The effective swept volume of a bottom trawl
Original version
This report is not to be cited without prior reference to the authorsAbstract
The reaction of individual fish towards an approaching trawling
vessel has previously been measured using target-tracking methods. In
this paper these measured velocities are fitted to a deterministic mean
behaviour model and a diffusion-advection model taking the random
component into account. The output of the diffusion-advection model
is used to estimate the probability of a fish to be caught by the bottom
trawl. For typical depths in the Barents Sea, 200 - 350 m, and for
immature Cod feeding on capelin, a mean fishing height of about 10
metres is found, and the effect of horizontal herding from the warp
is shown. The effect of random fish movement is visualised by the
different results from the two models.