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Fish

Fish Data

Fish are collected following state protocols and identified in the field before being safely released on-site. The stream reach to be sampled is 35 times the mean width of the stream and encompasses habitat that will adequately represent species richness, abundance, and community structure of the fish population. Sampling is optimal during the summer months when water levels are low and fish populations are stable and sedentary. A list of study sites and fish collected is provided below.

Fish Inventory

2021 | 2020 | 20192018 | 20172016 
2015 | 2014 | 2013 | 2012 | 2011 | 2010

Fish Monitoring

Fish are collected following protocols outlined in the document Standard Operating Procedures for Conducting Biomonitoring on Fish Communities in Wadeable Streams in Georgia. The stream reach to be sampled is 35 times the mean width of the stream. This sample length usually encompasses three riffle-run-pool sequences and will adequately represent species richness, abundance, and community structure of the fish population.

Georgia’s fish biomonitoring season usually occurs from early April until mid-October, but the duration is variable due to water levels and temperature. Sampling is optimal during the summer months when water levels are low and fish populations are stable and sedentary. When sampling, one individual operates a backpack electrofishing unit; other members of the sampling team carry nets and a bucket to transport the fish. The sampling team moves upstream, so as not to disturb the areas yet to be sampled. The anode ring of the electrofishing unit sends out a charge which momentarily stuns the fish and draws them out of their habitat. The fish are then scooped up with a net and collected for identification. Riffles are sampled by setting up a seine net at the bottom and having the electrofishing unit move downstream toward the seine. Stunned fish will be carried by the current into the net; the sampler may need to shuffle and kick his feet to dislodge any fish that may be laying on the substrate (stream bottom). The net is then raised and captured fish are placed in a bucket. Fish are identified to the species level, counted, examined for anomalies (such as lesions and tumors), and released. Results from field sheets are transferred to a computer database so that the fish populations may be analyzed. A useful analytical tool is the Index of Biotic Integrity, which integrates characteristics of the fish community, population and individual organisms to assess biological integrity.

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picture of a man and a woman conducting fish monitoring at a creek

Fish Taxonomy

Fish are widely recognizable to anglers, outdoor enthusiasts, and everyday citizens. Size, body shape, and color distinguish different taxa of fish and help when trying to identify a species.

The body shapes of fish have developed to take advantage of the habitats where they live and feed. Longer, torpedo-shaped fish inhabit fast-moving water, while deep-bodied fish have adapted to thrive in slower-moving pools. Fins and tail, position of mouth, and barbels (whiskers on a catfish) enhance a fish’s ability to swim, feed, and locate food respectively. These and other physical characteristics not only allow a species to take advantage of certain stream habitats unpopulated by other fish but also help the scientist to make a conclusive identification.

The Stream Monitoring Program uses information obtained during fish sampling to determine the Index of Biotic Integrity (IBI) for a local stream. To identify the fish specimens and safely release them in the field, the Stream Monitoring Program works closely with a fisheries biologist.  Cobb County Aquatic Biologists hold a Scientific Collecting Permit from the Georgia Department of Natural Resources, Law Enforcement Division, Special Permits Unit.

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hands holding red breast sunfish lepomisauritus
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fish

Fish, like macroinvertebrates, are susceptible to degradations in water quality and are sensitive to pollution and habitat loss. Unlike macroinvertebrates, fish are relatively mobile. If the stream reach does not provide adequate protection from predators, sufficient food supply or acceptable water quality, fish will search out more suitable conditions. The presence or absence of fish provides commentary on water quality as well as habitat stability and food supply.

Fish inhabit different living spaces within the stream ecosystem and have evolved to thrive in different flow regimes. A stream with a variety of flow conditions such as riffles, pools and undercut banks will host a more diverse population, which is indicative of a healthy stream.

Several additional factors make fish excellent monitors of local steam conditions. Because fish have adapted different eating habits, a diverse fish population may indicate a well balanced ecosystem which sustains aquatic vegetation, macroinvertebrates and smaller prey species. Additionally, fish live longer than macroinvertebrates and spending a longer life cycle exposed to variations in water quality can provide valuable information regarding the consistency of water quality over many years. This is particularly true of predator species higher on the food chain which may exhibit the effects of bioaccumulation.

The longevity of the fish life cycle, their dependence on a variety of stable habitat to support different species, and their reliance on nourishment from plants and animals make fish communities a very useful tool when assessing stream health or impacts to water quality.