Saving Auckland's iconic whales

They’re the mysterious giants of Auckland’s Hauraki Gulf; warm-blooded, bigger than buses, dark grey with ballooning pleated white bellies and huge mouths bristling with baleen. They’re Bryde’s whales, and about 60 of them live in the Hauraki Gulf year-round, hanging out just a few metres below the waves as they feed on great mouthfuls of fish and krill. If you’ve ever taken a ferry out to Waiheke Island or fished for a feed near Moutihe Island, you may well have passed close by or even right over one without realising it.

Bryde’s whales are from the same family as blue and humpback whales, which are also known as rorquals, a name that refers to those pleated underbellies which expand to take in huge gulps of food. Weighing up to 25 tonnes, they’re hungry beasts, and can consume 600kg of small fish, krill and plankton in a day.

That’s why they’ve made their home in the Hauraki Gulf, says Dr Rochelle Constantine, head of the Marine Mammal Ecology Group, director of the Joint Graduate School in Coastal and Marine Science, and a senior lecturer at the University of Auckland. “The Gulf is a highly productive ecosystem – there’s a lot of mixing of waters. It’s a really diverse place for marine mammals. It’s a real gem and I don’t think a lot of Aucklanders realise it. It’s not just a place you go to get a snapper. It’s a really important place for a lot of animals, a really crucial ecosystem.”

The whales are fairly solitary creatures, noodling around by themselves or in pairs most of the time. Constantine says they can often be spotted working up ‘bait balls’ of small fish, which attract pods of dolphins and diving seabirds. They can be identified when surfacing by a straight dorsal fin about three-quarters of the way along their backs, which often has a notched or ragged rear edge.

Where are the whales?

Not a lot is known about Bryde’s whales as their preference for temperate subtropical waters means they don’t store much blubber, so were unattractive to whalers in the 19th and 20th centuries. In fact, when Dr Constantine worked on a project just a few years back, where suction-cup tags were attached to seven Bryde’s whales to record their activity, the project team were amazed to discover that even though the whales generally live in water 50-60m deep, they spend over 90 per cent of their time just six and a half metres below the surface. “That’s less than one of their body lengths,” says Dr Constantine. “And at night they’re even closer, only five and a half metres below the surface. They’re right there.”

The team also discovered that the whales are very busy during the day, diving up and down, foraging and moving about, whereas at night, they’re barely active at all – probably resting up after a hard day’s work.

Unfortunately, this habit of staying close to the surface puts the whales at the often-fatal risk of being struck by ships. Auckland has the busiest port in the country, with well over 1000 visits from container ships every year. With hull draughts of up to 12m, these ships plough directly through the underwater zone that Bryde’s whales spend most of their time in.

Ships vs whales

Dr Craig Pritchard, head of the New Zealand Centre for Conservation Medicine at Auckland Zoo, and a member of the forensic team that has been performing necropsies on all recent Bryde’s whales found dead in the Gulf, says the captains of the ships have no way to tell when they strike a whale. “If you were travelling on the Fuller’s ferry and you hit one, you’d know, but if you’re in a 210m container ship, you wouldn’t have a clue. Sometimes the ships will come into the port and they’ll have a whale wrapped around the bow and they won’t even know about it.”

Ships may not even need to be unlucky enough to strike a whale directly, says Dr Constantine – if a big enough ship passes close enough to a whale, the force of the moving water can suck a whale into the ship’s path.

“We’ve got a real problem here,” she says. “We’re losing about two whales a year to ship strike, which is probably not okay because of the replacement rate. Bryde’s whales are long-lived, slow-breeding. And we don’t really have a good measure of the impact of ship strike on the whale population because it takes a long time to accumulate the data. It’s not until you’ve had 20 or 30 years of data collection that you can really see the magnitude of the problem.”

Of the 18 whales that have been assessed for cause of death over the last 10 years, a significant majority appeared to have been killed by ship strike. Dr Pritchard says indicators like grazing, bruising, muscular damage and broken bones can show where a whale has been hit by a ship. The most recent necropsy of a 14m female whale also showed she had not reached sexual maturity, meaning that she was killed before having a chance to breed.

“Not many people know these whales exist,” says Dr Pritchard. “They’re beautiful creatures, big, gentle giants, and they’re in our backyard.” He’s doing his bit to raise awareness of the whales with a photographic installation at the Centre for Conservation Medicine at Auckland Zoo, which shows the process of necropsying and burying a dead whale. “Where I think Auckland Zoo is good, is that we have 700,000 visitors through our doors a year,” he says. “When we have Sea Week, we really push this. We’re just trying to tell a story and get people involved.”

What’s the solution?

So, if ships don’t know when they’ve hit a whale, how do you stop them hitting whales? It’s a hard question to answer, but Dr Constantine says various groups are doing their best to find a solution. The Department of Conservation, the Ports of Auckland, Auckland Council, local tangata whenua, and the Hauraki Gulf Forum have all met with Dr Constantine and other interested parties to discuss solutions in a working group that meets every six months. “The industry is very clear they don’t want to kill whales,” says Dr Constantine. “But it is a cost of having large shipping. Auckland is New Zealand’s busiest port. It’s where so much of the stuff that Auckland uses and exports comes and goes from. Slowing down has been identified as the best way to minimise ship strike mortality, but there’s a financial cost to slowing down.”

Based on research from overseas, Dr Constantine says 10 knots is a harbour speed limit that would lower the risk of ship strike mortality to 20 per cent. “It doesn’t get to zero, but you’re never going to get to zero without stopping shipping entirely.” At present ships average 14 knots through the Gulf. That still presents a high risk, she says. “When ships are going 15 knots, there’s an 80 per cent chance of mortality.”

However, Matt Ball from the Ports of Auckland disputes these figures. The company doesn’t control speed limits on the harbour – that’s the responsibility of government, councils or harbourmasters – but it does co-ordinate the industry response to whale strike. “Compulsory speed reductions are problematic,” says Matt. “Yes, reducing speed reduces the likelihood of killing a whale, but it doesn’t eliminate it.” The Ports of Auckland prefers voluntary measures, and encourages shipping lines that enter Auckland to slow down if they are ahead of schedule. They’ve also set up a whale warning system, where anyone who sights a whale radios Harbour Control which transmits the details to all ships, so they can try to deviate away from the whale, or slow down.

“It’s a good idea,” says Dr Constantine. “Although we don’t know whether by deviating from the path of one whale, that they’re not deviating into the path of another.”

A whale worth protecting

Both the Ports of Auckland and Dr Constantine are looking forward to the results of an aerial surveying programme set to happen in the next few months, which will help work out whether the whales are grouped loosely in certain areas, or if they’re spread evenly around the Gulf. “It will also allow us to look at prey aggregations and associations with dolphins and other species to try to predict where they’re likely to be found,” says Dr Constantine.

Whatever the results, she says, it’s important that New Zealanders make protecting the Bryde’s whale a priority. Whales and dolphins are apex predators – they’re either large consumers or top-of-the-food-chain consumers. Research in Antarctica suggests in the process of eating and excreting krill, the whales create bioavailable iron – a mineral required for phytoplankton to grow – and phytoplankton is the start of the food chain. “So whales in some way are actually fertilising the ocean,” says Dr Constantine. “Their role in ecosystems is really important.”

And the giant mammals are iconic creatures, she adds. “People really love whales and dolphins, and I see that we can use that to argue marine conservation cases. Because if we can’t save the things that we love, there’s not much hope for the things we don’t love, and don’t see, and don’t know about… which is most of the marine world. If we accept that it’s okay for whales and dolphins to disappear, then I despair for the barracouta, or the slimy sea slug or the snotworm.”

Bryde’s in brief

• Genus: Balaenoptera.
• Species: B. brydei, B. edeni, B. omurai.
• Size: 13-15m long, up to 25 tonnes.
• Found: Around New Zealand, South Africa, Japan, California and Mexico between 40 degrees north and south (Whanganui in New Zealand, and Iwate in Japan, approximately).
• Eats: Fish up to the size of a sardine, plus plankton and krill.
• Number in NZ: Around 200, with a population of just under 60 in the Hauraki Gulf.
• Status: Critically endangered – on NZ’s national top 10 endangered list.

Fun facts

• Bryde’s is pronounced ‘broo-ders’. The name comes from a Dutch entrepreneur who helped open the first whaling station in Durban, South Africa.
• The Bryde’s whale is the only baleen whale that doesn’t migrate to the polar regions to breed. That means whale calves are being born right in Auckland’s Hauraki Gulf.
• Females breed every second year, giving birth to a single calf about 3.5m long.
• There are thought to be three different species of Brydes whale: an ‘inshore’ type, an ‘offshore’ type, and a ‘pygmy’ type (also known as Omura’s whale).

What you can do

If you’re out and about on the Gulf and see a whale, you can call Auckland Harbour Control on Channel 16 to report the whale’s location so they can advise nearby container ships to adjust their path.

If the whale you see is stranded, injured or dead, call 0800 DOC HOT (0800 362 468) right away.

You can also register any sightings through the Department of Conservation Marine Mammals sightings page. If you can attach a photo to your report, that’s extra-helpful.

If you want to register your support for a lowered harbour speed limit of 10 knots to help protect Bryde’s whales, you can write to Auckland Council.