West Coast Groundfish Observer Program Manual, Part2 - NOAA

CHAPTER 5
around the waist. Observers should be creative,
experiment, and find out what works best.
When tally sampling, all individuals should be recorded to
species. Some species are similar in appearance so it may
not be possible to distinguish them to species. Examples
of these are Rougheye and Shortraker rockfish or
Shortspine and Longspine thornyheads. It is acceptable to
tally these species to mixed groups such as
Rougheye/Shortraker and Shortspine/Longspine.
Tally Random Sampling Methods
There are three types of random sampling on fixed gear
vessels, spatial, systematic, and temporal. In all three types
of longline sampling, begin sampling on a skate knot.
In the explanations below all the gear subunits
(skates, pots or poles) are generically referred to as
“skates”.
Systematic Sampling (preferred)
Fixed-gear vessels routinely set over of a depth gradient or
across different bottom types. This means the catch can
vary significantly along a set. The best way to account for
the variability caused by setting across a depth gradient or
different bottom types is to use a systematic spatial random
sampling frame. The procedure for systematic spatial
sampling is as follows:
1. Verify how many skates are in the set.
2. Decide how many skates to sample, making sure to
sample at least 1/3 of the set.
3. Break the set into sampling segments (n) by dividing
the total number of skates by the number of skates
that will be sampled. For example, there are 12
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