An Integrated Traits Resilience Assessment of Mediterranean fisheries landings

1. An increasing number of studies have been examining the functional configuration of biological communities or ecosystems by using biological traits. 2. Here, we investigate the temporal dynamics and resilience of the trait composition in Mediterranean fisheries landings over 31 years (1985-2015) 3. We transcribed the FAO Mediterranean landings dataset for a total of 101 marine species into a dataset of 23 traits related to the life cycle, distribution, ecology and behaviour of fish and other marine animals. Mediterranean sea surface temperature (SST) was evaluated as a potential driver of the trait composition. Trait dynamics were evaluated both separately by trait and by developing an Integrated Traits Resilience Assessment (ITRA) using ten selected traits. ITRA is a variation of the Integrated Resilience Assessment (IRA), a method to infer resilience dynamics and build stability landscapes of complex natural systems. 4. Changes in trait dynamics were documented both for individual traits and for the entire traits “system”, and a relevant regime shift was detected in the second half of the 1990s. At that point, the landed traits system switched to higher optimal temperature, more summer spawning, shorter life span, smaller maximum size and wider depth distribution. This shift was found to be a lagged discontinuous response to sea warming, which gradually eroded the resilience of the original state of the traits system, leading it into a new basin of attraction. 5. The finding that, apart from changes in species composition, the composition of biological traits in fisheries landings has also changed, indicates that functional changes may have occurred in the Mediterranean ecosystem. Apart from functional traits (i.e. related to survival, growth and spawning) that can be linked to these changes, the inclusion of ecological traits (related to environmental conditions preferences) in the analyses indicates potential mechanisms explaining the observed shift. Our findings suggest that changes in the Mediterranean ecosystems are evidently deeper than previously thought, with profound implications for the management of this highly impacted sea.

JRC.D.2 - Water and Marine Resources