Long-term variation in brown trout, Salmo trutta L., stocking success in a large lake: interplay between availability of suitable prey and size at release

Abstract –  Factors affecting long-term variation in brown trout, Salmo trutta L., stocking success were examined in a large lake, Lake Oulujärvi, in central Finland. Brown trout were stocked in spring (late May to early June) in 1974–1991 and in summer (late June to early July) in 1992–2001. The biomass of the vendace, Coregonus albula (L.), population (prey) at release time had the largest positive effect on stocking success within both periods: biomass of adult vendace in spring and both 0+ and adult vendace in summer. Increasing the size of stocked fish had a positive effect if the vendace available at release were only adults. The increasing trend of predator-catch-per-unit-effort (CPUE) [combined CPUE of northern pike Esox lucius L., burbot Lota lota (L.), and pike-perch Stizostedion lucioperca (L.)] through the study period and its negative effect on trout stocking success suggested an increasing effect of predation within the entire time series.     

A test for interaction between brown trout (Salmo trutta) and inanga (Galaxias maculatus) in an artificial stream

Abstract –  The interaction between brown trout ( Salmo trutta ; fork length (FL) range 255–390 mm) and inanga ( Galaxias maculatus ; FL range 55–115 mm) was tested during summer through autumn in an artificial stream consisting of a single run-riffle-pool sequence with a natural food supply. Each experimental trial lasted for 15 days, and consisted of two brown trout and 50 inanga collected fresh from a nearby stream, with each species given prior residence in four replicate tests, totalling eight trials in all. In addition, two control trials (each 10 days), with 50 inanga in each, were run. Brown trout almost exclusively occupied the pool, whereas inanga occupied all habitat types, although in different proportions, when tested with and without brown trout. The proportion of inanga in the pool was appreciably lower in the experimental trials with brown trout than in the control trials with no brown trout; prior residence had no significant effect on inanga habitat use. Mortality of inanga attributable to predation by brown trout ranged from 0 to 40% with a mean of 14.5 ± 4.7%. The results suggest that habitat use and survival of inanga populations in small streams can be adversely affected by brown trout.     

Predation on native sculpin by exotic brown trout exceeds that by native cutthroat trout within a mountain watershed (Logan,UT, USA)

We explored potential negative effects of exotic brown trout (Salmo trutta) on native sculpin (Cottus sp.) on the Logan River, Utah, USA by (i) examining factors most strongly correlated with sculpin abundance (e.g., abiotic conditions or piscivory?), (ii) contrasting the extent of brown trout predation on sculpin with that by native cutthroat trout (Oncorhynchus clarkii utah) and (iii) estimating the number of sculpin consumed by brown trout along an elevational gradient using bioenergetics. Abundance of sculpin across reaches showed a strong (r ≥ 0.40) and significant (P < 0.05) correlation with physical variables describing width (positive) and gradient (negative), but not with abundance of piscivorous brown trout or cutthroat trout. In mainstem reaches containing sculpin, we found fish in 0% of age‐1, 10% of age‐2 and 33% of age‐3 and older brown trout diets. Approximately 81% of fish consumed by brown trout were sculpin. Despite a similar length–gape relationship for native cutthroat trout, we found only two fish (one sculpin and one unknown) in the diets of native cutthroat trout similar in size to age‐3 brown trout. Based on bioenergetics, we estimate that an average large (> 260 mm) brown trout consumes as many as 34 sculpin per year. Nevertheless, results suggest that sculpin abundance in this system is controlled by abiotic factors and not brown trout predation. Additional research is needed to better understand how piscivory influences brown trout invasion success, including in‐stream experiments exploring trophic dynamics and interactions between brown trout and native prey under different environmental conditions.     

草栖钝绥螨对二斑叶螨的捕食作用

为明确草栖钝绥螨Amblyseius herbicolus对二斑叶螨Tetranychus urticae的控制潜能,在温度分别为19、22、25、28和31℃、相对湿度均为（85±5）%、光周期均为16 L∶8 D条件下测定草栖钝绥螨对二斑叶螨各螨态的捕食偏好性、捕食功能反应及自身干扰反应。结果表明,草栖钝绥螨对二斑叶螨幼螨和第1若螨具有嗜食性,对其捕食选择系数分别为2.22和1.27,均大于1.00,对二斑叶螨卵、第2若螨和雌成螨捕食选择系数分别为0.61、0.68和0.22,均小于1.00。在不同温度条件下,草栖钝绥螨对二斑叶螨各螨态的捕食功能反应均符合HollingⅡ型;在19～31℃范围内,草栖钝绥螨对二斑叶螨各螨态的瞬时攻击率、最大日捕食量和捕食能力均随着温度升高呈先升高后降低的趋势,在28℃时达到最大值;而草栖钝绥螨对二斑叶螨各螨态的处理时间随着温度升高呈先缩短后延迟的趋势,在28℃下处理时间最短。在相同温度下,草栖钝绥螨对二斑叶螨卵、幼螨和第1若螨的捕食作用较强。在有限的捕食空间和二斑叶螨密度固定的条件下,草栖钝绥螨单头捕食量和捕食作用率随其自身密度的增加而逐渐下降,说...     

天敌昆虫—蠋蝽的研究进展

蠋蝽是农林上一种十分重要的天敌昆虫,具有地理分布广、捕食种类多、捕食能力强、适应性好等特点,开发应用前景十分广阔。为了系统总结近年来在蠋蝽研究领域取得的一系列进展,本文从蠋蝽的分类地位、地理分布和形态学、生物学特性、人工繁育技术、控害功能研究等方面进行了综述,分析了蠋蝽研究领域当前存在的问题,并对今后的研究方向和应用前景进行了展望。     

Effects of landscape structure on nest predation in roadsides of a midwestern agroecosystem: a multiscale analysis

Nest predation is an important cause of mortality for many bird species, especially in grassland ecosystems where generalist predators have responded positively to human disturbance and landscape fragmentation. Our study evaluated the influence of the composition and configuration of the surrounding landscape on nest predation. Transects consisting of 10 artificial ground nests each were set up in 136 roadsides in six watersheds in south-central Iowa. Nest predation on individual roadside transects ranged from 0 to 100% and averaged 23%. The relationship of landscape structure within spatially-nested landscapes surrounding each roadside transect (within 200, 400, 800, 1200, and 1600 m of the transect line) to nest predation was evaluated by using multiple regression and canonical correlation analyses. The results of this multiscale landscape analysis demonstrated that predation on ground nests was affected by the surrounding landscape mosaic and that nest predators with different-sized home ranges and habitat affinities responded to landscapes in different ways. In general, wooded habitats were associated with greater nest predation, whereas herbaceous habitats (except alfalfa/pasture) either were associated with less nest predation or were not important. Different landscape variables were important at different spatial scales. Whereas some block-cover habitats such as woodland were important at all scales, others such as rowcrops and alfalfa/pasture were important at large scales. Some strip-cover habitats such as gravel roads and paved roads were important at small scales, but others such as wooded roadsides were important at all all scales. Most landscape metrics (e.g., mean patch size and edge density) were important at large scales. Our study demonstrated that the relationships between landscape structure and predator assemblages are complex, thus making efforts to enhance avian productivity in agricultural landscapes a difficult management goal.     

益蝽对草地贪夜蛾高龄幼虫的捕食能力评价和捕食行为观察

为了探究天敌昆虫益蝽对草地贪夜蛾的捕食潜力,本试验在室内条件下评价了益蝽5龄若虫对草地贪夜蛾6龄幼虫的捕食能力,结合田间观察总结了益蝽的捕食行为特点。结果表明：益蝽5龄若虫对草地贪夜蛾6龄幼虫的捕食功能反应符合HollingⅡ模型,对草地贪夜蛾6龄幼虫的日最大捕食量、瞬时攻击率和处理时间分别为4.671头、1.512和0.215 d;益蝽偏食活猎物,对草地贪夜蛾幼虫致死量大,当草地贪夜蛾幼虫密度大时,益蝽将一头猎物刺吸致死后并不持续吸取,而是快速攻击其他猎物,这一特点对于控制草地贪夜蛾种群数量十分有利。     

七星瓢虫对草地贪夜蛾低龄幼虫的捕食能力评价

为了评估七星瓢虫Coccinella septempunctata对重大入侵害虫草地贪夜蛾Spodoptera frugiperda（J.E.Smith）的防控效果,本试验在室内条件下开展了七星瓢虫对草地贪夜蛾1龄、2龄幼虫的捕食功能反应和种内干扰研究。结果表明：七星瓢虫对草地贪夜蛾幼虫的捕食功能反应均符合HollingⅡ模型,七星瓢虫对草地贪夜蛾1龄幼虫的日最大捕食量、瞬时攻击率和处理时间分别为233.100头、1.204和0.103 h;对草地贪夜蛾2龄幼虫的日最大捕食量、瞬时攻击率和处理时间分别为41.220头、1.075和0.582 h。七星瓢虫的搜寻效应随猎物密度的增加而逐渐降低。七星瓢虫对草地贪夜蛾的捕食作用受到较强的种内干扰。试验证明七星瓢虫对草地贪夜蛾具有较好的控害效果,可用于对草地贪夜蛾的防控实践。     

基于两性生命表的以朱砂叶螨为猎物的加州新小绥螨四川种群生长发育、繁殖及捕食率

为全面掌握加州新小绥螨四川种群的种群特征,本试验运用两性生命表开展了以朱砂叶螨为猎物的加州新小绥螨四川种群的生长发育、繁殖与捕食率研究。结果表明,加州新小绥螨四川种群不同发育阶段重叠,在雌成螨产卵期结束前雌成螨特定年龄-阶段存活率S_xj明显高于雄成螨。单位时间（12 h）特定年龄-阶段繁殖力f_x5、特定年龄繁殖力m_x最大值分别为1.74和1.12粒/雌,单雌总产卵量为49.28粒。种群内禀增长率为0.27/d、周限增长率为1.31/d、净增殖率为26.61粒/个体、世代平均周期为12.34 d。在未成熟阶段,加州新小绥螨各螨态特定年龄-阶段捕食率C_xj均呈双峰型,雌成螨和雄成螨捕食率均随时间明显波动。加州新小绥螨取食朱砂叶螨的转化率为4.55、内禀捕食率为0.54、周限捕食率为1.72头。以朱砂叶螨为猎物时,加州新小绥螨四川种群表现出较好的个体发育、种群增长和捕食能力,可作为控制朱砂叶螨的生防资源,值得进一步研究和开发利用;同时朱砂叶螨可作为加州新小绥螨四川种群人工繁殖选择的猎物之一。     

巴氏新小绥螨和尼氏真绥螨的耐饥能力及饥饿对二者捕食朱砂叶螨功能的影响

试验温度25℃条件下,室内测定我国农作物害虫的常用生物防治剂—巴氏新小绥螨Neoseiulus barkeri Hughes和尼氏真绥螨Euseius nicholsi Ehara et Lee的耐饥能力,以及定量分析不同饥饿程度对两种捕食螨捕食朱砂叶螨的功能反应和捕食速度的影响。研究结果表明：两种捕食螨各螨态的耐饥时间与发育历期呈显著正相关（P﹤0.05）。各螨态的阶段存活率与存活时间之间的关系均可用二次抛物线拟合。根据饥饿半致死和致死时间（T50和T95）,巴氏新小绥螨的耐饥能力明显强于尼氏真绥螨。除巴氏新小绥螨雌成螨的耐饥性存活曲线呈拱形外,两种捕食螨其它螨态的耐饥性存活曲线均呈凹形。不同饥饿程度的两种捕食螨雌成螨捕食朱砂叶螨若螨的功能反应均为HollingⅡ型,饥饿程度不能改变它们的捕食功能反应类型,但可使功能反应模型的各参数值发生较大改变。饥饿24 h的巴氏新小绥螨和尼氏真绥螨雌成螨对朱砂叶螨若螨的捕食作用主要集中在取食的前8 h阶段,而未经饥饿处理的两种捕食螨雌成螨在开始捕食的24 h内各阶段的捕食速度变化不大。因此,饥饿处理对两种捕食螨雌成螨的捕食作用有明显影响。