Egg Predation Research Articles

Predation by signal crayfish Pacifastacus leniusculus on fish eggs and its consequences for coregonid recruitment.

The character and magnitude of predation by the invasive, ectothermic Pacifastacus leniusculus, a crayfish widely introduced to Europe and Japan from North America, on the eggs of coregonid fishes, vendace Coregonus albula and whitefish Coregonus lavaretus were examined by experimentation, modelling and field data. The present results showed that P. leniusculus has the potential to be very efficient predator of fish eggs under winter conditions, but the predation by P. leniusculus did not significantly decrease production of coregonid larvae during the years with a high P. leniusculus population in the study lake. Hence, the mortality caused by the novel invertebrate predator appeared to compensate for other yet unexplored mortality factors instead of having an additive effect on the present salmonids.

Trophic roles of black rats and seabird impacts on tropical islands: Mesopredator release or hyperpredation?

Rats contribute to the decline of tropical seabird populations by affecting their breeding success through direct predation of eggs and chicks. When they coexist with other predators, invasive rats may also generate indirect interactions via the changes they impose on the structure of communities and trophic interactions following invasion (‘hyperpredation process’), or when apex predators are eradicated from the ecosystem (‘mesopredator release effect’). Understanding these effects is necessary to implement restoration operations that actually benefit threatened seabird populations. We investigated these processes on two French tropical seabird islands of the western Indian Ocean, Europa and Juan de Nova, where black rats coexist with two different apex predator species (introduced cats and potentially native barn owls). The parallel use of several methods (diet analysis, stable isotopes, seabird monitoring) to identify trophic roles of rats revealed that the direct impact of rats on seabirds was particularly high on Europa where only rats and owls occur, with high consumption of chicks resulting in low breeding success for several seabird species. We also suggested that hyperpredation associated with top-down regulation of cats is occurring on Juan de Nova, although territoriality of cats may buffer this process. Conversely we found evidence that mesopredator release effect is unlikely, irrespective of the apex predator identity. Considering the most likely effects on both islands we provided recommendations on eradication priorities to mitigate the risk of local extinction that seabirds are currently facing.

Intense predation of non-colonial, ground-nesting bird eggs by corvid and mammalian predators

Context Loss of eggs to predators is a major cause of reproductive failure among birds. It is especially pronounced among ground-nesting birds because their eggs are accessible to a wide range of predators. Few studies document the main causes of clutch fate of ground-nesting birds. Aims The main objective of the present study was to identify the major egg predator of red-capped plovers (Charadrius ruficapillus). We also investigated the effectiveness of the following two primary strategies available to the plovers to avoid egg predation: (1) the placement of clutches under vegetative cover and (2) avoiding predators by nesting outside the peak season of predator occurrence. Methods Remote-sensing cameras were deployed on plover nests to identify egg predators and nests were monitored over four breeding seasons to document reproductive success and fate. An experiment using false clutches with model eggs investigated the influence of nest cover on the risk of egg predation throughout the year. Line-transect surveys were conducted to estimate the abundance of egg predators in and around the wetlands. Key results The little raven (Corvus mellori) was the major egg predator identified in 78.6% of red-capped plover clutches and in 92.4% of false clutches that were camera-monitored. The hatching success of plover eggs was not influenced by nest cover (P = 0.36), but model egg survival in false clutches improved significantly with the presence of nest cover (P = 0.02). The abundance of little ravens increased during the plover breeding season and was highly negatively correlated with false clutch survival (rpearson = –0.768, P = 0.005). Conclusions Little ravens were the major predator of red-capped plover eggs and their abundance increased significantly during the plover breeding season. Any influence of nest cover on hatching success of eggs may have been masked by the extremely high rate of egg loss associated with the increased little raven abundance during the plover breeding season. Implications The high rate of egg predation is likely to have negative consequences on the local red-capped plover population, suggesting management is warranted. Little raven populations have expanded and, thus, their impact as egg predators needs to be investigated especially on threatened species.

Out of sight but not out of mind: corvids prey extensively on eggs of burrow-nesting penguins

Context Egg depredation is a major cause of reproductive failure among birds and can drive population declines. In this study we investigate predatory behaviour of a corvid (little raven; Corvus mellori) that has only recently emerged, leading to widespread and intense depredation of eggs of a burrow-nesting seabird (little penguin; Eudyptula minor). Aims The main objective of this study was to measure the rate of penguin egg depredation by ravens to determine potential threat severity. We also examined whether penguin burrow characteristics were associated with the risk of egg depredation. Ravens generally employ two modes of predatory behaviour when attacking penguin nests; thus we examined whether burrow characteristics were associated with these modes of attack. Methods Remote-sensing cameras were deployed on penguin burrows to determine egg predation rates. Burrow measurements, including burrow entrance and tunnel characteristics, were measured at the time of camera deployment. Key results Overall, clutches in 61% of monitored burrows (n = 203) were depredated by ravens, the only predator detected by camera traps. Analysis of burrow characteristics revealed two distinct types of burrows, only one of which was associated with egg depredation by ravens. Clutches depredated by ravens had burrows with wider and higher entrances, thinner soil or vegetation layer above the egg chamber, shorter and curved tunnels and greater areas of bare ground and whitewash near entrances. In addition, 86% were covered by bower spinach (Tetragonia implexicoma), through which ravens could excavate. Ravens used two modes to access the eggs: they attacked through the entrance (25% of burrow attacks, n = 124); or dug a hole through the burrow roof (75% of attacks, n = 124). Burrows that were subject to attack through the entrance had significantly shorter tunnels than burrows accessed through the roof. Conclusions The high rates of clutch loss recorded here highlight the need for population viability analysis of penguins to assess the effect of egg predation on population growth rates. Implications The subterranean foraging niche of a corvid described here may have implications for burrow-nesting species worldwide because many corvid populations are increasing, and they exhibit great capacity to adopt new foraging strategies to exploit novel prey.

Variation in the Mating Systems of Wrasses (Labridae) at a Spawning Aggregation Site on Guam, Mariana Islands

Event Abstract Back to Event Variation in the Mating Systems of Wrasses (Labridae) at a Spawning Aggregation Site on Guam, Mariana Islands Terry J. Donaldson1* 1 University of Guam Marine Laboratory, United States The wrasses (family Labridae) exhibit a diverse number of mating strategies and behaviors. This diversity is expressed not only interspecifically but also intraspecifically. At Guam, Mariana Islands, over twenty species of wrasses spawn on a small, shallow coral reef known as Finger Reef that projects outward from the main reef into Apra Harbor. Preliminary observations indicated that the mating system utilized by some wrasses varied within species. To examine why this occurs, I utilized direct visual observations supplemented by underwater video and photography. I recorded the identity of the species courting, the number of individuals participating, the distribution of male mating territories, courtship and spawning behaviors, and courtship success. Field work utilized snorkeling for several hours a day variously within the lunar month during 2013-2015. I found that courtship and spawning occurs either in temporary resident spawning aggregations or within a protogynous haremic mating system. Within spawning aggregations, mating systems include a lek-like system with paired spawning, and group or promiscuous spawning. Haremic species followed the traditional single male-multiple female model. Both group-spawning and haremic species, however, also spawned in simple male-female pairs. Sneaking or streaking behavior during pelagic spawning events were observed in all mating systems. The results of these observations found that lek-like behavior and group spawning were dependent upon higher densities of males and females at the site. At lower densities, however, some species reverted to simple paired spawning while others used a haremic system rather than a lek-like system. This suggests that some species of wrasses practice a mixed strategy that is dependent upon fish density during the courtship period. Keywords: courtship behavior, Egg predation, fish reproduction, Mating systems, Spawning aggregation Conference: XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015. Presentation Type: Oral Presentation Topic: Physiology, Behavior and Toxicology Citation: Donaldson TJ (2015). Variation in the Mating Systems of Wrasses (Labridae) at a Spawning Aggregation Site on Guam, Mariana Islands. Front. Mar. Sci. Conference Abstract: XV European Congress of Ichthyology. doi: 10.3389/conf.fmars.2015.03.00054 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 09 Nov 2015; Published Online: 10 Nov 2015. * Correspondence: Dr. Terry J Donaldson, University of Guam Marine Laboratory, Mangilao, Guam, 96923, United States, terryjdonaldson@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract Supplemental Data The Authors in Frontiers Terry J Donaldson Google Terry J Donaldson Google Scholar Terry J Donaldson PubMed Terry J Donaldson Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

蚯蚓对瓦氏黄颡鱼摄食达氏鳇卵的干扰实验

PDF HTML阅读 XML下载 导出引用 引用提醒 蚯蚓对瓦氏黄颡鱼摄食达氏鳇卵的干扰实验 DOI: 10.5846/stxb201309142275 作者: 作者单位: 1.三峡大学 三峡库区生态环境教育部工程研究中心，宜昌 443002;2. 水利部水工程生态效应与生态修复重点实验室，武汉 430079;3. 中国科学院生态环境研究中心，北京 100085,三峡大学 三峡库区生态环境教育部工程研究中心,三峡大学 三峡库区生态环境教育部工程研究中心,三峡大学 三峡库区生态环境教育部工程研究中心,三峡大学 三峡库区生态环境教育部工程研究中心,1.三峡大学 三峡库区生态环境教育部工程研究中心，宜昌 443002;2. 水利部水工程生态效应与生态修复重点实验室，武汉 430079;,水利部水工程生态效应与生态修复重点实验室,三峡大学 三峡库区生态环境教育部工程研究中心 作者简介: 通讯作者: 中图分类号: 基金项目: 楚天学者基金(KJ2010B002);国家自然科学基金(51009082,51210105017);水利部公益性行业科研专项(201201030);水利部水工程生态效应与生态修复重点实验室开放基金;三峡库区生态环境教育部工程研究中心开放基金(KF2013-03) Earthworms can be used to deter predation on sturgeon eggs by darkbarbel catfish Author: Affiliation: 1.Engineering Research Center of Eco-environment in Three Gorges Reservoir Region,China Three Gorges University;2.Key Laboratory of Ecological Impacts of Hydraulic-projects and Restoration of Aquatic Ecosystem, Ministry of Water Resources, Wuhan 430079, China;3.Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China;,,,,,,,Engineering Research Center of Eco-environment in Three Gorges Reservoir Region,China Three Gorges University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:自然水域中中华鲟(Acipenser sinensis)卵常受到敌害鱼类捕食的威胁,瓦氏黄颡鱼Pelteobagrus vachelli(Richerdson)是中华鲟卵的重要敌害鱼类。以中华鲟卵的敌害鱼类瓦氏黄颡鱼为研究对象,选择环毛蚓(Pheretima tschiliensis)为瓦氏黄颡鱼的饵料,以达氏鳇卵(Kalugasturgeon)替代中华鲟卵进行室内实验,通过研究适合瓦氏黄颡鱼摄食的环毛蚓规格,以及环毛蚓干扰瓦氏黄颡鱼摄食达氏鳇卵投放比例,探讨中华鲟卵的保护方法。在水温为(20.0±1.5) ℃的条件下,研究了3种不同体长规格[体长(15.3±1.4) cm、(12.0±2.1) cm、(7.7±0.5) cm]实验鱼个体分别摄食3种不同体长规格环毛蚓(体高为0.3cm,体长分别为8、4、2cm)和达氏鳇卵的摄食率;研究了体长为4cm的环毛蚓对3种不同体长实验鱼摄食达氏鳇卵的干扰效果。实验结果表明:3种体长规格瓦氏黄颡鱼均摄食达氏鳇卵;3种体长规格瓦氏黄颡鱼共同摄食的替代饵料规格为体长4 cm及以下的环毛蚓;适宜干扰实验所选体长实验鱼摄食达氏鳇卵的饵料为体长4 cm的环毛蚓;当环毛蚓与达氏鳇卵数量比例为1 : 1时,可实现达氏鳇卵的保护。研究证明在实验条件下可实现环毛蚓对中华鲟卵敌害鱼类——瓦氏黄颡鱼实施摄食干扰,提示下一步可以尝试选择环毛蚓作为替代中华鲟卵的饵料,进行干扰食卵鱼类摄食中华鲟卵的野外验证试验。 Abstract:The eggs of Chinese sturgeon (Acipenser sinensis), an important native fish species in China, are extremely vulnerable to predation by other fishes in the wild. In some cases, more than 90% of Chinese sturgeon eggs are consumed by predators. Darkbarbel catfish [Pelteobagrus vachelli (Richerdson)] are major predators of Chinese sturgeon eggs. Thus, it is critical to gain a better understanding of the feeding behaviors of Darkbarbel catfish to develop practical ways to protect Chinese sturgeon eggs from predation. In this study, we explore the use of bait as a potential tool to redirect Darkbarbel catfish's feeding away from Chinese sturgeon eggs. In a laboratory experiment, Darkbarbel catfish were fed earthworms (Pheretima tschiliensis) of different sizes, and we observed their feeding habits and preference between earthworms and Kaluga sturgeon eggs. Darkbarbel catfish were captured from a known Chinese sturgeon spawning area at the lower reaches of Gezhou Dam, and fed in the experimental tanks for 30 days to adapt to the experimental environment before beginning feeding trials. The experimental environment was supplied with water at a constant (20.0 ± 1.5) ℃ temperature under natural light conditions. Darkbarbel catfish were divided into 3 groups according to standard body length[ (15.3 ± 1.4) cm, (12.0 ± 2.1) cm, (7.7 ± 0.5) cm] and fed a diet of either different-sized earthworms (body height of 0.3 cm; body length of 8 cm, 4 cm or 2 cm, respectively) or Kaluga sturgeon eggs. The results showed that earthworms of body length of 8 cm can only be eaten by fish in the largest size, whereas earthworms 2 cm and 4 cm in length can be eaten by fish of all sizes. Kaluga sturgeon eggs were eaten by Darkbarbel catfish of all sizes. There were no significant differences between the feeding rates of Darkbarbel catfish on earthworms 2 or 4 cm in length. We also examined whether medium-sized earthworms (body length of 4 cm) could be used to distract Darkbarbel catfish when feeding on Kaluga sturgeon eggs. Darkbarbel catfish were simultaneously offered Kaluga sturgeon eggs and earthworms in different quantities. The results showed that the liklihood of Darkbarbel catfish eating Kaluga sturgeon eggs was close to 0 when the ratio of the quantity of earthworms to Kaluga sturgeon eggs is 1 : 1, while half of the Kaluga sturgeon eggs were eaten when the ratio of Kaluga sturgeon eggs to earthworms is 2 : 1. The findings indicated that 1) Darkbarbel catfish of all size groups will eat Kaluga sturgeon eggs and earthworms; 2) earthworms with body length equal to or shorter than 4 cm could be appropriate as bait for Darkbarbel catfish of all sizes; 3) the ratio of earthworms to Kaluga sturgeon eggs is an important determinant in the feeding preference of Darkbarbel catfish; 4) earthworms could potentially be used as a bait to feed Darkbarbel catfish to mitigate predations on sturgeon eggs; 5) Darkbarbel catfish prefer to eat earthworms rather than Kaluga sturgeon eggs when the ratio of earthworms to eggs reaches or exceeds 1 : 1. Considering the similarity between Chinese sturgeon and Kaluga sturgeon eggs, this study could help inform conservation strategies for the Chinese sturgeon in Yangtze River. Further verifications in the field and on Chinese sturgeon eggs are now needed. 参考文献 相似文献 引证文献

Predation of seabird eggs by Common Mynas on Bird Island, Seychelles, and its broader implications

Predation of seabird eggs by Common Mynas on Bird Island, Seychelles, and its broader implications

A decision framework for prioritizing multiple management actions for threatened marine megafauna.

Resources for conserving biodiversity are invariably insufficient. This situation creates the need for transparent, systematic frameworks to help stakeholders prioritize the allocation of resources across multiple management actions. We developed a novel framework that explicitly prioritizes actions to minimize the impacts of several threats across a species' range. The framework uses a budget constraint and maximizes conservation outcomes from a set of management actions, accounting for the likelihood of the action being successfully applied and accepted by local and Indigenous communities. This approach is novel in that it integrates local knowledge and expert opinion with optimization software, thereby minimizing assumptions about likelihood of success of actions and their effectiveness. To test the framework, we used the eastern Gulf of Carpentaria and Torres Strait population of the flatback turtle, Natator depressus, as a case study. This approach allowed the framework to be applied in a data-poor context, a situation common in conservation planning. The framework identified the best set of actions to maximize the conservation of flatback eggs for scenarios with different budgets and management parameters and allowed comparisons between optimized and preselected scenarios. Optimized scenarios considered all implementable actions to explore how to best allocate resources with a specified budget and focus. Preselected scenarios were used to evaluate current allocations of funds and/or potential budget allocations suggested by different stakeholders. Scenarios that used a combination of aerial and ground strategies to reduce predation of eggs performed better than scenarios that focused only on reducing harvest of eggs. The performances of optimized and preselected scenarios were generally similar among scenarios that targeted similar threats. However, the cost-effectiveness of optimized scenarios was usually higher than that of preselected scenarios, demonstrating the value of conducting a systematic optimization approach. Our method provides a foundation for more effective conservation investments and guidance to prioritize actions within recovery plans while considering the sociopolitical and cultural context of decisions. The framework can be adapted easily to a wide range of species, geographical scales, and life stages.

Reed Parrotbill nest predation by tidal mudflat crabs: Evidence for an ecological trap?

Understanding the relationships between nesting habitat quality and predation risk is essential for developing appropriate conservation management for threatened species. This is particularly relevant where anthropogenic pressures could decouple the environmental cues used by birds to assess nesting habitat quality from increased predation risk. In this study, we conducted a series of surveys and nest experiments to examine the nest predation rates of Reed Parrotbill (Paradoxornis heudei) a passerine bird between inland and tidal reed‐bed wetland habitats, at Yellow River Delta National Nature Reserve, Eastern China during 2008, and 2010–2012. We found significant differences in the habitat structural characteristics between the two adjacent wetland habitats that are critical for Reed Parrotbill nest‐site selection. Experimental trials using recently constructed and abandoned Reed Parrotbill nests as ‘artificial nests, quail eggs and predator‐exclusion measures, revealed that tidal mudflat crab (Helice tientsinensis) was the primary cause of Reed Parrotbill egg predation in tidal reed‐bed habitat. Annual predation rates of real nests from inland reed‐bed habitat varied from 35% to 68%, and predation rates of artificial nests were much lower than those from real nests. Pitfall sampling revealed that the abundance of tidal mudflat crabs was significantly higher in tidal reed‐bed habitat. Our data suggested that Reed Parrotbills breeding in tidal reed‐bed habitats may be highly vulnerable due to extremely high rates of nest predation (up to 100%), caused primarily by the high density of tidal mudflat crabs. The incongruence between nest‐site habitat preference and nest survival indicated an ecological trap scenario, which requires further studies on its proximate and ultimate causes as well as the development of effective conservation management for the Reed Parrotbill.

Factors Affecting the Spatial Distribution of Oviposition Sites for Tandem Black Saddlebags Dragonflies (Odonata: Libellulidae)

Oviposition site location may be affected by (1) factors influencing the costs and benefits to the offspring (e.g., resource availability, competition, predation risk) and (2) factors influencing the costs and benefits to the female (e.g., predation risk or mate harassment). In cases in which both the male and female are involved in locating a site, costs and benefits may differ for each parent and the resulting oviposition site location may represent the outcome of selection pressures on one or both of them. We studied oviposition behavior in the black saddlebags dragonfly (Tramea lacerata Hagen), a species in which the male and female typically remain together (i.e., in tandem) while traveling among potential oviposition locations. Oviposition sites tended to be away from pond shoreline at the outer edge of the vegetation on the water’s surface. We found that tandems distributed their oviposition locations widely around the pond, and interactions with other dragonflies (typically other T. lacerata, either territorial males or tandems) led to a larger distance between consecutive oviposition locations. Interestingly, for 10% of the tandems, the female became separated from the male and oviposited solitarily multiple times. These solitary females spent significantly less time and traveled significantly smaller distances between successive oviposition sites than when in tandem. Our results indicate that while some aspects of oviposition behavior and site selection may be consistent between the male and female (e.g., the characteristics that make a site suitable), other aspects, such as the distribution of sites, may be a result of a differing benefits and costs for the two sexes, perhaps as a consequence of potential sperm competition.

Sculpin Predation on Lake Trout Eggs in Interstices: Skull Compression as a Novel Foraging Mechanism

Lake Trout (Salvelinus namaycush) spawn in fall and hatch in spring; to protect their eggs over the winter they spawn on rocky reefs, where the eggs settle deeply into interstices. Uptake of water swells the eggs, further protecting them by lodging in crevices. Freshwater sculpin (Cottidae), the primary predator of salmonid eggs, are small, benthic fishes with malleable bodies and large heads. To acquire the lipid-rich resource contained in eggs, sculpin must penetrate deeply into interstices, and have a method to extract lodged eggs. We placed Slimy Sculpin (Cottus cognatus) into a tunnel containing a sequence of funnels with progressively smaller openings to determine the smallest hole they could enter. Forty-three of 138 Slimy Sculpin (31%) moved through openings up to 19.7% smaller than the maximum width of their head, indicating that they compressed their skull to move through the opening. We examined egg acquisition behavior by placing Lake Trout eggs into holes drilled in a Plexiglass plate. Holes ...

A novel model of predator–prey interactions reveals the sensitivity of forage fish: piscivore fishery trade-offs to ecological conditions

AbstractEcosystem-based fisheries management seeks to consider trade-offs among management objectives for interacting species, such as those that arise through predator–prey linkages. In particular, fisheries-targeting forage fish (small and abundant pelagic fish) might have a detrimental effect on fisheries-targeting predators that consume them. However, complexities in ecological interactions might dampen, negate, or even reverse this trade-off, because small pelagic fish can be important predators on egg stages of piscivorous fish. Further, the strength of this trade-off might depend on the extent to which piscivorous fish targeted by fisheries regulate forage species productivity. Here, we developed a novel delay-differential bioeconomic model of predator–prey and fishing dynamics to quantify how much egg predation or weak top-town control affects the strength of trade-off between forage and piscivore fisheries, and to measure how ecological interactions dictate policies that maximize steady-state profits. We parameterized the model based on ecological and economic data from the North Sea Atlantic cod (Gadus morhua) and Atlantic herring (Clupea harengus). The optimal policy was very sensitive to the ecological interactions (either egg predation or weak top-down control of forage by predators) at relatively low forage prices but was less sensitive at high forage fish prices. However, the optimal equilibrium harvest rates on forage and piscivores were not substantially different from what might be derived through analyses that did not consider species interactions. Applying the optimal multispecies policy would produce substantial losses (>25%) in profits in the piscivore fishery, and the extent of loss was sensitive to ecological scenarios. While our equilibrium analysis is informative, a dynamic analysis under similar ecological scenarios is necessary to reveal the full economic and ecological benefits of applying ecosystem-based fishery management policies to predator–prey fishery systems.

Gender-specific benefits of eating eggs at resident reef fish spawning aggregation sites

Food resource availability has a fundamental role in shaping consumer populations through changes in energy intake. Tropical reef fish spawning aggregations provide a resource pulse for reef-based planktonic egg predators, and an opportunity to quantify the energetic repercussions of natural changes in food availability in tropical reef fishes. We examined the effects of the consumption of eggs from the broadcast spawning surgeonfish Ctenochaetus striatus on the allocation of energy to body condition, growth and reproduction in the planktivorous egg-predator damselfish Abudefduf vaigiensis. Fish that fed on eggs at resident fish spawning aggregation sites (FSASs) had significantly greater lipid storage in liver vacuoles compared to conspecifics from non-FSASs. Growth of male A. vaigiensis was faster at FSASs than non-FSASs. However, we found no differences in the growth of females among sites. Female A. vaigiensis from FSASs in vested more into reproduction, having larger gonadosomatic indices (GSI) than females from non-FSASs, while there was no difference in the GSI of males among FSASs and non-FSASs. At the same locations, no differences were found in the life-history traits of the reference species, Pomacentrus moluccensis, which does not consume eggs. This study demonstrates the role of natural variations in food availability on energetic processes in reef fish. Furthermore, the sex-specific energy allocation strategy highlights the complexity of the interaction between natural variations in food availability and life-history strategies. This study demonstrates that the conservation of FSASs may also benefit trophically linked reef fishes.

Field and laboratory selection of brassicaceous plants that differentially affect infestation levels by Delia radicum

AbstractSeveral plant traits control plant–insect interactions and shape host range of herbivorous insects according to their degree of dietary specialization. Understanding how plant species diversity influences herbivore infestations is of interest for the development of alternative crop protection strategies. In a pest management context, an appropriate selection of plants can modify pest distribution at the field scale. To develop a ‘push–pull’ strategy against the cabbage root fly, Delia radicum, we conducted a field study to both determine which plants exhibit contrasted pest infestation levels and to evaluate their influence on egg predation activity. Our field experiment reveals that infestation levels of brassicaceous plants by the cabbage root fly in the field can vary considerably according to plant genotype and species, while the number of predated eggs is only slightly affected by plant species. Olfactometry studies carried out under laboratory conditions revealed that plants harbouring the highest number of eggs in the field were also highly attractive, suggesting that olfactory stimuli are responsible, at least partially, for the differential infestation levels observed in the field. In a ‘push–pull’ context, this study demonstrates that different brassicaceous plants could be used to redistribute cabbage root flies in broccoli crops without compromising herbivore control by natural enemies. In addition, the importance of plant volatiles for infestation levels suggests a potential for developing a semiochemically assisted ‘push–pull’ system in which trap plants would be enhanced by synthetic release of attractive compounds.

Preference for outbred host plants and positive effects of inbreeding on egg survival in a specialist herbivore.

Inbreeding can profoundly affect the interactions of plants with herbivores as well as with the natural enemies of the herbivores. We studied how plant inbreeding affects herbivore oviposition preference, and whether inbreeding of both plants and herbivores alters the probability of predation or parasitism of herbivore eggs. In a laboratory preference test with the specialist herbivore moth Abrostola asclepiadis and inbred and outbred Vincetoxicum hirundinaria plants, we discovered that herbivores preferred to oviposit on outbred plants. A field experiment with inbred and outbred plants that bore inbred or outbred herbivore eggs revealed that the eggs of the outbred herbivores were more likely to be lost by predation, parasitism or plant hypersensitive responses than inbred eggs. This difference did not lead to differences in the realized fecundity as the number of hatched larvae did not differ between inbred and outbred herbivores. Thus, the strength of inbreeding depression in herbivores decreases when their natural enemies are involved. Plant inbreeding did not alter the attraction of natural enemies of the eggs. We conclude that inbreeding can significantly alter the interactions of plants and herbivores at different life-history stages, and that some of these alterations are mediated by the natural enemies of the herbivores.

Invasive House (Rattus Rattus) and Brown Rats (Rattus Norvegicus) Threaten the Viability of Red-Billed Tropicbird (Phaethon Aethereus) in Abrolhos National Park, Brazil

Destruction of nests and predation by introduced species are among the main factors responsible for seabird declines. The red-billed tropicbird ( Phaethon aethereus) is a tropical, colonially nesting seabird whose distribution in Brazil is restricted to a small, isolated breeding colony located within Abrolhos National Park. This represents the southernmost population of the species in the western Atlantic, and is among the most southerly in its global distribution. Despite its isolation, the population on Abrolhos is threatened by egg predation by two invasive rat species: the house rat ( Rattus rattus) and brown rat ( Rattus norvegicus). In this study we conduct a population viability analysis of P. aethereus in Abrolhos to estimate the potential long term impacts of the rats. Our results indicate that egg and chick predation by rats has the potential to quickly drive the Abrolhos tropicbird population into serious decline. Reducing this threat may require the urgent implementation of a rat control program.

Predation of Eggs and Recently Hatched Larvae of Endemic Ringed Salamanders (Ambystoma annulatum) by Native and Introduced Aquatic Predators

Predation is a key determinant of pond community structure, yet not all predators are equally effective and not all life stages of potential prey are similarly susceptible. Understanding the effects of native and introduced species is essential to informing management strategies, especially for endemic and species of conservation concern. We examined the effects of five common predators (three native: Central Newts [Notophthalmus viridescens louisianensis], aeshnid dragonfly naiads [Aeshnidae], and Southern Leopard Frog tadpoles [Lithobates sphenocephalus]; and two introduced: Fathead Minnows [Pimephales promelas] and Mosquitofish [Gambusia affinis]) on survival of eggs and recently hatched larvae of Ringed Salamanders (Ambystoma annulatum). We also examined the effect of supplemental food or cover availability on survival at each stage. Predators primarily showed a binary response to eggs, consuming all or none of them. Supplemental food did not influence whether eggs or larvae were consumed. Larvae were consumed by all predator species although the effect varied. The presence of cover did not reduce the impacts of the other predators on larval survival. Overall, the two introduced fish species had a greater impact on survival of the early stages of Ringed Salamanders than did the native predators. Further inquiries into the susceptibility of different life stages and survival will improve conservation strategies for rare and endemic species such as Ringed Salamanders.

Foretičtí roztoči lýkožrouta smrkového Ips duplicatus (Coleoptera: Curculionidae: Scolytinae) z oblasti recentní gradace ve střední Evropě / Phoretic mites (Mesostigmata) on double-spined spruce bark beetle Ips duplicatus (Coleoptera: Curculionidae: Scolytinae) in recent oubreak area in the central Europe

Abstract Phoretic mites can be predators of eggs and larvae of bark beetles. Phoretic mites associated with Ips duplicatus have not been systematically studied so far. Therefore, we studied the spectrum and abundance of phoretic mites associated with this species in the eastern part of the Czech Republic. Beetles were sampled with pheromone traps. In total, 500 beettle individuals were captured. From their bodies and the sediment of collecting bottles, 292 mite individuals were collected, and three species of phoretic mites (Mesostigmata) were identified. The most numerous species was Dendrolaelaps quadrisetus. This mite species as well as the other identified species Uroobovella ipidis were not known as phoretic on I. duplicatus before. The second most numerous species was Trichouropoda polytricha known from galleries of I. duplicatus. Total abundance and the number of phoretic mites per beetle as well as the species spectrum significantly differed between localities. The values of abundance and species spectrum were similar to I. typographus

Preliminary survey of a nemertean crab egg predator, Carcinonemertes, on its host crab, Callinectesarcuatus (Decapoda, Portunidae) from Golfo de Nicoya, Pacific Costa Rica.

The possible presence of egg predators in brood masses of portunid crabs from Pacific Central America has not been studied yet. This survey reports the finding of a nemertean crab egg predator on the portunid crab, Callinectes arcuatus, from the Golfo de Nicoya, Pacific Costa Rica. Nemerteans were found in the egg masses of 26 out of the 74 crabs for a prevalence of 35%. The intensity (mean number of worms/ infected crab) was estimated to be 18 with a variance of 1–123 worms/infected crab. No nemerteans were observed either in the 19 Callinectes arcuatus from Golfo Dulce (southern Pacific coast) and the 10 Portunus asper from Herradura-Jaco (central Pacific coast). This nemertean is a member of the genus Carcinonemertes, which has been reported from the Caribbean coast of Panama. However, the encountered Carcinonemertes sp. is the first published finding and report from Costa Rica and Pacific Central America.

Macrozooplankton predation impact on anchovy (Engraulis encrasicolus) eggs mortality at the Bay of Biscay shelf break spawning centre

Abstract A real-time PCR based method involving a species-specific probe was applied to detect Engraulis encrasicolus eggs predation by the macrozooplankton community during the 2011 spawning season. Three locations along the shelf break presenting contrasting but high prey densities were sampled. A total of 840 individuals from 38 taxa of potential macrozooplankton predators were assayed for E. encrasicolus DNA presence and 27 presented at least one positive signal. Carnivorous copepods were responsible for the most predation events (66%) followed by euphausiids (16%), chaetognaths (5%), and myctophid fish (4%). Macrozooplankton predation on anchovy eggs followed a type-I functional response with daily mortalities <4% of available prey abundance suggesting a negligible impact on the species recruitment at the shelf break spawning centre.