Steven W. Purcell

Lifespans of animals inform us about generation length, underpinning assessments of extinction risk and models for fishery harvest strategies. Uncertainty and contention endure about the lifespans of coral reef echinoderms, especially soft-bodied sea cucumbers. We used a photographic mark–recapture study at Lizard Island, Australia, to validate longevity, growth and displacement in the large sea cucumber Bohadschia argus . This species is harvested in fisheries throughout the western central Pacific and Southeast Asia. Using the photographic mark–recapture method, four individuals, estimated to be up to 22 years old in 2012, were recaptured 11 years later. Most eye-spots on the matched individuals persisted over the study period. The recaptures confirmed a lifespan of at least 33 years and an estimated generation length of at least 21 years. Long-term growth of the individuals was modest, with body size increasing by just 0.2–1.3% per year. Some individuals had displaced little over the period. Our data prove multi-decadal longevity in coral reef sea cucumbers, underscoring their vulnerability to extinction and a need to apply conservative estimates of generation length to conservation planning and fishery models.

The genetic diversity and connectivity of reef-building coral populations are key to their survival in warming oceans. Yet our understanding of corals’ demographic resilience and adaptive potential is complicated by cryptic species diversity, wide geographic distributions, and complex coral-algal symbioses. To address these challenges, we investigated genetic connectivity and diversity of the broadcast-spawning coral Acropora spathulata and its associated Symbiodiniaceae across 29 reefs spanning the Great Barrier Reef, the Coral Sea, and New Caledonia, using whole-genome sequencing of 1,088 colonies. We identified four genetically distinct coral populations that diverged between 0.27 and 0.65 million years ago, likely due to geographic isolation across thousands of kilometers. These populations maintained asymmetrical gene flow along major ocean currents despite demographic isolation, and sustained large local effective population sizes (∼2,900), supported by a high dispersal range of ∼100 km per generation. In contrast, their Symbiodiniaceae partners varied over finer spatial scales, with five distinct Cladocopium taxa distributed along latitudinal and cross-shore gradients, likely driven by local environmental conditions. These results suggest that high dispersal capacity and large local population size promote demographic resilience within reef systems, while environment-specific symbioses and long-distance gene flow across reef-systems support adaptation and evolutionary rescue.

Sea cucumbers paradoxically suffer from being both highly prized and commonly disregarded. As an Asian medicine and delicacy, they command fabulous prices and are thus overfished, poached, and trafficked. As noncharismatic animals, many are understudied and inadequately protected. Despite presenting a rich diversity of life histories, members of this broad taxonomic group (class Holothuroidea) are often managed simply as “sea cucumbers” in fisheries worldwide. One cannot imagine fishes (class Pisces) being given the same universal treatment. Yet this may happen for species of sea cucumber that differ on the same fundamental level as tilapia and tuna. As more sea cucumbers reach an endangered status and wild populations become depleted to the point of collapse, critical questions arise about the relevance of established conservation and governance strategies. This article reviews the main threats faced by exploited sea cucumbers, outlines conservation and governance effectiveness, identifies gaps in knowledge, and explores management and research perspectives in the context of climate change and booming fisheries crime. We stress the perilous state of harvested sea cucumbers globally and the urgent need for action.

Fisheries science draws on morphometric data for stock assessments. Length–weight relationships are essential for estimating body weight from length measurements taken either underwater (in situ) or out of the water (ex situ). We examined morphometric models for the high-valued sea cucumber, Holothuria lessoni. From 77 specimens captured in 2024 (mean weight ± SD: 1774 ± 372 g), we measured body length and width in situ and ex situ, then weighed the animals ex situ. We compared morphometric models using four biometric parameters. The fitted relationships were more statistically significant (p < 0.001) when using in situ measurements compared to ex situ measurements. The length–weight relationship from our study was compared with those from two previous studies on the same species at the same location. Each study generated significantly (p < 0.001) different length–weight relationships. These findings suggest that length–weight relationships should be re-evaluated at regular intervals, as they may evolve over time. Our study indicates that estimation of body weight from length (and width) must rely on established relationships corresponding to whether the measurements are made in situ or ex situ. Our results suggest that in situ measurements could provide more reliable data for length–weight relationships in certain holothuroids.