Ecosystem Modelling in Support of Ecosystem-Based Management in the Caspian

Abstract

Nowadays, resource overexploitation and climate change are worldwide recognised as considerable threats to the sustainable development of socio-economic systems and environment well-being. With a growing evidence, highlighting the uncertain state and future of world fish stocks, new approaches to fisheries management that take account of fishing and climate change effects on ecosystems structure and function are being called for. The ecosystem-based bioresources management (EBBM) is defined as a science-based approach of managing human activities, such as fishing, fish stock enhancement and drivers of pollution/eutrophication, with a view to in parallel conserve and sustainably use in the long-term run, the nature living resources. It is meant to deal with issues such as scientific assessment of the Caspian ecosystem and fisheries, environmental change (including climate), biological interactions, anthropogenic impacts (pollution, overfishing), conservation and recovery of biodiversity (habitats, populations), as well as the social and economic impacts. Major task to promote EBBM in the Caspian region was to also provide the decision-makers with innovative tools to support both traditional and innovative management practices.

This paper describes the construction and application of an ecosystem model of the Caspian using the Ecopath, Ecosim, Ecospace approach (EwE). The EwE model is meant to answer simple, ecosystem-wide questions about the dynamics and the response of the ecosystem to anthropogenic changes. It can help to design policies aimed at implementing EBBM and can provide testable insights into changes that have occurred in the ecosystem.

The study proved that the ecosystem components and various fish populations in the Caspian interact in a rather complex way, even though described by a relatively simple trophic model. The effects of predation and other multi-species interactions, combined with climate change and anthropogenic pressures, create a formidable challenge for the ecosystem and bioresource managers – a challenge that needs new approaches and directions.

The proposed ecosystem model demonstrates its ability to resolve multi-species interactions and habitat preferences and account for environmental and anthropogenic stressors, in the process of evaluating spatial management scenarios.

The most important factor dominating in all possible scenarios is the illegal fishing or IUUC. The main targets of the IUU fishing are the stocks of valuable fish resources, especially sturgeons. Therefore, the control over IUUC must be a priority target for the EBBM, especially when building recovery strategies for sturgeons.

The evaluation of spatial scenarios demonstrates that the effects of protected areas (SPACE) are proportional to the size of the closed areas and specific (for different fish groups) to their placement. SPACEs have to be sufficiently large and to cover the main target fish distribution areas. Effective IUUC control measures need to be enforced inside of the SPACEs and even better in the whole region.

The importance of the benthic pathways is pronounced in the North Caspian. It seems that pelagic and benthic systems are relatively decoupled. However, the relatively high importance of the benthic system may buffer the population explosion of the invasive Mnemiopsis leidyi; as a result the effect of this species in the North Caspian is expected to be less severe compared to other areas of the sea.