By-catch analysis of Argentinean prawn Artemesia longinaris (Decapoda: Penaeidae) in surrounding area of Patos Lagoon, southern Brazil: effects of different rainfall

2011 ◽  
Vol 91 (5) ◽  
pp. 1059-1072 ◽  
Author(s):  
L.F.C. Dumont ◽  
F. D'Incao
Keyword(s):  
Juvenile Fish ◽  
Marine Species ◽  
Southern Brazil ◽  
Target Species ◽  
Surrounding Area ◽  
Patos Lagoon ◽  
Low Salinity ◽  
Top Predators ◽  
Incidental Catch ◽  
By Catch

One of the most problematic fishing methods in terms of by-catch and discarding is prawn-trawling. This paper analyses the incidental catch of an artisanal trawl fleet during two discrete Artemesia longinaris fishery seasons (2002 and 2004). The fishery season of A. longinaris operates monthly and it takes place in the surrounding area of the Barra do Rio Grande. Sampling was carried out during the fishing season (April–December) always on the same artisanal trawl boat. An observer was included on-board to avoid loss of information due to discards made by the fishermen at sea. Fifty species were caught: 38 fish and 12 crustaceans. Discrete fauna abundance and composition were recorded in analysed years, with higher by-catch ratios associated with elevated rainfall and low salinity. The overall discard ratio was 1:5.6, with values ranging from 1:11.3 in 2002 to 1:2.5 in 2004. The most striking differences between both years analysed were observed during autumn (1:75 in 2002 and 1:11.30 in 2004) and winter (1:16 in 2002 and 1:0.97 in 2004), while spring presented similar values (1:8 in 2002 and 1:4 in 2004). The discard ratio estimated in terms of number showed a different pattern, presenting overall values of 1:2.24 in 2002 and 1:0.5 in 2004. Higher estuarine runoff may have increased biomass production in the surrounding area of Patos Lagoon during 2002, sustaining higher abundance of estuarine-related and marine species in the area, as well as higher mean trophic level and abundance of top-predators. Conversely, A. longinaris production was consistently lower, since this marine species does not tolerate marked reductions in salinity. In 2004, salinity was higher, associated with low rainfall and favouring A. longinaris abundance in the area. During this dry year, the target-species was dominant in samples resulting in very low by-catch ratios, especially in winter (1:0.97). The catch was mainly composed of juvenile fish, since fishery is performed in nursery grounds.

scholarly journals Diet and feeding strategy of the dusky grouper Mycteroperca marginata (Actinopterygii: Epinephelidae) in a man-made rocky habitat in southern Brazil

2011 ◽  
Vol 9 (1) ◽  
pp. 161-168 ◽  
Author(s):  
Mario V. Condini ◽  
Elisa Seyboth ◽  
João P. Vieira ◽  
Alexandre M. Garcia
Keyword(s):  
Feeding Strategy ◽  
Marine Species ◽  
Southern Brazil ◽  
Patos Lagoon ◽  
Additional Tool ◽  
Rocky Habitat ◽  
Dusky Grouper ◽  
Dietary Shifts ◽  
Rocky Habitats ◽  
Rocky Bottoms

The dusky grouper (Mycteroperca marginata) is a marine species usually associated with rocky bottoms and reefs. The present work investigated the diet and feeding strategy of a dusky grouper population inhabiting a 4.5 km long pair of rocky jetties located in the mouth of Patos Lagoon estuary. No prior research has been conducted in such man-made habitat and the current study provides a basis for comparative studies on the diet of the dusky grouper populations inhabiting natural vs. man-made rocky habitats. Similarly with previous studies on natural substrates, crabs and fishes were the main food categories consumed (%IRI = 85.1 and %IRI = 12.6, respectively), whereas shrimps and mollusks had lower importance in the diet (%IRI = 1.9 and 0.4, respectively). As previously reported for dusky grouper populations inhabiting reefs and rocky bottoms, the present work revealed conspicuous size related dietary shifts. Blue crabs and fishes become increasingly important food items in the diet of larger individuals (> 500 mm, TL). Finally, it was found that the studied dusky population has a generalist feeding strategy with a high between-individual variation in prey consumption. Such strategy remained similar across the size increment of the species. Our findings suggest that man-made rocky substrates provide suitable feeding grounds for the dusky grouper in southern Brazil and could be used as an additional tool in the conservation efforts of this endangered species.

scholarly journals Dynamics and Viability of a Small, Estuarine-Resident Population of Lahille’s Bottlenose Dolphins From Southern Brazil

2021 ◽  
Vol 7 ◽  
Author(s):  
Pedro F. Fruet ◽  
Luciana M. Möller ◽  
Eduardo R. Secchi
Keyword(s):  
Coastal Waters ◽  
Bottlenose Dolphins ◽  
Population Viability Analysis ◽  
Disease Outbreaks ◽  
High Survival ◽  
Southern Brazil ◽  
Patos Lagoon ◽  
Dolphin Population ◽  
Protection Area ◽  
By Catch

Identifying threatened populations and quantifying their vulnerability is crucial for establishing priorities for conservation and providing robust information for decision-making. Lahille’s bottlenose dolphins have been long subjected to by-catch mortality in gillnet fisheries in coastal waters of southern Brazil, particularly in the Patos Lagoon estuary (PLE) and adjacent coastal waters, where dolphins from three populations (or Management Units) show overlapping home ranges. In this study we used a stage-classified matrix population model to conduct a demographic analysis of the PLE’s population with life-history data estimated through an 8 years mark-recapture study. A population viability analysis (PVA) was used to run a series of simulations where the risk was assessed under different by-catch scenarios, taking into account the effects of parameter uncertainty and stochasticity in the projections. In the absence of by-catch, we estimated that this dolphin population would growth at a rate of about 3% annually (95% CI: 1.2–5.8%). Under current by-catch rates, prognoses indicated high probabilities of viability over the next 60 years. These optimistic prognoses appear to be associated with the high survival of adult females. However, the eventual removal of very few mature females (one every year or two) would result in a prominent likelihood of decline from its current abundance at all pre-specified levels. The viability of the population would be substantially improved if the survival of juveniles/sub-adults could be increased. This may be achieved through the recently implemented dolphin protection area, which prohibits gillnet fisheries in the core area of this population. If the protection area reduces the entanglement rates of the most impacted life-stages (i.e., juvenile/sub-adult dolphins), there would be a substantial chance of the PLE’s dolphin population increasing above 20% of its current size, which is here proposed as conservation goal. If met, this goal has the potential to promote habitat quality, increase genetic diversity and connectivity with adjacent populations, enhancing the ability of bottlenose dolphins in southern Brazil to cope with environmental change and potential disease outbreaks.

scholarly journals Temporal Variability of Suspended-Solids Concentration in the Estuarine Channel of Patos Lagoon, Southern Brazil

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 646
Author(s):  
Rafael André Ávila ◽  
Priscila Mulattieri Suarez Orozco ◽  
Mauro Michelena Andrade ◽  
Osmar Olinto Möller
Keyword(s):  
Temporal Variability ◽  
Suspended Solids ◽  
Southern Brazil ◽  
Patos Lagoon ◽  
Reliable Technique ◽  
Acoustic Data ◽  
Solids Concentration ◽  
Estuarine Hydrodynamics ◽  
Inflow Conditions

The assessment of suspended-solids dynamics is crucial for the effective monitoring of estuarine environments. As the recurring in-situ sampling is usually problematic, the calibration of the backscattering from acoustic Doppler profilers has shown to be a reliable technique to estimate the suspended-solids concentration (SSC) in estuaries and rivers. In this study, we obtained a linear model that provides SSC estimates for the estuarine channel of Patos Lagoon by calibrating turbidity and acoustic data with in-situ concentration samples. The model output was analyzed in terms of its relationship with estuarine hydrodynamics and temporal variability. In this estuary, the supply of suspended solids is known to be due the runoff from its main tributaries, but also through the exchanges between the estuary and the coastal ocean. Both sources provide sediments and organic solids which affect water quality, geomorphology, and harbor operations. Results show that SSC is strongly linked to estuarine hydrodynamics, where concentrations increase with streamflow. During outflow periods, higher concentrations are associated with river runoff, whereas with inflow conditions they are induced by southern and southwesterly winds. However, relationship between SSC and streamflow is asymmetrical, meaning that the largest concentrations are majorly linked to outflow currents and downstream transport.

Fish and invertebrate by-catch in the crab pot fishery in the Isle of Man, Irish Sea

2017 ◽  
Vol 98 (8) ◽  
pp. 2099-2111
Author(s):  
Fikret Öndes ◽  
Michel J. Kaiser ◽  
Lee G. Murray
Keyword(s):  
Irish Sea ◽  
Target Species ◽  
Catch Per Unit Effort ◽  
Isle Of Man ◽  
Ecosystem Effects ◽  
By Catch ◽  
Catch Rates ◽  
Taxonomic Groups ◽  
Catch Composition ◽  
Autumn And Winter

Baited trap or pot fisheries are considered to have relatively few wider ecosystem effects on the marine environment, particularly when compared with towed mobile fishing gear. However, this assumption is rarely tested in the field. This study aimed to determine the composition of non-target species that occur in crustacean pots and to assess spatial and temporal differences in catches in the waters around the Isle of Man, Irish Sea. The data were collected using fishery independent surveys and a questionnaire study. Based on fishery independent surveys, a total of five taxonomic groups and 43 species occurred as by-catch. The dominant by-catch species was velvet crab Necora puber. The by-catch per unit effort (BPUE) for all of the non-target species was low particularly in comparison to towed bottom gear fisheries around the Isle of Man. BPUE of species composition varied considerably between different locations around the Isle of Man. The results of both the fishery independent and questionnaire data suggested that the by-catch rates varied with season with peak BPUE occurring in spring which then declined into autumn and winter. By-catch composition did not decrease significantly with an increasing target species catch. Overall, by-catch was low relative to target species catch which may be partially attributable to the use of escape panels in pot fisheries in the Isle of Man.

scholarly journals Habitat use patterns of franciscana dolphins (Pontoporia blainvillei) off southern Brazil in relation to water depth

2009 ◽  
Vol 89 (5) ◽  
pp. 943-949 ◽  
Author(s):  
Daniel Danilewicz ◽  
Eduardo R. Secchi ◽  
Paulo H. Ott ◽  
Ignacio B. Moreno ◽  
Manuela Bassoi ◽  
...  
Keyword(s):  
Habitat Use ◽  
Rio Grande ◽  
Limiting Factors ◽  
Small Scale ◽  
Southern Brazil ◽  
Rio Grande Do Sul ◽  
Use Patterns ◽  
Management Procedures ◽  
By Catch ◽  
Pontoporia Blainvillei

The patterns of habitat use by the franciscana dolphins (Pontoporia blainvillei) along its distribution are poorly known. This study investigates the patterns of habitat use with respect to depth for 181 individuals of different age, size, gender and reproductive condition off Rio Grande do Sul, southern Brazil. The results reveal that franciscanas are very homogeneously distributed according to depth. Individuals from all lengths utilize nearly the entire range of depths of the surveyed area. Larger or older animals do not use deeper waters than younger animals, indicating that body size and age are not limiting factors for franciscanas that occupy deeper or offshore waters. Gestation seems to not cause a change in the distribution of females. Although the sex-ratio of the overall data did not vary from 1:1 in different depth intervals, a small-scale comparison between the northern and southern coast demonstrated the existence of some kind of sexual segregation. Franciscana by-catch in Rio Grande do Sul is not sustainable and it is agreed that management procedures are needed. Nevertheless, the available data on species distribution do not allow the designing of a protected area in order to minimize the by-catches of a particular sex/reproductive class.

Archaeological Earthen Mound Complex in Patos Lagoon, Southern Brazil: Chronological Model and Freshwater Influence

Radiocarbon ◽  
2017 ◽  
Vol 59 (1) ◽  
pp. 195-214 ◽  
Author(s):  
Rafael G Milheira ◽  
Kita D Macario ◽  
Ingrid S Chanca ◽  
Eduardo Q Alves
Keyword(s):  
Archaeological Sites ◽  
Human Intervention ◽  
Southern Brazil ◽  
Patos Lagoon ◽  
Lagoon System ◽  
Indigenous Groups ◽  
Freshwater Influence ◽  
Intense Activity

AbstractIn the present work, we assess the chronology of archaeological sites known as earthen mounds, commonly found at the Pampas biome, among the lowlands of Brazil, Uruguay, and Argentina. We focused on the Pontal da Barra settlement, which is a testimony of the long-term occupation of indigenous groups in the swamp and wet environment of Patos Lagoon, southern Brazil. A Bayesian chronological model based on the radiocarbon (14C) dating of 17 samples of fish otolith, 5 charcoal fragments, and 2 bones (human and dog) allowed determination of the beginning of the occupation as well as the occupational synchronism of the different mounds. The nature of the samples allows us to study the local 14C reservoir effect through the comparison between the group of marine and terrestrial samples, deriving a reservoir offset value of 63±53 14C yr for this particular area, indicating a strong freshwater influence in the lagoon system. We estimate the start of human intervention in the landscapes of southern Patos Lagoon to be around 2200 cal BP, with the most intense activity between 1800 and 1200 cal BP.

scholarly journals A numerical study of the Plata River plume along the southeastern South American continental shelf

2005 ◽  
Vol 53 (3-4) ◽  
pp. 129-146 ◽  
Author(s):  
Felipe M. Pimenta ◽  
Edmo José Dias Campos ◽  
Jerry L. Miller ◽  
Alberto R. Piola
Keyword(s):  
South America ◽  
River Discharge ◽  
Numerical Study ◽  
South American ◽  
Southern Brazil ◽  
Large Area ◽  
Plume Dynamics ◽  
Low Salinity ◽  
River Outflow ◽  
Low Latitudes

The Rio de la Plata, one of the largest rivers on Earth, discharges into the ocean waters from basin that covers a large area of South America. Its plume extends along northern Argentina, Uruguay, and southern Brazil shelves strongly influencing the ecosystems. In spite of this, little is known about the mechanisms that control it. Here we report results of simulations with POM carried out to investigate the roles of wind and river discharge in Plata plume dynamics. Different outflows were explored, including an average climatological value and magnitudes representative of La Niña and El Niño. Forcing the model with river discharge the average plume speed was directly related to the outflow intensity. The Plata northward extension varied from 850 to 1550 km and for average discharge a band of low salinity waters formed from the estuary up to 30ºN of South Brazilian Shelf. Upwelling and downwelling winds were applied after 130 days. The distribution of low salinity waters over the shelf was more sensitive to the wind direction than to the river outflow variability. Downwelling winds were very capable of advecting the low salinity signal downshelf. Upwelling winds were efficient in eroding the plume, which was basically detached from the coast by Ekman drift. Abnormal plume intrusions toward low latitudes may be a result of the original plume position coupled with events of persistent strong downwelling favorable winds.

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