Abstract

Simple SummaryIncreasing demand for an efficient and economic fishmeal feed for sustainable aquaculture has urged the aquafeed sector to seek an optimum fish-feed formulation. This study investigated the physiological response in olive flounder fed various fishmeal diets in a typical fish farm. The fish were farmed for 20 weeks, using the following experimental feeds: a control feed (CON), a replacement by 20% (F20), and 30% (F30) of the fish meal content of the CON. All groups showed no significant difference in growth and survival rates. However, due to investigating hormone expression associated with maturation, high expression of PSS-I and low expression of FSH-β, ER-α, and ER-β in FM30 compared to other experimental groups were observed. Therefore, up to 30% fishmeal replacement does not affect growth, but it appears to have a slight effect on the sexual development of olive flounder.Olive flounder (Paralichthys olivaceus) is a commercially important and valuable species for aquaculture in Korea. Due to the unstable supply of fishmeal for farmed fish, an optimum fish-feed formulation should be researched to ensure the sustainability of P. olivaceus aquaculture. This study investigated the effect of three experimental diets: Con (basal diet); FM20 (20% fishmeal replacement of CON); and FM30 (30% fishmeal replacement of CON) on P. olivaceus over 20 weeks at a typical farm by monitoring the growth and factors relating to sexual maturation. The results showed that no differences in growth were observed between the CON and diet-replacement groups. Gonadal oocyte development was similar between the CON and diet-replacement groups. Moreover, sbGnRH and GH expression did not differ between the CON and diet-replacement groups. The levels of Erβ and Vtg expression were significantly higher in the FM20 group than in the CON and FM30 groups after the experimental period. The expression of PSS-I was significantly higher in the FM30 group than in the CON and FM20 groups. Therefore, although growth occurred when 30% of the fishmeal was replaced, such high dietary protein replacement may be ill-advised during the maturation of olive flounder at the commercial fish farm.

Highlights

  • Olive flounder (Paralichthys olivaceus) is the most cultured fish in Korea, accounting for 43,320 tons, or 51% of the 85,217 tons of the total fish-farming production in 2019 [1]

  • The growth and feed efficiency of olive flounder fed a proper fishmeal replacement are similar to those of fish fed traditional feed [11,12], research on the growth and sexual maturation associated with different food sources remains insufficient

  • The feed conversion ratio did not differ between the control diet (CON) and experimental groups (p > 0.05), and the feed conversion ratio of the FM30 group was significantly lower than that of the FM20 group (p < 0.05)

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Summary

Introduction

Olive flounder (Paralichthys olivaceus) is the most cultured fish in Korea, accounting for 43,320 tons, or 51% of the 85,217 tons of the total fish-farming production in 2019 [1]. It is considered an important and economically valuable aquaculture fish in Korea and. Feed is the major factor influencing the early growth, gonadal development, and sexual maturation of cultured olive flounder. The growth and feed efficiency of olive flounder fed a proper fishmeal replacement are similar to those of fish fed traditional feed [11,12], research on the growth and sexual maturation associated with different food sources remains insufficient. Recent studies on fish feed have attempted to substitute fishmeal and determine appropriate replacement rates

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