Sir Peter Blake Ambassador Fenna Beets - smooth sailing
Fenna Beets is one of the two recipients of the Sir Peter Blake Trust Marine Science Award. In her role as a Sir Peter Blake Trust Ambassador Fenna is currently on-board RV Tangaroa working alongside NIWA scientists to survey New Zealand fisheries, biodiversity and seabed geology on the Chatham Rise.
Setting sail on day one the weather was brilliant and the swell minimal, a good omen for what was ahead. This has held true for the trip thus far and fingers and toes are crossed for it to continue. I spent some time on the bridge on Monday and Damian, who is the 2nd Mate, showed me some of the radar equipment they use for noting other vessels, including what they are doing (steaming or fishing), what their heading is, and if we will come into close distance of them. I asked if he had seen any dolphins while on his watch and just as he finished saying he had not, a pod of dolphins came swimming towards the bow and elegantly fell in line with us. I have never seen dolphins remain with a vessel for so long. We left the bow before they did, who knows how much longer they cruised with us for. It was a real treat! We saw another small group for a split second at lunch one afternoon and have also been treated to sighting the odd seal. You can’t not love these gracious marine mammals and they are certainly worth a mention!
The main element I want to touch on for this entry however, is something that I find really interesting and exciting from a scientific standpoint. We have a physicist called Adam on board, who says he avoids the fish lab as much as possible, a laugh since he is largely responsible for some of the mesopelagic tows we are doing! The reason I say he is responsible, is that he is trying to improve software that predicts what species are occupying differing acoustic layers on echograms.
Acoustic echosounders work by beaming a burst of sound down into the water and measuring what bounces back up when it hits the fish. It displays this as a picture called an echogram. Because fish have differing densities, size and behaviours, acoustic scientists can begin to work out what species of fish are being seen on the echograms at varying frequencies.
We hauled a mesopelagic trawl net target tow in the other day with over 95% of a single species called Maurolicus australis, a small silver fish with bright purple dots on its belly. Adam guessed it to be this species from looking at the echogram, but the software said it was Electrona carlsbergii which is a similar sized fish. The software predictions are based on what species have been found so far from trawls on specific mesopelagic layers on the echograms, and so the purpose of our tows is to check the truth and refine the prediction software. The reason it is so exciting is that NIWA has collected around 20 years of acoustic data of this sort all over the Chatham Rise while doing regular trawl surveys, and if they can accurately and consistently identify species of fish in differing layers using acoustics alone, then this data suddenly comes to life and can tell us about these mesopelagic populations over time.