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Deepwater snappers (Lutjanidae) support important commercial demersal fisheries in Okinawa and throughout much of the Indo-Pacific region. However, recent evidence suggests that over-exploitation has substantially reduced stock biomass throughout these regions. Deepwater marine protected areas (MPAs) are often established as a conservation and management tool, but there are few published studies on their efficacy. This study examined the effectiveness of a deepwater MPA in the Kita-Taikyu Bank (KB), based on the changes in relative abundance and size-frequency distributions for target species collected over seven years between a five-year period of year-round closure and subsequent seasonal closures. Etelis coruscans was the most abundant lutjanid in the KB, comprising 45.0% of the total number of individual deepwater snappers. The relative abundance of E. coruscans in the deepwater MPA was influenced by whether protection was year-round or seasonal; their abundance decreased significantly when the ban was lifted. Some distinct size modes of E. coruscans gradually grew larger during the year-round closure, but modes were indistinct after the change to seasonal closures. In addition, our results showed that the relative abundance of mature size classes had not fully recovered during the study period. In our tagging experiment for 151 deepwater snappers comprised of six species, two tagged Pristipomoides filamentosus were recaptured. These cases supplied some biological data regarding deepwater snappers: the periodicity of the growth zone formation and the low rate of cross-border movement of Pr. filamentosus. Our study suggested that deepwater snappers are rapidly depleted by fishing and very slow to recover. It also provided evidence of the potential success of MPAs for deepwater snappers; longer-term year-round closure of deepwater MPAs may be the best solution for affording long-lived fishery species the protection necessary for them to achieve maturity.

Little is known about the behavior and migration of deep-sea snappers, as observation of their deep-sea habitats is difficult. Manual acoustic tracking of deepwater longtail red snappers Etelis coruscans was conducted at the Ojika Se Bank, in the waters around the Satsunan Islands, Japan, to investigate their post-release horizontal and vertical behavior. Eight individuals were tagged with transmitters equipped with depth sensors for tracking. At least six of these eight fish survived after release. The fish gradually dispersed from the Ojika Se Bank, and only one-third remained there 33–34 days after release. The fish that remained at the Ojika Se Bank moved horizontally by 2.2 ± 2.0 km daily, but remained near the top of the bank. The fish were distributed in the 168.8- to 288.8-m depth range, and moved vertically by up to 50.0 m between consecutive days. To the best of our knowledge, this is the first report on the daily fine-scale horizontal and vertical movements of any species of deep-sea snapper.

Onaga Etelis coruscans is an important component of the commercial deep-water handline fishery in Hawaii and is one of the more valuable species because of its local popularity. This species is part of a management unit called the Deep 7, a data-poor fishery comprising six snapper and one grouper species for which information about age, growth, longevity and maturity is incomplete. Although some life history information is available for onaga, prior estimates of maximum age (~10–20 years) likely suffered from underestimation of age, whereas two recent studies provided estimates that were similar to the work presented here—a refined age reading protocol revealed age estimates up to 55 years. This maximum age estimate and the age reading protocol used on onaga otoliths were validated using bomb radiocarbon dating. Using an otolith reference image age reading protocol that relied on the validated otolith sections, almost all onaga otoliths covering nearly the full body size range were used to generate valid growth parameters that may be sexually dimorphic. An empirical estimate of age at the length at which 50% of individuals reach maturity (L50) is 11 years, and fish near the minimum retention size in Hawaii (1 lb (~0.45kg) or ~30-cm fork length) may be just 2–3 years old.

This study provides the first comprehensive fishery-independent baseline assessment of commercially important deepwater bottomfish populations across the main Hawaiian Islands. Differences in bottomfish relative abundance and size distribution were evaluated for 6 deepwater Bottomfish Restricted Fishing Areas (BRFAs). While no differences were detected in species relative abundance, evaluation of size-frequency distributions found the 2 most commercially valuable species (Etelis coruscans and Pristipomoides filamentosus) to be significantly larger inside the BRFA at Ni‘ihau, located off the most remote of the main Hawaiian Islands. This BRFA is 1 of 2 ongoing BRFAs offering 10 yr of protection. This result highlighted the time it may take a long-lived and slow-growing species to show a detectable response to protection and that size distribution analyses can detect these more subtle changes. No positive effects of protection were detected for the second ongoing BRFA located off Hawai‘i. Instead, 2 species (P. filamentosus and P. sieboldii) were significantly larger outside the BRFA. In contrast to Ni‘ihau, the second BRFA established in 1998 originally included less preferred habitat and is next to the second largest port in Hawai‘i, offering greater access, higher population pressure and more problematic enforcement. This study demonstrates that biological, sociological and environmental context must also be considered when interpreting the effectiveness of marine protected areas.

Data on the potential exploitation of deep demersal fish species in Reunion Island are very limited. The Regional Comitee for Sea Fisheries and Marine Breeding, with the scientific and technical support of Ifremer of La Reunion, has launched prospecting campaigns to identify and characterize deep-sea fish species (between 150 to 600 m deep), with an innovative method of catching with electric reel. The catches made concern mainly 5 main species (yields, frequency of catch, commercial interest). A new species, the brillant pomfret (Eumegistus illustris), as well as the longtail red snapper (Etelis coruscans), are the both main resources that can be exploited by the electric reel technique. They represent more than 60% of the overall catches made during the survey. The other species (red snapper (Etelis carbunculus), shortnose spurdog (Squalus megalops), beryx (Beryx decadactylus), black snoek (Thyrsitoides marleyi)) are supplements species, given the impossibility to target them, and maintain daily yields at a consistent level with the profitability of the fishing operation. The distribution of these species is strongly related to bathymetry and an assessment of the area available for their habitat around the island, shows that the abundance of these resources is limited to an incompatible level with intensive exploitation. Absence of more precise scientific arguments suggest a precautionary approach and encourages to recommend not favoring the exploitation of new efficient fishing units on this resource but rather to consider it as a potential complementary activity for the fishing units of current small professional fishery, which practice other trades (coral fish species and pelagic fish on FADs with fishing hook)., Les données concernant les potentialités d’exploitation des espèces démersales profondes à La Réunion sont très limitées. C’est pourquoi, le Comité Régional des Pêches Maritimes et des Elevages Marins, avec le soutien scientifique et technique de l’Ifremer de La Réunion, a lancé en 2000 des campagnes de prospection pour identifier et caractériser les espèces de poissons profonds (entre 150 à 600 m de profondeur) d’intérêt halieutique, avec une méthode innovante de capture au moulinet électrique. Les captures réalisées concernent principalement 5 espèces d’intérêts halieutiques (rendements, fréquences des captures, intérêt commercial). Une espèce nouvelle, le « mochong » ou « castagnole » (Eumegistus illustris), ainsi que le vivaneau la flamme (Etelis coruscans) constituent les ressources principales exploitables par la technique du moulinet électrique. Elles représentent plus de 60 % des captures globales réalisées lors de la prospection. Les autres espèces (vivaneau rouge (Etelis carbunculus), requin zépine (Squalus megalops), béryx (Beryx decadactylus), snoek (Thyrsitoides marleyi)) n’interviennent qu’en compléments de revenu, compte tenu de l’impossibilité de les cibler et de maintenir des rendements journaliers à un niveau compatible avec la rentabilité de l’exploitation. La répartition de ces espèces est fortement liée à la bathymétrie et une évaluation de la superficie disponible pour leur habitat autour de l’île, montre que l’abondance de ces ressources est nécessairement limitée à un niveau incompatible avec une exploitation soutenue. En absence d’arguments scientifiques plus précis, l’approche de précaution incite à recommander de ne pas favoriser la mise en exploitation de nouvelles unités de pêche performantes sur cette ressource mais plutôt de la considérer comme une activité complémentaire potentielle pour les unités de la flottille de petite pêche professionnelle actuelle, qui pratiquent les autres métiers (pêche à l'hameçon des poissons de fond récifaux et des poissons pélagiques sur DCP).