ABSTRACT: Sea cage aquaculture can alter the spatial distribution of wild fish populations; however, little is known about the dietary habits of wild fish frequenting sea cages. We used wild juvenile cod Gadus morhua reared in the laboratory and fed either an aquafeed pellet or marine-based diet to determine trophic discrimination factors (TDFs) of stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope values in white muscle tissue and baseline liver proportions of vegetable-oil based (VOB) fatty acids. We then used δ¹³C and δ¹⁵N and proportions of VOB fatty acids to investigate the dietary habits of wild cage-associated juvenile and adult Atlantic cod and adult Atlantic redfish Sebastes fasciatus. Cod and redfish were collected in the immediate area of sea cages and reference areas of no aquaculture production. Juvenile cod captured around sea cages had both elevated δ¹³C and δ¹⁵N values and proportions of VOB fatty acids, and isotopic fractionation comparable to laboratory cod fed an aquafeed diet. However, differences in δ¹³C and δ¹⁵N and proportions of VOB fatty acids between cage-associated and reference site adult cod and redfish were predominately absent. Results suggest that sea cages may provide an energetic subsidy to juvenile cod but perhaps not at the level to sustain adult cod or redfish. Therefore, the lack of differences suggests that both adult groups may be using cage sites opportunistically and only for short duration, as isotopic values and fatty acid proportions were not consistent with waste feed consumption despite individuals being collected in close proximity to sea cages.

中文翻译：

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海水网箱养殖可以为加拿大纽芬兰南部沿海海湾的野生鳕鱼幼鱼提供有力的补贴

摘要：海水网箱养殖可以改变野生鱼类种群的空间分布；然而，人们对经常出现在海网箱中的野生鱼的饮食习惯知之甚少。我们用野生少年鳕鳕鳕在实验室饲养并送入任一种水产饲料颗粒或基于海洋的饮食，以确定稳定的碳（δ的营养判别因子（TDF的）¹³ C）和氮（δ ¹⁵ N）同位素值在白肌植物油基 (VOB) 脂肪酸的组织和基线肝脏比例。然后，我们使用 δ ¹³ C 和 δ ¹⁵ N 以及 VOB 脂肪酸的比例来研究野生网箱相关的大西洋鳕鱼幼鱼和成年鳕鱼以及大西洋红鱼Sebastes fasciatus的饮食习惯. 鳕鱼和红鱼是在近海网箱区域和没有水产养殖生产的参考区域收集的。在海网箱周围捕获的幼鳕具有升高的 δ ¹³ C 和 δ ¹⁵ N 值和 VOB 脂肪酸比例，以及与以水产饲料喂养的实验室鳕鱼相当的同位素分馏。然而，δ ¹³ C 和δ ^{15 的}差异N 和网箱相关和参考地点成年鳕鱼和红鱼之间的 VOB 脂肪酸比例主要不存在。结果表明，海网箱可以为幼年鳕鱼提供能量补贴，但可能达不到维持成年鳕鱼或红鱼的水平。因此，缺乏差异表明，尽管个体是在靠近海网箱的地方收集的，但由于同位素值和脂肪酸比例与废物饲料消耗量不一致，因此两个成年群体可能会机会性地使用网箱地点，并且仅持续很短的时间。