Sagittal otoliths are calcareous structures in the inner ear of fishes involved in hearing and balance. They are usually composed of aragonite; however, aragonite can be replaced by vaterite, a deformity which is more common in hatchery-reared than in wild fish. Vaterite growth may impair hearing and balance and affect important fitness-related behaviours such as predator avoidance. Captive rearing techniques that prevent hearing loss may have the potential to improve fish welfare and the success of restocking programmes. The aim of this study was to test the effect of structural tank enrichment on vaterite development in the otoliths of hatchery-reared juvenile Atlantic salmon Salmo salar, and to assess the effects of vaterite on immediate predation mortality and long-term survival after release into the wild. Fry were reared in a structurally enriched or in a conventional rearing environment and given otolith marks using alizarin during the egg stage to distinguish between the treatment groups. Otoliths were scrutinised for the presence and coverage of vaterite at 6, 13, and 16 weeks after start feeding, and the growth traits were measured for enriched and control fry when housed in tanks. In a subsequent field experiment, juveniles were released in the Rasdalen river (western Norway), and otoliths of enriched reared and control reared fry were scrutinised from samples collected immediately prior to release, from predator (trout Salmo trutta) stomachs 48 h after release and from recaptures from the river 2–3 months after release. Vaterite otoliths occurred as early as 6 weeks after start feeding in hatchery-reared S. salar. Vaterite occurrence and coverage increased with fish length. Enriched rearing had no direct effect on vaterite formation, but enriched reared fry grew slower than control fry. After release into the wild, fewer salmon fry with vaterite otoliths had been eaten by predators, and a higher proportion of fry with vaterite otoliths than those lacking vaterite were recaptured in the river 2–3 months after release. Contrary to expectations, this suggests that vaterite does not increase predation mortality nor reduce survival rates in the wild during the early life stages.

矢状耳石是鱼类内耳中的钙质结构，与听力和平衡有关。它们通常由文石组成；然而，文石可以被球霰石取代，这种畸形在孵化场养殖中比在野生鱼中更为常见。球霰石的生长可能会损害听力和平衡，并影响与健康相关的重要行为，例如躲避捕食者。防止听力损失的圈养养殖技术可能有可能改善鱼类福利和重新放养计划的成功。本研究的目的是测试结构罐富集对孵化场养殖的大西洋鲑幼鱼耳石中球霰石发育的影响鲑鱼，并评估球霰石对释放到野外后的即时捕食死亡率和长期存活率的影响。鱼苗在结构丰富或传统的饲养环境中饲养，并在卵阶段使用茜素给予耳石标记以区分处理组。在开始喂食后 6、13 和 16 周，仔细检查耳石的球霰石的存在和覆盖情况，并测量生长特性，以获取在水箱中饲养的富集鱼苗和对照鱼苗。在随后的田间试验中，幼鱼被释放到 Rasdalen 河（挪威西部），从捕食者（鳟鱼三文鱼) 释放后 48 小时胃和释放后 2-3 个月从河中重新捕获。球霰石耳石最早在孵化场饲养的 6 周后出现盐沼. 球霰石的出现和覆盖率随着鱼的长度而增加。强化饲养对球霰石的形成没有直接影响，但强化饲养的鱼苗比对照鱼苗生长慢。释放到野外后，捕食者吃掉的带有球霰石耳石的鲑鱼鱼苗较少，而在释放后 2-3 个月，在河中重新捕获的带有球霰石耳石的鱼苗的比例高于没有球霰石的鱼苗。与预期相反，这表明球霰石在生命早期阶段不会增加捕食死亡率，也不会降低野外生存率。