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Finding Fish in Peru, Part One

One fish, two fish, red-blue Peru tetra fish. In November 2018, Smithsonian Conservation Biology Institute researchers and partners spent two weeks in Peru counting and identifying fish. Their study area is the location of a future oil pipeline, and the information they collect could help protect the aquatic animals that call this part of the Amazon home.

In this photo essay, take a look at some of the animals they discovered during their survey, as well as the methods they used to collect data.

A small, iridescent red and blue fish found in Peru. Researchers believe it is a red-blue Peru tetra fish but need to conduct a DNA analysis to confirm

Researchers believe this is the red-blue Peru tetra (Hyphessobrycon margitae), a freshwater species found in the Nanay River in the northern Peruvian Amazon.

However, the red-blue Peru tetra looks a lot like some of the other fish found in the area. To be sure they correctly identified this fish, scientists will conduct a DNA barcoding analysis — a test used to identify species based on a small section of their DNA.

A fish researcher (ichthyologist) records GPS data from a small boat in a river in Peru

Here, Morgan Ruiz Tafur, one of the project’s lead ichthyologists (a fancy word for fish researcher), uses a GPS to record the geographic coordinates of the sampling site. In addition to collecting and identifying fish, the team also records information about each place they visit.

They consider the general appearance and quality of the aquatic habitat -- from water flow, depth and clarity to what the substrate (or bottom of the stream) consists of, such as sand, silt or leaf litter.

Information about the habitat may be important in the future. If local communities and researchers see fish populations shifting, they can look for changes in the habitat to help understand why.

A small catfish, called a pastaza cory, with short barbels (or whiskers) extending from its mouth, small fins and a short, triangular tail. It has a thick stripe around its midsection and smaller stripes near the back of its body and on its tail

The pastaza cory (Corydoras pastazensis) was found in both of the main rivers that the future pipeline will cross. This armored catfish is popular in the aquarium trade because of its attractive colors and patterns.

If carefully and sustainably managed, the trade of ornamental species like this one can be a good economic alternative to illegal logging or hunting activities.

The underside of an armored catfish, with two wide fins on the side of its body and barbels (whiskers) extending from around its mouth

Some species of armored catfish (genus Loricaria) can be distinguished by the unique fringes, filaments and barbels that extend from their lips. It is thought that these extensions help catfish search for food in murky water. The team has yet to identify the fish pictured here, but they hope that DNA analysis will reveal more information.

A group of researchers wade into a murky stream in the Peruvian Amazon and use a beach seine to catch fish

Researchers have to get creative when searching for wildlife, especially in the water where animals can be difficult to spot and even more challenging to catch. The team in Peru used different fishing techniques — including cast nets, beach seines, gill nets and hand nets — to ensure they would find a wide variety of fish.

Beach seines, like the one used here, are dragged along the stream or sea bottom toward the shore. They help catch species found in the lower water column or along the sea floor and are most useful in shallow waters.

Cast nets, as their name implies, are cast along the water’s surface. They are often used in larger bodies of water to catch fish swimming in the upper water column. Hand nets are helpful in small streams, where they can be quickly placed and removed from areas where fish may be hiding.

Gill nets are used in deep, open waters and often have wider mesh for catching large species. They can be left in the water for many hours, hanging like a curtain to catch swimming fish.

An electric eel resting on top of a mesh net in the Peruvian Amazon

In Hermogeno Creek, the team caught an electric eel (Electrophorus electricus). These fish grow up to 8 feet (2.5 meters) long and can discharge 800 volts of electricity, which they use for defense, hunting, communication and navigation.

Eels are adapted to breathe both underwater and at the surface, which helps them survive in different environments. They eat fish, crustaceans, insects, amphibians, reptiles and even small mammals, so their presence in aquatic ecosystems indicates that there are healthy populations of other animals.

Stay tuned for Part Two, where you’ll meet more of the animals that researchers encountered in the Amazon and find out how they plan to use the data they collected.