STATUS OF THE RIVER TANA SALMON POPULATIONS 2016 Report of the Working Group on Salmon Monitoring and Research in the Tana River System Cited as: Anon. (2016) Status of the River Tana salmon populations 2016. Report of the Working Group on Salmon Monitoring and Research in the Tana River System. CONTENTS Summary ................................................................................................................................................................. 5 Sammendrag ......................................................................................................................................................... 23 YHTEENVETO ........................................................................................................................................................... 41 The group mandate and presentation of members ............................................................................................. 60 1 Introduction ................................................................................................................................................. 61 1.1 Purpose of the report .......................................................................................................................... 61 1.2 Premises of the report ........................................................................................................................ 61 1.2.1 The Precautionary Approach .......................................................................................................... 61 1.2.2 Single- vs. mixed-stock fisheries ..................................................................................................... 62 1.2.3 Management and spawning targets ............................................................................................... 62 1.2.4 Data basis ........................................................................................................................................ 62 1.3 Explanation of terms used in the report ............................................................................................. 62 2 The River Tana, the Tana salmon and salmon fisheries ............................................................................... 64 2.1 The Tana and its salmon...................................................................................................................... 64 2.2 Tana salmon fisheries .......................................................................................................................... 68 3 Threat factors ............................................................................................................................................... 74 3.1 Review of individual human-caused threat factors ............................................................................ 75 3.1.1 River regulation (hydropower) ....................................................................................................... 75 3.1.2 Water use ....................................................................................................................................... 76 3.1.3 Acidification .................................................................................................................................... 76 3.1.4 Physical habitat modifications ........................................................................................................ 76 3.1.5 Agricultural pollution ...................................................................................................................... 76 3.1.6 Mining activity ................................................................................................................................ 76 3.1.7 Other causes of pollution ............................................................................................................... 76 3.1.8 Gyrodactylus salaris ........................................................................................................................ 76 3.1.9 Salmon lice ...................................................................................................................................... 77 3.1.10 Infections related to fish farming ............................................................................................... 77 3.1.11 Other infections (not related to fish farming) ............................................................................ 77 3.1.12 Climate change ........................................................................................................................... 77 3.1.13 Escaped farmed salmon ............................................................................................................. 77 3.1.14 Invasive (or introduced) species ................................................................................................. 78 3.1.15 Overexploitation ......................................................................................................................... 79 3.1.16 Predation .................................................................................................................................... 79 3.2 Ocean conditions ................................................................................................................................ 79 3.3 Overall view of Tana salmon threat factors ........................................................................................ 80 4 Stock status evaluation ................................................................................................................................ 81 4.1 How to evaluate stock status? ............................................................................................................ 81 4.2 Salmon production and spawning targets .......................................................................................... 81 4.3 A procedure for target-based stock evaluation .................................................................................. 84 4.3.1 Estimating target attainment .......................................................................................................... 84 4.3.2 Management target definition ....................................................................................................... 85 4.3.3 Pre-fishery abundance and catch allocation ................................................................................... 88 4.4 Overexploitation ................................................................................................................................. 89 4.5 Development in stock size................................................................................................................... 92 4.6 Stock-specific status evaluation .......................................................................................................... 93 4.6.1 Tana/Teno (total) ............................................................................................................................ 94 4.6.2 Tana/Teno main stem ..................................................................................................................... 97 4.6.3 Máskejohka ................................................................................................................................... 101 4.6.4 Buolbmátjohka/Pulmankijoki ....................................................................................................... 105 4.6.5 Lákšjohka ...................................................................................................................................... 109 4.6.6 Veahčajohka/Vetsijoki .................................................................................................................. 113 4.6.7 Ohcejohka/Utsjoki + tributaries .................................................................................................... 117 4.6.8 Váljohka ........................................................................................................................................ 121 4.6.9 Áhkojohka/Akujoki ........................................................................................................................ 125 4.6.10 Kárášjohka + tributaries............................................................................................................ 127 4.6.11 Iešjohka .................................................................................................................................... 131 4.6.12 Anárjohka/Inarijoki + tributaries .............................................................................................. 135 4.6.13 Summary and discussion of stock status and exploitation patterns ........................................ 139 4.7 The role of local/traditional knowledge in the current status evaluation ........................................ 144 4.7.1 The role of local/traditional knowledge within the scientific status assessment ......................... 144 4.7.2 Relative roles of the status assessment and the LEK/TEK in management decision-making ....... 144 4.7.3 Brief discussion of alternative explanatory factors ...................................................................... 145 5 Design and implementation of a stock-specific monitoring programme in Tana ...................................... 148 5.1 Background ......................................................................................................................................