Parsimony analysis to track fish living areas via isotopic signatures in otoliths

Conceptual parsimony is widely applied to formulate living area hypotheses regarding isotopic tracking of fish. Parsimony, conceptually or not, already helps researchers to make decisions about the most likely sequences of isotopic-inferred movements for each fish individually. Beyond the individual hypotheses, the parsimony analysis (PA) was also applied here to synthesize collective data on strontium isotopic fractions in otoliths and assess the migratory routes of five fish species. The isotopic “signatures” of 26 environments of the Verde River, its tributaries, and the Paraná River in Brazil were used to track the isotopic histories contained in the otoliths. The indications of the presence or absence of each individual in each area were used as data input in the parsimony analysis of migratory routes (PAMRs), which returned cladograms grouping the living areas paired by the most important routes, a new analytical combination. The PAMRs separated the living areas into groups of environments that coincide with the compartmentalization of the Verde River basin and its connectivity, including the manual transposition of some specimens. A frequentist index allowed us to compare the intensity of manual transposition with the intensity of active migratory routes. This study case was directly applied to evaluate conservation measures for migratory ichthyofauna, but the conceptual and methodological tools are replicable for summarizing the data for migratory routes of any animal datasets containing individual life stories.