Nav: Home

Secrets of fish population changes revealed

June 07, 2018

Populations of fish in the ocean are notoriously variable, waxing and waning in often unpredictable ways. Knowing what drives changes in fish population sizes is important for managing fisheries and conserving species.

For the first time, scientists have linked the ecology of adult fish populations inhabiting coral reefs with the dispersal of baby fish between reefs, reporting the dynamics of a living network called a "marine metapopulation."

"It's not like studying deer in a forest, where one need only count births and deaths to understand how population size changes, which is difficult enough," says senior author Mark Hixon, professor in the Department of Biology at the University of Hawaii at Manoa.

"The challenge of understanding changes in reef fish abundance in a metapopulation is to measure simultaneously egg production by adults on multiple reefs and the dispersal of baby fish among those reefs, as well as other factors," explains first author Darren Johnson, assistant professor in the Department of Biological Sciences at California State University, Long Beach.

Challenge indeed. Like many ocean species, most coral reef fishes cast their tiny babies (called "larvae") into the ocean currents, where they may or may not eventually find a reef on which to settle.

"The larvae are like lottery tickets, some of which are lucky and most of which perish," reports co-author Mark Christie, assistant professor in the Department of Biological Sciences at Purdue University. "The larvae that survive may return to the same reef as their parents or settle on a reef hundreds of miles away."

But how can these tiny babies be tracked, let alone linked to their parents?

New genetic methods analyzing small samples of fin tissue from captured and released fish allowed the scientists to compare adult bicolor damselfish in the Bahamas with baby fish appearing on the same or other reefs over three years, thereby matching parents with their offspring.

"Such patterns of larval connectivity have now been documented many times using genetic methods," says co-author Tim Pusack, assistant professor at Williams College, "but we closed the population life-cycle loop by integrating larval dispersal with egg production by adults."

Quantifying what they called "demographic connectivity," the scientists calculated larval dispersal as a function of initial egg production by adding artificial nests to reefs in which the damselfish laid their eggs.

"We counted how many eggs each nest produced, thereby learning how many offspring were produced at each reef," reports co-author Christopher Stallings, associate professor in the College of Marine Science at the University of South Florida. "Combining these data with the genetic parentage data, we were able to estimate how many of the larvae that leave a reef come home, and how many travel to other reefs."

The most important reefs for replenishing the overall metapopulation showed high levels of successful larval dispersal relative to the number of eggs produced.

Studying only larval dispersal alone, or egg production alone, both typical of previous studies, did not provide a clear picture of the drivers of fish abundance.

"This is the first field study to successfully measure both dispersal and egg production," reports Oregon State University fisheries oceanographer J. Wilson White, who was not involved in the study. "These results reinforce the need to link those two pieces to understand population changes."

The integration of such difficult to measure information will allow scientists to identify the most valuable reefs to protect for conservation and management of coral reef fishes.
-end-
Funded by the National Science Foundation, this research was recently published in the peer-reviewed scientific journal Ecology.

University of Hawaii at Manoa

Related Biology Articles:

Experimental Biology press materials available now
Though the Experimental Biology (EB) 2020 meeting was canceled in response to the COVID-19 outbreak, EB research abstracts are being published in the April 2020 issue of The FASEB Journal.
Structural biology: Special delivery
Bulky globular proteins require specialized transport systems for insertion into membranes.
Cell biology: All in a flash!
Scientists of Ludwig-Maximilians-Universitaet (LMU) in Munich have developed a tool to eliminate essential proteins from cells with a flash of light.
A biology boost
Assistance during the first years of a biology major leads to higher retention of first-generation students.
Cell biology: Compartments and complexity
Ludwig-Maximilians-Universitaet (LMU) in Munich biologists have taken a closer look at the subcellular distribution of proteins and metabolic intermediates in a model plant.
Cell biology: The complexity of division by two
Ludwig-Maximilians-Universitaet (LMU) in Munich researchers have identified a novel protein that plays a crucial role in the formation of the mitotic spindle, which is essential for correct segregation of a full set of chromosomes to each daughter cell during cell division.
Cell biology: Dynamics of microtubules
Filamentous polymers called microtubules play vital roles in chromosome segregation and molecular transport.
The biology of color
Scientists are on a threshold of a new era of color science with regard to animals, according to a comprehensive review of the field by a multidisciplinary team of researchers led by professor Tim Caro at UC Davis.
Kinky biology
How and why proteins fold is a problem that has implications for protein design and therapeutics.
A new tool to decipher evolutionary biology
A new bioinformatics tool to compare genome data has been developed by teams from the Max F.
More Biology News and Biology Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at Radiolab.org/donate.     You can read The Transition Integrity Project's report here.