pH值对南美白对虾虾苗成活率的影响

实验研究不同pH值对南美白对虾虾苗成活率的影响,得出以下结论:pH值7.0~9.0范围内虾苗应激较小,成活率较高。pH值低于7.0或高于9.0时,虾苗初期死亡率普遍高于pH值7.0~9.0。pH值的高低会影响到虾苗的成长健康以及成活率大小等问题,研究pH值对南美白对虾苗成活率影响大小,为南美白对虾养殖业提供了重要的科学依据。     

南美白对虾养殖技术 (下 )

3.适时放虾苗 　　南美白对虾最适生长水温为 22～ 35℃，在此水温范围内放虾苗养殖，生长速度快，摄食量大，体质健壮，抗病力强。南美白对虾生活在偏低水温的环境中则摄食量小，体质弱，生长慢，从而养成成活率低。因此南美白对虾在我国南方的放养时间是 4～ 5月份较合适。 　　4.合理的放养密度 　　一般半精养条件下，由于人工控制条件差，设施简单，因此放养虾苗密度一般每亩放 6000～ 10000尾，精养池塘放苗密度为 3万～ 4万尾 /亩。按照目前罗氏沼虾高密度精养，采取轮捕的方法，放养密度高达 5万～ 6万尾 /亩，亩产量已达到 500公斤…     

淡水养殖南美白对虾失败原因及预防(下)

五、放苗时间太早,下塘后水温骤降,引起虾苗死亡。有的养殖户为了使成虾提前上市,有个好价格,就提早放苗。象江浙沿海一带在4月底前就有人放苗,有的甚至在4月20日前不搭建临时保温大棚,就把虾苗放入池塘内。放入时水温在20℃以上,而过几天强冷空气南下,一下子使水温下降到15℃以下。南美白对虾在水温18℃以下时,其摄食、活动就会受到严重影响,体质相对较弱,正在蜕壳或刚蜕壳的虾苗在水温达到16℃以下1天以上,大部分就要死亡。预防方法:江浙地区养殖户放苗时间确定在5月份以后,最好在5月15日至6月15日放苗,这样完全可以避免因水温太低带来的…     

利用锅炉大棚增温培育南美白对虾幼虾技术

南美白对虾不耐低温,水温低于15℃时停止生长,在我国不少地区养殖时间只有4个月左右。我们在南美白对虾池塘养殖前期利用锅炉大棚控温培育幼虾,早繁虾苗经30d左右时间强化培育使其规格达3cm左右（生产中称为锅炉苗）,再放人池塘中养殖.     

南美白对虾幼苗池塘大棚标粗淡化技术初探

因为海水运输虾苗具有成活率高、载运密度大、水质不易变坏等多项优点,所以一般南美白对虾虾苗都采用盐度15左右的海水运输,随着南美白对虾养殖不断向内陆发展,在养殖地标粗淡化虾苗成为养殖过程中不可缺少的一个重要环节。     

南美白对虾病害防治技术

南美白对虾生长快,在合理密度和饲料充足的条件下,水温22-35℃,幼虾经60-70天左右饲养,可养成体长10-12cm、体重10-15g的商品虾,养殖成活率达80％,亩产达200kg以上;南美白对虾抗环境变化能力强,对温度及盐度适应范围甚广,能在水温6-40℃的水域中存活,生长水温15-38℃,最适水温22-35℃;能在盐度0.5‰-35‰的水域中生长,可以在海水池塘半精养和精养;虾苗经淡水驯化后,     

海珍品长途活体运输试验

对虾苗、亲虾及商品海珍品进行保活长途运输试验；结果表明，运输成活率与长途运输时间、运输密度及水温之间有密切关系。在正常水温下，虾苗运输时间长短与其运输密度成反比；亲虾运输，每袋以2－3尾亲虾为宜。海珍品运输与水体pH值密切相关；pH值越低，其运输成活率越低。     

罗氏沼虾苗种运输密度研究

为了探索罗氏沼虾苗种合理的运输模式,通过在室内模拟公路运输环境,采用氧气袋充氧的方式进行不同密度罗氏沼虾苗种运输试验。罗氏沼虾苗种规格为1 cm,设置6000、7000、8000、9000、10000尾/袋5个密度梯度,在温度22℃下,模拟运输8 h后,检测氧气袋中水体的溶解氧、氨氮、p H等水质指标,统计虾苗的成活率,之后按照试验得出的最佳运输密度进行实际运输试验,对成活率加以验证。结果显示,在温度22℃、运输时长不超过8 h时,采用氧气袋充氧方式,罗氏沼虾苗种的运输密度以不超过8000尾/袋为宜。     

淡水养殖南美白对虾挫败原因及预防（下）

有的养殖户为了使成虾提前上市，有个好价格，就提早放苗。象江浙沿海一带在4月底前就有人放苗，有的甚至在4月20日前不搭建临时保温大棚，就把虾苗放入池塘内。放入时水温在20℃以上，而过几天强冷空气南下，一下子使水温下降到15℃以下。南美白对虾在水温18℃以下时，其摄食、活动就会受到严重影响，体质     

南美白对虾苗对pH突变的适应性试验

南美白对虾生长快,适盐性广,抗病力强,已成为我国主要的养殖虾种之一。从沿海到内陆,南美白对虾养殖正如火如荼地开展。养殖户从育苗场或淡化苗场购苗进行放养,由于苗场与养殖水体水质条件的差异如pH值、盐度、温度等的不同,将直接影响下池虾苗的成活率。有人进行了南美白对虾仔、幼虾对盐度突变的适应性研究,为南美白对虾放养时盐度的调节提供了依据,而南美白对虾对pH的适应性研究尚未有报道。本文就对南美白对虾淡化虾苗对pH突变的适应性试验进行了初步探讨,旨在为养殖户科学放养提供理论依据。一、材料与方法1.材料试验于2003年6月29日…     

Tidal and subtidal fluctuations in temperature, salinity and pressure for the winter 1996 larval ingress experiment—Beaufort Inlet, NC

A multidisciplinary field experiment was conducted to compare water properties, larval abundances, and transport and retention processes at Beaufort Inlet and two channels leading to the estuarine nursery grounds. Temperature, salinity and subsurface pressure were monitored in situ for a six-week period during March and April 1996 in each channel. Intensive sampling was performed during two neap-tide periods when water mass conditions in the estuary were significantly different. Currents were stronger in the eastern channel during both experiments. Ebb currents were stronger than flood in both channels. Decreasing subtidal sea level appeared to account for the stronger ebb currents. Subtidal sea level in the inlet responded optimally to north–south (along the inlet axis) wind stress and along a line 15° clockwise of north–south. This direction closely parallels the channel axis of Core Sound and may provide an efficient conduit to carry large volumes of low-salinity Pamlico Sound water into the estuarine complex when winds blow south in this sector. The tidal stream in Beaufort Inlet sets up strong cross-inlet gradients by the advection on the east side of higher salinity shelf water and advection on the west side of Beaufort Inlet plume water. The axial fronts produced by differential advection of these two water masses might play some role in redistributing larvae present in one tidal stream to another.     

饲料磷水平对吉富罗非鱼肠道磷和脂肪酸转运及甘油三酯沉积的影响

摘要:为了探究饲料中不同磷水平对罗非鱼肠道磷和脂肪酸转运及甘油三脂沉积的影响，我们配制了3组不同磷水平的饲料，饲料中磷含量分别为1.21 %（LPD）、1.75 %（MPD）和2.66 %（HPD）），用配制的饲料投喂罗非鱼10周。结果显示：与LPD组相比，HPD组显著增加罗非鱼肠道钠磷协同转运体SLC34A2基因（95.7%）和蛋白（200.1%）的表达，增加肠道组织总磷含量（79.2%）；HPD组上调脂肪酸吸收基因cd36、fabp1、fabp2和fatp1及甘油三酯合成基因dgat1的表达（11.2%~54.0%），下调脂肪酸转运基因apob-100的表达（37.7%），增加游离脂肪酸（NEFA）的含量（241.1%）。与LPD组相比，HPD组显著增加罗非鱼肠道组织甘油三酯（TG）的含量（42.9%）。 综上，我们的研究表明，饲料中高磷水平增加肠道组织TG的含量，上调脂肪酸吸收途径和抑制脂肪酸排出途径。我们的研究为深入揭示磷影响鱼类磷代谢及脂类代谢的机理奠定基础。     

运输胁迫下日本黄姑鱼肝脏抗氧化系统的响应

研究了运输胁迫对日本黄姑鱼(Nibea japonica)肝脏抗氧化能力的影响。胁迫处理后,鱼体肝脏中抗氧化防御指标受到不同程度的影响。超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活力快速升高并显著高于处理前水平(P0.05),之后逐渐下降到与处理前无显著性差异。谷胱甘肽转移酶(GST)活力在处理后也有所升高,但一直与处理前无显著性差异(P0.05)。肝脏中维生素C(VC)含量在处理后1 h显著性升高,以应对氧化压力;而自由基含量先升在胁迫0.5 h后快速降低并恢复到处理前水平。丙二醛(MDA)含量在处理后0.5 h达到最高值,然后快速恢复并与处理前无显著性差异(P0.05)。研究表明,运输胁迫能通过氧化应激反应对日本黄姑鱼造成影响,在胁迫应激反应中SOD和CAT可以作为有效的生物指示剂用于胁迫状态的检测;同时,日本黄姑鱼具有较强的抗氧化防御体系,能较快地清除体内自由基并调整鱼体以适应外界环境的影响。     

Impact of aeration and alkalinity on the water quality and product quality of transported tilapia—A simulation study

The effects of aeration and alkalinity on water quality and product quality of Nile tilapia (Oreochrmis niloticus) were determined for simulated commercial hauling conditions. Three types of aeration were tested: pure oxygen aeration with a fine bubble diffuser (Oxygen), air aeration with medium bubble diffusers (Air), and a combination of both pure oxygen aeration with a fine bubble diffuser and air aeration with a medium bubble diffuser (Mixed). Simulated transport hauls were conducted at two initial alkalinities: 1.74 ± 0.11 meq/L (Low) and 8.84 ± 0.55 meq/L (High).The Air treatments resulted in the lowest carbon dioxide concentration, and the highest pH and un-ionized ammonia concentrations. At high alkalinities, the Air treatments were unable to maintain adequate dissolved oxygen levels. The Mixed treatment resulted in reduced carbon dioxide and dissolved oxygen concentrations. The Oxygen treatment resulted the highest dissolved oxygen, highest carbon dioxide, and lowest pH and un-ionized ammonia. Un-ionized ammonia concentrations were higher with the High Alkalinity treatments because of higher pH. Significant mortality was observed in the Air treatments in both the Low- and High-Alkalinity treatments. Mortality in the Oxygen and Mixed treatments for both low and high alkalinities were comparable to that observed in commercial tilapia transport using fine bubble diffusers and pure oxygen.These results indicate that mortality due directly to hauling water quality will not be increased at high alkalinity, if pure oxygen aeration is used. The potential effects of water quality during hauling on survival and product quality may be less than the impact from (a) physical damage from loading and un-loading and (b) physiological problems resulting from pH and temperature shock during the transfer from the hauling tanks to retail holding systems, especially for fish of reduced fitness.     

Exchange and flux of larval fishes across the western Gulf Stream front south of Cape Hatteras, USA, in winter

To describe exchange and to frame the magnitude of the flux of larval fishes across the Gulf Stream front in winter, collections were taken on the inshore and offshore sides of the frontal zone in 1991, 1993, 1994 and 1995, off Onslow Bay, North Carolina. Collections yielded larval fishes representing 75 families. Of these, the larvae of the families Gonostomatidae or Phosichthyidae consistently occurred on both sides of the frontal zone, yet are exclusively of mesopelagic, deep-oceanic origin; hence, they indicate Gulf Stream-to-shelf water-exchange. The larvae of the clupeid, Brevoortia tyrannus , and the sciaenid, Leiostomus xanthurus , occurred on both sides of the frontal zone, yet spawn on the outer continental shelf in or near the Gulf Stream front; hence these taxa indicate shelf-to-Gulf Stream water-exchange. The mechanisms of exchange, as indicated by the distribution of heat and salt across the front, along with satellite images of sea-surface temperature, were not completely resolved, largely because of the two-dimensional ( x , z ) rather than three-dimensional ( x , y , z ) coordination employed. The observed distributions of indicator taxa did not always conform with expected, given the distribution of heat and salt across the front. Parcels of water exchanged across the front upstream (to the south) and encountered during observation along the cross-shelf transects explains the lack of conformity. Where the expected and observed distributions agreed, the flux was 0.0009 larvae m⁻¹ s⁻¹ for the indicators of Gulf Stream-to-shelf exchange, and 0.0007–0.0030 larvae m⁻¹ s⁻¹ for the indicators of shelf-to-Gulf Stream exchange.     

Transport of subarctic large copepods from the Oyashio area to the mixed water region by the coastal Oyashio intrusion

The lateral transport of organic carbon in large grazing copepods ( Neocalanus cristatus, Neocalanus flemingeri, Neocalanus plumchrus and Eucalanus bungii ) from the Oyashio area to the mixed water region (MWR) by the coastal Oyashio intrusion was estimated using the data of VMPS (vertical multiple plankton sampler) and 1500 dbar-referred geostrophic transport from the CTD (conductivity temperature depth sensor) data of five cruises during June 2001 to April 2002 on a repeat observation section OICE (Oyashio Intensive observation line off Cape Erimo), which extends southeastward from Hokkaido Island, Japan. The transport to MWR by the coastal Oyashio intrusion was estimated to be 5.3 × 10¹¹ g C for the four species. Data from profiling floats also indicated that the copepods were advected from OICE to MWR by the coastal Oyashio intrusion within about 2 months. This transport is considered to be one of the significant sources of organic carbon in MWR as it is larger than the amount of large zooplankton consumed by Pacific saury ( Cololabis saira ) in MWR, one of the dominant copepod predators in this region.     

Effects of the North Pacific Current on the productivity of 163 Pacific salmon stocks

Horizontal ocean transport can influence the dynamics of higher‐trophic‐level species in coastal ecosystems by altering either physical oceanographic conditions or the advection of food resources into coastal areas. In this study, we investigated whether variability in two North Pacific Current (NPC) indices was associated with changes in productivity of North American Pacific salmon stocks. Specifically, we used Bayesian hierarchical models to estimate the effects of the north‐south location of the NPC bifurcation (BI) and the NPC strength, indexed by the North Pacific Gyre Oscillation (NPGO), on the productivity of 163 pink, chum, and sockeye salmon stocks. We found that for salmon stocks located in Washington (WA) and British Columbia (BC), both the BI and NPGO had significant positive effects on productivity, indicating that a northward‐shifted bifurcation and a stronger NPC are associated with increased salmon productivity. For the WA and BC regions, the estimated NPGO effect was over two times larger than the BI effect for pink and chum salmon, whereas for sockeye salmon the BI effect was 2.4 times higher than the NPGO. In contrast to WA and BC stocks, we found weak effects of both horizontal ocean transport processes on the productivity of salmon stocks in Alaska. Our results indicated that horizontal transport pathways might strongly influence population dynamics of Pacific salmon in the southern part of their North American ranges, but not the northern part, suggesting that different environmental pathways may underlie changes in salmon productivity in northern and southern areas for the species under consideration.     

Simulation of the impact of climate change on the egg and larval transport of Japanese anchovy (Engraulis japonicus) off Kyushu Island,the western coast of Japan

In order to investigate the impact of climate change on egg and larval transport of Japanese anchovy (Engraulis japonicus) off Kyushu Island western Japan, we conducted particle‐tracking simulations on transport success/failure to fishing grounds from 1960 to 2007. The modeled transport success since the mid‐1990s increased and decreased in the offshore and coastal zones, respectively, compared with the 1960s and 1970s. The estimated northward shift of the spawning ground and weakened Tsushima Warm Current contributed to increase in modeled transport success to the offshore zone. Conversely, the weakening trend of the modeled onshore current in the Goto‐Nada Sea combined with the northward shift of the spawning ground resulted in unsuccessful larval transport. These results suggest that fluctuations in juvenile and subadult anchovy catches in this area may be attributable to changes in the physical environment. The present study showed that changes in transport success induced by oceanographic fluctuations related to climate change, have the potential to affect anchovy recruitment off the western coast of Japan.     

Modelling the transport of particles in the North Sea with reference to sandeel larvae

The transport of particles representing sandeel larvae in the North Sea is simulated with a three-dimensional circulation model for the years 1976 to 1990. A great year-to-year variability in drift patterns is demonstrated. The results may explain some of the observed differences in recruitment between the main sandeel areas in the North Sea. In the northern sandeel area it seems that strong year classes are unlikely if the retention due to unfavourable currents is poor, and that a high retention in the summer may favour a good year class. In the southern sandeel area no clear coupling between year class strength and larval drift is found, possibly because the retention always seems large enough for a potentially good year class. For more quantitative use of such models in relation to sandeel recruitment, more biological knowledge is obviously needed on larval vertical distribution and timing of sandeel hatching and settling.     

Towards a more complete understanding of the life cycle of brown shrimp (Crangon crangon): modelling passive larvae and juvenile transport in combination with physically forced vertical juvenile migration

In this study we developed and utilized a complex model approach to investigate the impact of stage‐specific transport processes on the development and spatial distribution of brown shrimp (Crangon crangon) post‐larvae and juveniles in the German Bight. First, we focused on drift processes during the pelagic larval stage by coupling an individual‐based model for egg and larval development ‘off‐line’ to a 3D hydrodynamic model utilizing the Lagrangian method. Secondly, we investigated tidal‐induced transport processes after juvenile settlement. To determine the tidal cycle, the model coupling was accomplished ‘on‐line’ by resolving the individual‐based model and hydrodynamic model with the same time step. The vertical migration of juveniles, a prerequisite for the selective tidal stream transport (STST), was modelled as a sub‐grid scale physical process (balance of forces: gravitation, buoyancy, Stoke’s friction and dynamic uplift) and considered complex particle dynamics. We applied the model to test temperature and salinity cues as possible tidal indicators utilized by juvenile brown shrimp. Our results indicated that transport processes could significantly change the timing and spatial distribution of post‐larval abundance. We also showed that the small‐scale hydrodynamic forcing acting on the bodies of juvenile brown shrimps was sufficient to account for the vertical migration required to use STST. For both investigated tidal cues STST performing juvenile brown shrimp were transported on‐shore. A faster and more continuous STST was calculated for the salinity cue, resulting in larger abundances of brown shrimp in estuarine areas.