Hard times for catadromous fish: the case of the European eel (Anguilla anguilla, L. 1758)

Abstract

Catadromous fish species are very important organisms for their ecological, economical, and cultural value. For its complex life species catadromous fish result in worldwide decline since the beginning of the 20th century. Among the most iconic catadromous species, the European eel Anguilla anguilla L. 1758 has aroused considerable interest since very ancient times. Because, to date, many aspects of their life cycle remain relatively unknown, to implement our knowledge about the main natural and anthropogenic threats to its survivorship and identify possible solutions to preserve it, in this narrative review, we present the state of the knowledge about the life cycle, habitat occupancy, recruitment, and migration patterns of the European eel and about the major threats most likely have contributed to the decline of eels’ populations.

Exploring European Eel Anguilla anguilla (L.) Habitat Differences Using Otolith Analysis in Central-Western Mediterranean Rivers and Coastal Lagoons from Sardinia

“…Eels with rounder otoliths were found in freshwater riverine habitats. These environments generally tend to be less susceptible to variations in salinity or temperature and depth than brackish estuaries or lagoons [98]. However, it remains unknown how environmental abiotic variables may act together, influencing or limiting the growth of the species [29].…”

Changes in Dendritic Spine Morphology and Density of Granule Cells in the Olfactory Bulb of Anguilla anguilla (L., 1758): A Possible Way to Understand Orientation and Migratory Behavior

“…Our findings showed great synaptic development activity in migratory phases of eels, which regresses in the trophic phase, but must necessarily be recreated by tracing the migratory memory of the routes previously travelled in the juvenile phases. If olfaction plays a role in the orientation and migratory behaviour throughout the complex and long life cycle of A. anguilla and if eels possess a memory, all these processes could be influenced by changes in the olfactory stimuli under several internal and external conditions (e.g., adaptation to different aquatic environments; sexual development phases, growing or fasting phases, climate changes, ocean alterations) [ 108 , 109 , 110 ], making it difficult or impossible to cover wide reproductive migratory routes and constituting a cofactor that contributes to threaten this critically endangered species (CR) [ 111 ].…”

Evaluation of Chemical Elements, Lipid Profiles, Nutritional Indices and Health Risk Assessment of European Eel (Anguilla anguilla L.)

“…Due to their complex life cycle, catadromous fish species are subject to the cumulative impact of many anthropogenic threats that have led to global decline since the early 20th century [5]. Important factors determining the quality status of the eel are environmental parameters, such as the area of the body of water, depth, connections with the sea, and the size of the river basin [23], while the aspects that explain the storage and elimination of contaminants from the body of these fish are habitat, physiological factors, lipid content, geographic origin, and nutritional behavior [24].…”

“…The European eel (Anguilla anguilla L.) is a species native to the waters of Western Europe [1]. It is a predatory fish [2] and is classified as a catadromous species [2][3][4][5], with reproduction taking place in the Sargasso Sea (Atlantic Ocean). The discovery of small (<10 mm) larvae in the Sargasso Sea by biologist Johannes Schmidt over 100 years ago confirmed the location of the spawning grounds for this species [1].…”