UH Hilo aquaculturist Chad Callan’s research has transformed commercial fish production for the aquarium trade
Chad Callan’s research has resulted in successful culturing of high-demand reef fish in the aquarium trade; the result is reduced strain on wild-caught populations and coral reefs. He’s also working with state agencies to restore nearshore fisheries and with community groups managing loko iʻa (traditional fishponds).
By Samantha Dane/UH Hilo Stories.
This story on Chatham Callan’s research profile was first published on the website Keaohou that features UH Hilo faculty research and scholarly activity.
An aquaculturist at the University of Hawaiʻi at Hilo hopes his research into new rearing methods for Hawaiian reef fish will continue to have positive impacts on the aquarium trade and local fishing industries while also protecting marine resources.
Chatham “Chad” Callan, an associate professor of aquaculture whose research is based at UH Hilo’s Pacific Aquaculture and Coastal Resource Center at the edge of Hilo Bay, is developing sustainable rearing methods for coral reef fishes not commercially available in the aquaculture trade.
Usually, these fish are taken from the wild, but developing commercially viable methods of raising fish lessens the strain on wild-caught fish populations and the coral reefs they support. Many of these fish have not been studied in an aquaculturing context before, so little is known on how to properly rear them in a lab or commercial context.
“I hope to rectify this through research and improve commercial fish production for the aquarium trade,” says Callan, whose work has already produced a successful feeding protocol for yellow tang, one of the most popular marine aquarium fish. The new protocol “has since transformed how marine ornamental aquaculture is being done for other species,” he says.
- See Development of Improved Feeding Methods in the Culture of Yellow Tang, Zebrasoma flavescens (Jan. 22, 2018, Journal of the World Aquaculture Society).
“My lab was the first to culture this species after nearly 20 years of (research and development) trying to make it happen,” he says. “This work paved the way for the culture of other similar reef species that are of high importance to the aquarium trade. Culture of these fish species helps reduce fishing pressure on coral reefs.”
Hawaiian cleaner wrasse
In a current project on aquarium fish, Chatham and his research team have uncovered a previously unknown stage in the life cycle of the Hawaiian cleaner wrasse, another popular marine aquarium fish.
“In my current research with Hawaiian cleaner wrasse, we learned that this fish goes into a semi hibernation type state during its metamorphosis to juvenile form,” explains Callan. “During this time, they basically make a little mucous cocoon and nearly vanish from the rearing tanks. We had previously assumed they had all perished during this phase, but recently were very surprised to see nearly 60 emerge from this state and fill the tank once again. This marked another first for this species, as after we raised this batch they were made commercially available for the first time as a cultured alternative to wild fish.”
This Hawaiian cleaner wrasse research is ongoing at UH Hilo’s aquaculture center, where Callan has been conducting research for several years before coming on board as UH Hilo faculty in 2023. His research team has been culturing endemic Hawaiian species, such as potters angelfish and Hawaiian cleaner wrasse, among others, since 2015, and recently made the significant headway with the cleaner wrasse.
“We plan to keep working with this species, and hope to continue improving methods for their rearing so that commercial offerings will become more frequent,” says Callan in a social media post. The work includes caring for broodstock, producing live feeds, and caring for the delicate larvae; “this work is a labor of dedication,” he says of his research team.
He’s also currently working on developing culture methods for other coral reef fish species that have not been commercially produced yet.
Marine stock restoration
Callan is also working with state agencies to restore nearshore fisheries. Previous stock restorations programs for moi and mullet in the late 1990s to early 2000s showed promising results building up local fisheries but were ended due to a lack of funding.
“A major goal within the next decade is partnering with the state to get the moi and mullet programs back up and running again,” says Callan. “Our work aims to help reduce impacts on coral reef environments and help restore nearshore fisheries with species that have been experiencing declines over the past several decades.”
Another research goal is working together with community leaders managing loko iʻa (traditional fishponds) to restock the ponds and find ways to produce fish depending on the condition of the fishpond. Fish such as mullet, moi, āholehole, and milkfish are all species of interest for Callan and the fishpond managers across the state who wish to restore these culturally significant areas to the point where the fish can once again be grown and harvested.
“I’d really love to see a successful stock restoration program for moi and mullet be re-started again,” he says.
In relation to this work, Callan and a research team have investigated loko iʻa and the impacts of climate change. This study assesses how climate change may affect loko iʻa productivity, as well as how nutrient flow restoration and restocking may mitigate some of these effects.
- See Restoration and management of an Indigenous aquaculture system helps mitigate climate change impacts to estuarine fisheries. (2025, npj Ocean Sustainability)
“We found that although rising water temperature may lead to declines in fish density, loko iʻa fish populations were more resilient to rising water temperatures than those in the surrounding estuary,” write the collaborative authors of the study. “Notably, the combined benefits of fisheries effort regulations, nutrient flow restoration, and restocking were found to offset some of the potentially negative effects of warming on fish populations and substantially increase short- and long-term estuarine and loko iʻa fish density. However, long-term population trends were still primarily dictated by emissions scenarios and their associated temperature projections. In the face of rising water temperatures, biocultural restoration may be especially important for enhancing fish populations and increasing social-ecological resilience.”
Teaching and workforce development
Along with two aquaculture classes Callan currently teaches as a primary instructor, students work directly with him at the aquaculture center, where much of his research takes place.
“Students work with us directly here at the Pacific Aquaculture and Coastal Resource Center, assisting with fish care, feeding, recording data, cleaning tanks, et cetera,” he says. “They get great hands-on experience that makes them much more marketable post graduation. I also help mentor undergraduate students on their capstone projects as well as supervise graduate students.”
Undergraduates are encouraged to do independent research projects for thesis or capstone work and use the aquaculture facility to develop various research and fish rearing skills. The center also employs students to help around the facility caring and feeding fish, cleaning tanks, and recording data, all invaluable hands-on experience for those hoping to get into the field.
Callan says there are an increasing number of aquaculture-related positions around the islands as the industry continues to grow and diversify.
“As the fastest growing food production sector in the world, aquaculture stands on the forefront of future food production, especially here in Hawaiʻi,” he says.
Alongside graduate students and doctoral candidates doing research at the aquaculture center, the facilities also host elementary and high school student groups. This gives Callan the chance to teach visiting students about the work being done at the center, an essential part of the scientific outreach portion of his research.
About
Callan received his master of science in marine biology (2000) and a doctor of philosophy in marine biology (2007) both from the University of Maine. He arrived at UH Hilo as an associate professor of aquaculture in 2023 after teaching at Hawaiʻi Pacific University on Oʻahu for over 15 years.
At HPU, he also conducted research and later served as program director at the Oceanic Institute’s Finfish Program where he managed all aspects of the program, from administrative work to trial development and research.
In addition to his position at UH Hilo he is currently serving as cooperating graduate faculty at UH Mānoa’s marine biology graduate program.
Story by Samantha Dane, a biology major at UH Hilo.
