The provisional categorisations for 2019 were published yesterday by the Scottish Government: https://www.gov.scot/Resource/0054/00542420.pdf. It is proposed that the River Alness will change from Category 3 to Category 1, meaning the end to the mandatory 100% catch & release in place this season.
The 2019 assessment https://www.gov.scot/Resource/0054/00542418.pdf explains the changes to the model, which includes "The updated methods remove any geographic component from the process with the relationship between catch and salmon numbers being determined by month and the flow conditions. The rod catches and the estimated adult abundance can then be compared to produce an annual exploitation rate for each assessment areas."
There are also several references to criticisms and comments from stakeholders e.g. "The changes to the assessment model have been made in response to criticisms that we have previously adopted an approach which has been too precautionary and too general. While we are maintaining our precautionary approach overall, the latest model focuses better on individual rivers or areas and is a significant step forward in terms of improving and refining the science behind our approach. This leads us to believe that properly managed exploitation of salmon stocks can allow for the retention of fish on a higher number of rivers."
Category 1 advice also includes the comment ”This recognises the effectiveness of existing non-statutory local management interventions.”