Leadership in fish shoals

Leadership is not an inherent quality of animal groups that show directional locomotion. However, there are other factors that may be responsible for the occurrence of leadership in fish shoals, such as individual differences in nutritional state between group members. It appears that front fish have a strong influence on directional shoal movements and that individuals that occupy such positions are often characterised by larger body lengths and lower nutritional state. Potential interactions between the two factors and their importance for positioning within shoals need further attention. Initiation of directional movement in stationary shoals and position preferences in mobile shoals need to be addressed separately because they are potentially subject to different constraints. Individuals that initiate a swimming direction may not necessarily be capable of the sustained high swimming performance required to keep the front position or have the motivation to do so, for that matter. More empirical and theoretical work is necessary to look at the factors controlling positioning behaviour within shoals, as well as overall shoal shape and structure. Tracking of marked individuals whose positioning behaviour is monitored over extended time periods of hours or days would be useful. There is an indication that shoal positions are rotated by individuals according to their nutritional needs, with hungry fish occupying front positions only for as long as necessary to regain their nutritional balance. This suggests that shoal members effectively take turns at being leaders. There is a need for three‐dimensional recordings of shoaling behaviour using high‐speed video systems that allow a detailed analysis of information transfer in shoals of different size. The relationship between leadership and shoal size might provide an interesting field for future research. Most studies to date have been restricted to shoals of small and medium size and more information on larger shoals would be useful.     

Density‐ and size‐dependent mortality in fish early life stages

The importance of survival and growth variations early in life for population dynamics depends on the degrees of compensatory density dependence and size dependence in survival at later life stages. Quantifying density‐ and size‐dependent mortality at different juvenile stages is therefore important to understand and potentially predict the recruitment to the population. We applied a statistical state‐space modelling approach to analyse time series of abundance and mean body size of larval and juvenile fish. The focus was to identify the importance of abundance and body size for growth and survival through successive larval and juvenile age intervals, and to quantify how the dynamics propagate through the early life to influence recruitment. We thus identified both relevant ages and mechanisms (i.e. density dependence and size dependence in survival and growth) linking recruitment variability to early life dynamics. The analysis was conducted on six economically and ecologically important fish populations from cold temperate and sub‐arctic marine ecosystems. Our results underscore the importance of size for survival early in life. The comparative analysis suggests that size‐dependent mortality and density‐dependent growth frequently occur at a transition from pelagic to demersal habitats, which may be linked to competition for suitable habitat. The generality of this hypothesis warrants testing in future research.     

River modification reduces climate resilience of brown trout (Salmo trutta) populations in Ireland

This study investigated interactions between eco‐hydromorphological state, riparian vegetation cover, water temperature and fish community composition in lowland rivers in Ireland. Physical habitat modification of study sites corresponded with degraded eco‐hydromorphological state (degree of ecological and physical modification) and reduced thermal buffering capacity (greater temperature fluctuation and increased frequency of extreme temperature events). This impact was reflected in the fish community, with a shift from a brown trout‐dominated (Salmo trutta L.) fish assemblage to predominance of the more thermally plastic minnow, Phoxinus phoxinus (L.), and stone loach, Barbatula barbatula (L.). Eco‐hydromorphological state may be a central factor affecting the ability of temperate rivers to resist temperature change in a warming climate and to maintain suitable conditions for salmonids and other cold‐water biota. Strategies aimed at climate change proofing of temperate rivers should focus on preserving or re‐establishing the eco‐hydromorphological processes that create habitat complexity and buffer stream temperature.     

Effects of Potassium Lactate and Acetate on Listeria monocytogenes Inhibition,Physicochemical and Sensory Properties of Smoked Catfish Fillets

The objective of this study was to evaluate the effects of liquid and wood smoking with a potassium lactate (PL) and acetate (PA) combination on the quality and inhibition of L. monocytogenes growth in ready-to-eat (RTE) smoked catfish fillets. Catfish fillets were tumbled with PL and PA, and treated with no smoke (NS), wood smoke (WS), liquid smoke 1 (LS1), and liquid smoke 2 (LS2). Wood smoke with antimicrobials (WSWA) showed greater inhibition (p < 0.05) of L. monocytogenes growth than other treatments with the exception of the LS1 treatment with antimicrobials. Consumers preferred (p < 0.05) smoked catfish fillets treated with WS to LS1 with respect to appearance, odor, flavor, texture, and overall acceptability. In conclusion, the use of PL and PA did not have a negative impact on the quality and sensory properties of smoked catfish fillets but had a synergistic effect with wood smoke constituents that inhibited the growth of L. monocytogenes.     

四川泸县龙眼产业现状与发展对策

简述四川泸县龙眼产业现状及发展中存在的问题,提出加强基础设施、技术队伍、合作组织建设,加大投入等对策。     

农垦企业科技项目工作的难点与对策

分析广东省华海糖业发展有限公司科技项目工作中的难点,提出加强该公司在科技项目工作的对策,为国内的农垦企业在完善科技项目管理工作、促进农垦企业项目带动战略顺利实施和实现农垦企业科学发展等方面提供参考和借鉴。     

真空冷冻干燥对方便米饭理化性质的影响

采用电子扫描显微镜(SEM)和X-射线衍射图谱法,对热风干燥和真空冷冻干燥处理的方便米饭的微观结构和结晶结构进行分析。结果表明:真空冷冻干燥法制备的方便米饭表面形成蜂窝状的均匀孔隙结构,纹理比较有规则,无裂痕,同时结晶度较低;而热风干燥的方便米饭结构紧密,无明显空隙,淀粉结晶度较高。     

青海省设施蔬菜现状及发展对策

简述了青海省设施蔬菜发展现状,分析了当前存在的问题,提出了青海省设施蔬菜快速发展的策略。     

Textural and Sensory Properties of Herring (Clupea harengus) Cubes in Chinese-Type Paste as Affected by Prefrying Methods

The aim of this study was to determine the textural and sensory properties of herring (Clupea harengus) cubes prefried by deep frying (DF), mild frying (MF), and vacuum frying (VF) in Chinese-type pastes stored for 25 days at 13–15°C. Three groups of fish cubes in every Chinese-type paste were compared for texture, physical, and sensory properties by carrying out texture profile analysis (TPA), moisture content, color, and sensory analyses; and two types of Chinese-type pastes were investigated, oily Paste (A) and light Paste (B). The results showed that L* of fish cubes decreased significantly (p < 0.05), and a* and b* increased significantly (p < 0.05) in two kinds of Chinese-type pastes. Fish cubes prefried by DF and MF had higher sensory scores in Chinese-type Paste A, while those prefried by DF and VF had higher sensory scores in Chinese-type Paste B.