Abstract In the present study, we evaluated the effects of two stocking densities (low - ALD, 3.81 kg m−3 vs. high - AHD, 7.26 kg m−3) on the growth, health, and flesh quality of rainbow trout (Oncorhynchus mykiss) and the yield and microbiological quality of lettuce (Lactuca sativa) produced in a low-tech aquaponic system compared to hydroponic cultivation (HYP). Nine experimental units (three replications per treatment) were utilised. A total of 123 rainbow trout (initial body weight: 142 ± 35 g) were randomly distributed in six 500-L tanks (3 per stocking density) and monitored during a 117 day trial period. The final weight (331 g on average), specific growth rate (0.73% d−1), feed conversion ratio (1.58), and mortality (3%) of the fish did not differ between stocking densities. The morphometric indices, slaughter results, and flesh quality were not affected. Similarly, the quantity of lettuce produced during two consecutive cycles was similar among treatments (2.4 kg m−2 on average). At harvest, microbial contamination (total viable count, E. coli, Enterobacteriaceae, Pseudomonas, mould, and yeasts) was similar in the fish skin and lettuce produced in aquaponic systems with different stocking densities, as well as in the lettuce produced in aquaponic and hydroponic systems. In conclusion, rainbow trout and lettuce productions were successful in the tested aquaponic system, whereas stocking density did not affect fish growth or flesh quality.

中文翻译：

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放养密度对低技术鱼菜共生系统养殖虹鳟鱼（Oncorhynchus mykiss）生长和肉质的影响

摘要 在本研究中，我们评估了两种放养密度（低 ALD，3.81 kg m-3 与高 AHD，7.26 kg m-3）对虹鳟鱼（Oncorhynchus mykiss) 以及与水培 (HYP) 相比，在低技术水培系统中生产的生菜 (Lactuca sativa) 的产量和微生物质量。使用了九个实验单元（每个处理三个重复）。总共 123 条虹鳟鱼（初始体重：142 ± 35 克）随机分布在 6 个 500 升水箱（每个放养密度 3 个）中，并在 117 天的试验期内进行监测。鱼的最终重量（平均 331 克）、比生长率（0.73% d-1）、饲料转化率（1.58）和死亡率（3%）在放养密度之间没有差异。形态指标、屠宰结果、肉质不受影响。同样，在两个连续周期中生产的生菜数量在处理之间相似（平均 2.4 kg m-2）。在收获时，不同放养密度的鱼菜系统中生产的鱼皮和生菜以及鱼菜系统中生产的生菜中的微生物污染（总活菌数、大肠杆菌、肠杆菌科、假单胞菌、霉菌和酵母菌）相似。水培系统。总之，虹鳟鱼和生菜在经过测试的鱼菜共生系统中是成功的，而放养密度不影响鱼的生长或肉质。肠杆菌科、假单胞菌、霉菌和酵母菌）在鱼皮和不同放养密度的鱼菜系统中生产的生菜中以及在鱼菜和水培系统中生产的生菜中相似。总之，虹鳟鱼和生菜在经过测试的鱼菜共生系统中是成功的，而放养密度不影响鱼的生长或肉质。肠杆菌科、假单胞菌、霉菌和酵母菌）在鱼皮和不同放养密度的鱼菜系统中生产的生菜中以及在鱼菜和水培系统中生产的生菜中相似。总之，虹鳟鱼和生菜在经过测试的鱼菜共生系统中是成功的，而放养密度不影响鱼的生长或肉质。