Updated catch length frequencies for the Tristan group of islands using factory pack category data

Abstract

Reliable factory processing records of lobsters caught at all four islands of the Tristan group are available since 20011 . These “pack category” data record the number of lobsters that fall into different packing categories. There are two types of product for which data have been collected: “tails” (where only the tails are packed into cartons) and “whole” where either whole cooked or whole raw frozen lobsters are packed. The pack-categories however refer to certain weight ranges, with different categories applying to “tails” and to “whole” product. Tables 1a and b list the pack categories and the associated weight ranges. Johnston (2010) applied the method described below to convert factory pack category data into catch length frequencies for data for the period 2001 – 2008. Recently, two further year’s of factory pack category records have become available, and this document serves to update the work presented in Johnston (2010) with the 2009 and 2010 data.