A key part of DIT analysis for identifying differential harvest rates by fishery is to have the catches in each fishery to be electronically sampled. That is both marked and unmarked need to be examined to see if they contain a CWT (in those "keep anything" fisheries). This hasn't been the case but I don't know what the situation is now. Alaska was a holdout for a long time in that they didn't look at unclipped fish for CWTs. The lodge fisheries in BC were another problem for unmarked. But in essence if only some of the fisheries are sampled then doing DIT analysis is much more complicated and requires some major assumptions.

So using DIT groups for evaluating individual fisheries is problematic because of these sampling issues. However, the differences in escapement numbers for the unmarked and marked tag groups can quickly be used to get an all-fishery difference in exploitaiion rates between the two. What has been found that the higher the proportion of the stock that is exposed to MSFs, the greater the difference in escapement rates between the unmarked and marked groups. EG PS stocks generally show a greater gap between the two than Col R tules for example. But the data is messy and sometimes down track with expectations very well.

Just Because is correct that doing DIT groups requires essentially double the number of released fish and CWTs. That luxury isn't there for Stilly.