Nesting strategies and disease risk in necrophagous beetles

While the effects of carcass decomposition on microorganisms have been demonstrated in recent years, little is known of how this impacts necrophagous insects. A common assumption is that insects that exploit carcasses are exposed to a high density of potentially harmful microorganisms, but no field data have so far validated this. Necrophagous beetles such as the Scarabaeinae have complex nesting behaviors with elaborate parental care. So here, we begin to explore whether this conjunction of life history and nesting behavior represents an adaptive response to the threat posed by microbes in these environments, mainly by entomopathogens. We evaluated the density and distribution of fungi and bacteria from soil near the carcasses, and their ability to infect and kill insects that are in contact with this soil during the decomposition process. Our data showed an increase in the density and activity of opportunistic or facultative pathogens during the apex of decomposition, when there is a predominance of necrophagous insects. Meanwhile, the survivorship of bait insects decreased when in contact with soil from this period of decomposition, indicating a potential risk of infection. However, the density and activity of these microorganisms decreased with distance from the carcass, mainly with depth, which would benefit tunneller beetles in particular. We have thus provided the first field data to show that necrophagous insects are indeed exposed to high densities of potentially harmful microorganisms. Furthermore, we propose that some parental care strategies may have arisen not only as a response to competition, but also as adaptations that reduce the risks of disease. Although we have focused on carrion feeders, we suggest that the same occurs with coprophagous beetles, as both carrion and dung are nutrient‐rich resources.     

Cephalotes clypeatus Fabricius (Hymenoptera: Formicidae): nesting habits and occurrence in animal carcass

The ecological position of the family Formicidae in animal carcasses varies from predator, when feeding on eggs, larvae and pupae of some insects to necrophagous, when the ants feed on exudates or decomposing tissues. Ants are present in human corpses subject to forensic analyses and can also be used in estimation of the post-mortem interval (PMI). Cephalotes clypeatus Fabricius is exclusively arboricolous and occurs only in the American continent. During a field study conducted in the Campus of the Universidade Estadual de Campinas, in December 2003, a laboratory mouse carcass weighing 35,9 g was placed in an iron-mesh cage, which was adequate to collect adult ants. The carcass decomposed in four days. The total of 82 specimens of C. clypeatus was collected, in the first two days of exposure. They were observed feeding on exudates, tissues of the carcass, and on Diptera larvae occurring in the carcass. This species was observed nesting in hollow branches of Senna multijuga (Rich.) H.S. Irwin & Barneby (Caesalpinaceae), which was found one-meter far from the cage. Further investigation on the biology of this Cephalotini must be performed, in order to understand the role of this species in the utilization of animal carcasses, and in the entomological succession process as well. This is the first report of C. clypeatus in animal carcasses.     

Effects of carrion decomposition on litter arthropod assemblages

1. Many organisms contribute to the decomposition of carrion. For arthropods, many studies focus on the necrophagous community, those directly consuming carrion.
2. Necrophagous arthropods use carrion as a shelter or food source. Therefore, carrion generally increases the abundance and biodiversity of necrophagous species. However, it is unclear if carrion has similar effects on detrital communities.
3. This study examines changes in community structure and composition of necrophilous and detrital communities over the course of decomposition.
4. Five pig head carrion were placed at least 7 m apart under cages in temperate mixed forest. Leaf litter was sampled 0 m, 1.5 m, and 3 m from each carrion weekly during summer, and monthly during autumn, until the first frost. Arthropods were extracted from leaf litter by using Berlese funnels.
5. At the carrion site, necrophagous insects increased in abundance, species richness, and Shannon diversity during decomposition, and all decreased after dry decay.
6. Detritus arthropods displayed a sharp increase in abundance during advanced decay, decreasing during dry decay, and a general increase over time for species richness and diversity.
7. In conclusion, carrion can influence the surrounding, non-necrophagous arthropod community, highlighting the need to investigate carrion effects beyond typical necrophagous species to have a more holistic understanding of carrion ecology.

     

Diversity,Daily Flight Activity and Temporal Occurrence of Necrophagous Diptera Associated with Decomposing Carcasses in a Semi-Arid Environment

The harsh conditions of the Brazilian seasonally dry tropical forest known as Caatinga pose challenges to the insects specialized in the exploitation of ephemeral resources. We investigated the diversity and daily flight activity of dipterans associated with decomposing rat carcasses in a field experiment performed in the semi-arid region of Pernambuco State, Brazil. We also analyzed the temporal arrival of adult insects on the carcasses at three stages of decomposition: early, intermediate, and advanced. We collected 1173 individuals, of which Muscidae had the highest abundance (36.5%), followed by Sarcophagidae (28.1%), Calliphoridae (25.2%), and Fanniidae (10.2%). Chrysomya albiceps (Wiedemann, 1819) (Calliphoridae), Fannia pusio (Wiedemann, 1830) (Fanniidae), Atherigona orientalis (Schiner, 1868), and Musca domestica (Linnaeus, 1758) (Muscidae) were the most abundant species. The richness reached its maximum value on the second day of decomposition, with 18 species, decreasing to 8 species on the last day of decomposition (7 days). The ecological indices of diversity, dominance, and evenness varied little among the stages. There was an overlap of most species throughout the decomposition, although the overall abundance was higher at the intermediate stage for Calliphoridae, Muscidae, and Sarcophagidae. In accordance to previous studies, nocturnal flight was rare, as approximately 8% of insects were captured at night. Our results expand the knowledge on ecological and behavioral aspects of necrophagous flies under inhospitable environments, such as the dry season in the Caatinga. The dominance of the invasive species C. albiceps reinforced here illustrates its geographical expansion towards the countryside of Northeastern Brazil.     

Delaying insect access alters community composition on small carrion: a quantitative approach

We present a study of interactions in the highly competitive insect communities inhabiting the carrion of small mammals. Via manipulation in a fully quantitative design, we delayed community development by excluding insect colonization in mouse and rat carcasses for 3 days, to study the role of early competitively dominant colonizers [burying beetles (Nicrophorus spp.; Coleoptera: Silphidae) and blowfly larvae (Diptera: Calliphoridae)] in the course of heterotrophic succession on small cadavers. Earlier studies demonstrated that in the case of large mammalian carrion, exclusion of insects’ access to the carcass in the early stages of decomposition altered the successional trajectory and species assemblages. However, the effect of such manipulation in easy monopolizable small vertebrate carrion remained unknown. Our results demonstrate that delaying insect access to carrion significantly lowered blowfly larvae abundances, while it simultaneously had no effect on colonization and carrion burial by burying beetles. Higher abundances of blowfly larvae seem to deter necrophagous beetles, whereas they are not harmful to the larvae of flesh flies, at least in larger rat carcasses. Predatory beetle species preferred the lower abundances of blowfly larvae, presumably due to better accessibility of their prey. Our results therefore suggest that in the course of the entire season, larvae of blowflies are the dominant competitors in small carcasses, and significantly affect the assembly of other insect groups, whereas burying beetles may exhibit a more temporal pattern of dominance.     

Decomposition process for buried rat (Rattus norvegicus,Berkenhout 1769) carcasses in Riyadh city,Saudi Arabia: A preliminary study

The present report outlines the initial observations from an ongoing study examining the decomposition rate of buried rat (Rattus norvegicus, Berkenhout 1769) carcasses in Riyadh city, Saudi Arabia. Eight rat carcasses were buried in separate holes at depths of 20 and 40 cm (four holes per depth) to allow natural decomposition and examined at 10-day intervals up to 40 days. During the study period, environmental factors such as humidity, soil temperature, and air temperature were monitored at each depth on a daily basis. At the end of each burial period, one carcass from each depth was exhumed and the degree of decay and presence of insect activity were examined. The results showed that burial depth and temperature were major factors affecting the decomposition rate, whereas no insect activity was observed. The findings of this study can be used to more accurately estimate the time since burial of carcasses.     

Deer Carcass Decomposition and Potential Scavenger Exposure to Chronic Wasting Disease

ABSTRACT Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy afflicting the Cervidae family in North America, causing neurodegeneration and ultimately death. Although there are no reports of natural cross-species transmission of CWD to noncervids, infected deer carcasses pose a potential risk of CWD exposure for other animals. We placed 40 disease-free white-tailed deer (Odocoileus virginianus) carcasses and 10 gut piles in the CWD-affected area of Wisconsin (USA) from September to April in 2003 through 2005. We used photos from remotely operated cameras to characterize scavenger visitation and relative activity. To evaluate factors driving the rate of carcass removal (decomposition), we used Kaplan-Meier survival analysis and a generalized linear mixed model. We recorded 14 species of scavenging mammals (6 visiting species) and 14 species of scavenging birds (8 visiting species). Prominent scavengers included American crows (Corvus brachyrhynchos), raccoons (Procyon lotor), and Virginia opossums (Didelphis virginiana). We found no evidence that deer consumed conspecific remains, although they visited gut piles more often than carcasses relative to temporal availability in the environment. Domestic dogs, cats, and cows either scavenged or visited carcass sites, which could lead to human exposure to CWD. Deer carcasses persisted for 18 days to 101 days depending on the season and year, whereas gut piles lasted for 3 days. Habitat did not influence carcass decomposition, but mammalian and avian scavenger activity and higher temperatures were positively associated with faster removal. Infected deer carcasses or gut piles can serve as potential sources of CWD prions to a variety of scavengers. In areas where surveillance for CWD exposure is practical, management agencies should consider strategies for testing primary scavengers of deer carcass material.     

西安地区家兔尸体上尸食性昆虫的初步观察

置家兔尸体于室外空地进行观察,研究春季西安地区家兔尸体上昆虫群落的组成及演替规律。结果表明西安地区春季常见的尸食性的昆虫包括3目11科16种,其中双翅目的巨尾阿丽蝇Aldrichina grahami、鞘翅目一种阎甲Margarinotus sp.为优势种。尸体上昆虫群落的演替有明显的时间规律可循,昆虫类群的出现时间与尸体的腐败阶段有明确的对应关系,可以为法医科学中推测死亡时间提供依据。     

珠江三角洲猪尸体上昆虫群落的演替及其对法医学中死亡时间推断的指示意义

为了解决刑事案件中死者死亡时间推断的难题,不同季节野外环境用18头猪尸体做模拟材料观察和筛选对推断死亡时间高度准确的昆虫指标。结果表明,幼虫开始出现时间、幼虫开始爬离时间、大部分幼虫爬离尸体的时间、开始化蛹的时间、大部分幼虫化蛹的时间、开始羽化的时间、羽化结束的时间等若干昆虫指标比较敏感且稳定可用作死亡时间的精确推断。在珠江三角洲春季、夏季及秋季尸体腐败很快,分别在259±23,202±18,277±20 h进入白骨化期,而冬季则时间较长,约经过1 297±63 h才进入白骨化期。大约有47种嗜尸性昆虫在尸体生态环境出现,大多数种类全年可见,尸体上的昆虫群落的优势种为大头金蝇Chrysomya megacephala、绯颜裸金蝇Achoetandrus rufifacies及厚环黑蝇Hydrotaea (Ophyra) spinigera。蝇类昆虫在尸体上只能大规模繁殖一代尸体即白骨化。根据以上结果可确定一些可用于死亡时间推断的关键时间点。     

Foraging risk in scavenging ecology: A study of scavenger behavior and patterns of bacterial growth

Scavenging constitutes an understudied energy pathway in terrestrial ecosystems, with important connections to disease ecology. A prevailing null hypothesis in scavenging ecology is that carcasses serve as a risk-free meal for whatever animal first encounters them on the landscape. We tested this hypothesis by focusing on a suspected risk that scavengers would face at carcasses: the risk of pathogen exposure. We conducted field trials with mouse carcasses in which we manipulated potential cues to pathogen risk and then monitored scavenger foraging decisions. Separately, we studied pathogen and commensal bacteria dynamics within mouse carcasses through time in the laboratory to better understand how carcass age might impact pathogen risk to scavengers. A visual cue to pathogen risk in the field (carcasses deployed in groups of 7 in 1 m²) caused facultative vertebrate scavengers to pass on the opportunity to feed at a rate six-times higher than for carcasses deployed singly (46.9% vs. 7.7%), suggesting an ability to perceive cues to pathogen risk at carcasses. The cues to carcass age, however, produced no effect on facultative scavenger behavior in our field trials. Laboratory trials demonstrated that both commensal enteric bacteria and a known pathogen (Listeria monocytogenes) increased at least through bloat and active decay stages in carcasses, suggesting that cues to carcass age may not help scavengers reduce pathogen risk early in decomposition. In providing evidence counter to the free meal hypothesis, our results support the continued formation of an alternative risk-based framework to understand scavenger behavior at carcasses.     

Methods and models to determine perinatal status of Florida manatee carcasses

Differences in perinatal mortality can be indicators of differences in physiology, behavior, toxicology, population dynamics, and ecology of species and individuals. Extensive data collected under the Florida Manatee Carcass Recovery Program provide important information about manatee perinatal mortality. However, early age at death can be difficult to determine for often highly decomposed carcasses. Here, I provide quantitative methods to identify perinatal status for manatee carcasses. First, perinatal and nonperinatal mortality were defined based on physiological indicators. After review of necropsy reports, specific length classes became clear indicators of perinatal status: carcasses <82‐cm long were always perinatal, and carcasses >160‐cm long were always nonperinatal. Using data from carcasses 82–160 cm long of known perinatal status, Bayesian models quantify the relationship among age at death, carcass length, and carcass recovery month. The models predict the perinatal status of carcass 82–160 cm long when physiological indicators are unavailable. Overall, perinatal status could be determined for 98.2% of carcasses collected from 1978 to 2005. Initial examination of the fraction of perinatal mortalities within the entire carcass sample reveals interesting spatial and temporal patterns that warrant further analyses.     

Effects of decomposition on carcass attendance in a guild of carrion-breeding flies

Many forensically important calliphorids, sarcophagids and muscids (Diptera) oviposit or larviposit on corpses only during the early stages of decomposition, yet individuals may attend bodies throughout decay. A field study was conducted to investigate how patterns of carcass use and attendance by some fly species are affected by decomposition. Five fly traps were placed in the forest and baited with whole, fresh piglet carcasses. Piglets decomposed in traps throughout the experiment, and all were skeletonized within 6 days. Flies were trapped at both early and late decomposition stages, and the species and population structures of trap catches were compared. More flies attended carcasses early rather than late in decay. For all species, flies attending early were mainly gravid females, but few gravid females attended late in decay. No females ovi- or larviposited late in decay, whereas females of all fly species deposited offspring early in decay. The number of males trapped of each species correlated positively with the number of females with eggs at early development stages. Observations were made of fly predation by European wasps Vespula germanica Fabricius (Hymenoptera, Vespidae) and jumper ants Myrmecia pilosula Smith (Hymenoptera, Formicidae) throughout the experiment. There was a higher risk for smaller fly species of being killed following predator attack. Ants and wasps attacked smaller fly species, whereas only wasps attacked larger fly species.     

Blowflies (Diptera: Calliphoridae) activity in sun exposed and shaded carrion in Portugal

The first forensic entomological study performed in Portugal is presented. Two piglet (Sus scrofa L.) carcasses were used to determine adult Calliphoridae activity on carrion over a period of 121 days, all along the end of spring and the summer, both in a shaded and a sunny site. Five decomposition stages were observed and a total of 10723 adult Calliphoridae, belonging to 11 species, were collected. Calliphora vicina, Calliphora vomitoria, Chrysomya albiceps and Lucilia caesar were the dominant species in this study. Decomposition was faster on the carcass exposed to the sun and the number of Calliphoridae specimens was higher there than in the shaded site. It was found a significant effect of the decomposition stage in the number of specimens attracted to the carcass, as well as a significant effect of the interaction between the decomposition stage and insolation regime. Calliphora and Lucilia species did not show preference for sunny or shaded areas. Important differences in the Calliphoridae community structure were found compared to other regions of the Iberian Peninsula, reinforcing the need of further studies in different environments and regions of this geographical area in order to collect information about the local necrophagous fauna used in forensic practice.     

The attraction of virgin female hide beetles (Dermestes maculatus) to cadavers by a combination of decomposition odour and male sex pheromones

ABSTRACT: INTRODUCTION: The hide beetle Dermestes maculatus (Coleoptera: Dermestidae) feeds as an adult and larva on decomposing animal remains and can also be found on human corpses. Therefore, forensic entomological questions with regard to when and how the first receptive females appear on carcasses are important, as the developmental stages of their larvae can be used to calculate the post-mortem interval. To date, we know that freshly emerged males respond to the cadaver odour of post-bloated carcasses (approximately 9 days after death at Tmean = 27degrees), being attracted by benzyl butyrate. This component occurs at its highest concentration at this stage of decay. The aim of our study was to determine the principle of attraction of virgin females to the feeding and breeding substrate. For this purpose, we tested the response of these females to headspace samples of piglet cadavers and male sex pheromones [(Z9)-unsaturated fatty acid isopropyl esters] in a Y-olfactometer. Because we expected that such an odour combination is of importance for virgin female attraction, we tested the following two questions: 1) Are virgin female hide beetles attracted by a combination of cadaver odour and male sex pheromones? 2) During which decomposition stage do the first virgin females respond to cadaver odour when combined with male sex pheromones? RESULTS: We found that young virgin females were attracted to the cadaver by a combination of cadaver odour and male sex pheromones. Neither cadaver odour alone nor male sex pheromones alone was significantly more attractive than a solvent control. Our results also gave a weak indication that the first young virgin females respond as early as the post-bloating stage to its associated decomposition odour when combined with male sex pheromones. CONCLUSIONS: Our results indicate that freshly emerged males possibly respond to cadaver odour and visit carcasses before virgin females. Being attracted to cadavers when male sex pheromone is perceived as well, virgin females can optimise their reproductive possibilities.     

Mass loss and macroinvertebrate colonisation of Pacific salmon carcasses in south-eastern Alaskan streams

1. We examined the spatial and temporal dynamics of pink salmon ( Oncorhynchus gorbuscha ) carcass decomposition (mass loss and macroinvertebrate colonisation) in south-eastern Alaskan streams. Dry mass and macroinvertebrate fauna of carcasses placed in streams were measured every two weeks over two months in six artificial streams and once after six weeks in four natural streams. We also surveyed the macroinvertebrate fauna and wet mass of naturally occurring salmon carcasses.
2. Carcass mass loss in artificial streams was initially rapid and then declined over time ( k =–0.033 day^–1), and no significant differences were found among natural streams.
3. Several macroinvertebrate taxa colonised carcasses, but chironomid midge (Diptera: Chironomidae) and Zapada (Plecoptera: Nemouridae) larvae were found consistently and were the most abundant (on average 95 and 2%, respectively, of the invertebrates found). Chironomid abundance and biomass increased over time, whereas Zapada abundance and biomass did not. Significant differences in abundance were found among natural streams for Baetis (Ephemeroptera: Baetidae) and Sweltsa (Plecoptera: Chloroperlidae) larvae, while no significant differences were found for chironomid and Zapada abundance or biomass.
4. Our results suggest that salmon carcasses initially undergo a high rate of mass loss that tapers off with time. Chironomid and Zapada larvae are likely to be important in mediating nutrient and energy transfer between salmon carcasses and other components of the freshwater-riparian food web in south-eastern Alaskan streams.     

Effect of investigator disturbance in experimental forensic entomology: succession and community composition

Carrion insect succession studies have historically used repeated sampling of single or a few carcasses to produce data, either weighing the carcasses, removing a qualitative subsample of the fauna present, or both, on every visit over the course of decomposition and succession. This study, conducted in a set of related experimental hypotheses with two trials in a single season, investigated the effect that repeated sampling has on insect succession, determined by the number of taxa collected on each visit and by community composition. Each trial lasted at least 21 days, with daily visits on the first 14 days. Rat carcasses used in this study were all placed in the field on the same day, but then either sampled qualitatively on every visit (similar to most succession studies) or ignored until a given day of succession, when they were sampled qualitatively (a subsample) and then destructively sampled in their entirety. Carcasses sampled on every visit were in two groups: those from which only a sample of the fauna was taken and those from which a sample of fauna was taken and the carcass was weighed for biomass determination. Of the carcasses visited only once, the number of taxa in subsamples was compared to the actual number of taxa present when the carcass was destructively sampled to determine if the subsamples adequately represented the total carcass fauna. Data from the qualitative subsamples of those carcasses visited only once were also compared to data collected from carcasses that were sampled on every visit to investigate the effect of the repeated sampling. A total of 39 taxa were collected from carcasses during the study and the component taxa are discussed individually in relation to their role in succession. Number of taxa differed on only one visit between the qualitative subsamples and the actual number of taxa present, primarily because the organisms missed by the qualitative sampling were cryptic (hidden deep within body cavities) or rare (only represented by very few specimens). There were no differences discovered between number of taxa in qualitative subsamples from carcasses sampled repeatedly (with or without biomass determinations) and those sampled only a single time. Community composition differed considerably in later stages of decomposition, with disparate communities due primarily to small numbers of rare taxa. These results indicate that the methods used historically for community composition determination in experimental forensic entomology are generally adequate.     

Tissue sterility in uneviscerated carcasses.

Sheep muscle tissue removed aseptically from control carcasses, from uneviscerated carcasses held at 20 degrees C for 24 h, and from carcasses of sheep subjected to stress before slaughter was examined for the presence of bacteria. All samples from a total of 68 carcasses were sterile. Whole-body autoradiography of mouse carcasses showed that 14C-labeled fixed bacteria injected after death remained in the lumen of the intestine. Live bacteria did not penetrate the mucosal surface until the tissue structure had been disrupted by proteolytic enzymes. Bacteria were unable to penetrate sections of intestine longitudinally until considerable structural breakdown had occurred, indicating that blood and lymph vessels do not normally offer a pathway for microbial invasion from the intestine. Clostridia, which have been reported to be responsible for deep spoilage of meat, reached maximum numbers 24 to 28 h after death in the intestines of guinea pig carcasses stored at 20 degrees C, but did not invade carcass tissues until the stomach ruptured as a result of proteolysis between 2 and 3 days after death.     

Tissue sterility in uneviscerated carcasses.

Sheep muscle tissue removed aseptically from control carcasses, from uneviscerated carcasses held at 20 degrees C for 24 h, and from carcasses of sheep subjected to stress before slaughter was examined for the presence of bacteria. All samples from a total of 68 carcasses were sterile. Whole-body autoradiography of mouse carcasses showed that 14C-labeled fixed bacteria injected after death remained in the lumen of the intestine. Live bacteria did not penetrate the mucosal surface until the tissue structure had been disrupted by proteolytic enzymes. Bacteria were unable to penetrate sections of intestine longitudinally until considerable structural breakdown had occurred, indicating that blood and lymph vessels do not normally offer a pathway for microbial invasion from the intestine. Clostridia, which have been reported to be responsible for deep spoilage of meat, reached maximum numbers 24 to 28 h after death in the intestines of guinea pig carcasses stored at 20 degrees C, but did not invade carcass tissues until the stomach ruptured as a result of proteolysis between 2 and 3 days after death.     

A checklist of arthropods associated with pig carrion and human corpses in southeastern brazil

Necrophagous insects, mainly Diptera and Coleoptera, are attracted to specific stages of carcass decomposition, in a process of faunistic succession. They are very important in estimating the postmortem interval, the time interval between the death and the discovery of the body. In studies done with pig carcasses exposed to natural conditions in an urban forest (Santa Genebra Reservation), located in Campinas, State of S?o Paulo, southeastern Brazil, 4 out of 36 families of insects collected - Calliphoridae, Sarcophagidae, Muscidae (Diptera) and Dermestidae (Coleoptera) - were considered of forensic importance, because several species were collected in large numbers both visiting and breeding in pig carcasses. Several species were also observed and collected on human corpses at the Institute of Legal Medicine. The species belonged to 17 different families, 6 being of forensic importance because they were reared from human corpses or pig carcasses: Calliphoridae, Sarcophagidae, Muscidae, Piophilidae (Diptera), Dermestidae, Silphidae and Cleridae (Coleoptera). The most important species were: Diptera - Chrysomya albiceps, Chrysomya putoria, Hemilucilia segmentaria, Hemilucilia semidiaphana (Calliphoridae), Pattonella intermutans (Sarcophagidae), Ophyra chalcogaster (Muscidae), Piophila casei (Piophilidae); Coleoptera - Dermestes maculatus (Dermestidae), Oxyletrum disciolle (Silphidae) and Necrobia rufipes (Cleridae).     

Do fall additions of salmon carcasses benefit food webs in experimental streams?

Research showing that salmon carcasses support the productivity and biodiversity of aquatic and riparian ecosystems has been conducted over a variety of spatial and temporal scales. In some studies, carcasses were manipulated in a single pulse or loading rate or manipulations occurred during summer and early fall, rather than simulating the natural dynamic of an extended spawning period, a gradient of loading rates, or testing carcass effects in late fall-early winter when some salmon stocks in the US Pacific Northwest spawn. To address these discrepancies, we manipulated salmon carcass biomass in 16 experimental channels located in the sunlit floodplain of the Cedar River, WA, USA between mid-September and mid-December, 2006. Total carcass loads ranged from 0?C4.0 kg/m² (0, 0.001, 0.01, 0.1, 0.5, 1.0, 2.0 and 4.0 kg/m², n = 2 per treatment) and were added to mimic the temporal dynamic of an extended spawning period. We found little evidence that carcasses influenced primary producer biomass or fish growth; however, nutrients and some primary consumer populations increased with loading rate. These effects varied through time, however. We hypothesize that the variable effects of carcasses were a result of ambient abiotic condition, such as light, temperature and disturbance that constrained trophic response. There was some evidence to suggest peak responses for primary producers and consumers occurred at a loading rate of ~1.0?C2.0 kg/m², which was similar to other experimental studies conducted during summer.