Swimming performance of wild and F1-hatchery-reared Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) smolts

Abstract –  The swimming performance of wild and hatchery-reared smolts of two salmonid species was investigated. Wild Atlantic salmon smolts (WS) and brown trout smolts (WT) of equal size were caught in fish traps during migration. Hatchery-reared smolts of both species (HS and HT for salmon and trout respectively) were first generation offspring from wild broodstock. The swimming performance of individual smolts from the four groups (WS, HS, WT, HT) was tested three consecutive times using a swimming flume with water flowing at a start rate of 0.16 m·s⁻¹ and a constant acceleration rate of 0.167 cm·s⁻² (10 cm·s⁻¹·min⁻¹). Wild caught smolts of both species performed significantly better than those reared in hatchery conditions. The WS group were observed to maintain an average swimming speed ( U _burst) that was 30% faster than the HS group, whereas the wild trout smolts were superior to HT by approximately 25%. Repeated measures revealed species-specific exhaustion patterns. Brown trout smolts maintained consecutive U _burst indicating significant stamina compared with Atlantic salmon smolts that were found to be exhausted by the initial trial.     

Using logbook-based catch-rate data to detect yellow eel population trends in the southern Baltic Sea

Within recent years, a slight but significant increase of European eel Anguilla anguilla (L.) recruitment has been documented, but it remains questionable whether or not the increased recruitment levels resulted in higher eel numbers at the regional scale. To detect the changes in yellow eel numbers, logbook data covering a 15-year time series of catch per unit effort (CPUE) data from the German Baltic Sea were analysed. Monthly mean catch rates were calculated for two different size classes for two passive gears: fyke and stationary trap nets. Change-point analysis was applied to discover changes in the catch data. After a period of decreasing or constant catch rates, the fyke net data indicated that yellow eel numbers increased slightly in recent years in the Baltic Sea. Besides increasing numbers of immigrating juvenile eels, other population dynamics or conservation efforts might have added to the observed positive stock trend.     

Using a telemetry study to assess the boundary net efficiency of an enclosure system used for yellow eel density monitoring

To assess yellow eel (Anguilla anguilla L.) densities in non‐tidal waters, 1‐ha enclosure approach was developed. For unbiased density and biomass calculations, the catchability of the system needs to be evaluated. A telemetry study with 49 tagged eels was conducted in 2015 and 2016 to verify the effectiveness of the 1.8‐m high boundary net. Excluding recaptured eels (N = 10), 42.8% of the released eels (N = 15) escaped the enclosure within 48 hr. Regarding the movement frequency, similar movement patterns were observed for enclosed and escaped eels within 48 hr after release. Based on the telemetry study, it is concluded that the boundary net is recognised as an obstacle by yellow eels, and reduces the escapement of enclosed eels.     

喷嘴直接注入式农药喷洒系统控制方法研究

为了实现农药变量喷洒,准确计量和控制农药的注入速率和注入量很有必要。提出了一种喷嘴直接注入式系统(DNIS)原型,并在此基础上研究了农药喷洒量的控制方法。该系统应用快速响应电磁阀(RRV)向水中注入农药,RRV由100 Hz的脉宽调制(PWM)信号驱动,通过改变PWM信号占空比调节农药注入速率。试验室环境下设计了基于比例-积分-微分(PID)算法的闭环控制策略,将农药注入速率快速稳定在设定值。通过试验测试了RRV、DNIS系统和PID控制器的工作性能。试验结果表明,采用RRV可准确计量农药注入速率,闭环控制策略可获得较稳定的农药速率控制效果,农药注入速率可在4 s内达到设定值,注入速率的稳定性相对于没有控制策略有明显提高。     

Pflanzenschutz mit Pflanzenextrakten (Botanicals): Hintergründe,zwei Fallstudien,Schlussfolgerungen und Standortbestimmung

Plant extracts (botanicals) are of special significance for plant protection, especially in organic farming. This is due to their origin, specific modes of action, toxicological and ecotoxicological properties as well as to ever changing legal, patent, economic and social/political issues. This paper surveys this complex background and presents data on two selected botanicals which pertain to the use of extract fractions from Glycyrrhiza glabra (sweet wood) for control of Bremia lactucae (downy mildew) in lettuce and azadirachtin for control of leafhoppers in Melissa officinalis L. Both compounds exhibited good effects in the greenhouse which were less pronounced or absent in the field. The effects of sweet wood were strongest when applied twice preventively at 5?% concentration. In the greenhouse, this resulted in a lower number of infected plants and smaller leaf areas attacked by the downy mildew pathogen at high disease pressure. Azadirachtin (plant protection chemical NeemAzal®-T/S in combination with the additive Trifolio S-forte; 1.5 l/ha + 3 l/ha in 600 l water per hektar, 3 applications, interval 7 days) was better in controlling leaf hoppers than natural pyrethrins in combination with rapeseed oil (Spruzit Schädlingsfrei; 6 l/ha in 1,000 l water per hektar, 1 application) in the greenhouse and exhibited very high insecticidal efficacy almost equivalent to that of thiacloprid (Calypso 480 SC; 0.12 l/ha in 400 l water per hektar, 1 application) at moderate disease pressure. Thiacloprid, however, is not applicable in organic farming. In order to introduce these promising results in practical plant protection further fundamental studies are needed. These can only be realized by a joint effort of private companies, research and plant protection institutions, as well as public funding bodies. This article is not meant as a presentation of “perfect” results, it is rather an example of the problems and pitfalls that need to be overcome during development of a botanical and its applications. They are the reason why the market for botanicals will remain small.     

Acetylation of wood in combination with polysiloxanes to improve water-related and mechanical properties of wood

Scots pine sapwood was acetylated with ethyltriacetoxysilane using acetic acid as a solvent and sulfuric acid as a catalyst. A weight percent gain (WPG) of 14 % and cell wall bulking of 7 % were obtained after 5 h of reaction time. Pine specimens were acetylated with acetic anhydride in the presence of 1 % ethyltriacetoxysilane, dihydroxy-functional siloxane, acetoxy-functional siloxane, amino-functional siloxane and non-functional siloxane, respectively. Acetoxy-functional siloxane induced the greatest reduction in water uptake with a water repellent effectiveness after 24 h of up to 62 % as compared to acetylated wood. WPG and cell wall bulking increased compared to solely acetylated wood with increasing concentrations of acetoxy-functional siloxane in acetic anhydride; anti-shrink efficiency, however, did not increase. Fungal resistance of pine sapwood and beech as well as mechanical strength properties did not change when 20 % acetoxy-functional siloxane was added to acetic anhydride compared to solely acetylated specimens.     

Behaviour,escapement and mortality of female European silver eels within a regulated lowland river draining into the Baltic Sea

Migration patterns of 146 female silver eels on their way through fresh and brackish water stretches of the Warnow River into the Baltic Sea were studied using acoustic telemetry. The majority of eels (77%) regained their expected downstream migration behaviour after a median rehabilitation time of 2 days. Positive rheotactic behaviour was observed for 23% of tagged eels after release, probably influenced by experimental procedures. The observed silver eel escapement rate was 63%. Two migratory groups were classified by significantly different migratory speed, time of residence in brackish waters and biometric silvering characteristics. Although the classification of silvering stages is based on these measures, the proportions of these stages did not reflect the observed differences in migratory behaviour. In the context of a permanent silver eel descent in the freshwater part of the Warnow River, a permanent escapement was likewise occurring into the Baltic Sea.     

Auswirkungen einer Nachd��ngung im Sommer auf die Frosth?rte von Salix cinerea L. sowie auf ausgew?hlte N?hrstoffe und Biomarker

One year old rooted cuttings were fertilized with Osmocote exact according to 0,8 g N L^{? ? 1} substrate in February 2009. In August half of the plants received the same fertilizer dose while the other half was not refertilized. In autumn 2009 and in spring 2010 early resp. late frost tests were carried out under controlled conditions, furthermore sprouting was evaluated in spring 2010. Frost damage was measured with the electrolyte leakage method. In the early frost test biochemical stress responses like glucose, sucrose and proline were analyzed. In the new shoots N-, P-, and K-concentration were measured. Refertilized plants did not grow more but showed higher N-, P-, and K-concentrations. These plants had more proline in their buds and roots compared to the non-refertilized ones. Sucrose and glucose contents in the roots of refertilized plants were lower than in non-refertilized ones, in the buds there was no difference. Damage due to early frost was independent from refertilization for new shoots and buds but in roots higher for the refertilized plants. In spring 2010 refertilized plants sprouted earlier compared to non-refertilized ones. In buds damage due to late frost slightly increased in refertilized plants while in roots there was no difference between the fertilization treatments.     

Determination of immunoglobulin A concentrations in the serum and cerebrospinal fluid of dogs: an estimation of its diagnostic value in canine steroid-responsive meningitis-arteritis

Previous studies on canine steroid-responsive meningitis-arteritis (SRMA) suggested that elevation of immunoglobulin A (IgA) concentrations in both serum and cerebrospinal fluid (CSF) is specific for SRMA throughout the different disease stages. Recent studies however have raised concerns about the value of this test. The purpose of this study was to investigate the diagnostic value of IgA concentration testing in paired CSF and serum samples. IgA concentrations of 525 paired canine CSF and serum samples were evaluated. Samples were obtained from dogs with SRMA (n=311) and dogs with miscellaneous conditions (n=214) such as other central nervous system (CNS) inflammatory diseases (n=34), CNS tumours (n=46), idiopathic epilepsy (n=42), intervertebral disc disease (n=46) and non-CNS diseases (n=46). Serum IgA concentrations were significantly higher in dogs with untreated SRMA compared to those with other diseases. IgA CSF concentrations were significantly higher in dogs with SRMA compared to other disease categories, with the exception of inflammatory CNS disease. The sensitivity for IgA concentrations in serum and CSF was 91% with a specificity of 78%. Analysis of 525 paired samples confirmed that IgA concentrations were higher in dogs with SRMA. Calculation of the diagnostic value of IgA concentration confirmed that the test is highly sensitive for SRMA. Testing paired CSF and serum samples for IgA is still recommended for the diagnosis of suspected cases of SRMA.