Hikianalia Science Update | April 24, 2015
The Polynesian voyaging canoe Hikianalia is on a 2,400 mile return journey from Aotearoa to Hawaii. Crewmembers will be sending frequent updates so that educators and students can track her progress in conjunction with the Worldwide Voyage Tracking Map.
We have been sailing north-east into warmer waters. The water surface temperature has been around 23ºC (73ºF) for the last couple days, much warmer than the 18ºC (64ºF) in Auckland, New Zealand. The windy conditions have landed us many malolo (flying fish) on deck, especially at night. Most of the catch is 10-20 centimeters (cm, 4-8 inches) in length, but one was a little juvenile of only 1 cm (0.4 inches). We usually return them right back into the ocean.
The most exciting events in the last few days have been the capture of two mahimahi. The first one was a male of 120 cm length that we caught two days ago. As with every fish we catch, we collected a small part of its fin and preserve it in a little tube for future DNA analysis. We also inspect stomach contents: the stomach of our first mahimahi contained two fish and six blue jelly-like discs. The fish were still in pretty good condition, but we are not sure what they are. The smaller one was beige and rhomboid in shape and looked like a triggerfish. The skin was very rough and scaly, resembling sand paper. The larger one was very long and eel-like with thin blue-silver skin, possibly related to the ribbon fish.
The blue jelly-like discs are actually colonies of hydroid polyps, similar to Portuguese man-of-war. Each has a blue disk that floats on the surface of the water with a transparent half disc sticking up perpendicular of it that serves as a sail. The sail is reflected in its Latin name Velella velella, meaning something like little sail. At the bottom of the little blue discs are attached many little bright blue polyps, similar to coral polyps. Each polyp has tentacles equipped with stinging cells (also called nematocysts) used to catch prey floating by such as zooplankton. Those little sailing colonies occur throughout the worldʻs oceans.
Today we caught the second mahimahi, a female of 114cm length and a very full stomach containing lots of those same triggerfish-like fish, a few already well digested malolo and some parasites. We preserved the parasites and a fin clip of the triggerfish for possible future DNA analysis and also looked at the stomach contents of two of them. We found lots of tiny crab claw and legs in them, suggesting they feed on benthic organisms in coastal areas or on the bottom of the ocean, which is probably also where they live. Who knows where the mahimahi ate those little triggerfish?