基于计算机视觉的大菱鲆对背景色选择习性研究

为了探讨大菱鲆幼鱼对于不同背景色的选择习性,该文首先通过9格颜色试验发现大菱鲆幼鱼偏好淡紫色,而出现在黑色和红色背景累积频率较低;同时通过计算机视觉分析发现,幼鱼在黑色和红色背景下体表明度变化速率远比在紫色和粉色背景下剧烈,证明了黑色和红色背景对幼鱼胁迫更大,其需要调动更多激素来调整生理响应,以改变体色适应新的背景环境。因此建议养殖池的颜色尽量采用浅色,不要使用黑色等深色作为养殖背景颜色,研究结果可为养殖系统设计和生产管理提供参考依据。     

胆汁酸对大菱鲆幼鱼生长、脂肪代谢酶及血清生化的影响

在基础饲料中分别添加0、0.03%、0.06%、0.09%及0.12%的胆汁酸,配制5组等氮等能的实验饲料(D1、D2、D3、D4、D5),投喂体质量为26.5 g的大菱鲆(Scophthalmus maximus)幼鱼56 d,研究胆汁酸对其生长、体组成、脂肪代谢酶活力及血清生化的影响。结果显示:(1)实验鱼的增重率、特定生长率、蛋白质效率及脂肪效率呈先升后平稳的趋势,均在D3组达到最高值。(2)胆汁酸显著降低了全鱼粗脂肪及粗灰分含量,提高了粗蛋白含量(P0.05);降低了肌肉粗脂肪含量,提高了粗蛋白及粗灰分含量(P0.05)。(3)脂肪酶及脂蛋白脂酶活力呈先升后平稳的趋势;肝脂酶活力显著升高(P0.05)。(4)胆汁酸降低了血清谷丙转氨酶及谷草转氨酶活力,提高了碱性磷酸酶活力(P0.05);总蛋白及白蛋白的含量随胆汁酸含量的增加而升高(P0.05);甘油三酯、总胆固醇及高低密度脂蛋白胆固醇含量随胆汁酸含量的升高而下降(P0.05)。(5)鳗弧菌感染48 h后,D3、D4及D5组的累积死亡率显著低于D1组。以增重率为评价指标,经折线回归分析,体质量26.5 g的大菱鲆幼鱼饲料中胆汁酸的适宜添加量为0.09%。     

Production and Physicochemical Characterization of Gelatin and Collagen Hydrolysates from Turbot Skin Waste Generated by Aquaculture Activities

Rising trends in fish filleting are increasing the amount of processing by-products, such as skins of turbot, a flatfish of high commercial value. In line with circular economy principles, we propose the valorization of turbot skins through a two-step process: initial gelatin extraction described for the first time in turbot, followed by hydrolysis of the remaining solids to produce collagen hydrolysates. We assayed several methods for gelatin extraction, finding differences in gelatin properties depending on chemical treatment and temperature. Of all methods, the application of NaOH, sulfuric, and citric acids at 22 °C results in the highest gel strength (177 g), storage and loss moduli, and gel stability. We found no relation between mechanical properties and content of pyrrolidine amino acids, but the best performing gelatin displays higher structural integrity, with less than 30% of the material below 100 kDa. Collagen hydrolysis was more efficient with papain than alcalase, leading to a greater reduction in Mw of the hydrolysates, which contain a higher proportion of essential amino acids than gelatin and show high in vitro anti-hypertensive activity. These results highlight the suitability of turbot skin by-products as a source of gelatin and the potential of collagen hydrolysates as a functional food and feed ingredient.     

利用数码技术测定鲆鲽类体表面积的方法

提出一种快速、准确测定鲆鲽类体表面积的新方法,利用数码相机拍照获取带有标准坐标纸背景的鲆鲽类鱼体数码图像,采用图像处理软件Photosllop CS2和Adobe Acrobat Professional分别获得单位背景面积和鱼体图像的像素数,通过两者的比例计算出体表面积.30尾大菱鲆(Scophthalmus maximus)体表面积的实测表明,与传统计数方格面积法的测量结果相比,Photoshop法相对误差为-4.40%～3.08%,Acrobat法相对误差为-1.83%～1.30%.统计分析显示,2种图像处理软件所测数据与传统方法测量值间差异都不显著,测量1尾大菱鲆体表面积,传统方法约耗时15 min,Plaotoshop和Acrobat法分别只需3 min和1.5 min.新方法可以迅速和准确地测定鲆鲽类体表面积,便于鲆鲽类养殖生产中对养殖密度进行有效管理.     

不同培养液对大菱鲆致病性纤毛虫——贪食迈阿密虫种群增长及复壮毒力的影响

从山东烟台地区某大菱鲆养殖场的患病大菱鲆体内分离出致病性纤毛虫——贪食迈阿密虫,筛选了4种盾纤毛虫常用体外培养液[大肠杆菌培养液(DH)、牛肉浸膏培养液(BEV)、米粒培养液(RV)、改良L-15培养液(L-15)],研究了不同培养基对纤毛虫种群增长及复壮毒力的影响.试验结果显示:在BEV和L-15两种培养液中,贪食迈...     

鲜活大菱鲆溯源标识固定工艺研究及参数优化

为获取鲜活大菱鲆(Scophthalmus maximus)溯源标识固定工艺,分别采用细耳标扣、T型扣与套环扣进行鱼体固定试验,对比各组的钉扣固定速率与钉扣有效固定率,评价不同钉扣固定后鱼体状态指标,选出最合适的钉扣。在此基础上,对比鱼体不同部位鳍体的固定效果,并对钉扣固定位置范围参数进行优化试验。结果表明,采用T型扣在大菱鲆背鳍部位,背鳍顶端以下5 mm至背鳍根部范围内进行标识固定较为适宜。此时,钉扣固定速率可达29.67尾/min,暂养5 d后的钉扣有效固定率达100%,且各项鱼体状态指标仍保持高水平。本研究的推广应用可为水产品产地溯源以及消费者对产品信息查询提供技术支撑。     

Fat content in turbot feed: influence on feed intake, growth and body composition

The influences of dietary fat concentration on growth and energy deposition were studied in two replicated groups of turbot, Scophthalmus maximus (L.). Individually tagged turbot (202.3 g) held at 15.6 °C were offered dry pellets in excess. These contained either high-fat (25.4%) or low-fat (16.6%) concentration and identical protein (43.2%). After 3 months, feed treatments were crossed in two replicates, and the remaining fish were offered a mix of feeds for a further 2 months. Fish were sacrificed for analysis of body composition at the start of the experiment, at the time of feed treatment changes and when the experiment was terminated. There were no significant differences in energy intake, specific growth rate or weight between treatments at any time during the experiment. At the time of the feed treatment change fish offered high-fat feed had a significantly higher relative body fat (8.2 vs. 6.3% w/w) and lower body water (71.2 vs. 73%), but there were no differences in protein or ash content. By the end of the experiment, differences in body composition had diminished. The results indicate that fat content in the turbot may be manipulated by changing the dietary fat content, apparently without major influences on weight gain.     

Biochemical and histochemical activities of tyrosinase in the skins of normal and albino turbot scophthalmus maximus

Albinism occurr frequently in hatchery-reared turbot, particularly in China. To elucidatethe mechanism of albinism, we comparedthe biochemical and histochemical activity of tyrosinase inthe skins of normal and albino turbot using substrate L-3,4-dihydroxyphenylalanine (L-dopa). It was foundthat: (1) tyrosinase activity existed in allthe skin extracts tested, including pigmented and non-pigmented skins from ocular or blind side of normal and albino turbot, andthe tyrosinase activity ofthe ocular skin extracts was significantly higherthanthat ofthe blind skin extracts from a single individual for both normal and albino turbot. Unexpectedly,the tyrosinase activity inthe extracts from albino skin ofthe ocular side of albino turbot (termed AOA skin) was about 56% higherthanthat from pigmented skin ofthe ocular side of normal turbot (termed PON skin); (2) histochemical staining showedthat tyrosinase activity was present only inthe PON skin but not inthe AOA skin, andthe white skin ofthe blind side of albino (termed WBA skin) and normal turbot (termed WBN skin). A large amount of positive black granules was formed inthe epidermal cells of PON skin but no black granules were formed inthe skins of AOA, WBA and WBN; (3) temperature and salinity have similar effects onthe tyrosinase activity of ocular pigmented and of albino skin extracts, andthe optimal temperature was 5560°C and optimal salinity 26; however, different pH values had different effects onthese tyrosinase activities, andthe optimal pH value of ocular pigmented skin extracts was 7.0 and ocular albino skin extracts 8.0; allthethree activators tested (SDS, trypsin and zymosan) can increasethe activity of tyrosinase in both ocular pigmented and albino skin extracts of turbot. Butthe level of activation onthe ocular albino skin extracts of albino turbot was significantly higherthanthat on ocular pigmented skin extracts of normal turbot.Onthe basis ofthese observations, it is suggestedthat a large amount of wild type tyrosinase is expressed in albino skin butthe tyrosinase activity is blocked by some unknown inhibitory factors andthe blocked activity of tyrosinase can be readily recovered bythe homogenization of skin tissues in vitro.the unknown inhibitory factors need further studying.