Whale mortality from ship strikes in Ecuador and West Africa

Abstract

We document two unusual cases of a Bryde's and a sei whale struck by container cargo vessels and draped over the bow bulb, respectively in the Southeast Pacific and the Eastern Tropical Atlantic. The 207m-length P&O Nedlloyd Pantanal collided with an adult Bryde's whale Balaenoptera edeni in the southern Gulf of Guayaquil, Ecuador, on 10 December 2004. The whale showed massive dermal hematoma indicating that it was alive when struck. Similarly, the container ship OSNA Bruck arrived at Dakar port, Senegal, on 19 March 1998 with the fresh carcass of a juvenile sei whale B. borealis on its bow bulb. The collision occurred between Las Palmas, Gran Canaria and Dakar, Senegal. Freshly dead balaenopterids can hardly be picked up by ships since they sink at death and do not float until decomposition and bloating sets in. A review of previous cases show that ship strikes are rarely recorded in these regions, partly due to the lack of regulations, including no reporting obligation. However, the case studies reveal that another factor may severely augment under-reporting of ship strike mortality. In both instances the crew became aware of the collision only upon arrival at port, suggesting that whales which are hit and killed or wounded, but do not become draped over the bow bulb (if the vessel has one), go unnoticed. The probability of bow draping may be low, and modelling should be attempted. National authorities are encouraged to improve data collection and introduce regulations such as mandatory reporting. These are the first fully documented, fatal whale collisions in Ecuador and West Africa (south of the Canary Islands), and the first struck and killed Bryde's whale in the Southeast Pacific.