Whales, krill, climate change and the omega-3 addiction
By Iain Watt, President EcoNetwork Port Stephens.
Humpback whales (Megaptera novaeangliae) named for the hump of blubber lying in front of their dorsal fin, lying about two thirds along their back have fought back from near extinction. But the real battle is only beginning. They are found in all oceans. In the southern hemisphere they migrate from their feeding grounds in the Southern Ocean to the warmer tropical waters, in the case of the Eastern Australian population, off Queensland where they breed, calve, and nurture their young. This 10,000 km round trip is the longest migration of any mammal. They are seen off NSW travelling north between May and July and heading back south from September to November, taking approximately 3 months in each direction, travelling at an average of 8 km per hour, but often as slow as 1.5 km per hour when socialising.
Young males lead the way north with adult breeding animals forming the bulk of the migration followed by pregnant and females with calves that continue feeding to build blubber reserves and the energy required for the journey ahead.
Adult humpbacks can grow to 11 – 18 m long and weigh up to 50 tonnes (mature males are slightly smaller than females). They reach physical maturity at 12 – 15 years (13 – 14 m) and can live for 50 years. Females reach sexual maturity between 4 and 10 years old. Mating and calving takes place during June to October in warm tropical waters of 22o – 25oC. Gestation takes 11.5 months and calves are 3 – 5 metres long, weigh up 2 tonnes at birth and consume 45 to 100 litres of > 60% fat rich milk per day to survive for their first 5 months to a year. Unsurprisingly, they only calve every 2 – 3 years. Lactating mothers spend 16 hours per day resting at or near the surface prior to migrating south.
Humpbacks only sleep for 30 minutes at a time, any longer and they risk a dangerous loss of body heat. They can hold their breath for up to 40 minutes absorbing 90 % of the oxygen in the 200 litres of air that they inhale, but usually only dive for a maximum of 15 minutes to about 150 – 200 m. By comparison, a sperm whale can swim down to 2250m.
Individual humpback whales can be identified by the unique markings on their tail flukes. Their rostrum and pectoral fins can be covered with large numbers of the acorn barnacle Semibalanus balanoides, often with the goose barnacle Pollicipes pollicipes growing on top of the acorn barnacles. They have up to 35 distinctive broad ventral throat grooves, extending to their navels that allow for expansion of the mouth/throat when feeding.
Between 1949 and 1962, 8,300 humpback whales were killed off the east coast of Australia. Nearly driven to extinction, the population was down to around 100 – 300 animals, approximately 3.5 – 5% of pre-whaling numbers before the International Whaling Commission (IWC) banned humpback whaling in the Southern Hemisphere in1963 and were protected in NSW in 1965. However, commercial whaling continued in Australian waters with 16,000 sperm whales taken before the IWC in desperation, finally called a moratorium on all whaling in 1986. All whales in Australia are listed as vulnerable and protected under the Biodiversity Conservation Act 2016.
Since 1965 the Australian east coast humpback population has rebounded to circa 30,000 and whale watching has become a popular tourism attraction from May to November.
With changing public opinion driven by organisations like Greenpeace and Sea Shepherd, the Australian Government finally held an inquiry into whales and whaling and came out on the side of the whales. However, given the number of whales left, was this a win for the community or the normal cynical economic expediency, underpinned by opportunistic politics. We seem to have a fundamental problem understanding the concept of sustainable resource management over short term acquisition.
The enigmatic whale song, which some sailors will have heard through the hull of their boat, was thought to only emanates from the males. But mothers and calves have also been recorded in shallow water whispering to each other. They may “whisper” to avoid attracting predators like orcas or amorous males from the deeper waters. The whale song is complex, haunting, and distinctive, and can go on for hours. It can change subtly each year and different populations have different songs. There is no scientific consensus on why the males sing, but it is thought to be used to communicate their presence and to entice (woo) females to mate with them.
Recent research on Australian humpbacks from 1997 to 2015, found male humpbacks sang less and fought more as the whale population recovered and competition for mating became more intense. With the rapid population growth, reducing song is thought to be a tactic to avoid attracting other males to potential mates, preferring to quietly find a female to mate with, and avoiding having to fight off other male competition, particularly when there is a higher proportion of males in their social circle. However, it is unlikely that whales will lose their song, more likely they have simply adapted to improve their chances of mating. The ability to adapt will become more prominent as they change behaviours to meet the challenges of future climate change stressors.
Humpbacks feed primarily on Krill, ‘swarms’ of finger-sized, shrimp like crustaceans that underpin the Southern Ocean food chain. Krill and small fish are filtered through the 270 – 400 baleen plates which hang from both sides of their upper jaw. Humpbacks are estimated to consume between 1 – 1.5 tonnes of Krill and small fish per day.
They have a range of feeding strategies. Trap feeding, the animal lies still on the surface with their mouth wide open, not perceiving the threat of the still object the krill and herring shoal into the mouth for shelter, the mouth is heaved shut trapping the krill and herring in a single gulp. With bubble net feeding a single or group of whales swim under the prey releasing small bubbles to create a ring of bubbles corralling and concentrating the prey into a tight ball before lunging upwards to gulp the prey. This behaviour is mostly documented in northern hemisphere populations but was recorded off NSW for the first time in 2022. The eastern Australian population is known to occasionally feed on the southerly migration if a swarm of Krill or small fish are encountered, but they are usually observed lunge feeding on their side or feeding below the surface.
Humpbacks are ‘capital breeders’ and can go months without feeding, relying on their blubber reserves for use during the breeding cycle. They build their blubber reserves feeding on iron rich Krill and do not build muscle that requires iron. So the remaining iron is excreted in their poo, which is estimated to have a concentration of iron 10 million times more than iron concentrations found in normal seawater. This process of feeding in one area and pooing (large quantities) in another is known as the ‘whale pump’ and has important ramifications for ocean ecology and climate change mitigation.
Ocean waters are generally iron deficient, and the lack of iron is one of the critical limitations for phytoplankton production. The “whale pump” helps disperse iron into the ocean waters supporting phytoplankton production, a key ocean resource, phytoplankton is a primary producer forming the base of the ocean foodweb and plays a key role in the oceans’ capacity to absorb more CO2 and produce more O2 than any other ecosystem in the world. Oceans are the “planetary pump” that supports life on earth. The decimation of the whale populations through last century must have contributed to the current desperate state of our oceans, and no doubt had much wider ramifications on the health of the oceans than generally recognised.
Krill is one of the most abundant animal species in the world, estimated at 375 – 500 million tonnes in the Antarctic. Krill poo, like whale poo, plays an important role in climate change mitigation, forming relatively large Carbon rich pellets that rapidly sink to the seafloor, sequestering Carbon away for many years. It is estimated that in this way, Krill removes 23 – 39 million tonnes of Carbon per year, making the Southern Ocean the largest Carbon sink in the world.
Healthy Krill populations are critical to the health and productivity of the Southern Ocean. It has been hypothesised that the decimation of the whale populations last century allowed krill numbers to increase dramatically. This abundant food supply may have contributed to the rapid recovery seen in the humpback populations. But Krill densities have been declining in recent years. This incredible resource is under threat from industrial fishing and climate change impacting their habitat range.
Warming sea temperatures are driving Krill further south and the combined effects of rising sea water temperature and ocean acidification are reducing Krill development and hatching rates, which will ultimately lead to a population collapse. On top of this, fishing pressure is increasing. This will impact on all animals that rely on Krill as a significant proportion of their diet such as fur seals, penguins, albatross and other seabirds. It will also impact on the whale migration and the overall health of the whale population, forcing them to travel further for less. Although their ability to switch prey and adapt has been documented in humpback populations elsewhere, this will be a major, possibly unseen impact of climate change with wider implications for the rest of the world. A key Krill fishing area, around the Antarctic Peninsula is one of the most rapidly warming areas in the world and has warmed by 3o over the past 50 years, as a result, Krill populations are expected to fall by 30 % – 40 % by 2100 caused by climate influences alone.
The Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) was established in 1982 to regulate fisheries in the Southern Ocean. Fishing pressure is growing rapidly with larger ships on order from China and Norway to meet the demand for Krill based product. The stocks are highly concentrated within specific areas and the current vessels can suck up 1000 tonnes of krill per day, taking 450,000 tonnes of Krill in 2020, a 15% increase on the previous year.
The British Antarctic Survey states that after 90 years of study, the biology and ecology of Krill remains poorly understood. The 2022 IPCC report indicated climate stressors could present considerable risk to the Krill populations, and the marine food chains in Antarctica and ultimately around the world. Any claims of sustainability are stretching reality.
Demand for lipid rich high profit Omega 3 health supplement found in Krill has taken off despite the lack of any proof regarding the apparent health benefits purported by the market. This coincides with greater demand for aquaculture feed, bait for chumming the water for game fishing and livestock feed and pet food, all on the rise. Krill is the target of the Southern Ocean’s and possibly the world’s largest fishery – ironically thought to be sustainable.
Delays in ice formation allows fishing to continue into the winter, targeting animals rich in Omega 3 lipids after the summer feeding. This is when the Krill should be protected from their natural predators by the sea ice. The known variability in spawning success and high variability in biomass indicates that Krill is at extreme risk from increased fishing pressure.
Despite the laudable congratulatory attitude to saving the whales, in fact they are probably as endangered now from climate change as they were from the whalers. The threat to the Krill from industrial fishing will have worldwide implications, despite lack of any evidence that Omega 3 lipids have health benefits.
We have a very poor track record of managing our natural world and its resources, why would the Krill fishery be any different. Krill is far too valuable to the Southern Ocean, the whales, seals and seabirds and the world at large to be randomly converted into fish food, pet food, and snake oil. Let’s not be short sighted about this, the only weapon we have to fight this avaricious stupidity is to avoid purchasing products that contain Krill product. This might pre-empt the inevitable “too little too late” approach typically taken to avoid change, until faced with the reality of economic extinction or actual species extinction.
Of all the existential threats to whales, and seabirds – it is climate change – probably not wind turbines, one of the only options to continued carbon based climate change – if we want to carry on in the luxury to which we have become accustomed.…….
Scientists and the krill fishery need to work together though to protect nutrient cycles, the carbon sink and the environment. In fact, we believe it is unlikely that any fishery globally considers the impact that removing animals like krill or fish has on nutrient cycles.
We still don’t know exactly how removing krill from the oceans will impact the atmosphere and oceans, and how climate change will further exacerbate this. But one thing is for sure, krill are important in supporting life and storing carbon in the oceans.
It has been estimated that the 12,000-strong population of sperm whales in Antarctica removes approximately 200,000 tonnes of carbon per year from the atmosphere.