Revelle: Breaking Undersea Waves Make Fish a Sandwich

T_Tide_Logo_2015It’s never good news when the phone rings in the chief scientists cabin. It was 7:30 am on Tuesday. We had just lost electrical communication with our Fast-CTD fish. I arrived on the fantail to find the worst-case scenario unfolding. Fifty meters of wire were being coiled on the deck. There was no instrument on the end. The fish and 800 m of wire were lost.

It didn’t take long to see what had happened. Nearly 20 m of the cable was filleted by razor sharp cutters (Figure 1). Then a few meters of undisturbed wire…. then “Chomp”!


SharkBite 1



About  once a cruise we have a deep encounter with a shark or big fish (Figure 2). Our recent cruises have been in the South China Sea or in equatorial waters, where sharks are expected. Only the depth of the encounters has been a surprise. Our old fish design had a lead nose, which over time got decorated with the gouge marks of sharks teeth (Figure 3). Once we brought up a tooth stuck in the lead. Off Tasmania, in the “Roaring Forties”, the waters are surprisingly warm, due to the south-flowing East Australia Current. As the local surfers confirm, there are sharks here too.

Figure 1. A close up of roughly 20m of “flossed” cable.

We were profiling between 1300 and 1900 m when the incident happened. “Bruce” (Nemo, Finding, W. Disney Inc, 2003), while swimming through the blackness at around 500 meters depth, apparently bumped into our wire. The instrument was near the top of its profile, 800 meters below. He struck at the moving wire, using the first 20m to floss his teeth. Then he bit down hard.

Crash Guard Before Bent Crash Guard II

Figure 2. The nose of our 2012-vintage Fish showing the orange micro-conductivity cell, before (left) and after

(right) an encounter with a UFO (Unidentified Fishy Object).

It’s tough when you lose an instrument. In over forty years of playing this game, well over 100 thousand profiles, we have previously lost only one CTD. It’s part of the cost of doing business in field science, and the cost unfortunately is getting to be quite high. The value of this instrument is equivalent to the operational cost of our ship for roughly 12 hours.

Close-up Chomp mark

Wasting time bemoaning lost equipment is expensive too. By 11 am we were ready to go again with our back-up CTD fish, using an old, well-worn, cable from a previous experiment. Hopefully we’ll learn a lot more about ocean mixing & no more about sharks as the cruise continues to unfold.


Figure 3. When the lead beneath the black tape is deeply gouged and there is a matching gouge on the opposite side of the fish, you know that you’ve failed the Bruce taste-test.



Rob Pinkel