Mangroves, The Marls, Abaco, Bahamas (Keith Salvesen, Rolling Harbour)


For some time now, there has been understandable concern about the increasing evidence of mangrove die-back in the Abaco Marls and elsewhere in Abaco waters. Scientific investigations are ongoing and you will find some of the survey results so far on the excellent Abaco Scientist interactive map HERE. You’ll find other relevant and authoritative mangrove material if you check out the BLOG menu of the website.
Abaco - The Marls

The ‘200 sq. miles’ in my map is debatable, depending what one includes. Other estimates are of 300 or even 400 sq. miles. Whichever, the Marls cover a massive area of mangroves, islets, flats, channels and wonderfully diverse wildlife. A large proportion of the many species – fish, birds, turtles etc – depend on the complex ecology of the mangroves for food, shelter and breeding. Depletion of the mangroves from whatever cause will have a direct effect on the creatures of the Marls.

Stingrays Abaco Marls 6

Ryann Rossi, a PhD student with North Carolina State University, has been researching the worrying phenomenon of mangrove die-back in the Marls this summer. She has written an interesting and informative  account (conveniently in the RH ‘Facts about…’ style) that was published in Abaco Scientist last week. The blue links will take you to the ABSCI site for further information on each topic. I’m grateful to Ryann and ABSCI for permission to use the material.

Five Things to Know About the Mangrove Die-back in The Marls (at this point, anyway)

1. This die-back appears to be the result of multiple stressors acting together. Think of it in the sense of our own body – when our immune system is down, we are often more susceptible to getting sick. The same thing is likely happening to the mangroves.Mangrove Die-back 1 (Abaco Scientist : Ryann Rossi)

2. It appears as though a fungal disease may be taking advantage of already stressed mangroves and causing die-back. We did preliminary surveys across Abaco and found fungal lesions nearly everywhere. However, the fungus was present in different densities in different areas. In the die-back area nearly all the leaves remaining on trees have lesions. We think that this pathogen capitalized on the mangroves being weakened by other stressors such as hurricanes, which cause extensive leaf drop, change in the movement of water, change in sedimentation and erosion.

Mangrove Die-back 2 (Abaco Scientist : Ryann Rossi) jpg

3. We are still working on identifying the pathogen associated with the lesions we’ve found. We are confident that it is a fungus and are currently growing fungal cultures in the lab to examine defining morphological characteristics in addition to using DNA sequencing to identify the culprit.

4. We have documented the presence of the Robust Bush Cricket (Tafalisca eleuthera) in the die-back areas as well as other areas with high densities of lesions. These crickets are documented to consume Red and White mangrove leaves. As such, we were concerned about their potential role in die-back. We set out a caging experiment to exclude the crickets from certain dwarf Red mangrove trees to see just how much grazing they may be doing in the die-back area. This experiment is ongoing.

Mangrove Die-back 3 (Abaco Scientist : Ryann Rossi) jpg

5. The take home: there is likely more than one causal agent of the die-back in The Marls. Many factors govern mangrove productivity and functioning: nutrient availability, salinity, sedimentation rate, herbivory, and disease are just a few of the factors that contribute to overall mangrove function making it very difficult to pin point which factors may be driving the die-off. On the bright side, we are confident that we have a lead on the causes and we are working hard in the field and laboratory to fully understand what is going on in The Marls.

By Ryann Rossi|August 26th, 2015|Disease, fungus, Insects, Mangroves and Creeks, The Marls
All pics below taken while fishing on the Marls except Melinda’s shark (I’ve never got a good one)
Hawksbill Turtle, Abaco Marls (Keith Salvesen)Bonefish Abaco Marls 4Shark 4 ©Melinda Riger @ G B Scuba copyOsprey - Abaco Marls 1 Reddish Egret (White Morph), Abaco MarlsRoyal Tern, Abaco, Bahamas (Marls) 3Willet, The Marls, AbacoSouthern Stingray, Abaco Marls (Keith Salvesen 4)
FRIENDS OF THE ENVIRONMENT has also included an article on die-back by Ryann in its latest Newsletter:

Mangrove Die Off on Abaco by Ryann Rossi, NCSU

This summer Stephanie Archer and I continued research efforts focused on determining the cause of the mangrove die-off in The Marls (work funded by the National Science Foundation). Our efforts were predominantly focused on the fungal pathogen we found associated with the die-off site. We created a small citizen science and outreach project to document the presence or absence of the pathogen across Abaco. This project consisted of short surveys and leaf collections. In total, 92 areas were surveyed including locations from Abaco and San Salvador. We also took this outreach project to the annual Bahamas Reef Environment Education Foundation (BREEF) teacher training conference.  There we disseminated survey packets to teachers from islands throughout The Bahamas who will help us collect more data on the presence (or absence) of this pathogen on other Islands.

3 men on a skiff, Abaco Marls (Keith Salvesen : Rolling Harbour)

Three men on a skiff – Abaco Marls

On Abaco, we constructed an experiment to investigate the role of grazing and the presence of fungal lesions on Red mangroves. We simulated grazing using crafting scissors to cut small sections on 600 leaves in 4 different mangrove creeks. We observed the leaves for 28 days to determine if cutting leaves predisposed leaves to fungal infection. At these sites we also trapped for insects to gain an idea of what kind of grazers may be chewing on the leaves. We also did a series of disease incidence surveys that will be routinely monitored for disease progress over the next 2 years. These surveys will allow us to systematically track the progress of the disease. In addition to our field work, we spent many hours in the laboratory isolating fungi from leaves to grow in culture. These cultures were brought back to North Carolina State University and will be sequenced in order to help us identify the fungal pathogen responsible for making the lesions on the mangrove leaves.

Mangroves, Abaco Marls (Keith Salvesen)

Credits: Source material Ryann Rossi; Abaco Scientist; all photos © Keith Salvesen @ Rolling Harbour except those by Ryann / ABSCI in the main article and Melinda Riger’s cool shark


Great Egret Abaco 7


The piratically named Treasure Cay (aaarrrrrr…) is north of Marsh Harbour, and home to one of the larger communities on Abaco. It has a wonderfully long white sand beach, a golf course, condos and villas, a marina and a cheerful atmosphere. It is also one of the best areas in North Abaco for birding. There are the shorebirds, of course, and all the usual ‘settlement’ species. In addition, the golf course has freshwater ponds where you will find a wide variety of duck and other water species. NB Check in at the Club House and get permission first – amiably given if politely requested (see map below).

Treasure Cay also has a large area of bays, brackish inlets and lagoons, including – to continue the pirate theme – Galleon Bay, Brigantine Bay, Cannon Bay and Gun Powder Creek. And also White Sound. This can be reached by luck (which may run out) or good management (ask for directions; wait for me to get back the map I have lent to someone and post a grab from it). Drive (with care) along the uneven track beside the lagoon and there is a good chance you will see Great Egrets in the mangrove islands dotted around the middle of the water. This is what to look out for…Great Egret, White Sound, Abaco

Zoom in a bit, and you’ll see two more egrets on the far side of the clump of mangroves. It’s a colony… in the end we were able to count 9 birds on this one mangrove island.Great Egret Abaco 1

One of the loveliest features of these fine birds in breeding season is the way that even a slight breeze will blow their long plumes away from their bodies like streamersGreat Egret Abaco 2Great Egret Abaco 3

We were some way from the birds, as these rather indifferent photos suggest, so we decided to try and get closer. The water was fairly low, leaving expanses of firm-looking marly mud around the edge. There was an apparent causeway to an overgrown rocky outcrop that would enable us to get closer to a vantage point without being spotted. As it turned out, the mud was only… ankle deep. It could have been messier. And we had a chance to see at close quarters the remarkable way in which mangrove entanglements develop.

Great Egret Abaco 4 Great Egret Abaco 5

We reached the outcrop muddier and slightly wiser, and clambered up through the scrubby and scratchy bushes to the top, nothing if not intrepid. My wading stick came in handy for beating a rough path. And by adopting strange stances in the manner of someone trying to pick up a faint cellphone signal, we could peer through the foliage to establish whether we were indeed a bit closer to the egrets.Great Egret Abaco 6

The answer was yes. But there was another obstacle, familiar to all fellow ‘focus fail’ offenders. Shooting a bird through a hole in a bush straight in front of you is complicated. You get a vivid detailed  frame of greenery, with a blurry centre of unintentional and unwanted BOKEH instead of the intended subject. A lens entension (the poor man’s zoom that I use) tends to make it worse. So you’ll have to make do with these pictures for now, until you can visit White Sound and get your own with your natty Nikon. Great Egret Abaco 11Great Egret Abaco 9Great Egret Abaco 8

My favourite ‘stance’ shotGreat Egret Abaco 10

That wasn’t the end of the adventure. After we had squidged our way back through the slightly smelly mud, we moved further along the sound, to find a further egret colony on the far shore just in time to watch them from afar as they took flight.Great Egret Abaco 12 Great Egret Abaco 13 Great Egret Abaco 14



When leaving Treasure Cay, visitors receive a friendly reminder to return, in terms reminiscent of, yet far nicer than, a Scottish Tourist Board brochure. Maybe this reflects the historic significance of the Scots in the history of the Bahamas, to the extent that there is even a Bahamas tartan. 

Bahamas TartanHaste Ye Back...

TC Map credit: Abaco Estate Services. They send me emails, so I guess they won’t mind publicity here


Reddish Egret (White Morph) Abaco 5


Contrary to appearances from the header image and the one below, Reddish Egrets (Egretta rufescens) do not yet use cellphones to communicate. Nevertheless, the trick of having a good ear-scratch while standing in water on one leg is a good posey accomplishment.Reddish Egret (White Morph) Abaco 4

All these photos were taken while we were bonefishing from a skiff far out on the Marls in the mangroves. Ishi poled us closer so that boat-partner Tom – a real photographer – could get some shots. Meanwhile, I did my best with my little camera that I take out on the boat – the one that won’t matter too much when it slips from my hand or pocket into the drink. These things happen: I lost a good pair of Costas that a gust of wind unkindly whisked away when I took them off to change a fly.Reddish Egret (White Morph) Abaco 3Reddish Egret (White Morph) Abaco 2

This egret comes in two very different ‘colourways’. The classic version has a slatey-blue body and a reddish head and plumes. The white morph is pure white. The only similarities between the two are the two-tone bills with the black tip; and the blue-grey legs and feet.

True Reddish Egret, as you might expect it to lookReddish_Egret Wiki

The white morphReddish Egret (White Morph) Abaco 9

I’m not certain of the proportions of each type on Abaco, but I have certainly seen twice as many white ones as true reddish ones. There seem to be quite a few around – there are plenty of fish for them and dozens of square miles of human-free space in which to stalk them. However as with many (most?) of the bird species, there is a declining population for all the usual man-related reasons, and these fine birds have now had to be put on the IUCN ‘near-threatened’ list.220px-Status_iucn3.1_NT.svg

The bird kept an eye on us as we drifted closer, but was unperturbed. It continued to poke around in the mud, and occasionally it moved delicately but quite quickly to a different patch.Reddish Egret (White Morph) Abaco 8 Reddish Egret (White Morph) Abaco 7 Reddish Egret (White Morph) Abaco 6

We watched the bird for about 10 minutes. Then we returned to what we were really there for – Tom to catch bones with practised skill, and me to wave the rod incompetently around until some passing fish took pity on me and grabbed my fly, knowing it would soon be released once all the fuss was over…Reddish Egret (White Morph) Abaco 1



Laughing gulls. Amusingly raucous and raucously amusing. Unless, maybe, you are living right next to a breeding colony during a collective fit of hysterics. These gulls, Leucophaeus atricilla, will be familiar to anyone on the Atlantic coast of North America; in the Caribbean; and further south to the northern coastal areas of South America. In winter, their migration pattern simply involves relocating to the southern parts of their range. They are easily recognisable in the breeding season by their smart black caps, though this fades in winter. And by their unmistakeable call, of course. Immature birds tend to be darker than adults. They breed in large colonies, each female laying 3 – 4 eggs. And like most (all?) gulls, they’ll eat pretty much anything.

Laughing Gull Conservation Status

We saw – and heard – plenty while bonefishing on the Abaco Marls in June. I took some rather grainy distance shots, as they tended to fly off as the skiff was slowly poled towards them. This gull has found a good vantage point for some quality preening among the mangroves.

The pair below stayed put, and watched our gradual approach with suspicion that turned into noisy protest as we poled past them. I presume they were defending their territory – probably a nest site nearby.

I took a very short video just before they flew off as we drifted by. Apologies for the sound of the breeze – I’ve no idea if it’s possible to reduce the background noise while retaining the bird call. Listening to online bird sound clips (e.g. on the excellent Xeno-Canto) I think not. Or not without expensive editing equipment of a complexity I can’t face…

And here (thanks, Don Jones @Xeno-Canto) is what laughing gulls sound like when one of them has told the one about the bonefish and the shrimp…



The rollingharbour wildlife enterprise doesn’t normally mix with the technical side the bonefishing on Abaco in general or at the Delphi Club in particular. rh is personally adept at failing to boat fish even where he is lucky enough to hook up; and in turning genial, amiable guides into scowling cursing wrecks in a day.

This is an exception: an excellent 4.5 minute video from Dr Aaron Adams (marine biologist and Bonefish & Tarpon Trust Operations Director) on how to maximise your chances on the mangrove flats by not spending hours flogging the water pointlessly in obviously unproductive areas. Clearly if you have a guide, this is unlikely to happen – but what if you are wading or otherwise going solo? 

The reason to post this informative video here is for the insight into the structure of mangrove swamps, with clear underwater photography and commentary as a skiff glides the flats over ‘dead’, & productive, areas. What is a mangrove swamp? Where do the fish favour? Why? This video will help your understanding.


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