Research Paper Volume 16, Issue 18 pp 12443—12472

Figure 1. Lower housing densities in the juvenile stage accelerate body growth. (A) Schematic diagram showing the housing conditions. The hatched fish were kept at five different densities until three wph: 1, 2, 4, 10, and 40 fish per tank. (B) The graph shows their body weight at 3 wph under the housing conditions represented in (A). Each point represents an individual fish. The data were obtained for 13-28 fish at each density from a single experiment. The data are shown as the mean ± S.D. **, p < 0.01 by Tukey test. (C) Images are representative images of three-week-old fish under the group housing (40 fish per tank) and single housing (one fish per tank). The lower panels show higher magnification images of the boxed areas in the middle panels. The black arrows indicate fin coloration. The black lines in the images are drawn at 1 cm intervals. Blue scale bars, 1 cm. (D) Body weights at six different juvenile growth stages from 9 days posthatching (dph) to the onset of sexual maturity (group-housed fish; 35 dph, single-housed fish; 21 dph). The data were obtained from four samples at each stage. The data are shown as the mean ± S.D. Each point represents an individual fish. The blue and pink italic numbers represent the six weight-based stages of body growth in group- and single-housed fish, respectively (see methods section for detail). Representative images of fish at each weight-based growth stage under group housing (40 fish per tank) and single housing (one fish per tank). The black lines in the images are drawn at 1 cm intervals. Blue scale bars, 1 cm. Sex was confirmed by the expression level of a female-specific gene, zona pellucida sperm-binding protein 3 (XM_015945764.2). (A–D) G: group-housed fish, S: single-housed fish.