Cultured per­spec­tive

An in­creas­ing pop­u­la­tion and the con­ser­va­tion of the dwin­dling stocks of our last wild food means one thing: aqua­cul­ture is more im­por­tant than ever.

Element - - Cover Story - By Andy Ken­wor­thy

With the busi­ness of catch­ing wild fish un­der pres­sure from all sides, the world is in­creas­ingly look­ing to aqua­cul­ture, the de­lib­er­ate and con­trolled farm­ing in water rather than on land. Global seafood con­sump­tion is re­ported to have risen from 10kg per per­son in the 1960s to 17kg to­day, boosted by in­creas­ing af­flu­ence; to­day about half of all seafood con­sumed to­day comes from some form of fish farm.

The in­dus­try be­gan with largely un­reg­u­lated and hap­haz­ard de­vel­op­ment in the 1960s, which was then reined in with gov­ern­ment con­trols. It has since be­come some­thing of a suc­cess story in re­cent years, cre­at­ing a ma­jor pri­mary in­dus­try, with ma­jor play­ers like New Zealand King Salmon, which is now 52% owned by a Malaysian com­pany. Aqua­cul­ture is worth about $300 mil­lion a year, with a gov­ern­ment tar­get to be­come a bil­lion dol­lar in­dus­try by 2025. The three flag­ship prod­ucts are: Green­shell mus­sels, king salmon and Pa­cific oys­ters.

About two thirds of the dol­lars come from Green­shell mus­sels, New Zealand’s trade-marked brand of farmed na­tive green-lipped mus­sels. They are grown sus­pended on sub­merged ropes by more than a thou­sand farms, cov­er­ing more than 11,000 hectares of sea around our shores. The main Green­shell mus­sel farm­ing ar­eas are in the top of the South Is­land, in Golden and Tas­man Bays, and the Marl­bor­ough Sounds, and the Coro­man­del in the Firth of Thames. There are other smaller ar­eas of mus­sel farm­ing around New Zealand in­clud­ing

Houhora Bay (North­land), the Hau­raki Gulf (Auck­land), as well as around Banks Penin­sula and Ste­wart Is­land.

Aside from their vis­ual im­pact, the farms also de­posit shell and other waste into the water and seabed nearby, con­sume plank­ton from the ocean and have been known to cause tan­gling prob­lems for whales and other ma­rine mam­mals. But re­cently the ef­fects have not been so se­vere as to raise the ire of en­vi­ron­men­tal groups or wide­spread public con­cern.

New Zealand is the world’s largest pro­ducer of king salmon, chiefly ex­ported to the United States, Ja­pan and Australia. The fish are born in land-based hatch­eries and trans­ferred to sea cages or fresh water farms for up to 18 months, un­til they reach a harvest weight be­tween 2-4kg. Most sea cage farm­ing is in the Marl­bor­ough Sounds, Ste­wart Is­land and Akaroa Har­bour, and there are also fresh water op­er­a­tions in Can­ter­bury, Otago and Tas­man.

The ab­sence of any na­tive salmon species, as well as New Zealand’s rig­or­ous bio-se­cu­rity mea­sures, means that the king salmon raised here don’t re­quire vac­cines and an­tibi­otics. The salmon are fed spe­cially for­mu­lated fish­meal pel­lets, which do not con­tain steroids or other growth en­hancers.

Ac­cord­ing to the New Zealand Salmon Farm­ers As­so­ci­a­tion’s Fin­fish Aqua­cul­ture En­vi­ron­men­tal Code of Prac­tice states that raw ma­te­rial for fish feeds should come from sus­tain­ably man­aged fish­eries.

Done badly, fish farms can cre­ate se­vere im­pacts on the seas around them, es­pe­cially through the re­sult­ing fae­ces and un­eaten food that can pol­lute the water and seabed. As a re­sult, salmon farms are gen­er­ally not ap­proved if they are pro­posed over reefs or com­plex habi­tats with a high di­ver­sity or abun­dance of species, or im­por­tant fish spawn­ing or nurs­ery habi­tats. In fact, farm site se­lec­tion is so crit­i­cal that only a hand­ful of sites around the coun­try are con­sid­ered suit­able.

But done well, fish farms can have a po­ten­tially pos­i­tive ef­fect, as the farms tend to at­tract wild fish around them be­cause of the in­creased shel­ter and nu­tri­ents. Care­fully cho­sen sites with strong cur­rents en­sure the cages are well oxy­genated and flushed of waste. Com­puter con­trolled feed­ing and video mon­i­tor­ing has also been in­stalled in some fish farms to re­duce food waste, the re­sult­ing cost to the en­vi­ron­ment and the farms’ bot­tom line.

The mus­sel farm­ing in­dus­try is worth

about $200m a year to New Zealand.

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