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7. ACTIVE DAYS SURVEYS


7.1 OBJECTIVE
7.2 DATA RECORDING

7.1 OBJECTIVE

Active Days Surveys are usually carried out at the end of the month, when all sampling has finished and estimates are about to be produced. Its objective is to determine a time raising factor for estimating total fishing effort.

7.2 DATA RECORDING

The following theoretical example illustrates a simple way of recording Active Days for each estimation context (minor stratum, month and boat/gear type) through discussions with fishers at the end of each month, since Active Days do not remain constant over time.

In the example there are two minor strata (SW Coast and NE Coast) and five boat/gear types, comprising gillnets, beach seine, hook and line, traps and shrimp trawlers. Each combination of minor stratum - boat/gear type requires an indication as to the number of active days to be used as time raising factor for the given survey period.

Estimation of fishing effort for June 2001 - Active Days

Minor stratum

Boat/gear type

Active Days

Remarks

SW Coast

Gillnets

24

2 days of bad weather
No fishing during 4 Sundays

Beach seine

26

No fishing during 4 Sundays

Hook and line

26

No fishing during 4 Sundays

Traps

29

2 half-days of bad weather

Shrimp trawlers

-

No such boats in stratum

NE Coast

Gillnets

26

No fishing during 4 Sundays

Beach seine

30

All days potentially active

Hook and line

-

No such boats in stratum

Traps

-

No such boats in stratum

Shrimp trawlers

30

All days potentially active


To be noted that:

It is possible that an event will affect only part of a fishery. For instance, bad weather may only affect half of the boats of a certain category. For the boats with traps in SW Coast bad weather affected only half of them, meaning that only one day (or two half days) were subtracted from 30. Such refinements are of course useful but not always feasible.

SUMMARY

In this section supplementary guidelines regarding the use of time raising factors known as Active Days were considered, noting that:

  • Active Days are very important and greatly affect the estimation of total fishing effort.
  • Active Days express, in a uniform manner, periods during which fishing activities can potentially occur. In contrast to Boat Activity Surveys, they do not account for trip variability of individual boats.
  • Active Days are area- and boat/gear-specific.
  • Active Days can simply be set to the number of calendar days in a month when sampling in time is frequent enough to cover both normal and exceptional (low or zero activity) events.


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