Parrotfish population declining 30% according to UOG


It looks as though Guam’s parrotfish population is declining by 30% over the past decade.

This was shown in a study conducted by UOG’s Sea Grant and Marine lab.

There are fewer Parrotfish in Guam’s waters according to a University of Guam Sea Grant-funded study conducted by researchers from the UOG Marine Laboratory.

During the study, researchers used video recordings in the same locations to survey Parrotfish numbers in 2012 and 2021.

According to Dr. Brett Taylor, the study’s lead author and  UOG Sea Grant researcher, Parrotfish are a staple in the island as they represent about 30% of the coastal fishery catch.

Dr. Taylor said that the past ten years in Guam have been really dynamic, so they conducted the study to see how this affected the Parrotfish population and their ecosystem.

“There’s been a lot of things that have been positive or negative towards the way things react on the reef and so we really wanted to have a check and double-check on this and see how our parrotfish is responding as a resource and as a component of the reef fauna,” says Dr. Taylor.

The study found that although overfishing plays a role it isn’t the only cause of the population decline.

“We’ve had successive bleaching events over the last 10 years and even when corals don’t bleach we have heat stress that affects the ecosystem,” Dr. Taylor continues.

“Most of the decline is actually in species that are not very strong fishery targets; they’re smaller whittier species, it’s what we call them, that are typically very resilient to human exploitation. So, what that tells us is that there’s a lot more going on than just overfishing over the last ten years and that’s why we believe there is certainly kind of a muddled impact of both fishing which is an easy thing to try and figure out what that does because you’re taking fish from an ecosystem, but also, there’s habitat decline, sedimentation, things that make it very hard to exist on a reef when it changes.”

According to the study, changes are likely caused by a “complex mix of exploitation, habitat change from multiple stressors, and responses to management measures.”

One of those management measures, which makes a positive impact on the situation, is Public Law 35-78 which was enacted in 2020 and prohibits fishing with a spear or other devices while SCUBA diving.

“There were many decades where there was a lot of debate whether SCUBA spearfishing should be outlawed, because we were one of the last places in the Indo-Pacific that still allowed it. So I do think that it was a very positive management measure, especially for Parrotfishes which are one of the top targets of that, so that should release pressure from Parrotfishes,” says Dr. Taylor.