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.

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 Biopsy darting of common bottlenose dolphins (Tursiops truncatus) in southern Brazil: evaluating effectiveness, short-term responses and wound healing

2017 ◽  
Vol 11 (1-2) ◽  
pp. 121-132 ◽  
Author(s):  
Pedro Friedrich Fruet ◽  
Luciano Dalla Rosa ◽  
Rodrigo C. Genoves ◽  
Victor H. Valiati ◽  
Thales R.O. De Freitas ◽  
...  
Keyword(s):  
Wound Healing ◽  
Tursiops Truncatus ◽  
Local Level ◽  
Bottlenose Dolphins ◽  
Previous Attempt ◽  
Southern Brazil ◽  
Short Term ◽  
Patos Lagoon ◽  
Multiple Biopsy ◽  
Sampling Effectiveness

Cetacean biopsy sampling is a widely used technique with undisputable scientific value. Although it is generally considered as a harmless technique with no apparent long-lasting effects, studies have recommended examining behavioral responses to evaluate potential impacts on individuals, groups and sampled populations. In this study, we evaluated individual behavioral reactions and wound-healing in common bottlenose dolphins (Tursiops truncatus) during a biopsy sampling program carried out in southern Brazil from 2003 to 2012, and compared sampling effectiveness between dedicated and opportunistic sampling surveys. Two hundred and fiftytwo biopsy attempts were made, resulting in 118 hits (48% of attempts) and 134 samples (52% of attempts) collected successfully. Responses to biopsy sampling were low-level, of short-term duration, and elicited similar reactions on the dolphins, irrespective of shot distance, sex of individuals, dolphins’ group size and pre-behavioral state. Dolphins subjected to multiple biopsy attempts reacted in a similar manner as in previous attempt(s), with no evidence of increasing the intensity of the reaction. Wounds could be monitored in 18 animals and healed over 18 to 35 days. Generally, wounds appeared to be covered by epidermis in about three weeks with no observed signs of skin infection. Our results agree with previous studies suggesting that biopsy sampling does not cause significant disturbance to the behavior of dolphins. At a local level, this study demonstrates that biopsy sampling of bottlenose dolphins in the Patos Lagoon Estuary is more effective, less costly and less intrusive when conducted opportunistically, but that long-term sampling is required to achieve a relatively good sample size from photoidentified individuals in the population.

Temporal trends in mortality and effects of by-catch on common bottlenose dolphins, Tursiops truncatus, in southern Brazil

2010 ◽  
Vol 92 (8) ◽  
pp. 1865-1876 ◽  
Author(s):  
Pedro F. Fruet ◽  
Paul G. Kinas ◽  
Kleber G. da Silva ◽  
Juliana C. Di Tullio ◽  
Daniele S. Monteiro ◽  
...  
Keyword(s):  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Temporal Trends ◽  
Patos Lagoon ◽  
Biological Removal ◽  
Patos Lagoon Estuary ◽  
Low Levels ◽  
By Catch ◽  
Juvenile Males ◽  
Related Mortality

The mortality of the bottlenose dolphin, Tursiops truncatus, on the southern portion of Rio Grande do Sul State coast was investigated based on 914 beach surveys conducted between 1969 and 2006. A total of 188 stranded bottlenose dolphins were recorded during this period, indicating a 1.8M:1F sex-ratio of those animals sexed (N = 79). Mortality was low in calves, high in juveniles and sub-adults and slightly lower than in adults. The overall mortality was clearly seasonal overlapping with higher fishing efforts in the Patos Lagoon Estuary and adjacent coastal areas, where most individuals washed ashore. Analysis of a continuous 14-year long subset (1993–2006) of the data indicated relatively low levels of mortality between 1995 and 2000 and a marked increase between 2002 and 2005 followed by an apparent drop in 2006. By-catch was responsible for at least 43% of the recorded mortality between 2002 and 2006. Juvenile males were more susceptible to incidental catches. Among females, by-catch of adults represented 75%. Results of a potential biological removal analysis suggest that current levels of fishing-related mortality are unsustainable for the small resident population of bottlenose dolphins that inhabits the Patos Lagoon Estuary, and that this population may be declining.

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.

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.

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.

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