Dr Derek Mills, who died aged 90 on the 29th of January, made great contributions to the understanding of the fishes of the Tweed and their environment from his position as a Senior Lecturer in the then Dept. of Forestry and Natural Resources of the University of Edinburgh, both through his own work and that of his students.
He was a regular contributor of papers to the Annual Reports of the River Tweed Commissioners in the 1970s, covering a wide range of topics of interest and concern. In the Annual Report of 1970, he wrote a preliminary account of the fish populations of some Tweed tributaries; in the 1971 Report he reported on the population density and growth of young salmon in those tributaries and in the 1972, along with some of his students, on the trout. In the 1973 Report, his contribution was on the movements and contribution to angling of stocked trout; in the 1974 it was on the changes in weight distribution of Autumn salmon on the Tweed. The 1978 carried a summary of a major survey he and his students had made of the freshwater fishes of the catchment. In 1979 a student of his reported on his work on the diet of Cormorants on the lower river and in 1980 Dr. Mills wrote more generally on Scottish salmon rivers and their future management. In 1981 he gave an account of an expedition he had been on to study salmon on their feeding grounds around Greenland.
The theses, Honours, Masters and Doctoral, produced by his students are an absolutely invaluable store of information on the fishes of the Tweed in the 1970s and 1980s, some species of which have undergone major declines since, such as the Eel, studied in great depth in four Tweed tributaries in the early 1980s (Hussein) and the Dace (Starkie, 1976). Dr Mills was an early and concerned observer of the effects of old-style dense, coniferous afforestation on fish in burns which they shaded and the work of his Masters student Barbara Smith (1976) on the Cardrona Kirkburn was a milestone in changing forestry practice to mitigate its effects on fish. These sorts of studies not only produced information valuable for their own times, but created baselines against which any changes can be identified and measured: a fly-life survey of the early 1970s (B. Smith, 1974) has been repeated by The Tweed Foundation in recent years and shown how species previously found in the lower reaches have spread upstream, probably due to warmer conditions. Another study of the early 1970s, again on the Cardrona Kirkburn (S. Campbell), which trapped Sea-trout and Brown-trout running up to spawn has also been repeated by The Tweed Foundation to find that numbers of female Sea-trout were the same almost 40 years on, but that the smaller, male, Brown-trout had become younger for their size. To have this sort of long-term background is a huge advantage for fisheries work on the Tweed as it gives the sort of perspective that is essential for any firm understanding of present day situations.
The Honours theses he set up and supervised covered a very wide range of topics: Mayfly, Stonefly and Caddis in the Tweed; the diet of Eels; spawning behaviour and larval development of Grayling; the food of Grayling; the determination of the age and growth of Roach from scales and Opercular bones; the growth and food of Stone Loach (Beardies); the distribution, food and growth of Minnows (Baggies); the insect populations of Fruid and Talla reservoirs compared to St. Mary’s Loch; the age and growth of Gudgeon; the Flounder of the Tweed; connections between land-use and the growth of Trout; the population dynamics of Tweed salmon and the effects of fisheries; the parasites of the Eels of the Tweed; the factors controlling the survival of Sea-trout; land use changes in the in the catchment of the Whiteadder as shown by aerial surveys; the overall effect of the area of coniferous afforestation on aquatic animals; the seasonal distribution of Sea-trout; the spawning of Sea-trout in eight Tweed tributaries; the parasites of Tweed trout and the use of spot patterns to identify individual Grayling.
The catchment surveys Dr. Mills organised, of the fish fauna of the Tweed Basin (Mills, Griffiths and Parfitt, 1978) and of the Salmon and Trout stocks of the Tweed (Mills and Tomison, 1985) gave the bases on which the present regular surveys of the Tweed were set up in the 1990s and some of the electro-fishing sites he first surveyed are still being sampled. His final major contribution to the Tweed was to edit the proceedings of the “Tweed Towards 2000” Symposium in 1989.
Derek was a Trustee of The Tweed Foundation from when it was first set up in 1983 to 2002 and a member of its Technical Advisory Group, and continued to give great and much valued support and advice after retiring from formal participation in its work.