No-fish zone protects life on the seabed

No-fish zone protects life on the seabed

Grab samples showing the amount of biomass from the fished zone (left), and the protected zone (right). (Photo: Sean Handley, NIWA).

Seabed communities at Separation Point, Nelson, have been left more-or-less untouched since 1980, when the area was closed to power fishing. NIWA scientists studying the communities have found clear evidence of the benefits of that protection.

The area, between Tasman and Golden Bays, was closed to protect various species of bottom-dwelling (benthic) bryozoans living on the soft seafloor sediment. Bottom-trawling and  dredging were predicted to rapidly destroy the bryozoans’ fragile structures, and the habitat created by the bryozoans was protected as a nursery for juvenile finfish.

Recent sidescan sonar images of the seafloor show a rich bryozoan community thriving within the protected zone, compared with a soft mud-dominated seafloor outside the zone’s boundary. Similarly, grab samples from the protected zone are full of organisms of many species, whereas samples from the fished area are mainly fine mud, containing fewer organisms of lower diversity.

“Our next job is to look beyond the direct impacts of the closure,” says NIWA’s Dr Sean Handley. “We want to answer the bigger question: how does protecting bryozoans at Separation Point affect the many species which make up the wider ecosystem associated with them?”

Research subject: Coasts