RECENT RESEARCH TOPICS AND
PROJECTS

I) HABITAT MODELS FOR FISH SPECIES AND OTHER TAXA

Only those species which habitat use is known in detail, can be understand in its ecological demands and effectively protected. Therefore, there is a great need to produce predictive models to relate biological (community, population and individual) data to environmental factors - such that the development of methods to be used to help interpret and predict changes in environments and faunas. Habitat suitability models are powerful mathematical tools to predict faunal compositions under present, future and historical conditions, if the habitat preferences of the species and the most important environmental parameters of the habitats are known or could be derived or assumed. The preferred option to develop accurate mathematical models is habitat modeling based on special research surveys relating presence and absence of fish species and their life stages together with habitat environmental parameters. However, the ZMH fish collection provides valuable data to validate the models. Furthermore, collection data can be used to develop models explaining large-scale changes in distribution areas of species in relation to environmental factors, including climate change and anthropogenic impact, in particular when linked with other global data banks. Erstwhile habitat models were based only on very general expert knowledge of habitat use of the species. Often, they did not provide the opportunity for statistical discrimination and validation and did not include population or individual based parameters and processes. A major goal of our research is therefore to develop new types of habitat models where predictions are based on detailed knowledge of habitat use and population dynamics of fishes and other taxa.

Project BUFI - is an actually running research project in which we analyse habitat use, habitat shift and biodiversity of fishes in typical shore habitats (groyne fields) of the middle Elbe River in Germany. The project is sponsored by the Federal Institute of Hydrology. The major aim of the project is to develop habitat models which predictions are based on detailed knowledge of habitat use of dominant fish species and their life stages. Discrimination and validation of those models are possible and performed using receiver operating characteristic curves. To obtain accurate models, the habitat preferences of the species have to be estimated very carefully and for each of the species life history stages. Input data for the models are presence and abscence of fish species and life stages obtained using point abundance sampling (Fig. 1). Statistical models predicting the habitat suitability of the fish fauna are developed based on logistic regressions. These models can predict habitat suitability on a very small-scale resolution (Fig. 2).

II) BIODIVERSITY, ECOLOGY AND SPECIATION OF ESTUARINE AND FLUVIAL FISHES

Estuaries and large rivers are a focus of human activity. In few other places do the activities of fishers (Fig. 3), industrialists, shippers, farmers, conservationists, sports enthusiasts and biologists overlap to such extent. Especially the fishes of estuaries already face one of the most rigorous of aquatic environments. Many of the species living in estuaries may be operating at or close to their physiological limits, but despite this, species diversity and productivity are high. Our research topics are to detect and explain biodiversity and organization of estuarine and fluvial fish fauna in space and time and to investigate trophic interactions and importance as well as population dynamics of the key species. Our actual studies in this research field focuses on the Elbe Estuary and connected river stretches and its tributaries. We perform research on invasive species, like round goby (Neogobius melanostomus), large predatory species, like zander (Sander lucioperca), and diadromous species, like lampreys, smelt, houting, Atlantic Salmon, trout, flounder, European eel and shads (Alosinae), a subfamily of herrings (Clupeidae). We use morphological methods (Fig. 4) in combination with micro-chemical methods, e.g. Strontium (Sr)/Calcium (Ca) ratio in otoliths, to clarify relationships of different stocks and to detect typical migration patterns, their individual migration variability and possible relationships between migration patterns and speciation processes. Estuaries and connected river stretches play a crucial role in the life cycles of diadromous species by providing a route for their migration to and from their spawning and main feeding areas. It is generally assumed that diadromous fish species show the tendency to have less genetic structuring among the discrete populations in comparison to entirely freshwater populations. However, among species with different migration patterns like anadromous, catadromous and amphidromous migration may exist different levels of suppressed genetic divergence among separate riverine stocks. Furthermore is to take into account that the establishment of non diadromous populations in lakes could facilitate speciation. The establishment of landlocked stocks and homing allows genetic differences to accumulate. Additionally, there are a number of cases of congeneric diadromous species with broadly overlapping distributions, which indicate that speciation still takes place. Definitely, these different appearances need to be studied in detail.

Project "Distribution and ecological niche of the invasive Round Goby Neogobius melanostomus (Pallas, 1814) in North-western Germany"

Round goby is a relatively small bottom fish with a maximum length of 25 centimeter. It is a feeding generalist with a diversified food intake and is also able to tolerate various environmental conditions. Native range of N. melanostomus is in the brackish parts of the Sea of Azov, the Black Sea, and the Caspian basins. After introduction into the Gulf of Gdańsk, Poland, in 1990, the invasive Round Goby spread its range along the coast of the Baltic Sea. Its western distribution boarder probably reached the Baltic Sea coast of Schleswig- Holstein, Germany, in the year 2005 or 2006.
Since 2011 we perform research-fisheries in the Kiel Canal and in the river Trave system in Schleswig-Holstein, Germany, in order to detect colonized habitats in brackish and freshwater ecosystems (Fig. 5). Population biology, habitat use, distribution, density, and the role of Round Goby in the food web of the water bodies are investigated. Therefore not only N. melanostomus was studied but also Pikeperch Sander lucioperca (Linnaeus, 1758) as one of the possible predators of Round Gobies. In addition to the outdoor research activities we conduct aquaria experiments (for example on substrate and salinity preference of Round Goby) in the Zoological Museum, University of Hamburg. The potential spreading of Round Goby in the future is being predicted with habitat models.

Projects Klimzug-Nord and ESTRADE

http://klimzug-nord.de/index.php/lang/en/page/2009-07-21-KLIMZUG-NORD-Home

http://www.biologie.uni-hamburg.de/bzf/estrade/index.htm

III) SYSTEMATICS, MORHOLOGY, TAXONOMY AND HABITAT USE OF ELASMOBRANCHS, OSTARIOCLUPEOMORPHA AND PERCOMORPHA

This is a central research topic of the Section Ichthyology. An important basis for this task is the ZMH fish collection with its abundant and worldwide material of adult and larval fishes from marine and freshwater areas. Actually, the collection is completed with outstanding species which are mainly collected along the Atlantic seaboard, in the North and Baltic Seas and in their estuaries and tributaries. Actually we investigate, e.g., the systematics and habitat use of elasmobranchs from the shelf of Thailand, changes in distribution areas of species of oreosomatids and gobiids in the Atlantic Ocean, and the diversity of Ostarioclupeomorpha and Percomorpha in coral reefs of the Red Sea (Fig. 6) and in European river systems and estuaries. Furthermore, we develop identification keys for fish larvae in European fresh and estuarine waters in the framework of an international cooperation. Ostarioclupeomorpha and Percomorpha comprise together about two thirds of all known recent fish species worldwide and have populated almost all aquatic habitats. Especially, information on their early life stages is still incomplete. The newly hatched larvae, from the yolk-sac stage and preflexion stage to flexion and postflexion or juvenile stage exhibit a varity of changes in their ecology and as well in meristic and morphometric features. For instance, morphological features of fish larvae like, e.g., body shape, larval pigmentation, number and position of fins, number of fin rays, alimentary canal, position of anal opening, spines and spinous ridges on head and operculum, etc. change during larval development. Such variability makes fish larvae difficult to identify. Therefore, there is an ongoing great need of accurate taxonomic information on fish larvae of several groups. The keys are based on different identification tables for different developmental stages of each of the relevant species (Fig. 7).

Project "Taxonomy and distribution of deep-water chondrichthyans from the West Indian Ocean"

Cartilaginous fish are especially susceptible to overfishing because the lifestyle of many species is characterized by late attainment of sexual maturity, slow growth and low reproductive output. Despite the population declines of many species, their taxonomic status and distribution is often unclear and there are still many unknown species.
The chondrichthyan fish fauna of the East African continental slope has so far hardly been investigated, although there is obviously a very high diversity of cartilaginous fish species. In the course of our investigations we are describing several new chondrichthyan species, especially skates from the family Rajidae (Fig. 8). Furthermore, we are planning to develop a checklist and a regional guide for the cartilaginous fish species of this area. In the framework of this project we are cooperating with specialists from other institutions from around the world. The results of this project will also supply important information for the assessment of the conservation status of species and for the establishment of management and protection programs.