Integrating key ecosystem components into stock assessment models for fishery management

Climate change is leading to substantial environmental shifts worldwide, and hence to changes in ecosystem functioning, food webs and species distributions. Ecosystem-Based Fisheries Management (EBFM) initiatives have increased, in order to protect the ecological systems that support fisheries production. EBFM has led to more complex models for the assessment of fishery resources, capable of explaining and evaluating the relationships between the stock status and ecosystem components (e.g., changes in predator numbers and environmental variables such as sea surface temperature due to climate change). European anchovy (Engraulis encrasicolus) plays important roles in top-down and bottom-up control within the trophic network of the Adriatic Sea, and is economically important for this basin. Any variation in the biomass of this species would have ecological and economic consequences, leading to the need for close monitoring of this species for resource conservation. Currently, anchovy is assessed using age-structured population dynamics and surplus production models. These models present some limitations as they only consider biological information, survey estimates and data from fishery. It is critically important to develop stock assessments that take account of environmental and ecosystem variables. The integrated stock assessment platform, Stock Synthesis (SS3), will be applied with the aim of developing innovative models to assess the status of small pelagic fishery resources and evaluating the impact of key environmental drivers on these stocks. The analysis will examine whether regional environmental variables such as sea surface temperature (as proxy for reproduction triggers), chlorophyll concentration (as a proxy for food supply), river runoffs and salinity (as a proxy for population distribution) have statistically significant impacts on growth, recruitment and maturation, and hence population biomass.