Intra-population variation in anadromy and reproductive life span in rainbow trout introduced in the Santa Cruz River, Argentina

CARLA RIVA ROSSI; MIGUEL PASCUAL; JOHN BABALUK; MARTÍN GARCÍA ASOREY; NORMAN HALDEN

JOURNAL OF FISH BIOLOGY

Blackwell Publishing

Lugar: Oxford, UK; Año: 2007 vol. 70 p. 1780 - 1797

0022-1112

Scale patterns, maturational status and otolith microchemistry (strontium to calcium ratios)were analysed in sympatric anadromous and non-anadromous rainbow trout Oncorhynchusmykiss in the Santa Cruz River (Patagonia, Argentina) to investigate the life-history differencesof anadromous and non-anadromous lifestyles and the association between maternal origin andprogeny life history. The analyses revealed that both forms can give rise to one another,indicating a single population with alternative phenotypes. Anadromous fish smolted at ages2 and 3 years, matured after 1 to 2 years in the ocean, and survived up to 11 years, spawning upto eight times. Non-anadromous fish survived up to 6 years, spawning up to three times. Theextended reproductive life span associated with anadromy in this river suggests that increasedenergetic and physiological demands associated with ocean migration may not necessarily resultin reduced postspawning survival, as has been suggested for salmonids in general. Alternatively,reduction in parity may be regarded as the evolutionary outcome of reproductive traits resultingfrom the adoption of anadromy (i.e. augmented reproductive investment) coupled with longrangemigrations to and from the ocean. The life-history patterns of Santa Cruz River rainbowtrout provide a natural experiment for investigating the evolutionary transition and maintenanceof anadromy and non-anadromy within salmonid populations.