The high frequency of regenerated scales (degree of scale regeneration, SRD) in reared fish has been used in the past for the identification of aquaculture escapees in the wild stocks. In the present study, we examined the evolution of the SRD in Gilthead seabream (Sparus aurata) throughout the entire rearing process (hatchery and on-growing, 2.0–21.9 cm standard length, SL). For this purpose, nine fish samples were randomly taken from different populations and farm sites, at different time points (58–393 days post-hatching, dph). Results demonstrated that scales are lost continuously, from the onset of squamation (11.2 ± 5.7% mean SRD, 58 dph, 2.0 cm SL) to the end of the on-growing period (98.7 ± 3%–99.8 ± 0.9% mean SRD, 314–393 dph, 21.7–21.9 cm SL). At the transition between the hatchery period and the on-growing in sea cages, fish presented a wide distribution of SRD, ranging from 40% to 92% (122 dph, 5.1 cm SL). Despite the different sample origins, a uniform relationship between SRD and SL was observed, with a clear inflection point (2.7 cm SL) and two periods with different rates of scale loss. Our findings are discussed in relation to the use of regenerated scales for the identification of aquaculture escapees in wild stocks and the need to revisit the different suggested critical SRD thresholds.

中文翻译：

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养殖金头鲷的鳞片再生：重新审视鳞片在识别水产养殖逃逸者中的应用

养殖鱼中再生鳞片的高频率（鳞片再生度，SRD）过去曾被用于识别野生种群中的水产养殖逃逸者。在本研究中，我们研究了金头鲷（Sparus aurata) 贯穿整个饲养过程（孵化和生长，2.0-21.9 厘米标准长度，SL）。为此，在不同时间点（孵化后 58-393 天，dph）从不同种群和养殖场随机抽取了 9 个鱼样本。结果表明，鳞片不断丢失，从鳞片开始（11.2 ± 5.7% 平均 SRD，58 dph，2.0 cm SL）到生长期结束（98.7 ± 3%–99.8 ± 0.9% 平均 SRD， 314–393 dph，21.7–21.9 cm SL）。在孵化期和海网箱生长之间的过渡期，鱼呈现出广泛的 SRD 分布，范围从 40% 到 92%（122 dph，5.1 cm SL）。尽管样品来源不同，但观察到 SRD 和 SL 之间存在一致的关系，具有明显的拐点 (2.7 cm SL) 和两个具有不同比例损失率的时期。