10 April Assignments: Abstract, Results, Discussion

Abstract

This project is a longitudinal study of the Uca minax fiddler crab species at Spermaceti Cove on Sandy Hook, New Jersey. The purpose of this study is to determine the status of the population, whether or not it is increasing, decreasing, or remaining stable. This has been done by repeating the same method over the past years, and will continue to be repeated in future years. Fiddler crabs are counted at Spermaceti Cove during full and new moon phases at low tides during late spring to early fall, the species' breeding season. After conducting statistical analysis of the quantitative data collected over the years, it shows that the population is remaining stable. As this is a longitudinal study, as more years of data are procured, different conclusions may be drawn by comparing all of the sets of data to each other.

 

Results

A correlation between the temperature of the counting day in Celsius and the amount of Uca minax fiddler crabs counted on both sides of Spermaceti Cove concluded that they have a slightly positive correlation of .31056. Evidentially, on a warmer day, more fiddler crabs will be spotted, as past counting sessions have shown (see Figure 1).



Figure 1: Above is a table of the date the crabs were counted, with the amount of crabs counted and the temperature in Celsius. It is shown that a higher temperature also yields a higher amount of fiddler crabs counted the majority of the time.

Mean, standard deviation, and variance of the 2016-2017 baseline data set and the 2017-2018 data set were calculated in order to determine the spread of the data. (see Figure 2).



Figure 2: This table breaks up the data from the 2016-2017 and 2017-2018 data collection sets, which are then further broken down into the amount of crabs counted on the North and South side of Spermaceti Cove during each counting session. Then the columns were totaled and the amount of crabs found on each side of the cove were averaged, which was then used to derived the variance and standard deviation of each set.

The variance of both years varied greatly between both sides of Spermaceti Cove. For example, the variance of the North side of the cove during 2016-2017 is 28,835.8, while the variance during 2017-2018 is only 5,586.5, meaning that the amount of crabs counted in the latter data set have values much closer together than in the 2016-2017 data set.

On the other hand, the difference in variance between the South side of the cove between both data sets is significantly less, with a variance of 48,062.8 in the 2016-2017 data set and 47,435.1. This means that the amount of crabs spotted on the South side were relatively close to each other each counting session. The same is true of the standard deviation between both sides of Spermaceti Cove, with a bigger difference of standard deviation on the North side than on the South side in both data sets.

The amount of fiddler crabs counted in the summer months, June, July, and August, of 2016 and 2017 were statistically compared using a t-test to determine the differences between the summers of both years. Using a t-distribution table,  the t-test number with an alpha level of .05 and 5 degrees of freedom should have been 2.015, not the 1.943 that was calculated.

 

Discussion

A correlation between the temperature of the counting days in Celsius and the amount of fiddler crabs counted on both sides of Spermaceti Cove exposed a direct relationship between these two variables; as temperature increases, there should be an increased amount of fiddler crabs spotted (see Figure 1).



Figure 1: Above is a table of the date the crabs were counted, with the amount of crabs counted and the temperature in Celsius. It is shown that a higher temperature also yields a higher amount of fiddler crabs counted the majority of the time.

The t-test provided evidence that the null hypothesis of this experiment cannot be disproven. This voids the hypothesis stating that the fiddler crab population at Spermaceti Cove would increase as the years go on. The population of Uca minax fiddler crabs at Spermaceti Cove on Sandy Hook, New Jersey shows no significant change over the years. The data collected in this study and the statistical analysis conducted on it backs this statement.

Further work is necessary to determine exactly why there is no significant change in population as years progress. One possible explanation is that the population of Uca minax fiddler crabs at Spermaceti Cove has already reached its carrying capacity, and no more fiddler crabs can thrive in the habitat due to the amount of resources, such as food and water, in it.

Longitudinal studies become more accurate as more years of data is collected. With more counting sessions each year, there will be more data points to statistically compare, making the conclusions more reputable. As the study continues, the conclusions conducted will become more accurate, as more years will be statically compared to each other.

Although the method for collecting data for this study remains the same from year to year, each year different people work on the study. This means that there could be slight variations in the way that data is collected, whether it be the counters being more negligible and careless when counting the crabs or not accurately recording descriptive data, like wind speed and direction and air temperature.