Sandfish generations: loss of genetic diversity due to hatchery practices in the sea cucumber Holothuria (Metriatyla) scabra

Hatcheries are indispensable for seed production of many commercial aquaculture species. However, for mass-spawning species in particular, they can be capricious environments where genetic diversity among progeny may be lost due to small effective broodstock population sizes, variable parental contributions and differential family survival. Understanding the genetic impacts of hatchery production is therefore important for addressing these problems and optimising propagation methods. We used 6051 genome-wide Single Nucleotide Polymorphisms (SNPs) to analyse genetic diversity, parental contributions and offspring kinship during a commercial-scale hatchery production run of sandfish (Holothuria scabra), a high-value sea cucumber grown in mariculture operations across the Indo-Pacific region. Broodstock contributions were highly skewed, with up to 26% of the parent pool contributing and kinship analyses determined that just two parents sired between 44.4 and 67.5% of all offspring genotyped. Effective population sizes were reduced as expected between broodstock and offspring groups (NeLD = 1121.2 vs. 19.4, respectively), while losses of allelic diversity but not overall heterozygosity were apparent. Numbers of families surviving (13–16) to the juvenile stage were low, suggesting low effective population sizes among offspring cohorts is an issue for sandfish hatchery operations. To address variability in family compositions and broodstock contributions, pedigree tracking and batch spawning may be used to optimize broodstock management and hatchery protocols, to ensure production of genetically diverse offspring for routine culture and restocking operations. As many sandfish broodstock remain wild-sourced, maintenance of healthy wild populations as reservoirs of genetic diversity is important, along with selection for spawning of genetically diverse individuals which are as distantly-related as possible

Octopuses in the south - west Pacific region: a review of fisheries, ecology, cultural importance and management

Octopuses present a difficult resource to manage because of their relatively short life spans, rapid growth rates, high natural mortality and seasonal fluctuations in abundance. With exploitation efforts increasing worldwide, particularly in the Pacific Island region, substantial knowledge gaps in their biology, exploitation and management remain. We conducted a literature review to summarise their species distribution, abundance, ecological attributes, utilization, importance and management within the Pacific Island Countries and Territories (PICTs) of Fiji, Vanuatu, the Solomon Islands, New Caledonia, Tonga, Samoa and American Samoa. We found that 23 species of octopuses within 11 genera were recorded from these PICTs, belonging to the families Amphitretidae and Octopodidae. Overall, Tonga was the most speciose country with 11 occurrence records and Samoa recorded the least with just a single species. All other countries recorded between 2 and 8 taxa. The day octopus (Octopus cyanea) was recorded from all PICTs except Samoa. There are no specific national regulations on octopus fisheries within the PICTs and management is largely dependent on overarching national fisheries legislation. However, community-based management efforts can be an effective platform in sustaining octopus stocks. Octopuses also play an important role in the folklore and customs of many Pacific Islanders, and we provide a summary of these for the specific PICTs assessed. This review highlights areas for further research and development for the Pacific Island region and the urgent need to address specific knowledge gaps on octopus taxonomy, stock assessment and fishery management