Materials and Methods

        This study was conducted over a seven day period at Whalebone Bay, located on the northeast coast of St. George, Bermuda.  Observations and samples were taken at random times throughout the seven day period.  During each trip to Whalebone Bay, an aerial photograph was taken of the bay to help locate the large school of baitfish.  Multiple photographs were taken each trip to help determine the distribution and the relative size of the school.  The photographs were also useful in monitoring the movement of the school as the day progressed.  They could be used to establish whether the school made any specific movements throughout the day on a regular basis.  A 5.2 mega pixel digital camera was used to take the photographs, so the resolution was high enough to clearly see the school of bait fish.   

                  

Figure 1:  The photograph above shows the method used to measure  the average length of the silverside.  The fish above is dwarf herring, which were also present in the bait school in small numbers.	Figure 2:  The picture above is Whalebone Bay.  The large black area is the large bait school observed on the first day of the trip.

        In order to determine the effects that predation and temperature had on the bait fish, I was required to enter the water.  The primary instruments that were utilized for this were: a 25 x 18cm fish net, a meter stick, a thermometer, and a slate.  Every 30 minutes, a total of ten silversides were caught using the fishing net and measured on a meter stick.  The lengths were recorded on the slate and later entered into an excel spreadsheet for analysis.  An average length was calculated for the fish to approximate the average size of the individuals in the school.  The distance between each fish in the school was approximated by eyeballing the number of fish lengths between each fish in the school.  A more accurate distance was obtained by multiplying the number of fish lengths by the average length of the 10 fish caught.  Furthermore, by swimming around and through the school of bait fish, the number of actively feeding predators was carefully observed and recorded.  The temperature of the water was also considered in this study to determine whether the movement of the school was in response to thermal changes in the water.  At 30 minute intervals, the temperature of the water was obtained from a thermometer and recorded on the slate.  The data was entered into an excel spreadsheet and the temperature values were plotted against the distance between each fish in school.