Design and development of a geothermal temperature control system for broodstock management of channel catfish Ictalurus punctatus

A control system was designed to raise and maintain water temperatures within 0.03-ha earthen ponds to a range conducive for spawning (24–30 °C) channel catfish Ictalurus punctatus. Heating was done during February 2001 to April 2001, when temperatures would have otherwise prohibited spawning (<24 °C). Temperature was increased from 10 °C (ambient) by 2 °C per day, and maintained at 27 °C, by the addition of geothermally warmed water (36 °C). The control system substantially increased the controllability and precision of heating ponds compared to manual operation. Systems were designed to control sets of four ponds. In designing this control system, consideration of biological constraints was essential. Reproduction in channel catfish is most strongly influenced by temperature. Because cold fronts are common during the winter and early spring (January–March), it was essential to ensure that pond temperatures did not fall below the range for spawning. Constraints on the heating rate and temperature variability to maintain fish health and stimulate spawning behavior were considered. Components of the control system included temperature measurement devices (type-T thermocouples), a central electronic control unit, electronic switches and electrically actuated ball valves. In response to the temperature sensed by each thermocouple, the controller sent a message to close or open the valve. When the valve was opened, warm water was added to the pond to increase the average pond temperature. Hardware and algorithm design and initial system testing were the major components of this project. The final design incorporated information on relevant biological parameters and safety features including peak pond temperature, independent aeration and water pressure control mechanisms. Initial results indicate successful control of this biological system, and ongoing studies suggest similar mechanisms may be used for additional control objectives. In particular, this system could be used to vary pond temperatures to study biological responses and to cool ponds by addition of well water during summer months.     

Optimising codend configuration in a multispecies demersal trawl fishery

Abstract The relative efficiencies and selectivities of conventional and modified codends were examined in a demersal trawl fishery targeting several species, including eastern king prawns, Penaeus plebejus (Hess), whiting, Sillago spp. and cephalopods. The modifications to codends included: (i) reducing the circumference; (ii) increasing the mesh size in conventional diamond‐mesh designs; and (iii) orientating meshes on the bar so that they were square shaped. The codends were tested against a fine‐meshed control in paired comparisons onboard three commercial trawlers. The conventional codend comprised 41‐mm diamond‐shaped mesh attached to an anterior extension section at a ratio of 150 to 100 meshes and was demonstrated to be non‐selective for the targeted species. Reducing codend circumference to 100 meshes and increasing the size of mesh to 45 mm both improved selection for eastern king prawns, but the lateral mesh openings were estimated to be insufficient to allow juveniles of the other key species to escape. By contrast, codends made from 35‐ and 41‐mm mesh hung on the bar improved the size selection for eastern king prawns and selected stout whiting, Sillago robusta (Stead) (the smallest commercial‐sized fish) across narrow selection ranges and at 50% sizes of retention (L₅₀s) that were closely correlated to the transverse morphology of fish and the maximum mesh opening. With the exception of a reduction in catches of octopus, Octopus spp., by the 41‐square codend, there were no other impacts on commercial catches by the square‐mesh designs. It was concluded that diamond‐mesh codends are inappropriate for use throughout this multispecies fishery and that a modified design comprising at least 35‐mm mesh hung on the bar is required to minimise the fishing mortality of unwanted sizes of the key target species. The results are discussed in terms of the utility of these types of modifications for closely regulating selection in penaeid‐shrimp trawls.     

Non-specific immunity parameters and the formation of advanced glycosylation end-products (AGE) in rainbow trout, Oncorhynchus mykiss (Walbaum), fed high levels of dietary carbohydrates

The effects of long-term hyperglycaemia (5 months), through feeding high levels of dietary carbohydrates, on the non-specific immunity parameters of rainbow trout, Oncorhynchus mykiss (Walbaum), was assessed. Fish were fed one of three diets composed of a basal diet containing ≈ 14% digestible carbohydrate which was progressively diluted with gelatinized potato starch in the following ratios of basal diet to supplemental carbohydrate (gelatinized potato starch): 65:00, 65:20, 65:35. The three diets were pair-fed based on the feed intake of the fish fed the diet containing the highest level of starch (65:35) and representing 100% intake. The other diets were then fed at different levels in a manner that allowed all the groups of fish in the same block to receive the same amount of the basal diet [e.g. the basal diet (undiluted, 65:00) was fed at 65% of the dietary intake of the 65:35 diet]. Blood glucose concentrations and relative liver-to-body size increased with increased dietary carbohydrate intake. Feeding supplemental carbohydrates resulted in a small increase in weight gain of the fish at both supplemental levels. Pronephros tissue lysozyme activity and pronephros macrophage superoxide production were not affected by the dietary treatments. The results suggest the presence of advanced glycosylation end-products in muscle tissue collagen, but were not significantly different between treatments. No substantial effect of long-term feeding of a high carbohydrate diet on the non-specific immunity of rainbow trout was observed. However, the results suggest that dietary carbohydrates may have a slight stimulatory effect on phagocytosis at low–moderate levels.     

Marine-Derived Xanthone from 2010 to 2021: Isolation,Bioactivities and Total Synthesis

Marine life has proved to be an invaluable source of new compounds with significant bioactivities, such as xanthones. This review summarizes the advances made in the study of marine-derived xanthones from 2010 to 2021, from isolation towards synthesis, highlighting their biological activities. Most of these compounds were isolated from marine-derived fungi, found in marine sediments, and associated with other aquatic organisms (sponge and jellyfish). Once isolated, xanthones have been assessed for different bioactivities, such as antibacterial, antifungal, and cytotoxic properties. In the latter case, promising results have been demonstrated. Considering the significant bioactivities showed by xanthones, efforts have been made to synthesize these compounds, like yicathins B and C and the secalonic acid D, through total synthesis.     

精细农业技术在农业生产上的应用

精细农业可以被定义为一个综合系统,该系统通过应用作物信息、先进的技术以及有效的管理方法等手段使农业生产达到最优化.作为一个真正的综合系统,应该在起始阶段制定好生产、流通以及采后处理阶段的有效策略.其中信息、技术、管理是该生产系统中最为关键的3大因素.……     

向镰刀菌毒素污染的谷物添加葡甘露聚糖对初产母猪生产性能和血液生化指标的影响

研究表明,镰刀菌毒素会导致泌乳母猪的采食量和日增重下降,具有延长母猪从断奶至发情间隔时间的倾向;葡甘露聚糖能够防止由镰刀菌毒素毒性作用引起的血清尿素和总蛋白浓度的下降。