Sea lion vs. camera

Digging into the backlog of things I've meant to post, here is an excerpt of one of the videos from the fish diversity recordings featuring a curious sea lion trying to eat the camera...




As it swims off it goes right for the transect tape, which is why you see the tape move up into the camera frame. We've seen this kind of demonic intrusion before...

Does fish diversity matter?

Previous work out of the Witman lab has looked at how sea urchin diversity affects processes like grazing rates in the Galapagos. Now the focus is shifting higher up the food chain to the things that eat sea urchins. More specifically, does the diversity of urchin predators affect the intensity of predation on urchins? Are there interactions between the different urchin predators that may alter predation rates? My own project aims to figure out to what extent seastars such as Pentaceraster are a part of this predation. The other obvious suspects would be predatory fishes.

Whodunit.

To get some preliminary data on the diversity of fishes (with a special interest in species that could potentially eat urchins), we've been deploying a bunch of Hero GoPro cameras at multiple sites around the central Galapagos archipelago to record 3-4 hours of continuous video data on the fish that are present. These little wearable cameras were originally made for filming high-definition extreme sports videos, but work extremely well as our underwater data-collectors - we've made little stands for them that weight them down on the rock (usually we also stick a few rocks on the stand for greater stability).

Deploying the camera system

GoPro in its natural habitat

During our 5-day research cruise, we collected fish diversity data from 11 different sites, deploying 2 cameras per site for a minimum of 1 hour continuous video data per camera. Video data are easy to collect and accumulates quickly, but it will probably take many more hours in the fall and spring to analyse fish diversity from the raw data.

Here is a one of the more exciting excerpts from Rocas Cousins, a site on the north side of Santa Cruz. How many fish species can you spot? (If you're not too distracted by the charismatic trio of ray, sealion and turtle...)

Down to business

The general theme of our lab's research this summer is to elucidate the trophic (=feeding) structure of organisms that live in subtidal habitat in the Galapagos islands. For example, my project aims to figure out what the different starfish species are eating, and what is eating them, in order to establish their role in the food web. One of the ways we are doing this is using these little extreme-sports wearable cameras (with waterproof housings) to record video of starfish (or other study species) that are tethered within the camera's field of view. We can then analyse the video data to determine rates of predation on the starfish (or urchins, or whatever we're tethering) as well as what ate it. The GoPro cameras with extended battery packs are supposed to give us about 4 hours of continuous data.

The past couple of days has just been assembling these camera systems (and the stands) and testing them out to see how well they work, how much area/distance the cameras cover, etc. We've been snorkelling out around the dock in front of the marine research building of the Charles Darwin Station in Puerto Ayora. Here is a picture of a camera housing on its stand, weighted down by rocks. We were checking for stability and the watertight-ness of the housing on this round.

And this is me with the camera setup. I think I was sticking rocks on the base...or something. (Photos by Leslie)
On the way back from deploying the cameras, we ran into an marine iguana nomming on some Ulva (a green, sheety seaweed). I think I am starting to get used to the iguanas (hard not to when you're just about tripping over them every time you get out of the water...) but I still think they are the coolest things ever.