David Cushing: Marine fisheries ecologist
Friday 11 April 2008
David Cushing was an outstanding contributor to marine science and a large character. He joined the Fisheries Laboratory (now the Centre for Environment, Fisheries and Aquaculture Science or Cefas) at Lowestoft in Suffolk after Second World War service in the Army. It was a time of change in cultures and technology that he embraced.
In 1974 he became Deputy Director leading the fisheries dynamics and management teams and retired from the laboratory in 1980. During this time, he was involved in many aspects of marine ecology and fisheries management, but he will be most remembered for advances in the understanding of how fisheries work as part of the ecosystem.
Fish stocks vary greatly naturally. The numbers of young North Sea haddock (the "recruitment", to fisheries scientists) can change by a factor of 10 from one year to the next. Cushing explained these dramatic changes in his "match-mismatch" theory, wherein the annual production of zooplankton food for the predatory fish larvae varies due to annual fluctuations in climate and weather. An ideal match of food and larvae results in a bumper harvest for the fishermen.
A natural extension was then to consider the implications of climatic shifts on fisheries production. We have good records of fisheries over the centuries, and we see stocks appearing and disappearing. David Cushing would have thrived on the current debates and uncertainties of the effects of anthropogenically induced climate change.
This was not, however, theory developed only at the desk. Cushing worked at sea and measured the dynamics of algal growth, nutrient depletion and zooplankton and fish larval numbers. In 1954 he lead 13 research cruises in the North Sea to study plankton dynamics in a moving body of water, stepping off one cruise on to another. He was particularly interested in examining the balances between nutrient regulation of algal production and zooplankton predation, and he produced some of the earliest marine ecological models.
The production of young fish cannot be a result of the environment alone. Underlying this great variability is a subtle trend of decreasing recruitment with decreasing numbers of adults. Cushing pursued with determination this problem of "stock and recruitment". Because of the variability, the trend in recruitment with parent stock size is difficult to detect, and some found difficult to believe. But Cushing insisted it was there, and introduced the concept of "recruitment over-fishing" as a companion theory to that of "growth over-fishing" which was developed by his colleagues at Lowestoft Ray Beverton and Sydney Holt. It is avoiding Cushing's recruitment over-fishing which ensures the sustainability of fish stocks.
David Cushing was much affected by the collapse of the North Sea herring in the 1970s. The herring collapsed from a parent stock size of over four million tonnes to 40,000 tonnes; a calamity for the herring and the vast industries involved with catching and processing it. Cushing led international working groups, for the International Council for Exploration of the Sea, to explain why. He initiated measures of stock abundance independent from industry statistics. In retrospect, and as he firmly believed at the time, this was a classic example of his "recruitment over-fishing". Fewer parents were producing ever fewer young.
David Cushing's work received world-wide recognition. Not only because of the importance of the work per se, but because he communicated those works to a wide audience with a string of readable books, such as his Marine Ecology and Fisheries (1975) and The Provident Sea (1988). Most notably, he was elected a Fellow of the Royal Society in 1977.
Cushing's contribution to science is not only his corpus of papers. He was a remarkable man, who had a great influence on many others. The problems he addressed were large and open-ended. He painted on a large canvas. David Cushing really was an ecologist who wanted to know how it all worked. Surely ecology is the most difficult of the sciences? And at sea even more of a challenge. From him others saw not only what was possible, but what was necessary to engage with problems of the scale found in the sea.
He continued working until 2001 as editor of the Journal of Plankton Research.
David Henry Cushing, marine ecologist and fisheries scientist: born Alnwick, Northumberland 14 March 1920; staff, Fisheries Laboratory 1946-80, Deputy Director, Fisheries Research 1974-80; FRS 1977; married 1943 Diana Antona-Traversi (one daughter); died Lowestoft, Suffolk 14 March 2008.
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