Mass mortality of the Critically Endangered naked characin ( Gymnocharacinus bergii ): Possible causes and impact

QUIROGA, SOFÍA; POVEDANO, HERNÁN E.; SOLIMANO, PATRICIO J.; VELASCO, MELINA A.; MARTORELLI, SERGIO R.; MONTES, MARTÍN M.; BARNECHE, JORGE A.; CATRIN, LAURA; CARTES, VÍCTOR FERNÁNDEZ; MAGGIONI, MATÍAS; SORICETTI, MARIANO; KACOLIRIS, FEDERICO

AQUATIC CONSERVATION-MARINE AND FRESHWATER ECOSYSTEMS

JOHN WILEY & SONS LTD

Año: 2023

1052-7613

1. The naked characin (Gymnocharacinus bergii) is the only endemic fish of the aridPatagonia of Argentina, living only in the thermal headwaters of the ValchetaStream in the Somuncura Plateau. This species is listed as Critically Endangeredon the IUCN Red List.2. In April 2018, a massive mortality event was observed in the species.Parasitological studies identified the cause as an epidemic of white spot disease,caused by the parasite Ichthyophthirius multifiliis (Ich).3. Ich is a common disease in aquaculture settings, but it has also been reported asan epizootic in wild fish populations across tropical and temperate regionsworldwide. This occurrence is associated with the introduction of fish into nonnative environments.4. This article presents the first recorded instance of a mass mortality event and Ichoutbreak in the naked characin. It includes a mapping of the disease in theheadwaters of the stream, an estimation of the impact on the species´ populationsize, and an analysis of potential causes associated with this epidemic.5. The results indicate that the epizootic produced mortality of 82% of the globalpopulation of the naked characin and was linked to the presence and highabundances of the invasive fish species Uruguay tetra (Cheirodon interruptus). Thedisease occurred in stream sectors where both characid species coexist,particularly in areas with the highest water temperatures.6. The Ich outbreak represents the most recent and severe threat recorded for theCritically Endangered naked characin. Implementing control measures against theinvasive Uruguay tetra is imperative to prevent future outbreaks that could pushthe species to the brink of extinction in the near future.7. This study provides crucial information for assessing current managementinterventions and developing new strategies within the framework of the actionplan for naked characin conservation