Predation Rates Research Articles

Lethal competition on joint predators during suppressing brown planthopper population

Joint predator is one technique to control brown planthopper (Nilaparvata lugens) in the rice field by combining two or more predator species having a positive interaction. This study aims to determine the effect of joint predator density (Pardosa pseudoannulata and Phidippus sp) on competition and its predatory rate in suppressing the N.lugens population. The study used a completely randomized design (CRD) by combining P. pseudoannulata or Pp (1,2,3 individuals) and Phidippus sp or Ps (1,2,3 individuals) to become Pp1Ps1, Pp1Ps2, Pp1Ps3, Pp2Ps1, Pp2Ps2, Pp2Ps3, Pp3Ps1, Pp3Ps2, Pp3Ps3. The parameters observed were predation rate, bodyweight, mortality of both predators, and competition model. The results showed that the composition difference between P. pseudoannulata and Phidippus sp affected on competition model and the predation. The predation rate of joint predators at different densities ranged from 40.4 – 47.0 individuals of N.lugens (80.8-94.0%) in one-day observation, and they consumed all prey until the third day’s observation. The highest predation rate occurred for Pp3Ps3, but it was assumed it was not safe because of cannibalism and lethal competition. The Pp1Ps2 composition of joint predators was classified as safe, with 0 and 0.2 individuals’ mortalities and followed by draw competition between two predators.

A MODIFIED MAY–HOLLING–TANNER MODEL: THE ROLE OF DYNAMIC ALTERNATIVE RESOURCES ON SPECIES’ SURVIVAL

This paper investigates the dynamical behavior of the modified May–Holling–Tanner model in the presence of dynamic alternative resources. We study the role of dynamic alternative resources on the survival of the species when there is prey rarity. Detailed mathematical analysis and numerical evaluations, including the situation of ecosystem collapsing, have been presented to discuss the coexistence of species’, stability, occurrence of different bifurcations (saddle-node, transcritical, and Hopf) in three cases in the presence of prey and alternative resources, in the absence of prey and in the absence of alternative resources. It has been obtained that the multiple coexisting states and their stability are outcomes of variations in predation rate for alternative resources. Also, the occurrence of Hopf bifurcation, saddle-node bifurcation, and transcritical bifurcation are due to variations in the parameters of dynamic alternative resources. The impact of dynamic alternative resources on species’ density reveals the fact that if the predation rate for alternative resources increases, then the prey biomass increases (under some restrictions), and variations in the predator’s biomass widely depend upon the quality of food items. This study also points out that the survival of predators is possible in the absence of prey. In the theme of ecological balance, this study suggests some theoretical points of view for the eco-managers.

Increased ladybird predation and metabolism do not counterbalance increased field aphid population growth under experimental warming

Abstract Climate change may have diverse and complex impacts on species interactions, destabilizing food webs and ecosystem services. The effects of warming on the top‐down biological control of crop pests have been considerably less studied than bottom‐up effects through crop physiological changes. We studied the effect of a 2°C warming in the laboratory and in wheat fields on the predation and metabolism of Harmonia axyridis on wheat aphids using molecular gut content analysis. We also measured the effects of warming on the predation rate and functional response of H. axyridis on each aphid species in the laboratory, as well as on DNA degradation rate. Field densities of Sitobion avenae and Rhopalosiphum padi, the two most abundant wheat aphid species, were increased by 2 and 2.5 times, respectively, under experimental warming, but densities of H. axyridis were not. Field predation rate of H. axyridis on these two aphid was found to be about 25% lower under elevated temperature. This could have been due to faster prey digestion, since degradation of the preferred aphid species, Sitobion avenae, was 1.5 times faster under elevated temperature. However, the functional response of H. axyridis larvae on these two species was 1.5 times higher under warming over the range of prey densities tested (50–250 over 24 h). The total predation rate of H. axyridis larvae on a mixture of S. avenae, R. padi and Schizaphis graminum aphid prey was also increased by 1.4 times, but consumption of R. padi aphids was increased while that of S. graminum was decreased under warming. Overall, our results show that global warming could strongly increase pest outbreaks and destabilize biological pest control, which would likely result in accrued yield losses. Read the free Plain Language Summary for this article on the Journal blog.

Temporal variation in tree diversity effects on birds and its implications for top-down control of insect herbivores in a tropical system.

Tree diversity promotes predator abundance and diversity, but evidence linking these effects to increased predation pressure on herbivores remains limited. In addition, tree diversity effects on predators can vary temporally as a function of environmental variation, or due to contrasting responses by different predator types. In a multi-year study, we assessed temporal variation in tree diversity effects on bird communityabundance, diversity, and predation rates as a whole and by functional group based on feeding guild (omnivores vs. insectivores) and migratory status (migrant vs. resident). To this end, we conducted bird point counts in tree monocultures and polycultures and assessed attacks on clay caterpillars four times over a 2-year period in a tree diversity experiment in Yucatan, Mexico. Tree diversity effects on the bird community varied across surveys, with positive effects on bird abundance and diversity in most but not all surveys. Tree diversity had stronger and more consistent effects on omnivorous and resident birds than on insectivorous and migratory species. Tree diversity effects on attack rates also varied temporally but patterns did not align with variation in bird abundance or diversity. Thus, while we found support for predicted increases in bird abundance, diversity, and predation pressure with tree diversity, these responses exhibited substantial variation over time and the former twowere uncoupled from patterns of predation pressure, as well as contingent on bird functional traits. These results underscore the need for long-term studies measuring responses by different predator functional groups to better understand tree diversity effects on top-down control.

Brood protection is essential but not sufficient for population survival of lapwings Vanellus vanellus in central Switzerland

Lapwing are among those ground nesting bird species that suffered strong population declines following agricultural intensification in many parts of Europe. The key problem appears to be a low breeding success which, depending on the situation, may be due to predation of eggs and chicks, starvation of chicks especially during dry conditions, agricultural activities leading to direct killings, and suboptimal breeding habitat. Here, we report on a population of 40–60 lapwing breeding pairs in an intensively cultivated arable landscape in central Switzerland, where protection from farming activities, implementation of special lapwing habitat and nest fencing to exclude terrestrial predators (mainly red fox) started in 2005 and is still ongoing. Chicks were ringed and families subsequently observed every 2–3 days. Hatching success for fenced nests built before May was high. Low hatching success was observed in unfenced nests due to high predation rates and in late nests due to abandonment by the female when the vegetation was growing too tall (e.g. maize). Regularly, chicks disappeared during the night shortly after hatching. Most likely many of them first left the fence and were predated outside. Our observations from a fenced field with wet soils and puddles suggest that lapwing may produce sufficient offspring if predation can be reduced and if large enough areas with suitable habitat are available.

Are the ladybugs Cryptolaemus montrouzieri and Exochomus quadripustulatus (Coleoptera: Coccinellidae) candidate predators of Toumeyella parvicornis (Hemiptera: Coccidae)?

Toumeyella parvicornis is an alien pest of recent introduction in Italy that infests stone pines (Pinus pinea L.), its main host plant in Europe. Infestations are currently controlled through endotherapic treatments, but the high costs and the long-term inefficacy highlight the need for alternative control strategies applicable in natural systems as well. An analysis of the effectiveness of autochthonous and naturalized predators is the first step to achieve this goal. This work focused on two candidate predators, Exochomus quadripustulatus and Cryptolaemus montrouzieri (Coleoptera: Coccinellidae), that may potentially control T. parvicornis. The analysis was carried out under laboratory-controlled and semi-field conditions. Laboratory tests were carried out to assess: (i) the predation rate of the ladybugs over different densities of pest preimaginal stages, and (ii) the effect of the presence of heterospecific and conspecific predators on the attractiveness of prey colonies. Semi-field experimentations were carried out by wrapping infested stone pine twigs with net sleeves and applying one of three treatments: (i) Exochomus quadripustulatus, (ii) Cryptolaemus montrouzieri, and (iii) control containing only the pest population. Both the ladybugs were attracted by T. parvicornis, offered as prey. Exochomus quadripustulatus was more attracted to conspecific and heterospecific ladybugs than Cryptolaemus montrouzieri and responded to prey more quickly. The results obtained could be useful for planning further experimentations to explore the potential use of these predators in biological control programs that may be applied in infested areas. Besides the use in an urban context, where pesticide use is strongly limited, the release of natural enemies may help safeguard stone pine forests. © 2024 Society of Chemical Industry.

Predator-Prey Interaction Between Xylocoris sordidus (Hemiptera: Anthocoridae) and Enneothrips enigmaticus (Thysanoptera: Thripidae).

The peanut thrips, Enneothrips enigmaticus (Thysanoptera: Thrypidae), is an important pest of the peanut (Arachis hypogaea) in South America. Due to concerns about the environment and human health induced by the extensive use of pesticides in the management control of pests, environmentally and friendlier tactics must be targeted. Thus, this study investigates, for the first time, the behavior of Xylocoris sordidus (Hemiptera: Anthocoridae) as a biological control agent for E. enigmaticus. The methodology included no-choice tests to assess whether the predation rate varies according to the developmental stage of the prey, as well as the predator's developmental stage with the highest predation capacity. Additionally, an analysis of the functional response of adult and 5th instar nymphs of X. sordidus exposed to different densities of E. enigmaticus nymphs (1, 2, 4, 8, 16, and 32) was conducted. The results confirm the predation of peanut thrips by X. sordidus, with a higher predation rate in the nymphal stages of the prey. There was no difference in predation capacity between predator nymphs and adults, and exhibiting a type II functional response. Therefore, the potential of X. sordidus as a biological control agent for E. enigmaticus is confirmed, showing the importance of adopting measures to preserve this predator in peanut crops.

Microplastics influence the functional responses of a tropical estuarine calanoid Pseudodiaptomus annandalei

Being chemically inert and morphologically similar (<5 mm in size) to the natural prey of copepods, microplastics (MPs) affect them through entanglement, ingestion, and interference with their natural prey selection. The effects of external factors, such as MP, can be observed in the form of alterations in the functional and numerical responses of copepods. Functional response is explained as the relationship between the intake rate of a consumer and the amount of food available in a particular ecotope. Considered three types of functional response: (i) with increasing food density, when intake rate increases linearly until asymptote, called Type-I functional response; (ii) when the proportion of prey ingested by the consumer decreases monotonically with prey density, considered as a Type-II functional response; and (iii) when ingestion rate and food density show a sigmoid relationship, is considered as Type-III functional response. In the present study, we attempted to elucidate the effects of MP on the functional responses of brackish water, demersal, calanoid copepod, Pseudodiaptomus annandalei, feeding on the rotifer Brachionus rotundiformis, and the ciliate Frontonia microstoma. The ability of P. annandalei to survive environmental fluctuations and its nutritional value make it an ecologically important organism in estuarine ecosystems. The experiment for estimation of functional response included four setups with adult and copepodite stages of P. annandalei, each with six replicates at six different prey densities, in the presence and absence of MP particles. Without MPs, P. annandalei showed a typical Type-II functional response, where the proportion of prey consumed significantly declined with increasing prey density. In the MP-applied medium, the proportion of prey consumed did not exhibit a significant relationship with the initial prey density. The number of ciliates and rotifers ingested by copepodites and adults was significantly lower in MP-contaminated medium than in prey either monospecific or in combination with microalgae. Because of the comparable size of MP to the prey species and unspecialized feeding of P. annandalei in natural waters, we hypothesized reduced predation rates as a result of pseudo-satiation resulting from MP ingestion leading to malnutrition and MP storage in copepod biomass.

Temporal and spatial refugia modify predation risk for non-native crabs in rocky intertidal habitats.

Populations of the non-native Asian shore crab, Hemigrapsus sanguineus, now dominate the rocky intertidal of southern New England, USA. High abundances suggest the recent invader may have experienced enhanced success as a result of enemy release. While larvae and juveniles may serve as a food source for ecologically important species, little is known about predation of mature H. sanguineus or the influence of habitat on predation pressure. To assess natural predation rates of adult H. sanguineus, crabs were tethered in the intertidal at Clarks Cove in New Bedford, MA. Crabs were left in situ for half of a tidal cycle then observed for signs of predation. Results of separate high and low tide trials showed that adult crabs were preyed upon at both high and low tide, though at a significantly higher rate during high tide during both daytime and nighttime, suggesting predation by aquatic species is greater than that by terrestrial species. To investigate the role of habitat as refuge from predation, a laboratory experiment manipulated the complexity of habitat provided to crabs in the presence of a native fish predator. Results indicate better refuge is provided by more complex shelter. Together, findings suggest that fish, crabs, and/or diving birds are important predators for H. sanguineus in the invaded range and that habitat refuge acts to reduce predation pressure.

Rapid change in anti‐predator behaviour of a threatened marsupial after thousands of years of isolation from predators

AbstractPrey naivety occurs when an animal does not recognize or is unable to respond effectively to the threat of a predator. Many animals lose their anti‐predator responses if they become isolated from predators, becoming vulnerable to increased predation rates if released into areas where native or introduced predators are present. In situ exposure to introduced predators is a technique that has been shown to improve anti‐predator traits in burrowing bettongs (Bettongia lesueur) and greater bilbies (Macrotis lagotis) and is associated with greater survival in bilbies. However, little is known about how in situ exposure to native predators can address the issue of prey naivety. This study investigated whether Shark Bay bandicoots (Perameles bougainville) from a remnant island population isolated from all mammalian predators for several thousand years could improve their anti‐predator behaviour after living with a native predator, the western quoll (Dasyurus geoffroii). We compared the vigilance and wariness behaviour, and nest site attributes of bandicoot populations living with and without native quolls at the Arid Recovery Reserve in South Australia. We found that after 6 years of quoll exposure, quoll‐exposed bandicoots had significantly larger flight initiation distances and spent more time engaged in vigilance behaviours at feed trays compared to control bandicoots. Quoll‐exposed bandicoots also selected nests with increased vegetation cover, preferring nests with both understory and overstory shrub cover present. The results of this study indicate that in situ exposure to native predators can improve vigilance and wariness behaviours in Shark Bay bandicoots over relatively short time frames. Exposing threatened species to native predators may assist with preparing them for life outside fenced safe havens.

Clay larvae do not accurately measure biogeographic patterns in predation

AbstractAimSpatial variation in predation can shape geographic patterns in ecology and evolution, but testing how predation varies across ecosystems is challenging as differing species compositions and defensive adaptations can mask underlying patterns. Recently, biogeography has borrowed a tool from ecology: clay prey models. But clay models have not been adequately tested for geographic comparisons, and a well‐known problem –that clay prey only appeal to a subset of potential predators– could bias detected geographic patterns whenever the relative importance of predator guilds varies among sites. Here, we test whether clay larvae accurately capture geographic differences in predation on real larvae.Location90° of latitude and >2000 m elevation across the Americas.TaxonVertebrate and invertebrate predation on ‘superworms’ (Zophobas larvae).MethodsAcross six sites that vary dramatically in latitude, elevation, and biome, we quantified predation on live, dead, and clay larvae. We physically excluded vertebrate predators from some larvae to distinguish total predation and invertebrate‐only predation.ResultsPredation on live superworms almost doubled from our high‐elevation high‐latitude site to our low‐elevation tropical site. Geographic patterns were consistent among live and dead larvae, but clay larvae missed extremely high predation at some sites and therefore mis‐measured true geographic patterns. Clay larvae did a particularly bad job at capturing geographic patterns in predation by invertebrates, although sample sizes for invertebrate predation were small.Main ConclusionsClay larvae are inappropriate for comparing predation rates across sites. They should be abandoned for biogeographic studies and reserved for comparisons within, rather than across, predator communities.

New grasslands promote pollination but not biological pest control in nearby arable fields in the short term

Agricultural intensification is a major threat to farmland biodiversity and associated ecosystem services. Semi-natural habitats are integral to the preservation of farmland biodiversity and ecosystem services, however, the extent in which they contribute to specific services is largely unclear. We studied predation rates of ground-dwelling predatory arthropods, and pollination success within old permanent grasslands, newly established grasslands and arable fields near and far from new grasslands. We evaluated whether grassland restoration can enhance pollination and biological control in crop fields. For this purpose, we established new grassland strips within cereal fields, which directly bordered existing permanent grasslands. We evaluated if the distance to these old and new grasslands affects the delivery of the two ecosystem services within crop fields. We found significantly higher seed numbers and seed weight in sentinel plants placed in old grasslands, new grasslands and nearby arable fields compared to distant arable fields. We also found significantly decreasing seed numbers and seed weight in sentinel plants placed in distant arable fields with increasing distance from old grasslands, while pollination success was not affected by distance in nearby arable fields. Contrary, we did not find any significant effects of new grasslands on biological control. Our study showed that 3 years after establishing grasslands arable fields benefited from the proximity of flower-rich new grasslands through increased pollination success though not regarding biological control. This indicates that, on a short term, establishing new grasslands can support beneficial arthropods in providing ecosystem services such as pollination. Predators, in contrast, might take longer to establish effective populations that denote higher predation rates. Our study provides a baseline for future long-term studies to better evaluate pollination and pest control patterns within arable fields.

The Study of Stability Analysis of Modified Leslie-Gower Herbivore Model with Allee Effect in Plants

A modified Leslie-Gower plant-herbivore model is studied under the Allee effect. Holling-type II functional response is used to modify the model. Delay differential equations play an essential role in making this model more realistic and complicated. The non-trivial equilibrium E* (P* ≠ 0, H* ≠ 0) of the proposed model is calculated. Moreover, the stability and instability of the state variables, which include plant population P and herbivore population H are described graphically. It is shown that the system represents absolute stability when it has no time parameter (τ). When the time parameter is less than the threshold value, then the system exhibits asymptotic stability. In addition, the system surrenders its stability, and Hopf-bifurcation occurs when the time parameter surpasses the threshold value. The timeseries graphs are also represented. It is demonstrated that the system becomes more stable with the maximum rate of predation. MATLAB software is used to perform the graphs to justify the theoretical results.

Depredation rates and spatial overlap between Great Hammerheads and Tarpon in a recreational fishing hot spot

AbstractObjectiveShark depredation, the full or partial consumption of a hooked fish by a shark before it is landed, is an increasing source of human–wildlife conflict in recreational fisheries. Reports of shark depredation in the catch‐and‐release Tarpon (also known as Atlantic Tarpon) Megalops atlanticus fishery in the Florida Keys are increasing, specifically in Bahia Honda, a recreational fishing hot spot and a putative Tarpon prespawning aggregation site.MethodsUsing visual surveys of fishing in Bahia Honda, we quantified depredation rates and drivers of depredation. With acoustic telemetry, we simultaneously tracked 51 Tarpon and 14 Great Hammerheads (also known as Great Hammerhead Sharks) Sphyrna mokarran, the most common shark to depredate Tarpon, to quantify residency and spatial overlap in Bahia Honda.ResultDuring the visual survey, 394 Tarpon were hooked. The combined observed shark depredation and immediate postrelease predation rate was 15.3% for Tarpon that were fought longer than 5 min. Survival analysis and decision trees showed that depredation risk was highest in the first 5–12 min of the fight and on the outgoing current. During the spawning season, Great Hammerheads shifted their space use in Bahia Honda to overlap with Tarpon core use areas. Great Hammerheads restricted their space use on the outgoing current when compared to the incoming current, which could drive increased shark–angler interactions.ConclusionBahia Honda has clear ecological importance for both Tarpon and Great Hammerheads as a prespawning aggregation and feeding ground. The observed depredation mortality and postrelease predation mortality raise conservation concerns for the fishery. Efforts to educate anglers to improve best practices, including reducing fight times and ending a fight prematurely when sharks are present, will be essential to increase Tarpon survival and reduce shark–angler conflict.

Lasting effects of avian‐frugivore interactions on seed dispersal and seedling establishment

Abstract The consequences of plant–animal interactions often transcend the mere encounter stage, as those encounters are followed by a chain of subsequent stages on the plant's reproductive cycle that ultimately determine fitness. Yet, the dissemination and recruitment stages of animal‐mediated seed dispersal are seldom analysed jointly, hindering a full understanding of the ecology of seed dispersal. We analyse the dispersal and recruitment of a fleshy‐fruited plant (Pistacia lentiscus), from fruit production to seedling survival up to their second year. We link early reproductive investment of individual plants to seedling recruitment and explore the role played by seed viability, the coterie of frugivores and microhabitat seed deposition. The proportion of viable seeds was generally low (mean = 34%) but highly variable among individual plants (range: 0%–95%). Seed viability did not seem to have a direct effect on individual plant's recruitment. We recorded 28 bird species feeding on P. lentiscus fruits or seeds. Their contribution to plant recruitment was mainly determined by their intensity of fruit consumption and probability to disperse viable seeds. Most frugivores presented non‐random microhabitat preferences, delivering uneven seed contributions to different sites. Post‐dispersal seed predation by rodents was the most limiting phase in P. lentiscus recruitment. Yet, microhabitats showing the lowest predation rates received the lowest seed rain. Hence, we found a decoupling of the dissemination and recruitment stages: most seeds do not arrive at the most suitable microhabitats. We estimate P. lentiscus plants need to produce c. 5 × 105 fruits to recruit a single seedling that survives to its second summer in our study site. Its success as a prevalent species in Mediterranean lowland landscapes relies on its high fecundity and thorough fruit removal and dispersal by a diversified frugivore assemblage, which compensates for the high seed unviability characteristic of this genus. Synthesis: Measuring the delayed, post‐dispersal outcomes of animal frugivory interactions may overturn inferences based on consumption observations only. Seed rain patterns are often decoupled from microhabitats' suitability for seedling recruitment. Hence, more integrative studies that encompass the entire plant reproductive cycle (from fruit production to seedling recruitment) are needed to fully understand frugivores' lasting contribution to plant regeneration in natural populations.

Can the native crab Thalamita danae be an effective biological control agent of the invasive mussel Xenostrobus securis in Hong Kong?

AbstractLocal predators are often considered effective and environmentally-friendly control agents to limit invasive species. Such biological control, however, depends on both the predator prey preferences and performances, which are in turn affected by variations in the physical environment. This study investigated the predation of the swimming crab Thalamita danae on the invasive mussel Xenostrobus securis under different salinity and thermal conditions. Xenostrobus securis, which is native to Australia, has spread to Hong Kong since the last decade, causing adverse ecological and economic impacts. Laboratory experiments evaluated the prey preferences and feeding behaviours of the crab on both the native mussel Brachidontes variabilis and the invasive X. securis under different typical salinities (15, 25, and 35‰) and temperatures (22 and 28 °C). The crab did not show clear preference toward either the invasive or the native mussels. Although the shell morphology of the invasive mussels lowered handling time as compared to the native mussels, the crab consumption rate was similar between the mussel species. The survival and predation rate of the crab were, however, substantially reduced under low salinities (< 15‰) where X. securis could be found. Thalamita danae, therefore, is a potential predator of X. securis, but such predation is only possible under normal, oceanic conditions. In hyposaline, estuarine/ freshwater environments where X. securis can survive, however, T. danae performs poorly and, as a result, such physical conditions may represent a predator refuge for the mussels to invade local ecosystems.

Exploring polymorphism in a palatable prey: predation risk and frequency dependence in relation to distinct levels of conspicuousness.

Camouflage and warning signals are different antipredator strategies, which offer an excellent opportunity to study the evolutionary forces acting on prey appearance. Edible prey often escape detection via camouflage, which usually leads to apostatic selection favoring rare morphs. By contrast, defended prey often display conspicuous coloration acting as warning signals to predators, which usually leads to positive frequency dependence and signal uniformity. However, when two morphs of the same species vary greatly in conspicuousness, the maintenance of both cryptic and conspicuous forms in profitable prey populations remains enigmatic. Using the white and melanic morphs of the invasive box tree moth (Cydalima perspectalis) presented at three different frequencies, we investigate (a) the palatability of caterpillars and adult moths to birds, (b) predation rates on the less conspicuous melanic morph, and (c) the role of frequency dependence in balancing morph frequencies. Our results show that caterpillars are distasteful for birds but not adult moths that are fully palatable. We found that the less conspicuous, melanic morph, benefits from reduced predation due to its lower detectability. The more conspicuous, white morph, instead, is more predated and is best off when common, suggesting positive frequency dependence. These results offer new insights into the evolution of color polymorphism and prey defenses in a polymorphic moth species. Further investigation is required to understand the role of different predation regimes on the maintenance of the polymorphism in this species and test whether additional selection pressures operate in natural populations.

High densities of large tuaki, the New Zealand cockle Austrovenus stutchburyi, provide a post-settlement predation refuge for conspecific juveniles

Bivalves are ecosystem engineers, and their effective management relies on a full understanding of the mechanisms that influence population dynamics. Juvenile tuaki (New Zealand cockle) Austrovenus stutchburyi, a numerically dominant and ecologically important bivalve in New Zealand estuaries, were found at higher densities when surrounded by high densities of large adults within Waitati Inlet, in southern New Zealand. Consequently, we hypothesised that adults provided a refuge from predation for juveniles, resulting in higher juvenile survival and retention in dense beds. The observed pattern was consistent with post-settlement Allee effects, where declines in density and truncated size distributions may have resulted in unsuccessful recruitment if a density threshold was reached. Field experiments were undertaken in 2020 and 2021 to test the potential sheltering effect of adults on retention and survival of juveniles, with and without the addition of organic loading of sediments. Presence of adults had significant effects on juvenile retention and interaction with organic loading in 2020, but not in 2021. To isolate the effects of adult presence on predation of juveniles, a series of laboratory experiments were carried out using the predatory crab Ovalipes catharus. Juvenile survivorship from crab predation was enhanced in the presence of large adults, consistent with the hypothesised sheltering effect. Further, predation rates increased significantly from winter to summer, which correlated with increasing water temperatures and the breeding and moult cycle of crabs. These findings across surveys, field and laboratory manipulations have significant implications for effective fisheries management and restoration of bed-forming bivalves.

A Potantial Nesting Site for Loggerhead Turtle (Caretta caretta): Yakacık Beach, Türkiye

Monitoring of sea turtle nesting beaches in Türkiye have been conducted since 1988 and the number of beaches reached to 22. Mediterranean coast of Türkiye has many small pocket beaches and other inaccessible remote sandy beaches. In this study, I introduce a new nesting site, Yakacık Beach, for the loggerhead turtles (Caretta caretta) in the border of Antalya and Mersin provinces. Following the preliminary field studies on the 1.7 km long beach, 201 and 197 nests were found in 2020 and
 2021, respectively, and the average nest density of the two years was calculated as 117.6 nests/km-1. Satellite images were also used to ensure and estimate the number of nests. The number of nest and the nest density were compared with the literature and Yakacık has the second highest nest density in Türkiye with a high predation rate up to 68%. The potential importance of Yakacık Beach and threats to the nesting beach and mitigation measures were discussed. Türkiye has one of the most important
 nesting sites for the loggerhead turtles and the green sea turtles (Chelonia mydas) in the Mediterranean, with 17 nesting beaches identified in 1989. With the discovery of additional nesting sites such as Çıralı, Alata, Sugözü, Davultepe, and METUKocahasanlı beaches in the following years, the importance of Türkiye for sea turtle populations in the Mediterranean has gradually increased. With this study, a new nesting beach was identified and the importance of Türkiye for the Mediterranean Sea turtles was emphasized.

Nature's Solution to Aedes Vectors: Toxorhynchites as a Biocontrol Agent.

This review summarizes the predatory potential of Toxorhynchites mosquitoes as biological control agents for Aedes vectors. A single larva can consume hundreds of mosquito larvae during its development, with preference for larger prey and higher consumption rates at higher prey densities. Studies suggest Toxorhynchites can significantly reduce Aedes populations. Beyond direct predation, they may indirectly influence prey behavior and adult mosquito lifespan. Despite the demonstrably positive effects of Toxorhynchites species as biocontrol agents, there are acknowledged limitations that require further investigation. These limitations include potential variations in effectiveness across diverse habitats and mosquito developmental stages. Additionally, long-term ecological sustainability and potential ramifications warrant further research. Future efforts should prioritize optimizing rearing and release strategies to enhance effectiveness. Exploring the potential for combined control methods with other biocontrol agents or traditional methods is also crucial. Finally, investigating the influence of environmental factors on predation rates can further refine and optimize the application of Toxorhynchites in mosquito control programs.