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Area swept by commercial trawlers

Trawling on or near the sea floor is the most widespread fishing activity in the New Zealand marine area that physically affects the seabed. From 1990, trawl effort by vessels required to report accurate fishing locations (TCEPR vessels) increased from fewer than 40,000 sweeps by trawls per year by about 127 vessels to a peak in 1998 of almost 80,000 sweeps per year by 173 vessels. In 2005, this number had dropped to under 55,000 sweeps per year by 94 vessels.

At the same time, the total area swept increased from 35,000 square kilometres in 1990 to a peak of more than 67,000 square kilometres in 1998. On average, the total area swept remained between 55,000 and 62,000 square kilometres in subsequent years until 2004. By 2005, the area swept had decreased to about 50,000 square kilometres, probably due to reductions in the total allowable catch for some species.

On average, around 55,000 square kilometres were trawled each year between 1990 and 2005.

Commercial trawling effort (total area swept in square kilometres) by Trawl Catch Effort Processing Returns (TCEPR) vessels, 1990–2005

Graph of commercial trawling effort by Trawl catch Effort Processing Returns vessels, 1990 to 2005

View data in a table (text description) for above graph

Data source: National Institute of Water and Atmospheric Research.

Location of commercial trawling effort

The map below reports on where commercial trawling effort occurred in New Zealand by showing the total area swept (in square kilometres) in each 25-square-kilometre ‘cell’ fished. Sixty-four thousand of these cells are in fishable depths (less than 1,600 metres deep). Overall, 58 per cent of cells at fishable depths were crossed by at least one trawl over the 16 years for which there is data.

Trawling effort by year rose from 20 per cent of fishable cells in 1990 to 30 per cent in 2002, and then decreased to 25 per cent in 2005. The data shows the majority of the fished cells have had less than 1 square kilometre swept by trawls over the 16 years.

Location of commercial trawling effort (total area swept in square kilometres within 25-square-kilometre cells) by Trawl Catch Effort Processing Returns vessels, 1990–2005

Map showing location of commercial trawling effort (total area swept in square kilometres within 25-square-kilometre cells) by Trawl Catch Effort Processing Returns (TCEPR) vessels, 1990–2005

Note: This figure has been produced using the Mercator projection.

Text description for above map

Data source: National Institute of Water and Atmospheric Research.

 

Many areas in the Exclusive Economic Zone are not targeted by trawling. Even if the area is of a fishable depth, catches may not be high enough to be economic.

Areas of higher trawling intensity are those where hoki, squid, orange roughy, scampi, or snapper are targeted.

The distribution of trawl effort changes from year to year, but the data does show a pattern of initial expansion of trawl effort to the east and south of New Zealand. This initial expansion is mainly due to trawl effort targeted at hoki, but has shrunk in recent years (as the hoki catch has decreased).

 

The above information has come from the latest national state of the environment report, Environment New Zealand 2007.

 

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Last updated: December 2007