2017 Spring Bottom Trawl Survey

Leg I: Fast Prey and Slow Predators

All photos in this post by NOAA/NEFSC Wesley Rand

One of my responsibilities as part of the scientific party on the Bigelow is to open animals’ stomachs to see what they have been preying on. I had a couple of interesting finds today.  I didn’t know these predators were capable of catching what I found in their stomachs!

The first find is something we are seeing pretty regularly, and that is winter skate (below,top two panels) with spotted hake (below lower panel) in their stomachs. If you just look at the two fish, you wouldn’t think skates could catch hake.Notice that the skate’s mouth is on its underside and not in a particularly maneuverable place. Pure speculation, but maybe the hakes rely on hiding in the ocean’s bottom instead of swimming away to avoid predators?  If that were so, skates could easily suck them up when they hiding in the mud or sand.

The second find of the day was something we had not yet seen on this trip; a fat spiny dogfish with a whole Atlantic menhaden in her stomach.

spiny-dogfish_opt

Spiny dogfish female we examined, with a full gut.

The menhaden was about 8 inches long and almost perfectly intact! Atlantic menhaden, commonly known as bunker or pogies, are fast-swimming, schooling fish. Spiny dogfish spend most of the time on the ocean floor and aren’t known to be the fastest swimmers, but I’m sure if one swam into a big bait-ball of menhaden, it could nab one.

mature-menhaden_opt

Atlantic menhaden, spiny dogfish victim! 

It’s all just conjecture, but that’s one of the great things about being a part of this survey. You get to see things that are happening in the wild, like predator/prey relationships that challenge your view of the world.  When your findings contradict what you thought was possible, you have to think of new ideas to explain how it’s possible. The other half of the fun is bouncing ideas off of colleagues to see if they have any merit or if maybe there’s some part of the picture you’re missing.

Wesley Rand, fishery biologist

Aboard the NOAA Ship Henry B.  Bigelow

 

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