Guest Blogs

This is a section of the blog that I am really excited about.  It is where I will invite colleagues, friends and other bloggers to submit a blog entry. It is my hope that this section will allow me to cover a wider array of topics, and allow you to meet some other interesting people and share in their stories and passions.

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The Truth About Nemo

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I am again lucky to have a great guest blog from a good friend and great scientist, Maarten De Brauwer. Maarten is a tropical marine ecologist who comes from Belgium and now lives in Australia. Maarten works on the extinction risk of reef fishes, ecology/importance of cryptic marine fauna and has a special interest in Indonesia reefs.

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Anemonefishes, also widely known as clownfishes, have long since been a favorite in the marine aquarium world. These charismatic and beautiful fish and the relationship with their hosts – sea anemones – have fascinated and amused scientists and aquarium enthusiasts for many years. The box office success of the Pixar movie “Finding Nemo” in 2003 made the fish widely known and hugely popular with the general public. Unfortunately, the message of the movie (wild fish should not be kept in tanks) got lost somewhere along the way and the exact opposite happened: an explosive increase in the trade in “Nemo”.

 

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Amphiprion percula “Nemo”

Clownfish as a species are widely known, but besides Nemo’s relationship with its “anemenemone” and its pretty colours, surprisingly little about clownfish biology reached the general public. Amphiprion percula (= scientific slang for “Nemo”) is only one of the 28 species of anemonefishes found globally. The 28 species are found from the Red Sea all the way to French Polynesia in the central Pacific Ocean, leaving the eastern Pacific and Atlantic Ocean devoid of these beautiful creatures. They can be found as far north as southern Japan and almost as far South as Perth, Australia. Many of the species are endemics; occurring only in a very small area. In the clownfishes’ case the endemic species are often found around small oceanic islands such as Seychelles, Mauritius or Chagos Archipelago.

While the adventures of Nemo and his dad in the Pixar movie were positively thrilling, reality in the case of the clownfish far surpasses fiction. The life of an anemonefish is a big adventure, from start to finish, with lots cliff-hangers and unexpected twists in the plot. After baby clownfish hatch from their eggs, they don’t simply move into their parents’ anemone. Instead, they float on the ocean currents for about three weeks, sometimes travelling up to 400km before settling into a suitable anemone. After moving into their new anemone, they transform from a see-through, wormlike larvae into a colourful miniature version of the adult fish. However, every single one these tiny clownfish will be, without exception, male. As a matter of fact, in any social group of clownfish, every individual will be male except for the largest fish. This dominant fish is female and will only mate with the largest male in the anemone.

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Amphiprion clarkii with eggs

 

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Amphiprion clarkii eggs

An interesting thing happens when this female dies (say, in the unlikely event she gets eaten by a barracuda), leaving the anemone looking very much like an all-male dorm room in a university, a lot of males wanting to mate, but no female to be found. To solve this problem, the biggest male will change sex, turning into the dominant female, with the next biggest male growing bigger and becoming the breeding male. (I’ll leave the human dorm room-version of this to your imagination) In other words, by the time Nemo’s father actually finds Nemo, it should really have been his mother again…which might have confused children and quite a few parents, but could have made for a very interesting movie in my humble opinion.

Unfortunately, not all is well for the anemonefishes, and the future of some species is could be in serious threat. Over the course of the last year, I collaborated with a great number of outstanding scientists to assess the risk of extinction of all 28 species of anemonefishes. The result of this collaboration is a rather large, global database, which tells us a lot of what’s happening with these fish. A few general conclusions can be made about their extinction risk.

The factor that affects the risk of extinction most strongly, is what gives these fish their name; their obligate relationship with a few species of sea anemones. Anemonefish can only use 10 species of sea anemones, and most species of fish will use only 1 or 2 host species. In the absence of anemones, the fish cannot survive on the reef; reefs without sea anemones will not have any anemonefish. Sea anemones are generally rare on coral reefs, an average of less than 0.2% of the area of coral reefs consists of suitable host anemones. Therefore, living in sea anemones might be safer for the fish which are already inside the anemone, but it makes finding a suitable place to live a lot harder for larval fish.

The quantity of host anemones is already small, but currents trends indicate that it is very likely the quantity will decrease even further in the future. Rising sea temperatures, increased acidification can cause host anemones to bleach and perish. Anemone bleaching is the same mechanism as coral bleaching; single celled algae living in the anemone are expelled, after which the anemone loses colour and is hard pressed to catch enough food to sustain itself.  As a result, anemones can shrink, are more susceptible for disease or can die off completely. In recent years, anemone bleaching events have occurred and caused localised disappearance of host anemones and the anemonefish living inside them.

While anemone bleaching might become more frequent in the future, it will rarely occur on a large enough scale to effect the anemonefish species with a wide distribution. The more area a species occupies, the less likely it becomes that the entire area will be affected by bleaching. Which brings us back the many endemic anemonefish species, these are the species that do occupy a small area. In the case of at least three species, it is entirely conceivable that the entire area occupied by the fish is so small, that all of the available host anemones could bleach in one event, potentially removing most of the habitat of the species of anemonefish dependant on it.

A last risk factor, overfishing could also play a role. The popularity of clownfish in the aquarium trade is bigger than ever before, and is likely to increase further with the sequel of “Finding Nemo” planned to be releases in 2016. Overfishing and destructive fishing practices in South-East Asia are known to have caused big declines in clownfish and host anemone populations. While these disturbances are significant on a local scale, they rarely affect the species as a whole. Furthermore, most species of anemonefish can readily be bred in captivity.

So what can we do about these threats? Since the biggest threat, bleaching is hard to remedy, the best we can do at the moment is reduce other stressors (such as overfishing and pollution) by protecting larger areas of coral reef habitat. Bleaching is most often induced by high water temperatures, which are affected by global climate change. So ultimately, the survival of some species of anemonefish, might depend on much bigger challenges, which we can all do small things about, but would take this blog too far away from clownfish.

Finally, try to follow the morale of “Finding Nemo”, don’t keep fish in tanks. And if you do feel the overwhelming need to see Nemo in your own house, make sure it has been bred in captivity and not a poor creature removed from its home anemone on a pristine tropical reef on the other side of the world.

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Amphiprion perideraion on the Great Barrier Reef

 

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Brazilian Coral Reefs

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I am very lucky to have a guest blog from a good friend and a great early career scientist from Brazil,  Carla Elliff. Carla is an oceanographer working with Brazilian coral reefs and the ecosystem services they provide. The main goals Carla is striving to reach are to increase ocean conservancy measures, sustainable options and public awareness.

 

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Carla Elliff

 

People always talk about how unique coral reefs are as an ecosystem, but sometimes we fail to think how different each reef is to each other. This is particularly true when considering Brazilian coral reefs in comparison to other nations.

Coral reefs in Brazil have four main traits that set them apart from other reefs around the world.

The first are these amazing structures that only occur in the reefs of the Abrolhos bank, called chapeirões. These mushroom-shaped coral pinnacles can reach more than 25 m in height and 50 m in diameter. Why they grow like this and why only in Abrolhos is still quite a mystery.

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Figure 1. Sketch of a small mushroom reef from the Abrolhos coastal reef arc, which is commonly found surrounding larger bank reefs.

The second is the low diversity and high endemic rates of these reefs. While coral reefs from the Indo-Pacific Ocean sum hundreds of species, in Brazil there are just under 20 species of reef-building corals. But don’t feel bad for the Brazilian reefs! Although there are few species, the major reef builders are endemic, meaning they only occur in Brazilian waters, which is pretty special. Some of these endemic species have affinities to species in the Caribbean, while others are related to Tertiary coral fauna, which means their closest relatives go way back (between 2.6 and 65 million years) and thus earned them the name of archaic species or relic forms.

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Figure 2. Mussismilia braziliensis, an archaic species endemic to the Brazilian coast.

The third trait concerns the important role that incrusting coralline algae has in the construction of the reef structure in Brazil. In fact, the only atoll found in the South Atlantic Ocean, called the Rocas Atoll, is basically composed by crustose algae. This has raised much discussion regarding the accuracy of considering Rocas an actual atoll.

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Figura 3. Rocas Atoll

Lastly, unlike most reef systems, in Brazil nearshore bank reefs are surrounded and even filled with muddy sediments from the continent. For most coral species this condition would make the waters uninhabitable, however, remember what I said about the endemic species? These species seem to be particularly sturdy and have developed mechanisms to cope with the higher sedimentation rates that can affect turbidity.

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Figure 4. Diving in pea soup at the reef of Boipeba Island, Brazil.

Despite these differences, Brazilian reefs also support an immense biodiversity and provide important ecosystem services. Diving in Brazil is definitely a scuba-lover must!

 

 

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The Shark Finning Trade by Joseph Cavanaugh

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I am so happy to have my first guest blog by a friend and mentor of mine, Joseph Cavanaugh.  This blog entry is on the shark finning trade.  Joseph is a marine biologist from Florida who is working to protect endangered marine species such as sea turtles, smalltooth sawfish, and right whales in St. Petersburg, Florida.  He is currently working on a shark fin project you can read more about on his blog:  http://thesharkfinproject.blogspot.com/

Joseph on a dive

Joseph on a dive

The consumption of shark fins, particularly in China, likely began prior to the Ming Dynasty (1368–1644).  By the time the ethnic Han Chinese came to power in the Ming Dynasty, shark fin soup became the Haute cuisine at banquets and special occasions such as weddings for royalty.  However, sharks and their fins were unlikely to have been targeted or kept once captured by fishers during this era.  Historically, there were small-scale shark fisheries that targeted sharks only beginning in the twentieth century for shark leather (West Indies in the 1920’s) and shark liver oil (1930’s on both coasts of the United States).  Fishing sharks for shark liver oil grew over a decade prior to World War II primarily to supply vitamin A to the U.S. and shark populations along both coasts were quickly depleted.  The interruption of this fishery by World War II and the advent of synthetic vitamin A in the early 1950’s granted a reprieve for shark populations.  Today the main driver for shark fisheries worldwide is to supply an ever-growing demand for fins to an emerging middle class in China.  Although there is some medicinal and pharmacological value for shark cartilage and other shark liver oil, sharks are primarily fished for their fins alone and these end up in bowls of shark fin soup once again served at banquets and weddings but now affordable to the masses. 

Joe and his son Finn with their fins up!

Joe and his son Finn with their fins up!

Shark finning is a particularly heinous and destructive method of fishing that involves cutting the fins off sharks and discarding the still-living animals back into the water to die a slow, painful death.  Only the fins are utilized and the rest of the shark is wasted.  Shark populations worldwide of which there are greater than 350 species, share a special status at the top of the trophic web or what we called the food chain until recently.  As is true of most apex predators, sharks are slow to reproduce and when they do, usually produce few offspring.  There is no dispute that current fishing practices have depleted many species of sharks to the brink of commercial extinction.  In fact, at this year’s CITES meeting in Bangkok, the oceanic whitetip shark, porbeagle, and three species of hammerheads, and both manta rays, were added to Appendix II protection ensuring that permits for trade in these species are legal and sustainable.   It is truly remarkable that in just a few decades after the Movie Jaws vilified sharks there are now a multitude of non-govermental organizations spearheading conservation campaigns for sharks worldwide.  In the 1970’s there were hundreds of shark tournaments on the east coast of the United States alone with a myriad of prizes offered including a “most sharks killed” category.  There is finally awareness among many nations and their citizens that sharks play a valuable role in our ecosystems.  Yet, international laws and enforcement protecting sharks are woefully inadequate in stemming the loss of what is estimated to be more than 100 million sharks a year.  The problem is largely one of market forces (supply and demand) and cultural mores that facilitate the demand for fins in China.  The Chinese communist government does not demonstrate transparent trade data for shark fins and there are growing crime syndicates that specialize in trafficking fins while international pressure increases on China to stop consuming shark fin soup.

This summer I depart to Hong Kong to investigate some of the cultural mores behind the trade in shark fins to better understand the problem and hopefully glean possible solutions.  I am convinced that without effective education and outreach campaigns targeting shark fin consumers, there is little hope we can curb finning before many species of sharks are gone in say, five to ten years, conservative estimate.   Just as with other unsustainable fisheries such as Bluefin tuna we know that as species become increasingly rare their market value increases to absurd levels, until the supply crashes and species become so rare that it is prohibitively expensive to target those species anymore.  Unfortunately for sharks, millions are killed each year as bycatch in long-line and other fisheries, creating a juggernaut for sharks to survive even without the specific shark finning fisheries.  If sharks species are to survive and rebound, the cultural mores in China will need to change rapidly.  There is a generation of Chinese who grew up dirt poor in the Cultural Revolution (1966-1976) whose children are now getting married and their parents can afford to serve shark fin soup at their weddings.  Convincing these parents of alternatives to shark fin soup is an important key component in ending shark finning.  There is little time left to change the tide for sharks and already it will take decades for worldwide populations to recover.

To read more on Josephs efforts against Shark finning please check out his blog:  http://thesharkfinproject.blogspot.com/

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One thought on “Guest Blogs

  1. Hey emma, your side is really really impressing. you definitely can see that you have your heart in your occupation and all this here. I like it

    regards
    Judith

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