Biometric relationships are critical to convert measurement performed at landings (fish with head, tail cut or gutted and gilled) to standardized measurements which can be used in stock assessment and scientific purposes. In the Indian Ocean, while tuna species are relatively well described, there is a critical lack of information for billfish and the interannual and seasonal variations of these relationships are rarely investigated. To cope with this issue, the relationships used at IOTC are coming from other oceans or close species which is not scientifically satisfactory. In this document, we present the biometric relationships for 6 large pelagic species over 267 individuals in 2017 and 2018 from catches of Reunionese longliners. The classical length and weights are established for this species. While the relationships are very neat, further collections are needed to provide robust relationship. This document question our ability to share and build a global biological database at IOTC which can be regularly updated and provided the best scientific knowledge for these relationship. These data could be also used for other scientific needs and could be easily freely accessible as they are not sensitive.