Comparing data-based indicators across upwelling and comparable systems for communicating ecosystem states and trends

A suite of ecological indicators was selected for communicating, in a comparable way, how fishing affects the state of several upwelling ecosystems and others in which small pelagic fish play key ecological roles. Detailed background and understanding of system-specific processes and changes is needed for proper interpretation of results. In particular, environmental forcing is important in driving dynamics in upwelling systems; fishing impacts cannot be understood without understanding the corresponding dynamics of the environment. The Saharan Coastal (Morocco) and southern Benguela, both having experienced upsurges in low-trophic-level species, differed from other ecosystems when considering indicator trends. The ecosystem off Portugal emerged as showing reduced signs of fishing impacts in recent years, although the change may also be reflecting climate change favouring recruitment and abundance of demersal stocks. The indicator suite confirmed general understanding that the Mediterranean ecosystems have been notably degraded for several decades. Results and conclusions from this descriptive synthesis are compared with other comparisons of more complex, model-derived indicators. Even in upwelling and comparable systems, the simple data-based indicators are useful in synthesizing information on the status of an ecosystem, in particular on the ecosystem effects of fishing, to provide an ecological diagnosis at the ecosystem level, to be used in decision-making. Indicators of recent ecosystem state and trends over time are needed to assess the effects of fishing, but more indicators measuring biodiversity attributes and environmental change would complement the suite, providing fuller assessment of the status of upwelling and comparable ecosystems.