Here fishy fishy
There's an old joke among fish biologists: 'Counting fish is just like counting trees, except they’re invisible and they keep moving.' This quip, made by the fisheries scientist John Shepherd, is especially relevant when we're attempting to count fish in depths where virtually no light penetrates - they are literally invisible. And they keep moving.
We are trying to not only find the fish in waters deeper than 100 meters, but to figure out if and when they are spawning. To do this we need to also hear where the fish are. Our ultimate goal is to use lost cost, non-lethal methods to detect fish spawning in deepwater snappers and groupers. This is increasingly important, as our recent paper demonstrated that small-scale fishing has negatively affected their populations. We have also found that these snappers and groupers are incredibly long-lived, with some groupers having life spans of 100 years. The problem is that we don't know when and where they reproduce, or if they form large groups to spawn like many other species. If we can figure this out, then we can make more targeted recommendations to our partners in conservation and resource management.
Fortunately, we live in a time of rapid innovation and are no longer dependent upon ship-based, huge remotely operated vehicles to explore deep waters. This past year, we were able to get the band back together (Ivy and Sam) to improve upon our previous deepwater lander, and to add a hydrophone to the setup.
Although we have been largely successful with the design and deployment of the new deepwater BRUV and hydrophone setup, we had less luck finding the spawners this past year. We chose locations and moon phases that previously yielded spawning activity, but unfortunately none of the concurrently-captured fishes were found to be in spawning condition. We do now, however, have some baseline acoustics from which to measure future deployments and we got some great data on fish, sharks, sponges, coral, and hagfish!
Our work continues, and we are constantly improving the setup, lighting, and deployment options. This year we will increase the number of deployments and experiment with lander configurations designed to resist dragging and entangling. With every drop of the camera we see something that's never been seen before, and we look forward to counting more invisible fish, doing invisible things.
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