Blue crabs, as a species, happen to be the most valuable fishery in North Carolina. Unfortunately, their populations have been decreasing due to overfishing. Legislation has been put into place in order to allow the population to recuperate but progress is slow and little improvement has appeared. Because of this, research has been directed towards finding the reason the Blue crab population is not recovering and nursery habitats are thought to be the cause. One such crab habitat is known as shallow detrital habitat (SDH) and in order to determine how effective it is as a habitat for crabs I am asking two questions. Firstly, I need to formulate a testable, quantitative definition to find out what SDH is specifically and the characteristics that make it a good habitat for Blue crabs. Then I need to find out where SDH can be found along the coast of NC’s Pamlico sound. In order to thoroughly answer both of these questions we took our field work out into the sound using boats to go from marsh site to site. Multiple soil cores were taken and returned to the lab in order to compare the soil samples to known SDH soil cores taken during an earlier year’s field study. Using processes to measure wet and dry weight, grain size and organic matter loss on combustion, we narrowed down SDH characteristics. Then by determining SDH presence at certain sites we made a map of areas along the Pamlico Sound where SDH is present and marked them as important nurseries for Blue crabs.
Results/Conclusions
Fifty marsh sites were assessed and soil cores were processed to find a way to define SDH. Our results indicated that SDH is a spongy type of soil, with high water absorption displayed by the huge difference in recorded wet and dry weights. The soil typically contains high levels of large organic matter as well as smaller bits of silty soil. Grain size analysis supports these claims by showing root material and silt sized particles averaging 19 and 24 percent of the soil weight, respectively. To visualize SDH habitats, a map was developed to show high confidence areas for SDH presence, high confidence areas for SDH absence, and areas of uncertainty that may require more data. Refinements to this map are ongoing in an attempt to reduce areas of uncertainty for SDH presence or absence.