Broodstock Redfish Handling Deaths at Aquaculture Facility

Broodstock Redfish Handling Deaths at Aquaculture Facility

In the l980s and l990s I was involved with several redfish aquaculture ventures in the United States as an advisor and scientist to assist them. I was a marine biologist that majored in fish parasitology/diseases under Dr. W. J. Hargis, Jr., and had extensive experience in holding, and rearing aquatic organisms. I was hired as a post-doctoral fellow by Dr. Gordon Gunter, an influence on my life and research. Part of this time as an advisor in various aquaculture projects I was Head of Experimental Organism Culture of a Toxicology Program and co-chairman of the Toxicology Program and the rest of the time I was Aquarium Supervisor of the J L Scott Aquarium in Biloxi. This was an advisory service of the state organization I was a member of during those times. We were in the initial stages of learning how to raise redfish and learned as we progressed along.

In the mid l980s one facility had built its broodstock tank and building and was ready to stock out adult redfish in order to obtain eggs. The personnel got adult redfish from a purse seine operation and transported them to a man-made pond on the grounds of the aquaculture farm. After those that were injured in capture and transport died, it was decided to be time to move the adults from the pond uphill to the holding facility.

The adult fish were coralled by pulling a seine in the pond, pulled into shallow water (where they became frantic and thrashed about), manually picked up and carried to a weighing-measuring table (they were dropped, and slime coat damaged), measured and weighed (beating tail on table, slid off table, etc.), manually carried (several tens of steps) to the brood tank, and put into tank water. I was mostly an observer/advisor during this operation as I did not want to be directly responsible, as a state employee, for the well-being of expensive fish belonging to a private venture plus I could not impose my ideas onto a private business (They could accept or reject my advice as they wished.). The owners of the redfish farm, their staff, and friends were the ones handling the operation and their procedures (which I presumed they had researched) were followed.

I had to bite my tongue on the excessive handling of the fish, and commented that they should be out of water as little as possible. For some reason they thought it necessary to get accurate readings of weight and length of the fish before they went into the brood tank. The fish were out of the water from pond to tank usually five minutes or more.

After about 35 fish were moved to the brood tank, the primary owner said he was glad that was done. I said he was not finished yet. He asked why. I told him that someone needed to get into the tank and pull out all the dead fish before they fouled the water. They did not want to believe me. The junior owner finally got down to his underwear and got into the tank, feeling around with his feet and hands. He was surprised when he found the first dead fish, and shocked when they got up to 12 dead fish. A few more died on following days.

After we had a pile of dead fish on the floor, the owners wanted to know why. I started opening them up. All 12 had bleeding from the blood vessels in the mesenteries of the digestive tract. The fish had the same problem beached whales get. When no longer supported (buoyed up) by water gravity takes over and internal organs "fall," causing ripping in the mesenteries and contained blood vessels, internal bleeding, shock, and sometimes death.

The rough handling, carrying, dropping, flopping on table, etc. caused internal bleeding and shock that some of the fish could not handle.

The owners should have transported the fish as quickly as possible to the brood tank and forgotten about weighing and measuring. They should also have carried the fish in wet slings for better body support, or in water if they could.

The facility succeeded in getting eggs from their remaining redfish, and raised redfish for several years before going out of operation.

We all learned from this .............


Adrian R. Lawler, Ph. D. (C) 2012 --