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Fig. 15. (a) Frequency of migrants and non-migrants, plasma levels of (b) testosterone (T), (c) pituitary contents of luteinizing hormone (LH), (d) plasma levels of LH, (e) thyroxine (T4), and (f) triiodothyronine (T3) in control and T 500 μg/fish-treated 1+ immature fish, and 1+ precociously mature male sockeye salmon. In (c), unit of Y axis in the control group was ng/pituitary, while those of T-treated and precocious male groups was μg/pituitary. Numbers above columns in (a) indicate the number of migrants and non-migrants. N.S. represents no sample. Differences in the frequency of upstream behavior from the control group were analyzed by the Fisher's exact probability test, using StatView version 4.5 software (Abacus Concepts, Inc., California, USA). * and ** indicate a significant difference at P < 0.05 and P < 0.01 from the control group, respectively. Differences in mean plasma and pituitary hormone levels among experimental groups were analyzed by one-way analysis of variance (ANOVA) followed by Fisher's PLSD. Differing letters represent significant differences at P < 0.05 among all groups. Reprinted with permission from Fish. Sci., 78, Munakata et al., Involvement of sex steroids, luteinizing hormone and thyroid hormones in upstream and downstream migratory behaviors in land-locked sockeye salmon Oncorhynchus nerka, 81–90, Fig. 6, © 2012b, The Japanese Society of Fisheries Science.

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