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Abundance and distribution of fish larvae in the channel area of the Patos Lagoon Estuary, Brazil
(1991) Muelbert, José Henrique; Weiss, Graciela
Distribution and abundance of fish larvae in the channel area of the Patos Lagoon, Brazil are reported. The Patos Lagoon is a shallow coastal lagoon with a very narrow connection with the Atlantic Ocean. Its southernmost region, characterized by a very dynamic estuary, was the site of 32 ichthyoplankton surveys conducted at 5 stations from April 1981 to March 1983. Samples were taken at 3 depth levels (surface, mid-water and bottom) and results indicated that larval density and distribution were associated with temperature. Larvae occurred year round and at all stations, but were most abundant and diverse during spring and summer with mean densities of 61/100 m3 and 189/100 m3 , respectively. However, this distribution was sometimes altered by meteorological conditions prevailing in the estuary. Twenty families of fishes were represented, including 27 taxa, 19 of which were identified to species. The three most abundant taxa overall were Mieropogonias fumieri, Brevoortia peetinata, and Lyeengraulis sp., whose larvae accounted for 22.9, 22.6, and 20% of the total, respectively. Parapimelodus valeneiennis; Blennidae; Triehiurus lepturus; Gobiesox strumosus; Paralonehurus brasiliensis; Maerodon aneylodon; Paraliehthys sp.; Atherinidae; Gobiosoma parri; and Mentieirrhus spp. had relative abundances between 1 and 5%.
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Abundance estimate for a threatened population of franciscana dolphins in southern coastal Brazil: uncertainties and management implications
(2010) Danilewicz, Daniel; Moreno, Ignacio Benites; Ott, Paulo Henrique; Tavares, Maurício; Azevedo, Alexandre de Freitas; Secchi, Eduardo Resende; Andriolo, Artur
The franciscana dolphin has been considered the most threatened small cetacean in the south-western Atlantic Ocean due to gillnet by-catch. The estimation of the species’ abundance has been recommended as the highest research priority. A line transect aerial survey to estimate franciscana abundance in Rio Grande do Sul, southern Brazil, was carried out in February 2004.The overall surveyed area comprised 13,341 km2 and at least 20 transect lines. Abundance was estimated using distance sampling methods and assuming g(0) ¼ 0.304. The corrected density is 0.51 franciscanas/km2, resulting in an abundance estimation of 6839 franciscanas (CV ¼ 32%; 95% CI ¼ 3709–12,594) for the surveyed area in Rio Grande do Sul. To improve this estimate: (a) perception bias should be determined; (b) the parameters influencing availability bias should be identified and quantified; and (c) survey sample size should be increased. While the lack of data to correct for perception bias and group size underestimation in this aerial survey is likely to yield an underestimate of franciscana abundance, the use of surfacing and diving time data from boat and land-based surveys to correct for availability bias is likely to cause its overestimation. Alternative values of the g0 group-size estimates and rates of increase were incorporated in the analyses, creating 240 different estimates of annual increment for this franciscana population. Even in the most optimistic scenario, the annual increment of franciscanas is not sustainable with the current levels of by-catch in Rio Grande do Sul, and fishery management to reduce by-catch must be initiated promptly.
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Abundance of bottlenose dolphins, Tursiops truncatus (Cetacea: Delphinidae), inhabiting the Patos Lagoon estuary, southern Brazil: Implications for conservation
(2011) Fruet, Pedro Friedrich; Secchi, Eduardo Resende; Di Tullio, Juliana Couto; Kinas, Paul Gerhard
A new mark-recapture abundance estimate and a photographic census were carried out to investigate the possible decline in the abundance of the bottlenose dolphins, Tursiops truncatus (Montagu, 1821), in the Patos Lagoon estuary due to the high levels of bycatch mortality which occurred between 2002 and 2006 in oceanic coastal areas close to the estuary. Fourteen systematic boat surveys were conducted between August and early December 2005 to photo-identify the bottlenose dolphins. The estimated number of animals, with long-lasting marks, in the population obtained from Chapman's and Mth models were 51 (95% CI = 49-53) and 52 (95% CI = 51-60), respectively. Taking into account the proportion of dolphins with long-lasting marks in the population, the total estimated population size ranged between 84 (95% CI = 76-93) and 86 (95% CI = 78-95) individuals, respectively, which was very similar to the 84 individuals revealed by the population census. Our results did not differ from the abundance estimate carried out in 1998, prior to the high fishing-related mortality event, suggesting that the population is stable. Plausible argument to explain the stability of the population is that some carcasses found on the oceanic coastal beaches near Patos Lagoon estuary come from animals that do not belong to the estuary community. Future studies should investigate fine-scale habitat partition between estuarine and adjacent coastal dolphins. If the existence of different communities living in close proximity (estuarine and coastal areas near to the estuary) is confirmed, a new abundance estimate is needed to access the conservation status of bottlenose dolphins in this region.
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Abundance, distribution and population dynamics of the short fin squid illex argentinus in southeastern and southern Brazil
(2013) Haimovici, Manuel; Santos, Roberta Aguiar dos; Bainy, Mara Cristiane Rodrigues Silveira; Fischer, Luciano Gomes; Cardoso, Luis Gustavo
Surveys and commercial fishing landings data of the short fin squid Illex argentinus were analyzed to address three related issues: the seasonal and spatial pattern of abundance; seasonal and regional variation of growth and maturation; and the interannual variation in the size at maturity and growth from Southern Brazil (SB, 28◦–34◦S) and Southeastern Brazil (SEB, 23◦–28◦S). Overall, 2455 specimens were examined for maturity and 337 specimens had their daily increments in the statoliths recorded. Aged specimens from SB ranged from 51 to 275 days, 55 to 354 mm ML and 2.4 to 1098 g. It was observed that (1) I. argentinus is a common component of the nekton on all the outer shelf and slope and appears to be more abundant south of Santa Marta Grande Cape, where the largest catches were obtained in the autumn survey. (2) Spawning and hatching occurs year round along all the region. (3) In SB growth was faster and maturity was attained at larger sizes in the cold season (June to November) and no differences between seasons were observed in the mean age of mature specimens. (4) In 2001/2002, growth was faster, mature squids were in mean 159 days old and most were under 210 days, in 2007/2008, growth was slower, mean mature age was 191 days and most were 250 days. (5) In SEB, maturity was attained at smaller sizes and it is likely that maturity is attained at a lower age and the lifespan is shorter. In the northern range of its distribution I. argentinus is characterized by a decreasing adult size toward lower latitudes, a short and variable lifespan with hatching and spawning in all seasons
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Abundância do bacterioplâncton e suas relações com fatores físico-químicos e biológicos em nove lagos rasos do Campus Carreiros – Furg, Rio Grande – RS (Brasil)
(2009) Souza, Neusiane Chaves de; Abreu, Paulo Cesar Oliveira Vergne de
Neste estudo procurou-se determinar quais fatores controlam a abundância de bactérias livres (BL) e aderidas a partículas (BA) em nove lagos presentes no Campus Carreiros da FURG, na região sul da planície costeira do Rio Grande do Sul. Concentração de oxigênio dissolvido, seston, nutrientes dissolvidos (amônia, nitrito, nitrato e fosfato), clorofila a e a abundância de bactérias, flagelados e ciliados foram determinadas em uma única coleta realizada em 10 de setembro de 2007. Não foi encontrada relação direta entre a concentração da clorofila a e a abundância bacteriana, o que permite supor que o principal aporte de carbono orgânico dissolvido para as bactérias é proveniente da decomposição da matéria orgânica oriunda da decomposição de macrófitas aquáticas e de plantas do entorno dos lagos. Contudo, foi observada uma relação inversa entre o oxigênio dissolvido e as BA, além de uma relação direta destas com o seston. Também foi encontrada uma relação positiva entre as BA e os flagelados heterotróficos e iliados, indicando um possível controle Top-Down”. Já as BL apresentaram uma correlação positiva apenas com a oncentração de fosfato dissolvido, caracterizando um controle “Bottom-Up”.
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Abundância e diversidade da assembléia de crustáceos decápodes dentro e fora de uma pradaria de Ruppia maritima L., no estuário da Lagoa dos Patos (RS-Brasil)
(1996) Garcia, Alexandre Miranda; Vieira Sobrinho, João Paes; Bemvenuti, Carlos Emílio; Geraldi, Ricardo Marcelo
Fortnightly beam trawl samples, collected daily and nightly, were used to ... and diversity of decapod crustaceans inhabiting widgeon grass (Ruppia marítima. Linnaeus, 1753) and nearby unvegetated habitats in the shallow water of Patos Lagoon estuary, from December/1994through March/'l 995, following Ruppia bed's developmentdevelopment and senescence. Collections at both study sites produced 26,325 individualsand six decapod species: Penaeus paulensis Peres-Farfante, 1967, Palaeomonetes argentinus (Nobil, 1901, Callinectes sapidus Rathbun, 1895, Calinectes danae Smith, 1869, Cyrtograpsus angulatus Dana, 1851, and Rhithropanopus harrisse Gould, 1841. Abundance was significantly higher in Ruppia's meadows than in unvegetated areas, except for the crab C.danae. As well, diversity was righer in widgeon beds, mainly because the crustaoeanss abundance was more evenly distributed in the vegetated habtat. Patos Lagoon widgeon beads play a nursery role for decapod crusataceans, including commercially important cruantaceans species, as pink shrump )P. paulensis) an blue Crab (C. sapidus).
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Abundância e diversidade da assembléia de peixes dentro e fora de uma pradaria de Ruppia maritima L., no estuário da Lagoa dos Patos (RS-Brasil)
(1997) Garcia, Alexandre Miranda; Vieira Sobrinho, João Paes
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Acartia tonsa production in the patos lagoon estuary, Brazil
(2012) Muxagata, Erik; Amaral, Waldemar José Appolinário; Barbosa, Carla Neme
Acartid copepods are abundant in estuaries, harbours, and semi-enclosed waters. A monitoring programme with the objective of evaluating copepod production, particularly that of Acartia tonsa, the dominant taxon in the Patos Lagoon estuary, was implemented. Zooplankton samples are collected monthly from two fixed locations with bongo nets 30 cm in diameter with nets of 90 and 200 mm mesh. Over a full year, 33 quantitative samples were analysed; copepods represented 40% of the organisms collected with the 90-mm mesh. Adults and copepodites of A. tonsa accounted for 19% of the total copepod fauna at both locations. Daily production rates of A. tonsa were calculated as 0.40 mg C m23 d21 for the inner estuary and 3.65 mg C m23 d21 in the channel. The value of 1 333 mg C m23 year21 calculated for A. tonsa at the channel station is very high relative to the situation in other estuaries, indicating that the estuary has a high production of copepods.
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Acclimation of juvenile mugil iiza valenciennes, 1836 (mugiliformes: mugilidae) to different environmental salinities
(2015) Lisboa, Viviana; Barcarolli, Indianara Fernanda; Sampaio, Luís André Nassr de; Bianchini, Adalto
Survival and physiological parameters associated with metabolism and osmoregulation were evaluated in juveniles of the Lebranche mullet Mugil liza acclimated to different water salinities (5, 10, 20, 30, and 40‰) for 15 days. Room temperature (25°C) and photoperiod (12L:12D) were fixed. Fish were fed twice-a-day with commercial diet (28% crude protein) until satiation. After acclimation, whole body oxygen consumption was measured and fish were euthanized and sampled for blood, gills, and liver. Whole body oxygen consumption and plasma osmolality did not change in the range of salinities tested. The isosmotic point was estimated as 412.7 mOsmol kg-1 (13.5‰). Gill Na+ ,K+-ATPase activity tended to be lower at 20 and 30‰, while liver glycogen content was significantly higher at 20‰ than at 5 and 40‰. These results indicate that juvenile M. liza is able to acclimate for a short-period of time (15 days) to a wide range of salinities (5-40‰). This condition is achieved through adjustments in gill Na+ ,K+-ATPase activity and carbohydrate metabolism to regulate plasma osmolality and aerobic/energy metabolism. Therefore, our findings support the idea of catching juveniles M. liza in sea water and rear them in estuarine and marine waters.
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Accumulations of the surf diatom Asterionellopsis glacialis in Cassino beach, southern Brazil, and its relationship with environmental factors
(2003) Rörig, Leonardo Rubi; Garcia, Virginia Maria Tavano
Cassino Beach (lat. 32°13’S, long. 52°15’W, Southern Brazil) is an exposed, intermediate to dissipative sandy beach, where dense accumulations of the diatom Asterionellopsis glacialis occur in the surf zone. The frequency of these accumulations, their forcing factors and resulting biomass have been investigated along a weekly sampling program from June/1992 to August/1993 at a fixed station. Data on cell densities, chlorophyll a, physical-chemical variables of surf-zone water, beach morphodynamics features and local meteorological conditions were collected. In addition, nearshore sediment and water (just behind the surf-zone) were collected to determine the density of A. glacialis cells, along with some physical-chemical variables of sea water. Results have shown that cell stocks of A. glacialis are resuspended from the nearshore epibenthic habitat by breaking waves and accumulated at the inner surf zone by shoreward water motion. This physically controlled process result in large phytoplankton biomass concentration, which is available to the trophic chains of the beach and surf zone ecosystem.. Mean chlorophyll a concentration(50.2 μg.l-1) was greater than levels found in adjacent neritic and estuarine waters.Dissolved inorganic nutrients concentrations were relatively high during most of the study period (average values: NO3+NO2+NH4=3.41μM; PO4=1.10μM; SiO4=28.5μM). Although accumulations have been more frequent in winter months, the process could not be regarded as seasonal, since its forcing factors can be effective in any season. These diatom accumulations in Cassino Beach provide an important carbon source for the system, which tends to be self-sustained or even an exporter of organic matter.
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Acúmulo de cromo e seus efeitos na fixação biológica de nitrogênio e absorção de nutrientes em soja
(2001) Castilhos, Danilo Dufech; Guadagnin, Clístenes Antônio; Silva, Marcelo Dutra da; Leitzke, Volnei Wruch; Ferreira, Luis Henrique; Nunes, Maria Cândida
O cromo não possui essenciabilidade comprovada na nutrição das plantas, porém é requerido pelos microrganismos em alguns processos metabólicos específicos. Nesse sentido, elaborou-se o presente trabalho com o objetivo de avaliar os efeitos de doses crescentes de Cr 3+ sobre a produção de matéria seca, absorção de nutrientes e fixação biológica de nitrogênio em plantas de soja. Antes da semeadura as sementes foram tratadas com inóculo turfoso contendo Bradyrhizobium japonicum. As plantas foram cultivadas durante 42 dias em vasos “Leonard” contendo areia lavada na parte superior e solução nutritiva sem nitrogênio na parte inferior. Os tratamentos constaram das seguintes doses de Cr3+ (CrCl3) aplicadas na solução nutritiva: 0, 20, 40, 80 e 160 mg L-1. Foi constatado que concentrações de Cr3+ superiores à 20 mg L-1 diminuíram a produção de matéria seca da parte aérea e radicular da soja, o número e peso de nódulos secos de Bradyrhizobium, como também a fixação biológica de nitrogênio e a absorção de P, K, Ca e Mg. Teores de Cr na parte aérea de plantas de soja superiores à 5,8 mg Kg-1 podem ser considerados fitotóxicos.
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Acute copper toxicity in the euryhaline copepod Acartia tonsa: implications for the development of an estuarine and marine biotic ligand model
(2010) Pinho, Grasiela Lopes Leães; Bianchini, Adalto
Copepods (Acartia tonsa) were exposed (48 h) to waterborne, diet-borne (non-Cu-equilibrated and Cu-equilibrated food), and waterborne plus diet-borne Cu in either the absence or the presence of food (diatom Thalassiosira weissflogii). Toxicity tests were run in different salinities (5, 15, and 30 ppt) together with measurements of physicochemical parameters and total and dissolved Cu concentrations in the experimental media. Results show that most of the toxic Cu fraction was in the dissolved phase. In general, Cu toxicity was higher in low (5 ppt) than in high salinity (30 ppt), regardless of the pathway of Cu exposure tested. In the absence of food, data clearly indicate that differences in waterborne Cu toxicity can be explained by changes in water chemistry. However, addition of food (either non-Cu-equilibrated or Cu-equilibrated) to the experimental media protected against acute Cu toxicity in salinities 5 and 15 ppt, suggesting that A. tonsa requires extra energy to cope with the stressful condition imposed by Cu exposure associated with the ionoregulatory requirements in low salinities. For diet-borne exposure, a very high Cu concentration was necessary to precontaminate the diatoms to a level resulting in copepod mortality. Therefore, availability of food exerted a more important positive impact in protecting against acute Cu toxicity than its potential negative impact via contamination resulting in toxicity. Findings indicate the need for incorporation of both salinity and food in a future biotic ligand model (BLM) version for Cu in estuarine and marine waters. In this context, the euryhaline copepod A. tonsa would be a suitable model species with which to perform experiments to validate and calibrate any future saltwater BLM.
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Acute exposure of juvenile cobia Rachycentron canadum to nitrate induces gill, esophageal and brain damage
(2011) Rodrigues, Ricardo Vieira; Schwarz, Michael; Delbos, Brendan; Carvalho, Eduardo; Romano, Luis Alberto; Sampaio, Luís André Nassr de
Cobia Rachycentron canadum is a fast growing fish with world-wide potential for aquaculture, and has been considered for rearing in recirculating aquaculture systems (RAS). Nitrate is considered the least toxic nitrogenous product in the ammonia nitrification process, but as it may accumulate in RAS, toxic levels can be reached. The objective of this study was to evaluate the acute toxicity and the histopathological effects of nitrate on juvenile cobia. Juveniles (6.87±0.36 g; 11.8±0.19 cm) were acutely exposed to six concentrations of nitrate (500–3000 ppm NO3 −-N) plus a control during 96 h. At the end of this period of exposure, juvenile cobia were sampled for histopathological evaluation. The estimated LC50 of nitrate to juvenile cobia was equal to 2407 and 1829 mg/L NO3 −-N at 24 and 96 h, respectively. Cobia exposed to sub-lethal nitrate concentrations showed histopathologic alterations in the gills, esophagus and brain. The gills revealed epithelial hyperplasia with complete lamellar fusion, telangiectasia, and lamellar shorting induced by necrosis, and the esophagus presented hyperplasia of epithelium and mucus cells. In the brain, glial cells proliferation, satellitosis (microglial cells surrounding neurons with swollen and prenecrotic neurons), and Virchow-Robin spaces (enlarged perivascular spaces, EPVS) were observed. The results of the present study indicate that juvenile cobia have a high tolerance to acute exposure of nitrate. However, assorted histopathological responses were observed for cobia at sub-lethal nitrate concentrations. Therefore, further studies are needed to estimate safe chronic nitrate levels for juvenile cobia culture.
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Acute exposure to microcystin-producing cyanobacterium microcystis aeruginosa alters adult zebrafish (Danio rerio) swimming performance parameters
(2011) Kist, Luiza Wilges; Piato, Angelo Luis; Rosa, João Gabriel Santos da; Koakoski, Gessi; Barcellos, Leonardo José Gil; Yunes, João Sarkis; Bonan, Carla Denise; Bogo, Maurício Reis
Microcystins (MCs) are toxins produced by cyanobacteria (blue-green algae), primarily Microcystis aeruginosa, forming water blooms worldwide. When an organism is exposed to environmental perturbations, alterations in normal behavioral patterns occur. Behavioral repertoire represents the consequence of a diversity of physiological and biochemical alterations. In this study, we assessed behavioral patterns and whole-body cortisol levels of adult zebrafish (Danio rerio) exposed to cell culture of the microcystin-producing cyanobacterium M. aeruginosa (MC-LR, strain RST9501). MC-LR exposure (100 μg/L) decreased by 63% the distance traveled and increased threefold the immobility time when compared to the control group. Interestingly, no significant alterations in the number of line crossings were found at the same MC-LR concentration and time of exposure. When animals were exposed to 50 and 100 μg/L, MC-LR promoted a significant increase (around 93%) in the time spent in the bottom portion of the tank, suggesting an anxiogenic effect. The results also showed that none of the MC-LR concentrations tested promoted significant alterations in absolute turn angle, path efficiency, social behavior, or whole-body cortisol level. These findings indicate that behavior is susceptible toMC-LR exposure and provide evidence for a better understanding of the ecological consequences of toxic algal blooms.
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Acute responses of juvenile cobia Rachycentron canadum (Linnaeus 1766) to acid stress
(2015) Rodrigues, Ricardo Vieira; Pedron, Janaína dos Santos; Romano, Luis Alberto; Tesser, Marcelo Borges; Sampaio, Luís André Nassr de
Fish are potentially submitted to water acidification when reared in recirculating aquaculture systems. This study evaluated the responses of juvenile cobia Rachycentron canadum after acute exposure to acid water. Juvenile cobia (12.6 0.5 g; 14.2 0.2 cm) were acutely exposed to four pH levels (7.9 (control), 6.5, 6.0, and 5.5). After 24 h of exposure to different pH values, fish were sampled for physiological and histopathological evaluation. Acid water affected physiological parameters and induced morphological histopathologies on gill and skin of juvenile cobia, and these effects were more conspicuous with decreasing pH values. Acid stress induced blood acidosis in juvenile cobia, coupled to a decrease in bicarbonate (HCO3 ) and saturated O2 (sO2) in fish blood. On the other hand, haematocrit, haemoglobin and glucose concentration increased their values (P < 0.01) comparing to control level. Hyperplasia with completely fusion of secondary lamella was observed in all pH treatments (6.5. 6.0 and 5.5), while telangiectasia and proliferation of chloride cells were present for fish exposed to pH 6.0 and 5.5. In skin hyperplasia and hypertrophy of mucous cells, necrosis of these cells for fish exposed to pH 6.0 and 5.5 was observed. The results of this study demonstrate that acute acid water exposition affected physiology and histopathology in juvenile cobia, especially at pH values below 6.5. Accordingly, particular attention must be given to pH during cobia reared in recirculating aquaculture.
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Acute tolerance and histopathological effects of ammonia on juvenile maroon clownfish premnas biaculeatus (block 1790)
(2014) Rodrigues, Ricardo Vieira; Romano, Luis Alberto; Schwarz, Michael Hans; Delbos, Brendan; Sampaio, Luís André Nassr de
This study evaluated the median lethal concentra-tion values (LC50) and the histopathological effectsof un-ionized ammonia (NH3--N) on juvenile mar-oon clownfishPremnas biaculeatus. After 96 h ofexposure to different concentrations of ammonia,juveniles were sampled for histopathological evalu-ation. The 24 and 96 h LC50 values of NH3-Ndetermined were 1.68 and 0.89 mg L1respec-tively. Maroon clownfish exposed to differentammonia concentrations displayed histopathologi-cal alterations in the gills, kidney, liver and brain.Gill tissue damage included lamellar hyperplasia,lamellar shorting and hyperplasia and hypertro-phy of mucous cells. The kidney showed hyper-anaemia, enlarged sinusoids within an apparentlydecreased amount of haematopoietic tissue,oedema on tubular cells and tubular necrosis, andan enlarged Bowman’s capsule. The liver presenteddilatation of hepatic sinusoids, fatty deposition inhepatocytes and Mallory bodies. Examination ofthe brain revealed a proliferation of glial cells, andthe Virchow-Robin space indicated a severe peri-vascular oedema and signs of neuronal sufferingwith satellitosis. The results of this study indicatethat juvenile maroon clownfish are relativelysensitive to ammonia and particular attentionmust be given to this toxic compound in culturesystems.
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Acute toxicity and sublethal effects of ammonia and nitrite for juvenile cobia rachycentron canadum
(2007) Rodrigues, Ricardo Vieira; Schwarz, Michael; Delbos, Brendan; Sampaio, Luís André Nassr de
Nitrogenous compounds can be toxic to aquatic animals especially when they are reared at high stocking densities. Cobia (Rachycentron canadum) is a fast growing fish currently reared in cages, but with expanding production in intensive recirculating aquaculture systems (RAS). Therefore, the objective of this study was to evaluate the acute toxicity of ammonia and nitrite to juvenile cobia. Juveniles (1.74±0.11 g for ammonia and 0.88±0.06 g for nitrite toxicity evaluation) were acclimated to test conditions(temperature26°Candsalinity22‰)andacutelyexposedtoammonia(0.25–1.30ppmNH 3-N)andnitrite(30–210ppm NO2-N) at 0.2 fish L − 1. Tests were run in 50 L semi-static tanks, experimental water was fully renewed daily, and all test concentrations plus the controls were run in triplicate. Mortality, feeding and swimming behavior were observed during 96 h, toxic concentrations for 50% the population and the respective 95% confidence intervals for these three end points were estimated using the Trimmed Spearman Karber Method. Cobia ceased to eat at 0.62 (0.56–0.70) ppm NH3-N and 76.1 (73.2–79.0) ppm NO2-N. Swimming behavior was affected at higher concentrations: 0.80 (0.74–0.85) ppm NH3-N and 88.8 (82.6–95.5) ppm NO 2-N. Even higherconcentrationswerenecessarytokilljuvenilecobia,LC50–96hforammoniawasestimatedat1.13(1.06–1.19)ppmNH 3-N, andwithintherangeofconcentrationstestedfornitriteitwasnotpossibletoestimatetheLC50–96h,asonly30%oftheindividuals died at the highest concentration after 96 h (210 ppm NO2-N). The results of the present experiments demonstrate that ammonia couldbeproblematicatrelativelylowlevelsfortheintensiverearingofjuvenilecobia;however,itisunlikelythatthehighlevelsof nitrite needed to harm juvenile cobia would be reached in a well designed and properly operating RAS.
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Add coastal vegetation to the climate critical list: forests are protected, but carbon sinks in mangroves, seagrasses and marshes are ignored
(2011) Copertino, Margareth da Silva
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Advective Surface Velocities Derived from Sequential Infrared Images in the Southwestern Atlantic Ocean
(2000) Domingues, Catia Maria; Gonçalves, Glauber Acunha; Ghisolfi, Renato David; Garcia, Carlos Alberto Eiras
Sequential infrared satellitebeen usedbetween November images 1995 and August 1996 have to derive sea sur- face advective velocities in the southwestern Atlantic Ocean using the Maximum Cross-Correlation (MCC) technique. The infrared images, geometrically corrected and accurately registered to a map grid, are masked for land and cloud cover. The linear displacements of the sea surface thermal features are determined by locating the maximum cross-correlation in windowed portions of suc- cessive images. The advective velocities are estimated for each pair of images based on regular grids. Incoherent vectors are eliminated from these fields using a statistical method. After this, a visual inspection by the operator is completed to remove the remaining fictitious vectors. The region studied includes the southern Brazilian, Uru- guayan, and northern Argentinian shelves and the neigh- boring oceanic area known as the Brazil-Malvinas Con- fluence. Despite the rather complex circulation of this region, the advective surface currents calculated by the MCC method are consistent with the shapes of the sea surface temperature features. The general patterns of the surface circulation estimated by the MCC agree well with previous studies that used direct measurements, hydro- graphic data, and/or modeling efforts. In the shallower areas of the study region, the MCC technique is less ap- plicable due to the predominance, in violation of the as- sumptions of the method, of nonadvective processes.
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Age and changes in growth of the king weakfish Macrodon atricauda (Günther, 1880) between 1977 and 2009 in southern Brazil
(2011) Cardoso, Luis Gustavo; Haimovici, Manuel
The coastal demersal sciaenid Macrodon atricauda (Günther, 1880), formerly M. ancylodon (Bloch and Schneider, 1801) was sampled for ageing during four periods (1977–1979, 1984–1986, 1997–1998 and (2006–2009) in commercial fishing and scientific surveys along southern Brazil (Lat. 30◦S–34◦40 S). Maximum observed age was seven years, but no fish over five years old was sampled in the last period. Marginal increment analysis of thin sections validated ageing and showed that opaque and translucent bands were laid down at all ages in spring–summer and autumn–winter, respectively. Ageing M. atricauda based on sectioned otoliths is highly recommended because comparisons with readings on whole otoliths showed that ages based on whole otoliths exceeded those based on sectioned otoliths for 56.5% of the aged specimens. The growth of M. atricauda has increased in the last four decades, most noticeably in the case of adult males over two years old and females over three years old. A threefold decrease in its density and the demersal fish community as a whole are the most likely causes of the growth increase.