A young British designer has won a prestigious international award for creating a "humane" net to make fishing more sustainable by preventing small fish from being trapped.

Dan Watson devised a system based on a series of escape rings for fish – which can be fitted to a fisherman's trawler net – in response to the problem of overfishing and the controversial and wasteful practice of throwing away healthy and edible fish or other creatures as so-called bycatch.

Watson, a graduate of The Royal College of Art, will on Thursday be named as the winner of the annual international James Dyson award which recognises and rewards imaginative design solutions to global problems.

The SafetyNet rings have been designed to exploit the escape behaviour and physiology of different fish. Small and medium fish swim up when stressed, whereas larger fish swim down. By exploiting this, the net only catches mature, non-endangered species and provides an illuminated "emergency exit" for the rest.

Sir James Dyson, the billionaire founder of the bagless vacuum cleaner and founder of the awards – run by the James Dyson Foundation – said: "This tangible technology approaches a serious environmental problem and we should celebrate it. SafetyNet shows how young graduates like Dan can tackle global issues ignored by established industries in new and inventive ways."

Since graduating, Watson has started a company, SafetyNet Technologies, to try to commercialise his technology.

Watson said he will be using his £10,000 prize money to further develop a broad range of prototypes and finalise government testing.