EVERY year, whales migrate along the Pacific coastline attracting inquisitive and awestruck eyes to Far South Coast beaches, headlands, lookouts and boats.
They usually head north to the warm coastal waters of Queensland and the Coral Sea to mate and give birth from late April to August, and return southwards from around September to November.
According to yet-to-be-published research by Geoffrey Ross, wildlife management officer and coordinator of the Marine Fauna Program for the NSW National Parks and Wildlife Service (NPWS) off Cape Solander south of Botany Bay, humpback whale migration periods are becoming longer every year as their numbers increase rapidly.
“Roughly by 2017 we will be seeing twice the number of whales passing Cape Solander than we saw in 2009,” Mr Ross said.
“We are seeing whales that leave early leaving earlier, and whales that leave late leaving later, so we will see whales over more of the year.
“Triggers such as day length and water temperature do effect the humpback migration, but there are a lot of variables involved that unfortunately the whales have no control over.
“The stragglers heading north later are either older or sick and so are slower and may miss out on a breeding season, while the slower ones heading south are mothers who stay longer with new calves,” he said.
Since Australia banned whaling in 1979 their numbers have improved, especially in the case of the humpback.
“We are seeing numbers at 16-18,000 over a season, which is down from the pre-whaling days of 36-40,000, which means we have about half of the expected numbers off the east coast,” Mr Ross said.
Ecologist Dr Peter Gill from charitable organisation Blue Whale Study has also noticed recent migration changes, in both blue whales and humpbacks.
“This [last year] is the earliest we have ever seen blue whales arrive in the Bonney Upwelling, and it is the first time I have seen humpbacks hanging around feeding.
“I don’t know why - we are just trying to understand how changes in upwelling intensity here over various time scales might influence whale numbers and it is a very tricky field of study.
“One reason that the timing might be changing could simply be that there are now so many more humpbacks than there were even 10 years ago, because when I started humpback research on the NSW coast in the early ‘80s there were probably fewer than 1000 migrating whales, now there are 20 times that,” he said.
“As they increase they will spread out in space and time.
“Changed timing could also be due to large-scale oceanographic changes somehow related to our changing climate, either in the Antarctic feeding grounds or elsewhere,” he said.
Field officer for NPWS and caretaker of Green Cape Lighthouse Gary Mulligan last year witnessed whales heading south in mid-February and north in the early days of March, leaving only a number of weeks between the sightings.
“Just this morning I had two humpback sightings heading north,” he said this week.
“We’ve seen more and more every year and they are travelling a lot closer to shore than in the past, sometimes breaching just 30 feet off the rocks.”
It’s good news for humpbacks – and whale watchers.
However, Mr Ross said the same cannot be said for the southern right whale, which is recovering more slowly due to the whaling pressures of the past and their calves also being subject to vessel strikes.
“We’ve lost two calves in the past three years on the east coast from a population of about 16 that commonly use NSW state waters, which is why I stress the importance of posting extra lookouts when you’re on the water during whale season, and ask recreational and commercial vessels to travel more slowly within our bays and estuaries,” Mr Ross said.
He is hoping to publish his findings after the 2015 season has concluded.