According to Watanabe, Summer flounder populations declined from 23.5 thousand metric tons in the mid-1980s to 9 thousand metric tons in the early '90s. If you inject fish with hormones you have to physically handle them. Our operation shows that you can take wild adult broodstock out of the ocean and provide the conditions necessary for them to spawn naturally that same year. Dr. Harry Daniels, a larval culture specialist at North Carolina State University, supplied wild adult southern flounder, obtained through commercial sources, for the project. Dr. John Burke of the National Marine Fisheries Service in Beaufort also donated broodstock for the study.
Freshwater fish produce large eggs with a lot of yolk.
By the time the yolk is eaten, freshwater fish are developed enough to be fed a commercial fish chow. That's why freshwater aquaculture is well established, whereas, marine aquaculture is still in the embryonic stages. Marine finfish produce small eggs with small yolks. When their yolk is used up, they must be fed microscopic algae and zooplankton. The upshot is that the requirement for these tiny organisms is a difficult task to meet.