IV- 6
Monthly Survey Effort and Catch Extrapolation Methods
To estimate the total number of trips taken by all RCGL holders, the monthly survey data
are extrapolated for each monthly sample period and gear combination by:
• Calculating the level of participation by dividing the total number of participants actively
using a specific gear by the total number of returned questionnaires,
• Calculating the mean number of trips taken by the participants indicating actively using a
specific gear, and
• The effort estimate is the product of the mean number of trips, level of participation, and the
total number of RCGL holders for the given sample period.
Determination of the estimated catch for each species is also calculated for each sample period
and gear level by:
Summing the total catch by species, sample period and gear combination
Summing the total number of trips taken by sample period and gear combination
Dividing total catch by the total number of trips to determine the mean catch for each
species for every sample period and gear combination, and
The catch estimate is the product of the mean catch and the estimated effort.
The margin of error ( 95% confidence interval) of the proportion actively using their RCGL
license is calculated based on the number of returned surveys and the size of the RCGL
population for each monthly RCGL population ( Lenth 2002).
Quantities of Gear Used ( monthly surveys)
The participants are asked to specify the average amount of gear used. Quantities were
categorized into ranges of values for the yardage of gill nets, head rope length of trawls, and
length of seine. Gears such as eel and crab pots were simply enumerated. Range, average,
median, and mode are calculated for the quantity of each gear type.