An opportunity arose to obtain humphead wrasse Cheilinus undulatus specimens between 2006 and 2009 from Indonesia, the major source and exporting country of this species, making study on its early gonad development possible for the first time. Protogynous hermaphroditism, previously proposed for this species, was confirmed in this study. Based on histological examination of 178 specimens, mainly <500 mm total length (L(T)) and ranging from 208 to 1290 mm L(T) (119.1 g to 43.0 kg whole body mass), the minimum body sizes for female and male sexual maturation were determined to be 650 and 845 mm L(T), respectively. Primary male development through juvenile sexual differentiation was not detected. A unique blind pouch, with a possible sperm storage function and associated with the testis, was reported for the first time in the Labridae. In Hong Kong retail markets, the global trading centre for this valuable species, live C. undulatus on sale for food were dominated by body sizes <500 mm L(T) between 1995 and 2009, reflecting an international trade largely focused on juveniles. In consideration of these findings, and given the threatened status of this species, management for C. undulatus capture and trade nationally and internationally are discussed with recommendations for ensuring sufficient spawning biomass in exploited populations and for sustainable trade.

This study documents the major external and internal morphological differences between Epinephelus bruneus and Epinephelus moara, and analyses the complete mitogenomes of both species. The partial cytochrome oxidase subunit I (coI) sequence divergence between E. bruneus and E. moara is significantly higher than specimens within the same species (P < 0·05). Analyses of gene flow (Nm = 0·02) and genetic differentiation (ϕst = 0·92995, P > 0·05) reveal reproductive isolation between E. bruneus and E. moara. These results support the hypothesis that E. moara is a valid species. Further molecular comparisons between E. bruneus and E. moara obtained in this study and a specimen identified in GenBank as E. bruneus from South Korea reveal that the latter is identical to E. moara rather than to E. bruneus.

In the changing Arctic Ocean, organic pollutants' transport and biogeochemical processes are strongly influenced by their particulate export on the broad continental shelf. To better evaluate the vertical particulate export of polycyclic aromatic hydrocarbons (PAHs), seawater samples were collected from the Bering Sea, Chukchi Sea, and Canada Basin with the first application of 210Po/210Pb disequilibrium during the summer of 2012. Dissolved PAHs (1.1–19 ng L−1, mean 5.2 ± 3.6 ng L−1) showed spatial distinctions, with high values on the Bering Shelf and low values in the Chukchi Sea, while particulate PAHs (1.0–12 ng L−1, mean 5.0 ± 3.5 ng L−1) showed high levels in the nutrient‐rich Bering Shelf Water layer. According to the 210Po/210Pb deficit on the Bering Shelf, the export fluxes of particulate PAHs ranged from 1,201 ± 276 to 3,650 ± 1,570 ng m−2 d−1, and their residence time ranged from 55 ± 23 to 133 ± 31 days. From the Bering Shelf to the Chukchi Sea, the decreased inventories of dissolved PAHs were positively related to their vertical particulate export fluxes (R2 = 0.62), suggesting the “Shelf Sink Effect” on PAHs.

Gonad ontogeny of the Hong Kong grouper Epinephelus akaara (a bi-directional sex changer) and the yellow grouper Epinephelus awoara (a protogynous hermaphrodite) was examined for the first time from post-larval phase until first sexual maturation, by histology. Approximately 20 specimens of each species were collected randomly every 2-7 weeks from rearing tanks with natural sea water and temperature between June 2013 and June 2014. The paired gonadal primordia (GP) were observed at 6 weeks after hatching (wah) for both species; however, gonia were first observed in GP at 16 wah for E. akaara and at 8 wah for E. awoara. The timings for the appearance of primary-growth stage oocytes (O1) and the completion of ovarian lumen (OL) varied; both at 27 wah for E. akaara, and at 18 and 23 wah for E. awoara respectively. A bisexual-phase gonad with an OL, O1 and scattered spermatogenic cysts (SC) was observed at 27-29 wah for both E. akaara and E. awoara. Sexual differentiation was subsequently observed from the bisexual-phase gonad at 34 wah for E. akaara, and 41 wah for E. awoara, with the appearance of cortical-alveolus stage oocytes (O2) for developing female and the proliferation of SC for developing primary male (i.e. from juvenile directly). Ovaries of mature females contained the vitellogenic stage oocytes (O3) and scattered SC; testes of mature primary males had sperm in sperm sinuses within the gonadal wall and remained O1. Minimum age of first sexual maturation for both female and primary male of E. akaara was at 41 wah; minimum total length (LT ) of female (143 mm) was larger than that of primary male (137 mm L(T)). Minimum age and size of first sexual maturation for female of E. awoara (47 wah and 149 mm L(T), respectively) were larger than those of E. akaara. Developing primary males of E. awoara were found at 41-58 wah, however, mature males were not observed, indicating inconsistency in first sexual maturation for E. awoara. This study provided strong evidences of primary male pathway in E. akaara and E. awoara; the latter is confirmed to be diandric.