ecosystems and EFFECTS OF FISHING

Our fisheries are affected by many things, including complex interactions between the physical, chemical and biological components of the atmosphere, the ocean, and the sea floor. These vary naturally over time.

Some of these occur as short-term cycles on a daily, seasonal or annual basis; some are longer term over decades or more.

Fisheries are also affected by human activities: the direct and indirect effects of fishing, the effects of terrestrial runoff; and the effects of introduced marine pests.

Knowing about these processes and effects, and how they affect fish stocks, is an important part of making decisions about what catch levels are appropriate, and what environmental effects are acceptable.

Biodiversity and ecosystems

The science group provides the baseline information on biological diversity in our marine ecosystems. It also provides information on how this exists within the wide picture of climate cycle and ocean processes.

The group oversees and develops research programmes, in conjunction with a range of government agencies and research providers.

These are closely linked with the 'effects of fishing' research programmes.

Current work areas in biodiversity include:

• ‘Big-picture’ ecosystem and ocean process issues in offshore environments.

• Marine habitats and their communities, and how they contribute to ecosystem processes. This work will particularly tell us more about the effects of bottom trawling and dredging on the wider ecosystem.

• Nearshore marine ecosystems; including how changing climate, terrestrial runoff, or upsetting the food chain can affect these ecosystems and their associated fisheries.

• Biodiversity and ecosystems in the Ross Sea region of Antarctica.

Effects of fishing

The effects of fishing on the aquatic environment fall into five broad categories:

• harm to protected species (marine mammals, seabirds, turtles, etc.);
• incidental catches of other fish and marine life;
• damage to sea bed habitats by trawling and dredging;
• upsetting the balance of ocean ecosystems; and
• upsetting the balance of natural genetic selection in a species.

The Ministry sets limits around the effects of fishing on the aquatic environment. Its process for setting these (Strategy for Managing the Environmental Effects of Fishing) first involves answering three questions:

Can the environment handle the effects?

What does society think about these effects?

What are we leaving for future generations?

The science group provides information and advice to answer the first of these questions.

To date, the most progress has been made in estimating the catches of protected species and other bycatch in offshore trawl fisheries. Significant progress has also been made in describing the effects of trawling and dredging on some seabed habitats.