Island Sentinels: Sample Analysis
The Island Sentinels program, led by FIConservancy naturalist Justine Kibbe, works to establish a database that encompasses a wide range of observations, which are gathered across twelve sites on Fishers Island. The data includes, but is not limited to, wild life sightings, the presence of marine debris, the varieties of seaweed, the changing water and air temperatures, the various mollusk and crustacean populations, the abundance of sea vessels, and the general seasonal changes year to year. The ability to ask questions that cover a wide range of subjects and answer those questions using already collected data is a significant benefit of noting such a broad range of observations. For example, if a threat against the seagull populations develops, a recorded history of the seagull population on Fishers Island, NY, over several years could be found in the database. The following document uses data collected by Justine Kibbe and individuals in the Island Sentinel Program, from 2012-2016, to establish a better understanding of the local history of the island.
HARBOR SEAL POPULATION: SAMPLE ANALYSIS
The harbor seal population that returns each late summer-early autumn is a noteworthy species of the island. Over the past few years, the window of their arrival time has ranged from September 2 through September 27, typically occurring near the end of the month. Their departure from the island has ranged from April 4 through April 21. The following table displays the average high and low numbers of seals counted off Hungry Point for 2012-2016 (Fig. 1). It should be noted that the seal count was observed from land, which at times may have limited the view of the entire population of seals present.
Average High and Low Count of Seals at Hungry Point 2012-2016
The highest recorded number of seals, 198 seals, was observed in December of 2015.
Examining the highest recorded number of seals is important to consider because the number of seals fluctuates frequently day to day depending on the tide, time of day, and other various factors. By looking at the highest number of seals counted each month, a better understanding of the typical size of the population is gained. The following table displays the highest count of seals for the months September through December of 2012-2016 (Fig. 2). To determine potential factors that contribute to the changes in seal population counts, the relationship between populations and temperatures was examined. Figure 3 displays the average low temperature for September through December from 2012-2016. The data indicates that as temperatures decline, the seal population increases. This trend is easy to see in 2012, 2013, and 2016 (Fig. 2 & Fig. 3).
Additionally, it was hypothesized that the tide schedule influences the number of seals. During observation counts, it appeared that more seals were present at low tide. To examine whether or not this was valid, the relationship between the average number of seals each month and tide was compared. It was found that the average number of seals (where there is sufficient data) from 2012-2016 is higher at low tide than at high tide (Table 1). Despite the changes, the data is only significantly different for the month of April (p-value=0.027).
Table 1. Displays the average number of seals counted at East and West dumplings from Hungry Pt., Fishers Island, N.Y. at high and low tide (2012-2016).
RECREATIONAL FISHING BOATS: SAMPLE ANALYSIS
Due to the importance of maintaining healthy seagrass meadows around Fishers Island, the Island Sentinel Program included the counting of recreational fishing boats, especially off the south side of Fishers Island, during 2013-2016. From the graphs, it is clear that the presence of power and fishing vessels drastically changes month to month, a trend that has been observed consistently over the years (Fig. 4). In the summer months, June, July, and August, exists the highest presence of vessels, with an exceptional number of vessels observed in July (Fig. 5). It should be noted that the amount of days that observations were taken, which varied, affects the number of total vessels seen each month. However, there still appears to be an increase in fishing and power vessels in the summer months. For example, on some summer days, counts will reach the 40’s for a single day at a one location.
The data collected by Justine Kibbe and the Sentinel teams covers a wide range of topics that are important to note when creating a report of the natural history of the island. The recreational fishing boat analysis and Harbor Seal analysis are two examples that provide insight into the many ways in which the data can be used to establish a better understanding of the island. The ability to study the island through various lenses is credited to the current data collection that invites a multitude of scientific questions.
Compiled by Olivia Backhaus, December 2017.