Babitonga Bay Research Articles

Yams (Dioscorea spp.) in shellmounds and swiddens: ancient history in Babitonga Bay, Santa Catarina State, southern Brazil

BackgroundIn Babitonga Bay, southern Brazil, records of yam consumption exist among shellmound builders from at least 4000 years ago. Shellmounds (sambaquis) are anthropogenic structures in the form of mounds with layers of shells associated with other faunal remains, as well as with charcoal, artefacts and burial. Larger sambaquis are considered to be funerary monuments. The indigenous Jê and Guarani people also lived in the region before the European invasion and cultivated yams. Currently, exotic and domesticated yams are cultivated in the region by farmers. Our aim is to describe the long-term history between the people and Dioscorea in the Babitonga Bay region based on its consumption and occurrence in shellmounds and swiddens.MethodsSurveys of Dioscorea spp. and host were carried out in the vegetation of shellmounds and in the surrounding area using visual detection through intensive searches in transects using the walking method. The survey of Dioscorea species used and cultivated in the precolonial, colonial and current periods was carried out based on the literature. In the present study, only Dioscorea trifida cultivations were recorded.ResultsDioscorea cayennensis, Dioscorea chondrocarpa, Dioscorea dodecaneura, Dioscorea laxiflora, Dioscorea olfersiana, and Dioscorea scabra, all recorded in associated vegetation of shellmounds, in different combinations of the species. In swiddens, D. trifida is most common, followed by Dioscorea alata and, to a lesser extent, Dioscorea bulbifera and D. cayennensis. Records of food use prevail, but they are used as medicinal plants. Yams are integrated on anthropogenic soils of shellmounds and in swiddens in monoculture systems or in intercropping with Zea mays or Colocasia esculenta. The presence of exotic food trees and D. cayennensis in some shellmounds indicates the influence of colonizers on the composition of the vegetation. In sambaquis, there are overlapping processes of construction of cultural niches by different human groups at different times.ConclusionsThe sambaquis and the associated vegetation and swiddens form part of a domesticated landscape. The native species of Dioscorea recorded in shellmounds and surrounding vegetation do not depend on human action to perpetuate themselves in the environment. However, this does not rule out human influence in the past, but it does not indicate horticulture among the Sambaquianos. Greater investment in genetic, archaeobotanical and ethnobotanical research can contribute to a better understanding of the relationship between people and yams over thousands of years.

A 1500-year multi-proxy record of subtropical mangrove dynamics in relation to sea level and climate changes on Babitonga Bay, Southern Brazil

Climatic changes and sea level variations have had a significant impact on the mangroves along the Brazilian coast during the Holocene. The present study focused on understanding the specific factors that have determined the establishment and expansion of mangroves in a subtropical estuary of southern Brazil (Babitonga Bay, State of Santa Catarina-SC), as well as their response to climate change and sea level variations during the late-Holocene. In this study, we carried out sedimentary analysis, palynology, and radiocarbon dating (C-14) to paleoenvironmental reconstruction of the last 1500 cal. year BP. Three facies associations were identified, indicating a progradational succession where a tidal flat was developed at the margin of the estuary. During the first phase, between at least 1440 and ±1286 cal. year BP, the area was characterized by a subtidal environment. The presence of Laguncularia pollen grains since ± 1390 cal. year BP indicated favorable conditions for mangrove establishment in proximity to the study site. Subsequently, around ± 1286 cal. year BP, the tidal flat developed, reaching the present-day shoreline, facilitated by the relative sea level drop. Avicennia trees were established on the tidal flat since ± 1273 cal. year BP, and the establishment of Rhizophora trees occurred in the most recent decades. This mangrove succession developed in Babitonga Bay following a temperature gradient, associated with low-temperature tolerance, and likely its establishment is associated with a temperature increase during the late-Holocene, that caused a migration of the southern limit of the mangrove in the subtropical zone to higher latitudes. Furthermore, the relatively slow expansion of mangroves upstream of Babitonga Bay also may have been controlled by the suitable salinity and substrate conditions, which were favored by the relative sea-level fall during the late-Holocene.

Description of Alitta yarae sp. nov. (Annelida, Nereididae): a new oligo/mesohaline species from southern Brazil

A new species of annelid, Alitta yarae sp. nov., is described from material collected in southern Brazil. This species was collected mostly from fishing buoys but also in muddy substrates of the following estuaries: Paraná Estuary Complex, Guaratuba, and Babitonga Bay. Alitta yarae sp. nov. belongs to a group of species with pennant-shaped posterior dorsal ligules. The most similar species of this group is A. succinea, which shares glandular structures from posterior dorsal ligules on lower edge only and having yellow-amber mandibles. However, the two species differ in the extension of the bare space between areas VI and VII–VIII, which is reduced in A. yarae sp. nov. and wider in A. succinea (respectively shorter than or equal to the palpophore), and the paragnath arrangement. Molecular analysis recovered ~20% genetic distance from the closest species A. succinea and no pattern of segregation among the estuaries studied. Finally, both the morphological and the molecular analyses strongly support the designation of a new species. http://zoobank.org/urn:lsid:zoobank.org:act:2575CF46-57C9-47AE-A4C1-235189F6C107

Mixing Process Evaluation Due to Sea Level Rise in Babitonga bay, Brazil

The Babitonga bay, located in the state of Santa Catarina, Brazil, is an estuarine system of great social and economic importance, that can be highly affected by climate changes effects. These effects include the water level increasing due to Sea Level Rise (SLR) that can be impact the circulation of the bay. In this work, effects in the circulation and mixing processes in the Babitonga bay due to SLR are evaluated. The Water Renewal Rate (WRR) and the Water Age (WA) are used as indicators for the evaluation of the effects. A hydrodynamic model was calibrated and validated for the year 2019, taken as a baseline scenario, and two representative scenarios of SLR due climate change, defined by the Inter-Governmental Panel for Climate Change (IPCC), for the year 2100, were analyzed. WRR and WA were calculated for the Summer and Winter periods for the year 2019, and also for four different projected scenarios for the year 2100. The renovation process is more efficient in the Summer because of the influence of the freshwater discharge. The results showed a reduction in the WRR for the year 2100, and, consequently, an increase in the WA, using the 2019 as the comparison scenario.

Holocene barrier overstepping, estuarine rollover and drainage merging in a sub-tropical bay

A combination of abundant accommodation and high rates of sediment delivery can allow estuarine incised valleys to archive post-glacial coastal evolutionary processes, including the effects of geological controls on valley positioning and stratigraphic evolution. Seismic-stratigraphic and vibracoring investigations in Babitonga Bay, Santa Catarina, Brazil revealed four main stratigraphic units related to the Upper Pleistocene and Holocene Transgressive System Tract (TST) and Highstand System Tract (HST). The interior of Babitonga Bay was subaerially exposed during lower sea levels, forming two distinct incised valleys. The first was established over the Palmital Shear Zone, while the second was formed beneath the modern Main Channel. During the period of Holocene sea-level rise, a coastal lagoon-barrier system was formed and overstepped, leaving remnants on the shallow shelf. Estuarine facies migrated landward until the drainage systems of the adjacent valleys were unified into the single estuarine basin of Babitonga Bay. During late Holocene sea-level fall, the back-barrier lagoon was infilled and prograding barriers and sandy spits developed in estuarine mouths. This study captures the unique geological framework and post-glacial evolutionary history of Babitonga Bay, illustrating the evolution of a stable tectonic valley in response to rising sea level and changing coastal morphodynamics during the subsequent phase of sea-level fall. It broadens our understanding of the response of similar coupled estuary / coastal sedimentary systems environments in response to sea-level change.

Long-Term Perspective on Fishing and Mammal Defaunation in the Atlantic Forest Coast of Brazil Using Archaeological Faunal Remains

Background and research aim: Escalating anthropogenic threats to the Atlantic Forest, a renowned biodiversity hotspot, has placed the region in the spotlight for current conservation efforts. Faunal overexploitation and habitat degradation are among key factors driving the region’s recent declines in faunal populations and biodiversity. Assessing the scale of these impacts is complicated by the near-complete absence of historical reference baselines. Methodology: Here, we provide a contribution to bridge this knowledge gap by analysing faunal remains from two historical archaeological sites, Morro Grande 1 (MG1) and Praia Grande Unidade 21 (PG-U21), in Babitonga Bay (Santa Catarina state, Brazil) dated between 1750 to 1950 AD. Results: Our results revealed that fishing and hunting played a crucial role in household consumption and economic livelihoods during the European colonisation of southern Brazil. Native terrestrial mammals made up a significant proportion of faunal remains at both sites. This suggests that species currently undergoing population declines were exploited in the region for at least the past two centuries. Conclusion: This study provides compelling evidence that the selective hunting of medium- and large-bodied native terrestrial mammals has persisted in the region for over 4500 years, and requires us to reconsider the idea of a heavy reliance on domestic animals during early European colonisation of southern Brazil. Our study thus traces the causes of regional terrestrial mammal defaunation back to the Pre-colonial and Historical times. Implication for conservation: We recommend the integration of historical and archaeological data into modern faunal population assessments and conservation initiatives to set more informed reference baselines.

Aerial photogrammetry techniques using drones to estimate morphometric measurements and body condition in South American small cetaceans

AbstractAerial photogrammetry protocols using drones have proved efficient in monitoring free‐living cetaceans. In this work an aerial photogrammetry protocol using a drone was applied to estimate morphometric measurements and body condition variation in two endangered cetacean species, franciscanas (Pontoporia blainvillei, n = 122) and Guiana dolphin (Sotalia guianensis, n = 41). Sampling occurred in winter and summer in Babitonga Bay, southern Brazil. A 115 cm length object was used to calibrate the scale of measurements at different altitudes. A scale calibration model based on eGSD regression by flight altitude was developed (RMSE = 0.039, r2 = 0.9902, ΔAICc = 0.00) and used to convert measurements from pixels to centimeters. Five morphometric measurements (body length ‐ BL, widths at anterior pectoral fin ‐ AP, axilla ‐ AX, anterior dorsal fin ‐ AD, and posterior dorsal fin ‐ PD) were taken from each animal to infer body condition, in which, the widths in the anterior portions of the body as % BL, can be an auxiliary tool in the evaluation of variation in the body condition of the small cetaceans studied. The aerial photogrammetry protocol allowed for estimating morphometric measurements and monitoring seasonal changes in the body condition of the small cetaceans.

Photo-identification of franciscanas (Pontoporia blainvillei) in Babitonga Bay, Santa Catarina State, Brazil

The franciscana (Pontoporia blainvillei) is a small cetacean endemic to the South Atlantic distributed in coastal waters from Espírito Santo State in Brazil to Chubut Province in Argentina. Babitonga Bay, on the northern coast of Santa Catarina State, Brazil, is home to the only known franciscana population that resides throughout the year in an estuary. Photo-identification is a technique that serves to identify individuals in their natural environment through photographs of natural or artificial body marks. The objective of this paper was to assess the feasibility of identifying individuals from this population from marks present on the dorsal fin and the body. From February 2011 to August 2013, 172 boat surveys were carried out in Babitonga Bay. Groups of franciscanas were recorded on 576 occasions and on 542 of these (94.09%) were photographed. A total of 6,953 (11.89%) from a total of 58,471 photographs were considered of high enough quality to distinguish the features used to identify individuals. Throughout the sampling period, 23 franciscanas were identified. Most of the animals exhibited nicks on the trailing edge of the dorsal fin (82.6%), a mark of longterm duration. Scratches were recorded on only one animal on a single occasion. The rate of resightings ranged from 5.26% to 78.95%, with 39.13% of the individuals showing a rate higher than 50%. A total of 41.8% of the Babitonga Bay population was identified by the presence of marks on the dorsal fin. The study indicates that photo-identification can be applied to franciscanas, which may allow the realisation of various future studies. Because of this species threatened status, the use of this technique may become particularly important for monitoring franciscanas in Babitonga Bay and perhaps in other regions.

Selection of fish resources for consumption and sale by artisanal fishers and implications to fisheries sustainability

Artisanal fishing may be directed at a diversity of target species. Understanding the factors that influencing the choice of fishing resources for sale or consumption helps us comprehend the pattern of use of natural resources and the pressures on the species caught. The commercial value of the species fished influences the fishing effort. Still, other attributes may interfere with the choice of species to be sold or consumed, such as biomass, trophic level, species habitat, and individual preferences. We analyzed the variables that interfere with the choice of fishing resources for consumption or sale (commercial value, trophic level, and habitat) among artisanal fishers in a subtropical estuarine system. We also explored the relationship between the commercial value and the species' trophic level. We conducted 80 interviews with artisanal fishers from five municipalities around Babitonga Bay, located on the southern coast of Brazil, who fish both invertebrates (crustaceans and mollusks) and fish. We found an overlap between the number of species sold (92) and consumed (79). Fishing resources with higher commercial value, and trophic level tend to be sold, while species with low commercial value, and trophic level are the most consumed by fishers. Furthermore, some species used for consumption and sale are classified with different degrees of threat regarding their conservation status as Critically Endangered (CR), Endangered (EN), and Vulnerable (VU), both at local and international assessments. We suggest future directions to support sustainable fisheries management in Babitonga Bay based on these data.

Ecologically driven differences in individual diet specialization across three populations of Guiana dolphin.

Populations usually considered foraging generalists may include specialized individuals that feed on a restricted subset of the prey spectrum consumed by the population. By analyzing the time series of δ13C and δ15N values in sequential growth layer groups within tooth dentin, we measured population- and individual-level variation in resource use of three populations of Guiana dolphins (Sotalia guianensis)-Caravelas River, Babitonga Bay, and Norte Bay-along a latitudinal gradient in the southwestern Atlantic Ocean. We show that the Guiana dolphin at Caravelas River is a generalist population consisting of individual dietary specialists, likely due to the absence of other resident dolphin populations thus allowing individuals to target prey across a wide range of habitats. The Babitonga Bay population is also composed of individual specialists potentially due to the selective foraging behavior of some individuals on high-quality prey sources within and near the bay. In contrast, the Norte Bay population comprises individual generalists, which likely reflects its distinctive cohesive social organization, coexistence with two other dolphin species, and an opportunistic foraging strategy in response to resource fluctuations inherent to the southern limit of the species distribution. Although the Guiana dolphin is generally considered to be a dietary generalist at the population level, our findings reveal that the total niche width of populations and the degree of individual diet specialization are highly context dependent, suggesting dietary plasticity that may be related to a latitudinal gradient in resource availability and environmental conditions.

Critically endangered franciscana dolphins in an estuarine area: fine-scale habitat use and distribution from acoustic monitoring in Babitonga Bay, southern Brazil

Franciscana dolphins in Babitonga Bay represent the only fully estuarine population of this critically endangered species, but this location is also home to a population of Guiana dolphins. Surrounded by large cities and harbors, Babitonga Bay presents intense human activities and potential impacts that may threaten the dolphins. Understanding their habitat use and distribution can inform the implementation of conservation actions and mitigation of such impacts. Here, we used acoustic data from 60 fixed passive acoustic monitoring stations, implemented between June and December 2018. The relationship between the occurrence of franciscanas and environmental variables was investigated with generalized additive mixed models. The selected model presented 51% of explained deviance and included time of day, intensity of presence of Guiana dolphins, maximum slope, and bottom sediment, among other less statistically significant variables. A daily distribution pattern was identified, with franciscanas remaining in the areas of greatest occurrence especially in the morning and seeming to prefer sandy bottom and flatter areas. Areas intensively used by Guiana dolphins were avoided. Additionally, we mapped their distribution using empirical Bayesian kriging to identify the main areas of occurrence and for foraging. Franciscanas are consistently predominant in the innermost region of the estuary, without expressive use of the entrance channel, but with a wider range in winter than in spring. The area around the islands, between the north and south banks, represents an important foraging area, a behavior more frequent during dawn and night. This study provides important insights into critical habitats and behavioral patterns of critically endangered franciscanas in Babitonga Bay.

Ocorrência de intersexualidade em Mugil curema em estuário do litoral norte catarinense, Brasil - relato de caso

ABSTRACT This study describes the occurrence of reproductive changes in a mullet (Mugil curema) from the Babibtonga Bay, Santa Catarina. Gross and microscopic findings indicated changes in the reproductive system that were characterized by the presence of both male and female gonads, nearing sexual maturity, which was compatible with the diagnosis of intersex. It was not possible to identify predisposing factors that may have contributed to the development of this condition. However, as this species of fish may have their reproductive development affected by anthropogenic influence, it is important to permanently monitor this kind of environment. Considering the number of fish belonging to this species that was examined (n=433), the estimated prevalence for intersexuality was 0.23% (confidence interval: 0.00 to 0.68%, with confidence level of 95%). The findings in this study support the diagnosis of intersexuality in M. curema from the Babitonga Bay, which is the first documented case of this condition in this species on the coast of Santa Catarina, Brazil.

The bee community (Hymenoptera, Apidae) of Ilha Grande, Babitonga bay, Santa Catarina State, Brazil: structure, insularity and interaction network

Island biotic communities tend to be less diverse than mainland communities. This work aimed to describe the bee community of Ilha Grande, Babitonga Bay, Santa Catarina, Brazil, and its interactions with floral resources. Entomological net-sweeps were used to collect bees in flight or on flowering plants for 7 hours a day, monthly, for two years. A total of 785 specimens were sampled in the field, belonging to 50 species or morphotypes with four indeterminate individuals. The most representative subfamilies were Apinae (58.59%), Halictinae (40.43%), Colletinae (0.8%) and Megachilinae (0.1%), while the most abundant species were Apis mellifera (305 individuals), Dialictus sp. 1 (182) and Dialictus sp. 2 (32). The presence of Apis mellifera decreased diversity throughout the year. Relative abundance and richness of Halictinae were greater on the island on mainland. Richness of Apinae was lower on the island than that on the mainland due to the absence of Meliponina. A total of 55 botanical species were identified in association with bees, with Schinus terebinthifolius (105 visits) being the most visited. Interaction network metrics indicate an asymmetric, nested, and poorly specialized network. The results corroborate the Theory of Island Biogeography and demonstrate little interference/favoring of some taxa as well as the absence of others.

Mytella strigata and Mytella guyanensis as an object of study: scientific and popular nomenclature review, morphological aspects and occurrence in Babitonga Bay-SC/ Mytella strigata e Mytella guyanensis como objeto de estudo: revisão da nomenclatura científica e popular, aspectos morfológicos e ocorrência na Baia da Babitonga-SC

Bivalve molluscs are an object of great economic interest, in the genus Mytella, it is possible to highlight the species Mytella strigata and Mytella guyanensis. The aim of this study was to carry out a review about the popular and scientific nomenclature of these species, evaluate the main characteristics used to differentiate them, as well as to carry out a quali-quantitative analysis of the mussels from the bay of Babitonga-SC. During the popular nomenclature review it turned out that the mussels M. guyanensis and M. strigata have gone through numerous revisions and nomenclature changes, as well as have several synonymous species. According to the studies reviewed to the popular nomenclature subject, 75% of the publications related to M. guyanensis and M. strigata were made in the Northeast, regarding the popular names “bacucu” and “sururu”, the second term was the most widespread. The analysis of the mussel stocks of Babitonga Bay demonstrated the predominance of M. guyanensis (96%). No significant difference was observed for the sample survey and collection station factors. However, the variations in abundance and diversity were significant for the stratum factor, where the highest values were recorded in the lower mesolittoral, suggesting a tendency for these organisms to be distributed in environments with less air exposure at low tide.

South Brazil pre-colonial sharks: Insights into biodiversity and species distributions.

South Brazil's archaeological coastal sites (shellmounds and middens) show a diverse collection of shark faunal remains, some of which belong to species considered rare nowadays for the region. However, shark archaeological remains identification in this region has been historically insufficient and prone to mistakes. This study identified shark fauna and estimated body size (total length) present at two archaeological sites: Rio do Meio (1220-977 Cal B.P.) and Enseada II (4286-3783 Cal B.P.), located in Santa Catarina, South of Brazil. Here, 1600 teeth and 3588 vertebrae were analysed and identified. We showed higher historical shark species richness than previously reported for South Brazil in historical and archaeological studies. In total, we identified at least 15 species of sharks (11 species and four identifications at the genus level). The presence of juvenile shark remains adds to the evidence of pre-colonial fishing impacts in local shark populations. The consistent recovery of adults and juveniles of Carcharias taurus points to a possible nursery area on the mouth of Babitonga bay. The high teeth frequency (43%) of C. taurus suggests the South Brazil coastline was once home to abundant populations of this critically endangered species. Furthermore, we discuss the presence of rare species nowadays, suggesting a possible historical residency for adult populations of Carcharodon carcharias based on the presence of juveniles and young-of-the-year on archaeological sites. The occurrence of Negaprion brevirostris, a tropical species, might have been facilitated by ocean current variations.

The role of fault reactivation in the geomorphological evolution of coastal landforms on passive continental margins: Evidence from a tectonic estuary in southern Brazil

Coastal areas are unique, fast-changing environments shaped by the action of a wide range of climatic, anthropogenic and geological factors. Tectonic processes (e.g., subsidence, uplift, faulting and tilting) are major controls of landscape evolution and may be responsible for significant changes in river catchments, sea level and erosion rates on coastal zones. In continental passive margins, however, strong tectonic influence is typically attributed to early post-rift evolutionary stages, while changes in climate and/or sediment flux become increasingly dominant in the latest phases. However, there are key exceptions to this rule. We provide new results on an estuarine system formed due to reactivation of major structures crossing the southern edge of Serra do Mar escarpment, where Precambrian terrains, Cretaceous volcanic rocks and Neogene coastal deposits coexist. Morphostructural analysis revealed strong morphometric anomalies near Proterozoic fault zones marked by local subsidence and reactivation of oblique and normal faults, responsible for relevant changes in coastal landscape and tilting of the coastal plain towards the Atlantic Ocean. Despite major Late Holocene progradation along the southern Brazilian coast, local subsidence led to development and preservation of Babitonga Bay, an atypical tectonic estuary formed in the latest stages of passive margin evolution. Our findings imply that the common assumption of recent tectonic stability for intraplate passive margins is false and may lead to misinterpretation of similar coastal systems around the world.

Assessing effectiveness and side effects of likely “seal safe” pinger sounds to ward off endangered franciscana dolphins (Pontoporia blainvillei)

AbstractThe franciscana (Pontoporia blainvillei) is the most endangered dolphin in the western South Atlantic Ocean due to bycatch. Our goal was to test the efficiency of a likely “seal safe” pinger (Banana Pinger, Fishtek Marine Ltd.) to ward off franciscanas, as well as investigating possible side effects of habituation and habitat exclusion. We deployed the pinger within a grid of click detectors (C‐POD, Chelonia Ltd.) in Babitonga Bay, southern Brazil, and the narrow band high frequency sonar click trains were used as a proxy for presence of the franciscanas and response to the pinger. The presence of franciscanas next to the pinger and at 100 m away decreased by 19.4% and 15.4%, respectively, when the pinger was switched on, indicating that the franciscanas avoided the area of the pinger. This avoidance response could not be seen at 400 m away. No habituation effect was noted at any distance. There was a slight gradual decrease in detections over the course of the study at all distances, which is probably related to seasonal variation in the population's habitat use, but this requires attention in future studies. The likely “seal safe” pinger sounds effectively warded off franciscanas and thus has the potential to reduce bycatch.

Macrobenthic community responses to multiple environmental stressors in a subtropical estuary.

We assessed how multi- and univariate models reflect marine environmental health based on macrobenthic community responses to three environmental stressor categories: hydrodynamics, organic enrichment and metal contamination. We then compared the models with the benthic index AMBI (AZTI Marine Biotic Index). Macrobenthic community and physicochemical variables were sampled at 35 sites along Babitonga Bay, a subtropical estuary in Southern Brazil. Distance-based linear modelling identified depth, grain size and organic matter as well as Cu and Zn as key stressors affecting the macrobenthos. Using canonical analysis of principal coordinates (CAP), we developed three multivariate models based on the variability in community composition, creating stress gradients. The metal gradient showed better correlation with the benthic community. Sediment quality indices (Geoaccumulation Index and Contamination Factor) showed a low to moderate contamination status, with higher concentrations for Cr, Ni and Zn at the inner areas of the bay. According to AMBI, Babitonga Bay has a “good” environmental health status, and the AMBI values show stronger correlations with the hydrodynamic and organic enrichment gradients (r = 0.50 and r = 0.47) rather than the metal gradient (r = 0.29). Lumbrineridae polychaetes (not included in the AMBI list) and Scoloplos sp. were negatively related to the metal contamination gradient and were considered sensitive, while Sigambra sp., Magelona papillicornis, the gastropod Heleobia australis and species of the crustacean order Mysida were positively related to the gradient and considered tolerant to higher concentrations of metals in the sediment. Despite the inconsistency in the ecological classification provided by AMBI and its relationship with the metal gradient, our results suggest that the environmental quality was satisfactory for the studied gradients. The metal gradient showed the weakest correlation to AMBI. In such cases, the ecological classification of taxa by the index should be evaluated under the perspective of the action of inorganic genotoxic contaminants represented by metals.

Echolocation variability of franciscana dolphins (Pontoporia blainvillei) between estuarine and open-sea habitats, with insights into foraging patterns.

Environmental and ecological factors can trigger changes in the acoustic repertoire of cetaceans. This study documents the first use of a well-established passive acoustic monitoring device (C-POD) to analyze echolocation sounds and behavior of franciscana dolphins in different habitats: estuary [Babitonga Bay (BB)] and open sea [Itapirubá Beach (IB)]. A total of 10 924 click trains were recorded in BB and 6 093 in IB. An inter-click interval < 10 ms (so called "feeding buzzes") was used as a proxy for foraging activity. The main difference in the acoustic parameters between the two habitats was related to the frequency spectrum, with higher maximum and lower modal and minimum click frequencies in BB, and a train frequency range of 17 kHz, against 10 kHz in IB. Also, the click emission rate (clicks/s) was almost 20% higher in BB. Both studied habitats showed a high proportion of feeding buzzes (BB = 68%; IB = 58%), but with a higher probability of occurrence in BB (p < 0.001) and at night (p < 0.001) in both habitats. The C-PODs showed great potential to monitor occurrence, bioacoustics parameters, and echolocation behavior of franciscana dolphins. Longer-term temporal and spatial monitoring are necessary for elucidating several issues raised in this study.

Assessment of population biology, size‐weight relationship, condition factor, and spatial distribution of the mangrove crab Ucides cordatus (Crustacea: Ocypodidae) in southern Brazil

AbstractBrachyuran crabs are considered one of the most representative groups in mangroves, being recognised as mangrove engineers. However, species that present commercial interest may have their population structure and spatial distribution affected by human activities, such as crab capture. Therefore, monitoring populations over time is essential. We investigated the population biology, size‐weight relationship, condition factor and spatial distribution of Ucides cordatus in a mangrove ecosystem from southern Brazil, providing information for population status assessment. Males and females differed in abundance and frequency, body size, size‐weight relationship and condition factor. Nonetheless, they presented the same spatial distribution pattern. Abundance, sex ratio and body size also revealed a possible influence of anthropised areas in the configuration and distribution of the species. Our results indicate a possible increase in the exploitation of the species, mainly due to the decrease of the largest male size classes’ frequency. Interspecific competition seems to be a possible biotic factor influencing its condition factor. The spatial species distribution highlighted the importance of sites with less anthropogenic influence for the maintenance of the species that can be considered as key areas for the conservation of the U. cordatus in Babitonga Bay.