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To save Hawaiian fisheries, scientists look to locals for answers

© Troy K Shinn/

Editor’s note: The world’s fisheries are in decline just as demand for seafood is rising. To restore and protect the overtaxed fisheries that 3 billion people depend on for their main source of protein, two new research papers propose that the scientific community must turn to the traditional knowledge and observation skills of local fishers.

As the science adviser for Conservation International (CI) Hawai‘i, Eva Schemmel, lead author of the two studies, noticed that the state of Hawai‘i lacked the fish reproduction data necessary to effectively manage local fish populations sustainably. When she started visiting communities, however, she found well-informed people ready to get to work. We sat down with Schemmel to discuss her findings.


In many coastal Hawaiian towns, small-scale fishers have a more thorough knowledge of the health of local fish populations than scientists do. (© Troy K Shinn/

Question: How can communities help the state of Hawai‘i make its fisheries more sustainable?

Answer: In creating effective rules and regulations for maintaining small-scale or “coastal community” fisheries, there are two commonly used practices worldwide: setting size limits for catch, and closing down areas of the fishery during spawning. It’s important to allow fish to spawn at least once so they can replace themselves. But catch size limits should also be capped on the upper end: Bigger fish spawn more and have [healthier] offspring, so protecting them can have a big impact on overall fish numbers. Fishing for species while they are aggregating and spawning, which happens at certain locations and times of the year depending on the species, can quickly deplete fish populations, which is why closed seasons are important.

In Hawai‘i, we have more than 50 types of reef fish that are commonly harvested, yet the state and scientific community have biological and reproductive information for only about 10 percent of them. But when I started going into local communities and working with fishers, I realized that a lot of that information was already part of traditional ecological knowledge. For example, Hawaiian fishing practices have long included rotating fishing grounds and closed seasons for particular fish species, as well as extensive knowledge on fish behaviors and spawning times. However, over time this information is being lost.

Communities have been learning about their home for hundreds to thousands of years. As scientists, we’re still catching up. Additionally, while data collected through scientific monitoring is increasingly relied upon to make environmental management decisions, local and traditional knowledge rarely carries the same weight in policy discussions. This needs to change. I saw a chance to bridge the knowledge gap by developing monitoring methods that would couple traditional knowledge and science to gather the information needed to manage community fisheries.

Q: What did comparing fish populations in Hawai’i teach you about how traditional knowledge can play a role in fisheries management?

A: To highlight the importance of traditional ecological knowledge and local stewardship, I wanted to document what communities already were well aware of: fish do different things in different places — which means when it comes to state policy, it’s not one size fits all.

For my first paper on this, I worked with communities and fishers to get samples of one commonly harvested fish, known locally as manini, in four locations across the main Hawaiian Islands each month for two years. Currently the state has a minimum-size limit for this species; I wanted to see how variable its size, maturity and spawning times were across those four locations to see if the “one size fits all” management is effective.

From that study, we found that size and maturity varies by more than 20 percent of the fish’s total body length. So even though it’s a small fish, that’s over an inch of variability in size and maturity — which can mean catching a fish before it is able to spawn at least once and replace itself. It also means that one size limit is likely ineffective across the islands. We also found that larger manini (about 22 centimeters, or almost 9 inches) produce up to 24 times as many eggs as 14-centimeter (5.5-inch) manini. This even further highlights the importance of fish size and setting appropriate harvest size constraints, leaving the small and large fish.

Because fish populations are clearly doing different things in different locations, incorporating traditional ecological knowledge and local monitoring is essential. Ultimately, the state does not have the capacity to manage at the community scale across the entire state, so to understand and set effective fishing practices for each area we recommend the participation of local fishers and communities. We as scientists and managers have much to learn from these communities and should look for ways to support these efforts.

ci_16752584Young Hawaiians learn about sustainable fishing practices at a CI-organized event. (© Conservation International/photo by S. Kēhaunani Springer)

Q: So that led to your “aha” moment — or paper two?

A: Right: Working with these communities, I found myself thinking, “Why do we even need scientists in this practice?” The communities understand what’s happening, and we — the scientists — are still catching up. In other words, to support communities I wanted to make fishery monitoring something that any fisher or community member could do without outside support.

I looked back at all the community-gathered data collected for the first paper. Everyone had been trained to measure the manini the same way; we did gonad weight measurements and compared them to more complicated laboratory assessments. We found that the lab work and the community assessments were essentially producing the same results when it came to determining spawning timing and size at maturity. What this tells us is that we don’t need to do the complicated science: Communities can use simple scales and tools to understand spawning patterns, size and maturity. Therefore, we don’t have to wait for the lag of scientific analysis or spend a lot of money — we can effectively manage our fisheries by enabling fishers to monitor and manage themselves.

To integrate this scientific monitoring with traditional practices, we worked with communities to incorporate data on spawning times and target fish sizes into local moon and fishing calendars. Hawaiians use the different moon phases to understand what’s happening in the ocean and on land, and linking the monitoring information to lunar cycles helps communities share their results with each other. This way, all fishers in a particular area will understand the local conditions — such as when a fish is spawning — and how to best respond.

Q: What exactly is at stake for Hawai‘i when it comes to improving management of coastal community fisheries?

A: In today’s age, there are so many competing and diverse uses of our resources. We must take a proactive approach to management.

In the Pacific Islands, our reef fisheries feed us. And as our marine resources get more and more depleted, whether from development or agricultural runoff or population growth, a lot of people are forced to collect smaller and smaller fish and at the wrong times. Conducting scientific monitoring in tandem with efforts to raise awareness about traditional practices can enable us to rebuild our fish populations. Fish are pretty resilient. They want to reproduce. And if you allow them to do that, our populations can recover.

The ocean is a way of life for people here. That’s why I think people have been so receptive to our work, because we’re not saying, “Don’t catch that fish.” We’re saying, “Understand what your impact is, and let’s all lessen it. Maybe it’s not the time to catch that fish, but there are 50 other fish out there for you to catch.”

Eva Schemmel is the science adviser for CI Hawai‘i. Sophie Bertazzo is a staff writer for CI.

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