Determining Breathing Frequency of Arapaima Spp. for Improved Fishery Management in the Amazon

Arapaima (Arapaima spp.) are obligate air-breathing fish endemic to the Amazon basin, and one of the world’s most overexploited fish species. Arapaima conservation and management depend on census counts that use air-breathing frequency to estimate fish abundance and set harvest limits. However, these counts depend on breathing rate assumptions, which have never previously been tested. This study examines relationships between breathing frequency and environmental parameters (i.e. temperature, depth, dissolved oxygen) for radio-tagged arapaima (n=17) in an upland river and its floodplain (Lake Ayapuá, Amazonas, Brazil). Multiple linear regression was used to evaluate environmental correlates of breathing frequency. Results show a significant negative relationship between breathing rate and water temperature (p-value = 0.014) and a positive relationship with fish size (p-value = 0.083). We observe average breathing frequency of 16 minutes for adult arapaima (T_L>1 m) and 14.5 minutes for juvenile arapaima (T_L=<1 m). Current management uses assumptions of a 20-minute breathing rate; therefore this study suggests revisions be made to fisheries management protocols to account for area-specific temperatures and size of fish counted. Our results will be used to inform better practices for censuses and improved management, thus helping to conserve populations of arapaima in the Amazon.