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Mapping the Distribution and Intensity of Bottom Trawling Effort along the California Coast from 1997 to 2009, with Impacts on Deep-Sea Corals

Project Goal

To create a series of maps showing the intensity of fishing with nets towed on the bottom off California from 1997 to 2009, and on the same maps display locations where corals have been found.

Geographic Location

Waters offshore of California from the Oregon border to the Mexico border beyond 3 nautical miles from shore out to waters 4,200 feet deep

Approach

Trawling locations and the hours fished, as recorded by the fishermen in logbooks submitted to the State, were used to create lines representing the individual tows of the net from start to end point. These tow-lines were overlaid with a grid of cells, and all the effort from three-year periods was summed to calculate the effort per square kilometer per year for each cell. To protect individuals’ confidential business practices, only cells fished by 3 or more vessels are displayed.

Results

Maps and their GIS layers were produced and submitted to the Deep Sea Coral Research and Technology Program. The maps show how the intensity of trawling effort varies with depth and location relative to where deep sea corals have been observed.

Importance to Management

These maps were presented to the Habitat committee of the Pacific Fishery Management Council to help them identify areas minimally impacted by trawling. Minimally trawled areas are more likely to have undamaged deep sea corals and sponges that could be protected and may be an important habitat for some fish.

Fiscal Year 2009 Funding

$32,637

Point of Contact

Janet Mason, Janet.Mason@noaa.gov

Map of waters off northern California showing intensity of trawling from low (dark blue) to high (green) for the 1997 to 1999 period. Trawling is not permitted within 3 nautical miles (3.5 statute miles) from shore in California and no deeper than 4200 feet. Corals of different types are indicated by colored circles.

Credit: Janet Mason, NOAA Fisheries SWFSC.