Source: Greenpeace New Zealand
Liz Slooten, marine mammal expert, gives a Q&A session with some Greenpeace supporters asking the questions!
Q: Just wondering what the most up to date info is on Māui and Hectors and the fishing industry – how is the campaign going? How do you think our current situation will impact that?
Hopefully we will get a decision from Government on better protection for Māui and Hector’s dolphins soon. Right now, it sounds like fishing is continuing, but observers are only going out on very large vessels. Not the smaller vessels inshore. So we are really flying blind now. If only they had got those cameras on the fishing boats, which government have been talking about for many years now, we would still be collecting information on how many dolphins are being killed in gill nets and trawl nets. The fishing industry strongly object to having cameras on boats, and have repeatedly blocked this. They are just playing for time. The longer they can drag this out, the longer they can keep using destructive fishing methods like gill nets and trawling.
Q: Why do you think has there been so little attention paid in media over the years to the dire state of Māui dophin compared with, say, kakapo?
I wish I could answer that question! There seems to be some weird difference between species that live on land, and species that live in the sea. As soon as you start talking about conservation of marine animals, the fishing industry lobby get involved and the argument becomes about whether the number of dolphins killed is sustainable (which it isn’t). i.e. Sustainable “harvest” (same as for fish) rather than about “protection” (as you would for kakapo). There is no excuse, or scientific rationale for treating marine animals any different.
Q: On the 7% that are recognisable is the data collected for predicted survival forecasts based on this number only?
These are not “forecasts” of future survival, but estimates of past survival. But yes, the estimates of survival are based on the 7% of the dolphin population that are recognisable. Other than there being fewer very young animals with natural markings (most of the markings are nicks in the dorsal fin caused by sharks, running into fishing gear etc) this sample of the population appears to be representative of the population as a whole. Similar mix of male and female, young and old individuals, etc.
Another option for estimating survival (which was more common in the past) is to tag dolphins to make them recognisable. Either by catching them and freeze branding them, or drilling holes in the dorsal fin and attaching a tag. This results in a much smaller proportion of marked individuals. Usually well below 1% of a population. Tagging, and biopsy sampling, are usually not allowed for calves and other young individuals. You have to catch dolphins to tag them, which means you can only sample individuals that come close to the boat. Not necessarily a random or representative sample of the population. For example, mothers and calves usually stay a bit further away. Tagging is very time consuming, expensive and risky for the dolphins. An estimate of survival for tagged dolphins would also be biased low, due to injuries and occasionally deaths caused by the tagging itself. For these reasons, using natural markings is the standard way to estimate survival and reproduction for whales and dolphins.
Q: Does the NZ Dolphin and Whale Trust have citizen science project/s that interested individuals can participate in?
Not right now unfortunately. We would need staff to coordinate something like that. Maybe when I retire.
Q: In Akaroa Harbour we often go out to look for dolphins. I also am concerned about the impact of the numerous cruise ships. Even when they are moored they cause a lot of upheaval of silt from the seafloor. This combined with radio/sonar noise from the ships, do they affect the dolphins? How is their reproduction been this year?
I agree, the cruise ships cause lots of silt being stirred up. They also make noise, dump sewage (outside the harbour, but still). We are studying the effect of this on the dolphins. Will Carome, a very bright student from the US is working on this. Dolphin reproduction this year has been very low. Less than 1% (0.8%) of the dolphins we saw this summer were calves. The average, over the last 30 years is 4.4% and the maximum is just over 8%. We don’t yet know what’s causing this, but are looking into it.
Q: How do the dolphins sleep? Because they need to breathe?
They rest half of their brain at a time, usually closing one eye (the one corresponding to the half of the brain that’s “sleeping”). You’re exactly right, they have to keep breathing, so they can’t sleep the way that land mammals do (including humans). They just keep slowly swimming around, while continuing to breathe. Must be exhausting being a dolphin! But then again, they will be used to it. It seems to us that would be very tiring, but it will seem normal to a dolphin.
Q: As an overseas student of marine biology, is there any chance of doing internships or voluntary work in your specific field?
Our students take out volunteers in the boat with them. We don’t usually do internships, because they involve a lot of extra time for the researchers. The best option for an ‘internship’ is to enroll for an MSc (or PhD) study.
Q: Do you promote the use of dolphin excluder nets?
These don’t work well for dolphins. The best way is to avoid using fishing nets in dolphin habitat. Switching to other fishing methods like fish traps and hook & line methods in those areas.
Q: Do we know how a pod of dolphins interact with other pods? Are they quite social between pods or maybe a bit territorial?
They are very social. Hector’s dolphins live in small groups of 2-8 individuals. When these groups meet there is a major increase in social activity. There is no indication of them being territorial.
Q: You mentioned using drones to spot some of the dolphins. I know there are some projects to use drones to stop dolphins getting caught in fishing nets. Can you always see the dolphins from the air like this?
This doesn’t work. Drones are very useful for research. But not for stopping dolphins getting caught in fishing nets. The chances of finding a dolphin using a drone are very low. Drones have a very small field of view. So you can only search a small area at a time. Gillnets are in the water for at least 24 hours at a time. Often longer. There is no way you could keep searching for dolphins near the net for all of that time. And of course it won’t work at night.
Q: Can you tell us more about how a hydrophone works?
It’s basically an underwater (waterproof) microphone. You can distinguish Hector’s and Māui dolphins from other dolphins because they have very high frequency sounds. Well above human hearing. We anchor hydrophones in the water for several weeks at a time to find out how much of the time they can hear dolphins. This has allowed us to study seasonal patterns of dolphins using Akaroa Harbour and other areas.
