Impact of climatic fluctuations on commercial fisheries in the Paraná River along the last century

RABUFFETTI ANA PIA; GÓRSKI KONRAD; ESPÍNOLA LUIS ALBERTO; ABRIAL ELIE; AMSLER MARIO LUIS; PAIRA ALDO RAUL

La Plata, Buenos Aires

Congreso; V Congreso Internacional sobre cambio climático y desarrollo sostenible.; 2016

Universidad Nacional de La Plata

We analysed the effects of decadal and annual hydrologic fluctuations on freshwater fisheries catches in the Middle Paraná River for a period of six decades from the 1930s to the 1980s. We first analysed changes in the flow regime of the Paraná River for the period between 1930s and 1980s, with focus on the variations of the flood pulse. To build and compare flow typology among years, we used cluster analysis. Principal component analysis (PCA) was used to assess overall similarity of flows among years. The fisheries catch analysed (1935-1983) were obtained along this river corridor. The obtained data consisted of landing reports on monthly/annual catches (total and by species) in ports along the Paraná River. Differences in total catches among decades were tested using a one-way permutational analysis (PERMANOVA). The canonical analysis of the principal coordinates (CAP) was used to assess temporal patterns of similarity in fish catches per decades. To analysed the effects of flow regime variables on the variation of fish commercial catches we used distance-based redundancy analyses (dbRDAs). The climatic fluctuations in this period strongly affected the hydrology of the Middle Paraná River and the characteristics of its flow regime. The magnitude of floods as well as maximum, minimum and mean water levels increased progressively from 1930s until the 1980s concomitantly with increasing frequency and intensity of ENSO events that resulted in differentiation of distinct hydrological periods. The flood pulses were significantly more frequent and of greater magnitudes during the 1970s and 1980s. These large floods resulted in increased commercial fish catches in the 1980s, possibly due to enhanced recruitment. Specifically, large floods increased the commercial fish catches two years later. This effect was stronger for species that use floodplain habitats as areas of reproduction and larval nurseries, such as Prochilodus lineatus. We conclude that the natural flow regime of the Paraná River and perhaps other large subtropical rivers must be preserved in order to sustain their productive fisheries.