Tuesday 3 June 2014

Pick a grab, any grab

For 17 days now, we have been grabbing bits of the Dogger Bank seafloor in order to better understand the habitats and communities that live there.

Today we are entering a new phase of the survey in which we’re going to use 5 different grabs to collect samples from a smaller area within this marine protected area.

The reason behind this extra effort is the need to compare our data with data collected in previous studies and by international colleagues using different grab equipment. Analysis of samples collected from different grabs can give different results. This is thought to be due to the differences in the way these grabs operate as well as their specifications.

Mini Hamon grab being deployed (A. Cunha JNCC)

The mini and large Hamon grabs for example, are effective for sampling fine and coarse sediments and have been widely used in the United Kingdom.

A Shipek going into action (A. Cunha JNCC)
The Shipek grab is smaller and used mainly for sediment particle size analysis; it is better suited for coarser sediments. The Day and Van Veen grabs are good for sampling fine and sandy sediments but are prone to getting stones caught in their jaws which can result in part of the samples being lost.

New grab induction day  (A. Cunha JNCC)

Because the Van Veen grab is a new piece of equipment on board of the Cefas Endeavour, a Risk Assessment  protocol has been created and everyone on board that will eventually use or help using this grab had to participate in a full demonstration of all possible hazards and risks.

The Van Veen being inspected by the Master, the Chief Scientist
and the engineers on board (A. Cunha JNCC).

A Van Veen grab being deployed by crew members  (M. Nelson JNCC)
We hope that the findings from this part of the survey will help us gain an insight into how data collected using different grabs vary and allow us to better compare our results with those collected in other studies at Dogger Bank.