Conservation of handfishes and their habitats - Final Report 2020

In late 2018, the National Handfish Recovery Team implemented a Red handfish (Thymichthys politus) re-population strategy (‘head-starting’ program) to bolster wild population numbers. We successfully collected Red handfish eggs, hatched and raised them in captivity at Seahorse World in 2018, and at the Institute for Marine and Antarctic Studies (IMAS) Taroona aquaculture facility in 2019. For the first ever, planned release of captive-reared Red handfish juveniles occurred back into the wild for population-bolstering purposes, which meant that we had two cohorts to return (one- and two-year old individuals).

Prior to release we implemented several essential components not outlined in the original project plan – habitat restoration (removal of barrens-causing urchins at the two known populations), tagging of some of the juveniles prior to release (to enable us to validate spot pattern recognition in young individuals), and pre-release conditioning to familiarise juveniles with their natural ecosystem prior to release (habitat, fishes, and invertebrates they are likely to encounter in the wild).

Forty-two juvenile Red handfish were successfully released into the wild across two existing populations in south-eastern Tasmania. This first-ever release of captive-hatched Red handfish was undertaken in 2020, and dive surveys re-sighted released juveniles at 1-, 3-, and 5-days post-release (across both sites).

Demonstration of head-starting as a successful strategy via post-release monitoring means that this approach should now be scaled-up to continue bolstering of wild populations – before the existing population size dwindles further. This work needs to be actioned in combination with increased effort in habitat assessment, restoration and management. Based on the success in integrating captive-raised juveniles back into the wild, we should now look to resourcing captive-breeding trials, which have greater capacity to replenish populations than head-starting and crucially would also serve as an insurance population. The feasibility of translocating individuals from wild and captively bred stocks to sites where they do not currently occur should be investigated as a potential extinction-avoidance tool for Red handfish under the aim of creating more populations in less threatened habitats.