TORONTO -- A new study has found that the effects of climate change combined with overfishing pose an increasing threat to food security, particularly in poorer countries.

The international team of researchers published their findings Tuesday in the journal Current Biology, analyzing over 800 species of fish in 157 countries.

For billions around the world, fish offer an important source of micronutrients such as iron, zinc, vitamin A and omega 3. But fish are disappearing from parts of the world that rely on them to feed their population.

Some of this has to do with foreign fishing boats that sell their catches elsewhere, says Aaron MacNeil, professor of biology at Dalhousie University in Halifax and one of the co-authors of the study.

"European boats come and fish in, say, in West Africa and take [the fish] back to Europe," MacNeil told CTV National News.

But for tropical countries, climate change poses an even greater threat, with fish stocks fleeing overly warm waters, following food or seeking cooler climates. Researchers found that fish stocks in tropical regions, such as Southeast Asia and Sub-Saharan Africa, are far less resilient to climate change compared to fish in more northern climates.

"The issues of overfishing and the issue of climate change are not isolated. They are interconnected now, interconnected in many different ways," study co-author William Cheung, professor at the University of British Columbia's Institute for the Oceans and Fisheries, told CTV National News.

These tropical countries, which make up 40 per cent of all coastal countries, also happen to be where fish stocks are needed the most. Tropical fish tend to have a higher density of micronutrients. Yet, the populations in these countries also tend to have higher rates of inadequate nutrition.

"In the tropics, what we see is a diminishment of really key nutrients like zinc and iron, vitamin A, things that are really essential for human health," said MacNeil.

Researchers say there are nutrient-rich species that are more resilient to both climate change and overfishing, but are currently underrepresented in catches. Some countries may be able to adapt their fisheries to target these species. However, researchers point out that low-income countries would have a tougher time making such adaptations.

"The people who have contributed the least to climate change, again this tends to be low-income countries in the tropics, are the ones that are expected to see reductions of nutrient content of their fish into the future," MacNeil said.