News

Team October 5, 2026

Leon Tran successfully defends Ph.D. dissertation — awarded 2026 Smith Conservation Research Fellowship

Huge congratulations to Dr. Leon Tran, who successfully defended his Ph.D. dissertation on the thermal tolerance of coral reef fishes and octopus! Leon's research quantified seasonal thermal sensitivity, upper thermal tolerance limits, and thermal safety margins in species including manini and the day octopus (heʻe mauli), and built thermal habitat suitability models to forecast how reef communities will shift as oceans warm. Leon was awarded both the prestigious 2026 David H. Smith Conservation Research Fellowship and a NOAA NMFS–Sea Grant Fellowship — and chose to accept the Smith Fellowship for his postdoctoral research. We are incredibly proud of Leon and can't wait to see what he does next!

Outreach August 6, 2026

Fish Resilience Program represented at ICBF (Vancouver) and ICRS (Auckland)

The Johansen Fish Resilience Program was proudly represented at this year’s International Congress on the Biology of Fish (ICBF) in Vancouver, Canada, and also at the International Coral Reef Symposium (ICRS) in Auckland, New Zealand, by Linda, Jasmine, Leon, and ʻAʻaliʻi. Lots of interest, questions, and exciting connections forged with new and existing colleagues!

Team August 5, 2026

Linda Eggertsen awarded prestigious startup grant as Assistant Professor at Universidade de São Paulo

Huge congratulations to postdoc Dr. Linda Eggertsen, who has been awarded a highly prestigious startup grant as an incoming Assistant Professor at Universidade de São Paulo, Brazil! While Linda will be sorely missed in the lab, we are so, so proud of her and look forward to many years of cool collaborative work together.

Team August 4, 2026

Christopher Suchocki joins the lab as Graduate Researcher

Welcome to Christopher Suchocki, who joins the Johansen Fish Resilience Program as a Graduate Researcher! Christopher is broadly interested in aquatic ecology, ecosystem function dynamics, and habitat restoration, and is focused on 3D modelling cryptic coral reef habitats to better understand fish and invertebrate recruitment, with the goal of designing ecological improvements for near-shore infrastructure.

Meet the team

Software May 16, 2026

Temp-Pref Tracker v.2.5 released

Temp-Pref Tracker v.2.5 is now available on the Fish Resilience Program website. This update adds optional internal core/body temperature estimation based on specimen mass and chamber temperature, updates the installer package, and includes the revised v.2.5 user manual for download.

Learn more & download

Software May 14, 2026

CTmax Tracker v1.2 released

CTmax Tracker v1.2 is now available through the Fish Resilience Program website. The software was developed for Critical Thermal Maximum experiments in fish and other aquatic ectotherms. The software combines interactive specimen tracking, live DAQ-linked temperature monitoring, ramp control, CTmax event logging with internal temperature estimation, and CSV export in a single Windows desktop application.

Learn more & download

Outreach April 9, 2026

ʻAʻaliʻi Kelling’s imu research featured in Hawaiian Airlines Hana Hou! Magazine

Congratulations to ʻAʻaliʻi Kelling, whose research on imu (traditional Hawaiian fish houses) has been showcased in Hana Hou!, the in-flight magazine of Hawaiian Airlines. The feature highlights ʻAʻaliʻi’s work exploring how these culturally significant structures influence juvenile fish behavior and habitat use — a wonderful example of integrating Native Hawaiian traditional knowledge with modern marine science.

Read the article (PDF)

Team April 9, 2026

Jasmine Reighard recognized among top cited authors in Reviews in Aquaculture

PhD candidate Jasmine Reighard has been recognized among the top 10 most cited authors for the journal Reviews in Aquaculture among 2024 publications. Her article “Salinity tolerance of fishes: Experimental approaches and implications for aquaculture production” was recognized as a top cited article by Wiley. Amazing accomplishment!

Outreach April 2, 2026

Voice of the Sea documentary features Fish Resilience Program

The lab’s coral reef fish research is featured in a full documentary episode on Voice of the Sea, a PBS Hawaiʻi television series produced by Hawaiʻi Sea Grant. The episode, “Clean Water, More Fish, Healthy Reef” (Season 13, Episode 2), explores our work in Kāneʻohe Bay and how ʻāina stewards are restoring streams and reefs.

▶ Watch on YouTube More outreach →

Team March 31, 2026

Leon Tran selected for nationally competitive fisheries fellowship

Johansen Lab student and Hawaiʻi Sea Grant Fellow Leon Tran has been selected for a nationally competitive fisheries fellowship. Leon’s research integrates species distribution modeling with experimental physiology to predict how coral reef fish distributions will shift under environmental change.

Read article (UH News)

Outreach March 27, 2026

Civil Beat covers herbivore & coral reef research

Honolulu Civil Beat published a feature on the lab’s work showing how herbivorous reef fish help protect coral reefs — and what happens when sediment runoff undermines their ability to do so.

More outreach →

Team December 15, 2025

ʻAʻaliʻi Kelling defends M.S. thesis & returns as Ph.D. student

Congratulations to ʻAʻaliʻi Kelling for successfully defending his M.S. thesis on the influence of Native Hawaiian imu (fish houses) on juvenile fish behavior! ʻAʻaliʻi has immediately rejoined the Johansen Lab as a Ph.D. student, where he will continue his research on fish-habitat interactions and cultural resource management.

Meet the team

Publication March 2025

New paper in Global Change Biology: Aerobic performance of coral reef fishes facing extreme thermal variability

Vaughan GO, Ripley DM, Mitchell MD, McParland D, Johansen JL, Shiels HA, Burt JA (2025) Narrow Margins: Aerobic Performance and Temperature Tolerance of Coral Reef Fishes Facing Extreme Thermal Variability. Global Change Biology, 31(3), p.e70100.

View all publications

Publication 2025

New paper in Science of the Total Environment: Piscivores and warming oceans

Brijs J, *Moore C, *Schakmann M, *Souza T, *Grellman K, *Tran LL, *Patton PT, Johansen JL (2025) Eat more, often: The capacity of piscivores to meet increased energy demands in warming oceans. Science of The Total Environment, 973, p.179105.

View all publications

Publication January 2025

New paper in PLoS One: Herbivore resilience to marine heatwaves

*Souza T, Brijs J, *Tran L, Crowder L, Johansen JL (2025) Herbivore functions in the hot-seat: Resilience of Acanthurus triostegus to marine heatwaves. PLoS One, 20(1), p.e0318410.

View all publications

Publication 2025

New paper in Journal of Experimental Biology: Social environment and swim speed

*Tiddy IC, *Neill CM, *Rosén A, *Hasegawa Y, Domenici P, Johansen JL, Steffensen JF (2025) Effects of social environment and energy efficiency on preferred swim speed in a marine generalist fish, pile perch (Phanerodon vacca). J Exp Biol, 228(5).

View all publications

Outreach August 6, 2025

Johansen Lab at the Indo-Pacific Fish Conference in Taiwan

This June, several Johansen Lab researchers and collaborators traveled to Taipei, Taiwan, for the 2025 Joint Conference of the Asian Society of Ichthyologists Annual Meeting and the 12th Indo-Pacific Fish Conference. Jake Snyder presented the first chapter of his PhD thesis on modeling coral reef and herbivorous fish outcomes, while Jasmine Reighard presented her research quantifying the metabolic costs of sediment exposure using 3D-printed respirometry chambers. Lisa McManus also participated.

Research June 13, 2025

Mud-to-Makai in Guam

In April, PI Jacob Johansen and postdoc Linda Eggertsen visited Prof Brett Taylor at the Marine Lab at University of Guam. Profs Howard Choat and Andy Hoey (JCU) also joined the trip. We had a productive week at the Marine Lab working on samples collected in Hawaii as part of the “Mud to Makai” project, studying effects of land-based sediment runoff on herbivorous fishes. Prof Choat also visited us at HIMB on the way back to Australia. A huge thank you to Brett for having us!

Team July 26, 2024

Congratulations to Katherine Grellman — first student to graduate from the Johansen Lab!

Congrats to Kat for becoming the first student to graduate from the Johansen Lab following the successful defense of her master’s thesis! We wish her well in her future endeavors and hope to see her often. What better way to celebrate than a nice climb outdoors with food, drinks, and friends!

Team July 18, 2024

Come see Katherine Grellman’s M.S. thesis defense!

Katherine defended her M.S. thesis on the effects of enhanced sediment-laden algal turfs on herbivorous fish interactions. She was the first student to complete their degree in the Johansen Lab.

Publication July 11, 2024

Why are fish shrinking as the oceans warm?

Find out in the Johansen Lab’s publication, “Impacts of ocean warming on fish size reductions on the world’s hottest coral reefs”, published in Nature Communications. The news release hit nearly all the main dailies in the UAE including The National, Gulf News, Al Etihad, and Al Khaleej. This research scored in the top 5% of all research outputs by Altmetric.

Read paper (Nature Communications)

Outreach July 5, 2024

Johansen Lab takes on Europe!

Leon Tran and Jasmine Reighard traveled to Prague, Czech Republic, to present their preliminary results at the Society of Experimental Biology. Jasmine presented her poster on “Metabolic responses to suspended sediment in a Hawaiian herbivorous reef fish”, while Leon presented his on “Body size variation and sensitivity to marine heatwaves in the day octopus (Octopus cyanea)”. Leon received the Best Early Career Research Award for his poster session, sponsored by Functional Ecology. Meanwhile, Jacob Johansen, Jake Snyder, and Mathias Sorensen traveled to Naples, Italy, where Mathias presented his preliminary results at the European Coral Reef Symposium.

Team June 12, 2024

Congrats to Katherine Grellman on starting her career!

Katherine was recently hired by The Nature Conservancy as their Coastal Science Specialist. In her new role, she will support water quality strategies to prevent land-based pollutants from impacting marine ecosystems across the Hawaiian islands. Way to utilize your graduate experience!

The Nature Conservancy Hawaiʻi

Publication 2024

New paper in Frontiers in Fish Science: Hypoxia and swimming in pile perch

*Frank LC, *Prescott LA, *Scott ME, Domenici P, Johansen JL, Steffensen JF (2024) The effect of progressive hypoxia on swimming mode and oxygen consumption in the pile perch, Phanerodon vacca. Frontiers in Fish Science, 2, 1289848.

View all publications

Team 2024

Shane Ribovich joins as Lab Manager

Shane Ribovich has joined the Fish Resilience Program as Lab Manager, overseeing day-to-day operations of the Johansen Lab at HIMB including the experimental seawater systems and field equipment.

Meet the team

Outreach 2024

RECOVER Virtual Lab brings fish physiology to classrooms

The RECOVER Virtual Lab — an interactive online tool developed with the lab’s research — now lets K–12 and college students explore how oil spills affect fish swimming performance. Freely available as a STEM education resource.

Try it out

Outreach March 18, 2024

Spring break in Kauaʻi — Imu Workshop

ʻAʻaliʻi Kelling, Jasmine Reighard, and Leon Tran traveled to Kauaʻi during spring break to lead an educational workshop for high school students about the traditional Hawaiian practices of Imu (Fish Houses).

Publication September 2023

New paper in Global Change Biology: Seasonal resilience to heatwaves and hypoxia

*Tran LL, Johansen JL (2023) Seasonal variability in resilience of a coral reef fish to marine heatwaves and hypoxia. Global Change Biology, 29(9), 2522–2535.

View all publications

Team August 1, 2023

Dr. Linda Eggertsen joins the lab as Postdoctoral Researcher

We are happy to welcome our newest member of the team, Dr. Linda Eggertsen. Linda is an extremely skilled field biologist and we look forward to her work on fish herbivory across terrigenous runoff gradients.

Meet the team

Team November 30, 2022

A Hui Hou Jeroen!

We said a bittersweet goodbye to our Post-Doc researcher Jeroen Brijs as his fellowship at the Johansen Lab has come to a close. We wish him all the best in his future endeavors and look forward to his publications about the effects of marine heatwaves on Hawaiian coral reef fish. You will be missed around the lab Jeroen!

Team October 14, 2022

Welcome new students ʻAʻaliʻi Keling & Jonathan Rosen

We are happy to welcome ʻAʻaliʻi Keling (MSc) and Jonathan Rosen (MSc) to our lab, both of whom are working on ways to improve fish recruitment and health in Hawaiʻi.

Meet the team

Research October 14, 2022

NSF grant to study sediment runoff & herbivorous fish

The Johansen Fish Resilience Lab is happy to announce that we just received a generous NSF grant to study the effect of sediment runoff on herbivorous fish functions. This project will start in February 2023.

Team June 22, 2022

Welcome M.S. student Katherine Grellman!

We’re super excited to be officially adding M.S. student Katherine Grellman to our lab team! Kat is a familiar face to the lab as she has helped out with previous field work and other projects. Now, Kat will be researching the effects of enhanced sediment-laden algal turfs on herbivorous fish interactions!

Team June 8, 2022

Leon Tran passes oral comprehensive exam

Big congratulations to PhD student Leon Tran for passing his oral comprehensive exam for the UHM Marine Biology Graduate Program. Good work Leon!

Team June 8, 2022

Welcome new PhD student Jasmine Reighard

Jasmine will be studying how declining water quality affects reef fish stress responses! She was also awarded a grant from the National Science Foundation Graduate Research Fellowship Program (NSF GRFP) to fund her research.

Publication May 2022

New paper in Journal of Experimental Biology: Escape responses from multiple threats

*Kimura H, *Pfalzgraff T, *Levet M, *Kawabata Y, Steffensen JF, Johansen JL, Domenici P (2022) Escaping from multiple visual threats: modulation of escape responses in Pacific staghorn sculpin (Leptocottus armatus). J Exp Biol 225(9).

View all publications

Publication 2021

New paper in Communications Biology: Social familiarity improves escape performance

Nadler LE, McCormick MI, Johansen JL, Domenici P (2021) Social familiarity improves fast-start escape performance in schooling fish. Communications Biology 4(1), 1–10.

View all publications

Team August 6, 2021

Leon Tran advances to the Ph.D. track

Congratulations to Leon Tran for advancing from the M.Sc. to the Ph.D. track in the UHM Marine Biology Graduate Program. Well deserved!

Publication August 5, 2021

New paper in Philosophical Transactions of the Royal Society B: Bio-sensing in aquaculture

Brijs J, Føre M, Gräns A, Clark TD, Axelsson M, Johansen JL (2021) Bio-sensing technologies in aquaculture: how remote monitoring can bring us closer to our farm animals. Philosophical Transactions of the Royal Society B 376(1830), 20200218.

Read paper

Publication August 5, 2021

New paper in Journal of Experimental Biology: Shark escape responses

*Schakmann M, *Becker V, *Soegaard M, Johansen JL, Steffensen JF, Domenici P (2021) Latency of mechanically stimulated escape responses in the Pacific spiny dogfish, Squalus suckleyi. J Exp Biol 224(3), jeb230698.

Read paper (JEB)

Publication June 2021

New paper in Environmental Science & Technology: Oil exposure and predation risk

*Khursigara AJ, *Rowsey LE, Johansen JL, Esbaugh AJ (2021) Behavioral changes in a coastal marine fish lead to increased predation risk following oil exposure. Environ. Sci. Technol. 55(12), 8119–8127.

View all publications

Publication April 2021

New paper in Oecologia: Species interactions and thermal environment selection

*Nay T, Hoey AS, Rummer JL, Steffensen JF, Johansen JL (2021) Species interactions alter the selection of thermal environment in a coral reef fish. Oecologia, 1–9.

View all publications

Publication March 2021

New paper in Journal of Fish Biology: Epaulette shark thermal strategy

*Nay TJ, Longbottom RJ, *Gervais CR, Johansen JL, Steffensen JF, Rummer JL, Hoey AS (2021) Regulate or tolerate: Thermal strategy of a coral reef flat resident, the epaulette shark, Hemiscyllium ocellatum. J Fish Biol 98(3), 723–732.

View all publications

Publication 2021

New paper in eLife: Thermal acclimation of tropical fishes to marine heat waves

Johansen JL, Nadler LE, *Habary A, *Bowden AJ, Rummer JL (2021) Thermal acclimation of tropical fishes to marine heat waves. eLife 10, e59162.

View all publications

Publication January 2021

New paper in Science of the Total Environment: Oil exposure effects on growth and competition

*Khursigara AJ, Johansen JL, Esbaugh AJ (2021) The effects of acute crude oil exposure on growth and competition in the red drum, Sciaenops ocellatus. Science of the Total Environment 751, 141804.

View all publications

Publication July 29, 2020

Extreme heat causes loss of diversity and productivity

New paper out today in Nature Communications: extreme environmental conditions reduce coral reef fish biodiversity and productivity. This study demonstrated how marine heatwaves dramatically reshape reef fish communities on the world’s hottest reefs.

Read paper (Nature Communications)

Team June 18, 2020

Welcome new PhD student Mathias Schackmann Soerensen

Mathias will be investigating the effects of sedimentation and turbidity on coral reef fishes.

Team June 18, 2020

Welcome new postdoc Dr Jeroen Brijs

Jeroen will be investigating the effects of ocean warming on feeding energetics in reef fishes.

Team June 18, 2020

Leon Tran receives NSF GRFP award

Congratulations to M.Sc. student Leon Tran for receiving the prestigious National Science Foundation Graduate Research Fellowship Program (NSF GRFP) award. Well done!