into a filamentous mass called a conchocelis. The conchocelis, under certain conditions, release spores that will grow into a new blade.

Life cycle of Porphyra yezoensis, from Takahashi and Mikami (2017). https://www.frontiersin.org/files/Articles/238074/fpls-08-00062-HTML-r2/image_m/fpls-08-00062-g001.jpg

Aquaculture of nori is most common in China, Japan, and Korea, but is growing in North America. A two-stage process is required to grow nor because of its complex life cycle. During the first stage, usually between May and October, the filamentous conchocelis stage nori are placed in a reservoir with seawater and nutrients to induce spore production. Following this phase, temperature and light intensity are manipulated to induce the release of spores, which are collected on nets; when spore release reaches are certain threshold, light intensity is increased to encourage growth of the thallus stage of Porphyra. Once settled on nets, Porphyra are grown in the sea or intertidal waters, and harvested after 40 or 50 days.  

Porphyra ready for harvest, from: http://english.jschina.com.cn/PhotoGallery/201203/t966519.shtml

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links, please go to ocean.tamu.edu and click “On the Ocean.

Contributing Professor: Dr. Lisa Campbell

Script Author: Martha Navarro

Editor: James M. Fiorendino

Featured image from: https://upload.wikimedia.org/wikipedia/commons/3/36/Porphyra_umbilicalis%2C_Porphyra_purpurea_Helgoland.JPG