###### Abstract  
The edible safety of eugenol-treated fish is one of the concerns limiting the anesthetic applied in the aquaculture industry. The depletion of eugenol was investigated at different water temperatures under the simulated settings of sea bass handling and transport. Sea bass was exposed to eugenol at a concentration of 60 mg/L for 3 min, then immediately transferred to clean water to be purged for 24 h and sampled at different time intervals. The left fish were re-exposed to eugenol in a repeat of the first exposure, purged for 48 h in clean water, and sampled for eugenol detection. Under the simulated settings, the sea bass could accumulate more eugenol residue in fillet when exposed to water at a temperature of 20 \({}^{\circ}\)C than that at 13 \({}^{\circ}\)C. However, eugenol could be depleted much faster when the sea basses were exposed to the higher water temperature. The half-lives of eugenol in sea bass were 0.28 h and 0.29 h for the first and second purging stage at a water temperature of 20 \({}^{\circ}\)C, while at 13 \({}^{\circ}\)C, the half-lives were 2 and 4.5 h, respectively. Therefore, increasing the water temperature may be an effective way to accelerate eugenol depletion in fish fillet and reduce exposure risk for the consumer. fish anesthetic; sea bass; eugenol; depletion; water temperature +
Footnote †: journal: Applied Sciences  
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is approved as a food fish anesthetic in Japan, the Maximum Residue Limit (MRL) in filler is set at 0.05 mg/kg and the withdrawal time is set at 7 days for fish and 10 days for crustaceans, respectively [16]. The WHO/FAO Joint Expert Committee on Food and Additives (JECFA) has proposed an acceptable daily intake (ADI) for eugenol, ranging from 0 to 2.5 mg/kg b.w. [17]. The daily intake of eugenol below the upper limit of the ADI value would not cause an appreciable health risk. This also means that less exposure to the anesthetic would lead to a higher safety margin in human health risk. Therefore, finding a way to reduce the residual amount of eugenol in edible tissues would not only improve the edible safety of eugenol-treated fish, but also benefit the aquaculture industry. Live fish can remove the residual eugenol in their tissues when purged in clean water. However, the ability to remove the anesthetic by fish is greatly affected by many factors, such as species, dosage, fish size, administration method, and water temperature [18]. As shown in previous reports, the half-life of eugenol in plasma was 12.14 h in rainbow trout in water at 4 \({}^{\circ}\)C, 0.3 h in Japanese founder in water at 24 \({}^{\circ}\)C, 19.97 h in grass carp in water at 25 \({}^{\circ}\)C, and 21.6 h in mandarin in water at 25 \({}^{\circ}\)C water, respectively [19; 20; 21; 22]. In the fillet tissue, the half-life was 26.25 min in rainbow trout [23], 10.27 h in grass carp and 5.1 h in mandarin. It indicated that the influencing factors were very complicated. Therefore, in live fish handling and transport, to ascertain and fully utilize the key influencing factors, it is very important to reduce the residue of eugenol in edible fish tissues in order to minimize the exposure risk of consumers. Sea bass is one of the most productive seawater species in China, as well as one of the species with the highest detection frequency of eugenol in the fish market [24]. This indicates that eugenol has been used in the handling and transport of sea bass, although the anesthetic has not been approved in the Chinese aquaculture industry. As investigated, from pond to market, sea basses were anesthetized for the first time in the culture ponds before being captured, and then transported to the market for 14-36 h; the second anesthetization was carried out on the transport vehicles before the sea basses were unloaded in the market, and then, the live individuals were temporarily held in a water tank for sale.