In brief: NIWA takes to the skies to map seabed

Aerial photography is being used to map the shallow-water habitats of the southern Kaipara Harbour. The technique allows NIWA scientists to identify seagrass meadows – important for sustaining coastal fisheries such as snapper – down to their maximum growing depth of 3 to 4 metres below the low tide mark.

By combining aerial photography with fish sampling, NIWA can map the location of critical fish nurseries, and monitor their health over time through remote sensing.

Fish were collected using small, hand- hauled, fine-mesh beach seines, pulled up onto a specially designed ramp deployed from an oyster barge. About 100 sites were sampled, spread across 150 square kilometres in the southern Kaipara.

The habitats provide a range of important ecological 'goods and services', such as seagrass material which finds its way into food webs and small invertebrates associated with seagrass meadows.

Dr Mark Morrison, Marine Ecologist, said that underwater seagrass meadows were critical to supporting high numbers of juvenile snapper, trevally, parore, spotties, piper, pipefish and other species, particularly in northern New Zealand.

"This study examines what components of these habitats are most important to small fish. It samples across seagrass habitat landscapes and quantifies where fish densities and numbers of species are highest.

"Sampling quantifies what fish species are associated with each habitat type and associated environmental conditions. That means we can identify which factors are most critical for supporting particular types of fish species, so that the most important habitats can be identified, mapped and protected."

The aerial photography was funded by the Ministry for Primary Industries (MPI), while the fish-sampling research is being funded by the Ministry of Business, Innovation and Employment (MBIE).

Ministry for Primary Industries website 

Ministry of Business, Innovation and Employment website