The benthic ecology and community structure in Lyttelton Harbour ...

10.
s ledge for future sampling wit-h the occasional use of
the plankton sampler.
the use of the orange peel grab were;
The reasons for discontinuing
1. it was too heavy, and overtaxed the winch'
gear on the boat;
2. the area sampled by the jaws was difficult
to calculate;
3. the depth of penetration varied greatly with
the type of substrate;
4. the jaws were often jammed open by gravel and shells
and
5. the sample was washed on the way up even
though a canvas cover had been placed over
the jaws.
Quantitative sampling does not allow any of the above
errors. The box dredge had a known capacity of 0.03
cubic metres and dug to known depth so the area and
volume sample could be reliably calculated.
1.6 Sampling techniques
Sampling was carried out over transects covering
areas of interest, generally crossing regions of variable
substrate~
The boats, initially the "Trade Wind" owned
by Mr E. Johnstone and later the "Pup" skippered by
D.J. Partington, were allowed to drift with the wind and
swell using the dredge. Experiments by MacIntyre (1964)
showed that the dredge dug on the downstroke of the
swell ~nd was stationary on the upstroke. This redu~ed
the bouncing that was apparent when it was being continually
pulled. Five minutes was enough to fill the
dredge box on any surface; usually less time was sufficient.
When the epibenthic sledge was being used the