AnEco

Context

In recent years, a progressive decline in the size (length and weight) of anchovy (Engraulis encrasicolus) in the Bay of Biscay has been observed across all age classes, and is especially marked in 1- and 2-year-old individuals. This phenomenon has significant ecological implications, as it may alter food webs and ecosystem productivity, as well as direct economic consequences, affecting the commercial value of catches and the profitability of the fleet.

Age-1 individuals account for around 80% of the stock’s total biomass, meaning that their size plays a decisive role in determining both the average size of the population and that of the catches. In this context, studying the early stages of the life cycle (eggs, larvae and juveniles) is key to understanding population dynamics and anticipating the size of the fish that will enter the fishery.

Several hypotheses have been put forward to explain this reduction in size. Recent studies point to a possible influence of ocean warming, although temperature alone does not fully explain the observed variability. Other mechanisms, such as changes in plankton structure, variations in predation pressure, or physical transport processes, also appear to play an important role. In particular, a significant relationship has been identified between the intensity of westward Ekman transport in spring-summer and juvenile size in autumn, explaining a substantial share of the interannual variability in size.

From a socioeconomic perspective, the relative increase in smaller anchovy has changed the structure of fish auction sales, reducing first-sale prices. At the same time, the fleet has adapted its spatial fishing strategies by shifting westwards, which entails higher fuel costs, reduced activity in Basque ports and an overall decline in economic returns, while also increasing uncertainty in decision-making during the fishing season.

The JUVENA scientific survey, carried out annually since 2003, provides key information on juvenile biomass, size and condition in autumn, as well as samples for biological and ecological studies. Integrating these data with other environmental and fisheries variables opens the door to the development of predictive tools capable of anticipating anchovy size and assessing exploitation and management scenarios.

In a management context based on the Total Allowable Catch (TAC), and in light of the debate around quota allocation by Producer Organisations (POs), having predictive information on anchovy size is essential to improve fisheries planning and help the sector adapt to the changes observed.

Objectives

Overall objective
To improve applied knowledge of anchovy population dynamics and the anchovy fishery in the Bay of Biscay by developing tools that support decision-making and enhance the operational efficiency and profitability of the Basque purse seine fleet.

Specific objectives

• To analyse the biological, ecological and environmental factors associated with the decline in anchovy size.
•  To develop a model for predicting anchovy size.
• To develop a sales price model based on size and other relevant variables.
• To characterise the anchovy fishery from a spatial and temporal perspective.
• To assess the economic impact of different quota allocation scenarios by POs.
• To design and develop an operational size prediction tool to support decision-making throughout the fishing season.

Expected impact

The project will make a significant contribution to understanding the processes that regulate anchovy size and survival by integrating biological, ecological, environmental and fisheries information. Its main outcome will be the development of a size prediction tool which, together with price and cost models, will make it possible to simulate fishing scenarios and support the fleet’s strategic decision-making.

This tool will help optimise economic returns per unit of effort, reduce uncertainty during the fishing season, and provide objective information for the design of management plans and quota allocation systems, both at national level and at PO level. In addition, the knowledge generated will make it possible to anticipate potential future changes in anchovy population dynamics and improve the fishing sector’s capacity to adapt.

Funding