Margarita Island Research Articles

Multilocus genetic analysis of Trypanosoma cruzi supports non-domestic intrusion into domestic transmission in an endemic region of Colombia

Trypanosoma cruzi, the causative agent of Chagas disease, is primarily transmitted to humans by hematophagous bugs of the Triatominae subfamily. In the Colombian Caribbean region, particularly on Margarita Island, T. cruzi transmission is highly endemic and associated with vectors such as Triatoma maculata and Rhodnius pallescens. Additionally, T. cruzi-infected Didelphis marsupialis are commonly found in close proximity to human dwellings. Given the complex transmission dynamics involving various domestic and non-domestic hosts, this study aimed to analyze 145 T. cruzi clones from twelve strains isolated from T. maculata, R. pallescens, and D. marsupialis using spliced leader intergenic region (SL-IR) sequences and nine polymorphic microsatellite loci. The results indicate the presence of a single polymorphic T. cruzi population, suggesting sustained local transmission dynamics between triatomines adapted to A. butyracea forests and peridomestic areas inhabited by synanthropic mammal reservoir such as D. marsupialis. Notably, this population appears to lack substructure, highlighting the importance of adopting an alternative eco-health approach to complement traditional chemical vector control methods for more effective and sustainable interruption of transmission.

Three-stage, 70 Myr exhumation of HP/LT rocks on Margarita, Venezuela: Caribbean intra-forearc shear, Grenada Basin rifting, and continental obduction

The La Rinconada Terrane comprises the core of Margarita Island, Venezuela; it is a composite unit composed of rocks of both continental and oceanic affinity that were brought together and metamorphosed at high-pressure and low- to medium-temperature conditions in a collision zone along NW South America in Albian to Cenomanian time. Details of the ensuing three-stage exhumation path and concomitant eastward translation until Miocene oblique collision of Margarita with central and eastern Venezuela have remained the subject of discussion. In this paper we integrate the results of published age dating and the details of extensive Rb-Sr, K-Ar, 40Ar/39Ar and fission track dating that have been only superficially presented to date. Initial exhumation from high-pressure conditions into ductile mid-crustal levels occurred at 90-80 Ma, followed by essentially isobaric, isothermal conditions for ca. 30 Myr during which the La Rinconada Terrane was subjected to continual ductile penetrative shearing and recrystallization. Partial to total recrystallization with concomitant partial to total isotopic re-equilibration, especially of quartz-rich rocks, was widespread during this time interval. The youngest Rb-Sr, K-Ar and 40Ar/39Ar ages cluster at ca. 50 Ma. Zircon fission track ages of 50–40 Ma corroborate exhumation into brittle levels of the crust at this time. An apatite fission track age of 23 Ma indicates the attainment of shallow depths in Miocene time. This discontinuous history of exhumation fits tectonic models of the Caribbean well. As the Caribbean Plate led by the Antilles Arc entered the gap between the Americas, strongly dextral, transpressive subduction in the SE Caribbean drove shear deep within the forearc. The La Rinconada Terrane of Margarita was exhumed to mid-crustal depths in the Late Cretaceous and is suggested to have occupied high-angle forearc shear zones above the primary Benioff Plane. As the arc migrated past the Guajira promontory and became extensional due to roll-back of Proto-Caribbean oceanic crust north of the Falcón re-entrant of the South American margin, the La Rinconada Terrane formed the footwall of an Eocene lithospheric rift that opened by late Eocene into the Grenada (oceanic intra-arc) Basin, effecting exhumation into the brittle crust. The progressive obduction of the SE Caribbean Plate onto the South American continental margin during prolonged dextral oblique collision completed most of Margarita's exhumation history by middle Miocene time (17–12 Ma).

Wind generation and power system interaction analysis using probabilistic techniques

. Energy power from renewable sources, especially wind turbine generators, are being considered as an important generation alternative in the electrical power systems around the world due to their non contaminant nature and low environmental effects. In particular, the power supplied by wind generators is widely random following the random nature of weather conditions; therefore a probabilistic approach during planning seems much more appropriate than the deterministic approach actually used in the electrical utilities. This paper presents a methodology that allows the application of probabilistic analysis, thru the use of programming tools, in the load flow planning studies. The methodology described provides the opportunity to obtain the steady state response in systems where wind power exists using a wind power generation model (WPGM) and an iterative routine to the load flow analysis considering each value of generation of the wind sources. A wind power generation model (WPGM) was developed using a random wind speed generator. The random wind speed generator describes the Weibull distribution of wind measurements, and then using Montecarlo simulation techniques, a program in Visual Basic executes the automatic evaluation of random samples of speed of wind considering the characteristic power curve of a wind turbine, obtaining a widely database of wind generation conditions. As a result of the investigation, a computational tool was developed in order to use it, in combination with the PSS/E load flow analysis software, for steady state power system analysis. The methodology was used as an assessment tool to identify the effects of wind turbines generation into the substation voltages and power flow profiles in the power network, for a wind farm project intended to be installed in Margarita Island. The analysis aimed to identify the transmission adjustments, reinforcements and expansions needed to guarantee the wind farm project integration successful into the power system.

Ecophysiological traits change little along a successional gradient in a tropical dry deciduous woodland from Margarita Island, Venezuela

Tropical dry forests (TDFs) are the most threatened terrestrial ecosystems and studying how functional traits of plant species change as secondary succession advances is important for understanding how and how fast can TDFs recover from disturbance. In this work we asked the question: how do functional traits change during secondary succession in a tropical dry woodland? We studied functional traits, especially ecophysiological traits, such as gas exchange, plant-water relations, leaf carbon isotope composition (δ13C), specific leaf area (SLA) and nitrogen concentration, in shrubs and trees in three successional stages (6 and 20 years after abandonment, and the dry deciduous woodland, 6 years, 20 years, and DW, respectively) along a successional gradient in a TDF in both wet and dry seasons to understand how TDFs recover after disturbance by opencast sand mining. During the wet season, similar mass-based photosynthetic rates (Amass), water potential, relative water content, instantaneous and intrinsic water-use efficiency (WUE and IWUE) and SLA were found in the 6 years and DW stages. During seasonal drought, similar reductions in these variables were observed for all three successional stages. However, δ13C of the 6 years species was higher than in 20 years and DW species, indicating a higher long-term integrated WUE in the former due to a strong reduction in stomatal conductance (gs) in the dry season. Species from the DW seem to couple metabolic changes to their characteristically low gs, such that nitrogen concentration per unit mass explained 86% of the variation in Amass. Given the functional similarity among species from the different successional stages, native species from the DW stage could have good physiological performance in the 6 and 20 years sites, and therefore could be used to restore these degraded areas.

Nine decades of Spanish sardine Sardinella aurita exploitation in Venezuela, a critical revision

The Spanish sardine Sardinella aurita, is the most important fishing resource in Venezuela, on Margarita Island it began its fishing and canning. This review estimates catch over nine decades and causes of fishing continuity. In 90 years, 4,386,758 tons were caught, a modest volume due to poor statistics. Three management ordinances have been enacted the first appeared after 40 years of activity in canning plants. The sardine industry has four periods, the first between 1927 and 1973 without fishing regulation and another three (1974-2005; 2006-2013 and 2014-2017) when the ordinances are applied. In each one the catch, annual average, operating gears, the capture per unit of effort and relevant investigations are considerate. The current regulation was based on the noticeable decrease in catches since 2005, which is why, in 2013, a ban was imposed and the minimum catch size was established at 19 cm. The regulation is ineffective because after seven years, the catches do not recover previous levels, in addition, it is incomprehensible to increase fishing gear (357 fishing in 2017). The artisanal fishing with beach seine (chinchorro) and the average maturity size of the species explain the permanence of the fishery, which endangered by the intensive use of purse seines that must be restricted.

Manta and devil ray species occurrence and distribution in Venezuela, assessed through fishery landings and citizen science data.

Manta and devil rays (collectively mobulids) belong to the monogeneric Mobulidae, which currently comprises 10 species, including a putative third manta ray species (Mobula cf. birostris). These large planktivorous rays are distributed throughout the tropical and subtropical oceans of the world. To date, six mobulid species are reported for the western Atlantic Ocean and the Caribbean Sea, three of which had previously been reported in Venezuela (Mobula birostris, Mobula tarapacana and Mobula hypostoma). A preliminary assessment of fishery landings and citizen science data was conducted to further the scientific knowledge of mobulid species in Venezuela. Fisheries landing data were collected at Margarita Island between 2006 and 2007, and again in 2014. Data mining of internet search engines and social media platforms spanning the past two decades was also conducted. A total of 117 individuals of five mobulid species were recorded: Mobula sp. (n=27), M. birostris (n=36), M. tarapacana (n=3), Mobula mobular (n=26), Mobula thurstoni (n=14) and M. cf. birostris (n=11). The latter three species are the first confirmation of these species in Venezuela. The authors found no records of the previously reported M. hypostoma during this study. Although the occurrence of M. hypostoma in Venezuela remains possible because of the broad regional range of this species, its current presence in Venezuela is invalidated given the repeated misidentifications which have occurred in previous publications. The results of this study increase the number of reported mobulid ray species in Venezuela to five (excluding M. hypostoma). The overall data from juvenile manta rays and pregnant M. mobular and M. thurstoni recorded in this study, combined with the occurrence of all but one species of mobulid ray found in the western Atlantic Ocean, suggest Venezuela provides important habitat for this threatened family of rays.

New Records ofCaudriellaHaman and Huddleston from the Middle and Late Eocene of Neo-Tethys: Taxonomic and Palaeobiogeographic Implications

ABSTRACTThe middle to upper Eocene mixed carbonate-clastic and siliciclastic deposits of the Şevketiye and Keşan formations in northwest Turkey yielded unique assemblages of larger benthic foraminifera, some displaying a typical orbitoidiform test, not comparable to any known taxa in the Palaeogene of the Neo-Tethys. These specimens with a flat, discoidal test, occasionally with an indistinct central depression, possess a central layer of equatorial chambers/chamberlets displaying a cyclical (orbitoidal) growth pattern and thick lateral layers with numerous chamberlets. The megalospheric embryonic apparatus possesses three small chambers (a triconch, the chambers of which are separated by notably thin walls), followed by a large auxiliary chamberlet. These specimens closely correspond to the genus Caudriella Haman and Huddleston and its type-species Margaritella ospinae (Caudri) that has only previously been reported with confidence from the Caribbean region, notably the type locality within the middle Eocene Punta Mosquito Formation at Margarita Island off Venezuela. Caudriella at its type locality also possesses a trilocular embryonic apparatus, which was incorrectly interpreted as arranged in a rectilinear or slightly curved row. The diagnosis of Caudriella is emended and considering the similarities in their equatorial sections with closely associated Linderina Schlumberger, a comparison of their embryonic-nepionic stages is given from the same deposits in NW Turkey and with those from the middle Eocene of the Sulaiman Range (Pakistan) and Kutch (India). A new record of primitive Caudriella is presented from Jamaica. The palaeobiogeographic distribution of Caudriella is reconsidered, being recorded from both the American/Caribbean and the Western Neo-Tethys bioprovinces. Limited data suggest eastward directed dispersal of the genus, even though this would be counter to most of the prevailing surface currents during the Eocene.

Environmental drivers of sex-biased foraging behavior in Magnificent Frigatebird in Baja California Sur, Mexico

Understanding the characteristics of a species’s distribution represents a challenge in marine environments because movement patterns and foraging areas are restricted by highly dynamic spatiotemporal variations in environmental conditions. In response to this heterogeneous context, marine predators such as seabirds need to maximize their foraging efficiency, especially during the breeding season, when movement is restricted by the need to return to the nest. Biologging technologies such as satellite transmitters and Global Positioning System (GPS) receivers allow researchers to track birds at sea and investigate the relationship between foraging strategy and changing oceanographic features. Our study focuses on characterizing the feeding areas of Magnificent Frigatebird (<em>Fregata magnificens</em>) breeding in Baja California Sur, Mexico. We used GPS receivers to track the foraging flights of frigatebirds during 2017–2019, identifying the core foraging areas and characterizing environmental conditions and marine productivity in these areas. Individuals repeatedly selected areas close to the colonies located in Espíritu Santo archipelago (Gulf of California) and Santa Margarita Island (Pacific Ocean). However, some males flew to more distant and equally productive areas to the south and north of the Baja California peninsula. We presume that the differential use of foraging areas between males and females reflects biometrical and behavioral differences of the sexes, which may explain the relationships between foraging behavior and breeding, intraspecific competition, and sex-based differences in parental investment. Because frigatebirds are considered indicators of marine environmental conditions, our data are useful to identify areas where prey species aggregate in space and time and, therefore, to expand the boundaries of existing marine protected areas. Data on seabird foraging ranges described here can be useful for delineating marine protected area boundaries and can be considered suitable candidates for inclusion in appropriately designated regional marine spatial planning.

TROPHIC STATUS OF A TROPICAL COASTAL LAGOON IN MARGARITA ISLAND, VENEZUELA

Punta de Piedras Lagoon is a coastal lagoon located south of Margarita Island, in the Venezuelan Caribbean Sea. This lagoon has ecological and economic importance for the inhabitants of nearby communities. Currently, the urban and industrial development in its surroundings represents a potential source of pollutants, providing concentrations of nutrients that could affect the ecological balance of the area. The trophic status of Punta de Piedras Lagoon was evaluated using various trophic indices. The concentrations of chlorophyll-a and nutrients (ammonium, nitrites, nitrates, and orthophosphates) were estimated in 10 stations with a monthly frequency from February 2005 to January 2006. These data were used to estimate the trophic condition based on the Karydis and TRIX trophic indices, and by comparison with Organization for Economic Co-operation and Development reference values. It was found that Punta de Piedras lagoon presented mesotrophic conditions in most of the water body having considerable differences between indices. The values of the closest station to Paseo Esther Gil corresponded to eutrophic waters. However, the circulation and residence time of water allow an exchange with the adjacent sea, which prevents the eutrophication process in the lagoon.

California sea lion population decline at the southern limit of its distribution during warm regimes in the Pacific Ocean

We evaluated the effect of regime shifts on the population dynamics of the California sea lion colony of Santa Margarita Island from 1979–2020. This colony is found at the southern extreme of the California sea lion’s range in the North Pacific Ocean in the temperate–tropical​ transition zone characterized by high primary productivity where oceanic and lagoon environments converge. It is largely isolated from other colonies. We assessed the influence of sea surface temperature and net primary productivity on sea lion population dynamics using historical abundance data taken from the literature and collected in the field (1979–2015). We also performed a Population Viability Analysis to determine the population trend and predict the probability that the colony could go extinct. Anomalies of sea surface temperature (1981–2020) and net primary productivity (2002–2020) were analyzed. Warm and cold periods were determined using the Regime Shift Detector. Colony size decreased at a rate of 4% per year, a decrease of ∼75% over 36 years. Four regimes (two cold and two warm) were identified in relation to the sea surface temperature and two regimes (one cold and one warm) in relation to the net primary productivity. The number of births decreased during strong El Niño events under both warm and cold regimes. During warm regimes, a lower abundance of sea lions was observed compared to the cold regimes that preceded them. Population declines due to regime shifts have also been observed in several species of pinnipeds that inhabit the North Pacific (e.g., the Steller sea lion). The Santa Margarita Island breeding colony meets the IUCN’s quantitative criteria for “Vulnerable” or “Endangered”. Our results highlight the importance of a colony-level approach in understanding how populations respond to changes in environmental conditions.

When good attitudes are not enough: understanding intentions to keep yellow-shouldered Amazons as pets on Margarita Island, Venezuela

AbstractUnsustainable harvesting to supply the demand for pets is the second most significant threat to parrots (Psittacidae). Given that parrot keeping is widespread, in-depth and culturally sensitive research is needed to inform and develop interventions targeted at changing consumer preferences and purchasing behaviours. Parrot keeping is thought to be driven mainly by a desire for companionship (the affection hypothesis). Alternative hypotheses include a deeply ingrained culture of parrot ownership (the tradition hypothesis) or the influence of socio-economic context (the contextual hypothesis). We used the theory of planned behaviour to evaluate the relative importance of behavioural and contextual factors influencing the intention to keep the yellow-shouldered AmazonAmazona barbadensisas a pet. We interviewed 150 owners and non-owners of parrots in two locations in Macanao Peninsula, Margarita Island, Venezuela, where the primary population of this species is located. We found mixed evidence supporting both the affection and contextual hypotheses: intention to keep parrots was higher in non-owners with high education level, strong affective attitudes regarding human–animal relationships, and higher expectations about social norms (41% of explained variance). Our study expands previous research on the illegal parrot trade by taking into account behavioural measures beyond attitudes, highlighting the role of social norms frequently ignored in such research. We discuss how a behaviour change campaign could redirect affective attitudes in the human–parrot relationship, and promote new social norms that support parrot conservation. Future research should consider the inclusion of moral and injunctive norms, and monitoring of intervention effectiveness.

A new species of Ampelisca (Crustacea: Amphipoda: Ampeliscidae) from Santa Margarita Island, west of the Baja California Peninsula, Mexico

A new species of the genus Ampelisca Krøyer, 1842 is described and illustrated in detail. The specimens were collected from soft bottom at 15 m depth in the northern coast of Santa Margarita Island, Mexico. Ampelisca capetilloi sp. nov. is characterized by: head as long as pereonite 1-2 combined; mandible with 8 rakers; maxilla 1 palp article 2 expanded distally; gnathopod 1 propodus anterior margin with 7 distal setae; pereopod 7 basis reaching middle portion of merus, posterodistal lobe of merus large, extending one-third of carpus; pleonite 3 dorsal margin smooth; urosomite 1 slightly sinuous dorsally; telson bilobate, each lobe with 3 dorsal setae. The new species is similar to Ampelisca mexicana Barnard, 1954 and A. pugetica Stimpson, 1864, but can be easily recognized with the identification key included herein. A checklist for Ampelisca species documented from the Eastern Tropical Pacific, including their geographic distribution, habitat, and depth range, is provided.

Garnetite, garnet-quartz (‘coticule’) and calc-silicate layers in high-pressure metapelitic rocks, Venezuela: metamorphosed exhalites in a Cretaceous back-arc basin

ABSTRACT Massive, boudinaged, rose-coloured layers up to one metre in thickness composed of 60–80 vol% spessartine-rich garnet and 15–40 vol% quartz occur in high-pressure, garnet-mica schist on Margarita Island, Venezuela. In the past, such spessartine-garnet-rich rocks have often, although inaccurately, been called ‘coticule’. Apatite can be significant, reaching 20 vol%. Accessory minerals are allanite, rutile (commonly rimmed by ilmenite) and rare phengite. Within the same mica-schist sequence, intercalated calc-silicate layers from one to two metres in thickness exhibit alternating layers, on a sub-mm- to cm-scale, of quartz and greenish layers rich in zoisite, epidote-supergroup minerals and diopside. Hyalophane and barite are present in small amounts. Calc-silicates are commonly pitted, with yellow to dark-brown, gossanous, botryoidal crusts. The composition of garnet in the garnet-rich layers, the calc-silicate layers and their host metasediments is distinctly different. In the garnet-rich layers, compositions are almandine-dominant (Alm57-63), followed by spessartine (Sps18-24), grossular (Grs2-16), pyrope (Prp6-11) and andradite (Adr0-6). Garnet in calc-silicate layers can range from almost pure grossular to Grs45-49Alm32-34Sps13-15, and in the enclosing metasediments is typically Alm71-73Prp14-15Grs3-8Sps4-7And2. Chondrite-normalized REE patterns of all three rock types are similar in shape, differing only in absolute contents, so that a common sedimentary precursor is indicated. Major and trace element chemistry of the garnet-rich layers are best explained if their pre-metamorphic protolith originated as a mixture of 60–70% normal detrital input and a precipitate from a distal source of hydrothermal activity. The term meta-exhalite is appropriate. The calc-silicate layers are more enigmatic, but an origin as a mixture of a hydrothermal component with a Ca-rich sediment also appears likely. Numerous lines of evidence indicate that the protoliths of the high-pressure rocks of Margarita Island originated in an Early Cretaceous back-arc basin in NW Colombia, so that an exhalite origin for garnet-rich and calc-silicate rocks is a plausible scenario.

Impacts of fishing on the Caribbean white sea urchin, Lytechinus variegatus, in Margarita Island, Venezuela

The Caribbean white sea urchin, L. variegatus, is locally harvested in Margarita Island and other locations of southeastern Venezuela. The recent reduction of densities raises concerns about potential impacts for overfishing. Densities of L. variegatus were estimated at Impact and Control locations between late-2012 and mid-2015 to 1) test temporal changes, comparing with 1997–1998 estimations, 2) the effect of seasonal closure on resource recovery and 3) the effect of local expansion. The results suggest that, after a period of fourteen years, an important decrease in L. variegatus densities occurred, as well as a lack of population recovery in fishing areas during seasonal closures. Furthermore, during the monitoring program, it was observed fishing activities in one Control location that subsequently showed clear patterns of population depletion, like other Impact locations. Fishing impact on L. variegatus populations is severe, persistent and expands over time without evidence of recovery, therefore it is expected that local populations of L. variegatus would collapse under current exploitation levels. However, due to the L. variegatus life history and its distribution range, recovery of impacted populations could be possible via recruitment of planktonic larvae if effective management actions are imposed. It is recommended to exercise more regulations on fishing activities and to execute management measures that allow recovering the stocks to maintain local populations of sea urchin.

Two new species of Styela (Tunicata: Ascidiacea) from the tropical West Atlantic Ocean.

Two new species of the genus Styela are described, with very rare characteristics in this genus: both are shallow-water and tropical, with more than two gonads in each side of the body. Styela panamensis sp. nov. is described from specimens collected in Bocas del Toro, Atlantic coast of Panama, and Styela multicarpa sp. nov. from specimens collected in Espírito Santo, Brazil and Margarita Island, Venezuela. They are probably native to the south Caribbean and S. multicarpa sp. nov. is introduced in Brazil.

SARS-CoV-2 genetic diversity in Venezuela: Predominance of D614G variants and analysis of one outbreak.

SARS-CoV-2 is the new coronavirus responsible for COVID-19 disease. The first two cases of COVID-19 were detected in Venezuela on March 13, 2020. The aim of this study was the genetic characterization of Venezuelan SARS-CoV-2 isolates. A total of 7 full SARS-CoV-2 genome sequences were obtained by Sanger sequencing, from patients of different regions of Venezuela, mainly from the beginning of the epidemic. Ten out of 11 isolates (6 complete genomes and 4 partial spike genomic regions) belonged to lineage B, bearing the D614G mutation in the Spike protein. Isolates from the first outbreak that occurred in the Margarita Island harbored an in-frame deletion in its sequence, without amino acids 83-85 of the NSP1 of the ORF1. The search for deletions in 48,635 sequences showed that the NSP1 gene exhibit the highest frequency of deletions along the whole genome. Structural analysis suggests a change in the N-terminal domain with the presence of this deletion. In contrast, isolates circulating later in this island lacked the deletion, suggesting new introductions to the island after this first outbreak. In conclusion, a high diversity of SARS-CoV-2 isolates were found circulating in Venezuela, with predominance of the D614G mutation. The first small outbreak in Margarita Island seemed to be associated with a strain carrying a small deletion in the NSP1 protein, but these isolates do not seem to be responsible for the larger outbreak which started in July.

Reproductive aspects of seven threatened shark species captured by artisanal fisheries in the southern Caribbean Sea

Venezuela is among the top four Latin American countries with the greatest elasmobranch biodiversity. The country is also characterised by extensive artisanal fisheries, but there is a paucity of regional life-history data for many important species. Here, we provide reproductive information for one local (Carcharhinus acronotus) and six cosmopolitan species (C. brevipinna, C. falciformis, C. limbatus, Galeocerdo cuvier, Sphyrna lewini and Isurus oxyrinchus) landed by artisanal fisheries at Margarita Island, Venezuela. For two years (2006–2007), three ports and two fish markets were weekly sampled for the total length (TL), sex, and maturity stages for specimens of the assessed species. A total of 664 specimens were analysed, of which 96% were immature. We found no significant differences in the sex ratios of all species, except for C. falciformis (1.5F:1M). Based on the numbers of neonates with unhealed umbilical scars, parturition appeared to peak in the first half of the year for C. acronotus (April–June) and S. lewini (May–June). Conversely, the second half of the year appeared important for parturition in C. brevipinna (August–September), C. limbatus (July–September) and G. cuvier (September–November). Both C. falciformis and I. oxyrinchus (individuals <1.5 m TL) showed non-seasonal parturition. The large percentages of small sizes of individuals in landings imply the waters surrounding Margarita Island might represent an important nursery area, and it is likely that historical and ongoing harvest rates represent a threat for regional populations of various elasmobranchs.

Using Peoples’ Perceptions to Improve Conservation Programs: The Yellow-Shouldered Amazon in Venezuela

The perceptions and attitudes of local communities help understand the social drivers of unsustainable wildlife use and the social acceptability of conservation programs. We evaluated the social context influencing illegal harvesting of the threatened yellow-shouldered Amazon (Amazona barbadensis) and the effectiveness of a longstanding conservation program in the Macanao Peninsula, Margarita Island, Venezuela. We interviewed 496 people from three communities and documented their perceptions about (1) status and the impact of threats to parrot populations, (2) acceptability of the conservation program, and (3) social processes influencing unsustainable parrot use. Approval of the program was high, but it failed to engage communities despite their high conservation awareness and positive attitudes towards the species. People identified unsustainable use as the main threat to parrots, but negative perceptions were limited to selling, not harvesting or keeping. Harvesters with different motivations (keepers, sellers) may occur in Macanao, and social acceptability of both actors may differ. Future efforts will require a stakeholder engagement strategy to manage conflicts and incentives to participation. A better understanding of different categories of harvesters, as well as their motives and role in the illegal trade network would provide insights to the design of a behavior change campaign.

Deadweight anchoring behavior for aquaculture longline

The similarity theory was used to study the behavior of five anchoring and one rezon type deadweight designs, using scale models. The surface sediments extracted from Charagato Bay, Cubagua Island, were characterized to evaluate the efficiency of these models on these substrates. A test structure consisting of a tank with a mixture of sediment and seawater, and a metal trestle was used. Tension variables were considered, using a 6 mm PE end section. Weights were added at one of its ends which represented the longline system's resistance force and at the other the model's force in the eyebolt (Tc) representing the gripping force due to the interaction of the anchoring design with the substrate, and the static rupture tension (Tr) upon the weight (Pm) of each model, against different anchoring attack angles (), aspect ratios (AR) 1/2.5; 1/3.0; 1/3.5, and 1/4.0; sail attack angles () of 0, 10, and 20°, and the efficiency index (EI) of each model. The Kruskal-Wallis contrast was used to detect the possible differences against different anchoring attack angles, and, to locate the differences between them; box and mustache graphs were used. The most effective model on very fine sand-type sediment was the pyramidal with the claw-like frame, followed by the pyramidal with the shovel-like frame and the rezon type traditionally used on Margarita Island.

Age and growth of the shark, Mustelus higmani (Carcharhiniformes: Triakidae) from Venezuela

Abstract. Introduction: Mustelus higmani is one of the shark species most commonly caught in the northeastern region of Venezuela; however, this species has been poorly studied. Objective: to evaluate the age and growth of M. higmani on the basis of the optical analysis of vertebrae. Methods: Between August 2016 and July 2017, the vertebral samples were collected in the fishing port of Juan Griego, Margarita Island. The growth study was based on a sample of 238 individuals, 86 males (24.1-59.5 cm TL) and 152 females (24.4-69.5 cm TL) and the use of growth modeling approaches. Results: The RMI analysis indicated an annual periodicity for the deposition of growth rings. Ages assigned varied between 0 and 5 years in males, and between 0 and 6 years in females. The estimates of growth parameters obtained were L∞ = 60.8 cm TL, k = 0.54 years-1 and t0 = -1.04 years in males; and L∞ = 72.4 cm TL, k = 0.40 years-1 and t0 = -1.31 years in females. The ages at maturity and longevities resulted respectively in 2.5 and 6.4 years for males; and in 2.0 and 8.7 years for females. Conclusions: In general, results indicate that M. higmani has a rapid growth, early maturity, short longevity, and continuous reproduction, characterizing it as a biologically productive species.&#x0D; Key words: Caribbean; ecology; elasmobranchs; fishery; sharks.