West Coast Groundfish Observer Program Manual, Part2 - NOAA

CHAPTER 6
Subsamples may be taken using any one of the following
random sampling methods.
• Spatial – Randomly select a unit of gear or an area
(portion of deck or bin, specific basket) to collect
individuals from.
• Temporal – Randomly select a point in time to
collect individuals.
• Systematic – Select a random start point (spatial or
temporal) and take individuals at set intervals. In
order to use a systematic system you must know
approximately how many of the target species are in
the population.
Example:
1. The crew on a trawler is sorting out a scupper
and the Observer is whole hauling the discard.
2. The Observer estimates that 100 Pacific Ocean
Pearch (POP) will be discarded. There are no
other priority species present.
3. The Observer refers to the Biological Sampling
chapter in his manual and verifies that he needs
to take sexed lengths from 20 of the discarded
POP.
4. The Observer decides to do a systematic
subsample of the POP within his species
composition sample.
5. The Observer divides the estimated number of
POP in the haul by the number he needs to
sample (100 /20 = 5). This tells him he need to
collect 1 fish out of every 5.
1/30/2004 6-9