These 40-50 foot giants used to number in the thousands, but now, with only about 500 individuals left in the wild, the North Atlantic right whale is listed as endangered on the IUCN red list. Stories of species declining in the wild, such as this, are far too familiar. And they are far too often linked to human activities.
Right whale populations have been under pressure from humans for hundreds of years. Additionally, they suffered a big loss this past summer when 15 dead right whales were found in U.S. and Canadian waters. This was a mass mortality event that has never been seen before. For a population that numbers only 500, this represents a loss of 3% of the population! So what is going on with the North Atlantic right whales? Why did so many die-off occur this past summer? And what can we do about it?
The right whale population declined over a period of hundreds of years from the 1600s to the 1900s due to whaling. At a minimum 5,500 individual right whales were removed from the oceans by humans over this period! Fortunately, right whales were legally protected in 1949, which curbed the harvest of these large creatures. Unfortunately, this hasn’t totally alleviated the impacts humans are having on the whales.
Of the 15 dead whales found during the summer of 2017, seven were necropsied to determine the cause of death. Six of the seven deaths were caused by human-related activities. Four whales were struck by ships and two were caught in fishing gear, while the cause of death for the last whale was inconclusive. Right whales can get entangled in many types of fishing gear but the buoy lines associated with pot and gill net gear are the most frequent offenders (Johnson et al. 2005).
Many of the dead whales were found further North than their usual range. With warming ocean temperatures due to climate change, right whales may be moving further north in search of cooler water. In these new areas, the whales may be more exposed to anthropogenic threats. Right whales are not typically found in these areas and so shipping and fishing regulations designed to protect whales are not enforced in these areas.
REPRODUCTION, FOOD AVAILABILITY & CLIMATE
Recently, right whales have been producing fewer offspring than normal. The cause of these low reproductive rates remains a mystery but many ideas have been put forward. Some ideas include poor nutrition, chemical contamination, and even entanglements. It has been estimated that 83% of the North Atlantic right whale population has been involved in an entanglement with fishing gear at some point in their life based on scarring seen on living whales. These sub-lethal entanglements can cause declining health and have negative impacts on reproduction.
However, a new study points to poor nutrition due to low food availability as a likely cause. Right whales feed on tiny animals despite their large size. Their prey is mostly made up of copepods, a small crustacean, but also includes other small invertebrates. These invertebrates need to be found at really high concentrations for whales to get enough energy, especially when they’re reproducing. As climate change warms the ocean, right whales need to move further north. These new, northern areas may not have enough food to support high levels of reproduction in whales. This suggests that climate change may be the ultimate culprit for low reproductive rates.
There are ongoing efforts to minimize deaths and injuries due to ship strikes and entanglements in both the United States and Canada through collaborations with various stakeholders. This can be accomplished by reducing the speed of boats and rerouting them when possible. Shipping lanes have been moved in the Bay of Fundy to shift them away from the summering grounds of right whales. Additionally, fishing gear modifications are being implemented.
This involves using modified gear at certain times and in certain areas where right whales are found in high numbers. Also, reducing the breaking strength of the ropes that are used for fishing (making the ropes easier to break) could reduce deaths and injuries associated with entanglements while still being strong enough for fishing operations (Knowlton et al. 2015).
Even if we make all of these changes to our fishing and shipping practices, it remains uncertain whether the North Atlantic right whale will be able to recover. The effects of climate change are harder to predict and mitigate. However, we must still do whatever we can to stop the accidental, anthropogenic deaths of right whales. And hopefully, we will have enough of an impact that summer 2018 will not bring as many fatalities as in 2017.