So now that we’re back from the field what to do with all the data that we collected. Well the first obvious step is to transfer the data from the many data sheets we used in the field to spreadsheets so we can actually use that data in our future analyses. But that’s not terribly exciting so lets just leave it at this: after a couple of days of tirelessly entering data into excel sheets we finished and now its time to start analysing it!
The first thing we decided to look at is changes in recruitment. As you might remember from my last post recruitment is when a fish metamorphoses from its larval phase (usually floating around on the ocean currents) to a recognizable juvenile form on the reef. Our dataset now includes 2002-2004 (pre-lionfish) and 2013 (post-lionfish). So while we won’t be able to say with absolute certainty that any changes we observe are due to lionfish; we can say that lionfish are a prime candidate for any shifts in the fish community structure. Other potential candidates are things like hurricanes and coastal development. To my mind lionfish are really the number one candidate because the time post hurricane before the 2002 surveys is about the same as the time post hurricane before this years surveys so you would expect the populations to have changed in a similar manner. Coastal development is unlikely to be much of a factor because Turneffe is still for the most part undeveloped. There have been a couple additions (a Coast Guard base next to the field station for one) but for the most part from what I’ve heard not much has changed, its not like a big town or resort complex suddenly showed up.
So without further ado here is a very rough graph of what our data looks like!
I know its pretty rough and complicated (I’m just learning how to code in R and haven’t really figured it out enough to make it do what I want completely!) but still you can get some pretty cool info out of it. Basically the the circles represent where all of the different survey years cluster towards as far as species composition (the purple four letter codes represent species so HAGA = Halachoeres garnoti or the Yellowhead wrasse). The small circles are each individual site coloured to match the year. So looking at this you can see that CHCY, the fish formerly known as the Blue Chromis, is negatively correlated with the 2013 data since its very far away from that circle. HAGA on the other hand is positively correlated to the 2013 data etc. So looking at this we can see that the three survey years before the lionfish invasion (black, red and green for 2002, 2003 and 2004 respectively) all have very similar fish community structure where as the new 2013 data has a somewhat different community structure.
So yeah cool stuff right! I haven’t even begun to figure out what all of that could mean in terms of what’s going on with the fish communities, or why some fish are positively and other negatively correlated to lionfish. But this is definitely a cool start to what will continue to be an interesting story to pull apart in the future.