Ensuring Tradition Remains for Future Generations Through Fishing

Journalist Enqi Yang recently wrote a piece for the Guam Daily Post about how the CHamoru people have relied on fishing as a way of life for centuries, and it’s a practice that continues today. However, there’s a growing concern of a dwindling population of reef fish.

According to officials with the Guam Department of Agriculture’s Division of Aquatic and Wildlife Resources, the growth of commercial fisheries in the last 10 years has decreased the reef fish population.

Additionally, there have been environmental changes that harm reef fish habitats and hinder population growth, such as warmer climates causing coral bleaching, an increase in crown of thorn starfish that eat coral, soil erosion and other dangers.

Leilani Sablan, a CHamoru woman who grew up fishing and is now a biology graduate student at the University of Guam, has taken over 4,000 fish measurements of local catches for her master’s in Biology thesis.

“We have seen a significant decrease in the amount of large body fish in the last decade,” she said. “Many older CHamoru fishermen I’ve interviewed are catching less fish and smaller sizes compared to the fish they’d caught while they were younger.”

However, stopping the decline of reef fish should not mean regulating fishing for a taxonomy of fish, which some may argue would be an easier way of helping the fish repopulate. The taxonomy of fish is all of the species in that category. For example, a common taxonomy of an important food fish in Guam is the unicornfish. In that taxonomy are many different species such as hangon (orange-spine unicornfish) and tataga (blue-spine unicornfish).

Brent Tibbatts, fisheries biologist at DAWR, strongly disagrees with regulating fish based on their taxonomy, especially in a tropical reef environment.

“We have over 400 species caught in our creel database as fisheries,” he said. “To come up with individual regulations for 400 species is absolutely impossible.”


Guam’s Reef Creatures

Limiting fishing?

Research has shown that, for example, if parrotfish in general are experiencing a decline, limiting fishing for all species of parrotfish won’t help. That’s because fish in the same family will not all respond the same way.

“We’re now starting to understand more about how different species of fish in the same family compensate for the losses of individuals, a term referred to as compensatory density dependence,” or CDD, Sablan said.

Species with strong compensatory density dependence will increase in numbers when fishing pressure increases, but their sizes will decrease – that’s how they compensate for the losses of individuals in the population. There will be more of them, she said, but they will be smaller.

“Good examples of such fish are tataga (Naso unicornis) and the Pacific longnose parrotfish (Hipposcarus longiceps), which get fished heavily. But over time, instead of being completely wiped out, they increase in the numbers of them in the population, but just at a smaller size,” Sablan said.

The reason behind this is that when larger bodies of fish are removed, it gives room for juveniles and recruits to grow and mature, she said.

“However, fish such as the Steephead parrotfish (Chlorurus microrhinos) have weak compensatory density dependence. They do not compensate with increased fishing pressure, but just slowly disappear over time,” Sablan said.

“This shows that not all fish in the same family respond to fishing pressures the same – one species of parrotfish can handle strong fishing pressure, but the other parrotfish can’t. We shouldn’t go with the norm and say don’t catch parrotfish anymore,” Sablan said.

Furthermore, Brent Tibbatts said, “if we put a size limit on all parrotfish, then there will be a disproportionate harvesting of parrotfish because each species has a different maximum size.”

“Even more, many reef fish are sequential hermaphrodites, meaning they begin life as one gender and change to another as they mature. When you place a size limit you will be disproportionately harvesting the genders. It harms the reproductive ability of the population,” he said.

Fishing responsibly

However, even though compensatory density dependence and reef fish variability show that making reef fish regulations is challenging, responsible fishing should still be demanded, Tibbatts said.

“Although making reef fish regulation is very complex and time consuming, in order to ensure the future generation continues to have great fishing, we must responsibly harvest every species of fish now,” Tibbatts said.

Reef fish are a foundational part of Guam’s needs and should be a lasting part of Guam’s culture.

“There should be fish everywhere, and anywhere we go we should be catching fish,” Sablan said.

This entry was posted in Uncategorized. Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s