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Shark bytes – EEA 2018 conference summary

This past weekend the European Elasmobranch Association conference was held in Peniche, Portugal. The Saturday started with a talk by keynote speaker Gavin Naylor, on the chondrichthyan tree of life.

He noted that sharks have been around for a long time, and during this time have evolved some pretty cool traits such as the ampullae of Lorenzini. However, a lot is still not known, like how did all these cool traits evolve? He set out to create a database containing information about as many species as possible, so comparative work can be done to answer that question. The database can be found on www.sharksrays.org and contain an evolutionary tree with divergence times of different species, range of species across the world and printable field guide of species selected by area.

Also CT scans of representatives of each family with which you can do a digital dissection, comparative anatomy, or make a  3D print are available. Eventually he would like to answer the question of how highly organised structures seemingly sprout out of nowhere. Julia Türtscher continued on the topic of evolution, doing geometric morphometrics (size comparisons) on teeth of extinct tiger shark species. Based on the tooth morphology, out of the 23 tiger shark species, 6 turned out to be invalid and 9 were reassigned, leaving 8 tiger shark species!

The day continued with Marisa Vedor who looked at the diving behaviour of blue and mako sharks in Oxygen Minimum Zones. Both species were keeping to shallower waters in the OMZ, changing their diet with it. Staying in shallow waters will leave them more vulnerable to longliners.

James Thornburn also discussed spatial ecology, in this case of tope sharks. He found females preferring higher temperatures, but at the same depth as males, implying sexual seggregation. The males also seemed to synchronise their movements. Some sharks were real record-breakers, with Haley Dolton’s tagged basking shark making its way to Moroccan waters from the Isle of Man with a track of 797 days. Manuel Dureil’s tagged nurse sharks swam 250 kilometers, crossing waters of over 2000 meters deep.

A number of talks were about the accumulation of heavy metals in sharks. Paulo Torres noted that sharks are good heavy metal scouts, finding heavy metals in both liver and muscle tissue. Alba Martín-Lázaro found that the parasites on sharks can concentrate heavy metals in their bodies, which would make having parasites potentially beneficial to sharks.

On Sunday, several novel techniques for data collection were discussed. David Ruiz-García used a blimp with camera to study the movement of two stingray species, finding them moving unoriented when encountering drift algae and humans. Ana Sobral collected photographs of mobulids taken by divers over the past years, concluding that photo-ID is a valuable tool to study their populations. Joanna Barker developed a new tagging method for angel sharks, allowing them to tag while underwater and take a genetic sample while tagging. J. Fontes used a harness with a towed multisensor package to study deep diving sharks and rays. The harness erodes and releases the entire package.

Some DNA studies were done too, with Laurent Duchatelet isolating microsatellites of two deep-sea bioluminescent lanternshark species, showing multiple paternity in litters and within uteri for one of them. Fenella Wood showed that eDNA can be used to identify angel shark nursery sites.

All in all it was a conference with some very high quality research shown, and luckily we didn’t lose any scientists to hurricane Leslie!

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