Predation Intensity Research Articles

Opportunistic gillnet depredation by common bottlenose dolphins in the southwestern Gulf of Mexico: Testing the relationship with ecological, trophic, and nutritional characteristics of their prey

Competition between fisheries and bottlenose dolphins is a globally relevant conflict given its socioeconomic and ecological implications. Understanding the factors driving the interactions between dolphins and fishery activities is key to the development of appropriate mitigation strategies. Our study aimed to assess whether these interactions are related to the ecological, trophic, and nutritional characteristics of the catch. We used 117 gillnet sets from 48 fishing trips during 2009 – 2010 and 2015 – 2019, which were classified based on the presence or absence of dolphin interactions. These interactions occurred year-round and were documented in 46.1% of the sets, with 14.5% of those showing signs of depredation. The passive acoustic predatory hypothesis, which states that fish species that generate sound are subject to a higher predation intensity by dolphins, was not supported by our data. Also, with the exception of species diversity, ecological parameters such as richness, biomass and CPUE were slightly higher, although not significant in sets with dolphin interaction. Furthermore, during 2015 – 2016, we sampled 123 organisms of 25 representative fish species in the catches and determined the whole fish isotopic composition (δ13C and δ15N), and estimated the nutritional value (i.e., lipid, protein, and energy content) of each species. Isotopic values showed no differences between net settings (with and without interaction), fish habitat, or prey type (potential prey,n= 11 species,vs. non-potential prey,n= 14). However, a preference towards fish from a certain range of thropic levels was evident. All the fish (N= 123) showed significantly higher protein values during the Rainy period, which may be attributed to their reproductive cycles and higher primary productivity. Interestingly, energy contents of the dolphins’ potential prey were also significantly higher during this period. Unexpectedly, protein and energy contents were significantly higher in the fishes caught in the sets without dolphin interaction, but only during the Dry and Windy periods, respectively. Opportunistic feeding habits are well known for bottlenose dolphins, and our results showed that “easy access” to prey will likely prompt interaction with gillnets, regardless of the species composition, biomass, seasonality, preferred habitat, sound production capacity, or nutritional value of the captured fish.

Evidence for local adaptation of oysters to a within-estuary gradient in predation pressure weakens with ontogeny

Consistent spatial variation in phenotypes within a species can reflect local adaptation to gradients in selective pressures, or plastic responses to variable conditions. In benthic marine foundation systems with long, dispersive pelagic larval stages, the usual assumption is that the plastic strategy should dominate, yet surprising examples of local adaptation are accumulating. We tested the potential for local adaptation to an environmentally-driven spatial gradient in predation pressure on the Eastern oyster (Crassostrea virginica) in a Florida estuary by reciprocally transplanting juvenile oysters between two sites. Experimental units included oysters in predator exclosures and controls that were exposed to both consumption by predators and nonconsumptive predator cues. One month after deployment, juvenile oysters from the upper-estuary site where more predators of adult oysters are present exhibited thicker shells in both the upper and lower estuary deployment sites, a possible signal of local adaption to a more intense predation regime. However, nine months after deployment, oysters sourced from both the upper and lower demes had thicker shells in predator-exposed treatments than in predator exclosures, regardless of location. Additionally, there was no evidence that the thicker shells in those oysters led to changes in survival or growth, as one would expect. These results suggest that while oysters from high-predator sites may initially exhibit an apparently adaptive antipredator trait, over the course of an oyster's life, trait expression is a plastic response to the perceived predation threat environment.

Following the track: accuracy and reproducibility of predation assessment on artificial caterpillars

AbstractExperimental studies of biotic interactions in real field conditions are essential to understand the structure and functioning of ecological networks. The use of artificial caterpillars to mimic actual prey availability is generally seen as a standard approach to compare the activity and diversity of predators along environmental gradients. Yet, even with standardized material and procedures, biases may still affect data from multiple observers with different expertise. We used pictures of artificial caterpillars with or without various predation marks, in an online survey that was targeted for the participants of the project, to evaluate the reliability of predation marks identification made by non‐scientists and by scientists with and without experience in predation mark identification. Pictures of artificial caterpillars displayed typical marks left by birds, mammals, and arthropods, as well as non‐predation marks (‘false positive’). In total 357 respondents scanned 7140 pictures of artificial caterpillars. Scientists were more confident and accurate in their observations than non‐scientists, but the differences in correct identifications among scientists and non‐scientists were low. Scientists with experience were also more accurate than scientists without experience, whereas there were no differences in self‐confidence among scientists with and without experience. Accuracy in predation mark identification did not differ among types of predators, but respondents were more keen to identify marks left by birds or mammals than marks left by arthropods. Our results have practical implications for the design of multi‐observer projects relying on artificial caterpillars as a proxy to assess predation intensity, in particular in the context of citizen science.

Dynamics of a predator–prey system with nonlinear prey-taxis

In this paper, we investigate a predator–prey system with nonlinear prey-taxis under Neumann boundary condition. For a class of chemotactic sensitive functions, we obtain the existence and boundedness of global classical solutions for initial boundary value problems in arbitrary dimensional space. In addition, we also study the local stability of the constant steady state solution, and obtain the global asymptotic stability of the steady state solution under different predation intensity by constructing appropriate Lyapunov functions. Furthermore, the steady state bifurcation, Hopf bifurcation and fold-Hopf Singularity are analysed in detail by using Lyapunov–Schmidt reduction method.

Predator control of marine communities increases with temperature across 115 degrees of latitude.

Early naturalists suggested that predation intensity increases toward the tropics, affecting fundamental ecological and evolutionary processes by latitude, but empirical support is still limited. Several studies have measured consumption rates across latitude at large scales, with variable results. Moreover, how predation affects prey community composition at such geographic scales remains unknown. Using standardized experiments that spanned 115° of latitude, at 36 nearshore sites along both coasts of the Americas, we found that marine predators have both higher consumption rates and consistently stronger impacts on biomass and species composition of marine invertebrate communities in warmer tropical waters, likely owing to fish predators. Our results provide robust support for a temperature-dependent gradient in interaction strength and have potential implications for how marine ecosystems will respond to ocean warming.

Efficacy and ethics of intensive predator management to save endangered caribou

AbstractLethal population control has a history of application to wildlife management and conservation. There is debate about the efficacy of the practice, but more controversial is the ethical justification and methods of killing one species in favor of another. This is the situation facing the conservation of woodland caribou (Rangifer tarandus caribou) in Canada. Across multiple jurisdictions, large numbers of wolves (Canis lupus), and to a lesser extent bears (Ursus americanus) and coyotes (C. latrans), are killed through trapping, poisoning or aerial shooting to halt or reverse continued declines of woodland caribou. While there is evidence to support the effectiveness of predator management as a stop‐gap solution, questions remain about the extent to which this activity can make a meaningful contribution to long‐term recovery. Also, there are myriad ethical objections to the lethal removal of predators, even if that activity is in the name of conservation. Debates about predator management, just one of numerous invasive actions for maintaining caribou, are made even more complex by the conflation of ethics and efficacy. Ultimately, long‐term solutions for the recovery of caribou require governments to stop delaying difficult decisions that address the real causes of population decline, habitat change.

Effect of ant-attendance on the occurrence of intraguild predation

Parasitoids and predators exploiting similar food resource make aphidophagous guilds especially favourable systems for studying intraguild predation, but ants as third parties protect aphids against their natural enemies and in return obtain carbohydrate-rich honeydew as a nutritional resource. A field experiment on the interrelationship among aphids, ants and predators/parasitoids was conducted on two plants (hoary cress Cardaria draba L. [Brassicaceae) and Canada thistle Cirsium arvense L. [Asteraceae]). Cardaria was infested with the aphid Acyrthosiphon gossypii Mordvilko (Homoptera: Aphididae) tended by the ant Lasius turcicus Santschi (Hymenoptera: Formicidae). Cirsium was infested with the aphid Brachycaudus cardui L. (Homoptera: Aphididae) tended by the ant Crematogaster sordidula Nylander (Hymenoptera: Formicidae). The mean number of predators per aphid colony decreased significantly when the aphids were tended by ants on both host plants. In contrast, the parasitism rate of both aphids decreased significantly without the tending ant. Thus ant attendance can affect the occurrence and intensity of intraguild predation, and consequently provide enemy free space for parasitoids. If a foraging female aphid parasitoid succeeds in ovipositing into patches with guarding ants, then its offspring could be protected from the risk of intraguild predation.

Protection effectiveness and sea urchin predation risk: The role of roving predators beyond the boundaries of a marine protected area in the Western Mediterranean Sea

Abstract Effective marine protected areas (MPAs) increase top predator density. Accordingly, a large abundance of predatory fish potentially increases predation risk for sea urchins inside an MPA. Intensity of predation was investigated for the sea urchin Paracentrotus lividus at a Mediterranean MPA. Predation rates were estimated for three levels of protection (full, partial, and absent) and two habitats (rocky reefs and Posidonia oceanica meadows). The natural density of sea urchins was correlated with predator biomass (fish sparids Diplodus spp. and Sparus aurata and the gastropod Hexaplex trunculus), and predation risk was evaluated through a tethering experiment. Significantly higher fish predation was found on the rocky reefs of the fully and non‐protected areas than in the partially protected area. These findings are consistent with the sparid biomass estimated in the fully and partially protected areas. However, a discrepancy between high predation risk and low sparid biomass was detected outside of the MPA's northern boundary, where marine farms (fish and mussels) are present. Benthic predator biomass also increased significantly across the northern boundary, but its predation activity was negligible. The low predatory fish biomass and low sea urchin density suggest a top‐down control by roving predatory fish on the rocky reefs of the non‐protected area, in proximity to the fish farms. Similarly, a significant gradient of benthic predator biomass and low sea urchin density suggest potential predation interactions inside the P. oceanica meadows across the northern MPA boundary near the mussel farms. This study highlights deviations from the expected trophic interactions outside the MPA that could be caused by aquaculture activities. Our understanding of the potential synergies between the MPAs and the nearby human activities needs to be broadened to improve the effectiveness of both ecosystem conservation and resource management.

Sex-specific evolution of brain size and structure and covariation with eye size in Trinidadian killifish

AbstractLinks between contrasting ecological conditions and evolutionary shifts in neurosensory components, such as brain and eye size, are accumulating. Whether selection operates in a different manner on these traits between sexes is unclear. Trinidadian killifish (Anablepsoides hartii) are found in sites with and without predators. Male killifish from sites without predators have evolved larger brains and eyes than males from sites with predators. These differences in brain size are present early in life but disappear in adult size classes. Here, we evaluated female brain growth allometries to determine whether females exhibit similar size-specific differences in brain size between sites that differ in predation intensity. We also quantified brain size and structure and eye size to determine whether these structures co-evolved in a sex-specific manner. We found that female brain growth allometries did not differ across populations. Yet, female killifish from sites without predators exhibited a larger cerebellum, optic tectum and dorsal medulla early in life (before maturation), although such differences disappeared in larger size classes. Females from sites with predators exhibited similar patterns in brain growth to males in those sites; therefore, shifts in brain size and structure are driven by differences between sexes in sites without predators. We also found evidence for covariation between brain and eye size in both sexes despite different levels of variation in both structures, suggesting that these structures might covary to fluctuating degrees in sex-specific ways. We conclude that differential investment in brain tissue in sites without predators might be linked to varying reproductive and cognitive demands between the sexes.

Ecological Infrastructures May Enhance Lepidopterans Predation in Irrigated Mediterranean Farmland, Depending on Their Typology and the Predator Guild

Ecological infrastructures (EIs) are considered relevant components in agricultural landscapes to support biodiversity and ecosystem services. We used the predatory attacks on lepidopteran dummies as a proxy to assess predation rates in the agricultural matrix and different EIs types according to their location and vegetation structure. We aimed at comparing the effect of different types of EI on the predation intensity in two intensively irrigated agricultural areas located in the Sorraia and Tagus river valleys in central Portugal. We hypothesized that: (1) the predation rate would be higher near EIs compared with the agricultural matrix, (2) the positive effect of EIs on predation rate would differ with their typologies, and (3) the EIs’ proximity and proportion in the surrounding landscape would have a positive effect on the predation rate in agricultural fields. The EI typologies influenced differently the predator groups and the overall predation rate. Major differences were observed for bird predation, being higher in woody EIs. A positive correlation between predation rate and EIs area of the surrounding landscape, as well as a negative correlation with the distance to the nearest riparian and woody EIs, was observed for birds. The observed dissimilarities in the predators’ response may be related to habitat differences and its functional connectivity. The overall monthly low predation rates are possibly related to the intensive agricultural system and the small area occupied by EIs.

Extensive spatial impacts of oyster reefs on an intertidal mudflat community via predator facilitation

Habitat engineers make strong and far-reaching imprints on ecosystem processes. In intertidal mudflats, the dominant primary producer, microphytobenthos (MPB), often forms high biomass patches around oyster reefs. We evaluate multiple hypotheses linking MPB with oyster reefs, including oyster biodeposition, meiofaunal grazing, and abiotic factors, aiming to help predict effects of reef removal or proliferation. We quantify spatial patterns of an Atlantic mudflat community and its environment around two large Crassostrea reefs before experimentally sacrificing one reef via burning. MPB biomass was enriched surrounding living oyster reefs although infaunal biomass and individual sizes were low. Structural equation modelling best supported the hypothesis that crab predation intensity, which decayed with distance from the reefs, locally freed MPB from grazing. Our results suggest that Crassostrea reef expansion may enrich local MPB patches and redirect trophic energy flows away from mudflat infauna, with potential implications for the sustainability of local fisheries and bird conservation.

Space and Habitat Utilization of the Red King Crab (Paralithodes camtschaticus) in a Newly Invaded Fjord in Northern Norway

The red king crab (RKC, Paralithodes camtschaticus) was introduced to the southern Barents Sea in the 1960s with the aim to develop a new, commercially attractive stock of the species. In the subsequent decades, the stock has indeed become abundant and widespread, but the species’ presence also implies intense predation on benthic biota and thereby severe degradation of benthic ecosystems. Our capacity to monitor and harvest the species efficiently is therefore imperative. Yet, fishermen report highly variable catches despite little variation in the timing and location of fishing, possibly induced by the species’ migratory behavior, which makes the search for crab aggregations time consuming and expensive. Previous studies have shown that the RKC is capable of conducting long-distance migrations, and suggest that the species conduct seasonal migrations between shallow (winter- and springtime) and deep waters (summer and autumn). Here, we applied telemetry to investigate the migratory behavior and habitat utilization of 37 adult individuals of the RKC in a relatively shallow fjord in northern Norway from late May until early November. Approximately half of the crabs (n = 16) left the study area early during the study period, but some individuals (n = 3) were recaptured between 53 and 147 km away from the study area, confirming that the RKC may conduct long-distance migrations. In contrast to expectations, most of the remaining individuals of RKC (n = 16) stayed for a prolonged summer and autumn period and used a limited portion of the fjord. These crabs responded quickly to changes in ambient water temperature, seeking deeper and colder waters masses when the temperature in shallower waters increased. Several individuals showed nearly identical spatio-temporal distributions, which supports earlier observations of crab aggregations. Our data indicates that the area utilization of the RKC is affected by trade-offs between biotic and abiotic factors, in which sub-optimal water temperatures may be tolerated provided appropriate access to food. Thus, our findings suggest that the current knowledge of RKC seasonal migration patterns may need to be revised, which in turn will have implications for managers and the fishing industry. This study demonstrates the high potential of telemetry studies to yield new, high-resolution data and knowledge of species’ ecology.

Stronger negative species interactions in the tropics supported by a global analysis of nest predation in songbirds

AbstractAimSpecies interactions are assumed to be stronger closer to the equator. However, numerous studies provided conflicting results and considerable controversy exists concerning the latitudinal patterns in the intensity of biotic interactions. Thus, the question of whether biotic interactions are stronger near the equator remains open. Here, we provide a global evaluation of latitudinal trends in nest predation in songbirds and their explanations.LocationWorldwide.TaxonSongbirds (Aves: Passeriformes).MethodsWe collected published data on nest predation in 1297 populations of 659 species across the globe (124,958 nests). We quantified latitudinal trends in the intensity of nest depredation (daily predation rate, DPR) and in potential demographic impacts of nest depredation (the proportion of nests destroyed by predators). We also quantified the latitudinal trend in the proportion of failed nests destroyed by predators and assessed how nest depredation and latitudinal trends differed across nest types. We aimed at explaining spatial variation in nest predation by productivity and species richness of potential nest predators.ResultsAll measures of nest predation increased towards the equator and the increase was stronger in the northern hemisphere. Nest predation also increased with time, and it was higher in open nests than in cavities. Nest predation increased with productivity (indexed by NDVI), independently of latitude. It also increased with species richness of potential nest predators, but this effect was confounded with latitude.Main conclusionsTropical songbirds faced both higher intensity of nest predation (higher DPR) and more detrimental demographic outcomes of nest depredation (higher proportion of nests lost to predators). Moreover, the proportion of nest failure caused by predators also increased towards the equator. Our results support the view that birds are subject to strong biotic interactions close to the equator. Nest predation increased with productivity and tended to increase with species richness of potential nest predators.

Alien vs. predator: influence of environmental variability and predation on the survival of ascidian recruits of a native and alien species

Drivers of successful introduction of exotic species remain a major headline in marine invasion biology. We ran two experiments aiming to disentangle the effects of abiotic factors like contaminants and the effect of predation on recruits’ survival of one native and one alien ascidian species. A feeding experiment allowed us to monitor microscale variation of generalist fish predation, which varied significantly within a marina. We also monitored the in situ survival of lab-grown ascidians at three locations within the marina, half with predator cage exclusion. The survival of the native Ciona intestinalis was conjointly highly influenced by location and caging. We were able to identify a link between predation intensity exerted by mobile generalist macropredators and C. intestinalis survival, whereas none of the measured contaminants accounted for site variability of survival. The non-indigenous Styela clava had significant higher survival and biomass when uncaged, suggesting a positive effect of predation for this species. The natural in situ recruits of C. intestinalis showed higher biomass when caged and may have competed with lab-grown S. clava. Our results suggest that generalist fish predation may play a crucial role in the success of non-indigenous species due to facilitation through competitive release.

Growth Parameters of Sentani Gudgeon Fish (Oxyeleotris heterodon) in Sentani Lake, Papua

ABSTRACTThe Sentani Gudgeon Fish (Oxyeleotris heterodon, Weber 1907) from the family Butidae with the general name Sentani Gudgeon is known locally as Gabus Malas and Himen. Sentani Snakehead Fish is one source of animal protein that is very important for the community around Lake Sentani. The population of the Sentani Gudgeon Fish species is at a crucial level. The issue could be affected by environmental pressures, continuous catches, competition with introduced species from outside Papua, intensive predation systems, and imbalances in ecological systems. The condition made a decline in population size until it became extinct. Gudgeon Sentani fish is the main target of catching in the lake. This condition significantly affects stock, size when first captured, population decline, reproductive cycle, and average catch. Until now, data and information on the growth of snakehead fish as the basis for fisheries management in the waters of Lake Sentani are not widely known. Considering the importance of preserving the native species of Lake Sentani, especially the Snakehead Fish, efforts to manage the fisheries in Lake Sentani's waters are urgent. This research was conducted in March - October 2020, located at Lake Sentani. The specimens were obtained from the catch of fishers with various gill nets and chopsticks. Enumerators or field assistants assisted the recording of the number and measurement of the total length of fish caught by fishermen daily. The results of the analysis showed: asymptotic size (L?) 46.20 cm, growth coefficient (K) 0.29, the total mortality rate (Z) 0.80 per year, natural mortality (M) 0.74 per year, the mortality rate due to fishing (F) 0.06 per year and exploitation rate (E) 0.075 per year.

Predation increases multiple components of microbial diversity in activated sludge communities

Protozoan predators form an essential component of activated sludge communities that is tightly linked to wastewater treatment efficiency. Nonetheless, very little is known how protozoan predation is channelled via bacterial communities to affect ecosystem functioning. Therefore, we experimentally manipulated protozoan predation pressure in activated-sludge communities to determine its impacts on microbial diversity, composition and putative functionality. Different components of bacterial diversity such as taxa richness, evenness, genetic diversity and beta diversity all responded strongly and positively to high protozoan predation pressure. These responses were non-linear and levelled off at higher levels of predation pressure, supporting predictions of hump-shaped relationships between predation pressure and prey diversity. In contrast to predation intensity, the impact of predator diversity had both positive (taxa richness) and negative (evenness and phylogenetic distinctiveness) effects on bacterial diversity. Furthermore, predation shaped the structure of bacterial communities. Reduction in top-down control negatively affected the majority of taxa that are generally associated with increased treatment efficiency, compromising particularly the potential for nitrogen removal. Consequently, our findings highlight responses of bacterial diversity and community composition as two distinct mechanisms linking protozoan predation with ecosystem functioning in activated sludge communities.

Do Active and Passive Antipredator Defences in the Toad Epidalea calamita Differ between Males and Females from Natural Habitats and Agrosystems?

Due to their assumed costs, simultaneous antipredator strategies are expected to face trade-offs, which, however, could be milder in individuals subjected to a more intense predator pressure. In this work, I studied the relationship between locomotion and parotoid glands in the natterjack toad, Epidalea calamita. Specifically, I predicted that individuals with reduced sprint speed would rely more on their chemical defences, having larger and more aposematically coloured parotoid glands. In addition, I expected this trade-off to be more evident in females and toads from pine grove habitats, because, according to previous work, males and toads from agrosystems are under greater predator pressure. However, sprint speed showed no relationship with coloration, but toads with proportionally greater parotoid glands were also proportionally faster. Thus, the costs of these antipredator traits might not be high enough to make them interfere, or the benefits of simultaneous optimisation of sprint speed and parotoid gland size might outweigh the costs of it in some individuals. In any case, habitat and sex did not affect these relationships, so the trends detected are valid across sexes and the habitats studied.

Linking Plant Functional Traits to Demography in a Fragmented Landscape

Habitat loss in highly deforested landscapes such as the Brazilian Atlantic Forest has been severely affecting the diversity and survival of palm species. As some species are more sensitive than others, trait responses to the environment, as well as environmental effects on fecundity, growth, and mortality rates, may affect species demography. Considering this context, we studied functional and demographic responses of three palm species (Astrocaryum aculeatissimum, Euterpe edulis, and Geonoma schottiana) to habitat loss in the Atlantic Forest in southeastern Brazil by measuring morpho-physiological traits related to plant growth and light acquisition for photosynthesis. We also tested the response of population fitness to fragment size. Plant survival and growth was subsequently monitored in 2006 and 2007, and population dynamics were summarized in pool matrices for large and small forest fragments in the monitoring periods comprehending one full year between 2005–2006 and 2006–2007. The asymptotic growth rate of populations (defined here as population fitness, λ) in five forest fragments was then calculated. Diameter of individuals of the demography plots (from year 2005 to 2007) was used to calculate the relative diameter growth rate. Later, in 2015, we measured a set of morpho-physiological functional traits in palms in the same plots used in the demographic studies. While A. aculeatissimum populations were stable in both monitoring periods in small and large fragments, E. edulis populations were predicted to decline due to intense predation by monkeys in the large fragment, but were stable in the smaller fragments, and G. schottiana populations were stable in the large fragments in both monitoring periods, but populations in the smaller fragments were predicted to decline in the second period, i.e., with lower fitness in these fragments. In addition, the functional traits analyzed showed that G. schottiana is a forest interior species associated with the shade/understory environment response. E. edulis was also affected by the size of the fragment, but due to a disruptive interaction with a predator and showed intermediate functional traits values. On the other hand, A. aculeatissimum thrived in areas with higher and lower incidence of light and was not demographically affected by forest remnant size. This suggests that E. edulis and A. aculeatissimum are habitat generalists. We concluded that differences in the ecophysiological performance of palms due to distinct morpho-physiological functional traits related to leaf economic spectrum, such as LDMC or specific leaf area (SLA) and to photosynthetic responses to light environment as electron transport rate (ETR) and saturation irradiance (Ik) were linked to the demographic variation observed in forest remnants of different size.

Quantifying the ecosystem service of non‐native weed seed predation in traditional terraced paddy fields

AbstractWeed seed predation is an important ecosystem service in paddy areas. To conserve and sustainably utilize this service, it is necessary to quantify the seed predation and reveal the relative contributions of seed predators. In this study, we quantified the extent of postdispersal seed predation of Lolium multiflorum Lam., a non‐native invasive grass weed, on levees of terraced paddy fields located in a traditional cultural landscape (satoyama landscape) of Japan. We investigated the temporal variability in seed predation of L. multiflorum during summer after the seed shed, and estimated the total seed loss due to predation on the levees of terraced paddy fields for 2 years. Furthermore, the relative contribution of invertebrates and vertebrates to the seed predation was estimated based on exclosures. The total seed loss due to predation during 4 months (from late June to late October) was consistently high (>99%) in both years (the maximum proportion of seed predation per 2 weeks = 80.0–86.7%). The seed predators were likely to be mainly invertebrates such as crickets and ground beetles. This study revealed that the seed predation intensity was consistently high and can be an important depletion factor for the seedbanks of weeds such as L. multiflorum on the levees of terraced paddy fields. The high intensity of seed predation by invertebrates might suppress the invasion and population expansion of L. multiflorum on the levees of terraced paddy fields.

Variability in site characteristics linked to bay scallop abundance but not tethered survival: Implications for restoration

While predation impacts the abundance and distribution of prey species, the overall impact of predation varies with predator identity, predator density, and habitat complexity, among other factors. Numerous commercially and recreationally important prey species, such as bivalves, face intense predation that may affect management and restoration efforts. Therefore, predicting sites with elevated predation risk can be critical for successful restoration, although making predictions based on lab feeding assays may provide challenges. This study used bay scallops Argopecten irradians as a model organism to examine scallop abundance and survival in relation to predator density, habitat complexity, and predicted consumption, across multiple sites within the same estuary. Published predator-specific relationships between scallop consumption and habitat complexity were combined with field survey data to predict consumption potential at six sites in Shinnecock Bay, NY, USA. Using a series of Pearson correlations, the relationships between scallop abundance and tethered survival and site characteristics (habitat complexity, predator density, estimated consumption, scallop recruitment) were explored. Seagrass cover and recruitment of new individuals both strongly influenced scallop abundance, although tethered survival was not strongly correlated to any site metric (predator density, seagrass complexity, or estimated consumption). This study demonstrates potential issues when trying to link mesocosm studies to the field environment, such as sites with no seagrass but potentially confounding habitat complexity (i.e., Crepidula fornicata) and overestimates of consumption due to lack of realism in mesocosm studies. Overall, our study highlights the necessity of conducting field experiments to test mesocosm results, but also provides several valuable conclusions for shellfish restoration.