What’s the best method to collect sea urchins for aquaculture?

 

A diver surfacing with a bag full of urchins. Photo by Fletcher Warren-Myers.

There are millions of purple sea urchins (Heliocidaris erythrogramma) in Port Phillip Bay chomping their way through kelp forests, which are important habitats for many creatures and critters that live within the bay. In their wake, urchins leave unsightly and biologically unproductive barrens, therefore causing reduced local biodiversity. Barrens can be flipped back into kelp forests if urchins are either removed or destroyed – but both options are extremely expensive. Fortuitously, the gonads (or roe) of urchins are a Japanese delicacy, with high quality roe fetching up to $450 kg-1. However, the roe of urchins harvested from barrens are typically unappealing and inedible, and therefore fishermen tend harvest them elsewhere.

Sea urchin aquaculture is an emerging industry in Australia, with several universities working on cultivating a variety of urchin species across Australia. The SALTT lab previously identified that harvesting adult urchins directly from barrens and feeding them with quality feeds to produce marketable roe is a nifty solution that can reduce the number of urchins in barrens while simultaneously profiting from the increasing demand for roe.

However, in order to collect urchins from barrens to bring them to aquaculture facilities to fatten them up, it’s important to determine the best harvest method that does not affect their survival and external condition. Dr Fletcher Warren-Myers and researchers from the University of Melbourne and Deakin University tested if divers using a 3-pronged hook or careful hand-collection to harvest urchins affected their mortality and external condition both in the short- and long-term. Overall, they found that survival and condition was similar regardless of collection method. As divers using the hook method collected urchins twice as fast as by hand, this will become the method to harvest urchins in the future.

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