The bottomfish research expedition is progressing along nicely and the work is keeping the scientists very busy. The day begins early as the crew meet to discuss the day’s bottomfish sampling locations. The small boats are then deployed to commence pursuit of the “Deep-7” samples required, including the Hawaiian grouper “hapu’upu’u” and the six species of deep-water snappers (“opakapaka”, “ehu”, “onaga”, “lehi”, “gindai”, and “kalekale”). See previous bottomfish research expedition post: http://bit.ly/16BlZ3g. The team is bottomfish sampling at depths ranging from 100 to 400 meters and occasionally has to deal with the local shark populations, or “the taxman” as a Sette crewmen refers to them, snacking on the catch and creating disruptions.
Aboard NOAA Ship Oscar Elton Sette operations continue with bottom fish sampling and the periodic Isaac-Kid trawl modified for use on the surface to catch juvenile shore fish. Upon completion of bottomfish sampling operations and recovery of the small boats, the team then prepares for the next day’s work by tying lures.
CTD operations commence to obtain depth profiles of temperature, salinity, oxygen and chlorophyll content. This is accomplished by deploying a CTD, attached to a frame, and lowering it to the bottom of the water column. The CTD sensor measures conductivity, temperature and depth. Also attached to the frame are niskin water bottles. The water bottles are fired electronically from onboard at varying pre-determined depths within the water column. The water is then filtered and processed onboard the ship to determine water chemistry and chlorophyll content. These measurements will help to characterize the physical environment that pelagic stage bottomfish may be associated with and may lead to a better understanding of their environmental habitat.
The Cobb midwater trawling operations begin at night about 25 nm offshore around Johnston Atoll. The net is towed at depths of 170-175, 100-125 and 20-25 meters in search for pelagic stage samples. When the net is brought back onboard, the sample is weighed and sorted and the scientists spend hours delicately separating the catch. Once this is done we start the operations again. See next bottomfish research expedition post: http://bit.ly/1cI479t