Habitat Protection and Research
It is widely accepted that some fishing methods, such as bottom trawling and dredging, impact on the seabed and may cause damage to marine habitats and ecosystems. Most fishing of this type occurs in water depths of less than 1200m (these make up around 30 percent of our economic zone).
The Ministry of Fisheries has recognised this problem and has a number of closures in place to protect the seabed. The Ministry has also commissioned a range of research projects to find out more about seabed habitats and communities and how they are affected by bottom trawling and dredging.
Current and Future Management
Policy and strategic frameworks to implement sea-bed protection have been under development for sometime now, and include the Strategy for Managing the Environmental Effects of Fishing and the Marine Protected Areas Policy and Implementation Plan.
The government has already closed a number of areas to trawl and dredge fishing. These include coastal trawl and dredge closures to protect sponge gardens in Spirits Bay (Northland) and bryozoan reefs off Separation Point (Tasman region).
There are also a range of Seamount Closures (announced in November 2000) and Benthic Protection Areas (announced in April 2007) across New Zealand’s offshore waters.
Combined, these protect about 32 percent of deep water habitats from bottom trawling and dredging. These measures are a step towards meeting objectives in the New Zealand Biodiversity Strategy and ensuring that pristine areas of ocean sea-bed are maintained for posterity.
The government’s approach to protecting seabed habitats was outlined in the Strategy for Managing the Environmental Effects of Fishing (SMEEF) that was launched in 2005. This approach will be to set standards based on the relative vulnerability of habitats (standards will determine how much of each habitat will remain free of impact). The assessment of vulnerability will incorporate the relative resilience of biological and physical components of each habitat, the reversibility of the impact and the relative importance of the habitat to ecosystem function.
The effect of bottom trawling depends on the extent of trawling, the type of habitat affected, and how much of that habitat exists.
The government realises that impacts will occur when fishing, just as impacts occur on land, but wants to constrain those impacts so they do not become adverse. Working out the point at which an impact becomes an ‘adverse effect’ is difficult and will no doubt be controversial, but that is the role of the standard-setting process.
Work is underway to assemble all the available information, and fill in critical knowledge gaps with new research. The research projects are tailored to provide the most cost-effective way of providing guidance on the impacts of fishing and what measures can be developed to usefully provide a way of assessing risk, vulnerability and resilience. Habitats will be mapped, and standards as described above will be developed. Decisions can then be made about the need for, and location of, any further closures.
Benthic Impacts Strategy
The Benthic Impacts Strategy sets out the government’s process for setting limits around the effects of fishing on sea-bed habitats. The limits are called Habitat Standards.
A Habitat Standard will define how much of each sea-bed habitat must remain free of damage, including from fishing. This will ensure that the effects of fishing do not stop sea-bed habitats functioning and contributing effectively to fish production and the marine ecosystem.
The standard will be based around an assessment of the risk that fishing poses to each habitat type in question.
The assessment will take into account:
- how sensitive the biological and physical components of each habitat are;
- the reversibility of the likely impacts; and
- the relative importance of the habitat to ecosystem function.
The first step in the process is to identify the range and location of broad sea-bed habitat types in New Zealand’s Territorial Seas (within 12 nautical mile of the coast) and offshore areas.
A habitat type is made up of physical attributes (like what the sea-bed is made of and how deep it is) and the plant and animal communities living there
To start with, habitat types will be identified from existing national classification systems and databases, but will be modified as more information becomes available.
The Ministry of Fisheries is currently undertaking, or plans for 2007/08, a range of research projects that will give more information on sea-bed habitats, particularly soft-sediment and seamount habitats in offshore areas.
The extent and intensity of fishing in this depth zone varies considerably, and a current project is mapping the footprint of trawling and dredging over the past 16 years to characterise trends in fishing patterns and changes in effort as fishing fleet behaviour has changed over time.
Zoning the ocean and mapping habitats from an ecological standpoint is not straightforward. Several projects have studied seamount habitats and it has been widely accepted that the benthos living there can be fragile, very long-lived and vulnerable to fishing. A current study is comparing recovery rates on seamounts closed to fishing with those where fishing has continued. However, seamounts form just a fraction of the seabed area, and attention is now turning to soft sediment habitats that underpin many of our largest trawl and dredge fisheries.
A recently completed project showed that the utility of the Marine Environment Classification system (which the fishing indudtry used as a starting point for proposing BPAs) in predicting broad-scale habitat types from physical and oceanographic information (e.g. water temperature, depth, slope, etc) can be significantly improved by adding biological information.
The most comprehensive biological data available is the distribution and abundance of fish species, some of which are closely associated with sea-bed habitats. Existing data about sea-bed invertebrates are also being tested for use in the Marine Environmental Classification system. However, information about soft sediment sea-bed communities in New Zealand is not comprehensive and the Ministry is seeking to improve the situation.
A multi-agency project to map sea-bed biodiversity and habitats on the Chatham Rise and Challenger Plateau will yield new information about offshore soft sediments and their associated communities from depths of 200 to 1200 m.
New work to assess the effects of trawling on different habitat types is also planned for 2007/08.