From plates to the port

Seafood shells dis­carded by din­ers are be­ing re­pur­posed to breathe new life into south­ern Australia’s dec­i­mated shell­fish reefs.

Australian Geographic - - Geobuzz - STORY BY AMY LEWIS

THE GREAT BAR­RIER REEF has be­come a po­tent sym­bol for threat­ened reef en­vi­ron­ments. Yet the lesser-known shellf ish reefs of Vic­to­ria and South Australia have suf­fered an even greater level of im­pact, with up to 99 per cent of these sys­tems now de­stroyed due to a long his­tory of dredge f ish­ing.

In an ef­fort to re­store one of these ecosys­tems, a team of sci­en­tists, f ish­ers and con­ser­va­tion­ists has brought an in­no­va­tive so­lu­tion to the ta­ble. They are us­ing mol­lusc shells re­cy­cled from our din­ner plates to re-es­tab­lish mus­sel and oys­ter reefs at Port Phillip Bay, in south­ern Vic­to­ria.

In col­lab­o­ra­tion with the Vic­to­rian Fish­eries Au­thor­ity and Al­bert Park Yacht­ing and An­gling Club, The Na­ture Con­ser­vancy (TNC) has for the past two years been col­lect­ing oys­ter, mus­sel and scal­lop shells from restau­rants and seafood sup­pli­ers in Gee­long, south-west of Mel­bourne. They have so far col­lected more than 420cu.m of shells that would have oth­er­wise ended up in land­fill.

In Novem­ber, they be­gan spread­ing shells and lime­stone rub­ble across the sea f loor at two sites in the bay to form bases for new An­gasi oys­ter ( Ostrea an­gasi) reefs. First, how­ever, the shells were stored at a site on Bel­lar­ine Penin­sula, where they were left to cure through sun and wind ex­po­sure for six months to en­sure any diseases they might have been

car­ry­ing were killed off. In March, the team will spread shells at a sec­ond site in the bay to form the base of a blue mus­sel ( Mytilus edulis) reef.

The sci­ence be­hind the ap­proach is sim­ple. Shellf ish lar­vae need a solid sub­strate on which to grow, so in ar­eas where suit­able reef habi­tats have been de­pleted, lay­ers of re­cy­cled shells can be ar­ranged on the sea f loor to pro­vide new hard sur­faces that will sup­port de­vel­op­ing lar­vae.

Most of Port Phillip Bay’s nat­u­rally oc­cur­ring shell­fish have died off, but re­searchers hope plac­ing the shells on the sea f loor dur­ing the nat­u­ral oys­ter and mus­sel spawn­ing sea­sons will en­cour­age rem­nant pop­u­la­tions to colonise the new reefs. To en­sure the suc­cess of these sites, the team is also introducing more than 10 tonnes of live blue mus­sels sup­plied by aqua­cul­ture farm­ers and some 350,000 oys­ter spat grown by the Vic­to­rian Shell­fish Hatch­ery.

“Al­though we have a low pop­u­la­tion base in the bay, we want to tap into the po­ten­tial of nat­u­ral re­cruit­ment,” says the project’s man­ager and TNC’s ma­rine restora­tion co­or­di­na­tor, Si­mon Brani­gan. He says Port Phillip Bay’s scheme was in­spired by a sim­i­lar USA ini­tia­tive, where re­cy­cled shells have been used to re­store 7ha of a Great Bay Es­tu­ary reef, in New Hamp­shire. Since 2009, oys­ter num­bers there have risen by more than 3.5 mil­lion.

The Port Phillip Bay shell-re­cy­cling ini­tia­tive is part of a large-scale reef restora­tion project that will see at least 10 reefs – cov­er­ing about 1000sq.m – newly con­structed or re-es­tab­lished. The first stage of the project was com­pleted in April 2017. It saw teams use lime­stone, rather than shells, to re­store two oys­ter reefs: Wil­son Spit Reef, at Gee­long Arm, and Mar­garet’s Reef, at Hob­sons Bay.

“We ex­pect that af­ter about three years, the shellf ish reefs will sta­bilise and start to grow,” Si­mon says. He hopes the project will not only in­crease the bay’s mus­sel and oys­ter pop­u­la­tions, but also ben­e­fit other species. The new reefs will pro­vide habi­tat and prey for an ar­ray of ma­rine life and help im­prove wa­ter qual­ity in the bay, be­cause shellf ish re­move ex­cess ni­tro­gen and in­or­ganic ma­te­ri­als through f il­tra­tion.

The project’s benef its ex­tend be­yond the wa­ters of the bay. It pro­vides lo­cal peo­ple with em­ploy­ment – Gee­long Dis­abled Peo­ple’s Industries sup­ply a work­force to col­lect shells and trans­port them to the cur­ing site. It also of­fers busi­nesses a sus­tain­able way of deal­ing with shellf ish waste. “We have re­duced our waste by 2500kg in two years, solely through re­cy­cling mus­sel shells,” says Alex Smith from Lit­tle Crea­tures, one of the restau­rants do­nat­ing shells. “The fact we can do some­thing with them rather than just throw them away is fan­tas­tic.”

Si­mon and his team hope to mir­ror their suc­cess at Port Phillip Bay with sim­i­lar projects at SA’s Gulf St Vin­cent and Western Australia’s Oys­ter Har­bour.

Rid­ing high on suc­cess, The Na­ture Con­ser­vancy’s ma­rine restora­tion co­or­di­na­tor, Si­mon Brani­gan, stands on a mound of seafood shells dis­carded by restau­rants but des­tined for re­cy­cling.

Vic­to­rian restau­rants are be­ing of­fered an al­ter­na­tive to dis­card­ing shells from seafood dishes.

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