After a 40-year career in fisheries research at Lowestoft, Geoffrey Arnold, who has died peacefully aged 71, achieved his lifelong ambition to become a qualified driver of a steam locomotive.

He also led a major project to restore the St John Ambulance's Blyburgate Hall, Beccles, which was officially reopened by the Princess Royal in 2008.

Dr Arnold (pictured), who was head of fish stocks management at the Centre for Environment, Fisheries & Aquaculture Science (CEFAS), went to Epsom College and St Catherine's College, Oxford.

He joined the Ministry of Agriculture's fisheries laboratory at Lowestoft in 1963 and was awarded a PhD in marine biology from the University of East Anglia.

He was awarded a Churchill Fellowship in 1976 to study fish laboratories in the United States. His research covered fish behaviour and tidal movements, fish distribution, and a pioneering project to tag blue fin tuna, which provided valuable input to and from research laboratories in the USA, Europe and Japan.

After retiring in 2002, he remained an active researcher and was recently given the title of emeritus research fellow.

In 1997, he became chairman of the town's St John Ambulance's property committee. An outstanding chairman, he led the team that modernised the St John's main hall and raised £71,000 to complete the work. Without his leadership and perseverance, it would not have been achieved and the splendid hall is a fine memorial to his work for St John.

He was made a serving brother of the Order of St John in 2008 and was awarded the Beccles Rotary 2013 Presidential Cup for services to St John Ambulance.

From his youth, he was keen on bird watching and steam railways. In his early teenage years, he often cycled with friends round the bird reserves of East Anglia from his home in Surrey. Family holidays always seemed to be near a steam railway.

In retirement he spent many happy hours helping at the Bure Valley Railway, where he achieved his lifelong ambition to become a steam engine driver.

He is survived by his wife, Marion, whom he married in 1967, having first introduced himself on a badminton court by whacking her with a racquet. He is survived by Marion, daughters Sarah and Helen, and grandchildren Bronwen, Ioan and Aneirin. A funeral has taken place.