Paul C. Southgate’s research while affiliated with University of the Sunshine Coast and other places

The mass production of release‐size H. scabra juveniles in the Philippines is primarily done in a floating hapa ocean‐based nursery systems. To optimize its production, understanding the influence of different culture conditions and their management is necessary. In this study, the effects of hapa net cleaning interval, hapa layers, and stocking density on growth and survival of sandfish juveniles reared in floating hapa (L × W × H: 1.7 m × 0.9 m × 1.2 m) nursery system were assessed in two 60‐day field studies. Results showed that the number of hapa net layers and cleaning interval had negligible effects on the growth performance of sandfish juveniles by day 30. However, sandfish juvenile survival was affected by hapa net layers with higher survival in triple‐layer mosquito net hapas (40.5 ± 0.97%) compared to double‐layer mosquito net hapas (17.8 ± 0.62%). By day 60, the growth performance of sandfish juveniles in double‐layer hapas was higher (average weight: 5.0 ± 0.97 g; AGR: 0.13 ± 0.03 g day⁻¹) compared to that in triple‐layer mosquito hapa nets (average weight: 3.1 ± 0.23 g; AGR: 0.07 ± 0.01 g day⁻¹). Survival of sandfish juveniles reared in double‐layer mosquito net hapas, cleaned at 5‐day intervals (85.9 ± 4.58%) was significantly lower compared to all other treatments. Conversely, initial juvenile stocking density did not significantly affect the growth performance and survival of sandfish juveniles in both rearing cycles. We therefore recommend the use of triple‐layer mosquito net hapas during the first 30‐day culture period and an initial stocking density of 1000 post‐settled sandfish juveniles to increase production output. After 30 days, when the juveniles are larger, the use of double‐layer mosquito net hapas and lower stocking density are recommended to reduce cost and enhance growth performance. Where cleaning is necessary, hapa nets may be cleaned at 10‐day intervals to improve survival. The results of this study have important implications for optimizing the production of release‐size sandfish in ocean‐based nursery systems in the Philippines.

Expansion of pearl production using the silver‐lip pearl oyster, Pinctada maxima, depends on increasing the availability of high‐quality spat from hatcheries and optimization of existing hatchery protocols. Research to develop feeding regimes yielding higher quality spat is seen as a priority. This study evaluated the suitability of three microalgae (Rebecca salina, Chaetoceros simplex and Tisochrysis lutea), fed singly and in combination, for spat of P. maxima and assessed whether mixed diets yielded spat of higher quality. A model‐fitting approach examined the response of spat fed microalgal diets for 35 days. Organic content of spat, as an indicator of quality, as well as metrics relating to spat size and weight were considered. On the basis of organic content, all microalgal diets tested were found suitable and there was no evidence that the mixed diets yielded higher quality spat compared to monospecific diets. Further, any gains in spat size attributed to the mixed microalgal diets were comparatively modest. Contrary to long‐held assumptions, our results indicate that monospecific microalgal diets are not necessarily inferior to mixed microalgal diets for on‐growing spat of P. maxima. They indicate potential to develop simpler and cheaper protocols for culture of P. maxima spat in land‐based systems.

Pearl culture in Fiji relies on a supply of pearl oysters obtained through the strategic deployment of spat collectors. Although the design and deployment of spat collectors aim to maximize the recruitment of pearl oysters (Pinctada and Pteria spp.), this activity incidentally captures many other bivalves as bycatch. This study explored whether tropical rock oysters (specifically Magallana bilineata and Saccostrea spp.) were present and sufficiently abundant as bycatch from pearl oyster spat collectors, to support additional commercial opportunities. The results showed that the absolute (0.7 ± 2.1 spat collector −1) and proportional (2.9% of all bivalves) abundance of these taxa was very low, which would limit oyster harvest in meaningful quantities. Although the prospect of creating additional revenue streams from bycatch could be seen as an incentive to on-grow and sell tropical rock oysters despite their low abundance, it is argued that greater benefit would come from prioritizing activities related to pearl oysters and associated downstream products such as mabé pearl, shellcraft, and pearl-meat production. Ultimately, existing spat collection activities within the cultured pearl sector did not have the anticipated potential to support supplemental aquaculture of tropical rock oysters.

Development of an appropriate nursery culture system is critical in improving the survival of post-release sandfish juveniles within different production systems. This study evaluated the growth performance of sandfish juveniles reared in floating hapa enclosures and advanced nursery culture pens by small-scale grouper farmers within rural coastal communities in Bolinao, northwestern Philippines. Growth performance and survival of sandfish juveniles reared in floating hapas were high (Table 1a). From an initial average weight of 0.03±0.002 g, sandfish attained an average weight of 4.28 ± 0.23 by day 66. Highest growth rates of sandfish juveniles reared in floating hapas was recorded by day 66 at 0.09 ± 0.02 g day-1 while lowest growth rate was recorded by day 24 at 0.04 ± 0.01 g day-1. Additionally, survival of sandfish juveniles at the end of the monitoring period was high at 56.8 %. Likewise, growth performance and survival of sandfish reared in the advanced pens were high (Table 1b). Highest growth rate of sandfish reared in the advanced pens was recorded by day 86 at 0.89 ± 0.1 g day-1 while the lowest growth rates was recorded at the end of the study at 0.15±0.3 g day-1. Despite the decreased in growth rates, sandfish attained 102.7±6.2 g after 157 days of rearing in the grow-out pens. This study showed the viability of releasing sandfish juveniles directly into advanced nursery pens as indicated by high growth performance and apparent survival of sandfish reared in the pens. Additionally, results of the study provide basis for the utilization of ocean-based advance nursery and development of a production model involving small-scale aquaculture farmers to increase sandfish juvenile production and ultimately the realization of the socio-economic benefits of sea cucumber mariculture.

Throughout the Pacific Islands, shellcraft has begun to feature prominently in development intervention which aims to generate positive livelihood outcomes for coastal communities. This activity often involves the post-harvest processing of natural assets, namely shells and skeletal remains of marine taxa, into jewellery by individuals or small-sized enterprises. To foster participation in shellcraft, development intervention commonly involves gifting or subsidising physical assets. Yet knowledge of the natural (i.e., taxa) and physical (i.e., tools) assets required for shellcraft remains scant. An understanding of human dimensions in shellcraft pertaining to patterns in asset use, such as how tool ownership differentiates taxa utilised and products produced, is important for determining if access to a specific tool is necessary, or an encumbrance, for achieving a desired outcome. In this study, we identified tools used and variation in tool ownership among artisans engaged in shellcraft to afford an accurate and realistic understanding of the tools required to participate in this activity. We then evaluate how ownership of a specific tool or type of tool differentiates both taxa utilisation and product production for shellcraft. Results indicate ownership of neither all nor any specific tool was required to participate in shellcraft, with artisans typically owning a unique combination of tools. Furthermore, results identified that some specific tools were critical for affecting the attractiveness of utilising certain taxa or producing certain products. Implications of the significant relationships between specific tools and certain taxa or products are discussed in the context of development intervention and commonly articulated theories of change where shellcraft is linked to subsistence fishing, aquaculture, or tourism.

Shellcraft is a livelihood activity that utilizes shells and skeletal remains of marine taxa for producing ornamental and decorative items. Despite an increasing importance of shellcraft in coastal areas of the Indo-Pacific region, information necessary for stakeholders to identify and respond to change through policy and management decisions is often lacking for fisheries that support this activity. To address this knowledge gap, a quantitative approach was taken to evaluate social-ecological factors (the what, where, how much, who, when, how, how often, and how long) in a “shellcraft fishery” centered at the Nusa Islands of Papua New Guinea. More than 151,100 individuals across 69 marine taxa were fished annually for shellcraft at the Nusa Islands; fishing was infrequent and quantities fished were low for most taxa when compared with other small-scale fisheries. Fishing most taxa had no association with the main demographic divisions within households although, in terms of participation and catch richness, women were the main actors. Gleaning, combing, and free-diving were the only fishing techniques used, with taxa primarily fished by gleaning intertidal habitats during the day. To contextualize sustainability of this fishery, local ecological knowledge-based perceptions of stock status for the marine taxa fished were examined. Considerations for governance, which included synthesis of existing regulatory measures and aspirations, are also discussed. Since shellcraft occurs throughout the Indo-Pacific region and there are commonalities in taxa utilized, this study provides a basis for comparative analysis of shellcraft fisheries within the region.

The sandfish Holothuria (Metriatyla) scabra, is a high-value tropical sea cucumber harvested from wild stocks for over four centuries in multi-species fisheries across its Indo-Pacific distribution, for the global bêche-de-mer (BDM) trade. Within Southeast Asia, the Philippines is an important centre of the BDM trade, however overharvesting and largely open fishery management have resulted in declining catch volumes. Sandfish mariculture has been developed to supplement BDM supply and assist restocking efforts; however, it is heavily reliant on wild populations for broodstock supply. Consequently, to inform fishery, mariculture, germplasm and translocation management policies for both wild and captive resources, a high-resolution genomic audit of 16 wild sandfish populations was conducted, employing a proven genotyping-by-sequencing approach for this species (DArTseq). Genomic data (8,266 selectively-neutral and 117 putatively-adaptive SNPs) were used to assess fine-scale genetic structure, diversity, relatedness, population connectivity and local adaptation at both broad (biogeographic region) and local (within-biogeographic region) scales. An independent hydrodynamic particle dispersal model was also used to assess population connectivity. The overall pattern of population differentiation at the country level for H. scabra in the Philippines is complex, with nine genetic stocks and respective management units delineated across 5 biogeographic regions: (1) Celebes Sea, (2) North and (3) South Philippine Seas, (4) South China and Internal Seas and (5) Sulu Sea. Genetic connectivity is highest within proximate marine biogeographic regions (mean F st=0.016), with greater separation evident between geographically distant sites (F st range=0.041–0.045). Signatures of local adaptation were detected among six biogeographic regions, with genetic bottlenecks at 5 sites, particularly within historically heavily-exploited locations in the western and central Philippines. Genetic structure is influenced by geographic distance, larval dispersal capacity, species-specific larval development and settlement attributes, variable ocean current-mediated gene flow, source and sink location geography and habitat heterogeneity across the archipelago. Data reported here will inform accurate and sustainable fishery regulation, conservation of genetic diversity, direct broodstock sourcing for mariculture and guide restocking interventions across the Philippines.