Day two of fieldwork here we go! What an amazing day we had out on the water. Today we were joined by Steve and Riley Hathaway from Young Ocean Explorers who were filming some awesome multi-species feeding aggregations in the Hauraki Gulf – Tīkapa Moana – Te Moananui a Toi.
Today’s adventure started at 9am where we departed from Leigh harbour, it was a tad windier than we had liked but the water was crystal clear and we were excited for a day out on the water. Today was a quiet day out with only a few MSFA’s spotted.
From the prevailing weather forecast and work up predictions we decided to head towards Waiheke Island and the Noises Islands. Here we spotted our biggest work up of the day! Over 200 gannets and 20 dolphins were all feeding together in one big aggregation. We slowly approached the MSFA, following the low flying gannets to their lunch spot. What really excites me about these feeding aggregations is how different species and individuals work together to exploit a prey patch, with the underwater herding behaviours of the dolphins counteracting the vertical scattering effect of the plunge diving gannets. This dynamic aggregation eventually split into two, with the initial 200 gannet strong group splitting in half. Over time as the original patch of food reduced, the gannets and dolphins moved to the second group – highlighting how ephemeral and spatially dynamic these prey patches are.
The highlight of the day, however, was encountering two Bryde’s whales (Balaenoptera edeni) and three poop patches! While these animals weren’t engaged in feeding behaviours it was still a cool sight to see! Whale poo is also a really awesome find because it can tell us a lot about a whales diet and health! Bryde’s whales are filter feeders which means they have a tendency to engulf microplastics – such as lint from our clothes and degraded ocean debris. Researchers from the University of Auckland use poo samples to analyse the amount of microplastics ingested by Bryde’s whales to estimate exposure risk and better understand the risk of micro-plastic ingestion by filter-feeders.
Unfortunately we didn’t have a whale pooper-scooper with us today but it’s bright pink colour tells us that shrimp was on the menu for this Bryde’s whale!
Can’t wait for our next field day out!
Until next time, sea you later!