Fish Ecology

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Photo: MMES student Jenna Cheramie removed a terra cotta tile to measure the amount of sedimentation that has accumulated on the reef. Photo credit: R. Nemeth

Coral reefs are complex ecosystems that have evolved highly diverse connections among its inhabitants. One of the most important of these relationships is between corals, which are living animals, and reef fishes that eat marine plants, such as seaweeds or algae. These plant eating fishes (also known as herbivores) are a diverse group that includes parrotfishes, surgeon fishes, chubs and damselfishes. They are beneficial to coral reef ecosystems in many different ways. Their most important role is consuming harmful algae which can overgrow corals or make it difficult for coral larvae to find a place to live on the reef. The positive affects herbivores offer to the corals can be overwhelmed by acute and chronic stress on coral reefs such as sedimentation and warming ocean waters. When coral reefs begin to decline from these external stressors, how does this impact the herbivores?

 

The Coral Reef Environment

 

The Fish Ecology research area studies the consequences of sedimentation and changes in the coral reef environment on the health of parrotfish populations, a key coral reef herbivore.

Conceptualized model showing effects of sedimentation on parrotfish.

 

Yellowtail parrotfish (Sparisoma rubripinne) in Reef Bay, St. John, U. S. Virgin Islands is an ideal study species for examining the effects of sediment on feeding and reproduction. Photo: R. Nemeth


How Degraded Habitats Affect Coral Reef Fishes

When people clear a hillside for development or regrade a dirt road, this exposes soil that can be easily eroded during heavy rainfall that is typical of the tropics. The eroded soil is swept into streams and runs quickly downhill toward the sea. Coastal habitats, such as mangrove forests and seagrass beds, naturally filter out much of this eroded soil, but when these habitats have been damaged or removed, the soil washes out to the coral reef as large brown plumes of sediment that causes stress, damage and death to corals.  These degraded coral reef habitats may in turn create a negative feedback loop to parrotfish populations (sediment impacted coral reef → reduced parrotfish fitness → more harmful algae → further degraded coral reef → reduced parrotfish abundance → more harmful algae…). Chronic sedimentation, due to poor land development and watershed management, can contribute to the persistence of algal–dominated reefs, a common condition in the Caribbean. In order to learn if these negative feedback loop conditions exist, we  are studying the yellowtail parrotfish (Sparisoma rubripinne), which is a common and abundant parrotfish in shallow coral and rocky reef habitats of the US Virgin Islands. The yellowtail parrotfish has a unique reproductive strategy where they migrate to the reef edge and form large spawning aggregations (hundreds of parrotfish gather for reproduction) on a daily basis. This characteristic makes them an ideal model species to test the effects of multiple natural and human factors on feeding and reproductive rates.

Sediment plume in Hull Bay, St. Thomas. Photo: E Bryan

Research Goals

Using a long-term coral reef monitoring database, we are examining how past natural disturbances, such as warm water induced coral bleaching and disease events that cause wide spread coral mortality, affect parrotfish populations.  Our field-based research area focuses on the relationship between land-based sedimentation rates (low vs. high), its influence on habitat composition of turf algae (helpful) vs. macro algae (harmful), and how these factors affect the diet, feeding rates and reproduction of the yellowtail parrotfish. Our research is also measuring how oceanographic conditions influence the frequency of parrotfish spawning and their reproductive output.

We expect the research will advance our understanding of:

  1. How major coral bleaching and disease events in 2005 and 2010 and chronic sedimentation affected parrotfish abundance and diversity;

  2. How different levels of sedimentation and algae composition affect feeding rates and reproduction (frequency of spawning and fertility) of parrotfishes parrotfish;

  3. How parrotfish diet changes under different levels of sedimentation and algae composition; and

  4. How oceanographic and environmental variables influence the frequency of spawning and reproductive output of parrot fish.

Goals 1 builds upon previous EPSCoR and NOAA funded research by synthesizing and analyzing long-term coral monitoring data for changes in herbivore communities following acute and chronic disturbances such as major coral bleaching and mortality events and variations in sedimentation rates across monitoring sites. 

Goal 2 measured monthly sedimentation and algae composition across a sediment gradient inside and outside the Virgin Islands National Park, from Fish Bay (high sediment), Reef Bay (moderate sediment) and Europa Bay (low sediment), St. John. To determine parrotfish responses to these variables, we established an array of 55 acoustic receivers across our study area and tagged 60 yellowtail parrotfish with acoustic transmitters. Half the fish were tagged in areas of high sedimentation while the other 30 fish were tagged in areas low to moderate sedimentation. Both these groups of tagged fish used different spawning aggregation sites. This acoustic telemetry study tracked yellowtail parrotfish movements, feeding habitats and spawning rates for over a year. 

Goal 3 used environmental DNA metabarcoding (eDNA) to examine the diet of parrotfishes feeding in areas with different sedimentation rates and benthic algae composition. 

Goal 4 is integrating ecological and oceanographic disciplines by using data from oceanographic and temperature sensors to record environmental conditions at each spawning site. Using data on spawning frequency and plankton tows at each site, we will be able to directly measure the reproductive output of yellowtail parrotfish and calculate their reproductive success. We are also exploring novel ways of measuring spawning frequency using audio and video recordings.

The Fish Ecology research team is working closely with other R2R research areas such as watershed management, oceanographic processes and coral reef resilience to provide a more comprehensive picture of factors that affect coral reef resilience.

Study site on south coast of St. John USVI showing lots of land development around Fish Bay and western Reef Bay compared to eastern Reef Bay and Europa Bay that are adjacent to Virgin Islands National Park.

Yellowtail parrotfish migration to their spawning aggregation site. Video credit: R. Nemeth

A parrotfish spawning event. Video by R. Nemeth

Photo below:
Post doc Dr. Kayla Blincow recording data at acoustic Doppler current profiler at the western parrotfish spawning aggregation site. Photo R. Nemeth

“Results from this research will provide important connections between human activities on land and the overall condition of nearshore coral reef ecosystems including potential negative feedback loops that affect coral reef resilience. If strong relationships are found between algal cover and sedimentation rates and their effects on parrotfish feeding and reproduction, human interventions that reduce erosion and runoff from watersheds will be more critical than previously thought. These actions will be an important step to enhance the resilience of nearshore coral reefs and increase the potential for these important ecosystems to return to a coral-dominated stable state.”

— Dr. Richard Nemeth

Community Engagement & Outreach

Richard Nemeth, Ph.D.

Most of my research has focused on documenting the timing and location of reef fish spawning aggregations of commercially important species such as groupers, snapper and triggerfish. Using mark-recapture techniques and acoustic telemetry has helped to define boundaries of marine protected areas used to protect species from fishing during this critical period of reproduction. Movement ecology, using acoustic telemetry, has been applied to determine home range size and feeding habitats of a number of other species including tarpon, snappers, sting rays and sharks. 

Understanding the environmental variables and ocean conditions, such as water temperature, current speed and direction, and how they influenced timing of spawning or other movement patterns is under investigation. Early work also examined the effects of land-based development on sedimentation rates and coral health. The current interdisciplinary research efforts will integrate previous research and provide a more comprehensive view of factors that contribute to coral reef resilience.

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Meet the team


Collaborators

Tyler Smith, Ph.d.

R2R Oceanography and Coral Reef Resilience Lead Researcher, UVI Associate Research Professor of Marine Science

Marilyn Brandt, Ph.d.

R2R Marine Disease & Restoration Lead Researcher, UVI Research Associate Professor of Marine & Environmental Science

Paul Jobsis, Ph.d.

R2R Emerging Areas – Movement Ecology Lead Researcher, Associate Professor of Marine Biology

David Hensley

R2R Watershed & Land Use Lead Researcher
UVI Research Specialist III

Brittany Lancellotti, Ph.d.

R2R Watershed & Land Use Post Doc

Doug Wilson

Chelsea Harmes-Tuohy, Ph.d.

Nicolas Schizas, Ph.d.

Evan Tuohy, Ph.d.


Staff

Kayla Blincow, Ph.d.

Dr. Kayla Blincow received her PhD from Scripps Institute of Oceanography in joined the Fish Ecology and Movement Ecology research labs as a post-doctoral fellow in 2021. She recently accepted a faculty position with University of the Virgin Islands College of Science and Mathematics but continues to collaborate with Dr. Rick Nemeth and Dr. Paul Jobsis.

Elizabeth Kadison

Shaun is a research technician who joined the Center for Marine and Environmental Studies in 2007.

Sarah Heidmann

Sarah graduated from the MMES program in 2018 and was hired as a research technician with the Center for Marine and Environmental Studies in 2019.


Graduate Students

Stefanie Maxin

Stef graduated with a degree in Marine and Freshwater Science from the University of Texas in Austin in 2021. She joined the Fish Ecology lab in 2022 and is focused on using passive acoustics to examine spawning behaviors of parrotfish and groupers.

Madison Miele

Madi graduated from Western Washington University with a bachelors degree in marine biology in 2022 and joined the Fish Ecology that fall. Her thesis research will focus on the impacts of an invasive seagrass on the movement patterns of the southern stingray using acoustic telemetry.

Sierrah Mueller

Sierrah graduated from UNC-Chapel Hill with degrees in Biology and Spanish and a minor in marine biology. She joined the Fish ecology lab in 2021 and her thesis research is focused on the early life history and habitat use of the redtail parrotfish, a commercial species for which little information is known. Sierrah recently defended her thesis.

Taylor Hobbs

Taylor graduated in 2017 with a B.S. in Environmental Science: Conservation Biology and minored in Interdisciplinary Arts and Cultural Studies. Here thesis research is focused on the spawning variability in Caribbean damselfish species. Taylor recently defended her thesis.

Greg O’Neill

Greg graduated from Northern Arizona University with a bachelor’s in Biology in 2022 and joined the fish lab that fall. Greg’s thesis research is focused on the impacts of an invasive seagrass on feeding and growth of juvenile yellowtail snapper.

Kayla Budd

Kayla earned a B.S. in Ecology and Environmental Biology from the University of Wisconsin - Eau Claire. She joined the Fish ecology lab in 2019 and her thesis research is focused on the impacts of coral disease on cleaner goby population dynamics.


Past Graduate Students

Jenna Cheramie

Jenna completed a BS degree from University of Louisiana and joined the Fish Ecology lab in 2020. She graduated in 2022 and her thesis research focused on the effects of sedimentation and algal composition on feeding and reproduction of the yellowtail parrotfish. She was hired as research technician in the Fish Ecology lab to work with autonomous underwater robots that are being used to discover and document spawning aggregation sites on mesophotic reefs.

Danielle Olive

Danielle was born in St. Thomas USVI and completed her undergraduate degree in Marine Biology at the University of the Virgin Islands. She completed her Master’s degree in 2022 on the effectiveness of different management measures on the life history of mutton snapper spawning populations in the Virgin Islands She currently is a Fishery Biologist at the Department of Planning and Natural Resources Division of Fish and Wildlife in St. Thomas. Danielle continues to collaborate with Dr. Rick Nemeth.

Sophie Costa

Sophie Costa completed her Master’s degree in 2022 comparing patterns of settlement and survivorship of juvenile yellowtail snapper in invasive and native seagrasses. She currently is a PhD candidate at Florida International University.


Undergraduate Students

Arbelson Mora

Jonicia Cardin

Ver Néle Callwood

Chloe Camacho

Samuel Gittens

Keedencia Harris