When natural history collections reveal secrets on data deficient threatened species: Atlantic seahorses as a case study

Natural history collections from museums and private institutions can play an important role supporting decisions in biodiversity conservation. Seahorse populations have suffered a worldwide decline, while many areas remain data deficient including areas subjected to heavy commercial trading, such as the coasts of West Africa. In this work, seahorse collections from museums and public institutions in Macaronesia (Azores, Madeira and the Canary Islands) were initially reviewed (1) to identify specimens not previously determined, and (2) to correct species determinations from Macaronesia and adjacent West African coasts. The morphological data (3) were tested for phenotypic variation of seahorses within and between Macaronesia and adjacent West African coasts. The presence of Hippocampus hippocampus (short-snouted seahorse) and Hippocampus algiricus (West African seahorse) was confirmed for the area, including new sightings along previous geographical distribution ranges. Morphological analyses partitioned seahorse species and several morphotypes within and between Macaronesia and adjacent West African coasts. This phenotypic plasticity was associated with cranial morphology. Such differences are a useful tool for tracking seahorse populations of varying species and origins. New information presented here, is valuable for improving the management and conservation of seahorses, particularly in areas threatened by illegal trading or other anthropogenic activities.