Survival of larval summer flounder Paralichthys dentatus on formulated diets and failure of thyroid hormone treatment to improve performance

Summer flounder is a new aquaculture species, the culture of which could be made simpler by the replacement, to the greatest extent possible, of live feed with formulated diets. Previous work has shown that development of the summer flounder stomach can be accelerated by treatment of the larvae with thyroid hormone. Two series of experiments were conducted. In the first ex periment, 2-week feeding trials were conducted beginning with fish (which w ere not treated with thyroid hormone) 14, 21, 28, 35, or 42 days after hatc h (DAH) to determine when they could begin to utilize commercially availabl e formulated diets. In the second experiment, two groups of sibling larvae, one treated with thyroid hormone, the other not, were placed in similar 2- week feeding trials at 25, 30 or 35 DAH to test whether survival of thyroid hormone-treated larvae would surpass those of untreated larvae. The first series of experiments demonstrated that the larvae could not effectively ut ilize the formulated diets until 35 DAH. The second series of experiments i ndicated that thyroid hormone-treated larvae do not exhibit significantly g reater survival than untreated larvae.