UHH: Biozentrum Grindel und Zoologisches Museum

RECENT RESEARCH TOPICS AND PROJECTS

I) BIODIVERSITY AND SYSTEMATICS OF FISHES OF THE ATLANTIC OCEAN AND ADJACENT WATERS

Analysis of biodiversity and systematics of fishes of the Atlantic Ocean and adjacent waters are central research topics of the Section Ichthyology. An important basis for this research task is the ZMH fish collection with its abundant material of fishes from Atlantic areas (mainly former ISH collection) which comprises two thirds of all of the described Atlantic fish species. 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.

Fig. 1: Determination and measurement of flatfishes from a research catch with a bottom trawl in ICES subdivision 24 of the Baltic Sea.

ANFIOS - a recent research project has focused on biodiversity in space and time of NATURA 2000 fish species in the Baltic Sea and its transitional waters to the North Sea. This project was assigned to the German Oceanographic Museum and the University of Rostock and was completed by the University of Hamburg. The project was sponsored by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety and the Federal State of Mecklenburg-Vorpommern. In the framework of the project, the following sources of data were analysed: records from museum fish collections and databanks, research fisheries with special trawls (Fig. 1), use of underwater video technique, records from fisheries research, catches from commercial and recreational fisheries, commercial catch statistics and relevant publications. The analyses resulted in 387 spatially and temporally different actual records of NATURA 2000 fish species within ICES subdivisions 20-27 since 1990. For the time period until 1989, overall 2,027 historical records of the relevant species were obtained. For instance, 326 historical records of Atlantic sturgeon were estimated within ICES subdivisions 20-27.

The 2007 project report (Erfassung_FFH_Fischarten_Nordsee-Ostsee_2007.pdf) can be downloaded under:
http://www.habitatmarenatura2000.de/en/downloads.php.

II) TAXONOMY AND MORPHOLOGY OF SELECTED GROUPS AND DEVELOPMENTAL STAGES OF OSTARIOCLUPEOMORPHA AND PERCOMORPHA

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.

Fig. 2: Different developmental stages of selected cyprinids a) yolk-sac stage of Rutilus rutilus (Linnaeus, 1758); b) flexion stage of Cyprinus carpio Linnaeus, 1758; c) juvenile stage of Romanogobio belingi (Slastenenko, 1934). © Monika Hänel

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.

Actually we develop IDENTIFICATION KEYS FOR FISH LARVAE in European waters to fill parts of this gap in knowledge. The keys are based on different identification tables for different developmental stages of each of the relevant species (Fig. 2).

III) DOES DIADROMY REALLY SUPPRESS SPECIATION AND DIVERSITY OF FISHES?

It is often assumed that migration of individuals generally results in gene flow among discrete populations of species. Therefore, 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 catadromous, anadromous 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 nondiadromous 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.

Fig. 3: Selection of morphometric measurements used in studies on Alosinae systematics.

Our actual studies in this research field focus on SYSTEMATICS, BIODIVERSITY, SPECIATION AND ECOLOGY OF SHADS (Alosinae), a subfamily of herrings (Clupeidae) which are widely distributed. Since no accurate analysis of alosine phylogeny has occurred to date, we use morphological methods (Fig. 3) in combination with genetic methods and biochemical analysis, e.g. to clarify phylogenetic relationships of groups within the shads. Furthermore, we perform measurements of Strontium (Sr)/Calcium (Ca) ratio in otoliths of shads to detect typical migration patterns of species and/or subspecies, their individual migration variability and possible relationships between migration patterns and speciation processes.

IV) MATHEMATICAL MODELS FOR HABITAT USE OF FISH SPECIES AND THEIR LIFE STAGES

Only those fish species which habitat use is known in detail, can be 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 aquatic environments and fish faunas. Since the 1980ties habitat modelling is a powerful tool to analyse the anthropological impact on the suitability of habitat especially for fishes and other aquatic organisms. Furthermore, there is a need to improve fauna-based evaluation indices for the European Water Framework Directive to perform ecological assessments of the aquatic habitats. Especially, the estimation of differences between the historical and actual status of the faunal compositions is difficult, because historical quantitative data of composition and density of fish fauna are scarce. However, habitat models are tools to predict faunal compositions, even under historical conditions, if the habitat preferences of the species and the most important environmental parameters of the habitats are known.

Fig. 4: Point abundance sampling by electro-fishing along the shore of the Elbe River.

BUFI and FISTOB - are two actually running research projects in which we analyse the habitat use, habitat shift and biodiversity of fishes in typical shore habitats (groyne fields) of the Elbe River in Germany. Both projects are sponsored by the Federal Institute of Hydrology. Former habitat models based only on a very general expert knowledge of habitat use of the species, and it has been criticised that those methods do not provide the opportunity for statistical discrimination and validation. The major aim of the projects is therefore to develop new types of habitat models which predictions are mainly based on detailed knowledge of habitat preferences of aquatic animals and their life stages. Discrimination and validation of those models are possible and are 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 abundances and occurrences of fish species and life stages obtained using point abundance sampling (Fig. 4). Statistical models predicting the preference of fish fauna environmental relationships are developed based on multivariate statistical methods, e.g. CCA, and logistic regressions.