As I’ve said before, we were very lucky to have a great group of volunteers again this year. People came from a variety of backgrounds and places, and so all had their own unique impressions of The Bahamas and the studies we are doing. Adric Olson was our only volunteer who stayed for the duration (full five weeks) of the trip. He counted a lot of conch and spent lots of time in the water at both the Lee Stocking Island study site and the Warderick Wells site. Adric was a great person to have around because of his positive attitude and sense of humor. He has the observation skills of a scientist, and always had a good question or suggestion. Here is Adric’s unique perspective…and our attempt to explain some of the finer points of fishery conservation science….
I would be remiss if I didn’t start my blog post by thanking those who made this trip possible for me. It has been a great experience and so I’d like to say thanks to Community Conch and the staffs at both the Perry Institute for Marine Science and the Exuma Cays Land and Sea Park, in addition to those who provided funding for the trip.
As I am one of the few people who was lucky enough to participate in the field work for the entire 5-week duration, I have a unique perspective on the quality and quantity of queen conch stocks in the Exumas. As you may have read, the number of conchs we found around Lee Stocking Island is small enough to be troubling, particularly in the deeper waters. This depletion is even more troubling when the numbers are compared with those reported by Dr. Alan Stoner’s from his studies done in 1991 (Stoner and Ray, 1996). (I’m sure this will be discussed in a much more scientific manner in the paper that will be published as a result of our work, so I will try to avoid mentioning specifics here). Although we did find a lot more conchs in the shallower areas around the Lee Stocking study area, they were very young which further compounded our concern. Although this may seem like a positive sign for the future of the conch, the reality may be much bleaker. A large amount of scientific research has shown that fishing pressures can drive the average size and age of commercially harvested species so that stocks become both smaller and younger, followed by a collapse of even the most expansive stocks (See: Beluga Sturgeon, Atlantic Cod, and queen conch in other countries of the Caribbean!).
The good news it that we saw a lot more queen conchs in the Exuma Cays Land and Sea Park than we did around Lee Stocking Island. The density of conchs (the number of conchs per hectare) was much greater, which is a good sign. Scientists are interested in measuring density within a population because generally, the more conchs there are in an area, the greater chance they have of finding each other and reproducing. And the larger the population (or number of individuals), the more likely it is that density will also be greater. But to have a proper discussion about the conch stocks in the Exuma Cays Land and Sea Park, a basic understanding of source-sink and meta-population dynamics is necessary.
Metapopulations come into play in fisheries when population groups (often called sub-populations) of a species are separated and small, so that the possibility of individuals from different populations finding each other and reproducing is virtually eliminated. In the case of the queen conch and other organisms that do not move long distances, the bigger the population and greater the density, the better chance individuals within the population have of finding each other and mating. A good way to visualize this to think about a somewhat cloudy day, where there are lots of distinct clouds in the sky but none of them touch any of the others. Just like the distinct populations found in a metapopulation model, some clouds are bigger than others and some are closer together. In nature, individuals, and therefore genes, can travel between these population “clouds”, depending on proximity, ease of travel, and other factors. This type of model applies for any number of organisms (even humans – North America and Europe are connected by airplanes and boats but the vast majority of those on either continent tend to stay and reproduce on that continent). Source-sink dynamics refer to the exchange between populations. Trouble can occur when one of the clouds is not able to sustain a population without an influx of individuals from another population. This unsustainable area or population is called a sink. The population or populations sustaining it are called sources. The smaller and further apart populations are, the less likely that this necessary exchange will occur.
Now, how does this pertain to the Land and Sea Park? The expectation is that marine reserves in general will act as sources that support populations outside of the area, but also, hopefully, sustain themselves. If a reserve like the Land and Sea Park is acting as a sink and cannot sustain itself, this could spell doom for populations (like populations of the queen conch) within that reserve if the source populations necessary to sustain it are destroyed. This is why scientists believe that a network of marine reserves is a better management approach, so that there will always be some populations large enough and close enough together so that exchange can occur. So is the Land and Sea Park a source or a sink? Is it sustaining itself? This is a complicated question which can have different answers depending on the species you are considering. Currents in the area and the duration of the larval phase of a species life cycle are important. As for the queen conch, we have some clues based on the population structure inside the Park. Look for our assessment in our next report!
- Adric observes a trio of conchs. photo by C. Booker
I’m going to conclude my post by saying nice things about the Bahamas, because I really enjoyed my time there. Almost every Bahamanian I met was exceptionally friendly, to the point that I felt they would oblige me if I needed the shirt off their back. On one notable occasion, I got to go to Big D’s on Great Exuma, where Big D made us the most photogenic conch salad I’ve ever seen (yes, sustainably caught!) and then chatted us up all night. Big D is a big supporter of queen conch conservation. He knows his business depends on it.
The scenery in the Bahamas was beautiful and the number of mostly undeveloped islands could yield an infinite number of postcard-perfect sights. The Exuma Cays Land and Sea Park was beautiful and I was blown away by the large number of sharks and fish, large and small. The majority of fauna in the Park was flourishing and the only shame is that the other parts of The Bahamas I saw during this trip didn’t look the same way. The Bahamas are a fantastic country with untold treasures and I just hope they are able to make the few changes necessary to preserve their beauty so I can share them with my children someday.