bay Biscay anchovies smaller

The AZTI technology centre has unveiled scientific evidence showing anchovies inhabiting the Bay of Biscay are smaller than 30 years ago. Photo: AZTI

Shrinking Anchovies in the Bay of Biscay: AZTI Study Reveals Size Reduction Over 30 Years

The AZTI technology centre, specialising in marine and food research, has unveiled scientific evidence pointing to a decrease in the size of anchovies inhabiting the Bay of Biscay.

A comprehensive study spanning three decades, from 1990 to 2021, highlights a noticeable reduction in the average size and weight of adult European anchovy (Engraulis encrasicolus L.). The findings, shedding light on the complex interplay of environmental factors, have been published in the esteemed journal Global Change Biology.

Fernando Taboada, one of the primary authors of the AZTI study, underscores, “The decrease in weight is slightly more pronounced than in total length, with reduction rates that have accelerated by up to 25% per decade over the last twenty years.”

While the changes are partially attributed to ocean warming, researchers participating in the study emphasise a multifaceted interaction of environmental variables, ruling out significant influence from fishing pressure.

Guillem Chust, another author of the study, notes, “We found that the more abundant the anchovy, the smaller the specimens, but this relationship with population density is less clear at later stages, where temperature has been shown to be the main cause of the decrease in size.”

bay of biscay anchovies

Image: AZTI

The Temperature-Size Rule (TSR) comes into play, with the experts explaining that juvenile fish in warmer waters tend to grow faster. However, these warmer conditions impede subsequent development, resulting in a smaller adult body size. The study confirms two ecogeographical hypotheses, indicating that fish size tends to be larger in colder water when comparing different closely related fish species. Additionally, individuals from various European anchovy populations generally exhibit larger sizes in colder seas.

AZTI underscores the need for caution, acknowledging the study’s reliance on observations and inherent limitations. Nevertheless, the accumulating evidence suggests that the reduction in anchovy size could serve as an indicator of the ecosystem’s response to climate changes in the Bay of Biscay.

The study received support from European projects LIFE Urban Klima 2050 and SEAWISE, along with backing from the Department of Agriculture, Fisheries, and Food Policy of the Basque Government through the FEMPA projects. The General Secretariat of Fisheries of the Ministry of Agriculture, Fisheries, and Food of the Spanish Government also contributed through the Next Generation funds of the Recovery Plan.

 

Source: Press Release

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