Clownfish can reportedly lay clutches of over 1000 eggs. Image by Roger Williams University.

Old McDonald had a farm – EI-EI-O, and on that farm he had some tropical marine fish.  EI-EI-wait, what?

Old McDonald is now into aquaculture.

Aquaculture is the rearing of aquatic animals and plants by people. It is farming in fresh water and salt water.

People like to keep fish as pets and see them in aquariums. 

The aquarium trade in fish and other aquatic organisms is worth billions of dollars. Most of the fish in the aquarium industry are bred through aquaculture, and most of these fish are freshwater fish rather than marine fish. Most marine fish in the aquarium trade are caught in the wild.

Glassy sweepers are also sometimes called copper sweepers for their copper-colored scales. Image courtesy of the New England Aquarium.

Catching wild marine fish can have negative effects on both the captured fish and their habitats. 

If the trip from ocean to tank takes too long, fish can become stressed, and can even die. Harmful collecting practices for marine fish can harm ecosystems already struggling with overfishing, coral bleaching, warming waters, and other climate change impacts. 

An example of a harmful marine fish collecting method is cyanide fishing. Fishers stun the fish with a poison called sodium cyanide before packing them tightly with other fish in bags for shipping. The poor conditions and the lingering effects of the cyanide poisoning can kill the fish and cause damage to the remaining fish populations in the reefs.

An aquaculture team is breeding marine fish.

The team – from the Roger Williams University in Bristol, Rhode Island and the New England Aquarium in Boston, Massachusetts – are trying to raise marine fish for aquariums so that they won’t need to be collected from the wild. So far, the collaboration has reared 17 species of fish, including five never before raised in captivity: the blue chromis (Chromis cyanea), brown chromis (C. multilineata), glassy sweeper (Pempheris schomburgkii) and queen triggerfish.

Juvenile fish swim in tanks at the wet laboratory and breeding facility at Roger Williams University. Image courtesy of Roger Williams University.

Marine fish are challenging to raise.

Aquaculture takes on a new level of complexity when dealing with marine fish. Unlike freshwater fish, which have relatively simple breeding systems, marine fish rely on complex variables like currents and ocean temperatures to tell them when to breed. Even if experts can create the right conditions, marine fish are challenging to raise. Having the right food for the fish is crucial.

In time these aquaculturists hope that their efforts will lead to captive breeding of marine fish that lessens the demand for collecting them in the wild, thus meeting the needs of the aquarium trade and lessening environmental problems sometimes caused by collecting marine fish in the wild.

Weedy sea dragons (Phyllopteryx taeniolatus) cling to a piece of their enclosure. The program has yet to successfully breed the species in captivity, but doing so remains a major goal of the Larval Fishes Aquaculture program. Image courtesy of the New England Aquarium.

Adapted from an article by Ashley Stumvoll, published on