Inland Farm Research Articles

Full-Genome Sequencing and Confirmation of the Causative Agent of Erythrocytic Inclusion Body Syndrome in Coho Salmon Identifies a New Type of Piscine Orthoreovirus.

Erythrocytic inclusion body syndrome (EIBS) causes mass mortality in farmed salmonid fish, including the coho salmon, Onchorhynchus kisutchi, and chinook salmon, O. tshawytscha. The causative agent of the disease is a virus with an icosahedral virion structure, but this virus has not been characterized at the molecular level. In this study, we sequenced the genome of a virus purified from EIBS-affected coho salmon. The virus has 10 dsRNA genomic segments (L1, L2, L3, M1, M2, M3, S1, S2, S3, and S4), which closely resembles the genomic organization of piscine orthoreovirus (PRV), the causative agent of heart and skeletal inflammation (HSMI) in Atlantic salmon and HSMI-like disease in coho salmon. The genomic segments of the novel virus contain at least 10 open reading frames (ORFs): lambda 1 (λ1), λ2, λ3, mu 1 (μ1), μ2, μNS, sigma 1 (σ1), σ2, σ3, and σNS. An additional ORF encoding a 12.6-kDa protein (homologue of PRV p13) occurs in the same genomic segment as σ3. Phylogenetic analyses based on S1 and λ3 suggest that this novel virus is closely related to PRV, but distinctly different. Therefore, we designated the new virus ‘piscine orthoreovirus 2’ (PRV-2). Reverse transcription–quantitative real-time PCR revealed a significant increase in PRV-2 RNA in fish blood after the artificial infection of EIBS-naïve fish but not in that of fish that had recovered from EIBS. The degree of anemia in each fish increased as the PRV-2 RNA increased during an epizootic season of EIBS on an inland coho salmon farm. These results indicate that PRV-2 is the probable causative agent of EIBS in coho salmon, and that the host acquires immunity to reinfection with this virus. Further research is required to determine the host range of PRV species and the relationship between EIBS and HSMI in salmonid fish.

Assessing potential health impacts of waste recovery and reuse business models in Hanoi, Vietnam.

In resource-constrained settings, the recovery of nutrients and the production of energy from liquid and solid waste are important. We determined the range and magnitude of potential community health impacts of six solid and liquid waste recovery and reuse business models in Hanoi, Vietnam. We employed a health impact assessment (HIA) approach using secondary data obtained from various sources supplemented with primary data collection. For determining the direction (positive or negative) and magnitude of potential health impacts in the population, a semiquantitative impact assessment was pursued. From a public health perspective, wastewater reuse for inland fish farming, coupled with on-site water treatment has considerable potential for individual and community-level health benefits. One of the business models investigated (i.e. dry fuel manufacturing with agro-waste) resulted in net negative health impacts. In Hanoi, the reuse of liquid and solid waste-as a mean to recover water and nutrients and to produce energy-has considerable potential for health benefits if appropriately managed and tailored to local contexts. Our HIA methodology provides an evidence-based decision-support tool for identification and promotion of business models for implementation in Hanoi.

Intra-farm wind speed variability observed by nacelle anemometers in a large inland wind farm

Using 11-month, 15-min averaged measurements by nacelle anemometers at 274 wind turbines, we studied the spatial and temporal variability of wind speed in a wind farm over an area of about 20km by 20km located in mountainous terrain. The intra-farm variability is compared between winter and summer: during summer the dominant time scale of wind speed fluctuation is the diurnal cycle of 24h. During winter, however, the dominant scale is 48h. The spatial variability of wind speed on scales ≤O(10km) is closely associated with the temporal variability on scales ≤O(10h). Over a time span ≤3h rapid drop-offs in wind speed occur more often than rapid increases, and the rapid drop-offs are more frequent during summer than winter. The intra-farm spatial variability of wind speed has a diurnal cycle with that reaches its maximum in the nighttime and its minimum around midday. For accurate wind power modeling, it may be of importance to consider the intra-farm variability of wind speed distribution. We found that when energy production exceeds 200MW, its estimation based on the averaged wind speed is significantly larger than when based on the speeds at individual turbines.

Effect Analysis about Inland Fish Farm for Development of Underground Seawater

Due to red tide and abnormal currents that take place every year, the damage of inland fish farms that takes sea water is increasing frequently. Also, the households of inland fish farm due to the increase in the cost of fuel and electricity are struggling many hardships economically. In relation to underground seawater for it`s farm analyzed economic effect based on the actual conditions for 1,700 inland fish farms, from this I have deduced policy implications for direction this project to be pursued from now on. The saving rate of costs of the fuel and electricity through the development of an underground seawater were approximately analyzed to decline about 3.4~9.7%, if utilizing only about 5% of the undeveloped farms, it was estimated effect of about 61 billion won, if 10%, it was estimated effect of about 122 billion won. Consideration in selecting the developer of underground seawater will be selected an character of farm method. It is expected this study will be helpful for business analysis related government in the fisheries.

Sclerochronology of Busycon sinistrum: late prehistoric seasonality determination at St. Joseph Bay, Florida, USA

Recent archaeological investigations indicate that coastal Fort Walton cultures in the St. Joseph Bay region of northwest Florida emphasized marine and estuarine foraging. These late prehistoric, Mississippi-period (A.D. 1000–1500) peoples collected fish, shellfish, and other aquatic resources. At the Richardson's Hammock site (8Gu10), radiocarbon-dated to about A.D. 1300, large, predatory gastropods were a major subsistence component. This adaptation is in sharp contrast with that of contemporaneous inland Fort Walton societies, who relied on maize agriculture, and raises the question whether coastal groups were separate hunter–gatherer–fisher populations or migrated seasonally from inland farming villages. We perform stable oxygen and carbon isotope sclerochronology on lightning whelks (Busycon sinistrum) to determine the seasonality of Fort Walton foraging and to compare the environment of prehistoric St. Joseph Bay with that of the modern bay. Oxygen isotope profiles suggest that shellfish collecting was relegated primarily to the summer months, producing a scheduling conflict with the primary growing season for maize in northwest Florida. Thus, coastal and inland Fort Walton sites probably represent separate culture groups. The relationship between δ18Oshell and δ13Cshell indicates similar environmental and climatic conditions between prehistoric St. Joseph Bay and today. However, modern whelks are depleted in 13C compared to Fort Walton whelks, which reflects both twentieth century CO2 emissions and years of dredging and wastewater pollution entering the bay.

Power Curve Estimation With Multivariate Environmental Factors for Inland and Offshore Wind Farms

In the wind industry, a power curve refers to the functional relationship between the power output generated by a wind turbine and the wind speed at the time of power generation. Power curves are used in practice for a number of important tasks including predicting wind power production and assessing a turbine’s energy production efficiency. Nevertheless, actual wind power data indicate that the power output is affected by more than just wind speed. Several other environmental factors, such as wind direction, air density, humidity, turbulence intensity, and wind shears, have potential impact. Yet, in industry practice, as well as in the literature, current power curve models primarily consider wind speed and, sometimes, wind speed and direction. We propose an additive multivariate kernel method that can include the aforementioned environmental factors as a new power curve model. Our model provides, conditional on a given environmental condition, both the point estimation and density estimation of power output. It is able to capture the nonlinear relationships between environmental factors and the wind power output, as well as the high-order interaction effects among some of the environmental factors. Using operational data associated with four turbines in an inland wind farm and two turbines in an offshore wind farm, we demonstrate the improvement achieved by our kernel method.

Stable Fly, Stomoxys calcitrans (L.), Dispersal and Governing Factors.

Although the movement of stable fly, Stomoxys calcitrans (L.), has been studied, its extent and significance has been uncertain. On a local scale (<13 km), fly movement occurs between host animals and resting sites to feed and mate, mainly at on-farm locations where herbivorous livestock regularly congregate. Small numbers emigrate from livestock congregation sites in search of other hosts and oviposition substrate, mostly within <1.6 km. Such local movement occurs by flight ~90 cm above ground, or with moving livestock. While stable flies are active year-round in warm latitudes, cold winters in temperate areas result in substantial population and activity declines, limiting movement of any sort to warmer seasons. Long-distance dispersal (>13 km) is mainly wind-driven by weather fronts that carry stable flies from inland farm areas for up to 225 km to beaches of northwestern Florida and Lake Superior. Stable flies can reproduce for a short time each year in washed-up sea grass, but the beaches are not conducive to establishment. Such movement is passive and does not appear to be advantageous to stable fly’s survival. On a regional scale, stable flies exhibit little genetic differentiation, and on the global scale, while there might be more than one “lineage”, the species is nevertheless considered to be panmictic. Population expansion across much of the globe likely occurred from the late Pleistocene to the early Holocene in association with the spread of domesticated nomad livestock and particularly with more sedentary, penned livestock.

An Economic Study of Low Lying Inland Fish Farming in Selected Areas of Kishoreganj District

The study was designed to examine the low lying inland fish farming practices of Karimganj upazila under Kishoreganj districts. Field level data were collected through direct interview using semi-structured questionnaire. Eighty sample farmers were selected purposively from the study areas. Six types of farming practices were identified in the study area among which only two types were prominent i.e., pond fish farming and Beel fish farming. Tabular, statistical and mathematical analyses were done to achieve the major objectives. The benefit cost ratio in Beel fish farming was 2.86 and in case of pond fish farming it was 1.95. Multiple regression model was used to explain the variation of gross return of pond and Beel fish farming and it was found that coefficients of human labour, feed, cowdung and manure had significant impact on gross return, whereas coefficients of feed, harvesting and making sanctuary had significant impact on gross return of Beel fish farming. Resource use efficiency was calculated by the ratio of marginal value product and marginal factor cost. Finally, the study identified some important problems of low lying inland fish farming and suggested probable solutions relating to the problems.DOI: http://dx.doi.org/10.3329/pa.v23i1-2.16619Progress. Agric. 23(1 &amp; 2): 81 – 90, 2012

Prevalence and antimicrobial susceptibility of Vibrio species related to food safety isolated from shrimp cultured at inland ponds in Thailand

Inland farming of marine shrimp species is a relatively recent development, in response to increasing demand for the products. This study aimed to investigate the prevalence and antimicrobial resistance of potentially pathogenic Vibrio species in shrimps cultured at inland ponds with low salinity in Thailand. Of 16 shrimp samples (white-leg shrimps and black-tiger shrimps) from ponds with water temperatures from 29 to 32 °C, and salinities from 1 to 5 parts per trillion, 15 contained Vibrio cholerae (densities: 62–252,000 MPN/g). Vibrio parahaemolyticus was present in six samples (370–6,300,000 MPN/g), and Vibrio vulnificus was present in two samples (16–1300 MPN/g). V. parahaemolyticus has higher affinity for non-native white-leg shrimp than for native black-tiger shrimp. The minimum inhibitory concentrations were then measured for 12 common antimicrobial agents. Resistance to ampicillin and oxytetracycline (8% and 2% of the isolates) was documented in V. cholerae isolates, resistance to ampicillin and oxytetracycline (72% and 3%) was found in V. parahaemolyticus isolates, and resistance to nalidixic acid (20%) was detected in V. vulnificus isolates. β-lactamase and tetracycline resistance genes were detected in the resistant Vibrio isolates. The oxytetracycline-resistance phenotype was eliminated by plasmid curing, suggesting that the resistance was related to R-plasmids. Our results show that shrimps cultured even in low salinity ponds are potentially contaminated with pathogenic Vibrio species, and that shrimp are a vehicle for transfer of species with antimicrobial resistance genes to the public.

Phosphorus and Nitrogen Budgets for Inland, Saline Water Shrimp Ponds in Alabama

Phosphorus and nitrogen budgets were prepared for ponds at an inland low-salinity shrimp farm in the Black land Prairie region of Alabama. The study was conducted during the first crop in three newly constructed ponds that had never before contained water. The main input of phosphorus and nitrogen was feed and averaged 47 kg/ha and 208.5 kg/ha, respectively. These inputs respectively accounted for 98.9% and 95.5% of total input for phosphorus and nitrogen; other inputs of phosphorus and nitrogen were post larvae, well water, rainfall and runoff, that combined, averaged 0.5 kg/ha and 9.8 kg/ha, respectively. The major output of phosphorus and nitrogen was shrimp harvest that averaged 5.2 kg/ha for phosphorus and 45.7 kg/ha for nitrogen. Only 10.9% of phosphorus and 21% of nitrogen applied in feed were incorporated into shrimp. Other losses of phosphorus and nitrogen were water outflows (seepage and harvest effluent) that accounted for 3.2 kg/ha for phosphorus and 7.8 kg/ha for nitrogen. The difference between the inputs and outputs of phosphorus is thought to represent adsorption by bottom soils. For nitrogen, the discrepancy between input and output apparently was caused by accumulation of organic nitrogen in bottom soil, denitrification and NH3 volatilization.

中国内陸部農村における農地流動化の特徴と展望

中国内陸部農村における農地流動化の特徴と展望

Research on the Prefabricated Prestressed Cylinder Foundation of Wind Turbines in the Soft Soil Region

With the rapid development of inland wind farm in China, the costal wind farm still has not got large-scale development as the result of the higher cost of fan foundation and the more difficulty of construction. The prefabricated prestressed cylinder foundation (PPC foundation), as a new type of wind turbine foundation designed for the soft soil region such as the inter-tidal coastal zone and inland wetlands, is introduced in this paper. The condition of lateral earth pressure distribution around the foundation which determines the flexural capacity of fan foundation in the soft soil is studied. Through theoretical analysis and mathematical derivation, the result shows that the lateral earth pressure around PPC foundation is changed with depth by 1.5th power curve which has good fitting to the finite element analysis result. The simplified and improved design process is applied into the practical engineering and the good economy of PPC foundation is proved.

양식넙치에 경구투여한 Ciprofloxacin의 근육조직 잔류량을 이용한 휴약 기간 설정 연구

Ciprofloxacin is the most commonly used fluoroquinolones for treating bacterial disease in olive flounder (Paralichthys olivaceus) farming, but its withdrawal time for industrial-scale farming has not been established. The depletion of ciprofloxacin was investigated in the olive flounder under field conditions. Fish were kept in an inland fish farm and fed a commercial diet containing 5 mg/kg of ciprofloxacin for 13 days. Seven fishes per sampling time were examined during and after the treatment. Ciprofloxacin and its major metabolite, enrofloxacin, were analyzed using HPLC with a fluorescence detector. The concentrations of ciprofloxacin and enrofloxacin in muscle increased during the medication period, and then decreased rapidly. The ciprofloxacin and enrofloxacin concentration in the olive flounder peaked on days 11 and 13, respectively, with maximum concentrations in muscle of 0.58 and 0.73 mg/kg. Residual ciprofloxacin and enrofloxacin were eliminated rapidly; 6 days after treatment, the respective levels in muscle were 0.04 and 0.10 mg/kg and neither was detected 15 days post treatment. The level of ciprofloxacin accumulation at the beginning of oral administration was variable according to the farming conditions, but the overall exhaustion time was similar. In conclusion, an adequate withdrawal period for enrofloxacin is 15 days in the case of oral ciprofloxacin administration.

Carp vitellogenin detection by an optical waveguide lightmode spectroscopy biosensor

A label-free carp vitellogenin sensor has a strong potential for on-site monitoring on the possible contamination of edible fish with endocrine disruptors as a sum parameter in an inland carp farm. In this study, we performed a sensitive detection for carp vitellogenin with a direct-binding optical waveguide lightmode spectroscopy-based immunosensor. Carp vitellogenin bound over the sensor surface quite specifically, judging from the sensor responses according to stepwise antibody immobilization. This was also supported by a negligible sensor response found at bovine serum albumin immobilization. When plotted in double-logarithmic scale for carp vitellogenin concentrations of 0.00675–67.5 nM, a linear relationship was found between analyte concentration and sensor response, together with the limit of detection of 0.00675 nM. The reusability of the immunosensor after the regeneration with 10 mM HCl was reasonably good, as presumed from the coefficient of variability of 6.02% for nine repetitive measurements. The model sample prepared by spiking a purified carp vitellogenin into a 10-fold diluted vitellogenin-free carp serum in 9.45 nM showed the response ratio of 96.70% against 9.45 nM of the purified carp vitellogenin. When a female and male carp sera induced with 17β-estradiol injection were analyzed, biomarker induction was even identifiable at 2000-fold serum dilution.

Salt Discharge from an Inland Farm for Marine Shrimp in Alabama

Abstract The total salt input in saline well water, mineral amendments, feed, and rainfall and runoff to ponds of an inland shrimp farm in Alabama was 1980.8 tonnes over a 5‐yr period. A residual of 270.4 tonnes of salt remained in pond water and 38.3 tonnes in bottom soil. Only 8.0 tonnes of salt were removed in harvested shrimp. A total of 1588.0 tonnes of salt or 80.2% of the input was lost to the environment with about equal amounts exiting the ponds in seepage and in overflow and harvest effluent. About 4.2% of the salt input (84.1 tonnes) could not be accounted for because of errors in assumptions and measurements. Salt concentration was elevated in a small stream passing through the farm and in the shallow aquifer beneath it. Needham Creek, the receiving water body for runoff and base flow from the farm watershed, had elevated salt concentrations when ponds were partially drained for harvest in the fall. At this time, chloride concentration exceeded 230 mg/L, the maximum concentration allowed by Alabama Department of Environmental Management regulations. Greater water reuse or more gradual release of pond effluent during harvest would reduce the peak in‐stream chloride concentration and avoid noncompliance with the in‐stream chloride criterion.

Characterisation of the environmental impact of a turbot ( Scophthalmus maximus) re-circulating production system using Life Cycle Assessment

The environmental impacts of a water re-circulating system for fish farming were studied through the case study of an inland turbot farm located in Brittany (France). Life Cycle Assessment methodology was used to evaluate the potential environmental impact through the following indicators: Eutrophication Potential, Acidification Potential, Global Warming Potential, Net Primary Production Use and Non Renewable Energy Use. Two methods were used to assess the farm's nitrogen, phosphorus and solids emissions: nutrient measurement accounting and nutrient balance modelling. The two methods gave similar results for solids and phosphorus emissions, while for nitrogen the measurement-based approach resulted in half the emissions predicted by the model. The uncertainty regarding the potential gaseous nitrogen emissions led us to assess impacts according to three scenarios, differing with respect to emissions of N 2, N 2O and NH 3. This approach illustrates that the uncertainty concerning nitrogenous emissions to the atmosphere leads to uncertainty with respect to the production system's Eutrophication Potential and its Global Warming Potential. The comparison of our results with similar results for large rainbow trout production in a flow-through system points out the impacts associated with the high level of energy consumption in the studied re-circulating system (i.e. Non Renewable Energy Use, Global Warming potential, Acidification Potential). The nitrogenous gas emissions of re-circulating systems require further studies, in order to precisely identify the substances involved and the technological solutions allowing reduced impacts.

Climate change and the emergence of Vibrio vulnificus disease in Israel

In 1996, a major unexplained outbreak of systemic Vibrio vulnificus infection erupted among Israeli fish market workers. The origins of this emergent infectious disease have not been fully understood. A possible link between climate change and disease emergence is being investigated. Meteorological service data from 1981, the earliest detection and reporting of V. vulnificus for the time in Israel, to 1998 for two stations located within the main inland fish farm industry were analyzed. The 1996–1998 summers were identified as the hottest ever recorded in Israel in the previous 40 years. Time series of monthly minimum, maximum, and mean temperatures showed significant increase in the summer temperatures along the 18 years. The highest minimum temperature value was recorded in summer 1996. Lag correlation analysis revealed significant correlations between temperature values and hospital admission dates. The eruption appeared 25–30 days after the extreme heat conditions in summer 1996, at a lag of 3 weeks in summer 1997 while the results for 1998 were at a lag of less than a week. Higher significant results were detected for the daily minimum temperatures in summer 1996 compatible with the disease eruption. These findings suggest that high water temperature might have impacted the ecology of our study area and caused the emergence of the disease, as an effect of global climate change.

Production of the Pacific White Shrimp, Litopenaeus vannamei, in High-Density Greenhouse-Enclosed Raceways Using Low Salinity Groundwater

Two nursery trials and one grow-out culture trial with Pacific white shrimp, Litopenaeus vannamei, were conducted at an inland farm near Gila Bend, Arizona, using low-salinity (1.8 to 2.6 ppt) ground-water. Trials were conducted in greenhouse-enclosed concrete raceways with bottom area of 97.5 m2 and water volume of 147.6 m3. Excellent survival (98.1±12.9%), FCR (0.7:1), and yield (2.22±0.17 kg/m2) were obtained in a five-week nursery study with stocking density of about 20,000 postlarvae/m2. In the grow-out trial, survival as high as 86% and a yield of 4.39 kg/m2 of shrimp with a mean weight of 14.7 g were achieved in 107 days from an initial mean weight of 0.5 g. These trials indicate that the Pacific white shrimp can be raised at very high densities with good survival using low-salinity groundwater. Composition of the groundwater is reported.

Hunting, fishing and animal husbandry at The Farm Beneath The Sand, western Greenland

A large and generally well preserved sample of animal bones was excavated at "The Farm Beneath The Sand" (Gården under Sandet, GUS) in the Norse Western Settlement in Greenland. The sample represents the entire period of occupation, from ea. AD 1000-1400 and could be divided into three time phases, allowing analysis of changes in the economy of the farm. A total of 8,250 bone fragments, from at least 36 species of fish, birds and mammals, were identified. The 166 fish bones from GUS constitute the hitherto largest sample from a Norse site in Greenland. The generally poor state of preservation of the fish bones, in combination with the fact that fish bones were only found in sieved samples, indicate that fishing may have played a larger role than the sheer number of fish bones indicates. The majority of the fish bones are from Arctic char (Salvelinus alpinus), followed by cod (Gadus morhua) and capelin (Ma/lotus villosus). The material of bird bones is strongly dominated by ptarmigan (Lagopus mutus), but there are also bones of, e.g., geese, auks, whooper swan (Cygnus cygnus), mallard (Anas platyrhynchos) and eider (Somateria mollissima). Remains of wings of White-tailed eagle (Haliaeetus albicilla) and a goose were found. The GUS people exploited the wild mammal fauna but also kept domestic animals. Bones of seals numerically dominate the mammal bone material. Reindeer (Rangifer tarandus) was also important, and Arctic hare (Lepus arcticus) was a smaller but constant element. Second in numerical importance among the mammals is sheep+goat which strongly dominate among the domestic animals. Right from the first time phase, the number of goats (Capra hircus) almost equals that of sheep (Ovis aries). The find of a complete goat skeleton is of particular interest. Cattle (Bos taurus) was also kept at GUS, whereas the find of only a single bone of swine (Sus domesticus) does not prove pig husbandry. Measurements of metacarpal and metatarsal bones indicate that sheep, goats and cattle were small and stout. Age estimates based on, i.a., tooth eruption and wear patterns indicate that cattle were kept mainly to provide milk. For sheep and goats, a more mixed exploitation is indicated, however, with the main emphasis on meat production. There are several indications of temporal changes in the economy of GUS: The exploitation of seals increases, and while common seal (Phoca vitulina) dominates the first phases, there is a change towards dominance of harp seal (Phom groenlandirn) in the later phase. The exploitation of reindeer decreases, sheep and goat become slightly more numerous, and cattle becomes scarcer. GUS was an inland farm, and its overall economy seems to have been strongly based on exploitation of the inland fauna: hunting of ptarmigan, geese, reindeer and hare; seals brought in from nearby breeding grounds; fishing for char, maybe at the mouth of the river in the nearby fjord. Hunting and fishing was combined with animal husbandry dominated by sheep and goats, and with a little cattle. Excursions must have been made to the seacoast to obtain harp seals and walruses (Odoben11s rosmarus). Throughout the period of occupation the relation between bone fragments of wild and domestic mammals was ea. 1:1, whereas the animal food gradually became more dominated by marine species: in phase 1, 29% of the fragments are from marine species, versus 44% in phase 3. A fair number of bones from horses and a skull and mandibles from greyhound-type dogs indicate that the farm had a certain level of status.

Seasonal malaria transmission and variation of anopheline density in two distinct endemic areas in Brazilian Amazonia.

Studies on seasonal anopheline fauna variation were performed in two distinct settlements in the State of Rondônia, Brazil: one at the Madeira River banks (Portuchuelo) with stable native Amazonian population; the other at an inland lumber-extracting farm (Urupá) in dry land, in which adults are mostly migrants. During a 6-yr period (1994-2000), 8,638 adult anophelines were collected: 2,684 in Urupá and 5,954 in Portuchuelo. Anopheles darlingi represented >95% of total mosquitoes caught. Dissection of 4,424 A. darlingi females yielded a very low sporozoite infection index below 0.1%. Oocysts were found in both localities in approximately 0.1% of dissected mosquitoes. Determination of the hour biting rates disclosed seasonal variations in both localities. However, in Portuchuelo, mosquito density peaked at the acme of the rainy season, whereas at Urupá it peaked in the dry season. The increase in mosquito density and incidence of malaria cases were coincident. The high mosquito densities observed in the riverine settlement of Portochuelo sector B, which permits evaluation in > 10,000 mosquitoes' bites/person/year, could explain, in spite of the low mosquito's infection index, the previously described development of natural immunity in the local population that is not observed in the dry land agroindustrial settlement of Urupá.