Boat-Based Creel Survey Processing
From 1982 until 1990 the monthly and annual values of Pounds Caught or Total Landings, Pounds Sold or Commercial Landings and Value for the individual species used in the Estimated Commercial Landings Graphs, Estimated Total and Commercial Landings Tables, Pelagic Plan Team Report Graphs and Tables and Bottomfish Plan Team Report Data was calculated from Boat-Based Creel Survey Data in the manner described below
Data collected from 1982 to October 1985 was from a simple Survey of all commercial fishing trips in Tutuila and Manua adjusted upward by the percent coverage to account for missed trips.
In October 1985, the present sampled Boat-Based Creel Survey System was begun in Tutuila. The data in Manua continued to be collected as a simple Survey of commercial and non-commercial Fishing Trips with the Manu`a statistics compiled on a monthly basis and adjusted by an estimated percent coverage factor that is usually 100%.
The data from the Tutuila Boat-Based Creel Survey System was expanded for the non sample days to get estimates of Tutuila landings separated into Commercial (Pounds Sold) Landings and Total (Pounds Caught = Pounds Sold plus Pounds Not Sold) Landings. The expansion stratifies the data by fishing method and by type of day (weekday or weekend/holiday) to improve the final estimates of landings by species. The expansions are done over a monthly period for monthly data and over an annual period for annual data thereby increasing the sample size and hence the accuracy of the annual data significantly. Because of this the annual values will not equal the total of all of the monthly values for the year.
The expansion first calculated the number of boat trips for each period and stratum. It then calculates the average catch, species composition and percent sold for each species per boat trip for each period and stratum. It multiplies this by the number of boat trips for each period and stratum to get the expanded Total Landings and Commerecial Landings for each species for Tutuila. The adjusted landings data for Manu'a was added to the Tutuila landings creating the Commercial and Total landings estimates for all of American Samoa.
In cases where there are boats trips for a particular stratum and period but less than three interviews for that period and stratum an interview pooling system was implemented. In these cases interviews are borrowed first from trips of similar fishing methods, next from trips on the other type of day and finally from trips one or two periods before or after the period in question. These interviews are combined with any interviews for the period of question until there are at least three.
To calculate CPUE's for each stratum and period all of the pooled interviews for that stratum and period are combined. The CPUE is calculated as the sum of the catch for those interviews divided by the sum of the effort for those interviews.
Because price information was not obtained for all landings that were sold, the commercial data was edited to create price information when none was available. To accomplish this, a three-tiered editing system was designed to "create" price estimates based on the best information available. The edit system puts average price information in each record where it is missing, based on the following three levels of available information:
1. If price information is available for the same species in the same month, the weighted average price per pound is written into all records missing that information for that species and month.
2. If no price information is available for the same species and same month, the annual weighted average price for that species is written into records for that species and month.
3. If no price information is available for a species for the entire year, the program prompts the user for input and updates the file based on the response.