Studies on the Improvement of Flesh Quality and Integumentary Color of Cultured Striped Jack Pseudocaranx dentex

为了提高培养的条纹凤尾莲的皮肤色素沉着、口感和质地，进行了多项试验。第一次试验结果表明，饲喂螺旋藻是非常有效的。添加10%水平的螺旋藻可显著降低背肌、肝脏和内脏的脂质水平，改善腹肌的色泽和质地，改善腹肌的口感，且显著性达到5%。喂食含有5%或10%藻类的饲料的鱼的皮肤颜色在背部变成彩虹色的绿灰色，在侧线附近有一条典型的黄色带，而喂食不含藻类或生沙丁鱼碎的对照饲料的鱼则呈现深灰色。黄质、叶黄素和玉米黄质占背被类胡萝卜素含量的95%以上（0.28 ~ 1.5 mg/100g组织），添加螺旋藻后均有所增加。使用新开发的软干颗粒也证实了这些结果，该颗粒具有高适口性和可接受性。在最后的实验中，将螺旋藻分离成丙酮、甲醇、水和乙醚可溶性部分和极性脂质部分，分别投喂鱼，以鉴定藻类中的有效成分。结果表明，甲醇溶脂或极性脂质组分中的γ -亚麻酸（GLA）能有效改善肉质，降低肌肉和肝脏中的脂质含量。因此，在实践中，建议在水产饲料中每100粒干颗粒添加约100毫克GLA。

Various trials were conducted in order to improve the quality of cultured striped jack, Pseudocaranx dentex, in terms of pigmentation of skin, taste and texture.The results of the first experiment showed that feeding of Spirulina was very effective for this purpose. The supplementation of Spirulina at 10% level depressed the lipid levels of the dorsal muscle, liver and viscera, and improved not only the integumentary color and texture, but also the taste ofventral muscle at 5% significance. The skin color of fish fed diets containing the alga at 5% or 10% became iridescent greenish gray at the back with a characteristic yellow band near the lateral line, whereas those on the control diet without the alga or minced raw sardine exhibited dark gray. The three yellow components - tunaxanthin, lutein and zeaxanthin - constituted more than 95% of the carotenoids (0.28-1.5 mg/100g tissue) in the dorsal integuments and all of them increased on supplementation of Spirulina. These results were also confirmed using a newly developed soft-dry pellet which high palatability and acceptability to striped jack.In the final experiment Spirulina was separated into the acetone, methanol, water and ethyl ether soluble fractions and polar lipid fraction, whereupon each was fed to fish to identify the effective component in the alga. The results have shown that gamma linolenic acid (GLA) in the methanol soluble or polar lipid fraction was effective for improvement of flesh quality, reducing the lipid content in muscle and liver. Thus, in practice, it is recommended that aquatic diets could be fortified with about 100 mg GLA per 100 dry pellet.