Using knowledge of behaviour and optic physiology to improve fish passage through culverts

Culverts reduce connectivity for aquatic animals by being both a hydraulic and physical barrier. However, altered light intensity may also be a behavioural barrier to fish movement, especially for diurnal species that have adapted to moving when it is light. We propose that knowledge of optical physiology and fish behaviour, two important mechanisms underpinning movement, can inform efforts to improve fish movement through culverts. We firstly review the sensory systems of fish with reference to visual sense and explore how this affects fish movement. We then highlight theoretical knowledge that can help us understand fish behaviour and the potential mismatch between the conditions under which fish have evolved and altered conditions within culverts. We describe potential knowledge gaps and directions for future research to improve our understanding of how culverts may affect fish movement. Finally, we explore the potential costs and ecological benefits of different mitigation options to identify those with the most promise for managing the light environment in culverts to facilitate movement. For researchers and managers exploring this subject, we suggest an approach that: (a) identifies light requirements for movement by different species, (b) tests movement under different light conditions and (c) considers an integrative assessment method for testing fish behaviour around culverts. Understanding how optical physiology, fish behaviour and culvert design influence fish movement can improve connectivity for a range of species.     

Main stem movement of Atlantic salmon parr in response to high river temperature

Atlantic salmon become thermally stressed when water temperatures exceed 23 °C. To alleviate this stress, they behaviourally thermoregulate by moving to patches of cold water, often forming large aggregations. These patches are known as thermal refuges. Given the consensus that climate change will increase temperatures in Atlantic salmon catchments, thermal refuges will become increasingly important in minimising summer mortalities. While the behaviour of salmonids within thermal refuges is fairly well understood, less is known about their main stem movement in search of thermal refuges or its thermal and temporal cues. We detail the results of a PIT telemetry study to investigate the main stem movement behaviour of thermally stressed Atlantic salmon parr in a temperature‐impacted river. PIT antennas placed around two thermal refuges and at the upstream and downstream limits of their surrounding reach were used to record the movement of salmonids during a heatwave. We observed parr movement at the upstream and downstream antennas 135 min prior to the occurrence of the midpoint of aggregations in the thermal refuges, indicating that Atlantic salmon parr make reach‐scale movements in search of cool water prior to aggregating. Logistic regression showed that the number of degree hours >28 °C predicted the occurrence of main stem movement with a good degree of accuracy, indicating that this temperature represents a fundamental threshold causing Atlantic salmon parr to move towards cool water. Such data could be instrumental in allowing river managers to place limits on human activity within rivers, allowing salmon populations time to recover following heat stress events.     

Dispersal and tributary immigration by juvenile coho salmon contribute to spatial expansion during colonisation

Anadromous fishes are frequently restricted by artificial barriers to movement such as dams and culverts, so measuring dispersal helps identify sites where improved connectivity could promote range expansion and population viability. We used a combination of DNA‐based parentage analysis and mark–recapture techniques to evaluate dispersal by juvenile coho salmon (Oncorhynchus kisutch) in a population in the initial stages of colonisation following installation of fish passage structures at a previously impassable dam on the Cedar River, WA, USA. The spatial distribution of individuals within maternal families revealed that dispersal was common. Among the offspring of radio‐tagged mothers, 28% were collected outside the spawning reach and dispersed up to 6.3 km (median = 1.5 km). Most juveniles captured in a tributary (Rock Creek, where few adults spawned) had immigrated from the Cedar River and represented many different families. Juvenile dispersal therefore provided a secondary phase of spatial expansion following initial colonisation by adults. Consistent with the condition‐dependent dispersal hypothesis, juveniles that dispersed farther upstream in the tributary were larger than fish collected near the tributary mouth. Overall, the results demonstrated widespread dispersal in a system with low coho salmon densities, and this might increase the rate of population growth if it reduces the effects of local density dependence. By implication, juveniles can take advantage of rearing habitats reconnected through barrier removal, even when such areas are located several kilometres from adult breeding grounds.     

Accumulation and Mobility of Salts in Soil as Influenced by Primary Biomethanated Spentwash

A soil column laboratory experiment was carried out at the central campus, Mahatma Phule Agricultural University, Rahuri, India during 2008–2009 to study the accumulation and mobility of salts in Typic Haplusterts as influenced by primary biomethanated spentwash (PBSW). The PBSW was applied in three different levels (0.5, 1.0, and 2.5 cm) and then tap water with low salinity and low sodium hazard (C₁S₁ class) was used to carry out leaching in four different levels of water at the pore volume of soil (WPVS) (0.5, 1.0, 1.5, and 2.0). The electrical conductivity (EC) in the soil increased significantly with increasing levels of PBSW and decreased with increasing levels of WPVS in surface (0–15 cm deep) and subsurface (15–30 cm deep) soil layers. The exchangeable calcium (Ca²⁺), magnesium (Mg²⁺), and potassium (K⁺) increased, whereas exchangeable sodium (Na⁺) decreased with increasing levels of PBSW and WPVS in surface and subsurface layers of soil. The organic carbon content increased with increasing levels of PBSW and decreased with increasing levels of WPVS in both the soil layers. The cation exchange capacity (CEC) increased with increasing levels of PBSW and WPVS in both the soil layers. The exchangeable sodium percentage (ESP) decreased with increasing levels of PBSW and WPVS over the initial values of soil in both the layers. The pH of saturated paste (pHs) was reduced and electrical conductivity of extract (ECe) was increased with increasing levels of PBSW and WPVS in both the layers. The Na⁺ content of saturation paste extract increased significantly with increasing levels of PBSW and WPVS in both the soil layers.     

睡眠运动中女王竹芋叶枕的细胞形态学分析

[目的]研究睡眠运动的机理,分析睡眠运动中的叶枕的形态学变化。[方法]以温室中女王竹芋为研究材料,用石蜡切片法对处于不同运动状态下竹芋的叶枕进行细胞形态学观察与分析。[结果]睡眠状态下的叶枕部韧皮纤维细胞体积增大,而觉醒状态下的叶枕部韧皮纤维细胞体积缩小。[结论]叶枕部细胞吸水撑大后叶子就张开,叶枕细胞排水缩小后叶子就闭合。     

Home range and seasonal movement of taimen,Hucho taimen,in Mongolia

Gilroy DJ, Jensen OP, Allen BC, Chandra S, Ganzorig B, Hogan Z, Maxted JT, Vander Zanden MJ. Home range and seasonal movement of taimen, Hucho taimen, in Mongolia.
Ecology of Freshwater Fish 2010: 19: 545–554. © 2010 John Wiley & Sons A/S Abstract –  Taimen, Hucho taimen, is the world’s largest salmonid and a prized sport fish. We used radio and acoustic telemetry to characterise movements of adult taimen in an extensive river system, the Eg–Uur, in north‐central Mongolia. Forty‐six taimen were tagged with transmitters (27 radio, 17 acoustic and 2 radio‐acoustic combined) and tracked from 2004 to 2008 using mobile surveys and fixed receivers. The mean home range of individual taimen tracked for an average of 2.4 years was 23 km (N = 41, range = 0.5–93.2 km). Of the fish with over 10 relocations (N = 16), 90% remained within a range of 38 km. Four distinct movement patterns were observed: (i) restricted core home range, (ii) core range with seasonal departures, (iii) core range with separate seasonal range and (iv) home range transfer. Movement was greatest in May and June (spawning and postspawning period) with another peak period of movement in September and October (water temperature cooling).     

Obstacles to migration constrain nest distribution of Atlantic salmon

Abstract – Programmes of habitat restoration usually assume that the targeted populations will readily colonise the newly provided habitat. However, this assumption may not always hold, and the success of restoration may be impaired if the individuals are driven to aggregate in areas of the habitat already available instead of spreading to new ones. We investigated how weirs situated along a river could drive Atlantic salmon (Salmo salar) to aggregate their redds and tested whether aggregation intensified at low fish density. For this, we applied spatial point pattern analysis to a data set consisting on the distribution of salmon redds in a small river over 15 years (1992–2006). Within the habitat suitable for spawning, redds were significantly aggregated, especially in the first 15 morphodynamic units below weirs. Our results suggest that the constraint imposed by obstacles on redd distribution should be considered when conducting habitat restoration.     

人参种植的经济分析

针对人参市场价格经常变化,利用最优概率控制模型对人参可持续生产的最低销售价进行经济分析。结果表明,人参生长速度越缓慢,其成本也越高,且人参市场价格对采参年龄起很大作用。若市场人参价格增幅大,最优采参年龄变小;若市场人参价格越低,则最优采参年龄越大,直到停止种植。     

土壤水流动系统及其应用初探

土壤水流动系统是由水势场，介质场，水化学学场，温度场耦合而成，并在时空四维上不断演变化的动态系统，土壤水调控就是通过综合措施改善水流动系统的上下边界年及浅部介质特性，优化田间微水文系统、微气候系统及土壤水流动系统。     

Benefits of repeated stocking with adult,hatchery‐reared brown trout,Salmo trutta,to recreational fisheries?

Abstract  Recaptures of adult, hatchery-reared, brown trout, Salmo trutta L., and fishing time from anglers were used to evaluate the benefits of stocking programmes with repeated releases of adult brown trout. The recapture rate varied between 17% and 29%. The time between stocking and capture (referred to as residence time) varied between 1 and 160 days (median 3–49 days). Between 67% and 84% of trout caught in the river were recently released fish. Fishing effort increased after stocking, thereby increasing the impact of angling on wild stocks. Stocking with adult brown trout decreases the impact of angling on wild trout only if the time spent fishing by all anglers is kept stable. Furthermore, because of the short residence time of stocked trout, long-term impacts through competition for space and food, or genetic impact through introgression, are limited.