Incorporating conservation limit variability and stock risk assessment in precautionary salmon catch advice at the river scale

Abstract

Abstract International wild Atlantic salmon management priorities have moved from exploitation to conservation since the 1990s, recognizing the need to protect diversity and abundance at individual river levels amid widespread declines. Here we review international salmon-stock assessments and describe a simple, transferable catch-advice framework, established for management of fisheries that conforms to international obligations. The risk assessment approach, applied at the river scale, jointly incorporates uncertainty in estimated and forecasted returning salmon numbers with the level of uncertainty around spawning requirements (Conservation Limits). Outputs include quantification of risk of stocks not attaining conservation limits (CL) and surpluses above CL on stocks able to support sustainable exploitation via total allowable catches (TAC), with monitoring by rod catch or fish counter. Since management implementation and cessation of at-sea mixed-stock fisheries, there has been a deterioration in the performance of many individual stocks, without any sustained increase in fisheries open to harvest. Given declines in mid-latitude Atlantic salmon populations over 30 years, the novel framework presented provides an approach to protect stocks failing to meet spawning thresholds while supporting sustainable exploitation of those achieving them. On-going management policy of adopting scientific advice and allowing exploitation only on stocks exceeding CLs is central to the objective of protecting salmon stocks.