Abstract:
Bio 2 students at Florida Institute of Technology went on a seining field trip to the Indian River Lagoon. The Lagoon stretches about 30% of Florida’s eastern coastline and is extremely unique. The students used a 15m net at three different depths; knee-deep, waist-deep and neck-deep. After bringing the net to shore the students measured the length of all the fish caught and recorded it along with its species. This data was then used to create Histograms comparing length of fish to frequency of appearance. Shannon-Weiner indices were also created from this information in order to help calculate the biodiversity of the Indian River Lagoon.
Introduction:
The Indian River Lagoon runs for about 150 miles, from Ponce de Leon Inlet all the way to the Jupiter Inlet. The Indian River Lagoon is sizeable body of water that separates the barrier islands from the mainland (IRGS 2007). This river dominates about 30% of Florida’s east coast. The Mosquito Lagoon, Banana River and the Indian River Lagoon, together make up the entire Indian River lagoon system. The lagoon consists of three different types of ecosystems; wetlands, terrestrials and estuaries. The Indian River Lagoon is unique from any other estuary system and has great biodiversity. This is because of its “unique geographical location, which straddles the transition zone between colder temperate, and warmer sub-tropical biological provinces. Here, as perhaps no where else in the continental United States, tropical and temperate species coexist and thrive” (Smithsonian 2011). Biodiversity is the assortment of life in a specified habitat or ecosystem. In order to help understand the biodiversity in the Indian River Lagoon Students at Florida Tech spent a day seining and recording species of fish as well as their size. The Indian River Lagoon System is North America's most diverse estuary system, with more than 4,000 plant and animal species (Kinder 2005). Some examples of common fish species caught in the lagoon are: Mojarra, Spotted sea trout, Stripped Mullet, Bay anchovy, Silver perch, Atlantic pipefish, and Puffer. Because of the large size of the Lagoon nearly 1 million people live along or near the lagoon. (Davidson 2001). With the constant increase of people in and around the river, the river conditions have been steadily declining. Although the river still looks nice, it cannot compare to its original state. With seasonal seining data, the types and amounts of species can be recorded and compared with other seasons to track the effects on the marine wildlife in the river. The uniqueness and size of the Indian River Lagoon makes it a perfect candidate to be studied. The Brevard zoo does a similar study with 4th grade students. The zoo takes student to the lagoon where they sein the river and see what different species of fish they can catch they call it the Lagoon Quest. The objective of the quest is to “create a sense of pride and feeling of ownership and responsibility in children so natural treasures such as the Indian River Lagoon will remain healthy and vibrant.”(Brevard Zoo 2013). The Immediate goals of the Students at Florida Tech were to capture fish and record their species and size. Later, after repeating this process seasonally, comparisons could be made between the data groups. For this trip however a decrease in fish concentrations will be observed, the deeper the samples are taken. If you go farther away from the shore, then less nutrients or food for the fish will be available in the water, therefore more fish will be caught closer to the shore.

Methods: The Study took place at the intersection of US1 and Valkaria Rd in Malabar, Florida. The spot was on the side of the road with some trees separating the road from about a 5-foot beach. It was sunny with very little cloud cover approximately 80 degrees Fahrenheit. The water was very calm with very few waves. The seining net that was used was 15m long and 2m high with a mesh thickness of .67cm. This net was taken and dragged through the river at three different depths. First were knee deep, then waist deep and finally neck deep. Four students would go out with the sein at a time. Two would hold the poles close to the shore while the other two walked out into the river perpendicular to the shore. Once the net was stretched, both groups of students descended into the river until the group closer to shore was knee deep. Then the students would drag the poles through the river while keeping the net as stretched as possible. They would drag the net for approximately 100 paces. After 100 Paces, the deeper end would continue dragging the net forward while the shallow end stayed planted, causing the deeper end to swing around toward the shore. As the net became parallel to the shore, the students would then walk the net into the shore while pulling the poles together, closing the net. Once the net was on the bank another student would grab the bottom of the net pulling it onto the shore. Once all the net was drag onshore, the students would use their hands and small nets to grab the fish from sein net and put them into two large buckets half filled with water. After all the fish were put in the bucket, each fish would be individually picked from the buckets, measured and recorded. Rulers were used to measure the fish. If the students had question s on the type of fish, the lab instructors were more than willing to help. This process was repeated at a depth of waist deep as well as neck deep. It was done at different times; 8:00am, 9:45am and 11:00am. The Shannon-Weiner Index is a tool used to calculate biodiversity of an area. The equation is as follows: Hʹ = ˗Σ(Pi*log Pi). Pi is the relative frequency of a sample and can be found by dividing the number of a certain sample by the total number of individuals. N is the total number of individual fish counted; ni is the total number of counted for each fish species. This index is useful because it can be compared to different samples to see which is more diverse. The Shannon-Weiner index for the knee-deep sein at 11:00am is shown below in Table 1. A total of 198 fish were captured, most of which were Mojarra and Bay Anchovy. Next is the 11:00am Waist deep sein in Table 2. This time, 275 fish were caught, most of which were Mojarra and Bay Anchovy. Finally, the Shannon-Weiner for the 11:00am Neck deep sein is shown in Table 3. This catch had the fewest amount of fish, only 96; 92 of which were Mojarra.
Table [ 1 ] Shannon-Weiner Index 11:00am Knee-Deep Sein
Table 1 Shannon-Weiner Index 11:00am Knee-Deep Sein

Table [ 2 ] Shannon-Weiner Index 11:00am Waist-Deep Sein
Table 2 Shannon-Weiner Index 11:00am Waist-Deep Sein

Table [ 3 ] Shannon-Weiner Index 11:00am Knee-Deep
Table 3 Shannon-Weiner Index 11:00am Knee-Deep

Table [ 4 ] Shannon-Weiner Index 11:00am combination of all seining depths
Table 4 Shannon-Weiner Index 11:00am combination of all seining depths

Results: The three must abundant fish caught during the 11:00am knee-deep sein were Mojarra, Bay Anchovy and the Atlantic Piper. The students only recorded the sizes of the first 25 fish of each species caught. The average size for the Mojarra was 57.52mm the size distribution can be seen in Figure 1. The average size for the Bay Anchovy was 54mm. More size distribution and frequency can be seen in Figure 2. The Average size of the Atlantic Piper was 66.8mm, more information about their size distribution and frequency can be seen in Figure 3. The next sein was waist deep. Again the Mojarra and Bay Anchovy were the top two fish caught however this time 12 Spotted Sea Trout were also caught. The Average Mojarra size was 43.6mm, more information can be seen in Figure 4. Of the 25 Bay Anchovy size recorded, the average was 52.4mm with only two being higher than 60mm; the Anchovy size distribution can be seen in Figure 5. Next is the Spotted Seat Trout, 12 were caught averaging 50.5mm this distribution can be seen in Figure 6. Finally is the 11:00am neck deep sein. At the neck deep depth, the least amount of fish were caught; only 96. The fish were not very diverse, 92 were caught, averaging about 48.4mm; the size frequency distribution can be seen in Figure 7. Only one Bay anchovy and one Atlantic Piper were caught. Distribution can be found on figures 8 and 9.

Figure [ 1 ] Length vs. Frequency histogram for Mojarra caught in knee-deep water in the Indian River Lagoon
Figure 1 Length vs. Frequency histogram for Mojarra caught in knee-deep water in the Indian River Lagoon

Figure [ 2 ] Length vs. Frequency histogram for Anchovy caught in knee-deep water in the Indian River Lagoon
Figure 2 Length vs. Frequency histogram for Anchovy caught in knee-deep water in the Indian River Lagoon

Figure [ 3 ] Length vs. Frequency histogram for Atlantic Pipers’ caught in knee-deep water in the Indian River Lagoon
Figure 3 Length vs. Frequency histogram for Atlantic Pipers’ caught in knee-deep water in the Indian River Lagoon

Figure [ 4 ] Length vs. Frequency histogram for Mojarra caught in waist-deep water in the Indian River Lagoon
Figure 4 Length vs. Frequency histogram for Mojarra caught in waist-deep water in the Indian River Lagoon

Figure [ 5 ] Length vs. Frequency histogram for Anchovy caught in Waist-deep water in the Indian River Lagoon
Figure 5 Length vs. Frequency histogram for Anchovy caught in Waist-deep water in the Indian River Lagoon

Figure [ 6 ] Length vs. Frequency histogram for Spottes Sea Trout caught in Waist-deep water in the Indian River Lagoon
Figure 6 Length vs. Frequency histogram for Spottes Sea Trout caught in Waist-deep water in the Indian River Lagoon

Figure [ 7 ] Length vs. Frequency histogram for Mojarra caught in Neck-deep water in the Indian River Lagoon
Figure 7 Length vs. Frequency histogram for Mojarra caught in Neck-deep water in the Indian River Lagoon

Figure [ 8 ] Length vs. Frequency histogram for Anchovy caught in Neck-deep water in the Indian River Lagoon
Figure 8 Length vs. Frequency histogram for Anchovy caught in Neck-deep water in the Indian River Lagoon

Figure [ 9 ] Length vs. Frequency histogram for Atlantic Pipers’s caught in Neck-deep water in the Indian River Lagoon
Figure 9 Length vs. Frequency histogram for Atlantic Pipers’s caught in Neck-deep water in the Indian River Lagoon

Discussion: Closest to the shore, in knee-deep water, 198 fish were caught. In waist deep water, 275 fish were caught and in the neck deep water, only 96 fish were caught in the net. There is a clear different between all of the locations, which were only a few meters apart. In the waist deep water 77 or about 40% more fish were caught than in the knee-deep water. 179 more fish were caught in the waist deep water than in the neck deep water, this is 187% more. it is not surprising that the least amount of fish were caught in the deeper waters, here there is more open are to be attacked by a predator and less places for small fish to hid. Fish would also not want to be in the really shallow knee-deep water because they are more easily seen and caught by predators such as birds from outside the water. Considering this it makes sense that the fish would want a nice compromise between that dangers of both the shallow and deep waters and stay in the middle. By comparing the Hmax to the H’ in table 1 you can see that the knee-deep area has the smallest difference at .47. Waist deep has a difference of .699 and neck deep has a difference .653; these two areas are similarly diverse. This data discredits the hypothesis of this experiment that the most fish would be in the shallow water. A conclusion can now be made most fish will stay in the middle, waist deep water. This however can be false due to many limitations. For example, samples were only taken in the morning, fish may move throughout the day and night. The size of the area studied was very small compared to the entire lagoon and the experiment was not replicated. With more seining trips to different areas of the lagoon at different times of the day would give more accurate data for this experiment. The Shannon-Weiner Index supplies useful information is deciding how diverse an ecosystem is. According the index, the knee-deep area is the most diverse.

References:

Brevard Zoo. 2013. “Lagoon Quest”. https://brevardzoo.org/education/zoo-lagoon
Davidson, Osha Gray. 2001. “Fire In The Turtle House: The Green Sea Turtle and the Fate of the Ocean” page 187. books.google.com/books?isbn=0786728833
Kinder, Larry. 2005 “Flyfisher's Guide to Florida Saltwater” page 287. books.google.com/books?isbn=1932098208
Indian River Genealogical Society. 2007 “Indian River County” page 7. books.google.com/books?isbn=0738544450
Smithsonian Marine Station at Fort Peirce. 2011. “Where is the Indian River Lagoon and Why is It so Important?”. http://www.sms.si.edu