About

Sperm whale identification and research log (SWIRL) is a research project on male sperm whales (Physeter macrocephalus) off Vesterålen islands in arctic Norway, with the main focus on depredation (whales taking fish off long lines).

Male sperm whales are present in these waters year around and several studies on their identity, distribution pattern and behavior have been conducted from the whale center in Andenes, where a combined whale-watching and research center was established in 1989. The long term identification data forms a valuable baseline information for our studies and SWIRL is the current curator of the ID catalogue.

Sperm whales feed mainly in deep waters off the continental shelf. The deep water canyon (Bleik Canyon) which ends only about 8 nm from the coast, has long been known to be a feeding ground for sperm whales and is also the area where sperm whales have mainly been studied since 1989. 






 

- Bleik Canyon -

Since 2010 there has been a change in the distribution pattern of sperm whales, where the whales are also found in shallower, coastal waters in addition to the deepwater canyon. This change is probably related to a change in prey abundance, distribution – or both, and one of the aims of our project is to analyze fisheries data for a better understanding for changes in the ecosystem. Sperm whales, like other marine mammals, are good indicator species of ecosystem changes – since changes in their distribution and behavior are easy for us to observe.

Part of the new feeding grounds for male sperm whales overlaps with an area where traditional long line fishery for Greenland Halibut (Reinhardtius hippoglossoides) operates. The Greenland Halibut spawns on the continental slope during summer and the fishery takes place in June and August. In August 2014 first observations of sperm whales taking Greenland Halibut from the fishing lines were made and these observations continued during the fishing season in 2015 .This behavior, called depredation, has been well documented for sperm whales and other toothed whales elsewhere and has caused significant economic loss for fisheries. Depredation is a behavior that spreads in the population through learning and therefore this novel behavior of sperm whales off Vesterålen islands can escalate to a problem for the long line fishery and our aim is to work together with fisheries to mitigate this problem.

A pilot study was conducted during summer 2016 using fishing boats as observation platforms to document sperm whale behavior and to obtain identification images of the whales interacting with the longlines (Similä et al 2017). Eighteen depredation events were registered and five different sperm whales were identified, two of which have been previously identified in the area. These numbers do not represent the scope of the problem or the number of individuals involved, since data was collected in an opportunistic manner.

The sperm whales could be seen approaching the vessels while the line was set, but waiting in a distance. They started approaching as the line was hauled in, lifting the front of their head out of the water while approaching to get a more accurate estimate of the distance . The whales stayed for the length of the haul-in process (up to two hours) with several shallow dives close to the line. The male sperm whale who was first observed depredating from the long lines in these waters (august 2014) was observed on at least five different depredation events in 2016. This whale as well as two others observed interacting with the longline have not been previously identified in the study area, suggesting that specialist "depredators" are being established in the area. Depredation events of between one and three sperm whales per long line were reported. Based on comparisons on catches with/without sperm whales, fishermen estimated between 30 and 50% loss of catch to the whales.

Although no direct observations of how the whales caught the halibut could be made, the fishermen reported that there was always a length of the line with no fish, suggesting that the whales have developed a technique where they take several fish at “one go”, possibly using their lower jaw as a tool. One Greenland halibut was taken onboard with sperm whale tooth rakes on the body.

Interaction with the longline is not without risk for the whales. Entanglement has not been reported, but stomach contents of 9 out of 22 sperm whales found stranded in the North Sea contained marine debris, including a longline and a hook (Unger et al. 2016) as well as other fishing gear.