Scientific activities in the fish section focus on three areas:
Littoral fishes of the Arabian Seas Region
The Arabian Seas Region, consisting of the Red Sea, the Gulf of Aden, the Arabian Sea, the Gulf of Oman and The Gulf, are a biogeographic sub-unit within the Indian Ocean. According to our present knowledge, some 2000 fish species occur this region. Research activities in the fish section include an inventory and taxonomic revision of littoral fishes. A zoogeographic analysis is based on this revision. Thus far, research in taxonomy and systematics was based on comparative morphology, but molecular genetic methods will be added in the near future.
The geographical focus of the research activities coincides with the collections’ traditional emphasis on the Western Indian Ocean. The two semi-enclosed northern extensions of the Indian Ocean, the Red Sea and The Gulf, where genetic isolation of organisms increases gradually from south to north, lend themselves as models for studies on marine biogeography and evolutionary biology, because of peculiar hydrographic conditions and the region’s geological history.
The cloudy damselfish (Dascyllus carneus) in Socotra Archipelago. At present, research activities focus on the insufficiently known fish fauna of the Socotra group of islands in the North-western Indian Ocean.
Deep-sea fishes of the Red Sea and the Gulf of Aden
Hydrographic conditions in the Gulf of Aden are quite similar to those in other parts of the Indian Ocean and the deep-sea fish fauna is characterised by cold stenotherm species, while in the Red Sea hydrographic conditions combined with a high degree of isolation from the Indian Ocean result in a secondary deep-sea fish fauna, which is derived from shallow water species. Diversity is fairly low and the degree of endemism (species which occur only here and nowhere else) is very high. Against this background, the diversity of deep-sea fishes is described, patterns of vertical distribution assessed and ecological groups defined as the baseline for a zoogeographical analysis. These studies, which were initiated by W. Klausewitz and his collaborators, are presently undertaken by Uwe Zajonz as part of his doctoral thesis.
These studies are based on a taxonomic revision of the deep-sea fishes of the area. The results are entered into an access data base, which to date is the most comprehensive source of information on this topic. A total of 157 species in 118 genera and 73 families were recorded from the Red Sea, while 340 species in 212 genera and 105 families are known from the Gulf of Aden.
The vertical distribution of each species is mapped and the fish diversity for each depth range assessed. Considering biological and ecological data, ecological groups are defined and the vertical zonation is described using explorative cluster analysis. In the Red Sea, fish population densities decrease with increasing depth. Species diversity is dominated by eel-like fishes (Anguilliformes) with a high number of endemics. According to our present knowledge, 44 species occur exclusively in the Red Sea, which corresponds to an endemism of 28 %.
Harpadon erythraeus, an endemic deep-sea inhabitant of the Red Sea.
Population dynamics of reef fishes
Besides taxonomic research field studies of reef fishes are an important part of the section’s activities. Over extended periods of time reef fishes are counted by species along fixed underwater transect lines. In this way, a complex picture is drawn of the long-term dynamics of fish populations. Thus far, these studies were undertaken in the Gulf of Aqaba, the Sudanese Red Sea, Socotra Archipelago and The Gulf.
Population studies of reef fishes undertaken in The Gulf since 1991 are of particular interest, because they illustrate the effects of catastrophic events on fish assemblages. The Gulf War oil spill caused only temporary damage and fish populations recovered after about three years. The effects of two coral bleaching events in 1996 and 1998, attributable to increased sea surface temperatures and followed by a large-scale coral die-off, were much more dramatic. These events resulted in a decline in the number of species per surface unit and a shift in species composition: in some of the dead reefs, obligatory coral associated species disappeared.
With a delay of about two years following the coral bleaching event, a decline in reef fish assemblages was observed. Strictly coral associated species, like the Arabian butterflyfish (Chaetodon melapterus) were most severely affected, while population densities of the Arabian surgeonfish (Acanthurus sohal), a species which feeds on algae in shallow waters, increased.
Taxonomy and zoogeography of Middle Eastern freshwater fishes
Globally, the Middle East is the only transition zone between three major biogeographic units, the Palaearctic, the Afrotropical and the Oriental realms. Since the Miocene a faunal exchange took place in this region via ever changing river networks. With increasing aridity since the late Miocene, river courses were isolated from each other. Research activities focus on the reconstruction of pathways of migration, which fish populations used in a faunal exchange between Europe, Asia and Africa via the Middle Eastern land-bridge and speciation processes in this transition and retraction zone as a result of increased fragmentation of river systems. At present taxonomic revisions, mapping of distribution patterns and zoogeographic analyses focus on Mesopotamia and the Arabian Peninsula.
Carasobarbus apoensis, an endemic freshwater fish of the Arabian Peninsula.
Identification guides for fisheries purposes
With a horizontal and vertical extension of fishing grounds and a diversification in species compositions of catches and landings, the marine environment is increasingly threatened by unsustainable fisheries practices. Against this background there is an urgent need of taxonomic expertise for fisheries planning and management. Since many years the fish section co-operates with the biotaxonomic programme of the Food and Agriculture Organization (FAO) of the United Nations, making available the results of taxonomic baseline research for the practical requirements of fisheries management and marine environmental conservation. With the joint project “Species Identification Guide for Fishery Purposes, Eastern Central Pacific” FAO and Senckenberg replied to a request by the Governments of Central American states, who urgently needed an identification guide for the planning and management of their fisheries. A guide book of three volumes and more than 1800 pages was produced, which for the first time provided illustrated identification keys and descriptions of all marine species of potential economic and/or environmental importance from macroalgae to marine mammals. Previously there had only been scattered, largely unpublished information of limited reliability, hence more than 60 taxonomists contributed original information to these books. The manuscripts were tested in the field in Central America for completeness and accuracy of the keys. These field exercises were combined with training of regional fisheries biologists in the use of identification keys and the collection of reliable fisheries data at the species level.
Subsequently, again in co-operation with FAO, an identification guide to the marine flora and fauna of The Gulf was produced. For the first time all fish species known from The Gulf were briefly described and illustrated. Other joint projects are planned.
Fischer, W., Krupp, F., Schneider, W., Sommer, C., Carpenter, K.E. & Niem, V.H. (eds) 1995. Guia FAO para la identificación de especies para los fines de la pesca. Pacífico centro-oriental. 3 vols, 1813 pp. FAO, Rome.
Carpenter, K., Krupp, F., Jones, D.J. & Zajonz, U. 1997. FAO Species Identification Guide for Fishery Purposes. The Living Marine Resources of Kuwait, Eastern Saudi Arabia, Bahrain, Qatar and the United Arab Emirates. 311 pp. FAO, Rome.
Ecology of the fishes of the Rhine River
Right from the onset the Rhine River and its tributaries received special attention. Species inventories, which started at the local level, provided information about the composition of fish assemblages and ecological requirements of individual species. These data were used for the compilation of distribution maps and red lists for the State of Hesse and at the federal level. Based on the ecological information collated, measures for the conservation of freshwater fishes were proposed.
Wild carp spawning in the Rhine River.
For the last 20 years, fish population dynamics of the upper Rhine River have been closely monitored. The entire German sector of this river was surveyed with funds from the Federal Ministry of Environment. The assessment of fish larvae and juveniles received special attention. They are important ecological indicators, providing insight into faunal dynamics. They are also used for ecological classifications.
Since 1995 the fish section co-operates with the chair of environmental conservation at the University of Marburg in the execution of the German-Ukrainian project “Integrated Ecological Analysis of the Dniester”. Together with colleagues from Ukraine the fish fauna is inventoried and human-induced changes are recorded in order to develop recommendations for a sustainable use of fisheries resources.