Rockfish Population Survey

The Moody Blue off Banks Island.

This project involved designing a method of doing a rockfish population survey quickly, cheaply, and without harm to the fish. The method is based on the techniques used to fish lingcod, except that hookless lures are employed, and a video camera is used to count and identify the fish that come to investigate the lures.

The current working depth of the equipment is 100 m, based on the present length of the video cable. This equipment can be used in very rocky-bottomed environments, and can accurately survey very small areas. As the gear will not touch the bottom or harm the fish, it can be used in marine protected areas and other environmentally sensitive regions. Survey runs can be done much more quickly, safely, and deeply than those performed by divers, and can be performed in regions where tidal currents would make other methods impractical.

To ensure good coverage, the survey of the site consists of transects in a grid pattern. The bottom contours are followed as closely as possible with the camera.

The camera is connected to a computer monitor and a digital video recorder for live viewing and recording. Data is logged in real time, with position and time data stamped as an overlay on the video. The bathymetry of the site can also be recorded during the survey. Using GIS software, a detailed 3D map of the survey site can be generated, illustrating the rockfish distribution at the site.

Each site survey generates a DVD which contains both a hydrographic chart showing the track lines of the survey, and the videos with the logged data showing the position of each fish. Mapping and other GIS information can also be added.

Video footage of the fish can be taken using color, black and white, or infrared cameras. Infrared lights will be tested to see if they are less intimidating to the fish.

Note that this equipment can be used to survey any type of fish that will be attracted to a lure, and can be used for midwater, as well as bottom, surveys.

Click image to enlarge.