Norwegian killer whale project - NORCA

The Norwegian killer whale project (NORCA) was established in 1987. This project has been previously coordinated by Dr. Tiu Similä and consists of a network of students and scientists working on different aspects of behavioural ecology and population dynamics of killer whales in Norwegian waters.

The main prey type of killer whales in the Norwegian waters is the Norwegian Spring-Spawning (NSS) herring (Clupea harengus). Herring migrated into Vestfjord and adjoining fjords in Lofoten to winter between October and January for approximately two decades. Up to an estimated 700 killer whales followed herring into this area. During recent years the NSS herring stock has changed its migration pattern and is now wintering outside the fjord system in the open ocean, North and Northwest of the Lofoten islands.

Most of our field work has been done during November and December, battling with the poor light conditions above the Arctic Circle. Photo-identification forms the basis of our field work. We currently have about 600 identified individuals in the photo-identification catalogue of Norwegian killer whales.

Previous studies

The main focus of Tiu’s studies was on the behavioural ecology of killer whales with special interest on feeding behaviour and predator-prey interactions. One of the most exciting findings of Tiu's was the underwater observations of a specialised feeding technique of killer whales, called carousel feeding. During carousel feeding killer whale group, in close cooperation with each other, chase the herring school into a tight ball formation close to the water surface. The killer whales then slap the herring school strongly with their tail and stun the herring. After this, it is easy to eat the stunned herring one by one. Carousel feeding event can be recognised above water sometimes by the jumping herring, huge gatherings of birds and by the killer whales swimming behaviour and their often high arched dives. Although carousel feeding might seem chaotic above water, it actually looks like a very delicate killer whale ballet underwater.

Another highly interesting study was done in 2000 and 2001 when altogether 7 killer whale individuals were equipped with satellite tracking instrument. One of the main aims of this study was to investigate interactions between killer whales and the Norwegian spring-spawning herring on a daily, seasonal and yearly basis in the Norwegian Sea. The satellite tracks showed killer whale movements following the migration patterns of NSS herring and also gives an insight to how killer whales keep on track of their unpredictable prey source.

During 2005 and 2006 a new exciting study was done by Dr. Ari Shapiro and his team on movement and vocal behaviour of killer whales by using suction cup attached DTAGs. Movement sensors in the DTAG provide detailed 3D orientation and depth position information on the tagged individual, together with recorded acoustical data. Altogether 15 deployments of DTAGs were done on killer whales both inside Tysfjord and Vestfjord. Ari used these digital tags to explore the contributions of individual killer whales to group carousel feeding and the relationships between vocal and non-vocal activity.

Current studies

Current studies focus on population dynamics, acoustical and genetic studies in the area of the NSS herring wintering grounds. Estimation of population size, survival and calving rates of killer whales is based on the use of photo-identification and mark-recapture methods. Photo-identification is also used to study movement and area use of killer whales in relation to the changes  in NSS herring wintering distribution. Acoustic behaviour of Norwegian killer whales, especially during feeding events, is currently being studied and compared to Icelandic fish-eating killer whales. Population structure of North Atlantic killer whales is looked between Norwegian, Icelandic and Scottish killer whales using photo-identification and genetic samples collected from each location.


Field notes from Norway


During our field season in 2005 we encountered several killer whale groups in Vestfjord and also inside Tysfjord. Weather conditions were generally good but we also needed to spend a few days onshore due to heavy winds. The sailing boat Iolaire worked as a reliable platform for our work but was also accompanied by a rib-boat for a few weeks.

During November and December we continued photo-identification work both in Vestfjord and Tysfjord. Photo-identification works as a basis for all other studies done on Norwegian killer whales as in all studies we need to be able to identify the killer whale group we are working with. We also used a hydrophone array to study the acoustic behaviour of feeding killer whales, special interest was in carousel feeding events. The most exciting piece of research in 2005 was done by PhD student Ari Shapiro (Woods Hole Oceanographic Institute) and his team, where killer whale movement and acoustic behaviour was studied by using suction cup attached DTAGs. Shapiro with his team managed to tag 8 killer whales altogether in Tysfjord area during November. Results of this study reveal interesting aspects of killer whale diving and acoustic behaviour during carousel feeding.


This year we had two research teams working in the area but cooperating with each other. One of the teams was led by PhD student Ari Shapiro (Woods Hole Oceanographic Institute). His team was focused using DTAGs, towed hydrophone array and photo-identification to study acoustic and movement behaviour of killer whales. This work was a continuation of the studies done during the 2005 field season. Their team used the sailing boat Iolaire and rib-boat as their platforms.

The other highly international research cruise was led by Dr. Petter Kvadsheim (FFI) and Dr. Patrick Miller (Sea Mammal Research Unit). The objectives of the trial were to study impacts of low frequency (LFAS 1-2 kHz) and mid frequency (MFAS 6-7 kHz) active sonar on killer whales and herring, in addition to testing the capability of active and passive sonar systems for detection of marine mammals, in orded to mitigate possible effects of sonar or seismic sources, were tested. On this cruise, two vessels with two rib-boats were used as platforms. Together with photo-identification the team made behavioural observations of killer whales.

In 2006 we found most of the killer whale groups in Vestfjord and only on few occasions inside Tysfjord. This could have been an indication of a change happening in the NSS herring wintering distribution area.


In November our team worked using the sailing boat Iolaire as a platform, thanks to the generosity of her new owner Wilhelm Munthe-Kaas, who skippered her for the team during this period. We were covering the Vestfjord area and conducted photo-identification, acoustic behavioural and genetic studies, done by Sanna Kuningas, Filipa Samarra and Andy Foote. Sightings of killer whales were few and very widely spread throughout Vestfjord. Killer whales were mostly travelling fast in search of scarce herring inside the fjords. Additionally weather conditions were poor with several heavy wind days and we were forced to spend many days onshore.

During December the research team joined another research cruise lead by Dr. Petter Kvadsheim (FFI) and Dr. Patrick Miller (Sea Mammal Research Unit) on H.U. Sverdrup. The team conducted photo-identification work, used hydrophone array to help locate the whales and to do recordings. New tagging techniques were tested for DTAGs, LKTAGs and satellite tags. Only a few killer whale groups were encountered inside Vestfjord, Tysfjord and Ofotfjord and these groups were mostly travelling fast and in an unpredictable fashion. The new NSS herring wintering grounds North and Northwest of the Lofoten islands were also visited for a few days during calm weather. In these offshore areas we found large aggregations of many killer whale groups, together with fin whales and sperm whales. The offshore area is very challenging area to work during winter time when we are faced with extremely low light conditions and heavy winds. This year it was very clear that a dramatic change has happened in the NSS herring´s wintering distribution and its effect on killer whale distribution was also evident.


An international research cruise was conducted in May-June in waters around Lofoten and Vesterålen Islands, led by Dr. Petter Kvadsheim (FFI), as a continuation of the research cruise done in winter 2006. The objective was again to conduct natural behaviour studies, tag cetaceans with DTAGs and LKTAGs and study the impact of low frequency (LFAS 1-2 kHz) and mid frequency (MFAS 6-7 kHz) active sonar on their behaviour. During this cruise we encountered several killer whale groups outside Lofoten Islands, especially in Røstbanken area. One killer whale group, including a young calf, was also found inside Vestfjord.

During November, a few days were spent on a fishing boat offshore, approximately 60-70nm NW of Andøya Island, where most of the spring-spawning herring is currently over-wintering. During fishing operations several killer whale groups were seen feeding around fishing boats, taking advantage of easy herring catch falling from the nets. It was possible to see even four different killer whale groups at the same time within a small area. At this latitude (70N°-71N°) low light conditions significantly limit photographing possibilities, making it a challenge to identify individuals. Some photo-identification photographs were collected and additionally a video camera was used to film feeding killer whales.

While killer whale sightings offshore were frequent, there have been only a few killer whale encounters inside the fjord system during November and December this year. Those killer whales which enter the fjords travel quickly through the area looking for the now-sparsely distributed herring in the areas previous known as good feeding grounds. The fjord system has previously been the spring-spawning herring wintering area and a hotspot for killer whales during October-January. However, during the last two or three years we have witnessed a clear decrease in numbers of killer whale individuals and groups inside Vestfjord, Tysfjord and Ofotfjord.


Since 2008, NSS herring and killer whales have mainly been found during winter months in the offshore waters of the Norwegian Sea above 70°N. These areas are logistically very difficult to access in winter and practically impossible to do photo-identification work in. Over the last three years, part of the large NSS herring stock has been found inside Andfjord during December and January. Killer whales have also followed their migrating prey to this area and have been frequently encountered in Andfjord over the last three winters.

Photo-identification work of killer whales was carried out during January 2013 in Andfjord. In this fjord large numbers of humpback whales and also some fin whales were seen to feed on herring, side by side with killer whales. Dynamic situation with the NSS herring and the Norwegian Sea ecosystem keeps us on our toes once trying to predict how the next years will develop regarding NSS herring and killer whale distribution.










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