DOI: 10.5281/zenodo.10604054
title: European eel (Anguilla anguilla) time series

description: This dataset was managed for the aims of the project ECOSISTER (Ecosystem for Sustainable Transition in Emilia-Romagna), WP3 of Spoke 5 and provides the long-term records (from 1781 to 2013) of European eel (Anguilla anguilla L.) production in the Comacchio Lagoon (Italy). 

he European eel spends most of its life as a yellow eel in freshwater, brackish, and coastal environments. Upon reaching sexual maturity, it undergoes metamorphosis into a silver eel and migrates back to the Sargasso Sea to spawn and die. The silver eels of Comacchio Lagoon were always caught in the lavorieri with approximately 100% efficiency and official estimates of the total biomass were being made every year for more than 200 years. The Regional Park of the Po Delta and the Management Agency for the Parks and Biodiversity of Delta del Po were founded in 1988 and took over the infrastructures, official documents and records of the previous company managing the fishery. These fishery historical records were organized and combined with new data to provide 1) Annual records of total weight of silver eels captured and 2) Annual records that present the variation of fishing area coverage, from 1781 to 2013.

The dataset is provided in two formats:

- Microsoft Excel XLSX file, including 3 sheets (Dataset, Fields and units, Taxonomy)

- CSV files (UTF-8), 3 files corresponding to the 3 sheets of the Excel file

 

The dataset includes 233 records with total weight of silver eels captured in the Comacchio lagoon, their annual density, and the fishing area coverage. The fields are described in Table 1.

All the dataset fields are described in the Excel sheet/CSV file “Fields and units”, while the taxonomic related information for Anguilla anguilla is provided in the Excel sheet/CSV file “Taxonomy”. Information extracted from the World Register of Marine Species (WoRMS; https://marinespecies.org/) is provided here (see details in Table 2).

Table 1. Fields in the dataset (NA=not available).








Field



Darwin Core term



Unit



Precision



Note





decimalLatitude



decimalLatitude



decimal degrees



± 0.00001



WGS84 (EPSG: 4326) - WAAS/EGNOS enabled GPS position





decimalLongitude



decimalLongitude



decimal degrees



± 0.00001



WGS84 (EPSG: 4326) - WAAS/EGNOS enabled GPS position





dateIdentified



dateIdentified



YYYY



NA 



The year on which the data refere





Mass of silver eels (t)



organismQuantity



tons of eel



NA



Total silver eel catches





Abundance (kg/ha)



organismQuantity



kilograms of eels per hectare



NA



Abundance of silver eels





Fishing area (ha)



sampleSizeUnit



hectares



NA 



Eel fishing area






 

Table 2. Provided taxonomic information.








Taxon



the name used in the dataset







ScientificName_accepted



the name accepted according WoRMS





AphiaID



Unique identifier in WoRMS





Kingdom



Taxonomic level





Phylum



Taxonomic level





Class



Taxonomic level





Order



Taxonomic level





Family



Taxonomic level





Genus



Taxonomic level





Species



Taxonomic level






This dataset permitted the analysis of local and global factors responsible for the collapse of the European eel through the publication of Aschonitis, V., Castaldelli, G., Lanzoni, M., Rossi, R., Kennedy, C., and Fano, E. A. (2017) Long-term records (1781–2013) of European eel (Anguilla anguilla L.) production in the Comacchio Lagoon (Italy): evaluation of local and global factors as causes of the population collapse. Aquatic Conserv: Mar. Freshw. Ecosyst., 27: 502–520. doi: 10.1002/aqc.2701.

The data were used to illustrate the population decline of eel in the most important eel fishery in the Mediterranean area, the Valli di Comacchio, followed by a detailed discussion of the potential role of major local factors (habitat loss, changes in local environmental conditions) and global factors (aquaculture and fisheries, climate change, habitat loss, pollution and parasitism) that may be responsible for the population decline of this important eel species.

The Valli di Comacchio which is also one of the most important areas for conservation. In fact, the Comacchio lagoon is included in the 2000 Nature network as IT4060002 “Valli di Comacchio” site and also in the Ramsar convention as important wetlands.

Furthermore, the Anguilla anguilla species is a critically endangered species, according to the IUCN, and is included in the 92/43/EEC Directive, therefore, information on its current population status and dynamics are necessary and can support the development of future conservation plans for eel species. It should also be pointed out that there is no long and detailed historical series on eel fishery, such as the one presented here, which is of quantitative value in describing the evolution of the eel population and due to the constant environmental condition of the area, also provides information on the amount of eel recruitment.