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Fisheries Biology should deliver the necessary knowledge on the biology, ecology and population dynamics of exploited (or potentially exploited) species to enable and ensure a sustainable fisheries and management of the resource. The Ecosystem Approach to Fisheries (EAF) requires the investigation of the biology of the species, the structure of the fish communities, processes and carrying capacity in the ecosystem and the interrelationships between compartments of the system.

A key requirement for understanding the status and development of a fish stock and its response to environmental changes is in the early life stages of the species. Eggs and larvae are the most vulnerable stages related to abiotic impacts or predators. Physiological constraints impact distribution and survival of the young stages and have a direct influence on year class strengths. Estuaries along tropical coasts play an important role as nursery areas for many species relevant to coastal fisheries.

Small scale fisheries are of outstanding importance for the protein supply of local populations along tropical coasts. However, in most cases the catches of the artisanal fishermen are poorly or not registered and do not appear in any official statistics. The biology and distribution of many species that are exploited are poorly studied or unknown, and stocks may be depleted before we even have the chance to learn their role in the ecosystem. This development leads to a decrease in biodiversity and may influence the stability of the coastal ecosystems.

The overall goal of the research of this working group is to investigate the impact of a variable and changing environment on fish communities, the growth and condition of fishes in coastal waters and their exploitability through fisheries:

Growth and life history patterns of fishes is a central part of the working group’s activities. Emphasis is put on the investigation of otoliths. The analysis of otolith microstructure and chemistry provides information on daily-based growth and allows the understanding of individual life histories of fish and thus a more detailed understanding of species-specific habitat use and related ecological processes.

The spatial connectivity of fishes between nursery and offshore areas can be investigated by means of otolith chemistry to clarify the importance of coastal areas for shelf populations. The growth and productivity potential can be estimated by relating growth performance directly to environmental factors such as temperature, oxygen or water mass in toto.

Migration and transport processes are important in the life of fishes and their knowledge is crucial for a proper management of stocks. The question of connectivity of populations between different ecosystems is prominent. Aquatic animals use several ecosystems during their lifetime.

Coastal systems such as mangroves, seagrass meadows or coral reefs may serve as nurseries for species that normally dwell on the continental shelf or go even beyond the shelf edge and use the special environment of offshore seamounts for feeding. The understanding of these migratory pathways is of great importance for management aspects. Obviously, the location of MPAs, the definition of temporal and spatial resting zones has to consider the migratory behaviour of the target species.

The role of a species in an ecosystem is partly defined by its position in the food web. Early stages build a link between small food organisms such as copepods and juvenile or adult fish. The survival capabilities of the early stages therefore are crucial for the development of a fish population. We investigate with traditional microscope and modern biochemical methods the trophic position of species in the system, their growth potential and condition to understand failure, success and variability in recruitment processes.

Physiological adaptations to temperature and oxygen are key factors influencing the physiology of fish. While the impact of temperature has been studied intensively in many different aquatic species, the role of oxygen is not that clear. Tolerance against low oxygen concentrations varies from species to species.

While some demersal fishes and crustaceans can cope with almost oxygen-free conditions for a short time, other species have very high thresholds and seem to be impacted by oxygen concentrations of medium ranges. Within the project GENUS (Geochemistry and Ecology of the Namibian Upwelling System) we are investigating distribution, growth and physiological performance of early stages of key species of the system.

Capacity development is an important measure to strengthen the capability of tropical countries to implement a better and sustainable management of their living coastal resources. We engage wherever possible in this area by providing hands-on training for students, PhD-candidates and young researchers or by implementing special courses in Bremen or at the institutes of our project partners abroad.

Group leader
Dr. Werner Ekau

Postdocs
Dr. Britta Grote

PhD students
Simon Geist
Nadine Moroff
Beau Tjizoo
Gustavo Adolfo Castellanos Galindo (DAAD/CEMARIN)
Marianna Audfroid Calderon

Diploma / MSc / BSc students
Katharina Michalowski (Diploma)
Katharina Schwinghammer (BSc)
Hans Sloterdijk (ISATEC)
Cephas Zuh (ISATEC)
Lorena Dandawa (ISATEC)
Paul Tuda (ISATEC)
Kalvis Grinvalds (ISATEC)
Lara Kim Hünerlage (MarBiol)
Maya Bode (MarBiol)

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