Life History Parameters Research Articles

A bone to pick with age estimation using hard parts: A case study of swordfish, Xiphias gladius, in the southwest Pacific Ocean

Life history parameters of fish can vary spatially, and these differences have been used to identify separate stocks for management. However, inconsistency in the methods used to obtain the parameters is often overlooked as a possible explanation for the variability in parameters. Here, we sought to understand whether large differences in growth parameters obtained for broadbill swordfish (Xiphias gladius) in the southwest Pacific Ocean and central Pacific Ocean were due to methodological differences in estimating age, and to evaluate the most appropriate hard part for providing annual age estimates. Sectioned anal fin rays were obtained from an earlier study undertaken in the southwest Pacific (1995–2003) and the assumed annuli were re-counted for a subset, using criteria confirmed through an inter-laboratory calibration exercise. Sagittal otoliths were also obtained from the same study (in which otoliths had been collected but annual age had not been estimated) and the assumed annuli present in transversely sectioned otoliths were counted using new criteria for reading growth zones. Ray-based growth curves were different to the curves obtained in the original 1995–2003 study, confirming that methodological differences exist among studies that use fin rays in the Pacific. More importantly, a direct comparison of the new age estimates from fin rays and otoliths showed a clear bias; ray age was lower on average than otolith age for females > 7 years and males > 4 years. Considering that otoliths have been shown to be more reliable than alternative hard parts for estimating the age and longevity for many species, the results suggest that swordfish live longer and grow more slowly than previously estimated in the Pacific. A maximum age of 21 years was obtained from otoliths and 14 years from rays. We recommend that protocols are established to ensure that hard part reading methods are standardised among laboratories and that otolith-based age estimation is investigated and validated for all billfish stocks, and potentially other fish species.

The effect of cladoceran, Daphnia magna, on the growth and pupation of Aedes aegypti L. mosquito larvae

BackgroundDengue and chikungunya are two mosquito-borne viruses transmitted by the mosquito, Aedes aegypti, and are responsible for great public health concerns in India. The present study tested the effect of Daphnia magna, a freshwater cladoceran, on the growth and pupation of Ae. aegypti larvae.ResultsAe. aegypti third instar larvae and adult, D. magna, were introduced in the ratios 1:1, 1:2 and 1:3 into beakers and placed in an illuminated BOD incubator at a temperature of 26 ± 1 °C. The delay in the duration of larval stages (the time taken from third instar stage until their emergence as adults) was measured. The emergence of adults was delayed for 3–4 days in the treatments where the ratio of D. magna was thrice the number of Ae. aegypti larvae. The L3 larval stage was found to be more prone to mortality than later instars, with 51.66% larval mortality. The sex ratio of males to females emerged was only 5:5 in the 1:3 ratio. Body size of both males and females was significantly reduced in all the treatment sets in the ratios: 1:1, 1:2 and 1:3 when compared with the control set. Longevity of adult was also reduced from 8–15 to 4–7 days in the case of males, and in the case of females it was reduced from 14–25 to 5–9 days in the treatment set when Daphnia was introduced thrice the number of Aedes larvae.ConclusionsOur study provides evidence that D. magna affects the growth and pupation of Aedes larvae and consequentially the life history parameters that affect the fitness of the population.

Naturally stressed? Glucocorticoid profiles in blubber of blue and gray whales in response to life history parameters.

The goal of the present study was to carry out a thorough methodological validation and describe baseline profiles for glucocorticoid hormones (cortisol and corticosterone) in blubber from blue (n = 77) and gray (n = 103) whales from the eastern North Pacific Ocean. For each species, we modelled cortisol and corticosterone concentrations in response to life history parameters (age, sex, reproductive status) and season or geographic location. In blue whales, cortisol concentrations did not vary significantly by age class, sex, or reproductive status, whereas corticosterone was significantly lower in immature than in adult females (p < .001). In gray whales, cortisol concentrations were significantly higher in lactating whales (p < .05), while corticosterone was significantly different between females and males (p = .001) and elevated in calves (p = .003). In gray whales, corticosterone concentrations were significantly lower in males sampled later in the year (August to November) compared to both sexes sampled between March and August (p = .05), but no seasonal trend occurred in blue whales. Our results indicate that glucocorticoid actions vary between species and sex in large whales. Analysis of multiple hormones improves our understanding of the physiology of maintaining metabolic homeostasis or coping with chronic stressors.

Does a Diet Rich in the Bacterium Rhodopirellula rubra Improve Daphnia magna Performance?

In the wild various organisms contribute to daphnids diet. This study, intendeds to evaluate the potential of the concentration of Rhodopirellula rubra as a single or supplementary food source for Daphnia magna. Feeding assays were performed according to standard guidelines for chronic assays (21 days), and life-history parameters and several biomarkers (protein content, oxidative stress, energetic reserves and pigments) were measured. Five food regimens were conducted with 20 individual replicates (A - R. subcapitata; 0.2 - suspension of R. rubra at 0.2 arbitrary units (AU); 0.4 - suspension of R. rubra at 0.4 AU; 0.2+A - suspension of R. rubra at 0.2+alga; 0.2+A-suspension of R. rubra at 0.4 AU + alga). Additionally, the effects of three diets (A, 0.2, and 0.2+A) on the longevity of D. magna were assessed. The five diets showed a different C, N, and carotenoids composition, with an increase in the mixed diets. The results confirmed that the mixed diets improved D. magna life-history parameters. A decrease in glycogen, and the increase of haemoglobin, protein, and gluthione-S-transferase (GST) were observed. Furthermore, D. magna fed with bacterial single diets, presented worsen life history parameters and a decrease in the protein content. An induction of oxidative stress response (increased catalase and GST), and a significant decrease in lipid peroxidation and an accumulation of glycogen and carotenoids were observed. Overall, an increase in the amount of R. rubra provided to D. magna, from 0.2 AU to 0.4 AU, negatively impacted daphnid performance. No significant effects on Daphnia longevity (a 110-day assay) were observed among the three diets tested. However, a significant survival percentage and fertility (cumulative offspring is more than twice) was observed when D. magna was fed with the mixed diet. Results demonstrated that different diets provided a nutritional diversified food to the daphnids that induced differences in D. magna performance. The mixed diets proved to be beneficial (with increase in offspring) on D. magna performance, independently of the bacterial concentration tested. When in single diet, bacterial concentration is not nutritionally sufficient to raise D. magna even when in increased concentration.

Comparison of ammonia thresholds for survival and reproduction between two copepods: The planktonic calanoid Eurytemora affinis and the benthic harpacticoid Tigriopus japonicus

The planktonic species Eurytemora affinis and the benthic species Tigriopus japonicus are two copepods that are extensively employed in aquaculture operations, especially as a source of live feed during larval rearing. Compared to T. japonicus, E. affinis is difficult to keep in stable cultures and to mass produce, which largely limits its usage. Furthermore, high levels of un-ionized ammonia (NH3−N) can limit the productivity of aquatic organisms. However, the toxicity of NH3-N can be easily affected by environmental conditions. The planktonic and benthic growth features of E. affinis and T. japonicus may reflect different adaptations to NH3−N stress that could affect their reproductive performances. Hence, we investigated the effect of NH3−N on the survival and reproductive patterns of E. affinis and T. japonicus at both the individual and population levels. The median lethal concentrations for both the nauplius and copepodite stages, life history parameters, and population growths of each species were evaluated after acute (24-h) and chronic (21–28 days) NH3−N exposure. The results showed that E. affinis was more vulnerable to NH3−N stress than T. japonicus at all developmental stages. The nauplius and copepodite stages of E. affinis exhibited 14.7- and 33.7-fold lower 24-h LC50 doses, respectively, than those of T. japonicus. Chronic individual exposure to NH3−N concentrations over a specific threshold (≥ 0.2 mg/L for E. affinis and ≥ 14.6 mg/L for T. japonicus) affected survival rates, extended the duration of the nauplius and copepodite stages, and delayed maturation in both species. In contrast, batch culture showed that low concentrations of NH3−N were beneficial to the reproduction of T. japonicus, whereas such a trend was not clearly observed in E. affinis. Finally, we hypothesize that the differences in the NH3−N sensitivities of E. affinis and T. japonicus could be attributed to their evolutionary history in pelagic and benthic habitats, respectively. The low NH3−N tolerance of E. affinis indicates the importance of managing ammonia levels during their cultivation.

Comparative Toxicity and Joint Effects of Chlorantraniliprole and Carbaryl Against the Invasive Spodioptera frugiperda (Lepidoptera: Noctuidae).

Fall armyworm, Spodoptera frugiperda, is one of the most devastating invasive pests in China. Chlorantraniliprole (CH) is currently the main agent for controlling S. frugiperda. Carbaryl (CA) has been widely used as a foliar treatment to control S. frugiperda, although the pest has become highly resistant to it. This study investigates the comparative toxicity and joint effects of CH and CA on S. frugiperda. Time-toxicity results showed that CH had high toxicity to 1st and 3rd instar larvae, whereas CA had very low toxicity to 1st and 3rd instar larvae. The mixtures of CH and CA at different mass ratios showed strong synergistic effects on toxicity, and the mass ratio of 2:1 exhibited the highest toxicity to S. frugiperda. Furthermore, the synergistic toxicity of CH and CA at the 2:1 mass ratio (CH+CA) was also verified in field populations of S. frugiperda. The life-history parameters showed that CH+CA dramatically decreased the survival rate and fecundity of the parent population (F0) compared with CH treatment at the same concentration. Besides, CH and CH+CA mixture showed induction effect on cytochrome P450s and glutathione-S-transferases (GSTs) activities in S. frugiperda, with cytochrome P450s enzyme responding the fastest. In conclusion, this research found CH+CA provided synergistic effects on the toxicity and the sublethal effect on larvae. The joint effects on the life-history parameters and the detoxifying enzymes in S. frugiperda, may be useful for implementing IPM programs against this Lepidoptera pest.

Offshore wind farms affect the spatial distribution pattern of plaice Pleuronectes platessa at both the turbine and wind farm scale

Abstract We investigated how the distribution of plaice Pleuronectes platessa, a typical soft-sediment fish species, has been affected by the introduction of hard substrate [turbines and scour protection layer (SPL)] at both turbine and wind farm scale in two Belgian offshore wind farms (OWFs). Diving transects (40 m) at 11 monopiles revealed four times higher plaice abundances on the sandy patches of the SPL (average radius 16.5 m) compared to the surrounding sand. We suggest that the configuration of the SPL, i.e. an open rock field, offering increased food and shelter opportunities, with sandy patches in between, facilitating the natural burrowing behaviour of plaice, forms the basis for the increased plaice abundances at the turbine scale. At the wind farm scale, beam trawl catches in between the turbines and in reference zones revealed significantly increased plaice abundances in one OWF, which suggests that wind farms can act as refuge areas for plaice, at least under specific conditions. Differences in environmental conditions, turbine foundation type, and surrounding fishing pressure may explain the equivocal findings between both OWFs, whereas low statistical power could have hampered the detection of general refuge effects. Next to the integration of different spatial scales (turbine/wind farm) within one study, longer-term monitoring and including extra life history parameters (e.g. length and sex ratio) might enhance the detectability of potential refuge effects.

Biological parameters, ecology and population trends of the Mediterranean endemic skate, Raja polystigma, in the Balearic Islands

Elasmobranchs are a vulnerable group that has been overexploited for almost half a century in the Mediterranean. However, few elasmobranch species have been assessed because information on their basic biological parameters is lacking for most species. Raja polystigma is a poorly studied endemic skate in the Mediterranean. The aim of this work is to determine some basic life history parameters of this skate in the Balearic Islands. Data were collected from commercial catches and during MEDITS surveys. Total length varied from 17 to 59 cm for both sexes, with a higher proportion of females than males. Allometric and morphometric relationships differed between sexes, females being heavier for a given size. Females matured at a larger size than males (L50 47.7 cm and 38.4 cm, respectively). Potential fecundity ranged between 11 and 45 yolked oocytes per female, and spawning was observed mainly during winter and spring. Persistent hotspots of adults and juveniles were detected on the shallow shelf off the northwest of Mallorca and east of Menorca, with adults being found mainly in the shallow and juveniles in deeper areas. Time series of abundance and frequency of appearance showed stable trends throughout the study period (2003-2018).

Facing the Green Threat: A Water Flea's Defenses against a Carnivorous Plant.

Every ecosystem shows multiple levels of species interactions, which are often difficult to isolate and to classify regarding their specific nature. For most of the observed interactions, it comes down to either competition or consumption. The modes of consumption are various and defined by the nature of the consumed organism, e.g., carnivory, herbivory, as well as the extent of the consumption, e.g., grazing, parasitism. While the majority of consumers are animals, carnivorous plants can also pose a threat to arthropods. Water fleas of the family Daphniidae are keystone species in many lentic ecosystems. As most abundant filter feeders, they link the primary production to higher trophic levels. As a response to the high predatory pressures, water fleas have evolved various inducible defenses against animal predators. Here we show the first example, to our knowledge, in Ceriodaphnia dubia of such inducible defenses of an animal against a coexisting plant predator, i.e., the carnivorous bladderwort (Utricularia x neglecta Lehm, Lentibulariaceae). When the bladderwort is present, C. dubia shows changes in morphology, life history and behavior. While the morphological and behavioral adaptations improve C. dubia’s survival rate in the presence of this predator, the life-history parameters likely reflect trade-offs for the defense.

Toxicity of triphenyl phosphate toward the marine rotifer Brachionus plicatilis: Changes in key life-history traits, rotifer-algae population dynamics and the metabolomic response

Triphenyl phosphate (TPhP) is used as a flame retardant that gradually leaks from products into the marine environment and thus may threaten low-trophic-level marine organisms, such as zooplankton. To assess the effect of TPhP on these taxa, we treated the marine rotifer Brachionus plicatilis as a target and examined the changes in key life history parameters and the metabolome after exposure to TPhP at 0.02, 1 and 5 mg/L. Additionally, the rotifer-Phaeocystis population dynamics (a simulation of the prey-predator relationship) were studied under TPhP stress. Our results showed that TPhP at 1 and 5 mg/L reduced the average lifespan and the total offspring number and prolonged the prereproductive time, suggesting damage to survival and fecundity. In the 0.02 mg/L group, no obvious damage occurred in the overall condition of rotifers, but the volume of parental rotifers after the first brood decreased. This implied that rotifers sacrificed somatic growth to reproduction in the initial period of TPhP exposure at the low concentration. All the tested TPhP concentrations altered the rotifer-Phaeocystis population dynamic changes, especially that 1 mg/L TPhP reduced the ability of rotifers to remove this harmful alga, as evidenced by the decrease in the maximum population density of rotifers and the extended time to P. globosa extinction. At the molecular level, metabolomics identified 84 and 206 differentially expressed metabolites, most of which were enriched in glycerophospholipid metabolism, steroid biosynthesis and sphingolipid metabolism. Nile red staining showed a decrease in neutral lipids in rotifers, further indicating a disorder of lipid metabolism induced by TPhP. Moreover, the balance between ROS production and the defense system was disrupted by TPhP, which contributed to its toxicity. This finding will promote the understanding of the ecological risk and mode of action of TPhP in aquatic environments.

Early life history of the middling thread herring (Opisthonema medirastre) in the central Galápagos Islands.

The authors estimated life-history parameters of a clupeid forage fish, Opisthonema medirastre, by sampling juveniles over the course of a year in the central region of the Galápagos Islands, Ecuador. They collected 160 juveniles on the south coast of Santa Cruz Island during the wet/warm season that were 16-48 mm standard length, were 30-88 days old, had hatched at the beginning of the wet/warm season and had grown at 0.4 mm day-1 . The results suggest that in Galápagos, O. medirastre reproduce during the wet/warm season mostly under neutral ENSO conditions.

Inheritance and Fitness Costs of Vip3Aa19 Resistance in Mythimna separata.

The “high-dose/refuge” strategy is expected to work most effectively when resistance is inherited as a functionally recessive trait and the fitness costs associated with resistance are present. In the present study, a laboratory selected Mythimna separata strain that have evolved >634.5-fold resistance to Vip3Aa19 was used to determine the mode of inheritance. To determine if fitness costs were associated with the resistance, life history parameters (larva stage, pupa stage, pupal weight, adult longevity and fecundity) of resistant (RR), -susceptible (SS) and heterozygous (R♂S♀ and R♀S♂) strains on nontoxic diet were assayed. The LC50 values of R♀S♂ were significantly higher than that of R♂S♀ (254.58 μg/g vs. 14.75 μg/g), suggesting that maternal effects or sex linkage were present. The effective dominance h of F1 offspring decreased as concentration increased, suggesting the resistance was functionally dominant at low concentration and recessive at high concentration. The analysis of observed and expected mortality of the progeny from a backcross suggested that more than one locus is involved in conferring Vip3Aa19 resistance. The results showed that significant differences in many life history traits were observed among the four insect genotypes. In short, resistance to Vip3Aa19 in M. separata was inherited as maternal and multigene and the resistance in the strain was associated with significant fitness costs. The results described here provide useful information for understanding resistance evolution and for developing resistance management strategies.

Spatial modelling for population replacement of mosquito vectors at continental scale.

Malaria is one of the deadliest vector-borne diseases in the world. Researchers are developing new genetic and conventional vector control strategies to attempt to limit its burden. Novel control strategies require detailed safety assessment to ensure responsible and successful deployments. Anopheles gambiae sensu stricto (s.s.) and Anopheles coluzzii, two closely related subspecies within the species complex Anopheles gambiae sensu lato (s.l.), are among the dominant malaria vectors in sub-Saharan Africa. These two subspecies readily hybridise and compete in the wild and are also known to have distinct niches, each with spatially and temporally varying carrying capacities driven by precipitation and land use factors. We model the spread and persistence of a population-modifying gene drive system in these subspecies across sub-Saharan Africa by simulating introductions of genetically modified mosquitoes across the African mainland and its offshore islands. We explore transmission of the gene drive between the two subspecies that arise from different hybridisation mechanisms, the effects of both local dispersal and potential wind-aided migration to the spread, and the development of resistance to the gene drive. Given the best current available knowledge on the subspecies' life histories, we find that an introduced gene drive system with typical characteristics can plausibly spread from even distant offshore islands to the African mainland with the aid of wind-driven migration, with resistance beginning to take over within a decade. Our model accounts for regional to continental scale mechanisms, and demonstrates a range of realistic dynamics including the effect of prevailing wind on spread and spatio-temporally varying carrying capacities for subspecies. As a result, it is well-placed to answer future questions relating to mosquito gene drives as important life history parameters become better understood.

Characterizing the sublethal effects of SmartStax PRO dietary exposure on life history traits of the western corn rootworm, Diabrotica virgifera virgifera LeConte.

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is an economically important pest of field corn (Zea mays L.) across the United States (U.S.) Corn Belt. Repeated use of transgenic hybrids expressing Bacillus thuringiensis (Bt) proteins has selected for field-evolved resistance to all current rootworm-active Bt proteins. The newest product available for WCR management is SmartStax® PRO, a rootworm-active pyramid containing Cry3Bb1, Cry34/35Ab1 [now reclassified as Gpp34Ab1/Tpp35Ab1] and a new mode of action, DvSnf7 dsRNA. Understanding the fitness of adult WCR after dietary exposure to SmartStax® PRO will identify potential impacts on WCR population dynamics and inform efforts to optimize resistance management strategies. Therefore, the objective of the present study was to characterize the effect of SmartStax® PRO dietary exposure on WCR life history traits. Adult WCR were collected during 2018 and 2019 from emergence tents placed over replicated field plots of SmartStax® PRO or non-rootworm Bt corn at a site with a history of rootworm-Bt trait use and suspected resistance to Cry3Bb1 and Cry34/35Ab1. Adult survival was reduced by 97.1–99.7% in SmartStax® PRO plots relative to the non-rootworm Bt corn plots during the study. Individual male/female pairs were fed different diets of ear tissue to simulate lifetime or adult exposure. Life history parameters measured included adult longevity, adult head capsule width, lifetime female egg production, and egg viability. Results indicate that lifetime or adult exposure to SmartStax® PRO significantly reduced adult longevity and lifetime egg production. Larval exposure to SmartStax® PRO significantly reduced WCR adult size. Results from this study collectively suggest that SmartStax® PRO may negatively impact WCR life history traits, which may lead to reduced population growth when deployed in an area with WCR resistance to Bt traits.

Body growth and reproductive parameters of common dolphins from the southwestern Atlantic

AbstractCommon dolphins, Delphinus delphis, in the southwestern Atlantic Ocean are subject to incidental mortality in fishing gear. However, no information on trends in abundance or estimates of bycatch mortality are available to evaluate the impact of this threat on the population. This study presents estimates of life history parameters using postmortem data obtained over a 17‐year period in Argentina. Ages were determined for 93 specimens, and reproductive organ samples were examined (n = 89). Immature animals ranged from 0 to 6 years in females and from 0 to 9 years in males. Mature animals ranged from 7 to 21 years in females and from 6 to 23 years in males. The asymptotic body length (L∞) described by a Gompertz model fit to age‐length data was 196 cm, 95% CI [192.45, 199.76] for females and 210.75 cm, 95% CI [206.64, 215.30] for males and was attained at 14 years in females and 15 years in males. Comparison to other populations showed that L∞ were shorter than estimates from New Zealand, similar to L∞ from eastern North Atlantic, and longer than estimates from North Pacific common dolphins. Lmax reported here were shorter than New Zealand ones but similar to those previously reported from other populations.

Simple length‐based approaches offer guidance for conservation and sustainability actions in two Central American small‐scale fisheries

Abstract Many species targeted by multi‐gear small‐scale fisheries in developing countries are poorly studied in terms of fisheries sustainability even as their contributions to biodiversity, livelihoods, export earnings and food security are well documented. This study presents new information on more than 150 fish species that constitute the bulk of small‐scale fishery landings in Belize and on the Pacific coast of Guatemala to provide guidance for improved biodiversity conservation and fisheries management. This includes a number of species listed as threatened on the IUCN Red List and Appendix II of CITES. Simple, length‐based approaches and thresholds of size at maturity show that many of the elasmobranch and bony fish species examined have many immature individuals landed (Belize 51%, Guatemala 77%) across several gears. In both countries, maximum size is negatively correlated with the intensity of overfishing for several common metrics: proportions of mature, optimal sized and mega‐spawners. The disproportionate removal of the largest species first will have cascading effects on biodiversity, community structure and species interactions, as well as livelihood opportunities and food security for fishing communities. Status indicators, such as fishing mortality rate relative to natural mortality rate and estimates of depletion based on lengths are sensitive to the assumed values of life history parameters, indicating the importance of improved data on growth, maturity and mortality for these populations. Our study emphasizes the use of a combination of fisheries conservation strategies, including size and effort controls, in conjunction with the closed area concept (i.e. marine protected areas) and meaningful consultation with resource users in order to maximize benefits for nature and people.

Forty-year historical analysis of marine mammal strandings in Texas, from 1980 – 2019

Long-term trends in marine mammal stranding patterns can provide useful information on basic life history parameters, spatiotemporal distribution, natural and human-related mortality events, and potentially vulnerable populations. Between 1980 and 2019, a total of 5,301 marine mammal strandings were recorded in Texas, USA. In total, 23 species were identified, including 19 odontocete species (toothed whales and dolphins), 3 mysticete species (baleen whales), and 1 sirenian species (manatee). Common bottlenose dolphins (Tursiops truncatus) stranded most frequently (94%). Six unusual mortality events occurred with causes attributed to disease, harmful algal blooms, or unknown etiologies. Common bottlenose dolphin stranding events increased significantly in late winter/early spring, with an early onset in southern Texas, and had a consistent peak in March involving primarily calves and adults. Spatial analyses using kernel density estimation within seven coastal Texas stock management areas, delineated by the National Marine Fisheries Service, identified potential hotspots for common bottlenose dolphin strandings near higher human population density and deep water channels. Peak stranding density estimates in each stock area ranged from 0.32 – 4.6km-2 for presumed bay, sound and estuarine (BSE) stocks and 0.82km-2 for the presumed Western Gulf of Mexico Coastal Stock. Common bottlenose dolphin stranding events were positively male-biased, including a significantly higher number of stranded male fetuses and neonates, and sexual dimorphism was observed in total body length of adults, with significantly greater length in males. For all records where human interaction (HI) could be determined as ‘yes’ or ‘no’, 30% were positive for HI, with the highest proportion of HI events occurring in the central and southern-most BSE stock areas; however, it is unknown how many HI cases contributed to mortality. This longitudinal study provides a comprehensive overview of marine mammal stranding patterns in Texas and serves as a useful resource for stranding investigators and Gulf-wide natural resource managers.

Superinfection exclusion: A viral strategy with short-term benefits and long-term drawbacks.

Viral superinfection occurs when multiple viral particles subsequently infect the same host. In nature, several viral species are found to have evolved diverse mechanisms to prevent superinfection (superinfection exclusion) but how this strategic choice impacts the fate of mutations in the viral population remains unclear. Using stochastic simulations, we find that genetic drift is suppressed when superinfection occurs, thus facilitating the fixation of beneficial mutations and the removal of deleterious ones. Interestingly, we also find that the competitive (dis)advantage associated with variations in life history parameters is not necessarily captured by the viral growth rate for either infection strategy. Putting these together, we then show that a mutant with superinfection exclusion will easily overtake a superinfecting population even if the latter has a much higher growth rate. Our findings suggest that while superinfection exclusion can negatively impact the long-term adaptation of a viral population, in the short-term it is ultimately a winning strategy.

A data-limited approach to determine the status of the artisanal fishery of sea silverside in southern Chile

Artisanal fisheries are essential, but for most the status of the stock supporting the fishing activity remains unknown due to lack of data and difficult access to sampling. For example, the artisanal fishery of sea silverside Odontesthes (Austromenidia) regia, in the Los Lagos administrative region of Chile, requires a data-limited approach to determine its status because the fishery administration has not invested in its monitoring. The approach consisted of estimating the spawning potential ratio (SPR) from length-frequency data collected in 2019 using length-based spawning potential ratio (LBSPR) and biological reference points using the only-catch optimized method (OCOM) to catch data covering from 1960 to 2020. In addition, five age-structured sea silverside populations were simulated considering uncertainty in recruitment and utilizing life-history parameters estimated by FishLife. According to LBSPR, the SPR was 0.58 (95% confidence intervals: 0.5-0.7), suggesting a fully exploited fishery status. The OCOM result was inconsistent with the life-history parameters and was discarded as a valid sea silverside stock assessment. The age-structured population simulations indicated evidence of a reduction in the spawning stock biomass close to 75% of the unexploited condition in 1960. Thus, the underexploited status reached a probability close to 49.4%, and the fully exploited status was 41.2%. The framework for a data-limited stock-assessment approach and results obtained here for the sea silverside are starting essential steps that may be emulated in other artisanal data-limited fisheries.

Hierarchy Establishment from Nonlinear Social Interactions and Metabolic Costs: An Application to Harpegnathos saltator

Social hierarchies are ubiquitous in social groups such as human societies and social insect colonies; however, the factors that maintain these hierarchies are less clear. Motivated by the shared reproductive hierarchy of the ant species Harpegnathos saltator, we have developed simple compartmental nonlinear differential equations to explore how key life-history and metabolic rate parameters may impact and determine its colony size and the length of its shared hierarchy. Our modeling approach incorporates nonlinear social interactions and metabolic theory. The results from the proposed model, which were linked with limited data, show that: (1) the proportion of reproductive individuals decreases over colony growth; (2) an increase in mortality rates can diminish colony size but may also increase the proportion of reproductive individuals; and (3) the metabolic rates have a major impact in the colony size and structure of a shared hierarchy.