The Girnock and Baddoch traps are long term monitoring sites focussed on salmonids and operating since 1966 and 1988 respectively. During some years these have also operated as downstream eel traps, resulting in years with complete, partial or absent annual count data as follows. Girnock: complete data 1966-1981, 2003-2009, 2011-2022; partial data 1982-1984, 1986, 1989, 2002, 2010; data absent 1985, 1987, 1988, 1990-2001. Baddoch: complete data 2006-2020; partial or possibly partial data 2003-2005, 2021. Small eels may evade capture by slipping through trap bars. Adult silver eels are too large to evade capture in this way, but some eels, both large and small, may bypass the traps in spates: thus annual counts represent minimum numbers. Trap protocols were similar, although not identical, over the monitoring period. Lifestage has not always been recorded, and where absent the following site-dependent criteria have been applied to determine lifestage: Baddoch, ‘silver’ if length > 279 mm in length and caught May-December inclusive, otherwise ‘yellow’; Girnock, ‘silver’ if > 279 mm in length and caught June-December inclusive, otherwise ‘yellow’.

Upstream eel movement data has been collected (May-September inclusive) and digitally stored at the Girnock since 2013, with data absent in 2016 and a new trap operating from 2017. These represent partial counts only, as an unknown proportion of eel bypass the trap.