I would like to share some background information on the equipment we need for this project, particularly the deep sea housings, accelerometers and lights. Hopefully this gives you a sense of how important these items are to our study and what role they will play in answering our research questions. The first of this series of lab notes will focus on the accelerometers and their housings.
Accelerometers and Housings
Your smartphone somehow knows which direction is up or down when you're playing a game or rotating it to better view a photo. Accelerometers are the little chips inside that keep track of this 3D orientation and tell it how to adjust the image on the screen.
For ecologists, accelerometers can provide insights into animal behavior. Here is an image of the one we'll use for some sense of scale.
The devices are capable of logging directional acceleration values in 3D space at very fine scales (every second for 6 hours). Researchers have primarily used them to document unique animal behaviors in space and time by coupling them with video analysis or visual observation.
As an example, imagine a goat moving across a square pasture. The goat would feed on grass in some places, rest in others, and move in between. Each time the goat changes behaviors, its body moves in different ways. An accelerometer on the goat's neck could record these movements for later download.
At the same time, researchers nearby could watch the goat and record its unique behaviors over time (e.g. feeding, moving, resting). After catching the goat and downloading the accelerometer data, they could match the observed behaviors to the accelerometer values and map behavior over time. Then, since they would already have the movement signatures that correspond to given behaviors, they could simply deploy the devices and leave. They wouldn't need to record behaviors visually because they could assign them afterwards!
To take the example a step further, imagine attaching a satellite collar with an accelerometer around the goat's neck. Adding the spatial component would allow the scientists to map certain behaviors over both space and time, and allow them to pinpoint critical feeding grounds in the pasture.
How will we use accelerometers?
We will attach our accelerometers to the fishing line right above the hooks. Instead of looking for specific behaviors, we will be taking the sum acceleration in all dimensions for a measure of activity and energy expenditure. Furthermore, the internal clock will tell us when an animal is hooked and allow us to determine the effects of capture duration on their condition at the surface. This is really important, as capture duration could greatly affect the risk of mortality post-release.
The housings are waterproof and custom-built to withstand the extreme pressures at 1000 meters down (100x greater than at the surface). The designs were made by folks at Blue Turtle Engineering, LLC, who also helped create the baited video unit that first filmed a giant squid last year!
Thanks for reading and for your help with the campaign! The next post will describe the lights, which were just officially named "Lanternfish".