Interspecific synchrony is related to body-length similarity in a fish community under prolonged drought conditions.

Interspecific synchrony and trait-based differences between species are likely to be related to each other. Therefore, we investigated interspecific synchrony patterns in a fish community under prolonged drought conditions, using a trait-based approach. We hypothesized that trait-similarity would predict interspecific synchrony among fish populations. We also expected that a general synchronous pattern for the whole community would be high during a severe drought context, indicating low stability. The study was conducted in a semi-arid reservoir between 2010 and 2017, which encompassed a five-year period of severe drought. We considered species differences in body length, gonadosomatic index, relative condition factor, and trophic level and found that interspecific synchrony was negatively related to species differences in body length. This result can be related to species requirements in terms of habitats and food resources. We also found a significant level of community-wide synchrony, with important implications for community stability during periods of prolonged drought. In conclusion, our results indicated a strong effect of environmental filtering in fish population dynamics over time. We highlight the importance of a trait-based approach to shed light on understanding ecological processes driving population dynamics.

An evaluation of the economic viability of environmental offsets in the saltworks industry / Uma avaliação da viabilidade econômica de compensações ambientais na indústria salineira

ABSTRACT: The extraction of sea salt depends on the occupation of large areas at the estuary banks, many of them inserted in Permanent Preservation Areas (PPAs). Thus, the objective was to evaluate the economic viability of Environmental Offsets (EO) as an alternative to the unoccupied PPAs in the saltworks. In order to do so, 27 solar saltworks installed in the region of the Brazilian White Coast were evaluated for the occupation of PPAs - measured using images from satellite, georeferenced, vectored with corresponding PPA bands generated - and estimated to EO (Impact Degree x Sum of the investments necessary to implement the project) and Economic Impact (Net Present Value, with long-term interest rate of 7%) of vacating PPAs. It was considered that EO was feasible whenever the costs resulting from it were lower than the economic impact caused by the vacancy of the PPAs. The PPAs were tthe productive area of ​​the saltworksthat occupied 13.70% of PPAs. For all the evaluated enterprises the value corresponding to EO was lower than the Economic Impact resulting from the vacancy of the PPAs. Thus, EO is an economically viable and more attractive alternative to the eviction of PPAs by the saltworks industry and may also provide environmental gains due to the financing of conservation units in the areas of influence of the enterprises. However, there is a need to improve the methodology used to estimate the EO, since a maximum limit is set, the environmental impacts caused by the projects are underestimated.

RESUMO: A extração de sal marinho depende da ocupação de grandes áreas às margens de estuários, muitas delas inseridas em Áreas de Preservação Permanente (APPs). Assim, objetivou-se avaliar a viabilidade econômica da Compensação Ambiental (CA) como alternativa à desocupação de APP pelas salinas. Para tanto, 27 salinas instaladas na região da Costa Branca brasileira foram avaliadas quanto à ocupação de APPs - mensuradas por meio de imagens de satélites, georreferenciadas, vetorizadas com a geração de bandas de APP - e estimados a CA (Grau de Impacto x Somatório dos investimentos necessários para implantação do empreendimento) e o Impacto Econômico (Valor Presente Líquido, com taxa de juros de longo prazo de 7%) da desocupação das APPs. A CA foi considerada viável quando seus custos resultantes foram menor do que o impacto econômico causado pela desocupação das APPs. A área produtiva média das salinas ocupa 13,70% de APP. Para todos os empreendimentos avaliados, o valor correspondente a CA foi menor que o Impacto Econômico resultante da desocupação das APP. Assim, a CA é uma alternativa economicamente viável e mais atrativa frente à desocupação das APP pela indústria salineira, podendo ainda propiciar ganhos ambientais em decorrência do financiamento de Unidades de Conservação nas áreas de influência dos empreendimentos. Evidencia-se, contudo, a necessidade do aprimoramento da metodologia usada para estimar a CA, já que fixado um limite máximo, os impactos ambientais provocados pelos empreendimentos são subestimados.

Effects of a Supraseasonal Drought on the Ecological Attributes of Plagioscion squamosissimus (Heckel, 1840) (Pisces, Sciaenidae) in a Brazilian Reservoir.

The aim of this study was to evaluate the effect of a supraseasonal drought on the ecological attributes of Plagioscion squamosissimus. The fish were caught quarterly from February 2010 to November 2014 using gill nets in the reservoir of Santa Cruz, Rio Grande do Norte, Brazil. The abundance of the species was evaluated with the catch per unit effort (CPUE) metric and then correlated with the accumulated rainfall and water volume of the reservoir. The diet of the fish was evaluated using the feeding index (IAi). The proportional similarity index (PS i ) was used to evaluate the variation in the niches of the fish. The body condition was inferred through the relative condition factor, and its variation was assessed with ANOVA. A reduction in the abundance of the species that were positively correlated with the reservoir water volume was observed. The diet of the fish comprised shrimp, gastropods, fish, insects, shrimp larvae, and vegetable matter, with shrimp being the major component. PS i showed the occurrence of individual specialization during November 2013 and November 2014. The relative condition factor was not correlated with a reduction in the water volume of the reservoir. The supraseasonal drought did not affect the relative condition factor, diet, and the trophic niche, but it did affect the species abundance.

Population structure and reproduction of a migratory fish Leporinus piau (Characiformes: Anostomidae) in a semiarid tropical reservoir, Brazil.

Migratory fishes have been seriously impacted by the building of reservoirs and because of the negative effects of these projects such as the interruption of migratory routes, reduction or elimination of spawning/feeding areas, and initial development can influence the population structure the migratory fishes, resulting in reduction in abundance. Leporinus piau is migratory fish widely distributed in the watersheds of the Brazilian semiarid and it is of importance for artisanal and sport fishing. The goal of the study was to evaluate the population structure and reproductive dynamics of the migratory species Leporinus piau in the Pau dos Ferros Reservoir, which is located in the semiarid region of Brazil. The CPUE, length structure, length-weight relationship, length at first maturity, sex ratio, gonad development and IGS were analyzed. Collections were performed quarterly between February 2011 and November 2012 using gillnets. The captured fish were counted; the standard length (cm) and total weight (g) were measured, and dissected to determine the sex and gonad maturity stage. The rainfall and reservoir water levels were recorded, and their correlations with the reproductive period and CPUE were analyzed. A total 549 individuals were captured. The average CPUE varied between 0.0259 individuals/m2*h (May/2011) and 0.0008 individuals/m2*h (August/2012), and significant differences were observed; however, significant correlations were not observed between rainfall and reservoir levels. The standard length varied between 5.9 cm and 20.7 cm, and the weight varied between 4.16 g and 271.5 g. A histogram analysis revealed that the 5-10 cm standard length class was the most abundant for juveniles and that the 10-15 cm class was the most abundant for adult females and males. The weight-length relationship was best fit by the equation log10Wt = -1.57711 + 3.00707 Log10 Ls, and the species presented isometric growth. The estimated length at first maturity was 12.76 cm. A total of 148 males and 82 females were collected (1.81:1, M:F), and these values were significantly different. The highest GSI was observed in February 2011 for both females (10.69) and males (5.72), and the GSI was significantly and positively correlated with rainfall. We concluded that the L. piau population is established in the reservoir and found that its reproduction period occurred during the rainy season between February and May.

Population structure and reproductive period of two introduced fish species in a Brazilian semiarid region reservoir.

The Amazonian fish species Plagioscion squamosissimus (Sciaenidae) and Cichla monoculus Cichlidae), have been widely introduced into different reservoirs in Brazil, and have caused many negative mpacts on local fish fauna. The aim of this study was to evaluate the population structure (abundance, length structure, length-weight relationship, sex ratio, and length at first maturity) and the reprodutive period of these wo species in the Santa Cruz Reservoir (built in 2002), located in the Brazilian semiarid region, for their adequate management and local species conservation policies. Specimens were collected quarterly in eight sites from February 2010 to November 2013 using gillnets (12 to 70 mm mesh between adjacent knots). The specimens captured were counted and the following biometric and biological data were analysed: standard length, total weight, and reproductive data, such as, sex, weight and gonadal maturity stage. The species abundances were estimated by CPUE and expressed as the number of individuals per gill net area x gill net exposition time (m2 x h); length frequency histograms were built with intervals of 5 cm. The length-weight parameters were estimated with a linear regression after a logarithmic transformation of the data. With the reproductive data we estimated sex ratio, reproduction period and length at first maturity (L50). We captured a total of 1,071 specimens of P. squamosissimus and 156 specimens of C. monoculus. Both species showed higher abundances in 2010, 0.004306 m2 x h and 0.00022 m2 x h, respectively, but this parameter decreased from 2010 to 2013. Standard length ranged between 6.4 and 46.2 cm for P. squamosissimus (20.025.0 cm was the most frequent class), and 7.0 and 38.7 cm for C. monocidus (10.0-15.0 cm was the most frequent class). The length-weight relationships were described by the following equations: log10Wt = -1.8349+3.0899log10Lp and R2= 0.9795 for P. squamosissimus, and log10 Wt = -1.7944+3.0885log10Lp and Wt = 0.0160 and R2 = 0.9929 for C. monoculus; both species exhibited positive allometric growth. The sex ratio for both species differed from 1:1, with a predominance of females for P. squamosissimus and males for C. monoculus. The Lp50 was estimated to be 15.90 cm for P. squamosissimus and 15.65 cm for C. monoculus, and the reproductive data indicated that both species reproduced throughout the year. We concluded that although the population of both species reduced their abundance over the study period, P. squamosissimus and C. monoculus are established and structured populations in the Santa Cruz Reservoir with individuals growing satisfactorily and reproducing in all seasons, without a well-defined reproductive peak. We suggest that the managers may allow the artisanal and/or sport fisheries of these species.

Population structure and reproductive period of two introduced fish species in a Brazilian semiarid region reservoir / Estructura poblacional y período reproductivo de dos especies introducidas de peces en una represa de una región semiárida brasileña

The Amazonian fish species Plagioscion squamosissimus(Sciaenidae) and Cichla monoculus(Cichlidae), have been widely introduced into different reservoirs in Brazil, and have caused many negative impacts on local fish fauna. The aim of this study was to evaluate the population structure (abundance, length structure, length-weight relationship, sex ratio, and length at first maturity) and the reprodutive period of these two species in the Santa Cruz Reservoir (built in 2002), located in the Brazilian semiarid region, for their adequate management and local species conservation policies. Specimens were collected quarterly in eight sites from February 2010 to November 2013 using gillnets (12 to 70 mm mesh between adjacent knots). The specimens captured were counted and the following biometric and biological data were analysed: standard length, total weight, and reproductive data, such as, sex, weight and gonadal maturity stage. The species abundances were estimated by CPUE and expressed as the number of individuals per gill net area x gill net exposition time (m2 x h); length frequency histograms were built with intervals of 5 cm. The length-weight parameters were estimated with a linear regression after a logarithmic transformation of the data. With the reproductive data we estimated sex ratio, reproduction period and length at first maturity (L50). We captured a total of 1 071 specimens of P. squamosissimusand 156 specimens of C. monoculus.Both species showed higher abundances in 2010, 0.004306 m2 x h and 0.00022 m2 x h, respectively, but this parameter decreased from 2010 to 2013. Standard length ranged between 6.4 and 46.2 cm for P. squamosissimus(20.025.0 cm was the most frequent class), and 7.0 and 38.7 cm for C. monoculus(10.0-15.0 cm was the most frequent class). The length-weight relationships were described by the following equations: log10Wt = -1.8349+3.0899log10Lp and R2 = 0.9795 for P. squamosissimus,and log10Wt = -1.7944+3.0885log10Lp and Wt = 0.0160 and R2 = 0.9929 for C. monoculus;both species exhibited positive allometric growth. The sex ratio for both species differed from 1:1, with a predominance of females for P. squamosissimusand males for C. monoculus.The Lp50 was estimated to be 15.90 cm for P. squa-mosissimusand 15.65 cm for C. monoculus,and the reproductive data indicated that both species reproduced throughout the year. We concluded that although the population of both species reduced their abundance over the study period, P. squamosissimusand C. monoculusare established and structured populations in the Santa Cruz Reservoir with individuals growing satisfactorily and reproducing in all seasons, without a well-defined reproductive peak. We suggest that the managers may allow the artisanal and/or sport fisheries of these species.

Las especies de peces amazónicos Plagioscion squamosissimus(Sciaenidae) y Cichla monoculus(Cichlidae), se han introducido ampliamente en diferentes embalses en Brasil, y han causado muchos impactos negativos sobre la fauna de peces locales. El objetivo de este estudio fue evaluar la estructura poblacio-nal (abundancia, estructura de tallas, relación talla-peso, proporción de sexos, y talla de primera madurez) y el período reproductivo de estas dos especies en la represa Santa Cruz, (construida en el 2002), situada en la región semiárida de Brasil. Las muestras se recogieron trimestralmente en ocho sitios de febrero 2010 a noviembre 2013 mediante redes de pesca (12 a 70 mm). Los ejemplares capturados se contaron y se analizaron los siguientes datos bio-métricos y biológicos: longitud estándar, peso total, y datos reproductivos, tales como: sexo, peso y estado de madurez gonadal. Capturamos un total de 1 071 ejemplares de P. squamosis-simusy 156 de C. monoculus.Ambas especies mostraron mayor abundancia en el 2010, 0.004306 m2 x h y 0.00022 m2 x h, respectivamente, pero este parámetro disminuyó de 2010 a 2013. La longitud estándar osciló entre 6.4 y 46.2 cm para P squamosissimusy 7.0 y 38.7 cm para C. monoculus.Las relaciones talla-peso fueron descritas por las siguientes ecuaciones: log10Wt = -1.8349 + 3.0899log10Lp y R2 = 0.9795 para P squamosissimusy log10Wt = -1.7944 + 3.0885log10Lp y Wt = 0.0160 yR2 = 0.9929 para C. monoculus;ambas especies mostraron un crecimiento alométrico positivo. La proporción de sexos para ambas especies difirió de 1:1, con un predominio de hembras en P. squamosissimusy machos en C. monoculus.El LP50 se estimó en 15.90 cm para P. squamosissimusy 15.65 cm para C. monoculus,los datos de reproducción indicaron que ambas especies se reproducen durante todo el año. Llegamos a la conclusión de que aunque la población de ambas especies redujo su abundancia durante el período de estudio, P. squamosissimusy C. monoculusestán ...

Analysis of artisanal fisheries in two reservoirs of the upper Parana River basin (Southeastern Brazil)

We compared the artisanal fisheries, in terms of catch strategies, productivity, and gross per capita income, at two reservoirs: the Barra Bonita (an eutrophic reservoir with some introduced species), and the Jurumirim (an oligotrophic reservoir, with no introduced species). Published data and structured interviews with fishers were used to evaluate fishing activity, fish biomass, and the financial performance of the fisheries. In the Barra Bonita Reservoir we analysed data from 745 fishing trips, from which 86,691.9 kg of fish were landed, with a mean CPUE of 62.4 kg/fisher-1 day-1. The main type of fish caught was tilapia (71,513.5 kg; CPUE of 51.5 kg/fisher-1 day-1), which constituted 82.5% of the biomass caught. In the Jurumirim Reservoir, we analysed data from 2,401 fishing trips, from which 25,093.6 kg of fish were landed, with a mean CPUE of 10.4 kg/fisher-1 day-1. The main type of fish caught was "traíra" (6,158.6 kg; CPUE of 2.6 kg/fisher-1 day-1), which constituted 24.5% of the biomass caught. Ordination analysis (PCA) indicated that there was a difference in composition between the fishing reservoirs and ANCOVA showed that there was a significant difference in fish production between the reservoirs. A Student's t-test showed that fishers in the Barra Bonita Reservoir had a significantly higher gross per capita income than those from the Jurumirim Reservoir. Although the Barra Bonita Reservoir has a higher fish production and the fishers earn a higher gross per capita income, we recommend the Jurumirim Reservoir as a model for artisanal fishery management because fishing activity in this reservoir is viable in the long term and such a model would promote conservation and sustainability. This contrasts with the Barra Bonita Reservoir, in which the fishery is not viable in the long term, due to environmental problems caused by artificial eutrophication and the introduction of alien species. It is also noted that in many countries, management of fisheries based on exotic species has not been viable in the long term.

Nós comparamos a pesca artesanal, em termo de estratégia de captura, produtividade e renda per capita bruta em dois reservatórios: Barra Bonita (reservatório eutrófico e com espécies introduzidas) e Jurumirim (reservatório oligotrófico e sem espécies introduzidas). Dados publicados e entrevistas estruturadas mensais com os pescadores sobre a atividade de pesca, quilo pescado e rendimento financeiro, foram usados para as análises. No reservatório de Barra Bonita foram analisados dados de 745 viagens pesqueiras, que desembarcaram 86.691,9 kg de pescado, com CPUE de 62,4 kg/pescador-1 dia-1. O principal pescado foi a tilápia (71.513,5 kg, CPUE de 51,5 kg/pescador-1dia-1) que representou 82,5% da biomassa pescada. No reservatório de Jurumirim analisamos dados de 2.401 viagens pesqueiras, que desembarcaram 25.093,6, como CPUE de 10, kg/ pescador-1 dia-1. O principal pescado foi a traíra (6.158,6 kg, CPUE de 2,6 kg pescador-1 dia-1), que representou 24,5% da biomassa pescada. Uma análise de ordenação (PCA) indicou diferença na composição pesqueira entre os reservatórios e uma ANCOVA indicou diferença na produção pesqueira entre os reservatórios. Teste t de Student foi significativo e os pescadores do reservatório de Barra Bonita tiveram maior renda per capita bruta. Embora o reservatório de Barra Bonita tenha tido maior produção pesqueira e os pescadores maior renda, recomendamos o reservatório de Jurumirim como modelo para gestão de pesca artesanal nos reservatório, pois a atividade mostrou ser viável em longo prazo bem como ecologicamente correto. Isto contrasta como o reservatório de Barra Bonita, em que a pesca não é viável em longo prazo, devido a problemas ambientais provocados pela eutrofização artificial e pela introdução de espécie. Observou-se que em muitos países, o manejo da pesca com espécies exóticas, não tem sido viável em longo prazo.

Reproduction, food dynamics and exploitation level of Oreochromis niloticus (Perciformes: Cichlidae) from artisanal fisheries in Barra Bonita Reservoir, Brazil.

Nile tilapia (Oreochromis niloticus), which is exotic to South America, is the most common species caught in artisanal fisheries at the Barra Bonita Reservoir, Southeastern Brazil. This species is of great socioeconomic importance for the region and keeps active a population of about 500 fishers. In the present study we assess reproduction, food dynamics and level of exploitation of O. niloticus, caught by artisanal fisheries in the Barra Bonita Reservoir. Specimens were collected monthly, from July 2004-June 2005, and a total of 1 715 specimens were analyzed. Each specimen was examined to obtain biological and biometric data: standard length (cm), total weight (g), reproductive data (sex and stage of maturation), and stomach contents (empty, partly full, and full). We also estimated the sex ratio (by macroscopic observation of gonads), reproductive period (by ovarian development and seasonal average of gonadosomatic index in females), and feeding habits (by stomach contents). The possible relationship between abiotic factors and the reproductive period was statistically verified using Spearman's Rank Correlation. The FiSAT (ELEFAN I) package was used to assess growth parameters, mortality rates and to infer exploitation rate from standard length frequencies. The O. niloticus population had a sex ratio of 1.3:1 (M:F). Results indicated that ripe females were captured throughout the year, with a higher frequency during the winter-2004 (with a frequency of 59%, at a mean temperature of 20.5 degreeC), and in spring-2004 (with a frequency of 60.5% at a mean temperature of 21.18 degreeC). The GSI mean values obtained by season were: winter-2004: 1.71; spring-2004: 1.72; summer-2005: 0.80, and autumn-2005: 1.19. The Spearman correlation indicated positive values with respect to pH, dissolved oxygen, electric conductivity, transparency and chlorophyll a, and negative values with respect to temperature, accumulated rainfall and altimetric benchmark. The main food items were phytoplankton and periphytic algae, observed in 99.6% of the analyzed stomachs. The estimated growth and mortality parameters were: Linfinity=33.60cm, k=0.63/year, longevity= 4.76years, Z=2.81/ year, M=1.20/year and F=1.61/year. The weight-length relationship was Ln Wt=-2.8532+2.8835 Ln Lp. The estimated yield per recruit values were as follows: E=0.570, Emax=0.776, E0.1=0.604 and E0.5=0.349. These results indicate that a well established population of O. niloticus is present at Barra Bonita Reservoir; with an active reproduction throughout the year, more intense during winter and spring, and that O. niloticus is a phyto-planktophagus species. There were no indications that this species is being overfished, we therefore recommend that, due to its exotic condition, no restrictions need to be taken on its fishing activities.

Population structure and stock assessment of Hoplias malabaricus (Characiformes: Erythrinidae) caught by artisanal fishermen in river-reservoir transition area in Brazil.

Hoplias malabaricus is a viable economic alternative for artisanal fishermen who used to live on the banks of rivers that now are dammed in Brazil. In order to preserve the species' natural stock, the main objectives of this study were to obtain bio-ecological information on this species reproduction, feeding dynamics and the description of the extent of its exploitation in river-reservoir transition area in Brazil. This way, from January to December 2005, different fishery catches were made with gill nets by artisanal fishermen, and a total of 426 individual H. malabaricus were obtained and sampled. From each specimen, the following biometric and biological data were analyzed: standard length, total weight, stomach contents, reproductive data such as sex, weight and gonadal maturation stage; with these data we estimated sex ratio, reproduction period and feeding habits. To assess growth parameters and infer on the degree of exploitation, the standard length frequency data were analysed using the FISAT (ELEFAN I) computer program. Data revealed a sex ratio of 0.8:1 (M:F), that reproduction occurs all year around, being more intense during spring and summer; it also showed that H. malabaricus is piscivorous. The growth parameters and mortality were estimated at: L(infinity) = 35.18 cm, k = 0.32 year, longevity = 9.3 years, Z = 1.25 years, M = 0.63 year and F = 0.62 year. The weight-length relationship was: In Wt = -3.1663+2.7456 In Lp. The yield-per-recruit analysis produced the following values: E = 0.496, E(max) = 0.916, E0.1 = 0.701 and E0.5 = 0.378. Overall, our data suggest that the stock of H. malabaricus is not yet overfished in the studied area.

Population structure of two Astyanax Baird & Girard, 1854 (Teleostei, Characidae) species from upper Paraguaçu river

The fishes of the family Characidae are among the main species of fresh water fishes in South America. In this work, some aspects of the population structure of two Astyanax species were assessed. The fishes were caught in Santo Antônio and São José rivers, in the Paraguaçu basin, by standardized monthly samplings adapted to the microhabitats. Astyanax sp. b (São José river) presented larger size than Astyanax sp. a (Santo Antônio river). The length-weight relationship showed positive allometric growth for Astyanax sp. a, and negative for Astyanax sp. b. Both the species showed a long reproductive period, with higher activities in dry period.

Os peixes da família Characidae estão entre os principais representantes de peixes de água doce da região Neotropical. Este trabalho apresenta alguns aspectos da estrutura populacional de duas espécies de Astyanax coletadas a partir de amostragens mensais padronizadas e adaptadas a diferentes microhabitats, em trechos dos rios Santo Antônio e São José, tributários do alto curso do rio Paraguaçu. Astyanax sp. b, coletada no rio São José apresentou maior tamanho que Astyanax sp. a, coletada no rio Santo Antônio. A relação peso-comprimento indicou um crescimento alométrico positivo para Astyanax sp. a e negativo para Astyanax sp. b. Ambas as espécies apresentaram um longo período reprodutivo, com maior atividade reprodutiva no período seco.