cetaceans of the congo river estuary, drc: the first inventory, aided by citizen science

The first inventory of cetacean diversity in coastal waters of the congo river estuary, democratic republic of the congo, was obtained between may 2021 and april 2022, through incidental sightings (n=17) reported mainly by artisanal fishers and direct observations of bycatches at fish landing sites. confirmed records include five odontocete species: four delphinidae: delphinus capensis gray, pseudorca crassidens (owen), stenella frontalis (g. cuvier), tursiops truncatus (montagu); one kogiidae: kogia sima (owen). there was one mysticete, balaenopteridae: megaptera novaeangliae (borowski). of six small cetaceans documented landed for use as aquatic bushmeat, four (66.7%) were t. truncatus. megaptera novaeangliae was the most frequently sighted cetacean (47.1% of reported sightings), registered between 17 may–3 september 2021, with a seasonality (austral winter) consistent with the se atlantic breeding stock (‘b-stock’). all information was collected by locals, the at-sea sightings by trained fishermen in a citizen science framework. the main benefits included a welcome marine conservation educational component, and low-cost, opportunistic fishing boat use. shortfalls comprised a deficiency in scientific detail and effort quantification, occasional data loss and lack of biological sampling. however, in a remote coastal region like the drc’s congo river estuary, where marine mammals have never before been studied, local citizen science methodology proved effective and, after adjustments, should be scaled-up.