Effects of environmental factors on the elemental composition of pejerrey Odontesthes bonariensis otoliths

WANG, YANPING; COLAUTTI, D. C.; BERASAIN, G. E.; VELASCO C. A.; YOKOTA, M.; STRUSSMANN, C. A.

Edinburgh

Congreso; 6th World Fisheries Congress; 2012

The fisheries society of british isles

The pejerrey Odontesthes bonariensis is the most important inland water fisheries resource in the Pampa region, a vast area of lowlands extending from the foothills of the Andes Mountains through Central Argentina, Uruguay and Southern Brazil to the Atlantic Ocean. Pejerrey populations inhabit an extensive network of rivers and shallow lakes where environmental conditions may vary from hyposaline to hypersaline and show temperature fluctuations in excess of 25ºC. This area is also characterized by decadal cycles of droughts and inundations that impart marked changes in the lakes? water levels and physico-chemical parameters, nutrients, primary production and trophic structure. In this environment, natural pejerrey populations show marked fluctuations in abundance, from hyper abundance and dominance over other species even complete disappearance in some years, but the causes are still not clear. Sustainable utilization of pejerrey resources would require information on the life history, origin, migration and dynamics of populations, their tolerance to environmental changes, and the connectivity of water bodies. Otolith microchemistry has the potential to address many of these needs including the record of past growth rates and the environmental conditions experienced by individual fish. As a preliminary step, this study used electron microprobe analysis (EPMA) to examine the amount of individual variation of otolith elemental profiles in fish exposed to the same environment, whether microchemistry would allow discrimination of fish from different origins, and the effects of water temperature, salinity, and food abundance on otolith microchemistry. The results showed that strontium (Sr) content provides a clear fingerprint for individuals exposed to the same environment and allows stock discrimination. The otolith Sr content was stable within salinities of 1 and 5 PSU and in this range was an accurate proxy for water temperatures between 13 and 29ºC. Abundant or restricted feeding affected growth rates but not the Sr content of otoliths. The results support the usefulness of otolith microchemistry to study biological phenomena in natural pejerrey populations.