Fig. 5. Plasma levels of follicle-stimulating hormone (FSH), testosterone (T), 11-ketotestosterone (11KT) and estradiol (E2) in chum salmon in the central Bering Sea and the NW Pacific Ocean, 2001–2003. Fish were divided into immature fish and maturing adult I and II, as shown in the inset in Fig. 3. Values are means ± s.e.m. n.d., not determined. Significant differences among groups are identified with different letters (P<0.05 one-way ANOVA and Tukey's test). See Table 1 for the number of fish.