Abstract
The increase in the research of cetacean surveys on the Brazilian coast has brought new data on the distribution of species never reported before. The present work reviews the current knowledge on cetaceans species and extends this knowledge with an analysis of cetaceans stranded in the Parnaiba Delta, on the coast of Maranhão State, Brazil. The studies on cetacean diversity on the coast of the Parnaíba Delta were made from August 2004 to August 2006. Fourteen strandings were reported, representing six distinct species, such as the estuarine dolphin (Sotalia guianensis), humpback whale (Megaptera novaeangliae), Bryde's whales (Balaenoptera edeni), dwarf minke whale (Balaenoptera acutorostrata), pigmy killer whale (Feresa attenuata), sperm whale (Physeter macrocephalus) and two specimens which have not yet been identified. The significant degree of cetacean diversity in the region shows that the Parnaíba Delta is, possibly, of an important area for cetacean studies in Brasil.
Highlights
The monitoring of beachcast cetaceans can provide information on spatial distribution, seasonal movements and mortality (Woodhouse, 1987)
Six species of cetaceans were recorded as stranded on the Parnaiba Delta during the last two decades (Figure 2)
The cooperation of the fishermen facilitated the detection of large animal strandings, which remained exposed on the beach for long periods, and so are more noticeable and are more likely to be recorded using the fishermen as guides through the waters of the Parnaiba Delta
Summary
The monitoring of beachcast cetaceans can provide information on spatial distribution, seasonal movements and mortality (Woodhouse, 1987). Data collection in prolonged periods and stranding locations can reveal some changes on population relative abundance (Sergeant, 1979). The report of cetacean stranding is, in general, an efficient method to obtain information about these animals. The obtained data may be partial, but may allow different studies (Raga et al, 1991). Fishermen activities, pollution and ship collisions can be considered the main threats and responsible for a high number of cetacean strandings around the world. As humans increase their exploitation of aquatic resources, individual dolphins, porpoises, and whales suffer, their societies are disrupted and populations decline (Whitehead et al, 2000)
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