Dr. Jacob L Johansen

Dr. Jacob L Johansen — Lab PI

Associate Research Professor (tenured), Hawaiʻi Institute of Marine Biology, University of Hawaiʻi Mānoa

Originally from Northern Europe (Denmark), Jacob spent over 20 years working all over the globe from Australia, South America, Middle East, Europe, Austral-Asia to USA. With a strong background in eco-physiology and behavioral ecology, Jacob's research focuses on how tropical coral reef organisms react and adapt to natural and human-induced environmental stress.

Core strengths: coral reef ecology, environmental stress responses, physiological tolerance, movement patterns and behavioral ecology of fishes. Research topics include species habitat selection, range-shift, habitat invasions, and the capacity of fishes to mitigate ongoing stressors.

Education: Ph.D. Marine Biology, James Cook University & ARC CoE for Coral Reef Studies (2012) • M.Sc. Marine Biology, James Cook University (2007) • B.Sc. Biology, Copenhagen University, Denmark (2004, High Distinction)

Appointments: Associate Research Professor (tenured), HIMB/UH Mānoa (2023–present) • Assistant Research Professor (tenure track), HIMB/UH Mānoa (2019–2023) • Research Scientist, New York University Abu Dhabi (2018–2019) • Postdoctoral Research Associate, Marine Science Institute, UT Austin (2015–2017) • Postdoctoral Research Associate, Whitney Marine Laboratory, University of Florida (2014–2015) • Postdoctoral Research Fellow, ARC CoE for Coral Reef Studies (2012–2014)

Journal editor: Reviews in Fish Biology and Fisheries (2019–present) • Coral Reefs (guest editor, 2019–2020) • Journal of Marine and Freshwater Research (2014–present)

Postdoctoral Research Fellows

Dr. Linda Eggertsen

Dr. Linda Eggertsen

Postdoctoral Researcher

Research: Predicting spatial and temporal responses of herbivorous fishes to sediment runoff. Background in reef fish ecology, seascape ecology and herbivory.

General research interest in reef fish ecology, with a background as a field ecologist studying connectivity, seascape ecology and herbivory, and its effects on ecosystem function. Investigating effects of land-based run-off (sedimentation and nutrients) on fish herbivory and fish distributions, and how runoff may impact coastal food webs and alter trophodynamics on reefs.

Graduate Students

Leon Tran

Leon Tran

Ph.D. candidate (NSF GRFP Fellow)

Investigating organismal physiology under environmental change. Focus on how individual organismal physiology drives population-level responses in species of conservation concern in coral reef ecosystems.

Current Hawaiʻi Sea Grant Fisheries Fellow and 2026 Smith Conservation Research Fellow. Research integrates organismal thermal tolerance and habitat suitability models to forecast shifts in the ecology of coral reef fish and macroinvertebrates as anthropogenic forces alter reef habitats.

Jasmine Reighard

Jasmine Reighard

Ph.D. candidate (NSF GRFP Fellow)

Investigating how declining water quality, particularly sedimentation, affects the metabolic performance and foraging behavior of herbivorous reef fish. Additionally, collaborating with loko iʻa (Native Hawaiian fishpond) stewards in Hawaiʻi to characterize the impacts of invasive upside-down jellyfish (Cassiopea spp.) on fish communities and to examine their tolerance to salinity and suspended sediment.

This work aims to inform adaptive invasive species management strategies that enhance subsistence fish production. I strive to apply my findings to fisheries management to sustain the livelihoods and identities of island nations, whether it be my family in the Philippines or Native Hawaiians or the millions of others who depend on the health of their islands' surrounding waters for economic security, food, and, importantly, joy.

Mathias Schakmann

Mathias Schakmann

Ph.D. candidate

Resilience of coral reef fishes to terrigenous run-off. Combining field and laboratory techniques to study behavioral and physiological responses to environmental stress including sediment run-off.

Early-career scientist with a passion for reef fish ecology. Interested in combining field and laboratory techniques to investigate how marine organisms respond behaviorally and physiologically to environmental stress, including temperature, water quality, pollution, and storm surges.

ʻAʻaliʻi Kelling

ʻAʻaliʻi Kelling

Ph.D. student

Assessing the influence of Native Hawaiian imu (fish houses) on juvenile fish behavior. Interests include fish-human interactions and food web sustainability with increased habitat complexity.

Recently defended M.S. thesis and returned as Ph.D. student. Research focuses on Native Hawaiian imu (traditional fish houses) and their influence on juvenile fish behavior and reef fish community assembly. Integrating Indigenous ecological knowledge with modern marine science.

Jacquin Moraga

Jacquin Moraga

M.S. student

Impacts of sedimentation on herbivorous fish foraging behavior. Born in San Diego, background in studying Hawaiʻi's reef fish responses to environmental stressors.

Originally from San Diego, California. Completed bachelor’s degree at UH Mānoa and interned at the Johansen Fish Resilience Lab. Pursuing master’s degree with a focus on the impacts of sediment on herbivorous reef fish.

Lab Staff

Shane Ribovich

Shane Ribovich

Lab Manager (2024–Present)

B.S. Marine Biology, Cal Poly Humboldt. Former Scientific Diver at Northcoast Evaluation of Reef Ecosystems. Background as marine mechanic, aquarist and carpenter. Collaborating with NOAA Fisheries.

B.S. Marine Biology with a Minor in Oceanography from Cal Poly Humboldt. Former Scientific Diver at Northcoast Evaluation of Reef Ecosystems Organization performing long-term Marine Protected Area monitoring surveys. Experience as Field Research Technician with the California Collaborative Fisheries Research Program. Background as marine mechanic, aquarist, and carpenter. Collaborating with NOAA Fisheries on lab and field-based operations.

Alumni

Jonathan Rosen

Jonathan Rosen, M.S.

First position after graduating: Knauss Fellow, U.S. Government.

Juliana Andrade

Juliana Andrade

Ph.D. Exchange Student (2025). Now: completing Ph.D. in Brazil.

Taylor Souza

Taylor Souza, Ph.D.

Former Ph.D. affiliate (Stanford). First position after graduating: Teacher, Le Jardin Academy, Kailua.

Dr. Jeroen Brijs

Dr. Jeroen Brijs

Postdoctoral Fellow. First position after leaving lab: Research Fellow, University of Innsbruck, Austria. ResearchGate

Katherine Grellman

Katherine Grellman, M.S.

First position after graduating: Research Specialist, The Nature Conservancy (Coastal Science).

Gustav Kronholm

Gustav Kronholm, M.S.

Exchange M.Sc. student from Denmark. First position after graduating: pharmaceutical production industry, Denmark.

Chloe Moore

Chloe Moore (Pixie)

Former Lab Technician. First position after leaving lab: NOAA technician

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