Paul Southgate

Local, regional, and global events have potential to disturb fisheries systems embedded within international trade networks. Events associated with sudden and unexpected disturbances, or shocks, in fisheries systems are of particular concern because of their potential to adversely impact the livelihoods and well-being of coastal communities. For these communities in the Pacific region, export-oriented mother-of-pearl (MoP) fisheries have been, and remain, of great economic importance with additional dietary benefits. A lack of information and understanding of events associated with shocks in MoP production and trade, however, limits the ability to predict reactions and to develop appropriate responses to future economic, environmental, or political change. We conducted an integrated assessment of historic MoP export data from 1888 until present (2020) for the largest producer in the Pacific region, Papua New Guinea, to detect shocks and identify associated events. Absence of a trend in the frequency or magnitude of detected shocks and the range of associated events identified suggest that shocks are intrinsic to MoP fisheries systems, and that shocks occur due to varied, often multiple synchronous, events. Critically, legislated policy changes to gear restrictions, licensing, ports of export, size limits, and spatial limits were never associated with shocks, while changes to permitted taxa and export tariffs were implicated in triggering, or contributing to, shocks in MoP exports. The historical assessment of shocks undertaken in this study may aid management agencies in identifying potential risks and appropriate responses to build resilience in MoP fisheries systems, and in artisanal fisheries systems more broadly.

Mabé pearl culture has become a significant addition to traditional rural livelihood activities in Tonga and in other south Pacific countries. Mabé pearl culture is a low-cost, low-tech alternative to round pearl culture, can be undertaken by local people with minimal training, and has considerable potential for value adding through production of jewellery and handicraft items. Mabé pearls are produced by attaching hemispherical nuclei to the inner shell surface of pearl oysters where subsequent coverage with nacre (mother of pearl) produces commercial pearls after a culture period of around 12 months. Traditionally, local mabé pearl farmers attempt to maximise pearl output by implanting four high-profile nuclei into each oyster. Recent research has indicated that fewer nuclei, and those with lower profile, may improve the overall quality of resulting mabé pearls and this has been adopted as best-practice by Tongan mabé pearl farmers. This study reports an economic comparison of these two nucleus implanting arrangements. Results showed that annual returns were not dissimilar with the traditional implanting method (four high-profile nuclei) generating USD 6977 per annum, while the recommended best-practice method (two low-profile, one high-profile nuclei) generated USD 6795 per annum. While the traditional method may generate potentially higher annual returns, there are two key considerations that favour the best-practice method: (1) reduced labour commitment that provides opportunity to engage in other livelihood activities; and (2) the production of a higher grade of pearls is more supportive of developing high value export markets for Tongan mabé pearls.

Stage I phyllosoma larvae of the spiny lobster Panulirus ornatus hatch in tropical oceanic waters with limited and variable food resources. To better understand how these larvae cope with food deprivation, this study examined specific (mU mg 1 protein) and total (mU larva 1) activities of major digestive enzymes (i.e., α-amylase, non-specific esterase, trypsin-like protease) during a series of ex situ experiments. Specifically, temporal changes in enzyme profiles were examined in three experiments simulating scenarios in which phyllosoma hatch and begin development in an environment where (1) prey is either continuously present or absent; (2) prey is initially present, but subsequently absent; (3) prey is initially absent, but subsequently present. Results indicated that the accessibility of suitable prey provides an overarching influence on digestive enzyme activities and substrate utilisation in Stage I phyllosoma of P. ornatus, with enzymatic responses to both intermittent prey availability and food deprivation being influenced by their nutritional history. In the absence of prey, larval digestive enzyme activities (mU larva 1) initially remained static from hatch but eventually declined with extended food deprivation. When prey became available, enzyme activities increased, with delayed access to prey having minimal impact on this enzymatic response. Furthermore, phyllosoma were able to adjust α-amylase and non-specific esterase activities (within 8 h) in response to the disappearance of prey, demonstrating adaptive changes to endure periods of food deprivation that were based on their nutritional history. The ability of phyllosoma to regulate enzyme activities from hatch is an important physiological strategy allowing them to survive in an environment characterised by highly variable zooplankton biomass and abundance, and explains why diets that differ greatly in nutrient composition have consistently been found effective for rearing phyllosoma in captivity.

Mortalities of bivalve larvae and spat linked with Vibrio spp. infection have been described in hatcheries since 1959, causing potential development of resistant bacteria. A reliable and sustainable solution to this problem is yet to be developed. Potential treatment of bacterial infection with bacteriophages is gaining interest in aquaculture as a more sustainable option for managing Vibrio spp. infection. This study assessed the effectiveness of bacteriophages (Φ-5, Φ-6, and Φ-7) against pathogenic Vibrio isolates (USC-26004 and USC-26005). These phage isolates were found to belong to the Myoviridae viral family. A total of 212 ORFs of Φ-5 were identified and annotated. The genome of this phage contained putative thymidine kinase and lysin enzyme. During infections with phages, the OD values of the isolates USC-26005 and USC-26004 remained stable at a much lower reading compared to the control after 9 h of incubation. Mortality rate of oyster (Saccostrea glomerata) larvae was 28.2 ± 3.5% in the bacteriophage treatment group, compared to 77.9 ± 9.1% in the bacterial treatment group after 24 h incubation. Findings of this study indicate that lytic phages might be utilized as potential bio-control agents of luminescent bacterial disease in oyster hatcheries.

This study assessed the use of novel, locally made, protective culture cylinders as a means of improving pearl oyster Pteria penguin performance and standardizing culture methods used by mabé pearl farmers in Tonga. Cylinders were constructed from locally sourced wire mesh, for a cost of USD 12.1 each and were used to protect oysters grown on chaplets. Growth and survival of two age cohorts of oysters-"young" (0.7-y-old and 33.1±0.7-mm dorsoventral height (DVH)) and "old" (2.7-y-old and 86.9±0.8 mm DVH)-cultured using this system were determined every 3-5 wk over an 11-mo period. The DVH of "young" oysters increased by 74.6 mm, wet weight (WW) by 161.2 g, and shell thickness (ST) by 23.4 mm, whereas for "old" oysters, DVH, WW, and ST increased by 55.2 mm, 271.4 g, and 14.7 mm, respectively, over the same period. "Young" oysters held in culture cylinders reached the starting size of the "old" oyster cohort within seven months of growth and at less than half their age (1.2 and 2.7 y old, respectively). "Young" oysters held in culture cylinders also showed a 3-fold greater monthly growth rate than oysters cultured in trays (6.8 and 2.1 mm month-1, respectively). Survival of oysters in culture cylinders over the 11-mo culture period was 91.7% and 97.6% for "young" and "old" oysters, respectively, compared with 25% for oysters cultured in trays. The use of protective cylinders for P. penguin culture increases oyster survival and reduces the culture period required for P. penguin to reach minimum pearl production size by >50% relative to the current tray-based culture method, supporting improved mabé pearl farm profitability.

This article describes the outcomes of research into the potential of community-based mariculture of the commercial sea cucumber, sandfish (Holothuria scabra), as a sustainable livelihood in New Ireland Province, Papua New Guinea (PNG). Around 5000 cultured juvenile sandfish were stocked in a 5-ha trial community sea ranch. The community agreed to protect the area from fishing until researchers collected technical data on sandfish performance. However, poaching of sandfish from the trial sea ranch occurred during the 2018 annual sea cucumber fishing season and no technical data were generated. Community attitudes and responses to the fishing season, the mariculture research activity and the failure of the trial sea ranch were investigated. Widespread community approval of the trial sea ranch and respect for the fishing prohibition were reported. However, it was found that poaching within the ranch escalated to extensive fishing because community-based management proved inadequate to sanction the poachers. Increased buying pressure and higher prices led to intensified fishing effort in the 2018 season. The trial sea ranch failed due to external pressures (i.e., brief, intense fishing season; limited project capacity), compounded by internal factors (i.e., weak local leadership; community disunity). It was concluded that research into and development of sandfish mariculture as a livelihood option in New Ireland Province might be impossible at this time due to the high value of sandfish, the annual sea cucumber fishing season, and ineffective governance at community, provincial and national levels. Lessons learned from this experience are presented and alternative models discussed.