The NOAAS TOWNSEND CROMWELL is now heading toward Honolulu having completed two oceanographic transects in support of bigeye tuna research. Despite a few mechanical and electronic challenges, we accomplished the mission and gathered a lot of data.

Researchers are interested in the productivity and oceanography of areas that commercial fisherman catch bigeye tuna. We conducted CTD casts and collected water samples along two transects west and south of the Hawaiian Islands. 
The area of the Bigeye Tuna transect (figure 1) had less chlorophyll in general in the near surface waters (0-200 meters) than did the transect farther south.  The temperature change with depth (thermocline) was gradual and the nutrient rich cold water was several hundred meters below the surface where sunlight does not penetrate. Toward the south of this transect (the left of the figure) the colder waters are closer to the surface, the thermocline is more abrupt, and there was an observed increase in chlorophyll at the boundary between the warmer and colder water.

The second transect which crossed through the North Equatorial Current (NEC) (figure 2) shows a strong thermocline and colder nutrient rich water closer to the surface all along the transect. The chlorophyll concentrations in this area are at least two times higher in the surface waters (0-200 meters) than in the waters to the north of 14 degrees latitude. These higher chlorophyll surface concentrations are readily monitored by ocean color satellite sensors and the data obtained from this cruise will be used to confirm and better interpret the satellite information.

After steaming for two days toward home port, we are still 300 miles from Honolulu. We will stop at night to tow the Isaacs - Kidd midwater trawl at the depth of the thermocline to test the real time depth and temperature sensor we attached to the (IKMT) net. Our aim is to target a certain depth to sample the biological community associated with that depth.

Update from 4/25/01

Last Modified 4/25/01

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