Two Cape Town-based scientists have taken top honours in an international conservation award.

Dr Samantha Petersen, a biologist with conservation group WWF-South Africa, took first place in the 2008 UN Environment Programme/CMS Thesis Award on Migratory Species Conservation for her research into the impact of commercial fishing on migratory seabirds, sea turtles and sharks.

And Dr Ross Wanless, formerly of UCT's FitzPatrick Institute for African Ornithology who now works for Bird Life International's global species programme, took third for his research into the impact of the introduced house mouse on the seabirds of Gough Island.

Wanless made the astounding - and tragic - discovery that these so-called "super" mice were attacking and eating albatross chicks on the island, which is a World Heritage Site.

The two were separated only by Dr Lin Xia's thesis on traffic disturbance of the migration of Tibetan antelope in the extensive Hoh-xil national nature reserve.

There were submissions by 32 candidates from 18 countries for the award, which is sponsored annually by National Geographic Deutschland, Deutsche Lufthansa, Zoological Research Museum Koenig and CMS (Convention on Migratory Species).

The judges noted that Petersen's thesis on "Understanding and mitigating vulnerable bycatch in southern African trawl and longline fisheries" had made a significant contribution to improving the affected species' conservation status.

Petersen described the award as "very gratifying" and said the exposure would help drive further research and action to help save vulnerable species from extinction.

"Our work in this sphere is absolutely crucial now. In the last decade concern globally has grown over the impact of bycatch on these species, especially in longline and trawl fishing, which decimated their populations.

"It's estimated that 75 percent of global fish stocks are either exploited to their maximum or over-exploited and that around 25 percent of marine resources landed are dumped. This has led to a catastrophic decline in vulnerable marine life, including the loss of up to 90 percent of the large predatory fish."

Wanless described his third place as "fantastic".

"I'm really bowled over, and having seabirds so high on the agenda is amazing. I hope their high profile can continue."

Dr Morné du Plessis, chief executive of WWF-SA and a former director of the FitzPatrick Institute, said the awards were important.

"They demonstrate not only the scientific expertise in WWF and in South Africa's scientific community, but also highlight the growing concern over the impact of human activity on marine resources."