Founder’s Briefs: An occasional series where Mongabay founder Rhett Ayers Butler shares analysis, perspectives and story summaries. Among those who cared about freshwater fish — and there were many — Paul Loiselle stood out not for how loudly he spoke and cared, but for how deeply he understood. His grasp of ichthyology was vast, his judgment trusted across both scientific and aquarium hobbyist circles. But what set him apart was his generosity: He shared his knowledge freely, whether guiding a fellow researcher through a taxonomic tangle or helping identify a fish from a snapshot taken in a far-off river. He was, by vocation and temperament, a bridge builder, between hobbyists and scientists, zoos and field researchers, aquariums and conservationists. For more than four decades, Loiselle was a fixture in both the aquarium trade and academic ichthyology. As curator of freshwater fishes at the New York Aquarium and later as emeritus, he managed species collections with a deep sense of purpose: not just to display biodiversity, but to preserve it. Nowhere was that mission more urgent than in Madagascar. Over 14 years of fieldwork, he helped document its astonishing array of endemic freshwater species, many teetering on the brink of extinction. Two now bear his name: the blotched Madagascar cichlid (Ptychochromis loisellei) and the red-banded Madagascar cichlid (Paretroplus loisellei). A third, Melanotaenia loisellei, hails from Papua New Guinea, evidence of his broader influence. Each is a tribute to a man who believed that even obscure, river-dwelling fish deserved a future. That…This article was originally published on Mongabay