The forgotten whale : a bibliometric analysis and literature review of the North Atlantic sei whale Balaenoptera borealis

Abstract

1. A bibliometric analysis of the literature on the sei whale Balaenoptera borealis is presented. Research output on the species is quantified and compared with research on four other whale species. The results show a significant increase in research for all species except the sei whale. Research output is characterized chronologically and by oceanic basin. 2. The species’ distribution, movements, stock structure, feeding, reproduction, abundance, acoustics, mortality and threats are reviewed for the North Atlantic, and the review is complemented with previously unpublished data. 3. Knowledge on the distribution and movements of the sei whale in the North Atlantic is still mainly derived from whaling records. Movement patterns and winter distribution are not clear. Surveys in some known summering areas show that the species has changed its distribution in parts of its previously known range. 4. With the present information, it is impossible to determine whether or not the North Atlantic sei whale population is subdivided into biological units. Abundance estimates are fragmentary and cover a restricted part of the summering habitat. 5. In the North Atlantic, sei whales seem to be stenophagous, feeding almost exclusively on calanoid copepods and euphausiids. On feeding grounds, they are associated with oceanic frontal systems, but how they find and explore these structures has not been fully investigated. 6. The available data on vital rates are based on whaling-derived studies and are 25 years old or older. Despite increasing human and environmentally induced pressures, there are no current estimates for mortality and population trends. 7. Current research needs include the clear definition of stock units, reliable abundance estimates, studies of distribution and migration that incorporate the identification of wintering areas, acquisition of up-to-date data on reproduction and mortality, and investigations into the consequences of environmental changes for the species.