菲律宾蛤仔清洗分级整机设计及参数优化

针对捕捞后菲律宾蛤仔清洗不彻底、分级精度低、破损率高、效率缓慢等难题，本研究设计了一种菲律宾蛤仔清洗分级一体机以实现菲律宾蛤仔清洗与分级作业。确定了毛刷辊配合高压喷淋的清洗方法、滚筒式筛分的分级方式，完成了滚筒筛筛分机构、高压水喷淋结构等关键部件设计、选型。开展了清洗分级一体机作业参数的EDEM离散元仿真分析。仿真结果显示：当毛刷辊转速3 r/min、滚筒筛转速15 r/min、滚筒筛倾角3°时，分级精度为91%。经过样机作业测试，在此参数下分级精度达到91%,蛤仔破损率在1%～2%之间，其壳体附着泥沙冲洗干净。研究表明，该清洗分级一体机实现了对菲律宾蛤仔的高效率、高品质的清洗分级。     

牡蛎清洗试验研究与清洗设备设计

分别采用毛刷、高压水、超声波对牡蛎进行清洗,以去除杂质比重为主要指标,探讨几种方式对牡蛎清洗效果的影响,初步确定最佳清洗参数。结果表明:毛刷、高压水、超声波都能够对牡蛎进行有效清洗。模拟人工冲刷式实验最佳工艺条件为:滚刷转速20 r/min,高压水压力8 MPa,流量15 L/min,时间2~5 min;超声波清洗实验最佳工艺条件为:低频(26 KHz),处理时间5 min。此系列工艺条件下牡蛎无死亡,生态冰温保活9 d后,存活率达到95%以上。以试验参数为基础,设计一种集三种清洗方式为一体的组合式牡蛎清洗设备。     

养殖网箱清洗设备的实验研究

在网箱养殖业中,网箱网衣的清洗是亟待需解决的一个问题.本文主要对自行研制涡旋式网箱清洗设备的使用效率进行研究.通过对4种不同规格的毛刷进行实验分析,评估涡旋式网箱清洗设备的实际清洗效率、清洗时间.通过对耐清洗生物种和对污染性生物再生长的研究,为以后的工作指明方向.最终确定自行研制的涡肇式网箱清洗设备的最佳毛刷长度为15～20 cm,设备的清洗效率为30%以上,最佳清洗时间为下海后2周,实验区耐清洗的生物主要为紫贻贝和牡蛎.同时要根据海区及附着物的不同,选择不同的毛刷材料.在实际养殖过程中,采取机械清洗和其他清洗措施相结合的方法,来解决养殖网箱网衣的清洗问题.     

多段滚筒式罗非鱼高效低损去鳞工艺

滚筒去鳞是鱼类连续去鳞加工的有效方法之一,虽然国内已有去鳞设备应用于实际生产,但实际去鳞效果和损伤等方面还无法完全满足生产需求。为探究不同去鳞部件在滚筒式去鳞加工过程中的实际效果和影响因素,该研究选取钢板网、圆形孔网、角钢刀具和螺纹钢4种去鳞结构件,设计滚筒去鳞实验装置并开展工艺参数研究,测量不同条件下去鳞率并观察分析损伤情况,在此基础上设计多段滚筒去鳞装置并进行试验验证。结果显示,去鳞时间和滚筒转速是影响钢板网和圆形孔网去鳞效果的主要参数,不同去鳞时间下的去鳞率差异显著,去鳞率随时间延长不断上升。在滚筒转速为35 r/min,去鳞时间接近4 min时,去鳞率可达95%;相同时间和转速下,各去鳞部件的去鳞效果依次为钢板网角钢道具圆形孔网螺纹钢,对鱼体的损伤程度依次为螺纹钢圆形孔网角钢道具钢板网;钢板网和圆形孔网组合式多段滚筒去鳞装置,在转速为35 r/min,去鳞时间为3 min时的最高去鳞率可达95%,且损伤率低。研究获得的适宜罗非鱼多段滚筒去鳞装置的工艺参数,可为罗非鱼滚筒去鳞设备的完善和优化提供依据。     

贻贝高压水射流清洗关键参数建模及试验

为解决贻贝传统清洗方式劳动强度高、清洗效果差的问题，搭建了贻贝高压水射流清洗平台。以射流压力、靶距、入射角为变量，射流打击力和射流冲击压力为评价指标，对贻贝外壳进行高压水射流清洗试验；通过Design-Expert软件设计多因素组合试验，建立射流打击力和射流冲击压力的数学模型，使用Box-Behnken响应面寻优得出贻贝高压水射流清洗参数的最优组合；采用最优清洗参数进行射流清洗试验，以验证参数的有效性。结果显示：使用喷射角为65°,内径为2 mm的扇形喷嘴，在射流压力为9.66 MPa,靶距为99.88 mm,入射角为75.38°进行高压水射流清洗时，射流冲击压力为0.011 MPa射流冲击压力远小于贝壳整体曲面的承压能力，清洗后的贻贝表壳完整无裂纹，表壳附着的各类顽固污物基本去除，清洗效果相较于传统清洗方式得到显著提升。高压水射流技术应用于贻贝的清洗，能有效提高贝源的洁净程度和工业化精细处理水平，同时对其他双壳纲贝类的清洗也具有一定的借鉴意义。     

厚壳贻贝定向装置设计与试验

为解决厚壳贻贝前处理阶段人工劳动强度大、定向技术落后的问题,设计了一种新型厚壳贻贝振动定向装置。首先采用三点测力法测量计算出厚壳贻贝的重心位置;结合振动理论对厚壳贻贝受力分析得出运动路线;然后使用Adams软件对其进行运动学仿真;最后利用控制变量法对定向装置的主要参数进行试验。结果显示:当厚壳贻贝的初始姿态为头部朝下,腹部朝右,振动电机频率为28.6 Hz,振动台面倾角为14°时,此种组合状态下的头尾定向成功率为90%,头尾定向平均所耗时间为25 s。研究表明,该装置能够有效与其他厚壳贻贝自动加工设备相衔接,提高自动化程度,降低加工人员配置,同时可为其他贝类的定向试验分析提供参考。     

围网网衣清洗装备的设计与打击力试验

在深海围网养殖过程中，围网网衣容易滋生很多附着物，影响围网内外部水体流动交换，附着物还会加重网衣重量，受海浪冲击时可能造成网衣破损。针对围网网衣清洗难的问题设计了一套围网网衣清洗装备。该装备采用水射流清洗技术，根据选取的高压泵(额定流量50 L/min,额定压力20 MPa)应用水动力学计算该装备喷嘴的理论直径与水射流理论打击力，加工样机进行水射流打击力对比试验来确定其最优喷嘴出水口形状和直径。结果显示：该设备在选配0.8 mm的圆柱形喷嘴时能与该高压泵的额定压力流量相匹配，可对该泵的压力流量进行最大化利用。研究表明，该设备在水下清洗时配有0.8 mm的圆柱形喷嘴能产生的射流打击力最大，且在靶距保持在10 mm内清洗效果最好，并为水射流清洗研究提供参考意义。     

厚壳贻贝剥半壳装置的设计

目前通常采用热加工方法获取贻贝肉,但该方法不能获得新鲜的贻贝肉。为了获取新鲜的带半壳的贻贝肉,首先针对贻贝的生物学特性,采用统计分析的方法确定厚壳贻贝后闭壳肌痕面积、壳长的基本参数,通过力学实验确定拉断后闭壳肌柱所需要力的大小相关参数,从而研制出一种厚壳贻贝剥半壳装置。该装置由工作台、支撑臂、气压缸、开壳刀具、真空吸盘、贻贝固定台及传送带组成。通过有限元分析确定最佳开壳刀具刃口宽度为9 mm,对开壳刀具施加作用力为900 N。该装置能有效提高厚壳贻贝开壳效率,降低人工劳动强度,满足加工企业的需求。     

鲜活海参清洗工艺试验研究

为了解决海参前处理加工环节中的清洗问题,通过引入气泡清洗技术,研发一种新型的适用于鲜活海参清洗新工艺。试验研究发现,气泡清洗能对海参周身体表进行有效的、低损伤、全方位的洗涤,而清洗强度（通入清洗水体的气流量）与清洗时间是海参清洗的重要工艺参数,并与气泡清洗后海参的洗净率和损伤率呈正线性关系。通过试验初步确定：当清洗强度为15 m^3/h,清洗1 min,海参的洗净率可达90%,而损伤率仅为5%。     

褐菖鲉幼鱼对贻贝养殖生境的利用规律初探

嵊泗海域规模庞大的贻贝养殖生境发挥着养护幼鱼的海洋牧场功能,而探查当地趋礁鱼类在幼体阶段对该生境的利用规律可为当地海洋牧场的设计提供重要参考,为此2018年5—7月对舟山北部枸杞岛贻贝场的褐菖鲉幼鱼、附着生物进行了逐月调查,使用自制网具采集目标生物样品,应用相对密度指数和相关分析法分析了褐菖鲉幼鱼在该生境中的栖息密度、栖息方式和空间分布特征,采用胃含物分析法确定其食性特征,并结合耳石轮纹探究其利用该生境的生长周期。结果显示,褐菖鲉幼鱼的栖息密度时空特征上,5—7月在养殖区贻贝串上的栖息密度分别为(10±6)、(7±5)和(5±5)个/串,时间上呈现逐月递减趋势,随时间的推移养殖区外侧幼体逐渐迁移至内侧近岸区直至消失。栖息方式选择上,褐菖鲉幼鱼栖息数量与贻贝串孔隙大小和附着海藻生物量之间皆呈正相关,但并不显著。饵料利用上,养殖区褐菖鲉幼鱼总体维持较高的摄食强度,各月份平均摄食强度皆高于对照区,主要摄食对象为麦秆虫和钩虾,重量百分比为70.9%和28.3%。栖息周期上,养殖区内褐菖鲉幼鱼耳石平均轮纹数为(57±12)个,其利用养殖贻贝串的周期一般约为2～3月,且该生境中幼鱼耳石纹路间距均匀性和条纹清晰度均明显优于岩礁生境。研究表明,枸杞岛的贻贝养殖生境成为褐菖鲉幼鱼额外的栖息环境,在增殖养护褐菖鲉资源方面发挥了积极作用,因此嵊泗海域在建设海洋牧场时可依据贻贝养殖生境的资源养护原理,通过设置浮体结构强化海洋牧场的饵料场和庇护功能,以提高褐菖鲉种群的补充量,为当地休闲海钓的持续发展提供部分保障。     

On-farm production of liquefied catfish protein

A method and the equipment used to process channel catfish (Ictalurus punctatus) offal into a liquid catfish protein (LCP) suitable for use as an animal feedstuff component is described. This process uses the offal following cleaning of the catfish for commercial use, i.e., without additional grinding or chopping. Small amounts of either hydrochloric acid or formic acid can be used to liquefy the catfish offal in 2 h or less. The liquefaction is conducted in a drum fitted with a baffle. The drum is heated to 50°C with water from an overhead manifold while turning on a drum roller. Bones and unliquefied material are removed by screening to yield LCP at pH 4.5.Variations in the processing conditions — grinding, agitation rate, acid employed, and time — did not alter significantly the amount of crude protein or the essential amino acid profile. Acid selection altered the amount of essential free amino acids found, with hydrochloric acid producing the lesser amount. Reducing the agitation rate lowered the amount of essential free amino acids. Comparison of the essential amino acid profile of the LCP with those of catfish, menhaden and herring meals showed lower amounts of these acids but sufficient to warrant use as a feed component.     

MUSSEL CULTIVATION AS A CO-USE IN OFFSHORE WIND FARMS: POTENTIAL AND ECONOMIC FEASIBILITY

More than 50% of the annual worldwide harvest of mussels is produced in Europe. The mussel cultivation in Germany is based on an extensive on-bottom culture and depends entirely on natural resources for food, spat and space. Due to stakeholder conflicts and a lack of spat availability, mussel farmers tend to move offshore where space is not limited and adequate settlement guaranteed. Newcomers – the offshore wind farmers – are covering large areas in the German Bight which in contrast give the opportunity to use these areas in a multifunctional way by accepting mussel cultivation within the wind farms. This study compiles the basic data for offshore mussel cultivation in close vicinity to a designated offshore wind farm in the open sea of the German Bight and employs different case-scenario calculations to illustrate the impact of changing parameter values on overall profitability or non-profitability of this activity. Primary focus is placed on the production of consumer mussels but seed mussel cultivation is also taken into consideration. We show that production of consumer mussels with longline technology is sufficiently profitable even under the assumption of substantial cost increases. This is especially true, if existing capacities could be used. The cultivation of seed mussels depends on the possibility of using existing equipment. A substantial increase of seed mussel prices to at least 0.6 €, given the main cost categories remaining constant, turns this alternative into substantial profitability. This study concludes with providing some recommendations on how favorable terms or actions could further improve profitability of offshore mussel cultivation. Altogether, our results are intended to shed some light on business management topics that future offshore mariculture operators such as traditional mussel farmers should follow in order to be efficient.     

Thermal Death Time of Listeria monocytogenes Cells in Artificially Contaminated Greenshell Mussels (Perna canaliculus)

ABSTRACT

The production of Greenshell mussel (Perna canaliculus) products involves a heating process, known as a blanching or conditioning step, which facilitates opening and inhibits enzymes which can reduce the shelf-life of mussel products.

To determine whether this initial heating process was also listeri-cidal, thermal death times were determined for seven strains of Listeria monocytogenes in raw Greenshell mussels. D-values at 58, 59, 60,61 and 62^CC were calculated to be 17.19, 11.32, 7.46, 4.91, and 3.24 minutes respectively, giving a z value of 5.52°C. This information combined with information on the core temperatures of mussels during processing will enable processors to implement processing regimes to ensure the elimination of any L. monocytogenes cells associated with the raw product. Such a processing regime has the additional benefit of reducing the carriage of pathogens into the processing facility.     

The impact of the adult blue mussel (Mytilus edulis) population on settling of conspecific larvae

The choice of a mussel bed as a settling locality by conspecific mussel larvae is a trade-off between reduced fitness due to an increased risk of larval predation and post-settling food competition with the filtering adults and the benefit from a reduced post-settling mortality. This reduced post-settling mortality may be due to a reduced benthic predation in habitats with high complexity. In a field experiment, the larval settling of blue mussels, Mytilus edulis, was recorded on an artificial substrate 0.25, 1 and 2 m above the bottom during six periods in spring 1999. The experiment was conducted at four stations with dense mussel beds located at two of these stations. Two of the four stations, one with mussel beds and one without, were located in a wind-exposed area and the two other stations in a sheltered area. It was demonstrated that the larval settling was reduced up to 1 m above the mussel beds. A size analysis of the settled mussels indicated that the reduction in settling intensity close to mussel beds was due to a pre-settling process: the larvae were predated by the filtering adult mussels. Settling was significantly affected by wind stress. During periods with a high mean wind velocity and a turbulent water column, the larvae showed a reduced settlement 1 m above a mussel bed relative to 2 m above, whereas the same patterns not could be observed outside a mussel bed. The importance of the filtration activity of the adult mussels and the behaviour of the larvae is discussed. The recruitment of blue mussels into a mussel bed was investigated. Here, significant positive correlations were observed between the density of recruits and density of adult mussels and weights of empty shells. This indicates that the filtering mussels not only increase the mortality of larvae, but also serve as an important substrate reducing post-settling predation from benthic predators.     

Protective socking material for cultivated mussels: a potential non-disruptive deterrent to reduce losses to diving ducks

Predation of cultivated mussels by diving ducks can threaten the viability of mussel farms. Conventional scaring tactics have had limited success at deterring ducks from feeding on cultivated mussels, because of rapid habituation and 24-h feeding cycles of some waterfowl species. We tested a socking material containing a biodegradable protective layer against predation by diving ducks on experimental blue mussel (Mytilus edulis) aquaculture sites in Prince Edward Island, Canada. We also assessed the effect of this new socking material on mussel growth and survival. Results showed that the protective socking has the potential to reduce losses to ducks, but did not perform well for all mussel seed sizes used by the industry. The protective layer also did not biodegrade fast enough, trapping a portion of mussels inside the sock, affecting growth and survival of these mussels. Improvements are needed to make this solution effective for all mussel sizes used by the industry and to make its production more cost effective.     

Evaluation of methods for assessing the retention of seed mussels (Perna canaliculus) prior to seeding for grow-out

The process of catching and relaying wild seed green-lipped mussels, Perna canaliculus, onto grow-out farms in New Zealand is extremely inefficient with the majority of the seed mussels being lost after transfer, mostly due to secondary settlement behaviour of the seed. In an attempt to identify the causes of this behaviour the retention of seed mussels was experimentally determined after exposure to three sub-lethal stressors, desiccation, starvation, and temperature fluctuation. In addition, two types of mussel seed behaviour were tested for their potential for developing a commercially useful method for identifying seed mussels with high retention properties prior to seeding. The two behaviours were the ability of seed mussels to attach by byssus threads to the substrate in slow flowing water, and the ability of seed mussels to pedal walk vertically up through a substrate filled column. Of the three stressors tested only desiccation and starvation significantly reduced mussel seed retention compared to “unstressed” controls by 38% (P < 0.05) and 42% (P < 0.05) respectively. Of the two types of mussel seed behaviour used for attempting to sort seed mussels, only the ability of seed mussels to attach by byssus threads to the substrate in slow flowing water showed any sensitivity for identifying individuals with higher retention properties (P < 0.05). Seed mussels that failed to byssal attach had a 23% lower mean retention, after 10 d experimental grow-out compared to seed that successfully attached. Although significant, this difference was relatively small and is unlikely to provide the basis for the development of a useful commercial seed mussel sorting method. Desiccation and starvation are both stressors that seed mussels are likely to experience during their commercial harvesting, transportation and seeding process. Consequently, seed mussels need to be relayed quickly and under moist conditions to reduce the potential for starvation and desiccation stress. Identifying seed mussels in poor nutritional condition and feeding them prior to seeding out on farms could also help to prevent the intermittent large scale seed mussel losses currently experienced. The application of these findings will assist in making more efficient use of the wild seed mussel resource and significantly lower financial losses to growers in New Zealand.     

Does electrofishing harm freshwater pearl mussels?

1. Two experiments were carried out in a Scottish river to test the effects of electrofishing on endangered freshwater pearl mussels (Margaritifera margaritifera). 2. In the first experiment, two areas of mussel bed were marked out as treatment and control sites and the former was electrofished using standard equipment. The mussels were examined 10 min, 24 h and 35 days after treatment and their shell valve closure responses, burrowing capabilities and gravidities were recorded as signs of normal ‘functioning’. 3. In the second experiment, individual mussels were marked as treatments and controls and the former were electrofished. These mussels were examined as before. 4. No mortalities occurred and no significant differences in ‘functioning’ between treatments and controls were observed in either experiment. 5. Since no measurable treatment effect could be demonstrated, it appears that electrofishing did not adversely affect the short‐term survival of M. margaritifera. Copyright © 2001 John Wiley & Sons, Ltd.     

输水工程中淡水壳菜生物污损影响及防治对策研究

淡水壳菜(Limnoperna fortune)是自然河流的滤食性底栖动物,极易进入输水工程通道,在输水结构上高密度附着生长,造成生物污损,降低输水效率,威胁工程运行。本文介绍淡水壳菜的生态学特性,分析生物污损对输水工程的不利影响,总结目前已采取的防治措施及评估效果,提出应深入开展生物污损风险评估及系统定量研究,建立快速灵敏的监测预警体系等管理对策,为输水工程运行管理提供参考。