Turbidity‐induced changes in emergent effects of multiple predators with different foraging strategies

Abstract – In natural systems, prey frequently interact with multiple predators and the outcome often cannot be predicted by summing the effects of individual predator species. Multiple predator interactions can create emergent effects for prey, but how those change across environmental gradients is poorly understood. Turbidity is an environmental factor in aquatic systems that may influence multiple predator effects on prey. Interactions between a cruising predator (largemouth bass Micropterus salmoides) and an ambush predator (muskellunge Esox masquinongy) and their combination foraging on a shared prey (bluegill Lepomis macrochirus) were examined across a turbidity gradient. Turbidity modified multiple predator effects on prey. In clear water, combined predators consumed in total more prey than expected from individual predator treatments, suggesting risk enhancement for prey. In moderately turbid water, the predators consumed fewer prey together than expected, suggesting a risk reduction for prey. At high turbidity, there were no apparent emergent effects; however, the cruising predator consumed more prey than the ambush predator, suggesting an advantage for this predator. Understanding multiple predator traits across a gradient of turbidity increases our understanding of how complex natural systems function.     

硇洲马尾藻人工育苗常见敌害生物及防治初探

本文调查了硇洲马尾藻人工育苗期间的主要敌害生物,并初步探讨了不同物理方法和化学药剂对其敌害生物的清除效果,旨在为人工育苗栽培提供基础资料。调查发现硅藻、刚毛藻、石莼、浒苔等附生藻类对硇洲马尾藻生长影响较大,蓝子鱼、麦秆虫和藻钩虾的摄食是硇洲马尾藻幼苗海区培育的主要危害。苗帘用5%硫酸铵药浴5min可抑制刚毛藻的生长,以2%柠檬酸药浴5min、0.3%醋酸药浴3min、3%硝酸铵药浴5min等均可药杀石莼、浒苔等附生绿藻,用640mg/L敌百虫浸泡10min可杀灭藻钩虾。     

棉田害虫及捕食性天敌种群消长动态研究

1992—1994年我们对棉田害虫和天敌种群动态进行了详细的调查,结果表明,田间害虫主要有10种,捕食性天故有四大类,各种害虫及天故的消长动态均不相同,相关分析表明,瓢虫类、草蛉类和棉蚜相关性显著,而蜘蛛类、食虫蝽类与棉蚜的相关性不显著,主要与棉田的盲蝽、叶蝉、棉铃虫、叶螨等害虫种群数量及消长动态有关。     

分子标记检测棉田烟粉虱捕食性天敌种类的研究

[目的]为合理利用和保护棉田烟粉虱捕食性天敌提供依据.[方法]利用烟粉虱特异性引物TB-F/TB-R94585,通过检测单头捕食性天敌肠道内烟粉虱残体,查明新疆吐鲁番地区棉田烟粉虱捕食天敌的种类.[结果]在新疆吐鲁番棉田,烟粉虱的捕食天敌涵盖7个目,13个科,有19种.其中12种,菱斑巧斑瓢虫Oenopis conglobata linnaeus、绒螨Allothrornbium sp、全黑飘虫.ccineUa sp、小毛瓢虫Scymnus sp,短刺刺腿食蚜蝇Ischiodon scuteuaris Fabricius、叶盲蝽Phylinae sp、食中齿爪盲蝽Deraeocoris pwtctulatm Fallen、异须微刺盲蝽Campylomma divrsieornis Reuter,蜘蛛类有斜纹猫蛛Oxyopes sertalus L.Koch、八斑球蛛Theridion octomaculasum、跳蛛Salticidae sp,灌木新园蛛Neoscona adianta Walckenaer是国内首次报道的烟粉虱捕食天敌种类.[结论]通过分子标记的方法检测天敌,反应灵敏,操作简便,适合对害虫捕食性天敌的田间普查.     

昆明松华坝水源保护区梨树害虫及天敌数量变动研究*

  通过对昆明市松华坝水源保护区松华乡梨园进行主要害虫、捕食性天敌的组成与数量特征的调查发现：该区域有害虫6目26科49种,主要害虫有蚜虫类、蝽类、天牛类、刺蛾类等;梨树上的主要害虫是梨二叉蚜、稻绿蝽、梨眼天牛、黄刺蛾等。捕食性天敌种类有5目6科17种,主要为瓢虫类、食蚜蝇类、草蛉类、螳螂类和捕食性蜘蛛;天敌与害虫之间有明显的时间与数量的跟随关系,天敌对害虫具有较强的控制作用。     

A review of the distribution, ecology and population dynamics of age-0 walleye pollock in the Gulf of Alaska

This review paper synthesizes published research and unpublished data on the abundance and distribution patterns, ecology and population dynamics of walleye pollock ( Theragra chalcogramma ) during their first year of life (age-0) in the Gulf of Alaska. Distribution patterns have been described using mainly trawl catches, but recently, acoustic methodology has been employed, especially in examining vertical distributions. Although age-0 pollock are found throughout the Gulf, the highest catches occurred west of Kodiak Island. Pollock are pelagic for at least their first 6 months of life but show an ontogenetic increase in depth distribution superimposed on a pronounced diel vertical migration at a larger size. Daily growth rates are variable depending on year, season and area, and growth generally ceases during the winter. The diet of age-0 pollock shifts from mainly copepods in early juveniles to euphausiids by fall, with epibenthic organisms becoming important during the winter months. Feeding occurs mainly at night in surface waters. Age-0 pollock are most frequently associated with gelatinous zooplankton (medusae) and older pollock. Many predators on age-0 pollock have been identified; the most important are arrowtooth flounder ( Atheresthes stomias ), adult pollock, puffins ( Fratercula spp.), murres ( Una spp.), harbor seals ( Phoca vitulina richardsi ) and Steller sea lions ( Eumetopiasjubatus ). Modelling provides some insight into the population dynamics of these juveniles and environmental conditions which interannually affect their survival. These results are discussed relative to the importance of age-0 pollock in the recruitment of this species and to their role in the pelagic ecosystem.     

Residential movements of top predators in Chile’s most isolated marine protected area: Implications for the conservation of the Galapagos shark,Carcharhinus galapagensis,and the yellowtail amberjack,Seriola lalandi

1. Marine protected areas (MPAs) are becoming a widely used tool for the conservation of biodiversity and for fishery management; however, most of these areas are designed without prior knowledge of the basic ecological aspects of the species that they are trying to protect.
2. This study investigated the movement of two top predators: the Galapagos shark, Carcharhinus galapagensis, and the yellowtail amberjack, Seriola lalandi, in and around the Motu Motiro Hiva Marine Park (MMHMP) using MiniPAT satellite tags to determine the effectiveness of this MPA for the protection of these species.
3. The Galapagos sharks (n = 4) spent most of their tag deployment periods inside the MMHMP. However, high intraspecific variability was observed in their movement dynamics. Daily individual maximum movements ranged from 17 to 58 km and the maximum distance from Salas y Gómez Island, the only emergent island within the MMHMP, ranged from 31 to 139 km.
4. The maximum linear distance travelled for a female juvenile Galapagos shark (152 cm total length) was 236 km, which is greater than the maximum distance previously documented for juveniles of this species (<50 km).
5. For the yellowtail amberjack (n = 1), 91% of the satellite geolocations were within the MMHMP, with a maximum daily distance travelled of 6 km. The maximum distance travelled between points was 111 km and the maximum distance from Salas y Gómez Island was 62 km.
6. All archival tagged fish spent most of their time at depths of <50 m and never left the epipelagic zone. Daytime versus night-time differences were pronounced in all individuals but showed high interindividual variability.
7. This study provides a baseline on the movement of these two top predators in the MMHMP and provides valuable insights for the creation of MPAs in the region and elsewhere.

     

Drivers for spatial modelling of a critically endangered seabird on a dynamic ocean area: Balearic shearwaters are non-vegetarian

1. Spatial modelling is an important research tool to improve our knowledge about the distribution of wildlife in the ocean. Using different modelling techniques (MaxEnt and a generalized linear mixed model), a predictive habitat suitability model was developed for one of the most threatened seabirds in the world: the Balearic shearwater, Puffinus mauretanicus.
2. Models were developed using a 10-year dataset from the Gulf of Cádiz (on the south-western Iberian Peninsula), a key foraging area for Balearic shearwaters during migration and the non-breeding season.
3. Predictive habitat maps strongly matched the observed distribution patterns, pointing to bathymetric features as the main modelling drivers. The species was concentrated on shallow areas (up to approximately 100 m in depth) of the continental shelf, very close to the mouth of the Guadalquivir River. In contrast with previous studies, Balearic shearwater distribution in the highly dynamic Gulf of Cádiz was not correlated with areas of high chlorophyll a concentration.
4. This lack of spatial correlation probably arises from the delay between the phytoplankton bloom and the response of the zooplankton and small fish that are preyed upon by Balearic shearwaters, which may result in important displacements of this trophic chain across the Gulf of Cádiz.
5. The analysis presented contributes to a better understanding of the spatial distribution and ecology of the critically endangered top predator in the Gulf of Cádiz and offers important information to improve management plans.

     

Resolving the urban nest predator paradox: The role of alternative foods for nest predators

Urbanization is a leading cause of species endangerment in the United States; however, certain species thrive in urban habitats. The loss of key predators or the addition of new predators in urban areas could alter the structure of urban communities. A reduction in nest predation is hypothesized to explain the high density of urban birds, yet urban areas typically have increased populations of avian nest predators. The loss of important nest predators in urban habitats, prey switching of urban predators, or successful nest defense against avian nest predators could explain this urban nest predator paradox. To assess these hypotheses I compared nest predation rates of Northern mockingbirds (Mimus polyglottos) in parking lots and residential neighborhoods to populations in pastures and wildlife preserves during 2007–2009 in Florida, USA and placed video cameras on a subset of nests in 2008–2009. Data do not support the hypothesis that urban nest predation rates are consistently lower than non-urban nest predation rates. Of the 56 nest predation events recorded, cats were the dominant urban predator and Cooper’s hawks (Accipiter cooperii) were the dominant non-urban predator. There was no evidence for a loss of important nest predators in urban habitats; however, prey switching by Cooper’s hawks likely occurred. There was also indirect evidence for the importance of nest defense. Furthermore, some of the cats recorded as nest predators in residential neighborhoods were owned cats and all but one cat predation event occurred at night. To reduce nest predation rates, cat owners should keep their cats indoors at night.