Phenotypic differences between non-native populations of rainbow trout Oncorhynchus mykiss in the Argentinean Patagonia

SEVASTEI, VIANEL; PAINEFILÚ, JULIO; CUSSAC, VÍCTOR E.; CRICHIGNO, SONIA A.

HYDROBIOLOGIA

SPRINGER

Lugar: Berlin; Año: 2024

0018-8158

Patagonia offers several examples of local adaptation in the exotic rainbow troutOncorhynchus mykiss. Specifically, the Valcheta Stream, characterized by hot springheadwaters and temperate lower reaches, was initially stocked in 1928. Subsequently,progressive upstream expansion, predation by O. mykiss on the critically endangerednaked characin Gymnocharacinus bergii, and a rapid adaptation to high watertemperature were observed. We documented the life history, breeding, growth,stomach content, Fulton condition factor, hepatosomatic and gonadosomatic indexes,haematological parameters, and body shape of Valcheta rainbow trout, comparing itwith a cold-water population of the same origin (Guillelmo Stream). The Valchetapopulation exhibited an earlier acquisition of sexual maturity and smolt characteristics,along with different growth parameters, including a shorter asymptotic length, highergrowth rate, and breeding rooted in winter, contrasting with the spring breedingobserved in Guillelmo Stream. Body shape variations were evident betweenpopulations and among parr, smolt, and adults. Stomach content volume, conditionfactor, hepatosomatic and gonadosomatic indexes, and haematology displayeddifferences related to annual cycle and reproductive adjustments. The Valchetapopulation of rainbow trout serves as an illustrative example of how fish species canadapt to effects of the climate change through local adjustments.