基于成像声呐的鱼类三维空间分布

针对海洋牧场中鱼群的三维空间分布问题,本研究提出一种利用成像声呐进行位置计算的方法。将成像声呐固定在船舷外侧的水下,并保证波束发射方向和声呐移动方向一致,通过走航的方式采集水下鱼群信息。首先对采集的原始数据进行图像处理,包括图像构建、背景去除、目标提取等,然后利用基于交互式多模型联合概率数据关联算法对水下目标进行关联处理,得到同一个目标在声呐水平视场中不同帧图像中的对应关系,在此基础上根据连续两帧图像中目标位置关系计算目标的空间坐标,最后结合关联算法获得多目标在三维空间中的运动轨迹以及深度分布情况。研究表明,本方法可以有效获取鱼群在水下的三维运动轨迹及其分布情况,这将为鱼类行为分析以及海洋牧场的资源评估提供技术支持。     

一种基于前视声呐的养殖网箱内鱼群数量评估方法

为准确、高效评估养殖网箱场内鱼群数量，科学指导网箱养殖，提出了一种基于前视声呐的养殖网箱内鱼群数量统计方法。方法应用时，以声呐图像处理技术为基础，首先以目标网箱内养殖鱼类在消声水池实验室的声学标定结果为依据，对前视声呐测量声图进行单个鱼体的声学图像阈值划分；其次凭借云台控制声呐旋转，对围栏区域进行遍历探测，随后将声学标定结果确定的阈值作为划分依据，将不同角度所测声学图像中鱼类进行划分、统计，估算得到整个养殖网箱内的鱼类数量；最后结合探测角度以及位置信息，得到网箱养殖区域内的鱼类空间分布特征，用于指导渔民进行后续的网箱养殖。此方法在舟山青浜岛大黄鱼养殖网箱中得以应用。结果显示：该方法估计得到的养殖网箱内大黄鱼数量与人工评估结果基本一致，经多次计算，平均相对误差仅为2.45%,且实现过程更加高效、便捷。本研究能够有效为养殖网箱提供鱼类数量信息，为亟待进行鱼类数量监管的网箱养殖产业提供科学、可靠的数量统计方法，具有广泛的应用场景。     

多波束渔用声呐作用距离预报建模及性能分析

多波束渔用声呐是海洋渔业实现高效、精准和选择性捕捞的重要工具。为了系统分析多波束渔用声呐探测性能及主要制约因素对作用距离的影响,针对圆柱形阵多波束渔用声呐,采用水声学系统仿真的方法,分别对主要为噪声和混响环境下的渔用声呐探测性能进行分析,对不同海况下噪声不同目标强度鱼群的探测性能进行比较,分析窄带系统和宽带系统降低混响的能力,并对噪声和混响混叠环境下的渔用声呐探测性能进行仿真分析;最终,从系统设计、发射方式、接收方式等多个角度提出提高渔用声呐探测性能的方法,为远距离、高分辨率多波束渔用声呐的研制提供改进的方向。     

基于荧光效应和调色板均衡化的小球藻自动计数方法研究

为实现藻类的自动计数,以小球藻为对象,提出一种基于荧光效应和调色板均衡化的小球藻自动计数方法。首先对小球藻荧光显微图像进行预处理,将真彩色小球藻荧光图像转换为256色图像,再采用调色板均衡化算法增强小球藻荧光图像对比度,并利用基于调色板的阈值分割算法将目标藻类与背景进行分割,同时进行计数。结果表明,该计数方法能够避免杂质影响,直接对藻类彩色图像进行图像增强和阈值分割,可以增强图像对比度,避免彩色图像灰度化过程中图像信息损失;采用连通区域标记方法结合连通区域的大小识别低重叠度藻类,可降低重叠藻类对计数结果的影响,从而提高小球藻的计算准确度。研究表明,该方法实现了针对藻类彩色图像的自动计数,且对小球藻的计数精度准确率达到95%以上,高于只使用灰度图像计数的方法。     

基于Ransac算法的多波束点云人工鱼礁提取方法

投放人工鱼礁作为海洋牧场建设的重要环节，其投放质量评估工作日益受到重视。为实现大范围的人工鱼礁三维信息的自动识别与提取，提升人工鱼礁量化评估的质量，提出了一种基于Ransac算法的多波束点云人工鱼礁提取方法。该方法首先利用多波束声呐获取点云，在对点云进行分割、去噪等预处理后，利用Ransac算法将点云分为内外点集，内点集近似拟合为海底平面，外点集为人工鱼礁。在浙江嵊泗马鞍列岛某礁区进行了相关试验，实现了整体和单体鱼礁的提取，提取正确度达94.79%,完整度达91%,能够较好地提取鱼礁的三维形态、位置、尺寸、高度、空方等信息。研究表明，本方法可以大范围地应用于各型人工鱼礁目标投放效果的量化评估。     

应用超声组织定征判断鲟鱼性腺成熟度

为应用超声组织定征纹理分析方法判断鲟鱼性腺成熟度,首先对17尾雌性杂交鲟进行性腺成熟度检测鉴定,其中7尾成熟,5尾未熟,5尾过熟,再应用超声组织定征分析法对上述鲟鱼性腺成熟、未熟、过熟的超声检测图像分别进行灰度特征值计算,选取了角二阶距、相关度、熵、逆差距、对比度5个特征值,定量分析了鲟鱼三个性腺发育期的超声图像的区别,确定了超声组织定征纹理分析方法判断鲟鱼性腺成熟度的可行性。     

利用声呐数据提取磷虾捕捞深度方法研究

为快速确定拖网深度、提高捕捞效率、降低渔业生产成本,文章根据声呐设备元数据(Metadata)提出一种提取指定鱼类目标最佳捕捞深度的方法。声呐设备元数据结构较为复杂且包含大量与目标捕捞对象无关的冗余数据,该研究通过分析简化了原始数据,计算和提取出海底深度、目标强度等信息,根据目标渔业资源类型确定有效数据范围及噪声数据范围,过滤噪声数据后以统计图形式展示有效数据,统计各个深度下的目标渔业资源量,构建深度与目标渔业资源量的关系,由多种方法计算并预测最佳捕捞深度。结果显示,在实验数据调查区域内,磷虾(Euphausia superba,目标强度-69.5～-40.8 dB)的最佳捕捞深度为172.9～187 m。由一段时间内某海域中探测到的声呐数据,可快速计算出该海域内目标渔业资源的最佳捕捞深度。     

鲟鱼鱼糜漂洗工艺优化及其对品质的影响

本研究以鲟鱼(Acipenser sinensis)肉为原料，通过正交实验对鲟鱼鱼糜的漂洗工艺进行了优化，对鱼糜漂洗前后的蛋白质含量及其组成、水分分布、凝胶性能等进行了研究。结果显示，鲟鱼鱼糜的最佳漂洗工艺为：水漂洗1次，盐水漂洗1次，盐的质量分数为0.25%，漂洗时间为1 min。鲟鱼鱼糜经漂洗后，其盐溶性蛋白比例显著升高(P<0.01)；鱼糜中的水分受到的束缚力增加，自由度减小，形成了更为致密的凝胶网状结构；破断力、凹陷距离、凝胶强度、持水力、白度等表征凝胶性能和鱼糜品质的指标明显提升。研究表明，采用恰当的漂洗工艺可显著提高鲟鱼鱼糜的品质。     

航道整治透水框架群对鱼类集群影响的水声学探测

四面六边透水框架作为工程构造物具有良好防冲促淤功能，在航道整治工程中得到广泛应用。为了探究四面六边透水框架群对鱼类的影响，于2014年5－6月，应用EY60回声探测仪和双频识别声呐（ARIS Explorer 1800）对金城洲透水框架工程区水域进行定点水声学监测，并采集工程区附近的渔获物。结果表明，工程区共捕获鱼类114尾，包含3目、4科、12属、14种，体长均值为（27.29±8.84）cm，95%置信区间为 25.65～28.92 cm。EY60回声探测仪对工程区共监测时长9589 min，鱼的数目12356尾，工程区鱼体的目标强度均值为（-63.24±5.79）dB，95%置信区间为-63.35～-63.15 dB；数据独立性T检验显示，工程区与对照区之间无显著性差异（P>0.05）；通过回声探测仪和双频识别声呐对鱼类出现频次监测，工程淹没区是对照区1.18倍，而工程半淹没区却是对照区的0.85倍；说明处于水下的四面六边透水框架群对鱼类具有一定的诱集作用。     

网箱养殖欧洲鲟鱼试验报告

本文阐述了欧洲鲟鱼在网箱中进行人工养殖切实可行是欧洲鲟鱼养殖的最佳模式，利用７５ｍ＾２（３只网箱）养殖２欧洲鲟鱼试验，经过１７０天饲养鲟鱼４５４公斤，单产每平方米６．０５公斤，出箱欧洲鲟鱼３９５民活率９８．８％，平均规格１．１５公斤，饲料系数２．５，投入产出比１：２．１７，获得显著的经济效益和社会效益。总结出网箱养殖欧洲鲟鱼生产配套养殖工艺。     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.     

美人鱼发光杆菌对凡纳滨对虾非特异性 免疫功能及抗病力的影响

在基础饲料中分别添加0.1%和1%美人鱼发光杆菌灭活菌、0.1%美人鱼发光杆菌活菌配制成3种免疫实验饲料,以基础饲料为空白对照组饲料,每组设3个平行样。对个体质量为(4.83±0.36)g的凡纳滨对虾进行为期20 d的饲养实验,分别在0、5、10、15和20d进行取样,以血清中的酚氧化酶(PO)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了美人鱼发光杆菌作为免疫制剂对凡纳滨对虾非特异性免疫效应的影响;在投喂免疫饲料后的第22天,按0.004 2 kg/kg体重的剂量,直接投喂对虾白斑综合征病毒(WSSV)病料,并记录累积死亡率。结果表明,美人鱼发光杆菌免疫实验组对凡纳滨对虾血清中PO、ACP、AKP、UL和SOD活性影响明显高于对照组,并且在饲料中添加美人鱼发光杆菌后,明显提高了对虾抵御WSSV感染的能力。其中0.1%美人鱼发光杆菌活菌实验组的抗病毒感染能力最强,WSSV感染14d内累计死亡率为63.3%±5.8%;而对照组为96.7%±3.3%。研究表明,美人鱼发光杆菌添加在对虾饲料中能提高凡纳滨对虾非特异性免疫水平,增强抵抗疾病的能力,将其作为对虾免疫增强剂具有良好的应用前景。     

Effects of Spirulina platensis as a feed additive on growth and coloration of blue dolphin cichlids (Cyrtocara moorii Boulunger, 1902)

This study was carried out to investigate the effects of replacing fish meal with dietary Spirulina as a feed supplement on the growth performance and coloration of blue dolphin cichlids (Cyrtocara moorii). Five isonitrogenous (47% crude protein) and isocaloric (17.36 kJ/g digestible energy) diets were for formulated to replace FM with 0, 5, 10, 15 and 20% Spirulina (designated as Control, SP5, SP10, SP15 and SP20 respectively) and fed to the fish (initial body weight, 3.15 ± 0.01 g). Fish were randomly distributed into fifteen 120 L aquariums (26.5 ± 1.00°C), 15 fish per aquarium. The diets were tested in triplicate for 12 weeks. Experimental groups were fed twice daily (09:00 and 17:00) by hand to satiation. At the end of the feeding trial, significantly (p < 0.05) higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and lower feed conversion ratio (FCR) were observed in fish fed the SP10 diet when compared to the SP20 diet. There was no significant difference in these parameters between the other groups. The skin coloration of blue dolphin cichlid fed a diet containing Spirulina meal was enhanced. The best coloration was observed in the SP15 group. These impressions were objectively validated by chemical determinations of carotenoids extracted from fish skins and passed statistical tests of significance. The study findings show that Spirulina meal does not diminish growth rates except at very high levels.     

A Minchinia mercenariae‐like parasite infects cockles Cerastoderma edule in Galicia (NW Spain)

The cockle Cerastoderma edule fishery has traditionally been the most important shellfish species in terms of biomass in Galicia (NW Spain). In the course of a survey of the histopathological conditions affecting this species in the Ria of Arousa, a haplosporidan parasite that had not been observed in Galicia was detected in one of the most productive cockle beds of Galicia. Uni‐ and binucleate cells and multinucleate plasmodia were observed in the connective tissue mainly in the digestive area, gills and gonad. The parasite showed low prevalence, and it was not associated with abnormal cockle mortality. Molecular identification showed that this parasite was closely related to the haplosporidan Minchinia mercenariae that had been reported infecting hard clams Mercenaria mercenaria from the Atlantic coast of the United States. The molecular characterization of its SSU rDNA region allowed obtaining a fragment of 1,796 bp showing 98% homology with M. mercenariae parasite. Phylogenetic analysis supported this identification as this parasite was clustered in the same clade as M. mercenariae from the United States and other M. mercenariae‐like sequences from the UK, with bootstrap value of 99%. The occurrence of M. mercenariae‐like parasites infecting molluscs outside the United States is confirmed.     

Sea bream culture in Egypt; status, constraints and potential

Marine fish farming in Egypt began in 1976 with the culture of gilthead sea bream, (Sparus aurata) as this fish was notably adaptable to brackish and marine pond conditions. Today, marine fish and shrimp farms amount to about 19,000 ha, out of which 42% is already in production while the rest, i.e., 58% is still under construction. In 1997, cultured gilthead sea bream production of 2,250 tons made up 3% of the 75,000 tons total aquaculture catch. In polyculture, usually with the grey mullet and sea bass, gilthead sea bream contributed 440 kg ha^–1 to the total yield of 1,700 kg ha^–1 (26%) over a period of 16 months. For the same period, the yield of monoculture ponds averaged 100 kg ha^–1, while in marine cages, yields ranged from 4–10 kg m³. In 1996–1997, fry of 0.25–1 g and fingerlings 1–10 g with a total of 3 million, were collected from the wild and 1 million fry were produced in the three marine hatcheries out of the four existing ones. The development of sea bream culture in Egypt is now severely inhibited by the shortage of seeds and adequate feeds. Exports of both sea bream and sea bass, during 1994–1996 averaged 1,300 tons per year.     

Dietary thiamin and pyridoxine requirements of fingerling Indian major carp,Cirrhinus mrigala (Hamilton)

Two experiments were conducted to quantify the dietary thiamin (experiment I) and pyridoxine (experiment II) requirements of fingerling Cirrhinus mrigala for 16 weeks. In experiment I, dietary thiamin requirement was determined by feeding seven casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) with graded levels of thiamin (0, 0.5, 1, 2, 4, 8 and 16 mg kg^?1 diet) to triplicate groups of fish (6.15 ± 0.37 cm; 1.89 ± 0.12 g). Fish fed diet with 2 mg kg^?1 thiamin had highest specific growth rate (SGR), protein retention (PR), RNA/DNA ratio, haemoglobin (Hb), haematocrit (Hct), RBCs and best feed conversion ratio (FCR). However, highest liver thiamin concentration was recorded in fish fed 4 mg thiamin kg^?1 diet. Broken‐line analysis of SGR, PR and liver thiamin concentrations exhibited the thiamin requirement in the range of 1.79–3.34 mg kg^?1 diet (0.096–0.179 μg thiamin kJ^?1 gross energy). In experiment II, six casein–gelatin‐based diets (400 g kg^?1 CP; 18.69 kJ g^?1 GE) containing graded levels of pyridoxine (0, 2, 4, 6, 8 and 10 mg kg^?1 diet) were fed to triplicate groups of fish (6.35 ± 0.37 cm; 1.97 ± 0.12 g). Fish fed diet containing 6 mg kg^?1 pyridoxine showed best SGR, FCR, PR, RNA/DNA ratio, Hb, Hct and RBCs, whereas maximum liver pyridoxine concentration was recorded in fish fed 8 mg kg^?1 dietary pyridoxine. Broken‐line analysis of SGR, PR and liver pyridoxine concentrations reflected the pyridoxine requirement from 5.63 to 8.61 mg kg^?1 diet. Data generated during this study would be useful in formulating thiamin‐ and pyridoxine‐balanced feeds for the intensive culture of this fish.     

Fertilization by refrigerator stored sperm of the Indian major carp, Labeo calbasu (Hamilton, 1822)

This study reports on the spermatological properties, and on the development of a protocol for refrigerator storage (4°C) of Labeo calbasu (Hamilton, 1822) sperm for artificial breeding. Volume, motility, concentration and pH of the freshly collected sperm were 2.21 ± 0.53 (μL g^?1 of fish weight) (mean ± SD), 95 ± 1 (%), 1.93 ± 0.44 × 10⁹ (cells mL^?1) and 7.56 ± 0.17 respectively. Sperm activation was evaluated at different osmolalities of NaCl solution, and motility ceased completely when osmolality of the extender was ≥287 mOsmol kg^?1. Sperm retained motility for 24, 72 and 108 h, after refrigerator storage when sperm were undiluted, suspended in Alsever's solution and suspended in Alsever's solution containing 5% methanol respectively. Fertilization rate of fresh eggs with sperm stored at 4°C in Alsever's solution and Alsever's solution containing 5% methanol was 77% and 60% with a hatching rate of 60% and 43% respectively. The fertilization and hatching success of the stored sperm suggests potential to use refrigeration for transporting genetic material to hatcheries for artificial breeding of L. calbasu in Bangladesh.     

A novel approach to denitrification processes in a zero-discharge recirculating system for small-scale urban aquaculture

This paper presents an innovative process to solve the nitrate build-up problem in recirculating aquaculture systems (RAS). The novel aspects of the process lie in a denitrification bioreactor system that uses solid cotton wool as the primary carbon source and a unique degassing chamber. In the latter, the water is physically stripped of dissolved gaseous O₂ (by means of a Venturi vacuum tube), and the subsequent denitrification becomes more efficient due to elimination of the problems of oxygen inhibition of denitrification and aerobic consumption of cotton wool. The cotton wool medium also serves as a physical barrier that traps organic particles, which, in turn, act as an additional carbon source for denitrification. Operation in the proposed system gives an extremely low C/N ratio of 0.82 g of cotton wool/g of nitrate N, which contributes to a significant reduction of biofilter volume. The additional advantage of using solid cotton wool as the carbon source is that it does not release organic residuals into the liquid to be recycled. Operation of the system over a long period consistently produced effluents with low nitrate levels (below 10 mg N/l), and there was only a very small need to replace system water. The overall treatment scheme, also incorporating an aerobic nitrification biofilter and a granular filtration device, produced water of excellent quality, i.e., with near-zero levels of nitrite and ammonia, a sufficiently high pH for aquaculture, and low turbidity. The proposed system thus provides a solution for sustainable small-scale, urban aquaculture operation with a very high recovery of water (over 99%) and minimal waste disposal.     

Effects of metomidate anaesthesia or transfer to pur sea water on plasma parameters in ammonia-exposed Atlantic salmon (Salmo salar L) in sea water

Atlantic salmon (Salmo salar L) postsmolts weighing 150 ± 53 g were exposed to 14–15 mg l^–1 TA-N (total ammonia-N) in sea water in 1 m³ tanks for 24h. Blood samples were then taken A) immediately after the fish were netted from the exposure tanks and stunned by a blow to the head; B) 2–20 min after the fish were transferred to 15 l of an anaesthetic solution of metomidate in ammonia-free sea water; or C) 2–20 min after the fish were transferred to 15 l of ammonia-free sea water. Plasma TA-N level was 18% lower in the anaesthetised fish compared to in the fish sampled directly from the exposure tanks (p 0.05), and accordingly 16% lower in the fish transferred to pure sea water although this difference was not significant (p = 0.07). Plasma glucose level was higher in the fish transferred to pure sea water than in the fish receiving the two other treatments (p 0.05), but plasma urea, osmolality, Na^{+, Cl–, Ca2+ or Mg2+} levels did not vary significantly between the different treatments. Plasma TA-N level increased with time in the fish in the metomidate solution (p 0.02).