Monday, 28 December 2015

My 2015 SMM conference experience report

Commentary by Sara Tavares

The Society for Marine Mammalogy (SMM) held its 21st Biennial Conference on the Biology of Marine Mammals 1 week ago in San Francisco, California (USA). The theme of the conference was "Bridging the past with the future", focusing on the past and future of marine mammal science in a changing world. This SMM conference was the biggest so far, with 1,536 abstracts submitted and over 2,200 registrants!

There were workshops, oral and poster presentations on a great variety of themes: conservation, distribution and abundance, behaviour, polar ecology, health, population assessment, ecology, climate change, acoustics, physiology, foraging ecology, human dimensions, population biology, genetics, biology, anatomy, evolution and education and communication. All the invited plenary talks were brilliant and very inspiring. Also, during the whole conference week there were a variety of art work in exhibit and special events to join.

SMM San Francisco City Hall birthday celebration (photo by Tomoko Narazaki)

Personally, it was my first SMM conference and I absolutely enjoyed it. It was overwhelming the size of the conference, with so many people attending and so many presentation sessions at the same time. But it was also great opportunity to see friends and colleagues, meet so many interesting scientist and discuss your work with others. We had the chance to choose which presentations to attend from a variety of highly appealing options of topics, species and locations around the world. We got to see fascinating research about orcas in various subjects from acoustics to interactions with fisheries and genetics.

Sara Tavares's oral presentation "The social structure of the Icelandic killer whale (Orcinus orca) population" at the 2015 SMM conference

It was very gratifying to be able to present part of my PhD study on the social structure of the Icelandic orca population. Thank you to the SMM organizers for making this such a great meeting of marine mammal scientistsThis was an amazing and fruitful experience  that I hope I can repeat in 2 years again!

Wednesday, 11 March 2015

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!