On the Diversity, Population Ecology, and Biogeography of Myctophidae

1. Introduction An overview of the PhD project of the first author within the framework of an international collaboration on lanternfish (Myctophidae) ecology is given. Mesopelagic fishes play an important trophic role in the open ocean as well as close to steep slopes. Myctophidae in particular display a high diversity that can be used as an indicator of biogeogrpahic distinctness of a specific area. The life history and adaptive strategies at the level of individual populations of myctophid species are poorly documented. In order to integrate these various aspects, a comparitive study has beeen studied. 2. Material The investigations are based on material of the global DANA deep-sea expedition that is deposited at the Zoological Museum, Copenhagen (ZMUC), and on collections from recent pelagic research cruises in deep-water canyons south of Georges\u27 Bank (NW Atlantic), the Canary Islands (Eastern Central Atlantic) and the Gulf of Mexico. 3. Data Analyses and Perspective Data on species composition and spatial distribution of mesopelagic fishes collected off the Canary Islands shows that myctophids are distributed patchily at a rather small spatial scale (Wienerroither 2003). These distribution patterns are consistent with areas characterized by high productivity and specific hydrological phenomena like upwellings and eddies. MOCNESS-catches close to deep-water canyons on the southern edge of Georges\u27 Bank (Wienerroither, Suiblein and Youngbluth 2003) enable an even more detailed analysis of the small-scale distribution of myctophid species. Populations of geographically separated areas will be compared using meristic and morphometric characters to reveal possible adaptations to ecologically different environments. Commercially-targeted fishes as well as marine mammals and birds use myctophid species as important sources of food. Adequate and sustainable ecosystem management require holistic consideration of the food web, with detailed knowledge about the lifecycle and population structure of its components. This necessity is reinforced but also complicated by the insight that geographically separated populations of the same mesopelagic fish species have differing life history data. 4. Literature Cited Wienerroither, R.M. 2003. Species composition of mesopelagic fishes in the area of the Canary Islands, Eastern Central Atlantic. Informes Tecnicos del Instituto Canario de Ciencias Marinas, 9:1-110. Wienerroither, R.M., F. Uiblein & M. Youngbluth 2003. Species composition and distribution patterns of myctophids and associated midwater fishes in the Gulf of Maine, NW Atlantic. Report from the Nanomia research cruise, September 2002, 8pp