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Where do they go? Dr. Nancy Foster Scholar Richard Coleman tracks fish populations in Papahānaumokuākea

By Yaamini Venkataraman

August 2018

Many Native Hawaiian fishers will tell you the same thing: there are not plenty of fish in the sea. In their childhood, they would throw nets into the ocean and catch numerous large fish. Today, when they bring their children to their traditional fishing grounds, their nets often come up empty. Where did the fish go?

convict tangs swimming
Convict tang (manini) swim at Midway Atoll in Papahānaumokuākea Marine National Monument in the Northwestern Hawaiian Islands. Photo: John Burns/NOAA

Dr. Nancy Foster Scholar Richard Coleman is working with native fishing communities to understand what has happened to Hawaiian fisheries. For his Ph.D. at the Hawaiʻi Institute of Marine Biology at the University of Hawaiʻi, Coleman is studying fish dispersal throughout Hawai‘i. He wants to figure out if the Northwestern Hawaiian Islands may provide a place for fish to grow up so they can later travel back to the Main Hawaiian Islands.

richard coleman
Dr. Nancy Foster Scholar Richard Coleman tracks fish populations in Papahānaumokuākea Marine National Monument. Photo courtesy of Richard Coleman

The Northwestern Hawaiian Islands are a wide expanse of uninhabited atolls and small islands stretching across 1,350 miles of open ocean. The islands, and the waters surrounding them, are protected by Papahānaumokuākea Marine National Monument, the largest protected area in the United States.

Papahānaumokuākea is not open to commercial fishing; however, limited fishing for research and consumption within the monument are strictly permitted. Fishing for consumption may be permitted under Native Hawaiian Practices permits, which allow for traditional and customary cultural practices. As a commercial no-take zone, the monument protects important fish species, and has been thought to have the potential to repopulate some fisheries in the main Hawaiian Islands — something several fishers are interested in.

“We were approached by a Native Hawaiian community leader who wants connectivity and dispersal information [for fish] targeted heavily by recreational fishing,” Coleman says. “This group wants to make a community-based management effort.” In particular, they want to know if fish populations in the monument could act as a source population for fish in the main Hawaiian Islands.

Before he can determine whether Papahānaumokuākea Marine National Monument is a source for fish populations in the main Hawaiian Islands, Coleman needs to figure out what population units exist in the Hawaiian archipelago. Fish spawn, or release eggs and sperm, into the open ocean. If fertilized, the egg develops into a baby fish, called a larva. The larvae themselves are at the whim of the ocean currents, hitching a ride and traveling far away from their spawning grounds. Larvae then need certain conditions to grow into juvenile fish that can swim on their own.

Coleman’s job is to figure out just how far these larval fish travel and where they end up. He examines dispersal and connectivity patterns for two Hawaiian fish: goldenring surgeonfish (kole) and convict tang (manini).

coleman diving near a coral and rock ledge
Coleman dives in Papahānaumokuākea Marine National Monument. Photo: Brian Hauk/NOAA

Fishing is important for Native Hawaiian culture and identity. There has been a strong movement for Native Hawaiians to access the same resources as their ancestors to cultivate their relationship with their ancestral places, reclaim their identity, and support overall health and well-being within their communities. Community-based resource management is not a new concept for Native Hawaiians. Several communities that practice subsistence fishing define their own regulations based on traditional practices, according to Kalani Quiocho, the Native Hawaiian program specialist at Papahānaumokuākea Marine National Monument. In fact, the word for fisher, lawaiʻa, roughly translates to “fish abundance” or “one who has sufficient knowledge about fish,” which alludes to the role that fishers have had, and continue to have, in responsibly managing natural resources.

Coleman analyzes the genetic makeup of adult fish to track them back to their original spawning grounds. When he was introduced to genetic methods as an undergraduate student participating in an NSF Research Experience for Undergraduates program, he was initially intimidated. They can be complicated to understand, and often require lots of time and energy both preparing samples in a laboratory and analyzing data on a computer. But after he saw how powerful genetic tools are — how many complicated questions he could start to answer with them — he was “hooked.”

To understand how fish are dispersed across the Hawaiian archipelago, Coleman first collects fish samples from several different locations. He then sequences all of their genetic information, or genome. Looking at the entirety of a fish’s genetic background, he can compare genomes between individual fish. The more similar these fish genomes, the more likely the fish are from the same population. Using these techniques, Coleman can identify fish that have traveled far away from their parents’ spawning ground, and those that remained in the same place.

coleman diving
Coleman’s goal is to figure out if fish populations in Papahānaumokuākea Marine National Monument disperse as larvae into the main Hawaiian Islands. Photo: T.E. Roberts/Tethys Images

Coleman expected that fish larvae dispersal would at least provide some connection between the main Hawaiian island populations and monument. Looking at kole, that is not what he found.

“Each island is its own independent unit,” Coleman says. “If the populations are overfished in any of the islands, it is going to take a long time to be repopulated by any of the neighbor islands.”

His findings also demonstrate the importance of the protective boundaries around Papahānaumokuākea Marine National Monument. Not only is the monument not a source population for the islands, but it also is not a sink for fish – that is, fish larvae do not tend to travel from the main Hawaiian Islands into the monument. According to Coleman, if the monument is overfished, it cannot be repopulated by populations from the main Hawaiian Islands.

Working with Native Hawaiian fishing communities, Coleman seeks to answer questions important for sustaining their culture. He sees a disconnection in the ways some scientists pursue research in the ivory tower.

“Scientists just speak to other scientists, and our message doesn’t really relate to the community,” Coleman says. By connecting genetics with traditional fishing practices and discussing these issues with Native Hawaiians, Coleman is bridging the divide between scientists and the communities’ needs.

Yaamini Venkataraman is a volunteer social media intern for NOAA’s Office of National Marine Sanctuaries and a graduate student at the University of Washington.