Hydrologic variability effects on catches of Prochilodus nigricans in the lower Amazon

Abstract

Flooding events in large rivers, termed flood pulses, expand and contract habitat available for fish populations, affecting fish abundance and catches. Here, we investigated if river hydrologic variability affected catch of curimata (Prochilodus nigricans), a widely distributed and economically important fish species of the Amazon Basin. Using fish catch and fishing effort data for the lower Amazon region collected between 1993 and 2004, we performed an (i) analysis of covariance (ANCOVA) to understand the intra-annual relationship, and (ii) a cross-correlation function (CCF) to assess the inter-annual lag associated between river water levels and catches. We found that the intra-annual relationship between monthly river water levels and monthly catches of P. nigricans was negative, resulting in greater catches during lower river water levels and vice versa. We also found positive correlations with an inter-annual lag of 15-months between river water levels and catch, indicating that years with more extensive flooding lead to greater than normal catches of P. nigricans 15 months later. Increased flooding can be hypothesized to lead to increased survival and growth rates of P. nigricans. This dependency of catches of P. nigricans on river hydrological cycles underscores the threat posed by ongoing hydrological alterations to fish-related food and income security in the region. Further research is necessary to assess the extent to which such hydrological effects can impact multispecies fisheries catches in light of growing levels of fishing pressure.