European eels Anguilla anguilla from freshwater lakes in Lithuania had slower growth rates and lower backcalculated total lengths (L T ) than those from lagoons and coastal waters, but no significant differences were found among fish with different migratory histories or between naturally recruited and stocked fish except a higher L T at age of stocked European eels at ages 5 to 8 years. The asymptotic L T ðL TN Þ did not differ among habitats or migratory histories, but the stocked eels in the lakes had smaller K (coefficient from the von Bertalanffy growth function) than did the both naturally recruited and stocked eels in the lagoon and coastal waters. The growth rate of European eels in Lithuania might be influenced mainly by different habitats rather than different migratory histories and stocking. The lower L T at age of naturally recruited fish at ages 5-8 years compared to stocked fish might result from the extra energy costs entailed in migration from the Atlantic and across the Baltic Sea.

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European eel Anguilla anguilla migratory behaviour during continental life is still unclear due to the multiplicity of aquatic environments colonised by the species. In the Camargue area (NW Mediterranean), eel colonisation of the Fumemorte canal, a freshwater habitat that communicates only with a vast brackish ecosystem (the Vaccarès lagoon), offers a rare opportunity to test for freshwater habitat residence during continental life. To this end, both laser ablation inductively coupled plasma mass spectrometry and electron probe micro-analysis were used to measure chronological variations of strontium concentrations (Sr:Ca) in the otoliths of 58 silver eels captured in the canal between 1997 and 2007. Comparing mean Sr:Ca ratios measured on otolith edges with the 2 analytical methods indicated that they provide comparable measurement accuracies. Linear discriminant analysis (LDA), based on the otolith Sr:Ca values corresponding to the initial entrance of the fish into the brackish ecosystem and their final capture in the freshwater canal, allowed successful discrimination of the 2 habitats and reconstruction of migratory history for all individuals. Six different migratory behaviours were identified. Eels that entered the freshwater canal did so either directly (67%) or after 1 to 2 yr spent in the lagoon (33%), with a subsequent majority of freshwater residents (55%) until their silvering. These results indicate the value of LDA for reconstructing habitat use during continental life using Sr:Ca ratios. They confirm the occurrence of freshwater residence during continental life in European eels, even in Mediterranean continental areas where brackish environments are predominant. This observed sedentary behaviour has implications for eel population management and conservation. Investigating Anguilla anguilla movements during continental life and its variation at both local and global scales is of paramount importance for the conservation of this endangered species (Bonhommeau et al. 2008, Belpaire et al. 2009), especially within the context of littoral habitat alteration due to anthropogenic activities and climate change. Because the abiotic and biotic conditions experienced by the eels within their continental habitats can induce strong differences in growth rate, age at maturity, sex ratio and lifetime reproductive success (Panfili & Ximenes 1994, Jessop et al. 2004, Walsh et al. 2004, Bevacqua et al. 2006, Daverat & Tomas 2006, Melia et al. 2006a, habitat loss during continental life can also threaten the maintenance of eel stocks in the future through a loss in reproductive success (Bonhommeau et al. 2008, Belpaire et al. 2009). In this regard, most of the investigations have focused on the continental habitats identified along the west European coasts (Daverat et al. 2005, Laffaille et al. 2005, Daverat & Tomas 2006, and nothing is known about the migratory behaviour of A. anguilla within its Mediterranean coastland habitats.In the Camargue area (NW Mediterranean coastland, southern France), the va...

Otolith Sr:Ca ratios from 32 of 34 European eel Anguilla anguilla collected from three freshwater sites in the River Asi, southern Turkey, indicated that they were resident in fresh water without apparent exposure to salt water since the elver stage. The Sr:Ca ratio criterion indicative of residence in fresh water was more than twice that of values from other European countries. Otolith Sr:Ca ratios of A. anguilla from fresh waters can vary among regions, possibly reflecting regional-specific water chemistry. Hence, the use of Sr:Ca ratios determined in one region to interpret results from a different region might lead to misclassification of migratory life-history types.

The age of Japanese eels (Anguilla japonica) is often estimated from otoliths, but this method has not been fully validated, particularly in tropical areas where the annulus in otolith is considered to be less distinct than in temperate areas. To validate the annuli in Japanese eel otoliths from southern Taiwan, knownage (2 year-old) cultured eels from an eel farm and wild eels from Kao-Ping River were collected. It was found that 26 out of 31 cultured eels (83.9%) showed two clear annuli and the remained 5 eels showed either one or three annuli. The mean (± SD) age of the cultured eels was 1.97±0.4 years. Meanwhile, a clear peak in the mean monthly marginal increment ratio of the otolith in wild yellow and silver eels occurred once a year during winter (November to March). The annual deposition of presumed annuli in otoliths of Japanese eel was validated and the age and growth rate estimation for Japanese eels in the tropical southern Taiwan is deemed feasible. The growth rate of cultured eels was significantly faster than that of wild eels, but it did not differ significantly between sexes for wild silver, yellow or cultured eels. The von Bertalanffy Growth Function parameters (K, L 1 and t 0 ) of the wild eels were estimated as 0.114±0.028 year −1 , 1178±171 mm and −0.8± 0.2 years, respectively.