As The Discovery Channel played the last episodes of Shark Week for the public to watch, hundreds of scientists joined in New Orleans to discuss their science at the centennial Joint Meeting of Ichthyology and Herpetology. There were so many fantastic presentations at this meeting but here are just a few of my favorite marine-related talks for the Ocean Bites crowd!
Keynote speaker- Sylvia Earle “Exploring the Deep Frontier”
Sylvia Earle is a world-recognized scientist and leader in marine conservation efforts. It was an incredible honor and joy to be in attendance to see her speak and she had an important message to deliver to the scientists in the room. Our oceans are in peril. As the human population grows, we are causing animal populations all over the world to decline. But right now not all is lost – we are at the point where we can make the decision to make a change and save the species we have imperiled. It is our job as scientists/ nature enthusiasts to stand up and protect the natural world. For as Sylvia said, “If we fail to take care of the natural world, nothing else matters”.
If you want to learn more about Sylvia Earle, I encourage you to watch “Mission Blue” (on Netflix) and to support her effort to protect the oceans by looking into her initiative to create “Hope Spots”.
Sawfish Conservation: As Sylvia pointed out in her opening talk and as many previous ocean bites posts have discussed, sharks are on the list of animals we have severely decimated. There was an entire day-long symposium on what we know about the conservation of a highly endangered group of elasmobranchs (sharks, skates, and rays): Meet the Sawfishes (Fig. 1).
These shark-like rays are known for their snout that looks like a sawand is covered in teeth-like projections (they are actually modified scales, not true teeth! – discussed by Monique Welten) that are used to catch fish. They are some of the largest elasmobranchs (some can reach up to 23 feet long!) and are also the most threatened of marine fishes, with all species being listed as endangered species. This is in part because of habitat destruction but has also been caused by human exploitation and because they make up a large portion of bycatch in fisheries
Because of their vulnerability and status as endangered species, scientists cannot easily study their behaviors in a lab. Kara Yopak is studying how sawfishes might behave by looking at their brains. By comparing the brain size and overall appearance (for example the relative sizes of different parts of the brain)among species of sharks, we can gain insight into what type of habitats sawfishes live in, what sensory systems are important to them, and how active they are. Interestingly, this work has led to the finding that in sawfishes the region of the brain responsible for movement is similar to that of the thresher shark- the shark that uses its tail to catch its prey. This comparative approach continues to reveal exciting aspects of shark biology, ecology, and behavior!
Sonja Fordham gave a talk about the history of sawfish conservation. Some sawfish species were listed on the Endangered Species Act in 2003, but it wasn’t until 2013 that all of the species became listed and protected (16 years after the initial attempt to protect these animals). Even with their protected status, sawfishes are still in danger. Shrimp fisheries in Florida catch these animals as bycatch (as do other fisheries not mentioned in this post), humans mishandle sawfishes they encounter, and their fins and saw-like rostrum are still being traded as trophies. Dean Grubbs added a hopeful note to this bleak situation. Since the establishment of protected lands in Florida, we have seen a possible range increase for the sawfishes, meaning they may be rebounding. And the continued work by scientists has led to potential discoveries of mating and breeding grounds that will aid in sawfish conservation. However, it is obvious these fishes still need our help. If you would like to know more about sawfishes and how to get involved, visit the Sawfish Conservation Society website.
There were a number of other fantastic talks on the biology, ecology, and conservation of different shark species but I just wanted to leave you with one more that blew me away. Vera Schluessel “Sharks don’t just have Sharp Teeth but also are Sharp Thinkers- Cognition in Elasmobranchs”. Schulessel’s lab at the University of Bonn focuses on the cognitive ability of sharks. They have trained sharks and rays in their lab to discriminate objects and are using this to determine the bounds of shark cognition. Essentially, they ask the shark/ray to decide between two pictures- one receives a food reward. Once the shark has learned which object will be rewarded, the scientists can swap out the “trained” image with other images of the same object to see if the shark can still distinguish between the images. Sharks were able to distinguish between shapes (i.e. pick the triangle over the square), between a fish and a snail (ANY image of a fish vs. any image of a snail), and between symmetrical vs. asymmetrical objects (Fig. 2A).
Then the scientists tested the ability of sharks/rays to discern optical illusions. Sharks weren’t fooled by Muller-Lyer illusions (Fig. 2B) or by Ebbinghaus Illusions (Fig. 2C). Furthermore, the sharks could distinguish between different movement patterns (like the difference between a fish or dolphin swimming pattern), objects moving at different speeds, and could even distinguish between quantities! If given two images with a different number of objects in each, the sharks could pick which image had the most/fewest objects (Fig. 2D) as long as there was a difference of two or more between the images (i.e. give a shark an image 3 dots and one with 6 dots and it could tell determine which image had the most dots but give the shark an image with 3 and 4 dots and it had a hard time). I think this highlights the lack of understanding we have about sharks (and other animals for that matter), how much more we have to learn about them, and how incredible and smart these animals are.
Because this is not just a Shark conference, and sharks are fish after all, I wanted to share a few brief tidbits from some of my favorite fishy talks as well.
Bethany N. Coffey and Timothy C. Tricas: “Context Clues: changes in vocal behaviors of triggerfish between interactions with conspecifics and predators”. These odd-looking coral-reef fishes make sounds! And lots of them. This may not seem that exciting but the sounds are made as a form of communication. Using their modified teeth the fishes make several different sounds and also rub a spine on their fin against their body, creating two different drumming sounds. Most of these sounds were only made when a predator or another triggerfish (conspecific) was present and the sounds produced were different depending on if the fish was near a predator or a triggerfish. This implies that triggerfishes are using sounds to communicate with predators or other triggerfishes!
Leo Smith, Jennifer Stern, Matthew Girard, Matthew Davis – “Phylogenetic and Anatomical Diversity of Venomous Cartilaginous and Ray-Finned Fishes”
You probably know of a few venomous fishes- the stingrays, lionfishes, and the very toxic stonefishes for instance, but the recent research by this team has increased our understanding of the diversity of venomous fishes. Previous reports had suggested that there were around 1,500 species of venomous fishes, however, Smith and colleagues have found that there are probably over 25,000 species of fishes that are venomous! It also appears that in the history of fish evolution, venom has evolved 18 separate times! There is an incredible diversity in these venomous fishes with several types of sharks (or other chondrichthyans) including the chimeras, batoids (or stingrays), horn sharks, and squalid sharks (i.e. dogfishes). In the bony fishes there are many more species of venomous fishes found in the catfishes, a group of deep-sea eels (monagnathids), toadfishes, stargazers, clingfishes, blennies, carangids (jacks and relatives), acanthurids (i.e. tangs- think Dory), and scorpaeniforms (the scorpion fishes like the stonefishes). Out of all of these venomous groups there are a variety of ways of dispersing venom- through spines on the fins, operculum, shoulder, or fangs.
These and many other talks and posters highlight the wonder of the natural world. To see more of the conference proceedings, see tweets on the talks by following #JMIH2016.