Differences in organochlorine accumulation accompanying life history in the catadromous eel Anguilla japonica and the marine eel Conger myriaster

Abstract

In order to examine the ecological risk for organic pollutants in diadromous fish migrating between sea and freshwater, organochlorine compounds (OCs) were determined in the catadromous eel Anguilla japonica having marine, estuarine and freshwater residence life histories. The eels were collected in Japanese coastal areas. We also compared the OCs accumulation with the marine eel Conger myriaster, which has a similar life history as A. japonica in the marine environment. The ontogenic changes in the otolith strontium (Sr) and calcium (Ca) concentrations were examined along the life history transect to discriminate the migration type. There were generally three different patterns, which were categorized as 'marine residence' (spent most of their life in the sea and did not enter freshwater), 'estuarine residence' (inhabited estuaries or switched between different habitats), and 'freshwater residence' (entered and remained in freshwater river habitats after arrival in the estuary) according to the otolith Sr:Ca ratio. There were generally no correlations between OCs such as Dichlorodiphenyltrichloroethanes (DDTs), Hexachlorobenzene (HCB), Hexachlorocyclohexanes (HCHs) and Chlordanes (CHLs) accumulation and each biological characteristic such as TL, BW and age in A. japonica. A positive correlation between the lipid content and concentrations of OCs were found. Additionally, the concentrations of HCB, ∑HCHs, ∑CHLs and ∑DDTs in A. japonica were significantly higher than those of C. myriaster, associating with the higher lipid contents (14% on average) in the former than the latter eels (9% on average). A negative linear relationship was found between the otolith Sr:Ca ratios and concentration of each OCs in A. japonica. The ecological risk of OCs increase as the freshwater residence period in the eel becomes longer. It is clear that migratory histories and lipid contents directly affected OCs accumulation in the anguillid eels.

A question of origin: dioxin-like PCBs and their relevance in stock management of European eels

“…Evidently the growth phase in continental freshwater and coastal systems is the decisive phase for the uptake of contaminants during the eel's life cycle. These findings are in agreement with results from similar studies (Tapie et al 2011;Arai and Takeda 2012;Byer et al 2013;Sühring et al 2013;Blanchet-Letrouvé et al 2014). Congener patterns of yellow and silver eels from the same habitat in this study showed no significant differences.…”

“…In a Portuguese study by Guimaráes et al (2009), results indicated that yellow eels originating from stronger polluted habitats showed higher adverse physiological effects determinant for their survival and performance than yellow eels originating from a less polluted habitat. In another study on Japanese eels (Anguilla japonica) by Arai and Takeda (2012) from Japan, the authors state that the ecological risks of organochlorine compounds (OC) increase as the freshwater residence period in eel become longer. Therefore individual lipid contents and migratory histories directly affect the accumulation of those OCs in anguillid eels.…”

Important questions to progress science and sustainable management of anguillid eels

“…Only in areas with very low environmental impacts (such as Norway, Holmqvist et al, 2006; and Scotland, Oliver et al, 2015) can eels be expected to exhibit low pollutant burdens (Bourillon et al, 2020). Despite the extensive literature on A. rostrata and A. anguilla , there are still only a few studies on the chemical contamination of other species of eels (Arai et al, 2012; Arai & Takeda, 2012; Calvi et al, 2006; Holmqvist et al, 2006; Khalil et al, 2017; Le et al, 2010; Ohji et al, 2006; Redmayne et al, 2000; Yamamuro et al, 2019).…”