Concluding Remarks on the Halifax Diadromy Symposium
Robert M. McDowall
The Halifax symposium of 2007 was viewed as an opportunity to review progress in our understanding of the place of diadromy in fish and fisheries approximately 20 years after the 1986 meeting in Boston, also sponsored by the American Fisheries Society, and to address challenges for the future. Clearly, diadromous fishes, despite their relatively small number, are of profound importance across a wide range of values from economic to conservation, and this symposium, and others before it, such as at Hilo, Hawai’i and Bordeaux, France in 2005, reflect that importance.
The Halifax symposium was international, and although scientists attending from the United States and Canada were most abundant, there were people from, or discussing the fish species of, Albania, Argentina, Asia (by an Australian), Bangladesh, Chile, France, Iraq, Italy, Japan, the Netherlands, New Zealand, Norway, Peru, Russia, and Sweden. Some of the larger contingents from outside North America were from New Zealand and Japan, perhaps a reflection of the importance of diadromy to fish ecology and fisheries in these countries. Somewhat ironically, it was those from New Zealand and Japan who came the furthest to attend the Halifax meeting. Missing were papers on diadromous fishes from Africa, some parts of Asia, Australia, and some of Europe. The small islands of the tropical and subtropical Indo-West Pacific were only sparingly covered (Iida et al. 2009, this volume), as well as the Caribbean and Central America (Bell 2009, this volume) and the warm Neotropics. A particular and, I think, unfortunate absence was of biologists working on diadromous fishes across French Polynesia and the Mascarene Islands in the western Indian Ocean, who have a vigorous research program on the amphidromous fishes of these islands (Keith et al. 1999, 2002, 2006; Keith 2003; Berrebi et al. 2006; Hoareau et al. 2007).
I have real concerns about the lack of knowledge of diadromy (if any) in the great tropical rivers, like the Mekong, Zambezi, Congo, Amazon, Ganges, Nile, and so many more. At present, there is little indication of diadromous species in many of these rivers (McDowall 1988), but is this an accurate representation of what happens there? Similarly, we seem to know relatively little of the diadromous hilsa Tenualosa ilisha, though Siddique, from Bangladesh, provided some background to such species there (Siddique 2009, this volume).
Major conservation issues relate to the state of the Caspian and Black seas, and the Sea of Azov, but there was no reference to their diadromous fish and fisheries at the Halifax symposium—an unfortunate absence.