The herring

To better understand the orcas we also have to understand their environment and, specifically, what they are feeding upon. And in most places where we study them their main prey is an abundant silver fish: herring.

Photo by Filipa Samarra

Herring is the unsung hero of this ecosystem. It supports the whales; in groups the whales encircle schools of herring and using their tails they slap a bunch of herring that gets stunned allowing the whales to feed on it one by one. But not all the stunned herring is eaten by the whales, so when the whales are feeding some uneaten herring floats to the surface. Seagulls and fullmars are quick to catch these and take advantage of the whales' work.

Photo by Sara Tavares

Then there are the beautiful gannets. They wait until the whales have rounded up a nice ball of herring and then plunge the water in pursuit of some fish too. It is an incredible sound hearing a group of gannets simultaneously diving into the water. And we always wonder how they don't hit the whales and well...sometimes they do!

Photo by Sara Tavares

And of course there are also the sea eagles we see in the winter and the skuas we see in the summer. But it's not just birds, we also see white-beaked dolphins and seals in the area, which are probably also getting their fare share of the silver prey. And there's also all the unseen fish, like cod, preying on herring.

Photo by Leticiaà Legat

Photo by Miguel Neves

Photo by Marjoleine Roos

Photo by Sara Tavares

Although many different species can depend on herring, the herring itself is a tricky prey and this year we have seen how the herring distribution can quickly change. Up until 2014, there was a huge amount of herring overwintering in the fjords of Grundarfjörður and Kolgrafafjörður. But this year although the herring stock estimates indicate it is still quite a healthy stock, the amount of herring present in this area is much smaller. This is because the majority of the stock is spending the winter in the offshore waters further West. In fact the herring only started coming to this area in large numbers in 2006, following yet another shift in its distribution (see this study for more information). 


It is quite a mystery exactly why herring shifts its overwintering location. During winter, herring doesn't feed and it is mainly trying to avoid spending energy or being predated, and it often chooses coastal areas to do so. It is not possible to predict how long the herring will remain offshore or even what proportion of the stock will do so. It could be that in the winter of 2016, a large proportion of the stock once again travels to the fjords to overwinter, as it did in the last few years. 

Interestingly, it seems that it is during winter that the herring aggregates in higher numbers in relatively small areas. Throughout the rest of the year, the stock can be much more dispersed. And with the herring come the whales, so it is no surprise that it is in the winter months that we can see the largest aggregations of whales too. In fact, it is only in winter that some individuals can be seen around Iceland, as it seems that during summer they go elsewhere (see our post about matches to Scotland). So there is a lot that can be learnt about orcas by having the herring in accessible locations during winter, as only then can we follow the lives of some whales. 

So we keep our fingers crossed that this has been an odd winter, and that next year the herring return to familiar shores!

A whale not seen for 20 years!

We were amazed this summer when we photographed an adult male we didn't recognise and after some searching realised he had last been seen in 1994! Yes, 20 years ago! 9459 is the code it was assigned when first seen and added to the catalogue of Icelandic killer whales existing at the time. Since then it had never been seen again until our first day out in the water this summer. There he was, in a large aggregation of whales just off Geirfuglasker in Vestmannaeyjar.

9459 seen in Vestmannaeyjar.

This incredible sighting shows us some interesting things. First, it tells us he is an old male! Most likely he is at least in his 40s, since he was already a fully grown adult male when first identified in 1994. Second, it shows how little we still know about this population. Unlike populations in other parts of the world, there haven't been dedicated long-term efforts following Icelandic killer whales. Studies first started in the 1980s by the Marine Research Institute, but much of what has been studied about these animals since then has come from opportunistic studies or short-term studies, with dedicated effort for a few years.

Much of the difficulty of studying killer whales in Iceland comes with unpredictable changes in their distribution as they follow their herring prey which changes its location throughout the year and between years. And of course, many locations where whales occur are difficult to access or exposed to weather making working conditions, well, unworkable! This is why it is so important to have as much help as possible! Sighting reports from anyone out at sea that comes across killer whales makes it possible to understand which whales go where.

Of course some animals may be only occasional visitors in Iceland and so will not be seen for long periods of time simply because they are elsewhere. But we don't know if this is the case! Long-term studies and wide coverage make it possible to have an idea of the residency patterns of whales in Icelandic coastal waters that help us answer questions such as that.

And it is not just knowing the whereabouts of whales. By regularly following who is around we can better understand birth rates, mortality rates and we can even estimate how many whales are likely to live in Icelandic coastal waters. All this information help us understand if the population is doing well or is facing any threats. As top predators, these whales play a very important role in the food chain so knowing more about them is crucial to our understanding of the whole ecosystem.

Find out below how you can help!

Thank you team!

This summer we went back to the beautiful Westman islands. For most the weather was terrible in the Southwest of Iceland, but somehow on 'killer whale land' things seemed to work out! We had beautiful weather to start and to end our season but a variety of weather conditions in between. Yet luckily the whales changed their distribution throughout July and came ever closer to Heimaey, the island where we were living. In the last two days the whales were just hugging Heimaey's west coast (we could see them from the window of the house) and made for a spectacular sight to all the locals that went out to see it. It is not often you get such calm waters in Vestmannaeyjar as we had in our last couple of days (see video), what a nice way to say goodbye to this wonderful place.

The slow change in the location where whales were found made it possible for us to make use of short weather windows to go out in the water. Key to this was searching from Heimaey's weather station. This is the highest point on the island and it has incredible views over the southern part of the archipelago. It allowed us to check what the sea state looked like in different parts of the archipelago and, most importantly, spot where the whales might be! In fact going to the weather station to spot for whales was a daily routine and helped us make sure we could quickly get to where the whales were. Time was of the essence when high winds were fast approaching!

The team (David, Filipa, Gaëtan, Katy, Leticiaà, Paul, Sara and Volker) at the weather station looking at a passing humpback whale. A great place to see all the islands and spot whales!

Dr. Volker Deecke and PhD student Leticiaà Legat from the University of Cumbria joined us this summer and with them brought a towed hydrophone array. With this we were ready to multitask! We could use the towed array to make acoustic recordings while on the move following whales to get photographs for photo-id. Whenever possible we also attempted to collect skin samples which will be used for studies on the whales' diet, genetics and pollutant levels. The only thing the short weather windows did not allow us to attempt was tagging. This was because the tag, attached with suction cups, stays on the whale for a few hours during which we follow the whale to then recover the tag once it comes off and floats at the surface. But getting the tag on is anything but easy and so requires a longer day out in the water.

Despite the weather we managed to collect enough data to end with a very happy smile in our faces. But none of this would have been possible without the rest of the team: Katy Gavrilchuck, David Gaspard and Gaëtan Richard. Katy and David were the skilled skippers and Gaëtan helped with everything from acoustics to biopsy sampling. The next few months will be spent analysing all the precious information we collected and we will keep you posted on our findings. But in our memories will remain the good times we spent in Heimaey with a great bunch of people!

Thank you everyone for making this a fantastic field season!

Adult male surfaces with Heimaey in the background (photo by Sara Tavares).

 

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Week 1

It's been one week since we arrived in Vestmannaeyjar to start the summer field season of 2014. We arrived to stormy days but as we needed a few days to work on the equipment and Tango this gave us the time to be ready for the good weather when it arrived. And Sunday was the day! Beautiful weather, the kind you rarely get in this part of the world. Flat seas, blue skies, sun shining and no wind. Perfect!

Back in the beautiful Westman islands. The view from the top of Eldfell on Heimaey island, showing most of the other islands of the archipelago in the distance.

We started heading West to where we had seen killer whales in previous years while the land team was searching the area southwest of Heimaey, all the way to Surtsey, where we know the whales are seen regularly too. This way we covered most of the area where we were likely to find them. After about 2 hours of sailing and searching we get the call from the land team: whales near Geirfuglasker. We were close so it was perfect timing!

Herring laying at the surface of the water (after being stunned by the whales tail slaps) is snatched up by the many seabirds flying above feeding whales.

When we arrived we saw this was a large aggregation of whales and we stayed in the area the whole day. We recognised some individuals right away and particularly one whale which we knew only from a picture donated to us by one of the tour guides of the Viking Tours boat. Sighted in 2010, the whale we numbered IS118 was easily recognisable due to the shape of its dorsal fin. It was like seeing someone you know but haven't seen in a really long time although we had actually never seen him ourselves! What an amazing sight!

IS118 seen in Vestmannaeyjar.

It was a perfect day that ended with an unexpected sighting of pilot whales! We had never seen pilot whales in these waters and talking to some of the locals they had neither, so it was quite a rare event. We saw a group of about 12-15 individuals swimming fast, but the report of one of the Ribsafari boats suggested there was another group also swimming fast nearer to Surtsey so there may have been different groups in the area. We didn't stay for long as we had to start heading home but we still managed to grab some pictures of this unusual sighting.

Over the next 2 days the weather got progressively worse but we still managed to work for half a day on both days. The whales have been consistently in the same general area and it looks like it has been mostly the same groups that are around. Week 1 has been eventful and we have been extremely lucky to find so many whales and get so much done already. We will keep you posted how the rest of the month progresses and in the meantime keep our fingers crossed for good weather and plenty of whales!

Keeping an EAR on the whales

In the last winter season sometimes it really felt like the whales were playing tricks on us! One day we went early in the morning for our daily morning check to see what the weather looked like and whether there were any whales in the fjord. As soon as we arrive at the viewpoint, perched high above the inner part of Kolgrafafjordur, we spot the whales! The weather however is not good so we can't go out, but at least we can try to photograph them if they come close to shore, for example to go under the Kolgrafafjordur bridge. We come back home to tell the rest of the team what the plan is, fetch the photo-id camera and head back to the fjord. The whole round trip must have taken 15 minutes, we go back and the whales are gone! This happened not just once but on a few occasions.

The view from Kolgrafafjordur viewpoint. In the centre you can see the bridge separating the inner fjord from the outer part of the fjord. A great place to spot the whales!

A common sight last winter: people waiting at the bridge for the whales to go under. It did make for a spectacular show particularly when the whales had to cross against the strong current.

Luckily this year some of the hard work was done for us. Better yet, we could keep track of the whales for 24 hours a day and even in stormy weather! We had an autonomous acoustic recorder called the EAR (Ecological Acoustic Recorder). Thanks to Dr. Marc Lammers, from the Oceanwide Science Institute, we deployed an EAR in late February on the inner part of the fjord where the whales spent most of their time. It stayed in the fjord for more than one month, recording the sounds in the environment for 5 minutes every 10 minutes. This meant that by the end of the season we had more than 400 hours of recordings to go through! But because the EAR was there for such a long time it provided us valuable information about when whales were present in the inner part of the fjord, as long as they were producing sounds.

Deploying the EAR buoy

400 hours may sound like a lot, but going through all these recordings has been fascinating. We have learned that the whales came to the fjord to feed often during the night! This type of information would have been impossible for us to gather with our usual methods, as we cannot work during hours of darkness.

But it is not like the whales were only feeding at night. Or for that matter it's not even like they would be there every night. So what is it that determines their choice of when to go feeding in a particular area or when to leave? Our photographic records seem to suggest that the whales may come to the fjords for a few days but then leave and only come back a few days (or weeks) later. Where they go in the meantime is unknown. But it certainly looks like they are constantly on the move!

It is not uncommon for killer whales to move around. Our recent post about the movements between Iceland and Scotland is a testament to just that and long movements are known also in other populations. But we are still far from understanding the finer details of what drives killer whales to move between areas or to temporarily leave what seem to be good feeding grounds, as they do in Iceland.  

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