Clownfish reproduction threatened by artificial light in coral reefs

JULY 10, 2019

by Flinders University

The popular story about a clownfish that got lost at sea in the movie Finding Nemo could have a much darker sequel—as artificial light in coral reefs leaves the famous fish unable to reproduce offspring, according to a new study.

Results from a new study published in Biology Letters show an increasing amount of artificial light at night (ALAN) in coral reefs, even at relatively low levels, masks natural cues which trigger clownfish eggs to hatch after dusk.

Lead author Dr. Emily Fobert, Research Associate in biodiversity and conservation at Flinders University, says test eggs that were incubated in the presence of artificial light had a zero success rate of hatching, with no offspring surviving as a result.

"The overwhelming finding is that artificial light pollution can have a devastating effect on reproductive success of coral reef fish," says Dr. Fobert

"When ALAN is present, no eggs hatched but when the light was removed during the recovery period, eggs from the ALAN exposure hatched like normal, so the presence of light is clearly interfering with an environmental cue that initiates hatching in clownfish."

"The results indicate increasing amounts of light have the potential to significantly reduce the reproductive fitness of reef fish who settle in a habitat near shore lines."

Read on

When anemones bleach, clownfish suffer

October 10, 2017

Coral bleaching is a well-known consequence of climate change. What is less widely known is that sea anemones suffer the same fate, and this reduces the fertility of clownfish living in these anemones, as researchers from the CRIOBE, a laboratory jointly managed by the CNRS, the EPHE and Université de Perpignan Via Domitia, have just demonstrated in French Polynesia. Following a 14-month study, they are publishing their results in Nature Communications on Oct. 10, 2017.

Like corals, sea anemones live in symbiosis with microscopic algae, which gives them their color. Symbiotic clownfish protect themselves from predators by sheltering among the anemones' tentacles, and each month, lay eggs at their base. The anemones are also protected by the clownfish that they host.

Every other day, from October 2015 to December 2016, researchers and students visited 13 pairs of clownfish and their host anemones in the coral reefs of Moorea Island (French Polynesia). This monitoring was conducted before, during and after the 2016 El Niño event that triggered a warming of the Pacific Ocean (+2°C on Moorea Island compared to the 2007-2015 average—a combined effect of ongoing global warming and the El Niño episode) and a worldwide coral bleaching episode. Half of the anemones monitored in this study bleached as they lost their microalgae. Among the clownfish living in the bleached anemones, the scientists observed a drastic reduction in the number of viable eggs (-73 percent). These fish were laying eggs less frequently and they were also laying fewer and less viable eggs, while these parameters remained unchanged among fish hosted by unbleached anemones.

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Saving Nemo: Bleaching threatens clownfish

Study reveals clownfish, the star Disney fish, and their sea anemone homes are at risk

Date: May 25, 2016

Source: University of Delaware

Clownfish became a household name over a decade ago when Disney released the movie "Finding Nemo."

Found exclusively in the Indo-Pacific, clownfish are symbiotic animals that only live in sea anemones, a close relative of corals that don't have a hard outer shell. The anemone provides a home and protection for the clownfish, while the clownfish provides food for the anemone.

As global concern grows for Australia's Great Barrier Reef -- which is experiencing the worst bleaching event in its history due to sustained high ocean temperatures amid a strong El Nino weather pattern -- University of Delaware researcher Danielle Dixson has co-authored a paper demonstrating how vulnerable clownfish are to the increased frequency of bleaching events.

Published today in Proceedings of the Royal Society B: Biological Sciences and co-authored with Anna Scott, a researcher at Southern Cross University in Australia, the paper illustrates that while clownfish can identify -- through smell alone -- if their potential home is bleached or healthy, they are inflexible in selecting a habitat.

"Unfortunately, our research has shown that bleaching does not break the symbiotic relationship between the anemone and clownfish. Clownfish are so behaviorally linked to one or a few particular anemone species for a home, that it limits their ability to acclimate if an entire reef bleaches," explained Dixson, an assistant professor of marine science and policy in UD's College of Earth, Ocean, and Environment.

"This means that clownfish are setting themselves up for bigger risk because we know that fish that go to bleached coral or anemones have an increased predation risk."

Continued … 

Young 'Nemo' clownfish roam further than thought, study shows

Australian and British scientists reveal why it was so hard to find Nemo – baby clownfish can swim up to 400km to find a home

Australian Associated Press

theguardian.com, Thursday 18 September 2014 02.10 BST

Scientists have revealed why it may be so difficult to find Nemo – baby clownfish can swim up to 400km in search of a new home.

A study, co-authored by James Cook University (JCU) researchers, shows the larvae cross large tracts of ocean to find new coral to settle on, making them better able to cope with environmental change.

“Knowing how far larvae disperse helps us understand how fish populations can adapt,” said Hugo Harrison from JCU’s centre of excellence for coral reef studies. “The further they can swim, the better they can cope.”

Continued ...

Fidgeting clownfish benefit anemones

By Ella Davies, Reporter, BBC Nature

Clownfish boost oxygen flow around their anemone hosts at night, scientists have found.

The relationship between the reef animals is well known, with the fish hiding in the anemone's stinging tentacles to avoid predators.

But US researchers have discovered the anemones also benefit from the night-time presence of the fidgety fish.

As clownfish move around, they boost water flow over the anemone and increase its oxygen consumption.

The findings are published in the Journal of Experimental Biology.

At night there is less oxygen available on the reef because photosynthesis ceases once the sun goes down. But night is also when the main predators of clownfish hunt.

"While many reef organisms can pick up and move to other areas with more oxygen, clownfish stick by their anemones; retreat is not an option," explained Dr Joseph Szczebak from Auburn University, Alabama, US who led the study.

To understand more about the nocturnal relationship of the clownfish and anemone, Dr Szczebak and colleagues travelled to the Marine Science Station in Aqaba, Jordan.

Continued:  http://www.bbc.co.uk/nature/21601006

Clownfish Talk Their Way Out of Conflict

Clownfish, the orange-, black- and white-striped fish made famous in the movie "Finding Nemo," are a gossipy bunch, popping and clicking amid their anemone homes to defend and reinforce their social status, according to new research.

Unlike the 360 other species of territorial marine fish in the Pomacentridae family,clownfish don't make a peep when mating. Researchers wondering why clownfish would bother to make noise in other circumstances discovered that their chatter helps maintain the rank and file among group members.

"Sound could be an interesting strategy for preventing conflict between group members," lead study author Orphal Colleye, a postdoctoral fellow at the University of Liège, Belgium, told LiveScience. "In terms of cost energy, you don't have to interact with another individual to determine which is the dominant and which is the subordinate, you just need to make a sound."

Continued:  http://www.livescience.com/24611-clownfish-talk-social-status.html