Bite profiles of some benthic grab samplers

The bite profiles of six 0·1 m² benthic grab samplers were reconstructed from video recordings of closure. The Petersen and the chain-rigged van Veen grabs both took shallow bites of variable profile; the Day and the Smith-McIntyre grabs both took fairly deep and consistent bites but were prevented by their frames from using their momentum on landing to increase penetration; two designs of warp-rigged van Veen grab both took deep, parallel sided bites. The long arm, warp-rigged van Veen was the only grab to collect sediment from a depth of at least 50 mm over the entire 0·1 m² sampled. A bucket shape, designed to optimise penetration and minimise upwards movement on closure, is suggested. © 1989.