With its common name originating from whalers who, because of their tendency to float on the surface once dead, decided that they were the ‘right whale’ hunt, the North Atlantic right whale (Eubalaena glacialis) has had a somewhat difficult past with people. By 1530s Basque whalers where happily taking these whales (and others too) off Labrador and Newfoundland in the Northeast Atlantic. By the mid-1600s, shore-based whaling took off down the east coast of the USA. Between 1634 and 1951, it is estimated that somewhere between 5,500 and 11,000 right whales were killed by hunters. 1935 saw the introduction of the Convention for the Regulation of Whaling – the first protection afforded to these critters but many – but not all – whaling nations (Japan and the then Soviet Union being the exceptions). Protection was bolsters in 1949 with the International Convention for the Regulation of Whaling (IWC), which banned signatories from hunting them for commercial purposes. In the US, they were listed under the Endangered Species Conservation Act in 1970, and the subsequent Endangered Species Act of 1973. Canada, who is not a signatory of the IWC, has listed them under their Species At Risk Act (SARA) as Endangered. Today it is estimated that there are somewhere between 300 – 400 individuals left, and whilst commercial whaling has ceased, they are still under threat primarily from ship strikes or entanglement in shipping gear.
To help tackle the ship strike threat, Seasonal Management Areas (SMAs) were introduced off the east coast of America in 2008. The rules are fairly straight forward, limiting speeds to under 10 knots (18.5 km/hour) for commercial vessels larger than 65 feet (20 meters) long. There are currently 10 SMAs, which become active seasonally to capture when right whales are actually in the area, and then deactivate when the whales should have moved off. Alongside the SMAs, Dynamic Management Areas (DMAs) were also brought it. These zones are implemented when aggregations of the whales are detected in areas outside the SMAs. For 15 days after detection, mariners are asked to avoid DMAs. If they do pass through, they are asked to voluntarily reduce their speeds. So do these zones work to reduce ship strikes on the right whales – and indeed any other large whale population that may find itself inside these zones? According to this latest study lead byfrom … sort of.
Julie and her fellow researchers obtained confirmed mortality data for a whole host of whale species – not just right whales – that were reported along the American east coast between 1990 and 2012, alongside cause of death (if identified). They also obtained sighting data from North Atlantic Right Whale Consortium database from 1990 to 2008. This, the team report, will help them assess the whales’ occurrence inside – and indeed outside – the SMAs. Some statistical, spatial, and temporal analysis later, and the team were able to tell us a little more about the effectiveness of these SMAs.
First to the mortalities. Between 1990 and 2012, 1,198 confirmed mortalities were reported along the US east coast. Most of the whales species were identified too – good news for the researchers, but cause of death was only confirmed with certainty in 458 cases. In line with other study findings, entanglement was the leading cause of death, followed by vessel strikes.
The sightings data indicated that just 17% of the right whale sightings between 1990 and 2008 were outside the areas that would become SMAs. In other words, when the SMAs were implemented in 2008, they were located in areas where 83% of sighting had previously occurred. Not bad – its tricky to capture every individual in a management zone when those individuals tend to move around a lot. So what of the strikes themselves… are they reduced? Well the good news is that over the years right whale ship-strikes have shown a decline… though not directly coincident with the introductions of the SMAs (the decline started from 2007, the zones were implemented in 2008). The researchers also note that active SMAs only encompass 36% of historical right whale strikes. 32% of the historical strikes occurred when the SMAs were active, but not in the areas the SMAs covered.
So whats going on here? Well the team believe that the decline is right-whale strikes is likely down to a combination of measures introduced earlier – like voluntary and mandatory routing changes in the Bay of Fundy. They also suggest that the SMAs themselves may not be as effective as they could be because of low vessel compliance (estimated to be around 21 – 33% between 2009 & 2011). They also suggest that there is insufficient monitoring to detect just how effective these management areas are…meaning the management strategy could never adapt to be ‘better’ because no one knew that there was a potential issue. The last major issue the researchers highlight is the timing and location of the SMAs. The SMAs cover critical habitat and calving areas for the right whales but they are missing in the ‘migratory corridor’ that run along the east coast. It is in this corridor where whales are most often sighted, and it in this corridor where strikes were frequent outside the active SMAs. In essence, the SMAs are “spatially insufficient in certain seasons”.
Because the researchers only included records of animals found dead (either at sea or on shore) and not those found with serious injuries that most likely lead to death, actual mortality could be underestimated…and likely is – not all dead whales end up on shore, or float on the surface until spotted. Which brings up another point. Where the dead whales were spotted is not necessarily where they died (especially on shore). The researchers recognise this, but note that drift data dead whales that were struck by ships is limited, and that drift would differ with location, making it difficult to determine where the whales actually died.
The paper which was published in Conservation Letters , and has been made open access. You can have a read of it here http://dx.doi.org/10.1111/conl.12105
Image: North Atlantic Right Whale. Credit Florida Fish and Wildlife Conservation Commission/Flickr (CC BY-NC-ND 2.0)