Temperature control of pikeperch (Sander lucioperca) maturation in recirculating aquaculture systems-induction of puberty and course of gametogenesis

After temperature-induced puberty at 12 degrees C for 12 weeks, the progression of gametogenesis in maturing pikeperch (Sander lucioperca) was studied at 12 degrees C, 14 degrees C, 16 degrees C, and 18 degrees C, compared with a control group reared at 23 degrees C. The plasma concentration of the sex steroids estradiol (E2), testosterone (T), 11-ketotestosterone (11-KT), and 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20-P) as well as the histology of the gonad confirmed the successful induction of puberty in all treatment groups and an advanced gonadal maturation until the end of the experiment in both. After 16 weeks at 14 degrees C, 80% of the female pikeperch examined were in mid vitellogenesis compared with a slower progression at 12 degrees C, 16 degrees C, and 18 degrees C. After 20 weeks, all fish reared at 14 degrees C accomplished mid vitellogenesis accompanied by a significant up-regulation of E2, which was also detected in the conspecifics reared at 12 degrees C and 16 degrees C, although not as advanced. In females reared at 18 degrees C, only a small percentage reached mid vitellogenesis accompanied by decreasing E2 concentrations, succeeding the induction of puberty at week 12. After 20 weeks, the level of T as well as 11-KT peaked in fish of both sexes kept between 12 degrees C and 16 degrees C. As in females, temperature influenced postpubertal maturation in males, which was indicated by significant temperature dependent changes of the sex steroids. E2 plasma concentrations in males exhibited a bimodal pattern with two maxima, first after 12 weeks at the onset of puberty and the second after week 26, coinciding with the end of spermatogenesis as indicated by milt production. In conclusion, postpubertal temperatures around 14 degrees C promoted a complete ripening in pikeperch of both sexes within 8 weeks, whereas higher temperatures constrained full gonadal maturation. Furthermore, with reference to the optimal temperature for the induction of puberty previously discussed, slightly higher temperatures around 14 degrees C are optimal for postpubertal maturation. This clearly indicates the existence of a dynamic temperature influence for optimal maturation due to postpubertal inhibition of maturation at temperatures higher than 18 degrees C. Consequently, in addition to the role of low temperatures in the induction of puberty, this is the first evidence that emphasizes the need for a closely controlled temperature range to be maintained during the ongoing maturation, which should be considered in year round production of pikeperch. Crown Copyright (C) 2013 Published by Elsevier B. V. All rights reserved.