Jeremy enters the bowels of Lighthouse Cave, San Salvador, Bahamas.
For hundreds of years, humans have "succeeded extravagantly at the expense of other species" (Quammen, 1996), and played a major role in determining the fate of ecosystems around the world. Our research project examines this concept on a local scale. We have sampled fish species in two streams that have faced varying levels of human disturbance, Collins Run and Harkers Run. Our ultimate goal is to assess the affects human development has had on the diversity, population density, and distribution of fish in these streams. We hypothesized that the recently disturbed stream, Harkers Run, will exhibit greater fish diversity, a higher population density, and a more even intra-species distribution. Representative samples of both Collins and Harkers Runs were taken with the help of fishing shocking techniques, and our data was analyzed. Overall, we found our hypothesis to be only partially correct. While we did collect more species, and more fish overall, at Harkers Run, Collins Run was more diverse and its population was more evenly distributed between species.
This research project is aimed at determining the affect human disturbance has on the distribution and diversity of fish in local streams. The two streams in question are Harkers Run and Collins Run. When we chose the streams for this project, we were under the impression that Collins Run had been affected by human development, while Harkers Run had not. Upon arriving at Harkers Run, though, it was obvious that it too was facing human disturbance. Thus, our research question had to be modified. We decided to assess the differences among fish diversity and population density in streams that have suffered varying levels of disturbance. We believe the fish in the long-term disturbed stream (Collins Run) will be less diverse and fewer in number compared to those in the recently disturbed stream (Harkers Run). Using fish shocking techniques, we hope to obtain data representative of each stream's entire fish population. Individual fish will be netted, and identified before their release. After collecting and analyzing the data, we will ultimately determine whether or not our hypothesis is correct.
Fish have been adapting to changes in their living environments throughout evolutionary hisory. Those that are unable to adapt, eventually die out (Vostradovsky, 1973). Over the years, humans have contributed to the extinction of many species. On a smaller scale, we have continually tested the adaptability of species by disturbing their living environments (Gulland, 1977). This project is interesting because it puts the latter point in perspective. We will see, first hand, how human development has impacted freshwater fish species in two of Oxford's streams.
Relevance of Our Research Question
Pollution, dams, and other man-made structures have been throwing off the natural ecology of rivers for decades, even centuries to a lesser extent. How has this affected the species that inhabit these rivers and streams? How have fish adapted to these situations? On a larger scale, how can our project affect the decisions of future scientists and conservationists? These are some of the questions we will attempt to answer with our research.
It is easy to see that there is a lot to learn about the impacts of human development on ecosystems. It is our hope that this research will provide an idea as to how, not just fish species, but faunal ecosystems worldwide, have coped with similar habitat disturbances. For example, if disturbances in stream systems cause fish to be less diverse and smaller in size, a disturbance in the rainforest might have the same affect on the plant and animal species that inhabit it. We believe many similarities exist between our research and that which has been done in ecosystems around the globe.
Conservationists are constantly looking for ways to stop ecosystem decay, and preserve what species diversity we have left. Our research may encourage conservationists to take action towards protecting stream ecosystems from human development. It also might urge them to revert already disturbed stream systems back to the way they once were. If nothing else, this project will provide a better analysis of the affect stream disturbance has on local fish species.
Materials and Methods
The first step in our experiment was to visit Collins and Harkers Runs. After consulting with Dr. Hays Cummins, it was decided that a technique termed fish shocking would be the most resourceful means of data collection. With this method, an electrical charge was applied to each stream, temporarily stunning the surrounding fish. One person was required to wear a backpack containing the electrical generator. This person was responsible for shocking the water with the attached wand, to make the fish easier to catch. In addition, two people were needed to walk behind the electrode "tail," and collect the stunned fish in nets. Netted fish were then stored in a buoyant, water-filled bin, and dragged behind the netters until they could sorted by species, and put into their respective buckets. The majority of the fish recovered quickly from the shock, and after we had finished sampling, they were released in the stream with no harm done (Fish Shocking, 2002). This procedure was chosen because it was recommended by a variety of sources dealing with fish population dynamics.
We are confident that our experimental design was the most statistically sound option available to us. We had the privilege of being accompanied to our sampling sites by a local expert in fish shocking techniques, Dr. Donna McCullum. She walked us through each step, and played a crucial role in the species identification of the fish we netted. Our only concern is that we did not obtain a sample that is representative of each stream's total population. We observed some fish swimming away from the wand, while others recovered too quickly from the shock to be caught. Since we did net such a variety of species though, we trust our sample is at least a good representation of the fish in Collins and Harkers Runs.
The materials needed for our experiment include: (1) the fish shocking device, (2) two nets, (3) a floatable bin, filled with water, and (4) one bucket per fish species. The use of each of these materials has already been discussed above. Further methods in our data collection involved researching what others had done in the past. Primarily, we examined the data obtained by Schneider et al. (2001), who also studied fish diversity in Collins and Harkers Runs. Their analyses were useful, since Harkers Run was still undisturbed at the time of their sampling. We also involved the class, to an extent, in our research. With the posting of our research proposal, we requested feedback and suggestions from the class, which greatly improved our project.
Research timeline for our project:
-October 4, 2002: Submit our Research Proposal by 11:59pm
-October 14, 2002: Sample at Collins Run at 8am
-October 29, 2002: Sample at Harkers Run at 8am
-October 30, 2002 to December 8, 2002: Analyze the Data Obtained Collins and Harkers Runs
-December 9, 2002: Present our Research to the Class at 5:45pm
-December 10, 2002: Submit our Final Research Report by 11:59pm
Upon visiting Collins and Harkers Runs, we were able to collect a variety of fish species. The charts, graphs, and equations below best display the data from our research.
Here the percent relative abundances for individual fish species at each site are graphed against one another.
To see the data sheets in excel format, click here
The following is a brief description of the individual fish species we sampled, according to Page and Burr's A Field Guide to Freshwater Fishes: North America North of Mexico (1991):
The striped shiner is marked by dark stripes on its sides, which meet behind its dorsal fin, forming a V-pattern. It is generally olive to silverish-bronze in color, although the body and fins of large males and some females are pink to red in color. The striped shiner inhabits clear to relatively cloudy creeks and small rivers, usually congregating near riffles in rock-strewn pools (110).
The spotfin shiner is identified by a black spot on the back of its dorsal fin, few to no black membranes on the front of its dorsal fin, and a pointy nose. It is olive above the black stripe on its back, and silver in color below. Breeding males possess bluish sides and yellowish-white fins. The spotfin shiner resides in sandy and pebbly creek, pools, and small to medium sized rivers (120).
The emerald shiner boasts a slender body, pointy nose, and a large, slanted mouth (which stretches to the front of its eyes). Its dorsal fin stems behind its pelvic fin, and it lips are black in color. It is light olive, with a silver stripe on its side. The stripe reflects an emerald color in light, from which the fish gets its name. It lives in runs and pools in moderate to large lakes and rivers, but is most commonly found in lucid water over fine-grained sediment (132).
The mimic shiner displays a wide, round nose, a small mouth, large eyes, and a thin body. Its dorsal fin stems above or a little behind its pelvic fin. It is clearish-gray to olive-yellow in color, with faint stripes on its silver side. The mimic shiner's habitat consists of pools at rivers, creeks or headwaters, which are bottomed by sandy sediment. It generally prefers quiets waters (154-155).
The green sunfish can be described as a thick-bodied fish, with a big mouth and an elongate nose. Adult green sunfish display yellow to orange fin edges, and a large black spot on their second dorsal and anal fins. It is bluish-green in color, with metallic specks of yellow and green. It also has a small, round pectoral fin. It prefers the quiet water of pools, lakes, ponds, and slow streams (267).
The bluegill sunfish is associated with a large, black spot on its dorsal fin, an immensely compact body, and an elongate, pointy pectoral fin. It has a small mouth and is olive in color, with tiny yellow and green specks. Adults have a slightly blue hue, with transparent to translucent fins, and a bright red to orange belly. It occupies lakes, creeks, ponds, and swamps, which are surrounded by vegetation (269).
The central stoneroller is marked by black banding on its orange anal and dorsal fins. In addition, it has curved rows of 1-3 large nodules inside its nostrils, and nodules around its nape. It has a preference for rocky runs, creeks, riffles, pools at headwaters, and small to moderate rivers (93-94).
The bluntnose minnow possesses a blunt nose, as its name implies, and a small, straight mouth. It has a thin body and round eyes, located on the sides of its flat head. Its dorsal fin stems behind its pelvic fin. It is tan to olive in color with a gray to black streak running around its nose. In addition, its scales are distinctly outlined, and it bears a black spot on its caudal fin. The remainder of its fins are transparent, except for another dark to black spot on its dorsal fin. It can live in virtually any type of water, but it is most attracted to lucid, stony streams (130).
The silverjaw minnow is identified by large, silverish-white chambers on its cheeks. The bottom of its head is extremely flat, and its eyes are located on the upper portion of its head. It has a compact body, a long nose, and its dorsal fin is located directly over its pectoral fin. It is light tan to olive-yellow in color, and possesses a dark stripe on its back. The lower half of the fish is generally silver in color. It lives in riffled, shallow water, bottomed by sandy sediment. It is found in most creeks and small to moderately sized rivers (163).
The creek chub is marked by a large black spot on its dorsal fin base, a black caudal spot, a very large mouth, and a pointy nose. It is olive-brown in color, with a black streak on its back. It also has a dark streak on its greenish-silver side, which goes around its nose and on its top lip. Orange coloration is common on the dorsal fin base and lower fins of breeding males. The creek chub inhabits pools in small rivers, creeks, and headwaters, bottomed by rocks and sandy sediment (87).
The blacknose dace possesses a number of dark spots on its back and sides. It also bears barbels on the corners of its mouth, and a long, pointy nose. It is light brown in color, has a black and silver spot at the base of its dorsal fin, and a black streak on its side. Breeding males acquire yellowish-white pelvic and pectoral fins, and a red stripe running the length of their body. The blacknose dace's habitat consists of pools in small rivers, creeks, and headwaters, bottomed by rocky sediment (100).
The white sucker has 0-3 rows of papillae in the center of its lower lip, and 2-6 rows on its upper lip. Its upper lip is half as thick as its lower lip. It lacks membranes connecting its pelvic fin to the rest of its body. It is olive-brown to black in color. Its fins are transparent to translucent. Breeding males are distinguished by their gold coloration, and bright scarlet stripe. It lives in many different habitats, but prefers tiny, lucid creeks and small to moderately sized rivers (169).
The golden redhorse sucker has a portly body, a gray, forked caudal fin, and a gray, concave dorsal fin. Its upper half is olive to brass in color, while its underside is yellow to white. Its anal and paired fins are yellow to orange. Breeding males have dark stripes along their sides and large tubercles on their nose. The golden redhorse resides in muddy to rocky pools, riffles and runs in creeks and rivers, and occasionally in lakes (185-186).
A big, flat, rectangular head characterizes the northern hog sucker. Its wide body tapers behind its dorsal fin. It has a blunt nose, and big lips, which are covered by papillae. It is olive-bronze to red-brown on its upper half, and yellow to white on its underside. The northern hog sucker's nose is bluish-black, and its fins are often orange in color, with black edges on its dorsal and caudal fins. It enjoys pools, runs, and riffles of lucid, rock-bottomed creeks and rivers (180).
The carpsucker has a body depth roughly 2 1/2 times larger than standard length. It possesses a small cone-shaped head, a short dorsal fin ray, a short nose, and its upper jaw extends past its eyes. It is olive to brown in color, with a white to brown underside. Its paired fins are white to pinkish-orange. It lives in backwaters and pools of rivers, creeks, and lakes (166).
The orange throat darter boasts dark bars on its sides, and an arched body. It is olive to brown on its upper half, and white to orange below. Its dorsal and caudal fins have red edges, while the rest of its fins have blue edges. It has orange branchiostegal membranes, which give the fish its orange chest and stomach. It also has two orange spots at the base of its caudal fin. The orange throat darter occupies mostly shallow, pebble-bottomed riffles, but is also found in pools and runs of creeks, headwaters, and tiny rivers (314).
Now that we have discussed the diversity of species sampled in Collins and Harkers Runs, it is important to turn our raw data into results. There are several equations that assist in this process.
Discussion and Conclusions
After reviewing our results of the abundances and diversity of the fish in Harkers Run and Collins Run, a few conclusions were made. We first had to take into account the extremely low water level of the streams. This made it difficult for us to even find a place to sample at Harkers Run. However, each site had a deep pool with a large concentration and diverse number of fish in it, along with shallow areas and riffles. Looking at Collins Run, we sampled shallower riffle areas along with a deeper pool, created around a large cement sewer block and pipe. This pool was the most obvious area disturbed by humans. We compared this pool with the pool from Harkers Run, which had been naturally carved out of shale. Then, we compared the fish from the shallower areas to see which streams were more stressed or disturbed.
Looking at the shallower riffle areas first, we noticed a significant size difference in the species of fish we collected, not only between species, but also within species. The fish in these areas were much smaller than those of the larger pools we sampled. The species we collected in these areas include orange throat darters, small minnow species, and small shiner species. When we looked at the numbers of these fish in each area, we found that the minnow species were more abundant in Harkers Run than Collins Run. However, we found that the shiner species were much more abundant in Collins Run. This may have been due to the fact that we covered more shallow ground in Collins Run than Harkers Run.
Moving on to the larger pool areas, we found a greater variety of species and a greater range in fish sizes. The Ideal Free Distribution Model predicts that fish will occupy the highest quality living areas in their environment, until the density of individuals reduces the benefit per individual. The species then spill over into the next highest quality area, and so on (Matthews, 1998). We believe that the pools within the streams we sampled offer the highest quality living areas for fish. The data from Collins Run reveals that this is where we found the largest fish, such as suckers, stonerollers, and sunfish. The sunfish and suckers were commonly found hiding in leafy areas or undercut banks, while the stonerollers were more often out in the open water. A past study on fish population dynamics stated that on average about 18% of fish in smaller streams exceed the length of 30 centimeters as adults (Matthews, 1987). However, we did not find any fish even close to this size in either stream. A possible cause for this is human disturbance. Pools were also the regions that we found most of the shiners in Collins Run. They were found in the open water in schools swimming around the pool searching for food. There were also more blacknose daces found in Collins Run. At Harkers Run, we found a much larger population of creek chubs. The bluntnose minnows and central stonerollers also had a much larger relative abundance at Harkers Run as compared to Collins Run. A larger variety of suckers were collected from Harkers Run, such as the carpsucker and northern hogsucker, which were not collected at Collins Run.
These findings all go to show that there was a definite difference between the two streams. Harkers Run, which was the lesser disturbed of the two, had a greater variety of species. After comparing our results with last years Fishbusters results, we found that the Fishbusters collected a much larger amount of orange throat darters than we did. We assumed this to be because of the extremely low level of the water, especially in the riffle areas. Many of the areas that would be riffles in higher water were either totally dried up, or there was so little water that it was uninhabitable. Another big difference we noticed was the number of creek chubs found at Harkers Run. We collected far more creek chubs than the Fishbusters (105 fish with a 33.65% relative abundance vs. the Fishbusters' total of 14 at both sites with a relative abundance of 5%). A possible reason for this would be that the lower water levels forced the creek chubs to congregate in the large pool we sampled as compared to a larger number of smaller pools present when the water levels were higher last year. However, we did notice that the central stonerollers were among the most abundant fish in their data, which was similar to our results. This was most likely due to the stonerollers inhabiting the larger pool areas that were present both last year and this year with the water level low (Schneider et al., 2001).
After making these conclusions about our results, some questions arose that we would like to answer in the future, or have someone else answer in the future. Brian had questioned how the low water levels affected the crayfish, frogs, and other creatures that lived in or around the streams. Also along those lines, how are those creatures affected in a disturbed environment vs. an undisturbed environment. Also, we would have liked to take depth readings of the streams to compare them with last year's levels. Another experiment we would like to have done would be to sample a stream that was really undisturbed. Considering that Harkers Run, the less disturbed of the two streams, had been bulldozed in areas, we had to question the validity of our results. In our thoughts, Harkers Run was another disturbed stream, just for a shorter period of time than Collins Run. Some suggestions for further investigations in this subject area would be: visit more sample sites (even though it is hard because the group will be dependant on others for equipment and time slots), test water quality, visit an actual undisturbed stream, and sample during a different time or season of the year (we did late fall).
Overall, our hypothesis was only partially correct. We did collect a greater variety of species, and more fish overall, at Harkers Run. But Collins Run was more diverse and had a better intra-species population distribution. If you would like to see additional pictures or a Quicktime Movie of our sampling at Collins Run, click here.
Cummins, Hays. Paleoecology Problem Set 2002.
Gulland, J.A. Fish Population Dynamics. John Wiley & Sons, Ltd., New York: 1977.
Matthews, William J. and Heins, David C. Community and Evolutionary Ecology of North American Stream Fishes. University of Oklahoma Press, Norman: 1987. p 28.
Matthews, William J. Patterns in Freshwater Fish Ecology. International Thomson Publishing, New York: 1998. p 500.
Page, Lawrence M. and Brooks M. Burr. A Field Guide to Freshwater Fishes. Houghton Mifflin Company, Boston: 1991.
Quammen, David. The Song of the Dodo: Island Biogeography in an Age of Extinction. Touchstone, New York: 1996.
Schneider, Grace, Marta Ralston, Amanda Higley, and Kristin Mandish. The Effects of Human Land Use on Fish Population (The Fishbusters). Natural Systems Research Project. 2001.
Vostradovsky, J. Freshwater Fishes: A Concise Guide in Colour. Hamlyn Publishing Group Limited, New York: 1973.
Fish Shocking. Mine Reclamation Clearing House> 2002.
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