Sea for your­self

The idea of a ma­rine re­serve where large snap­per and cray­fish can do what they do best – re­pro­duce – is one that should be en­cour­aged. Ma­rine re­serves pro­vide just that.

Element - - Ecology - By So­phie Bar­clay

In a coun­try where 33% of our land is pro­tected, a sim­i­lar con­ser­va­tion ethic should ap­ply to our ubiq­ui­tous coast­line. How­ever only 7% of our wa­ters are pro­tected. Ex­clud­ing our two ma­jor off­shore ma­rine re­serves, the fig­ure drops to less than 0.1% of the main­land coast. We have failed mis­er­ably to meet our obli­ga­tions un­der the New Zealand Bio­di­ver­sity Strat­egy of 10% pro­tected by 2010.

Given that 80% of our na­tional bio­di­ver­sity is found in the ocean, we need more ma­rine re­serves. “No fish­er­man needs more than 90% of the sea to fish in!” says veteran ma­rine bi­ol­o­gist, Dr. Roger Grace. “Ma­rine re­serves are the ‘Na­tional Parks’ of the sea, the only places where the full range of bio­di­ver­sity is pro­tected and can re­cover to its nat­u­ral state.” Re­cent re­search by WWF shows that 96% of Ki­wis want at least a third of our wa­ters to be pro­tected.

Grace ex­plains that ma­rine re­serves are also needed to en­sure fish pop­u­la­tions are not extracted be­low lev­els that are self-sus­tain­ing. The max­i­mum sus­tain­able yield (MSY), a sys­tem used to al­lo­cate fish­ing quo­tas, is very high for some species - for ex­am­ple 23% for snap­per. This means you can com­mer­cially catch snap­per un­til 23% of the orig­i­nal pop­u­la­tion size re­mains in our wa­ters - enough to en­sure ‘sus­tain­abil­ity’.

How­ever, a re­port re­leased in 2011 by the Min­istry of Fish­eries stated that “it is be­com­ing in­creas­ingly dif­fi­cult to jus­tify Msy-com­pat­i­ble tar­gets less than 30-40%”. In 2005, the Min­istry of Fish­eries re­ported that west coast snap­per pop­u­la­tions were sit­ting be­tween 8 and 12% of pre-fished biomass. These stocks are still be­ing com­mer­cially fished. Grace es­ti­mates that cray­fish biomass around the north-east coast of New Zealand could be as low as 1% of the orig­i­nal pop­u­la­tion.

Kina num­bers are con­trolled by large snap­per and cray­fish. As soon as we re­move these big crea­tures, kina pop­u­la­tions ex­plode, mow­ing down sea­weed forests. Com­plex ecosys­tems sup­ported by these forests are re­duced to kina-stud­ded ‘bar­rens’ - not a par­tic­u­larly in­spir­ing sight for snorkel­ers’ eyes.

Hav­ing more ma­rine re­serves can help bol­ster the fish pop­u­la­tion be­cause they act as nurs­eries, en­sur­ing pop­u­la­tion for fu­ture fish­er­men. “They pro­vide a haven for large, old an­i­mals which can breed in peace, spread­ing their prog­eny around the coast”, says Grace.

Big­ger preda­tors also pro­duce more eggs. A 12.5kg fe­male red snap­per has the same amount of eggs as 212 fe­males weigh­ing 1.1kg. The next time you reel in a 30-pounder, re­mem­ber that this egg-mak­ing ma­chine will be stock­ing our fu­ture fish­eries, and will prob­a­bly taste like an old boot, so do your grand­chil­dren a favour and throw it back.

There are over 30 ma­rine re­serves dot­ted around the coast. Make the most of the long-awaited sum­mer, and take a look at what a healthy ma­rine ecosys­tem can look like with our pro­tec­tion.

Pho­tos: Roger Grace Main pic: A net­work of Ma­rine Re­serves in Fiord­land pro­tects a rich bio­di­ver­sity with many deep water species liv­ing in ac­ces­si­ble shal­low wa­ters be­cause of the calm dark con­di­tions brought about by a tan­nin-stained fresh­wa­ter layer float­ing on the sea. Top inset: Large snap­per are now com­mon in Tawha­ranui Ma­rine Re­serve, which has been fully pro­tected since 1981. Snap­per and cray­fish have in­creased and elim­i­nated kina bar­rens, al­low­ing the kelp for­est to re­cover to nat­u­ral lev­els to­gether with its rich as­so­ci­ated bio­di­ver­sity. Bot­tom inset: Cray­fish have re­cov­ered to around 1000 per hectare at Tawha­ranui Ma­rine Re­serve in the ex­ten­sive kelp for­est. Else­where on the fished North­land coast you would be lucky to find 2 legal­sized crays per hectare on shal­low reefs cov­ered in kina, with lit­tle kelp.

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