Population Dynamics Parameters Research Articles

Stock assessment of rosy barb, Pethia conchonius (Hamilton, 1822) in Dal Lake of Kashmir Himalayas

For management of fish stocks, assessing the various parameters of population dynamics are regarded as being extremely important. Under this backdrop the population dynamics parameters viz. growth, mortality and recruitment of Pethia conchonius, inhabiting the Dal Lake of Kashmir Himalayas were analysed using FiSAT II software. The analysed specimens were collected from five different sites within the lake and exhibited a total weight range of 0.3 to 6.4 g and a total length range of 3.1 to 7.8 cm. The relative condition factor for the fish was reported to be 1.11. The growth parameter i.e., asymptotic length, age at zero length, growth performance index and growth constant were reported to be 10.0 cm, –0.75 years, 1.48 and 0.30 year–1 respectively. The total mortality of 1.49 year–1, consisting of natural mortality of 0.88 year–1 and fishing mortality of 0.61 year–1 was reported. An exploitation rate of 0.41 is suggestive of a less exploited state of the fish. The length at first maturity was found to be higher than the length at first capture, a condition that can disturb the stock, as such the utility of a net with relatively larger mesh size is advisable. The current research on the population dynamics of P. conchonius can be used as the baseline data for its management practices.

Interactive Effect of Cover Crop, Irrigation Regime, and Crop Phenology on Thrips Population Dynamics and Plant Growth Parameters in Upland Cotton

Interactive Effect of Cover Crop, Irrigation Regime, and Crop Phenology on Thrips Population Dynamics and Plant Growth Parameters in Upland Cotton

Population Dynamics Parameters and Exploitation Status of 55 Commercial Species in Egyptian Red Sea Fisheries: A Key to Sustainable Fisheries

Egyptian Red Sea fisheries face the same challenges as most of the world’s fisheries, including overexploitation, habitat loss, IUU fishing, pollution, and climate change. These fisheries are highly diverse with multiple species targeted by multiple fleets, using different fishing gears. Much work has been performed in recent years to assess Red Sea fish stocks. However, not all fish stocks in the Egyptian Red Sea are assessed, and those that are assessed only cover 30% of landings. The assessments are unbalanced by area, with the Gulf of Suez being much better covered than the southern Red Sea and Gulf of Aqaba. The results show that most of the analyzed stocks are overexploited. There is an urgent need to take action to protect, conserve, and restore the different fish stocks in different fishing grounds. These actions will ensure the sustainability of the fisheries, making them ecologically friendly and economically and socially efficient.

Rigorous assessment of a unique tiger recovery in Southeast Asia based on photographic capture-recapture modeling of population dynamics

Tigers and other large predatory carnivores have suffered population extirpations and range contractions. This is particularly true for tiger populations in southeastern Asia, which harbours one-third of their remaining habitats. In stark contrast, a sustained recovery of a wild tiger population has occurred between 2007 and 2023, in three reserves of Thailand: Huai Kha Khaeng (HKK), Thung Yai East (TYE) and Thung Yai West (TYW), which together cover 6470 km2 (36%) of the larger Western Forest Complex (WEFCOM). We quantitatively monitored this recovery employing closed and open model analyses of data from photographic capture-recapture sampling. The resulting estimates of tiger population dynamic parameters showed: mean (±SE) tiger abundance annually varied from 36 (1.0) to 79 (1.53) in HKK, 2 (0.26) to 20 (4.45) in TYE and 3 (0.26) to 44 (2.11) in TYW, driven by mean annual survival rates of 0.79 (0.02) in HKK, 0.72 (0.05) in TYE, and 0.69 (0.05) in TYW. The annual numbers of recruits fluctuated from 0 (1.69) to 33 (1.93) tigers in HKK, 0 (0.47) to 13 (0.57) in TYE and 0 (1.13) to 36 (2.28) in TYW. Overall, the mean tiger population densities/100 km2 ranged between 1.3 (0.19) and 2.9 (0.29) in HKK, 0.2 (0.08) and 1.8 (0.34) in TYE, and 0.2 (0.07) and 3.1 (0.56) in TYW. Generally, the tiger population trended upward, with reserves protected over longer periods leading the tiger recovery. Our results are further backed by ancillary records on births of 67 cubs, 47 tiger dispersal events, as well as the recovery corresponding with incremental spatio-temporal coverage by the patrols. Cumulatively, our results provide evidence that effective law enforcement should be a critical component for achieving tiger population recoveries in Asia. Alternative conservation strategies that ignore this component do not appear to be evidence-based. Our results also demonstrate the utility of the independent collaborative monitoring framework adopted by the Thailand Government.

First evidence of recruitment in critically endangered Galápagos pink land iguanas (Conolophus marthae)

AbstractWe present the first estimate of population dynamics parameters for critically endangered Galápagos pink land iguanas, Conolophus marthae, leveraging mark‐recapture data collected between 2006 and 2021. Demographic parameters were estimated using the POPAN formulation of the Jolly–Seber model. This approach provided a solid and robust estimate, consolidating the results obtained from previous estimates based on the Lincoln–Petersen method evaluating only two sampling occasions. Our results suggest that the abundance of males was higher than that of females at each sampling occasion, probably due to differences in sex‐specific behavior during the reproductive season. Our analyses also provide no evidence of a change in population size during the sampling period, estimated at 150–270 adult individuals, while suggesting positive entry rates. Finally, by comparing the biometric features of first‐captured versus recaptured iguanas, we found that the former have more juvenile‐like characteristics (i.e., they are, on average, smaller) than the latter. Although juvenile pink iguanas have rarely been recorded (only four sampled juvenile‐like individuals in over 16 years of field work), our combined results provide the first clear indication that the only known C. marthae population actively recruits new members from younger age classes. Such recruitment may have prevented any measurable population decline in the last 16 years, but it was also not sufficient to clearly increase the population size. These results are of the utmost importance for the conservation of this species. They will guide future high‐priority actions: (i) aiming at increasing population size by removing or mitigating threats and (ii) increasing the number of individuals by implementing a headstart program and/or founding a second viable population, as identified in the recently published IUCN Conservation and Management Plan.

Population dynamics of Variola albimarginata Baissac, 1953 and Variola louti Fabricius, 1775 (Perciformes: Serranidae) in Sulawesi Sea, Indonesia

Abstract. Achmad DS, Nurdin MS, Tilome AA, Moore AM. 2024. Population dynamics of Variola albimarginata Baissac, 1953 and Variola louti Fabricius, 1775 (Perciformes: Serranidae) in Sulawesi Sea, Indonesia. Biodiversitas 25: 978-989. The lyretail groupers Variola louti Fabricius, 1775 and Variola albimarginata Baissac, 1953 (Epinephelinae) are valuable foodfishes. IUCN Red List assessments classified both species as Least Concern, while noting that some stocks are overfished. The purpose of this study on the population dynamics of Variola groupers in Kwandang Bay was to evaluate the exploitation level for both species in this important grouper fishing area of the Sulawesi Sea, Indonesia. Population dynamics parameters were calculated based on length-frequency data collected from October 2022 to September 2023 using the ELEFAN I response surface analysis option in FISAT II. The asymptotic length at infinity TL? was 54.90 cm for V. louti and 54.40 cm for V. albimarginata with von Bertalanffy growth function K values 0.54 and 0.55, respectively. Recruitment occurred throughout the year, with monthly percentages of 1.08-13.52 % and 1.61-14.99%, respectively. Natural and fishing mortality were M = 1.04/year-1 and F = 1.17/year-1 for V. louti and M = 1.05/year-1 and F= 2.56/year-1 for V. albimarginata giving F/M ratios of 1.13:1 and 2.44:1. Beverton and Holt yield per recruit analysis gave exploitation rates (E = 0.53/year-1 and E = 0.71/year-1) exceeding the maximum sustainable value Emax = 0.37/year-1, indicating overexploitation of both species. To achieve the optimum exploitation rate of E50 = 0.24, fishing effort needs to be reduced by 29% for V. louti and 47% for V. albimarginata. Management options include setting a minimum legal size with recommended values of 32-33 cm and temporary closures during the peak reproductive season in May-June.

Annual survival rates of satellite-tracked adult European honey buzzards (Pernis apivorus) based on the Kaplan-Meier estimator and its probabilistic extension

Abstract The annual survival rate of adult raptors is an important parameter in population dynamics and is needed to derive measures for population stability and conservation management. Here we studied adult European honey buzzards (Pernis apivorus), a migratory land bird, using satellite telemetry throughout the year for up to three years. We used the Kaplan-Meier method of survival estimation in combination with the distribution density function for survival. This function describes the number of survivors N as a function of time t, based on the survival rate SR. This probabilistic extension of the Kaplan-Meier estimator results in a simple method that does not require a commercial statistical program to extract survival rates from event time analysis. It can be applied to analysing any event-time data, not only telemetry results but also ring recoveries, as demonstrated using European honey buzzards as an example. The average adult survival rate in our study, based on permanent satellite telemetry monitoring, was 0.44/year (linear correlation factor f = 0.99). This implies an adult mortality rate of 0.56 per year. It seems that particularly unfavourable weather conditions during the crossing of the Sahara and the Mediterranean led to this high mortality rate of our birds during migration from 2001 to 2011, but is likely to vary greatly from year to year. However, the loss rate in the wintering area was also high, at one third of the birds. More honey buzzards need to be tracked throughout the year to assess factors affecting survival and threats to populations adequately.

Population Dynamics of Gudusia chapra (Hamilton, 1822) from Lake Kaptai, Bangladesh

Aims: This study aimed to assess the population dynamics of Gudusia chapra in Lake Kaptai, Bangladesh, utilizing FiSAT II software for comprehensive analysis. The key objective was to determine growth parameters, mortality rates, exploitation status, and length-weight relationships to inform policy.
 Study Design: The study employed a quantitative approach, utilizing length frequency data collected from Lake Kaptai. FiSAT II software facilitated the estimation of population dynamics parameters, employing the Von Bertalanffy growth equation and other relevant analyses.
 Place and Duration of Study: The research was conducted in Lake Kaptai, Bangladesh, focusing on the intricate aquatic ecosystem from November 2003 to October 2004. Data collection and analysis spanned an extensive duration, providing a robust understanding of the population dynamics of G. chapra.
 Methodology: FiSAT II software was utilized for population dynamics estimation, with a particular focus on growth parameters, mortality rates, and exploitation status using Von Bertalanffy growth equation. Length-weight relationships were also determined. Recruitment patterns were observed, and key indices, including the growth performance index calculated.
 Results: The estimated asymptotic length (L∞) and growth coefficient (K) of G. chapra were found to be 19.95 cm and 0.89 year-1 respectively. Natural mortality (M), fishing mortality (F) and total mortality (Z) rates were 1.85, 2.21 and 4.06 year-1 respectively. The exploitation rate (E) indicated overfishing, with a value of 0.54, which exceeded the optimum E (E=0.5). The growth performance index (φ´) of 2.54 was recorded, and the recruitment pattern occurred between April and July.
 Conclusion: The study concludes that G. chapra in Lake Kaptai is experiencing overfishing, as indicated by the elevated exploitation rate. Understanding the growth parameters and mortality rates is vital for sustainable fisheries management in the region.
 Implication: The findings have significant implications for fisheries management, highlighting the urgent need for measures to mitigate overfishing of G. chapra in Lake Kaptai. Implementing conservation strategies and monitoring recruitment patterns are crucial for ensuring the long-term sustainability of this important fish species.

Population Dynamics of Indian Makerel (Rastrelliger kanagurta) in Northern Bone Bay Waters, Indonesia

This study aims to analyze the parameters of Rastralliger kanagurta population dynamics in the waters of Northern Bone Bay. To analyze the parameters of population dynamics, measurements were made of the total length of the sample fish in centimeters. The research was conducted in March – September 2022 at the Palopo City Pontap Fish Landing Site. Sampling is carried out every two weeks. The results of the growth parameter analysis obtained each value of growth coefficient = 0.84 per year, asymptotic length = 30.5 cm and to = -0.189 years. Furthermore, for mortality parameters, natural mortality was obtained at 1.64 per year, capture mortality = 2.47 per year, and total mortality at 4.11 peryear and exploitation rate at 0.6%. The results show that the growth rate of Rastralliger kanagurta is very high and can reach maximum length at a relative age of 15 years. Mortality parameters show that Rastralliger kanagurta mortality in northern Bone Bay waters is higher from fishing than natural mortality. The exploitation Rastralliger kanagurta in the waters of northern Bone Bay is 60% greater than the maximum exploitation rate of 50%. Based on the results of this study, management of fishery resources is needed so that the population is not disturbed.

Stock assessment using spawning potential ratio in data poor fisheries for mahseer Tor tambroides (Bleeker, 1854) in Aceh Province, Indonesia

Abstract. Haser TF, Nurdin MS, Supriyono E, Prihadi TH, Febri SP, Persada AY, Wibowo TH, Sari HPE, Putri KA, Antoni. 2023. Stock assessment using spawning potential ratio in data poor fisheries for mahseer Tor tambroides (Bleeker, 1854) in Aceh Province. Biodiversitas 24: 6039-6047. Overexploitation of mahseer has led to a decline in population, posing a threat to its sustainability in the wild. Therefore, this study aimed to compare the length-based spawning potential ratio of the fish from Atu Suasah and Lawe Melang Rivers in Aceh Province. The experiment was conducted from January to August 2023, and the population dynamics parameters were calculated through Response Surface Analysis using Electronic Length Frequencies Analysis in the Fish Stock Assessment Tools program. Meanwhile, the spawning potential ratio (SPR) was analyzed based on data uploaded to the Barefoot Ecologist's Toolbox. The results showed that the asymptotic length (L?) at Atu Suasah and Lawe Melang Rivers was 750 mm and 759 mm, respectively, with K coefficients of 1.40 year-1 and 1.55 year-1. The length at first maturity (Lm50) of mahseer in these rivers was 372.52 mm and 438.88 mm. Total mortality (Z) is 3.88 year-1 and 3.24 year-1, while natural mortality (M) values are 1.06 year-1 and 0.91 year-1, with corresponding fishing mortality (F) rates of 2.82 year-1 and 2.33 year-1. The Beverton and Holt analyzes of per recruitment results showed that mahseer in Lawe Melang and Atu Suasah River have exceeded Emax, where the current E values ??were 0.73 year-1 and 0.72 year-1 respectively. These implied that mahseer stock was overfished with SPR 9% and 16% respectively, falling below the standard biological reference point. To ensure sustainability, conservation efforts should be put in place, including establishing a capture size limit and reducing fishing gear by 42%.

Population Dynamics of Yellow Prawn (Metapenaeus monoceros) Captured at Night in the Waters of Samboja Kuala, Kutai Kartanegara Regency

Samboja Kuala is one of the Kelurahan in Samboja District which is an area where most of the population works as fishermen. There are two types of fishery activities in the Samboja Kuala area, namely capture fisheries (fishermen) and aquaculture fisheries. One of the most common catches obtained by fishermen is shrimp. Yellow-spotted shrimp (Metapenaeus monoceros) is one of the catches of fishermen shrimp in Samboja Kuala Waters. This study aims to determine several parameters of population dynamics using the carapace length data frequency method. The research was conducted in Samboja Kuala waters, Kutai Kartanegara Regency, in November-December 2022. Based on the results of the study, the sex ratio between males and females was 0,38: 2,65. The length range in male and female sex is 48,34 mm – 78,85 mm and 48,80 mm – 90,78 mm. And the natural mortality (M) of males and females was 1,27 per year and 1,65 per year, the capture mortality (F) of males and females was 0,63 per year and 1,64 per year, the total mortality of males and females was 1,90 per year and 3,29 per year, and the exploitation rates of males and females were 0,33 and 0,50. New additions of males occurred in October by 16,27% and new additions of females occurred in October by 24,93%. And it is known that the yield per recruitment value is 0.04 grams / recruitment.

Adaptability of Toxoptera aurantii (Hemiptera: Aphididae) to Different Tea Cultivars

The adaptability of phytophagous insects to different host plants is a key determinant of their population propagation. Understanding the feeding behaviour and population dynamics of insects is crucial for elucidating host adaptability and screening for insect-resistant germplasms. Here, we investigated Toxoptera aurantii (Hemiptera: Aphididae) adaptability using electropenetrography and assessed its population growth on seven tea cultivars: Huangjinya (HJY), Qianmei601 (QM601), Fudingdabaicha (FD), Longjing43 (LJ43), Qiancha1 (QC1), Qiancha8 (QC8) and Qiancha10 (QC10). The results showed that the feeding behaviour of T. aurantii differed significantly depending on the tea cultivars. The initial probing of T. aurantii on HJY was the earliest among the seven host plants. Aphids on QC1 and QC10 displayed an increased duration of stylet probing and decreased ingestion of phloem sap, whereas a contrasting trend was observed for aphids on HJY. In addition, the mechanical resistance of T. aurantii fed on HJY and QM601 during the probing phase was significantly lower than that of aphids fed on other cultivars. Population dynamic parameters revealed that the growth rate of T. aurantii reared on HJY was the fastest, and its population quantity within 15 days was markedly higher than that of aphids fed on other cultivars. These findings demonstrate that HJY is the most suitable host plant, whereas QC1 and QC10 are less suitable hosts for T. aurantii, although the aphids successfully survived on all the selected tea cultivars. Our results provide valuable information for the biological control of T. aurantii using resistant tea varieties.

Population dynamic parameters, economic evaluation of Crayfish (Procambarus clarkii) and value added of its shells from River Nile, Egypt

Population dynamic parameters, economic evaluation of Crayfish (Procambarus clarkii) and value added of its shells from River Nile, Egypt

Population dynamics of thresher shark (Alopias pelagicus) landed at the Kutaraja fishing port, Banda Aceh

At the Kutaraja Fishing Port, the shark species Alopias pelagicus accounts for the vast majority of shark catches. The purpose of this research was to ascertain the length distribution of A. pelagicus, the length at which it was first captured, the sex ratio, the von Bertalanffy growth parameters and functions, the mortality rate, and the exploitation rate. This study was carried out in the Kutaraja Fishing Port from December 2021 to February 2022. The incidental sampling method was used to collect 406 samples in total. The FAO-ICLARM Stock Assessment Tools were utilized to analyze population dynamics parameters. The male, female, and combined length distributions of A. pelagicus ranged from 186-295cmTL, 205-304cmTL, and 186-305cmTL, respectively. The length of the first capture was 249.40 cmTL, 252.29 cmTL and 250.78 cmTL, sex ratio of males and females is 1:2.24, the asymptotic length (L∞) was 344.25 cmTL, fish age at length 0 (t0) was 0.066/year, with a growth rate (k) of 0.50/year, 0.36/year dan 0.19/year, 374.83 cmTL and 378.92 cmTL, 0.058/year dan 0.048/year. Natural mortality (M) was assessed to be 0.59/year, 0.47/year, and 0.31/year, fishing mortality (F) was 2.08/year, 2.47/year, and 2.20/year, and total mortality (Z) was 2.67/year, 2.94/year, and 2.51/year. The A. pelagicus exploitation rate (E) was 0.78/year, 0.84/year, and 0.88/year, demonstrating complete exploitation of the male, female, and combined populations.

Estimation and analysis of insect population dynamics parameters via physiologically based models and hybrid genetic algorithm MCMC methods

Decision support systems are gaining importance in several fields of agriculture, forest, and ecological systems management. Their predictive potential, entrusted to mathematical models, is of fundamental importance to set up opportune strategies to control pests and adversities that may occur and that may seriously compromise the natural equilibria. Among the others, population dynamics is one of the crucial challenges in the field. Despite the scientific community in recent years providing valuable models that faithfully represent terrestrial arthropods populations, such as insects, one of the main concerns is still represented by the parameter estimation. Parameters, in fact, characterise the species and their estimation are often entrusted to dedicated laboratory experiments that require specific equipment and highly qualified personnel. In this study we propose a novel method to estimate the model parameters directly from field data, where experimental activities are less expensive and less time consuming. In this study we propose a combination of least squares methods via genetic algorithms to preliminary evaluate the best parameter values and Markov Chain Monte Carlo approach to obtain their distribution. The algorithm has been tested in the special case of Drosophila suzukii, to quantify part of the parameters of an almost validated model in two steps: i) a first pseudo-validation using perturbed numerical solutions, and ii) a validation using real field data. The results highlighted the potentialities of the algorithm in estimating model parameters and opened several perspectives for further improvements from both the computational and experimental point of view.

Population Dynamics of Jinga Shrimp (Metapenaeus affinis) in Samboja Kuala Waters Kutai Kartanegara Regency

Pink shrimp (Metapenaeus affinis) or Jinga shrimp is one of the species caught in the waters off Samboja Kuala. This catch is a valuable commodity in the market. The possibility of exploiting shrimp resources will be jeopardized in an effort to conserve, utilize, and catch high intensity shrimp. This study was conducted from September to December 2022 with the aim of determining population dynamics parameters using the frequency method from carapace length data. A mini trawl was used to collect shrimp in the waters of Samboja Kuala, Kutai Kartanegara Regency. Male and female jinga shrimp have a ratio of 1:2,43. Furthermore, for male and female shrimp, the growth rate coefficient (K) was 0,580 and 14,00, respectively, and the approximated natural length (L) was 145.82 and 160.81. Pink shrimp (Metapenaeus affinis) have natural mortality (M) of 1,113/year, mortality due to capture (F) of 0,516, and total mortality (Z) of 1,630, with exploitation value (E) of 0,316, indicating that they are still at the appropriate level. Herefore, female shrimp peaked in August at 14,6% and males peaked in July 31,81%. The Y/R capability was 0,049/year, and Emax calculated the Y/R relationship with the exploitation rate, which was 0,42.

Population dynamics and yield estimation of Common Carp (Cyprinus carpio, Linnaeus, 1758) in Ayalew reservoir, Gamo Zone, Southern Ethiopia

Common carp (Cyprinus carpio) is an introduced fish species in Ayalew reservoir. This study provides the first results on fishery dynamics of the species in the reservoir. The study was aimed at estimating important population dynamics parameters and production potential. Total length (TL) and total weight (TW) data were collected from a total of 276 fish samples (141 females and 135 males). The obtained data were analyzed using FiSAT II software. Jones length-based cohort analysis model and length-based Thompson and Bell yield prediction models were employed to estimate the population and production potential. The mean total length was 26 cm and the dominant length groups ranged from 17 to 33 cm were 87%. The length-weight relationship parameters were (TW = 0.0565TL2.53, R2 = 0.95) and the condition factor K = 1.29. The parameters of von Vertalanffy growth curve were L∞ = 41 cm, k = 0.52, to = -2.29, θ = 2.9 and A0.95 = 5.5 years. The estimated values of the total, natural and fishing mortalities were Z = 1.23, M = 0.55 and F = 0.68, respectively. The current exploitation rate was 0.55 which indicates slightly overexploitation. The estimated fish population and the annual fish yield were 59,304 and 1.5 tons, respectively. However, investigation on reproductive biology, limnolocal aspects and stock enhancements should be required for the sustainability of these resources.

Trophic structure using ecological relationships between five dominant commercial fish in Kolahi to Dargahan

AbstractThe purpose of this study was to determine the effects of frequent species population fluctuations and the impact of different rates of exploitation on other ecological links in the food web. The mass‐balanced Ecopath model represents the trophic interactions among the 31 defined functional groups in the Kolahi to Dargahan area, with five main species, including Trichiurus lepturus, Saurida tumbil, Nemipterus japonicus, Sillago sihama, and Cynoglossus arel (from April 2018 to April 2019). To investigate the effects of fishing and environmental disturbances, the Ecopath modeling approach combines software for analyzing ecosystem trophic‐level balances with population dynamic models. In the past 5 years, Hormozgan province has caught more than 45% of the benthic fish caught off the northern coasts of the Persian Gulf. From Kolahi to Dargahan, one of the most important fishing grounds in this province's southeast is located. Food web models are used to represent a marine system's current state, assess stock levels, and predict change over time. Over a year, the first five dominant fish in the study area, S. tumbil, S. sihama, C. arel, N. japonicus, and T. lepturus, were biometrically measured, and their population dynamics parameters as well as feeding ecology indices were analyzed. According to the trophic‐level index results, the five most common species studied in this study belonged to the third (N. Japonicas, S. sihama, and C. arel) and fourth (T. lepturus, and S. tumbil) trophic levels. The key species with the greatest impact on other groups of studied species were identified as S. tumbil and T. lepturus, respectively. The estimated ecosystem indicators were the system operational power (75846.797), the primary production/respiration ratio (0.034), the connectance index (0.159), and the system omnivory index (0.253). A pedigree index (PI) of 0.38 was estimated for the present model. Overexploitation of T. lepturus could disrupt the aquatic food web and adversely affect the long‐term sustainable use of aquatic resources, according to data. As a result, ecosystem‐based fisheries management should be implemented to find a more appropriate solution to sustainable exploitation in the studied habitat, an important fishing area in the Persian Gulf's north.

Additive Effect of Releasing Sterile Insects Plus Biocontrol Agents against Fruit Fly Pests (Diptera: Tephritidae) under Confined Conditions.

Pest control models integrating the use of the sterile insect technique (SIT) and augmentative biological control (ABC) have postulated that it is possible to obtain a synergistic effect from the joint use of these technologies. This synergistic effect is attributed to the simultaneous attack on two different biological stages of the pest (immature and adult flies), which would produce higher suppression on the pest populations. Here we evaluated the effect of the joint application of sterile males of A. ludens of the genetic sexing strain Tap-7 along with two parasitoid species at the field cage level. The parasitoids D. longicaudata and C. haywardi were used separately to determine their effect on the suppression of the fly populations. Our results showed that egg hatching percentage was different between treatments, with the highest percentage in the control treatment and a gradual reduction in the treatments with only parasitoids or only sterile males. The greatest induction of sterility (i.e., the lowest egg hatching percentage) occurred with the joint use of ABC and SIT, demonstrating that the earlier parasitism caused by each parasitoid species was important reaching high levels of sterility. Gross fertility rate decreased up to 15 and 6 times when sterile flies were combined with D. longicaudata and C. haywardi, respectively. The higher parasitism by D. longicaudata was determinant in the decrease of this parameter and had a stronger effect when combined with the SIT. We conclude that the joint use of ABC and SIT on the A. ludens population had a direct additive effect, but a synergistic effect was observed in the parameters of population dynamics throughout the periodic releases of both types of insects. This effect can be of crucial importance in the suppression or eradication of fruit fly populations, with the added advantage of the low ecological impact that characterizes both techniques.

High-Voltage Electrostatic Fields Adversely Affect the Performance of Diamondback Moths over Five Consecutive Generations

Changing electrical environments can influence the performance of herbivorous insects and adversely affect their control strategies. The diamondback moth, Plutella xylostella (L.), is a pest that devastates cruciferous vegetables. An age–stage, two-sex life table of P. xylostella over multiple generations was established to describe the effect of varying high-voltage electrostatic field (HVEF) exposure on their performance after the age-cohort eggs were exposed to HVEF at an intensity of 5.0 kV/cm for different durations. The results show that direct HVEF exposure adversely affected the population dynamics parameters of P. xylostella over multiple generations. In particular, the net reproduction rate, intrinsic natural increase rate, and finite increase rate of the P. xylostella population significantly decreased in the third and fifth generations under HVEF exposure for 10 min, while the mean generation time and doubling time significantly increased. Similarly, HVEF exposure for 10 min rapidly reduced the survival rate of adult P. xylostella in the first generation, and subsequently, it declined evenly and slowly. Meanwhile, the fecundity parameters of P. xylostella revealed that HVEF exposure for 10 min had the strongest inhibition effect on reproduction over five consecutive generations. In addition, HVEF exposure significantly increased the superoxide dismutase activity to produce extra hydrogen peroxide; however, increased catalase and peroxidase activity or reduced peroxidase activity triggered the accumulation of malondialdehyde in instar P. xylostella, especially after 10 min of treatment. The present findings provide experimental evidence and a theoretical basis for developing control strategies for P. xylostella under new HVEF environments.