Argentinian silverside
A large, adaptable silverside native to South America.
The Argentinian silverside is a Neotropical fish found in fresh and salt waters across South America. It grows quickly, supports major fisheries, and has been introduced globally, sometimes harming local ecosystems.
- Reaches up to 82 cm in length and 5.2 kg in weight.
- Sex determination depends on water temperature during development.
- Invasive in Lake Titicaca, threatening native fish species.
- Tolerates fresh, brackish, and salt water up to 3.5% salinity.
- Fast-growing, reaching maturity in just one to two years.
What it is
This Neotropical silverside is a robust fish that can reach 82 cm in length and weigh over 5 kg. It resembles other members of its genus but is notably larger. The body is streamlined, suited for life in varied water conditions. Its common name, pejerrey, translates to king fish in Spanish, reflecting its status in local cultures. While many silversides share this name, this specific species is distinct due to its size and adaptability.
Where it lives
Native to subtropical and temperate regions east of the Andes, it inhabits waters from the Río Negro basin in Argentina to southern Brazil. It thrives in the Río de la Plata Basin, covering parts of Paraguay and Uruguay. Coastal populations extend from Buenos Aires Province to Rio Grande do Sul. The fish occupies rivers, lakes, estuaries, and coastal lagoons. It tolerates fresh, brackish, and salt water, though not hypersaline environments. Temperatures between 7 and 30 °C are suitable, but extreme heat proves lethal.
How it lives
Young fish feed primarily on zooplankton. As they grow to about 10 cm, their diet shifts to aquatic and terrestrial insects. Adults become piscivorous, occasionally eating their own young, along with shrimp, snails, and plant matter. In captivity, they accept dry pellets. The species is highly adaptable, surviving in stagnant or flowing waters. However, high temperatures above 25 °C increase susceptibility to parasites and bacteria, which can cause mass mortality events.
Breeding and life cycle
Growth is rapid, with fish reaching maturity at one to two years old. Spawning occurs mainly in March and April, with a secondary period from August to November. Females lay thousands of eggs in shallow water attached to plants. Water temperature dictates the sex of the offspring. Cooler waters below 19 °C produce only females, while warmer conditions above 23 °C yield mostly males. Larvae cannot survive high salinity, but juveniles adapt quickly to broader ranges.
Fish and people
Regarded as an excellent food fish, it supports significant commercial fisheries and aquaculture operations. Anglers value it as a game fish due to its fighting ability. Introductions to new regions have boosted local economies but also caused ecological damage. In Lake Titicaca, pollution has led to unsafe metal levels in some catches. The species is farmed for its fast growth and ease of breeding in controlled environments.
Status and threats
While widespread and common, local populations face threats from rising temperatures and salinity due to climate change. As an invasive species, it has contributed to the decline of native pupfish and catfish in Bolivia, Peru, and Chile. Hybridization with native relatives in southern Argentina dilutes genetic integrity. Conservation efforts focus on managing introductions and protecting vulnerable native habitats from competition.
Questions people ask about Argentinian silverside
What does the Argentinian silverside eat?
Young fish consume zooplankton, while adults eat insects, shrimp, snails, plants, and other fish. They may even cannibalize their own young. In farms, they readily accept commercial dry pellets designed for trout.
How does water temperature affect this fish?
Temperature determines the sex of the offspring. Cool water below 19 °C produces females, while warm water above 23 °C produces males. Extreme heat above 32 °C is lethal, and high temperatures increase disease risk.
Is it safe to eat silverside from Lake Titicaca?
Some populations in Lake Titicaca contain metal levels from pollution that exceed international safety thresholds for human consumption. Fish from its native range in Argentina are generally considered safe and are widely eaten.
Why is it considered invasive in some areas?
Introduced populations have outcompeted native species like pupfish and catfish in Bolivia, Peru, and Chile. They also hybridize with native silversides in Argentina, diluting the genetic purity of local stocks.
Good reading and sources
- Odontesthes bonariensis on WikipediaEncyclopedia
- More photos on Wikimedia CommonsPhotos
- Wikidata recordOpen data
The facts on this page come from the Wikipedia article "Odontesthes bonariensis", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.
It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.
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