Migratory history and habitat-use strategy of the European eel Anguilla anguilla in Italian waters as indicated by otolith Sr/Ca ratios
Date Issued
2011
Date
2011
Author(s)
Li, Dai-Yu
Abstract
To understand the migratory behavior and habitat use of the European eel Anguilla anguilla in habitats with different salinities, a total of 180 eels were collected from Tevere River (TR, annual mean salinity = 0.0 psu), Lesina Lagoon (LL, annual mean salinity = 16.0 ± 11.4 psu), and Caprolace Lagoon (CL, annual mean salinity = 38.1 ± 4.5 psu), Central and Southern Italy. All of the 180 eels were conducted for biological estimation (e.g. age, total length, and weight) and 56 of them were randomly selected for otolith Sr/Ca ratios analysis. The analyzed path was separately from primordium to otolith edge and at the otolith edge by Electron Probe Micro-analyzer (EPMA).
The mean ( ± SD) Sr/Ca ratios at otolith edge are 2.8 ± 0.8×10-3, 7.8 ± 1.9×10-3, and 10.3 ± 1.7 ×10-3 for eels respectively collected from freshwater TR, brackish water LL, and seawater CL, significantly different among each other ( p < 0.01 ). The positive correlation between otolith Sr/Ca ratio and the ambient salinity (R2 = 0.63, p < 0.01) confirmed that Sr/Ca ratio is reliable in studying migratory history of the eel. Furthermore, the negative correlation between otolith Sr/Ca ratio and water temperature was only found in eels from TR, but not for eels from LL or CL, indicating that the effect of water temperature on otolith Sr/Ca ratio might be influenced by salinity.
Based on the temporal change in otolith Sr/Ca ratios, the migratory type and habitat use of 56 eels in the above three habitats were categorized into freshwater type (FW), brackish water type (BW), and seawater type (SW), as well as inter-habitat shifter type (IHS; eels migrated between habitats). The proportion of IHS is higher in the oligotrophic and highly saline CL (95%), followed by fresh TR (40%), and is lower in the eutrophic and brackish LL (35%). This suggests that eels preferred to settle in habitats with rich nutrient and lower salinity during the growth phase. To sum up, European eels in the Italian waters of Mediterranean area display high diversity of habitat use and their habitat use is facultative catadromy. In addition, our results are consistent with the hypothesis advanced in the previous studies that migratory behavior of the eel is mainly affected by environmental factors.
Subjects
European eel Anguilla anguilla
migratory history
habitat use
otolith Sr/Ca ratio
Italian waters
Type
thesis
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