A salty desert

Lab Note #4
Apr 21, 2014
At least for humpbacks. The migration of northern pacific whales to costa rica has been very, very small this year. While this has put a big damper on my goals, I have been plugging away in the waters between Drake Bay and Caño Island. Many days, I have seen no whales at all, but I wanted to revisit the map I posted in my previous post, since there were questions about what it was meant to show.    

Back in March, I had a day with two mother-calf pairs. The image below shows the route we took that day, and it is standard for us. A slow passage out to the Island, followed by a passage, either along its northern or southern side. Next we head to San Pedrillo, the southernmost extent of my study area before following the coast past San Josecito back to the Bay.  

The encounters with both groups were very brief, and the second did not afford an opportunity to photograph the animals before we lost them. First we encountered a group of spotted dolphins. As we observed them, we reoriented the vessel several times, and this changing perspective allowed us to sight this mother-calf pair. Our timing was just right, and we saw their backs rolling up just as a swell peaked off our bow. I marked a couple of puka positions before this pair eluded us. “Puka”, I should say, is a Hawai’ian word meaning “hole”.  The term is commonly used by whale researchers and watchers there to describe the calm spot of water that appears when a whale flexes her fluke as she dives. This generates a great deal of turbulence, and the glassy spot is readily distinguished from the surrounding waters. So finding the whales’ last location can be pretty easy. However, as is common with humpbacks in this region, the adult did not fluke during this encounter; as flukes are necessary for identifying individuals, this encounter ended without collecting that critical datum.  

Our second sighting was made where were conditions were a little more favorable. Humpback blows have a characteristic heart-shape, but can be hard to spot at a distance if the horizon is hazy. A clear, blue horizon allowed me to spot this pair at a distance of about 2 kilometers! We immediately made our way over, as you can see from our trajectory. The animals were in travel-mode, however, and we only observed them for a couple of breaths before we lost them in choppy water. Again, we did not see flukes. This pair was sighted quite a distance from our first encounter, but without photographic evidence, it’s impossible to say with certainty whether they are the same pair, or a different group.  

Another upside of 3/14/2014, however, was really clear conditions at San Josecito beach. This is a popular spot for Caño Island snorkeling trips. Caño Island is a National Park, with strict limitations: 150 per day ($10 entry for extranjeros), and two possible 4-hour windows for visiting – 7am-11am and 11am-3pm. So the morning trips often make their way back to Drake Bay via San Josecito Beach when their 11 o’clock window closes. The shallow bay is blocked in on north and south by rocky outcroppings, each of which are lined with substantial coral beds. There’s much healthy coral to see there, though there is plenty of evidence of anthropogenic disturbance. All the broken coral does make one appreciate the restrictions of Caño: every snorkeler must wear a flotation device, which effectively keeps one off the coral. San Josecito is mostly less than 2-3 meters deep, and so it’s easy to access the good stuff. On the other hand, it’s hard by the beach, and so can be quite sandy.

The 14th, however, was a clear water day, so Joy and I enjoyed a nice little swim. Overall, San Josecito capped a great day with two encounters, and helped dampen my disappointment over a reasonably diverse set of fish gracing the coral heads. I will describe the snorkeling and Caño Island in an upcoming note!
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