Marine mammal strandings recorded in New Caledonia, South West Pacific Ocean, 1877 to 2022

Context Strandings are an important source of information for estimating marine mammal biodiversity, particularly in data-sparse ocean basins such as Oceania.Aims Here, we report on knowledge acquired from 218 stranding events recorded in the waters of New Caledonia (1877-2022).Methods We investigated spatio-temporal distribution, stable isotope signatures, trace element concentrations, biometry measurements, genetic diversity, and diet, for the four most commonly stranded taxa (dugongs, 35% of events; sperm whales, 19%; Delphinidae, 18%; pygmy and dwarf sperm whales, 14%).Key results Beginning in 1991, reports of stranding events increased (183 events, 322 individuals, 20 species from seven families: Dugongidae, Physeteridae, Delphinidae, Kogiidae, Ziphiidae, Balaenopteridae, Otariidae), with hotspots identified on the west coast (Bourail, Ouano, Noumea) and in Prony Bay. Causes of death were not determined in 84% of stranding events, but were identified in the majority of expert-led necropsies (24 of 29 individuals from 10 species). Yet, valuable information regarding the impact of anthropogenic activities was gathered for some species of concern, such as the endangered dugong (28% human-caused). Since 2016, training and outreach have been provided to rangers, veterinarians, and various public safety officers to support their engagement in the scientific monitoring of marine mammal strandings. A website (www.rescue.ird.nc) was developed to facilitate standardised data collection and storage, and to provide public access to stranding records.Conclusion Although the number of individuals reported here remains modest, this study provides new information on poorly documented species in New Caledonia.Implications Long-term monitoring of strandings can help design effective conservation measures. Contexte Les echouages constituent une source d'informations importante pour estimer la biodiversite des mammiferes marins, en particulier dans les bassins oceaniques pour lesquels les donnees sont rares, comme l'OceanieObjectif Nous presentons ici les connaissances acquises a partir de 218 echouages enregistres dans les eaux de Nouvelle-Caledonie (1877-2022).Methodes Nous avons etudie la distribution spatio-temporelle, les signatures isotopiques, les elements traces, les mesures biometriques, la diversite genetique et le regime alimentaire des quatre taxons les plus frequemment echoues (dugongs, 35% des echouages; cachalots, 19%; Delphinidae, 18% ; cachalots pygmees et nains, 14%).Principaux resultats A partir de 1991, les signalements d'echouages ont augmente (183 evenements, 322 individus, 20 especes de sept familles: Dugongidae, Physeteridae, Delphinidae, Kogiidae, Ziphiidae, Balaenopteridae, Otariidae), avec des points chauds identifies sur la cote ouest de la Grande Terre (Bourail, Ouano, Noumea) et dans la Baie de Prony. Les causes de deces n'ont pas ete determinees pour 84% des echouages, mais elles ont ete identifiees dans la majorite des autopsies realisees par des veterinaires (24 des 29 individus de 10 especes). Des informations precieuses concernant l'impact des activites anthropiques ont ete recueillies pour certaines especes preoccupantes, telles que le dugong, une espece en voie de disparition (28% des echouages d'origine humaine). Depuis 2016, des formations et des activites de sensibilisation ont ete dispensees aux gardes nature, aux veterinaires et a divers agents publics pour soutenir leur engagement dans la surveillance scientifique des echouages de mammiferes marins. Un site Web (www.rescue.ird.nc) a ete developpe pour faciliter la collecte et le stockage de donnees standardisees et pour fournir un acces public aux enregistrements d'echouages.Conclusion Bien que le nombre d'individus signales echoues ici reste modeste, cette etude apporte de nouvelles informations sur des especes peu documentees en Nouvelle-Caledonie.Implications La surveillance a long terme des echouages peut aider a concevoir des mesures de conservation efficaces. Conservation of marine mammals in Oceania is limited by a lack of understanding of these relatively rare, yet emblematic species. Here, we report on significant biological and ecological data acquired from several decades of monitoring strandings in New Caledonia. This increased knowledge may help guide management measures locally and regionally. Photograph by Marine Mammal Stranding Center.This article belongs to the Collection Marine Mammals in the Pacific.