Plastic ingestion by the Wels catfish



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Plastic ingestion by the Wels catfish

The catfish is one of the major predators of inland waters and feeds on live and dead fish, worms, larvae and anything else it can find on the bottom. Specifically, during the juvenile phase it feeds on bottom invertebrates, while in the adult phase it feeds on fish such as eels and cyprinids.

In some cases, when the catfish is hunting, it goes up from the bottom to see if there is fish nearby and is often attracted by moving animals. The quantity of fish it eats daily is equal to 1.99% of body weight, in fact a 10 kg specimen feeds on 72.8 kg of fish per year, or 0.199 kg per day.

Its main weapon is its barbels, which allow it to identify prey in the dark and in the presence of high turbidity. As proof of this, there are many fishermen who underline the high number of catches made when the rivers are in flood.

Threatened in the countries of origin by fishing, pollution and the construction of reservoirs and dams, in the waters into which it was introduced, it is a source of problems and dramatic impacts on indigenous populations.

Plastic ingestion by the Wels catfish (Silurus glanis L.) study: detailed chemical analysis and degradation state evaluation, published on the Toxicology reports, explained: "Plastic ingestion by various organisms within different trophic levels, including humans, is becoming a serious problem worldwide.

Plastic waste samples are often found concentrated in an organism's digestive tract and can be degraded and further translocate to the surrounding tissue or circulatory systems and accumulate in food chains. In the present work, we report a detailed chemical analysis and degradation state evaluation of a relatively large piece of plastic waste found in the gastrointestinal tract of a Wels catfish (Silurus glanis L.) caught in the Bodrog River (Danube River basin ), eastern Slovakia.

Chemical analysis by surface-sensitive X-ray photoelectron spectroscopy (XPS) was performed to identify the surface composition of the digested plastic piece. Micro-Fourier transform infrared (μFTIR) spectroscopy showed that the plastic waste was oxidized low- density polyethylene (LDPE), with some nylon fibers adhered on the surface.

Glyceraldehyde adhered onto LDPE was also det ected, which might come from the carbohydrate metabolism of that fish. A morphology study by digital optical microscopy indicated solid inorganic particles attached to the surface of LDPE.

A degradation study by differential scanning calorimetry (DSC) showed considerable oxidation of LDPE, leading to fragmentation and disintegration of the plastic waste material."