- Adric observes a trio of conchs. photo by C. Booker
The surveys and our 2011 field season are officially completed! We’ve left the Exuma Cays Land and Sea Park, and the volunteers have traveled back home, but there is still a lot to say. Now with better internet access, I think it would be a shame to stop the blog. As we have more time to reflect on this expedition, I know there will be more for us to share. Scientific results aside, we learned a lot on this trip, and I think it is important to continue the conversation with a broader audience.
So, for our first post-expedition post, we’re going to recognize one of our veteran volunteers, Andy Mclean, who shall now be know as the conch whisperer.
Part of our reproductive study of queen conch this year involved determining whether the animal was male or female. This is very difficult to do without sacrificing the animal, because conchs are very shy. They have that big, hard shell to protect their soft bodies, and they use it whenever they sense danger. If disturbed, a conch may retract its entire body back into the shell and stay there until it is sure that the threat has passed.
The best way to find out if a conch is a girl or a boy is to look for the presence or absence of the male’s reproductive organ, “the verge”. The verge is easy to spot if the conch is out of its shell, though it is very rare (but possible) to catch a conch extending its body far enough out of its shell.
Andy became our expert at using non-invasive, non-lethal techniques to determine the sex of a conch. He was patient. He was non-threatening. He knew just where to look when a conch decided to emerge, and make a “run” for it. (Conchs are very, very slow, so it is really more like a “crawl for it”.) As Peyton put it, “Andy’s got the urge to see the verge emerge.”
We are not sure why this talent would be useful in any other setting, but perhaps you will see Andy featured in his own T.V. show one day…
As a nine year old kid I ordered a set of goggles, snorkel, and fins from Montgomery Ward Catalog. I taught myself to snorkel in the college pool as my Dad taught his Water Safety Instructor courses. As the students swam their laps and did their tasks I dove in and among them imagining all kinds of scenarios with me being in the Bahamas; diving the warm Caribbean waters instead of the chlorinated, heated pool at Chadron State College.
In these imaginary adventures there were any number of animals; sharks, rays, morays, and octopus. Now, years later, (and we won’t count how many…though the reference to the “Monkey Wards” Catalog should give you a hint) here I am actually in the warm waters off the sands of Warderick Wells Cay in the Bahamas. I’m here having adventures with conch. Yea, there are sharks, rays, morays and octopus around…be we are concentrating on the queen conch.
A friend sent me an email about the Community Conch project and said he thought I might be interested. I looked into it, and I was. I contacted Catherine and said I was very interested in coming to the Exuma Cays Land and Sea Park and helping any way I could with the project. She said come on down.
So I did. I wanted to observe the methods and protocols of their conch surveys. We do similar survey work along transects, only in terrestrial habitats. Our work revolves around the effects of different grazing schedules on grass, invasive weeds, and breeding birds. One of the major problems is always in insuring your sampling is unbiased and that your subsequent analysis is accurate. Community Conch has the same concerns and coming from such a different environment to watch and learn from them helps me to evaluate our sampling and our monitoring work.
One aspect of the surveys, towing an observer behind the boat, head and mask in the water looking down and counting conch, reminds me of doing large mammal surveys from an airplane…flying above and counting only those viewed through a special frame on the plane…though in doing that you don’t have to worry about the speed of the plane pulling your swimming suit down to your ankles. OK, that only happened once! However, this compare and contrast activity, or “cross fertilization” as Martha calls it, is exactly what I had hoped for.
If nothing else this has been a wonderful change for me. First, as you would expect, the Bahamas in July are about as different from Nebraska in July as you can get; secondly, I’m working in sea water instead of the open grasslands or the gravel mine lakes that I frequent at home. Lastly, while I’ve been on any number of recreational dive trips over the years, the diving here is quite different.
On a recreational dive you are schooled to slow down, relax, don’t exert yourself. Here, the dives last about 40 minutes with 28 of those minutes consisting of active swimming. Two divers go down. One navigates a square while the other searches for conch. I’ve never been able to stretch out a tank full of air in relaxed recreational diving and with these dives, because of the exertion; it is a challenge for me to simply get to the anchor again before I begin to run low on air. However, they are working around my limitations and I’m really enjoying the dives.
Today, however, I won’t be diving, I will again don the snorkel, mask, and fins and we will go looking for conch in shallow areas. Once we locate the conch we will free dive and try and find individuals that fit the size range we need for our study.
Our two-week adventure is drawing to a close and it has been great. The weather has been very good, the diving fun, and the people I’m working around fantastic. All things come full circle and today, years after playing out my dreams in the pool, I’ll grab my snorkel and fins and live those dreams of diving in the clear, warm waters of the Bahamas.
Over the past few weeks we’ve seen lots of queen conch. We’ve spent what amounts to days and days in the water and covered miles (or kilometers) of seabed in search of these animals. Each day the crew from the dive boat and the crew from the tow boat compare notes. Where did you go? How many did you see? How big? Any mating? Eggs? How old were they?
After listening to these daily reports and seeing hundreds of conch myself, I am amazed by the variety of shell sizes and shapes within the species, Strombus gigas. This variety is likely due to a combination of genetics, the kind of the habitat the conch is living in, and the age of the animal. In a previous post I briefly talked about the differences between juveniles, rollers, and adults (a little more on that soon), but for this post I am really talking about the adults.
Here in Warderick Wells the dive crew is finding a lot of older conchs in the deeper waters we are exploring. Most of the old conchs we find have shells that are very rounded and have long since lost the beautiful pale pink on the outside of their shells. They are extremely heavy because of the layers and layers of calcium carbonate shell the animal has built up over the years. The younger conchs the towing crew finds generally have a much more delicate appearance because their shell has not been worn down over time and the beautiful hues of pinks still stand out. So, age does obviously make a difference in the appearance of the conch.
All animals are shaped by their environment, and the queen conch is no different. The appearance of a conch shell is very influenced by the biological environment it lives in. Fishermen know that a conch’s shell tends to take on certain characteristics of its habitat and are not fooled by this “disguise”. Our towing team has had a great time trying to spot conchs disguised by lots of algae growing on their shell that resemble little “Chia pets”, or “rasta conchs” (depending on who you ask). These guys blend into their habitat really well! Towards the end of a conch’s life the thick shell has almost certainly become a little ecosystem itself. We’ve seen many different species of algae, some corals, and boring worms in the oldest shells.
Another reason for such great variety in the conchs we have seen may have to do with their genetic “flexibility”, or what scientists call phenotypic plasticity. Most immobile (or less mobile) animals can change the way their genes are expressed based on the habitat they live in. Scientists think that depending on the habitat (the physical environment and the food that is available), a conch’s shell might actually form differently in size and even in shape. After all, the better adapted they are, the more likely they are to survive!
We have also been finding a lot of a small variety of conch we call “sambas”. They are like miniature versions of the big broad-lipped queen conch that usually represents the species. The samba adults are still recognized by the flared lip, but it is not as big and beautiful. We do not know what exactly causes these conchs to grow smaller (type of food, availability of food, water quality, genetics?), but scientific investigations have indicated they may be genetically different than the normal sized queen conch.
In the end, we don’t mind what they look like; they all get counted as queen conch. However, from what we have heard, fishermen do care what a conch looks like. The small samba conchs are harder to get out of the shell and the meat is tougher, so they are often skipped over. The really old conchs may be passed up too for the same reason. The large conchs with the broad shell lips are tastier and you get more return ($) for your effort. Is this preference by fishermen (what scientists call selective fishing pressure) having an affect on the overall fishery? If only the sambas are left to reproduce, is that what we can expect to see more of in the future? From what we saw in the Berry Islands and Andros, this could be happening already.
Thanks for checking in…
Well everyone, at this early stage no real conclusions can be drawn about what we’re going to find in the deeper depths here in the Exuma Cays Land and Sea Park, but so far, we have found more queen conch on one transect than we did on all the transects we did (40) at Lee Stocking Island! We’ve also observed more mating and egg masses as well, which means more reproduction too. More conchs! More reproduction! Could the Park be living up to its reputation?
Our new volunteers are a great bunch of people. Andy and Ted were with us in the Berry Islands in 2009, and Peyton and Jasmine have joined us for the first time. And of course, we still have Adric with us. So, we’re getting everyone trained in the field, and just starting to get into our daily work rhythm. Stayed tuned for posts from the volunteers’ perspectives on the project and the Exuma Cays Land and Sea Park!
Thanks for checking in…
After sailing steadily up the Exuma Cays chain, we have made it to the Exuma Cays Land and Sea Park! This no take marine reserve has been protected since 1986 years and is known as the oldest Park of its kind in the world. Diving and snorkeling here is like going back in time. The marine life is truly amazing and unlike anything you might see throughout the rest of the Caribbean. A few of us took a quick snorkel yesterday and immediately noticed the difference. Quite simply, there are a lot more fish. There are a lot more different species of fish. The fish are bigger and they seem uninterested in your presence. They continue with their daily fish lives, displaying typical fish behaviors as you watch (as opposed to diving for cover as soon as you get too close). On our snorkel we saw a large coral head with 10 lobsters hiding beneath it. We saw juvenile and roller conchs. We saw large predatory fish and lots of big parrotfish grazing away. It really is a special place.
Scientists have been documenting the uniqueness of such a well-preserved ecosystem and the benefits it can have for fisheries conservation for many years. Scientific studies have shown that Nassau grouper biomass (a measure that captures both the number and size of a particular organism) inside the Park is much greater than outside of the Park, and that rates of parrotfish grazing (an important ecological process that keeps reefs healthy) are much higher in the Park (Mumby et al. 2006). Recently, scientists have found that in the Park there are fewer lionfish (an invasive species) on reefs where there is high grouper biomass. In places outside of the Park where grouper populations have been depleted, there are more lionfish, so it seems having more large grouper may help control this invasive species (Mumby et al. 2011). About 20 years ago, Dr. Allan Stoner and colleagues found that the density of conch (the number of individuals per area) in the Park is 31 times greater than densities on the fishing grounds around Lee Stocking Island (Stoner and Ray 1996). And that is, of course, why we are here today; to determine if those conch densities are still really high here in the Exuma Cays Land and Sea Park.
On our way here, we stopped by the settlements of Little Farmers Cay and Black Point to talk to fishermen about their experiences in our study areas. We had a good conversation with fishermen on Little Farmers Cay about the conching grounds around Lee Stocking, and enjoyed a delicious conch dinner from one of the local take-away restaurants. At Black Point I was able to make some good contacts for a future meeting with the fishermen there. People found it very amusing that we were headed to the Exuma Cays Land and Sea Park to count conch. They told me we were going to get tired of counting conch because there are SO MANY in the Park! They also warned us that we might see sharks…I told them I hoped so!
Until next time…
Well, we have said goodbye to 3 of our volunteers for the Lee Stocking Island leg of the trip and are heading north today. We really, really appreciate the time and dedication Jamie, Karl, and Alannah gave us while here. They did a great job! We got our work done and managed to have some fun doing it. Here are a few pictures of the crew…thanks guys!
Next we are going to Little Farmers Cay, which is about 15 miles north of Lee Stocking. No surveying there, but we will meet with some fishermen to talk conch. After that we will keep traveling up the Exuma Cays to Black Point, and then Staniel Cay. We hope to meet with some folks there too.
More posts are on the way, so be sure to check back again soon!