Loss of marine habitats

Part 2 of the Marine Ecology course is about the flora and fauna and their habitat.  This is getting to the heart of why I took this course.

Reading about shellfish on the Te Ara website (The Encyclopaedia of New Zealand), I read this about dredge oysters (or Bluff or flat oysters, or tio):

“After 140 years of dredging, most mullock reefs in Foveaux Strait have been destroyed by heavy equipment, and few sites are available for young oysters to settle. The oyster population in the eastern Foveaux Strait has never recovered since the 1950s, and neither have the mullock reefs. Some environmentalists believe the fishery will collapse if destruction of the reefs continues.”

And from a section on corals:

“Deep-water trawling for orange roughy fish has damaged some coral banks – centuries will pass before their habitat recovers.”

That is why you’ll find oysters in the red zone of Forest & Bird’s Best Fish Guide (see Blogroll links on the left) and orange roughy at the very bottom.

In an unbiased report that summarises the marine biodiversity of NZ, threats are listed as follows:

“fishing, mining, chemical pollution, coastal nutrient and sediment input, habitat loss, aquaculture, invasive species, harmful algal blooms, and climate change. ”  The report goes on to note the effects of these, notably fishing, which “comprise overfishing, habitat modification or destruction, bycatch depletion, and diminishment of ecosystem services because of biodiversity loss.  Impacts that have been documented in coastal waters are now mirrored in the deep sea ….. One study recorded 96 species (many undescribed) of invertebrate bycatch from a deepwater trawl fishery…..The effects of commercial trawling … are well known on soft bottoms in relatively shallow water, in which a single trawler may easily disturb 10km2 in a single day’s fishing. ”  (Gordon, 2010).

There appears to be a general acceptance that common commercial fishing practices are unsustainable, but when it comes to buying fish, from the supermarket, fish and chip shop or restaurant, how many of us ask about the source or fishing methods? 

In the UK, the campaign to raise awareness and change fishing regulations is well advanced, but, here in NZ, campaigns are only nibbling around the edges through Forest & Bird’s Best Fish Guide and Greenpeace efforts.  Habitat is being destroyed, bycatch is being disregarded, species are being pushed to extinction.  The fight needs escalating.  If eating habits don’t change, fishing methods won’t change, and collapse of fisheries and ecosystems will follow. 

In the words of a song my father used to sing – “when will they ever learn?”




Gordon DP, Beaumont J, MacDiamid A, Robertson DA, Ahyong ST (2010).  Marine Biodiversity of Aotearoa New Zealand, PLoS ONE.  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2914018/?tool=pubmed


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