The curation and organization of samples for molecular studies in the fish collection of Museu de História Natural da Bahia, Bahia, Brazil

The ichthyological collection at the Museu de História Natural da Bahia (MHNBA) in Bahia, Brazil, started in the 1970s, initially focusing on marine species. Between 2003 and 2024, several field expeditions were conducted to explore the taxonomic and geographic diversity of freshwater species across eight Brazilian ecoregions. Since 2005, and especially in the last seven years, expeditions funded by Brazilian development agencies have been carried out to collect fish tissues, establishing the fish tissue collection at MHNBA. In 2019, the collection began to be digitized and a standardized sample management procedure was implemented. Currently, the ichthyological collection at MHNBA, with material preserved in formalin, consists of approximately 10.500 catalogued lots from about 1,600 locations, stored in 70% alcohol and housed in sliding cabinets. The tissue collection is stored in vertical freezers at -18°C, organized in Eppendorf tubes (aliquots and whole specimens), and distributed in numbered boxes and drawers. All information is recorded in the cataloguing system to facilitate access and curation. To date, 6,044 specimens from 105 genera and 263 species have been catalogued. This collection also includes samples of 29 paratypes from four freshwater fish species. The number of species is likely underestimated, as individuals identified only to the generic level were excluded from the count, and many lots still need to be catalogued. Additionally, the collection includes samples of species that are uncommon in tissue collections, such as Hasemania piatan, Lignobrycon myersi, Moenkhausia diamantina, and Hyphessobrycon negodagua. The fish tissue collection at MHNBA is one of the most significant in the Brazilian Northeast and has been instrumental in developing various projects, primarily focused on the integrative taxonomy and phylogeography of freshwater fishes.