This portal tracks the research and sea-going activities of the Fisheries Engineering and Acoustic Technologies (FEAT) Team from NOAA¿s Northwest Fisheries Science Center. Follow us as we use acoustics, trawling, and oceanographic sampling to learn about the Northeast Pacific Ocean.
Sometimes, even after surveying thousands of nautical miles of the ocean (on this trip, and over the years), we see something that piques our curiosity. If weather cooperates, and we have time, we stop and check it out.
This morning, offshore of San Diego, was one of those times. The shallow layer was thick from the surface down to 100 m. What caught our interest (especially that of Chelsea and Chu) was the pattern across the frequencies – it was almost absent on the 18 kHz, very strong at 38 kHz, and then much weaker at 120 kHz.
We guessed that the layer was not fish given the frequency pattern, so opted to deploy the bongo net. This net has two 60-cm rings and 333 um (i.e. micrometers) mesh, so it’s good at catching small things. The bongo is lowered into the water and then towed toward the surface at a 45° angle.
When the bongo tow on our mystery layer was done, we looked into the jar and saw lots of little eyes looking back – larval fish! Given their size, these fish likely hatched from eggs less than two weeks ago. In the close-up photo you can see the distinct dark band on the tail and fins and the dark pigment near the eyes. We’re pretty sure these are larval hake, but need to get confirmation from an ichthyoplankton (i.e. larval fish) specialist.
The big question for us – if these are larval hake, where are the adults?