δ15N Stable Isotope Analysis Research Articles

Intraspecific differences in relative isotopic niche area and overlap of co-occurring sharks

Few studies have assessed whether patterns of resource partitioning among sympatric marine predators vary between different habitats. This type of data is important for understanding food web functioning as well as for supporting an ecosystem-based fisheries management plan. In this study, we used δ13C and δ15N stable isotope analysis to assess the relative isotopic niche area (i.e., which species has the largest and smallest isotopic niche area within a study site) and core isotopic niche overlap between 299 sharks of 11 co-occurring shark species that vary in size, diet and behavior in three coastal study areas in South Florida. Overall, results show that the relative isotopic niche area and patterns of core isotopic niche overlap between some sympatric shark species varied between sites, suggesting plasticity in resource use and competitive interactions between shark species (e.g., 85% of blacktip shark Carcharhinus limbatus standard ellipse area overlapped with the blacknose shark C. acronotus ellipse in Biscayne Bay, but there was no overlap between these species’ ellipses in nearby Florida Bay). Therefore, patterns of resource use and trophic interactions documented among species from one site may not be applicable to a neighboring location. These findings may have implications for food web models that incorporate trophic data from different areas for a species when local data are unavailable.

The diet and feeding rates of gastropod grazers in Singapore’s seagrass meadows

AbstractA wide variety of organisms are known to graze on seagrasses and their associated epiphytes, and this plant-animal interaction can affect the health of seagrass meadows. Grazing patterns tend to vary across meadows and faunal groups, and little is known regarding how gastropod grazers influence meadows in the tropics. To better understand this interaction, we surveyed the gastropod diversity in five meadows in Singapore. Further, grazing potential (i.e. potential food sources and feeding rates) of common gastropod species was quantified throughex situgrazing experiments, while their diet compositions were elucidated using dual δ13C and δ15N stable isotope analyses. The surveys revealed a high diversity of 274 gastropod species/morphospecies while PERMANOVA and SIMPER analyses showed that communities differed significantly among sites but not among seagrass species. Diet composition analysis indicated that seagrass leaves were the main food source for most gastropod species examined while epiphytes were important for microsnail (shell size <5 mm) species. However, all the gastropod species tested fed on epiphytes in theex situexperiments. These findings contribute new insights into grazing by marine gastropods on tropical seagrass meadows, and highlight the potential importance of both direct grazing and epiphyte removal on tropical meadows.

莱州湾鱼类群落优势种生态位

PDF HTML阅读 XML下载 导出引用 引用提醒 莱州湾鱼类群落优势种生态位 DOI: 10.5846/stxb201408281711 作者: 作者单位: 山东省海洋资源与环境研究院,山东省海洋资源与环境研究院,山东省海洋资源与环境研究院,烟台市水产研究所 作者简介: 通讯作者: 中图分类号: S931.1 基金项目: 山东省渔业资源增殖效果评价（SD-XGPJ-2012-2）；山东省优秀中青年科学家科研奖励基金（BS2012HZ030） Ecological niche of dominant species of fish assemblages in Laizhou Bay, China Author: Affiliation: Shandong Marine Resource and Environment Research Institute,Shandong Provincial Key Laboratory of Restoration for Marine Ecology,Shandong Marine Resource and Environment Research Institute,Shandong Provincial Key Laboratory of Restoration for Marine Ecology,Shandong Marine Resource and Environment Research Institute,Shandong Provincial Key Laboratory of Restoration for Marine Ecology,Yantai Fisheries Research Institute 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:根据2011年5月、8月、10月和12月莱州湾底拖网调查资料，对该海域鱼类群落优势种的生态位进行了研究。结果表明，全年调查共捕获鱼类49种，各季节优势种种类数分别为春季3种，夏季5种，秋季3种，冬季4种。夏、冬季优势种的丛生指数较低，春、秋季较高；冬、春季优势种的平均拥挤度较低，夏、秋季较高。基于欧氏距离的优势种丰度聚类结果同优势度排序结果吻合。主成分分析（PCA）表明，青鳞小沙丁鱼（Sardinella zunasi）和赤鼻棱鳀（Thryssa kammalensis）分别是影响第一轴和第二轴的主要种类。绯鱼衔（Callionymus beniteguri）、鲬（Platycephalus indicus）、髭缟虾虎鱼（Tridentiger barbatus）和短吻红舌鳎（Cynoglossus joyneri）是时空二维生态位宽度最高的种类（>2）。时空生态位显著重叠（>0.6）的种类有7组，其中银姑鱼（Pennahia argentata）和皮氏叫姑鱼（Johnius belengerii）重叠值最高（0.798）。δ13C值变幅（CR）最大的种类为斑鱼祭（Konosirus punctatus），δ15N值变幅（NR）最大的种类为青鳞小沙丁鱼；青鳞小沙丁鱼和鱼祭生态位总面积超过20，皮氏叫姑鱼生态位总面积最小（1.38）且与其他优势种营养生态位重叠较高。等级聚类、排序、PCA和优势种排序结果较一致，而与时空生态位宽度分析结果差异较大，表明莱州湾鱼类群落结构受洄游鱼类的影响较大。时空生态位宽度较高的种类主要为集群特征不明显的周年定居种（绯鱼衔、鲬、短吻红舌鳎等底层鱼类），而季节洄游种（青鳞小沙丁鱼、鱼祭、赤鼻棱鳀等中上层鱼类）因时间生态位宽度较低导致时空生态位宽度较低。时空生态位和营养生态位分析表明，生态位重叠导致的资源利用性竞争并不是导致莱州湾鱼类群落结构现状的决定性因素，而更多可能是人为干扰形成的。 Abstract:Laizhou Bay, an estuary of the Yellow River, is one of the three most important bays of the Bohai Sea, China. It is characterized by a high level of primary productivity and is one of the most important spawning and feeding grounds for most fish species in the Yellow Sea and Bohai Sea. After decades of overfishing, the dominant species of the fish assemblage have been altered. Ecological niche describes how an organism or population responds to the distribution of resources. Therefore, studies on ecological niches are extremely important to clarify the ecological dynamics of different species and the mechanism of interspecific coexistence and competition, as they are a fundamental tool for the conservation and assessment of fish stocks, as well as for the analysis of the ecosystem as a whole. Data were obtained from a bottom trawl survey conducted in Laizhou Bay (119°05'-120°00'E, 37°12'-37°40'N) in 2011. The most dominant species that contributed to 97.2% of biomass and 98.4% of abundance were used for the hierarchical cluster analysis, non-metric multidimensional scaling (NMDS), principal component analysis (PCA), and spatio-temporal niche analysis. Tissue samples were collected from the 12 most dominant species recorded in the trawl-survey catches. δ13C and δ15N stable-isotope analyses were performed to assess the trophic niche. A total of 49 fishes were collected. The assemblage density of dominant species was low in the summer and winter and high in the spring and autumn. The mean crowding of the dominant species was low in the spring and winter, and high in the summer and autumn. The results of the hierarchical cluster analysis based on the Euclidean distance showed a similarity with the results of the ecological dominance analysis. The PCA showed that Sardinella zunasi was one of the species that mostly affected the first axis, and Thryssa kammalensis mostly affected the second axis. Callionymus beniteguri had the highest value of tempo-spatial niche width, followed by Platycephalus indicus, Tridentiger barbatus, and Cynoglossus joyneri. Significant overlap of spatio-temporal niche occurred between the seven groups:Pennahia argentata vs. Setipinna taty (0.798), S. taty vs. Johnius belangerii (0.793), C. joyneri vs. J. belangerii (0.771), Chaeturichthys stigmatias vs. J. belangerii (0.770), Konosirus punctatus vs. Scomberomorus niphonius (0.763), and K. punctatus vs. C. joyneri (0.625). Konosirus punctatus had the highest δ13C range (CR=9.2), and J. belangerii had the highest δ15N range (NR=7.1). The total area (TA) of the trophic niche of S. zunasi and K. punctatus were the highest, both being larger than 20. Johnius belangerii had the lowest TA (1.38); however, it had a significant overlap with other species, such as C. stigmatias, C. joyneri, and P. argentata. The results showed a similar trend with cluster analysis, NMDS, and PCA; however, the trend was different with the tempo-spatial niche analysis. The non-migration species, which lives throughout year in the bay, with lower assemblage densities had a higher value of spatio-temporal niche width. The seasonal migratory species had a lower tempo-spatial niche width because of the low temporal niche width. The high spatio-temporal niche overlap between the most dominant species found in this study also reflected a high degree of homogeneity of fish assemblies in the Laizhou Bay. Competition owing to niche overlap was not the decisive factor that formed the community structure of nekton in the Laizhou Bay. The community structures might be most affected by anthropogenic activities. 参考文献 相似文献 引证文献

Are long-term fish assemblage changes in a large US river related to the Asian Carp invasion? Test of the hostile take-over and opportunistic dispersal hypotheses

Gizzard shad is a dominant planktivore/detritivore in the Wabash River, and populations crashed in the early 1990s. Previous work (1974–2008) identified a substantial shift in body-size structure and functional trait composition in the Wabash River fish assemblage between 1989 and 1996. Invasive Asian Carp appeared in the Ohio River basin including the Wabash River in the 1990s. Our goal was to test for temporal changes in assemblage composition and trophic structure relative to the invasion of Asian carp from the early 1990s. We hypothesized that establishment of Asian Carp was a contributor to the assemblage composition shift, and that their presence altered the trophic pathways and food sources of native fishes including Gizzard Shad (hostile takeover hypothesis). Alternatively, Asian Carp may have found success through capitalizing on an empty niche, likely left vacant by the decline in Gizzard Shad, or abundance changes in other trophic groups (opportunistic hypothesis). We utilized archival fish and mussel collections to test for trophic changes in the ecosystem using δ13C and δ15N stable isotope analyses. We examined stomach contents of the dominant planktivore/detritivore consumer, Gizzard Shad, from archival and recent collections to test for changes in the phytoplankton community. Stable isotopes indicated a community reliance on other, more deplete, carbon sources than indicated by the algae, and a slight increase between the δ13C time periods. Although all functional feeding groups of fishes indicated some reduction in δ15N, the differences were only significant for omnivores, mussels, and planktivore/detritivores. Although Asian Carp may have contributed to the collapse of Gizzard Shad populations, other stressors were likely more important drivers of their decline. This is the first, albeit indirect, evidence of opportunistic “invasion” as opposed to the historically presumed hostile takeover model.

Lake whitefish ( Coregonus clupeaformis ) energy and nutrient partitioning in lakes Michigan, Erie and Superior

A concurrent decrease in lake whitefish (Coregonus clupeaformis) condition and Diporeia spp. abundance in Lake Michigan has spurred investigations into possible links between the two phenomena. We examined female lake whitefish δ13C and δ15N stable isotopes, growth, reproductive investment, dorsal muscle total lipid and docosahexaenoic acid (DHA) contents from lakes Erie, Michigan and Superior to determine whether differences in food source were correlated with measures of stock success. Stocks with higher somatic growth rates and mean reproductive potential had higher energy stores in terms of percent total lipid. Stocks with low muscle lipid concentration also had smaller egg sizes as egg number increased. Diet varied among stocks as evidenced by δ13C and δ15N stable isotope analyses; however, muscle total lipid and DHA were not correlated to apparent Diporeia spp. prey use. When compared to stocks from lakes Erie and Superior, Lake Michigan stocks had lower growth, reproduction, and lipid stores. While stocks in Lake Michigan with access to declining Diporeia spp. populations may still feed on the amphipod, it appears that they are unable to consume the quantities necessary to maintain historical growth and reproduction. Stable isotope analyses of lakes Erie and Superior stocks, with higher growth rates and lipid values, indicated different feeding strategies with no indication of reliance on Diporeia spp. While differences in prey resources may have an effect on lake whitefish stocks, differences in Diporeia spp. abundance alone cannot explain differences in lake whitefish condition observed among the Great Lakes included in this study.

Foraging choices of vampire bats in diverse landscapes: potential implications for land-use change and disease transmission.

Summary In Latin America, the common vampire bat Desmodus rotundus is the primary reservoir of rabies, a zoonotic virus that kills thousands of livestock annually and causes sporadic and lethal human rabies outbreaks. The proliferation of livestock provides an abundant food resource for this obligate blood‐feeding species that could alter its foraging behaviour and rabies transmission, but poor understanding of the dietary plasticity of vampire bats limits understanding of how livestock influences rabies risk.We analysed individual‐ and population‐level foraging behaviour by applying δ13C and δ15N stable isotope analysis to hair samples from 183 vampire bats captured from nine colonies in Peru. We also assessed the isotopic distributions of realized prey by analysing blood meals extracted from engorged bats and samples collected from potential prey species. In two adjacent but contrasting areas of the Amazon with scarce and abundant livestock, we used questionnaires to evaluate the incidence of feeding on humans.Population‐level isotopic signatures suggested substantial among‐site variation in feeding behaviour, including reliance on livestock in some colonies and feeding on combinations of domestic and wild prey in others. Isotopic heterogeneity within bat colonies was among the largest recorded in vertebrate populations, indicating that individuals consistently fed on distinct prey resources and across distinct trophic levels. In some sites, isotopic values of realized prey spanned broad ranges, suggesting that bats with intermediate isotopic values could plausibly be dietary specialists rather than generalists.Bayesian estimates of isotopic niche width varied up to ninefold among colonies and were maximized where wildlife and livestock were present at low levels, but declined with greater availability of livestock. In the Amazon, the absence of livestock was associated with feeding on humans and wildlife. Policy implications. We provide the first insights into the foraging behaviour of vampire bats in habitats with common depredation on humans and show how vampire bat foraging may respond to land‐use change. Our results demonstrate risks of rabies transmission from bats to other wildlife and are consistent with the hypothesis that introducing livestock might reduce the burden of human rabies in high‐risk communities.

Evidence of nutrient partitioning in coexisting deep-sea echinoids, and seasonal dietary shifts in seasonal breeders: Perspectives from stable isotope analyses

The role of nutrition in echinoid growth and reproduction, as well as the mechanisms utilized to cope with food limitations in the deep sea remains under studied. We investigate echinoid feeding mechanisms within deep-sea submarine canyons in the NE Atlantic using a stable-isotope approach. Ten echinoid species were collected with a remotely operated vehicle. δ13C and δ15N stable isotope analyses (SIA) were conducted on echinoid tissues in order to investigate food sources assimilated with respect to nutrient partitioning between coexisting taxa, and seasonal dietary changes in food supply. Gut content analysis was conducted in conjunction with SIA.Echinoid taxa spanned three benthic trophic levels. This large trophic range might suggest an expansion of the trophic niches of echinoid taxa possibly to reduce interspecific competition for limited food resources. Evidence of nutrient partitioning among coexisting taxa was also found in the carbon data. Significant interspecific differences were found in the δ13C signatures of the somatic and reproductive tissues suggesting that different sources of carbon are assimilated into all tissues after the deposition of phytodetritus has taken place on the deep sea floor. However, this pattern differed for the data obtained before the deposition of phytodetritus; similar sources of carbon were assimilated into somatic tissues of different taxa, while some of these different taxa utilized significantly different sources of carbon to manufacture their reproductive tissues.While specific food sources could not be resolved from the carbon data of the present study, enriched δ15N values suggest that echinoids incorporate foods with distinctly higher δ15N values than that of POM and sediment, which could result from opportunistic feeding as well as bioerosion of the live coral framework and consequent grazing of fauna attached to the dead coral infrastructure.Seasonally deposited phytodetritus was incorporated into the reproductive tissues of the seasonal breeder, Gracilechinus alexandri, but not those of continuous breeders, Cidaroida and Echinothurioida. The material however was also found to support somatic tissue growth in cidaroids. These results suggest that seasonal breeders might utilize surface-derived phytodetritus to manufacture reproductive tissues, while continuous breeders might only utilize it for somatic tissue growth or not at all. Results for seasonal dietary shifts were compromised by poor spatial repeatability and thus require further investigation to understand better the role of phytodetritus in fuelling the growth and reproduction of deep-sea echinoids.

Benthic Trophic Interactions in an Antarctic Shallow Water Ecosystem Affected by Recent Glacier Retreat.

The western Antarctic Peninsula is experiencing strong environmental changes as a consequence of ongoing regional warming. Glaciers in the area are retreating rapidly and increased sediment-laden meltwater runoff threatens the benthic biodiversity at shallow depths. We identified three sites with a distinct glacier-retreat related history and different levels of glacial influence in the inner part of Potter Cove (King George Island, South Shetland Islands), a fjord-like embayment impacted since the 1950s by a tidewater glacier retreat. We compared the soft sediment meio- and macrofauna isotopic niche widths (δ13C and δ15N stable isotope analysis) at the three sites to investigate possible glacier retreat-related influences on benthic trophic interactions. The isotopic niches were locally shaped by the different degrees of glacier retreat-related disturbance within the Cove. Wider isotopic niche widths were found at the site that has become ice-free most recently, and narrower niches at the older ice-free sites. At an intermediate state of glacier retreat-related disturbance (e.g. via ice-growler scouring) species with different strategies could settle. The site at the earliest stage of post-retreat development was characterized by an assemblage with lower trophic redundancy. Generally, the isotopic niche widths increased with increasing size spectra of organisms within the community, excepting the youngest assemblage, where the pioneer colonizer meiofauna size class displayed the highest isotopic niche width. Meiofauna at all sites generally occupied positions in the isotopic space that suggested a detrital-pool food source and/or the presence of predatory taxa. In general ice scour and glacial impact appeared to play a two-fold role within the Cove: i) either stimulating trophic diversity by allowing continuous re-colonization of meiofaunal species or, ii) over time driving the benthic assemblages into a more compact trophic structure with increased connectedness and resource recycling.

Traceability of organic fish – Authenticating the production origin of salmonids by chemical and isotopic analyses

To develop a practical methodology for the authentication of organic salmonid products, 130 fillet samples of trout and salmon originating from organic and conventional aquaculture as well as wild stocks (salmon) were collected from the German market over one year. Combined stable isotope analysis of δ15N and δ13C in defatted dry matter allowed differentiation of organically farmed from conventionally farmed salmon and brown trout, whether raw, smoked or graved. For the additional distinction of organic and wild salmon, a second analysis of δ13C in fish lipids was required. Fatty acid analysis completely differentiated the three production types of salmon just by the linoleic acid content in the fish lipids, which was lowest in wild and highest in conventional salmon. Moreover, the elevated myristic acid content allowed organic to be distinguished from wild and conventional salmon. Furthermore, organic and conventional brown trout could be distinguished by combining the oleic acid and gondoic acid contents. Analysis of the free astaxanthin isomeric pattern allowed a clear distinction of conventional and wild salmon, but organic salmon showed variable patterns that did not consistently allow the authentication of their origin. While a special feed composition is required in organic aquaculture, the composition of conventional aquaculture feed has changed considerably within the last decade. Consequently, the percentages of animal and vegetable components, which clearly vary between the production types, result in distinctive features in terms of stable isotope or fatty acid composition that are utilisable for the authentication of organic salmonid products. To account for potential changes in aquaculture feeding practices, the established distinctive limits should be traced and possibly adapted in future.

Ornithogenic soils and the paleoecology of pygoscelid penguins in Antarctica

Ornithogenic or bird-formed soils have accumulated in many coastal regions around Antarctica as a result of breeding activities by pygoscelid penguins, especially the Adélie penguin (Pygoscelis adeliae). These soils are often deep, range from hundreds to thousands of years old, and contain a natural archive of penguin tissues and those of their prey. In some regions, these tissues are extremely well preserved by the dry, cold environment and include complete and partial penguin mummies, feathers, bone, and eggshell. Hard parts of prey (fish bones, otoliths, and squid beaks) also commonly occur in these deposits from the penguin guano as it accumulates during soil development. Here, we review how research on these soils and the tissues they contain has progressed since they were first identified and described. These studies have provided not only valuable information on penguin occupation history with climate change since the Pleistocene, but also whole ecosystem responses to perturbations such as the ‘krill surplus’ that is hypothesized to have occurred following historic depletion of seals and whales in the 18th–20th centuries. New findings in the Ross Sea indicate how penguin occupation and abandonment cycles have progressed over millennia in relation to climate change. In addition, stable isotope analysis of δ15N and δ13C in ancient and modern Adélie penguin tissues (feathers, bone, eggshell and membrane) and guano support the ‘krill surplus’ hypothesis in showing a dietary shift from fish to krill over the past ∼200 years. Other recent studies have focused on stable isotope analyses of penguin prey remains, as well as ancient DNA and mercury analyses of penguin tissues recovered from ornithogenic soils. An analysis of fish otoliths recovered from ancient guano provide a means to investigate values of otolith carbonate δ18O, which correlates with other paleoclimatic records, and can be used as a proxy for changing ocean temperatures through time. In addition, measurements of total mercury (Hg) in penguin egg membrane from abandoned colonies up to 800 years old indicate significantly higher mercury levels in the past compared to modern penguins, likely due to a greater reliance on higher trophic prey prior to the proposed ‘krill surplus’. All of these studies indicate that ornithogenic soils and the natural archive of tissues they contain provide a unique means to integrate both terrestrial and marine records with ecosystem studies and climate change, past and present, in Antarctica.

Dietary segregation between two cohabiting species of sparrows revealed with stable isotope analysis

Fox Sparrows (Passerella iliaca (Merrem, 1786)) and Song Sparrows (Melospiza melodia (A. Wilson, 1810)) cohabit on many islands along the Pacific coast of North America, and previous studies suggest that they rely on similar prey types. We used δ13C and δ15N stable isotope analysis on blood collected from breeding adults of both species in each of two habitats on Triangle Island, British Columbia, Canada, to test the hypothesis that the two species exhibit a consistent pattern (direction) of dietary segregation in different habitat types. Both δ13C and especially δ15N values differed between habitats, indicating that the two habitats were isotopically distinct. As predicted, δ15N values differed consistently between the two species in the two habitats, averaging ∼1.5‰ higher in the smaller Song Sparrow than in the larger Fox Sparrow in both. We infer that Song Sparrows included more animal matter and less plant matter in their diets than Fox Sparrows, and suggest that fixed traits related to body size might underlie the dietary (trophic) differences. In contrast, δ13C values did not differ between species. We conclude that dietary segregation could help to facilitate the widespread cohabitation of these two species of sparrows.

Nitrification–denitrification in waste stabilisation ponds: a mechanism for permanent nitrogen removal in maturation ponds

A pilot-scale primary maturation pond was spiked with (15)N-labelled ammonia ((15)NH(4)Cl) and (15)N-labelled nitrite (Na(15)NO(2)), in order to improve current understanding of the dynamics of inorganic nitrogen transformations and removal in WSP systems. Stable isotope analysis of delta(15)N showed that nitrification could be considered as an intermediate step in WSP, which is masked by simultaneous denitrification, under conditions of low algal activity. Molecular microbiology analysis showed that denitrification can be considered a feasible mechanism for permanent nitrogen removal in WSP, which may be supported either by ammonia-oxidising bacteria (AOB) or by methanotrophs, in addition to nitrite-oxidising bacteria (NOB). However, the relative supremacy of the denitrification process over other nitrogen removal mechanisms (e.g., biological uptake) depends upon phytoplanktonic activity.

Stable isotopic evidence for trophic groupings and bio-regionalization of predators and their prey in oceanic waters off eastern Australia

Muscle tissue was collected for stable isotope analysis (SIA) from the main fish predators and their fish and cephalopod prey from oceanic waters off eastern Australia between 2004 and 2006. SIA of δ15N and δ13C revealed that the species examined could be divided into three main trophic groups. A “top predator” group consisted mainly of large billfish (Xiphias gladius and Tetrapturus audax), yellowfin (Thunnus albacares), bigeye (T. obesus) and southern bluefin (T. maccoyii) tunas and sharks; with mako (Isurus oxyrinchus) the highest. Below this tier was a second group composed of mid-trophic level fishes including albacore tuna (Thunnus alalunga), lancet fish (Alepisaurus ferox), mahi mahi (Coryphaena hippuris) and ommastrephid squid. Underlying both groups was a grouping of small fishes including myctophids, small scombrids and nomeids as well as surface fishes including macrorhamphosids. These groupings were based largely on mean animal size which showed a positive linear relation to δ15N (r2 = 0.58). Some species showed significant ontogenetic variation in either δ15N (swordfish, lancet fish, yellowfin and albacore tuna) or δ13C (mako shark). We also noted a consistent latitudinal change in δ15N and δ13C at ~28°S for the top predator species, particularly albacore and yellowfin tuna. The differences were consistent with a change from oligotrophic Coral Sea to nutrient rich Tasman Sea waters. These differences suggest that predatory fishes may have extended residence time in distinct regions off eastern Australia.

Consumption and distribution of salmon (Oncorhynchus spp.) nutrients and energy by terrestrial flies

Anadromous Pacific salmon (Oncorhynchus spp.) subsidize terrestrial food webs with their nutrients and carcasses, a process driven largely by selective foraging by bears (Ursus spp.). We quantify wildlife transfer of salmon carcasses to riparian zones on two watersheds in coastal British Columbia and estimate total terrestrial fly production from remnant carcasses. Large-bodied chum salmon (Oncorhynchus keta) were transferred into the forest at a greater rate than were pink salmon (Oncorhynchus gorbuscha) (chum salmon mass = 6089–11 031 kg, 16%–48% of salmon run; pink salmon mass = 2266–2808 kg, 4%–6% of salmon run). Blow flies (genus Calliphora) and other Diptera dominated colonization (>90% of salmon carcasses). Between the two watersheds, 196 and 265 g of Calliphora larvae per metre of spawning length (4 and 7 million larvae for whole watersheds) were generated from salmon carcass transfer. Stable isotope analysis of δ15N and δ13C of spring-emerging adult Calliphora revealed that >80% of individuals had salmon-based signatures. Flies are a dominant consumer and vector of salmon nutrients in terrestrial habitats and supplement the diet of at least 16 vertebrate and 22 invertebrate species. Anticipated further declines of salmon in the North Pacific can be expected to further erode the complex associations coupling marine and terrestrial ecosystems.