With a few hours to spare before catching my return flight, we did one last survey of the Islas Paridas, but only sighted one group of bottlenose dolphins. Once inside the estuary we observed two more groups.
This wraps up our expedition. In all, we surveyed for 12 days, covered 1034 km, had 1 visual sighting of humpback whales and had 4 acoustic encounters with singers. It has been 15 years since we first surveyed these waters in the boreal season in 2001-2003, with similarly low encounter rates, suggesting there hasn't been an appreciable increase of the population using the Gulf of Chiriqui (unlike the population using this area during the austral season, which is increasing in leaps and bounds). We will prepare a report for presentation at the next Scientific Committee meeting of the International Whaling Commission, as part of the ongoing assessment of North Pacific humpback whale populations.
Our research in Panama is conducted under MiAmbiente permit SE/A-79-17. Islas Secas Resort provided logistical support.
Day Twelve, March 5, Bonus day two — a trip to Islas Contreras, Montijano wind, two elusive whales, and bottlenose dolphins
Our last full day of the expedition was spent surveying the small island group to the east of Islas Secas known as Islas Contreras. On our way there (under a head wind locally known as “Montijano”) we spotted two whales traveling together, keeping a low profile. We slowly approached them as we observed them for a surfacing interval. However, we were unable to relocate them, and because we didn’t get good looks we had to record them as “species unidentified”. Nearly simultaneously, we spotted a small group of bottlenose dolphins in the area that appeared to be of the “oceanic ecotype”. These dolphins were quite large and darker in color than the coastal group.
We had planned for 10 days of survey to account for bad weather days. But conditions have been so good that we’re hoping to continue surveying until the last possible minute (11 am on Tuesday).
In the absence of whales today, and to keep ourselves motivated, we decided to capture a couple of video clips of abundant gelatinous zooplankton that we encountered during our hydrophone dipping stations. We’re curious to receive species identifications from among our expert colleagues.
Day Ten, March 3, The land-sea breeze, a loud male singer in rough seas, and a trip to Islas Paridas
We are fortunate that the Gulf of Chiriquí is situated in a wind shadow while the Gulf of Panama to the east and the gulfs of Papagayo and Tehuantepec to the west endure sustained strong winds this time of the year.
Chiriquí is located in a shadow of relative calm, while the gulfs of Panama to the east and Papagayo to the west endure sustained “gap winds” crossing from the Caribbean through mountain gaps this time of the year. Image from https://earth.nullschool.net/#current/wind/surface/level/orthographic=-82.62,6.44,2242/loc=-82.312,8.192
However, the high pressure that dominates over Central America this time of year means that a local land-sea breeze develops twice a day very predictably. Like clockwork every morning around 7:30 am we get a breeze from land and around 3:00 pm we get an ocean breeze. This morning the breeze got a little intense while we were on transit to the the Islas Paridas for a survey there so we thought we were going to have to abandon that plan and return to the Secas. But not before doing an acoustic station with our hydrophone. As luck would have it, the song of a male humpback whale came very loudly through our earphones (it probably was within a few hundred meters from us). With a mix of excitement and disappointment (as we knew we would not be able to do much work with this whale in rough seas) we sat still, waiting for it to come to the surface so that we could at least catch a glimpse. But it stopped singing and we were unable to locate it visually at the surface among the white caps, so after about 45 min we decided to move on.
But by then the breeze had quieted down and Chanin, our captain, decided we could resume our original plan to survey the Paridas. We plied these waters in excellent weather conditions but without sign of humpback whales.
Today we surveyed the southern margin of our study area around Islas Secas. No humpback whales were seen or heard on the hydrophone. But we received notification from a sports fishing vessel that they had seen them yesterday at Islas Paridas, so that’s where we’re going tomorrow.
We’ve been having excellent weather and we have seen lots of groups of pantropical spotted dolphins during the expedition. They are by far the most common species of cetacean in the Gulf of Chiriquí. We often see them in association with logs and sticks, as they attract small fishes, so the dolphins use them like floating restaurants. Or at least cafés.
We usually take a 15 min break from surveying to eat our sandwich for lunch, while we drift with the engine off to enjoy a moment of quiet. During lunch break today, a pair of spotted dolphins approached us very cautiously. Probably thinking our research vessel Chiripanga was a very big log, they came over to inspect it. Interestingly, only the larger animal in the pair came close, and when the smaller one tried to get close, the larger one pushed it away. We’re guessing this was a mother and her calf and that she was being protective of it. Some days the highlight is the entertainment provided by a momentary lunchtime visitor, be it a yellow-bellied sea snake or an inquisitive dolphin. We’ll gladly take what we get.
Day Eight, March 1, Looking for whales at very low densities, and grateful for hydrophones — our ears in the water
Unlike what some people might imagine our work entails, it is not uncommon for us to spend up to 99% of our time looking at just water. Such days can be tough, as we must remain in full concentration scanning the horizon in order to conduct a rigorous survey.
Fortunately, the Gulf of Chiriquí and its many island groups offer gorgeous vistas of unspoiled nature. And when whales are in very low densities, as is the case in this expedition, we have a secret weapon: the hydrophone.
At the end of a very long day on the water today we were rewarded with humpback whale song coming out of our earphones during the last listening station. We implemented a trial-and-error search pattern for about an hour and a half to locate the lone singer. Ultimately we were unsuccessful in locating him before we had to return home, but in the process we learned a little bit about the range of our hydrophone as well as about how to go about conducting such searches in the future.
We can always hope for visual detections in coming days, but every record of presence is a small victory in this project, and after a few days without whales we were excited to hear them again!
Day Seven, February 28, Low, low tides, and a trip to Islas Contreras — Kingdom of the Bryde’s Whale
This morning we got a little complacent about an early departure, and our trusty research vessel Chiripanga got stuck inside the bay due to the extreme low tides associated with the full moon this time of the month. Since we couldn’t cross the reef, I figured at least I could snorkel it for about an hour until the tide started to come back. I was rewarded with a myriad of beautiful coral reef fishes, and at some point I even had a hawksbill sea turtle AND a much bigger olive Ridley sea turtle swimming together side by side. Where was the GoPro to prove it?!
Our survey today took us to the Islas Contreras, another nearby cluster of islands that harbors great humpback whale densities during the austral season. Today it was empty of humpbacks. We did briefly catch a glimpse of a juvenile whale shark near the surface, and even though we had the GoPro ready this time, it dove quickly as we approached it.
But humpbacks are not the only large whale species that can be found in these waters. Our research in previous years has shown that Contreras is a hotspot for Bryde’s whales, and today it proved itself again: about half way between Secas and Contreras we encountered a pair of Bryde’s whales. Typical for the species, they were rather elusive and we were not able to get close. But at least they kept our skills fresh until we encounter some humpbacks.
We have a network of informants among the fishers and other mariners in the Gulf, and even though we haven’t encountered humpbacks lately, we keep getting reports of others seeing them here and there. So the search continues.
The green circles show the concentration of Bryde’s whale sightings at the Contreras from a previous survey. The figure is from: Rasmussen, K. and D.M. Palacios. 2015. Update on humpback whale research in the Gulf of Chiriqui, western Panama, 2014. Paper SC/66a/SH/16 presented to the IWC Scientific Committee Annual Meeting, May 2015, San Diego, USA. 8pp.https://archive.iwc.int/?r=5500&k=eaf1442d5e
Today we extended our search to the Paridas island group, to the west of our home base at the Islas Secas. Despite excellent weather conditions we had no visual or acoustic encounters. Given the low population size of this group of humpbacks, we are fully expecting very low densities here at the southern extreme of the breeding ground in the Gulf of Chiriquí. So the search goes on.
We are encouraged that our colleagues further to the north are also conducting similar research, including Jose David Palacios Alfaro (Costa Rica), Ester Quintana (Guatemala), and Oscar Frey (Mexico), among several others. We look forward to similar coordinated efforts in future years.
Again, we encountered false killer whales today! This is a rather rare species and it's always a treat to observe their complex behavior and social structure in the wild. Through photographs of the distinctive markings along the trailing edge of the dorsal fin, we were able to determine this was the same group we encountered two days ago. Today we got to photo-ID a few more individuals in the group, and to document the presence of several juveniles.
Also, during the previous encounter, we collected three biopsy samples from this group, and today were able to photo-document the evolution of the biopsy tip wound over the course of two days for one of the animals, showing remarkable healing.
In the process of examining the distinctive markings on the dorsal find and caudal peduncle of these animals, we noticed the unmistakable sign of interactions with fishing gear.
This is a global problem and occurs because this intelligent species has figured out how to steal the catch from hooks set by fishermen. Our captain for this trip, Chanin Bernal, a life-long fisherman in these waters, tells us that artisanal tuna fishermen here in Panama sometimes pull the hooks with only fish heads attached, as the bodies have been snagged by the "pilotos" (the local name for false killer whales and related "blackfish").
Aside from the disfigurement, the problem is that some whales may be getting caught in the hooks or otherwise becoming entangled in the fishing gear, and getting seriously injured or dying
at rates that put local populations at risk (see for example: http://www.fpir.noaa.gov/PRD/prd_false_killer_whale.html).
Tuna and other large predatory fish are economically important for the sports and artisanal fisheries of Panama, and it is evident more work is needed by biologists, managers, and policy makers to solve this global problem that goes largely unnoticed.
Our friends Linda and Jim offered us the opportunity to survey the waters between the Secas and Coiba, an island at the eastern end of the Gulf of Chiriquí, from their larger boat Minerva, and we jumped at the opportunity, as we rarely get to access that area. We had great visual survey conditions and made a few stops to listen for whales, but we didn't encounter any...
...Until we were on the island. Coiba is a national park and its visitor center features the skeleton of a humpback whale and the skull of a Cuvier's beaked whale.