Saturday, June 20, 2015

Another trip to Trinidad

Scarlet Ibis returning from Venezuela

I have just returned from Trinidad (the country, not the city in Colorado) with Cameron Ghalambor, Craig Marshall (a new PhD student), and Travis Klee (a new Bachelor of Science). Unfortunately, we didn't have internet so I couldn't post about the trip as it happened, so instead, I will have try my best to recall the details and events.

Cameron and Craig arrived in Trinidad on June 10, after almost missing their flight from Denver, being delayed in Houston for about 4 hours, and arriving in Trinidad after the rental car place had closed. The next day, the plan was for them to obtain permits, scope out field sites, and purchase some groceries before Travis and I arrived in the evening. They were mostly successful except in regards to the permits (they arrived at the permit office at 3:40 only to be told they closed at 4 and were currently closed, welcome to "Trini time"). At least they managed to track down a rental car by the time Travis and I arrived at 10:30. We also had delays in Houston because the pilot couldn't get one of the engines to start (kind of a big deal!), but we did manage to get upgraded to the front bulkhead row and got free TV. Other than the delay, we made it to the field station with relatively little trouble.

The Reznick guppy facility near Arima, Trinidad

The plan for collections was to get three guppy species from a range of salinities for Cameron and Craig (Poecilia vivipara brackish, P. picta brackish, P. picta fresh, P. reticulata fresh) and 2 high predation/low predation pairs of P. reticulata for me. We started by collecting the brackish fish at a boat dock in the Caroni Swamp on the western side of the island.  We were very successful at collecting fish, but the vivipara turned out to be more difficult to catch with our butterfly nets than we anticipated.  We also tried seining but our net was small and we didn't catch any guppies (though we did catch other things, like eel/leptocephalus larvae). We also managed to find a site close to the boat ramp that was freshwater and were able to sample the freshwater picta. They were densely concentrated under the vegetation along the shore, which made sampling go very quickly. This is ideal since we don't like keeping the guppies in the transport bottles longer than necessary.

The boat canal in the Caroni Swamp
Cameron (left) and Craig (right) catching guppies
Cameron sorting guppies into bottles to be
transported back to the lab

The swamp is about an hour drive from the lab, so unfortunately we had some mortality when we got back.  But being scientists, we took this as a learning opportunity to try to verify the species we caught and distinguish vivipara and picta females.  Because guppies are small, sometimes it is easier to tell these differences on a fish that isn't swimming around.

Craig and Cameron sorting guppies
Examples of some of the fish from the Caroni swamp.
Male picta were obvious and are grouped on the right.
The middle column is most likely picta females, with the
exception of the first two, which are viviparafemale and male.

The next day we headed to the north slope of the mountain range to collect some freshwater reticulata from HP and LP sites.  We stopped quickly at one of the beaches along the Caribbean Sea then headed to our sites on the Yarra River. We sampled the HP site first, and saw lots of other cool fauna, including a large cichlid guarding its young, shrimp, and schools of characins (look like large tetras). Then we headed back up the Blanchisseuse Road (not for those with sensitive stomachs) to the Yarra LP site, which took some exploring to find the dirt road leading down to the river.  When we got there, we were greeted by a group of about 5 guys with a dead goat tied to a tree that was in the process of being butchered.  I couldn't make this up if I tried. They were very cordial though and had no problem with us collecting guppies upstream from them.  They did try to help by telling Cameron about some "big fish" near where they were working, and when Cameron asked if there was blood in the water, the response was "I just killed a goat". We did not sample there.

Las Cuevas Beach
Sampling the Yarra HP site
Sampling the Yarra LP site

We were very fortunate in that the rain held out most of the time we were sampling, so the next day we headed to the Aripo River on the south slope, which drains into the Caroni Swamp eventually.  We sampled a LP site that is also referred to as the Naranjo River.  Though this site has traditionally been sampled extensively, we found a healthy population. However, we did make sure to only remove a small number of individuals from each pool. We found a lot of killifish (Rivulus/Anablepsoides hartii) at this site as well, which only prey on juvenile guppies and are considered a minor predator. On the way home, we also stopped by the site of the Endler LP introduction about 40 years ago.  Again we found a healthy population that could potentially be a site for future studies.

The Naranjo/Aripo River LP site
Looking upstream
Killifish, Rivulus/Anablepsoides hartii back at the lab

After taking the fish back to the lab, we headed back out to the Caroni River again, this time further upstream so I could catch some freshwater reticulata from an HP site to pair with the Aripo LP site. We checked a site that I had sampled the last time we were in Trinidad.  However, that time was in the wet season and the river was difficult to sample so we were left with sampling one of the drainage ditches nearby.  These fish ended up being very unhealthy so not many survived when we returned to Colorado.  This time, however, we were able to sample the river.  The population wasn't as high density as the one near the swamp that we sampled a few days previously, so it ended up being the site that took the longest amount of time to finish, but it was still only about an hour. We had to be quick because just upstream someone was cutting down bamboo stands and were getting closer and closer to us and we didn't want them to fall on us.

Cameron looking for guppies in the Caroni River

Cameron and Craig also needed some freshwater reticulata since their previous freshwater site ended up being about 90% picta, so we went searching for a nearby site they could use.  We ended up near a road crossing in a popular spot for "liming" (aka, partying). Once we located a good vegetation patch with lots of adults hiding in it, it only took a few tries to get all the guppies we needed.  However, in the meantime, Cameron managed to find a fire ant colony that apparently he was sitting on.  He was a trooper because he brushed them off and continued sampling guppies. At this point, we had now collected everything we were targeting, which is pretty good for only 3 days!

Sorting guppies on the Caroni River (post fire ant attack)
Travis and some guppies caught at the Caroni HP sites

After a hard day of exploring, collecting, and fire ant attacks, we decided not to cook dinner, but to instead go out for some Trini street food called doubles.  They're sort of like a taco, with two pieces of bread overlapped on the bottom, then doused with a chickpea sauce and potentially other sauces.  If you're brave, you can ask for "plenty peppa".  I was not brave but the guys were. Each doubles stand is unique and we found some that serve them with other ingredients like ground chicken or a mango sauce.

Eating doubles
Looks like what you might
see in a baby diaper

Cameron had to head back to Colorado the next morning but the rest of us stayed another 2 days.  We used this time to try to catch some pike cichlids (Crenicichla frenata).  These fish are piscivorous and are one of the main predators of guppies in the HP sites.  We needed to catch a few to bring back to Colorado so we can use them for a "predator" treatment in the flow-through systems. We were told the best way to catch these is using hook and line with guppies as bait, so we headed to a few HP stream sites to see what we could do.

The morning started with a downpour and was the official start of the rainy season. We weren't able to get out for the first few hours, but once it cleared up we headed out to the El Cedro River.  We got (vague) directions to the site from a few people, with the warning "DO NOT go to the dump".  Apparently this is where very desperate people live and will attack people looking for anything they think will be valuable to them.  We thought we were going the right way, then saw a man in an orange vest that looked like he was checking in cars at a gate.  Immediately I realized it was the dump, so we had to turn around quickly and head back.  We eventually found the river in what looked like someone's driveway, but after poking around for about 20 minutes, we didn't see much of anything, including guppies.

The El Cedro River

Next, we headed to an Aripo HP site to try again for pikes.  We had to do a little more exploring to find the trail leading down to the river, but eventually found it.  It was kind of fun to actually do more of a hike to get to a site, rather than just pulling over on the side of the road.  This was the first site where I expected to see a fer-de-lance or bushmaster, the two venomous snakes found on the island, but we didn't see any. I guess that's actually a good thing. The river was beautiful when we got to it, and we had a clear view of the waterfall separating the HP and LP sites (predators have a difficult time scaling these, but somehow guppies and killifish can do it). Not long after we arrived at the site, we were overtaken by some kind of flying insect.  They didn't bite, but it was annoying because it made it difficult to concentrate on trying to fish.  I even had one fly into my eye.  When we got back to the house that evening, we learned that the rain earlier in the morning caused the termites to emerge.  We did see a lot of other fish at the site, mostly the larger Characins, but were unsuccessful at catching a pike.

Aripo River and waterfall
The rains brought out a lot of amphibians, and we decided that evening to go on a herp walk to see what we could find.  We probably saw at least 5 species, including ones that were inflated floating in a puddle.  We also saw some cane toads and some other frogs that we weren't sure exactly what they were.

The next (and last) day we tried for pikes again in the Oropuche River.  In contrast to all the other sites we had been to, this river drains to the Niriva Swamp in the east. We tried for a while and were unsuccessful at catching anything using our guppy bait.  This site is also a popular liming spot, so one of the locals came over to help us.  He suggested using some crackers (which he donated to us) to draw the small fish in, and the big fish will follow.  While this seemed like a great suggestion, the river was flowing a little too fast for this to work well.  However, Travis managed to figure out a way to bait the smaller characins and scoop them up with one of the butterfly nets.  Then we were able to use these for bait, which were much bigger than the guppies. After about 2 hours of trying, we had several bites, but were unsuccessful at catching anything. Then we met another local who actually collects fish and works for the zoo in Port of Spain.  He told us they catch them using a seine that spans the width of the river. We didn't have one that big, but we did try walking upstream a bit to find one of the spots he suggested.  We never did catch any pikes.  Fortunately, one of the other researchers went out to El Cedro for killifish that night and was able to net one for us while it was sleeping, so we were able to bring one back in the end.

Travis and Craig fishing for Pike

Me fishing for pike

Marianne, the pike cichlid

We wanted to make sure we did one thing for fun while we were in Trinidad, so the last evening we took a boat tour of the Caroni Swamp to watch the scarlet ibis return to their roost after foraging in Venezuela for the day. We saw lots of other wildlife too!  I'm really glad we had a chance to get out in the swamp a bit.

Me, Travis, and Craig

Four-eyed fish, Anableps

Tree boa

Silky anteater
Scarlet ibis

So in all, I would say it was a very productive trip.  Only about 5% of our fish died on the flight back to Colorado, and all are looking healthy and happy in the lab. Now I have no excuses, time to collect some data!