There are many environmental issues facing fisheries in New Zealand and around the world.
Bottom trawling is where fishing boats drag large nets along the sea floor. Trawling is the most important commercial fishing method in New Zealand, especially for deep-water fisheries such as orange roughy, hoki, and ling. However, research indicates that this form of fishing can seriously damage life on the sea floor.
The New Zealand Government has started working out ways to limit the damage in our seas. These include setting up areas such as marine reserves, mātaitai reserves, and areas where certain fishing methods cannot be used. And a proposal from the commercial fishing industry has led to more than 30 percent of New Zealand’s Exclusive Economic Zone being protected from bottom trawling and dredging.
Climate change affects many parts of our environment, including our oceans.
According to a United Nations Environment Program report, rising sea temperatures could:
- kill coral reefs
- threaten spawning grounds
- change ocean currents
- raise sea levels.
Rising temperatures around the globe will lead to the ice caps melting and sea levels rising. Rising sea levels will affect our beaches and coastlines as well as the marine life. The sea level around New Zealand has risen an average of 16 centimetres in the last 100 years, and scientists from the Intergovernmental Panel on Climate Change predict that it will rise more than double that amount in the next 100 years.
Soil and nutrient run-off from the land when it rains can greatly affect our coastal ecosystems. When the run-off pours into harbours and estuaries where the water is quite still, it drops down to settle on the sea floor. This is called sedimentation. Too much sediment can smother shellfish beds and other important marine habitats.
Scientists from the National Institute of Water and Atmospheric Research (NIWA) have researched the effects of sediment and found that baby paua and kina find it hard to survive with more sediment in the water. They also found that sediment affects the tiny animals living on kelp. Since these animals are a major food supply for many small fish, which in turn are a food supply for larger fish, it seems that high sediment levels could affect whole marine ecosystems!
Sedimentation results from the way we use the land for agriculture, forestry, or housing and roads. We can reduce the effects of sedimentation by managing the land well. This includes planting stream banks and eroded hillsides to help stop run-off and finding ways to reduce the amount of sediment and pollution that we allow to run into our streams, rivers, and oceans.
Threatened marine species
There are 444 threatened marine species in New Zealand waters. These include:
- Hector’s & Maui's dolphins
- many of our seabirds
- New Zealand sea lions.
Many things threaten these species, but fishing is one of the biggest threats:
- Dolphins can get caught in fishing nets, especially set nets, and drown.
- Seabirds risk getting caught on hooks in long-line fisheries when they try to grab bait from the lines. If they are caught on the hooks, they can drown. In trawl fisheries, they can get caught and drown in nets as they try to take fish from them.
- New Zealand sea lions can also get caught and drown in trawl nets as they try to feed on squid caught in the nets.
There are a number of management measures in place to help protect these species.
- A Threat Management Plan is being developed for Hector’s dolphins.
- A National Plan of Action is in place to protect seabirds.
- Boats in the southern squid fishery, around the Auckland Islands, use sea lion exclusion devices (SLEDs), which help sea lions escape from their trawl nets. There is also a limit on how many sea lions can be accidentally killed – when that number is reached, the fishery is closed until the next year.