Well we have made a lot of progress up the Caribbean coastline of Central America, following some of the more interesting physical features northward along the coast and eastward off the shelf. As we found Atlantic Bluefin Tuna Larvae during last year's cruises along the Mexican coast, this year's cruise involved an extend period during the first two legs for exploratory sampling in the Caribbean. The purpose of Legs 1 and 2 were used to sample as much of the Caribbean indicated as positive and negative habitat by the larval ABT (Atlantic Bluefin Tuna) created by the NOAA SEFSC Early Life History Lab.
The sampling routine is maximized to cover as much area as possible using Neuston nets to sample the surface, and fish another Neuston net with slightly larger mesh up and down between the surface and 10 meters, and in areas that show the promise of ABT larvae using a MOCNESS to get depth stratified samples to give us an idea of where in the water column we are finding ABT. To give you an idea above is an image of a larval scombrid, taken through the microscope. This is not a Bluefin larva but it is similar to what we are looking for.
Although chances are that there may have been ABT larvae present in our samples during leg 1, the scientists from ECOSUR and the ELH at SEFSC, had not found any scombrid larvae that could positively be identified as ABT. It may be that some of the scombrid larvae found during the first leg were simply to small and the samples too large for positive identification to be made at Sea. However as we moved farther north and crossed into Mexican waters we have tentatively found positive stations for ABT again. Though not unexpected this provides positive reinforcement of last years results and the possibility of depth stratified sampling, with the MOCNESS, in the areas where we find the larvae. But getting a sample with a small larval ABT in it is something of a reason for celebration, only for a couple minutes though then we get back to work as the clock is ticking towards the end of leg 2!!!!!!!
Next stop Key West, Woo Hoo!!!!!!!!
For any confused about the sampling terminology used in this post see, the early post about the MOCNESS, and last years post about sampling gear.
Sennai
