Study finds fish are shrinking

ACCORDING to a new study by the CSIRO, fish around the world are shrinking in size.

Dr Asta Audzijonyte, from the CSIRO’s Marine and Atmospheric Research unit in Tasmania, says fish are getting smaller due to climate change and commercial fishing.

But she found that even small decreases in the body size of some fish species had a big impact on their population size, because it made fish more vulnerable to predators.

“So basically, if the flathead gets a bit smaller, it’s being eaten more heavily by other fishes like barracuda, which is the predator of the flathead,” Dr Audzijonyte told the ABC.

The CSIRO study looked at five Australian fish species: Tiger flathead, jackass morwong, silver warehou, blue grenadier and pink ling.

Dr Audzijonyte says fishing could be changing the long-term evolution of fish sizes.

“We usually selectively catch the largest and the fastest-growing individuals, leaving the small ones in the ocean. So we only have the small ones left … But then also, only the small ones get a chance to reproduce, and they are more likely to produce other small and slow-growing fish.

“So in this way, we are getting a long-term evolutionary decline in body size, which is more problematic because the fish will not get bigger quickly, even if we completely stop fishing, because they already became evolutionarily smaller.”

The scientists used a complex modelling system to test how the decreasing fish size affects the interactions between different species.

To listen to a podcast of the full story, click HERE.

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