Hormonal Growth Promotion and Evidence for a Size-Related Difference in Response to Estradiol-17β in Yellow Perch (Perca flavescens)

Abstract

Our studies indicate that estrogen(s) promote growth and may mediate sexually related dimorphic growth in yellow perch (Perca flavescens). (1) Neither 17α-methyltestosterone (MT) at 1.5–60 μg/g diet nor estradiol-17β (E2) at 15–120 μg/g stimulated length or weight gain when fed for 85 d to age 0 perch that were initially 20–35 mm total length (TL) and 0.14–0.25 g total weight (TW). (2) In larger age 0 perch (initially 90–110 mm TL and 8–12 g TW), E2 at 2 or 20 μg/g accelerated length and weight gain; MT, triiodothyronine, and zeranol failed to promote growth at all doses tested. (3) E2 at 20 μg/g had differential effects when fed for 84 d to age 0 perch (initially 30–50 mm TL and 0.5–0.7 g TW) and age 1 perch (initially 90–110 mm TL and 8–12 g TW): E2 stimulated weight gain in the larger fish within the first 28 d, but did not improve growth in the smaller perch until they reached 80–100 mm TL and 5–10 g TW (after day 56). These results demonstrate that E2 promotes perch growth only after a certain size- or age-related maturational status has been reached. We suggest that this status is related to the onset of spermatogenesis, vitellogenesis, and sexually related dimorphic growth and may be linked to the maturation of hormone receptors.