Temporal patterns of fish occurrence of the euryhaline sector of a subtropical estuary, southern Brazil

Fish fauna was studied in five sites of the shallow infralittoral of the Paranaguá Bay during the period from October 1999 to September 2000. At each sampling site, fish were sampled with other trawls, salinity and temperature were measured, water samples were taken from the bottom of the water column for determination of dissolved oxygen, dissolved inorganic nitrogen and phosphate. The spatial and temporal behavior of the environmental variables was analyzed by a Principal Component Analysis; Cluster Analysis was used to gather the sampling sites, and Factorial Correspondence Analysis was applied to the most abundant species. Temperature was themost important variable for the distribution of the months, allowing the division of the study period into hot and cold months. The temporal variation in the fish fauna composition was indicated by cluster analysis, with highest percentages of dissimilarity between the sampling sites during hot months. The variation in dissimilarity between the sites occurred due to differences in the number of individuals and species of the catches. The high frequencies of occurrence of Anisotremus surinamensis, Etropus crossotus, Genidens genidens, Micropogonias furnieri and Sphoeroides greeleyiwere related to high temperatures. The greatest number of fish and species observed in hot months may be related to the life cycle of many species, which reproduce in warmer months, and whose offspring use estuaries as breeding areas.

Length–weight relationships for estuarine fishes in subtropical estuary

The present study describes the length/weight ratio (LWR) of 20 fish species caught in an intertidal area of the Paranaguá Estuarine Complex, southern Brazil. Fish were caught with three beach seine nets, with 2m high, 70m long and distance between knots of 2.5; 4 and 5cm. A total of 880 individuals of 21 species belonging to 11 families were captured, ranging from 5 to 75.5cm in total length. All species analyzed are widely distributed throughout the Southwestern Atlantic. Positive allometric growth (b > 3) was predominant, occurring in 60% species, 35% presented negative allometry (b < 3) and only 5% had isometric growth (b = 3). Many factors could be influencing the distinct growth patterns observed between the literature and the present study, such as the environmental influences, the reduced number of specimens, the sampling methods, the sampling periods and the estimation of the LWR with grouped sexes.

Length–weight relationships for estuarine fishes in subtropical estuary

The present study describes the length/weight ratio (LWR) of 20 fish species caught in an intertidal area of the Paranaguá Estuarine Complex, southern Brazil. Fish were caught with three beach seine nets, with 2m high, 70m long and distance between knots of 2.5; 4 and 5cm. A total of 880 individuals of 21 species belonging to 11 families were captured, ranging from 5 to 75.5cm in total length. All species analyzed are widely distributed throughout the Southwestern Atlantic. Positive allometric growth (b > 3) was predominant, occurring in 60% species, 35% presented negative allometry (b < 3) and only 5% had isometric growth (b = 3). Many factors could be influencing the distinct growth patterns observed between the literature and the present study, such as the environmental influences, the reduced number of specimens, the sampling methods, the sampling periods and the estimation of the LWR with grouped sexes.(AU)

Length–weight relationships comparison between juveniles and adults of fish species from the mangroves of south Brazil

This study reports the length‐weight relationships (LWRs) for 8 fish species that inhabit mangroves. Many fisheries depend on mangroves, which serve as nursery and feeding areas for the juvenile stage of fishes, shrimp, and other fishery resources. In this sense, mangroves provide many ecosystem services, therefore increasing the basic biological knowledge of these ecosystems can help to understand their functioning and create conservation strategies. The majority of LWR studies do not consider juveniles, and it is important to consider these differences as juveniles can grow differently from adults. The fishes were collected from Perequê mangrove, Paraná, Brazil between 2008 and 2010. A variety of fishery gears were employed, including trammel nets, fyke nets, and traps made with plastic bottles combined with four baits. The specimens were measured (weight and length), sexed and evaluated for maturational stage. For the adults, the LWRs were calculated separately by the sex, while juvenile LWRs were estimated together. In general, there were differences in growth type between sexes and life stages. Some species showed differences compared to FishBase estimations, but this could be due to the lengths (and life stage) of the individuals used in the present study compared to FishBase. The discrepancies between adult, juvenile and FishBase estimations showed the importance of considering these aspects in studies using LWR.

Nassarius foveolatus (Gastropoda, Nassariidae), a new record of an exotic species in Brazil

Exotic species are those that occur in an area beyond their natural limit and they are considered invasive when they cause harm to the economy, environment, or human health. In coastal environments, ballast water and inlays on the hull and other parts of vessels are the main ways of introducing invasive aquatic alien species. Nassarius foveolatus (Dunker, 1847) is native from the Central and East Indian Ocean to the East China Sea. The first specimens (empty shells) of N. foveolatus were collected manually on November 11, 2017 on the Rocio footbridge, located in the Paranaguá Estuarine Complex, on the coast of the State of Paraná, southern Brazil. Posteriorly, live specimens were collected in other localities of this bay. It is already possible to infer that the specimens of N. foveolatus occur together with the native specimens of N. vibex (Say, 1822), having the same niche. As previously only N. vibex existed in that place, at least a displacement of this native species has been occurred. However, certainly future ecological studies may confirm this displacement and additional consequences to the local ecosystem, as nassariids can be predators and scavengers. Control procedures should be also greatly implemented.

Nassarius foveolatus (Gastropoda, Nassariidae), a new record of an exotic species in Brazil

Exotic species are those that occur in an area beyond their natural limit and they are considered invasive when they cause harm to the economy, environment, or human health. In coastal environments, ballast water and inlays on the hull and other parts of vessels are the main ways of introducing invasive aquatic alien species. Nassarius foveolatus (Dunker, 1847) is native from the Central and East Indian Ocean to the East China Sea. The first specimens (empty shells) of N. foveolatus were collected manually on November 11, 2017 on the Rocio footbridge, located in the Paranaguá Estuarine Complex, on the coast of the State of Paraná, southern Brazil. Posteriorly, live specimens were collected in other localities of this bay. It is already possible to infer that the specimens of N. foveolatus occur together with the native specimens of N. vibex (Say, 1822), having the same niche. As previously only N. vibex existed in that place, at least a displacement of this native species has been occurred. However, certainly future ecological studies may confirm this displacement and additional consequences to the local ecosystem, as nassariids can be predators and scavengers. Control procedures should be also greatly implemented.(AU)

Owenia caissara sp. n. (Annelida, Oweniidae) from Southern Brazil: addressing an identity crisis

We re-assess the taxonomic status of Owenia Delle Chiaje, 1841 from Southern Brazil based on estuarine specimens from Paranaguá Bay (Paraná) and Babitonga Bay (Santa Catarina), and literature records. Owenia caissara sp. n. is diagnosed by a branchial crown with five pairs of tentacles, branched close to the base of the crown, rectilinear collar with a pronounced lateral slit, two ventrolateral ocelli partially covered by the collar, up to 23 hooks on a single row in the first abdominal segment, regularly curved nuchal shape, regularly moderate teeth curvature, and long and thin scales with oval transition. The description of Owenia caissara sp. n. reinforces the idea that Owenia fusiformis sensu lato is a complex of closely related species that can be distinguished on the basis of both macro- and micro- morphological traits.

Owenia caissara sp. n. (Annelida, Oweniidae) from Southern Brazil: addressing an identity crisis

We re-assess the taxonomic status of Owenia Delle Chiaje, 1841 from Southern Brazil based on estuarine specimens from Paranaguá Bay (Paraná) and Babitonga Bay (Santa Catarina), and literature records. Owenia caissara sp. n. is diagnosed by a branchial crown with five pairs of tentacles, branched close to the base of the crown, rectilinear collar with a pronounced lateral slit, two ventrolateral ocelli partially covered by the collar, up to 23 hooks on a single row in the first abdominal segment, regularly curved nuchal shape, regularly moderate teeth curvature, and long and thin scales with oval transition. The description of Owenia caissara sp. n. reinforces the idea that Owenia fusiformis sensu lato is a complex of closely related species that can be distinguished on the basis of both macro- and micro- morphological traits.(AU)

Short-term stability of estuarine benthic assemblages: are storms pattern-defining events?

Storms, associated with strong winds and heavy rains, are often the most severe physical disturbances in shallow coastal areas causing instability to sedimentary environments. We hypothesized herein that if storms influence short-term assemblage structure of macrofauna, then assemblages should change after storms, while remaining relatively stable over calm weather conditions. The study was conducted at the subtropical Paranaguá Bay, in southern Brazil. We selected four 700 m² sites, at the estuarine outlet, to monitor changes in number of species, number of individuals and Shannon diversity. Sampling was arranged considering the weather forecast so that both before and after conditions could be recorded. Data of each site was tested separately to access the significance of specific (before/after) comparisons using t tests. There were no clear effects of storms on macrofaunal species richness, abundance and diversity at the four sampled sites. Conversely, we showed that short-term variation in abundances occurred regardless of weather conditions. Increased dispersal may be the most common process associated with storms instead of mortality. Storms that intermittently affect the southern coast of Brazil can be thus seen as minor driving forces of shallow-water estuarine macrofauna. Effects of extreme meteorological events remain to be assessed.

Short-term stability of estuarine benthic assemblages: are storms pattern-defining events?

Storms, associated with strong winds and heavy rains, are often the most severe physical disturbances in shallow coastal areas causing instability to sedimentary environments. We hypothesized herein that if storms influence short-term assemblage structure of macrofauna, then assemblages should change after storms, while remaining relatively stable over calm weather conditions. The study was conducted at the subtropical Paranaguá Bay, in southern Brazil. We selected four 700 m² sites, at the estuarine outlet, to monitor changes in number of species, number of individuals and Shannon diversity. Sampling was arranged considering the weather forecast so that both before and after conditions could be recorded. Data of each site was tested separately to access the significance of specific (before/after) comparisons using t tests. There were no clear effects of storms on macrofaunal species richness, abundance and diversity at the four sampled sites. Conversely, we showed that short-term variation in abundances occurred regardless of weather conditions. Increased dispersal may be the most common process associated with storms instead of mortality. Storms that intermittently affect the southern coast of Brazil can be thus seen as minor driving forces of shallow-water estuarine macrofauna. Effects of extreme meteorological events remain to be assessed.

Short-term stability of estuarine benthic assemblages: are storms pattern-defining events?

Storms, associated with strong winds and heavy rains, are often the most severe physical disturbances in shallow coastal areas causing instability to sedimentary environments. We hypothesized herein that if storms influence short-term assemblage structure of macrofauna, then assemblages should change after storms, while remaining relatively stable over calm weather conditions. The study was conducted at the subtropical Paranaguá Bay, in southern Brazil. We selected four 700 m² sites, at the estuarine outlet, to monitor changes in number of species, number of individuals and Shannon diversity. Sampling was arranged considering the weather forecast so that both before and after conditions could be recorded. Data of each site was tested separately to access the significance of specific (before/after) comparisons using t tests. There were no clear effects of storms on macrofaunal species richness, abundance and diversity at the four sampled sites. Conversely, we showed that short-term variation in abundances occurred regardless of weather conditions. Increased dispersal may be the most common process associated with storms instead of mortality. Storms that intermittently affect the southern coast of Brazil can be thus seen as minor driving forces of shallow-water estuarine macrofauna. Effects of extreme meteorological events remain to be assessed.

Description of Sidneioides peregrinus sp. nov. (Tunicata: Ascidiacea: Polyclinidae): a possible exotic species in the Atlantic Ocean

Three species of Sidneioides Kesteven, 1909 were known until now, all of them from the western Pacific. Sidneioides peregrinus is a new species we found in Paranaguá Bay, southern Brazil. Diagnostic characteristics of the species are: colonies with 1-5 lobes, closely clumped, and attached by the entire basal area or by a common smaller area; seven to ten thin longitudinal fiber muscles (some branched) along the anterior two thirds of the thorax; no transverse muscle fibers; more than 30 tentacles of three orders forming one circle; pharynx with 10 to 12 rows of stigmata with 13 to 15 stigmata in each half row; bilobed anus at the level of the fourth or fifth row of stigmata; posterior abdomen not very elongated, oval, and joined to the abdomen by a narrow neck; numerous (> 30) testicular follicles; ovary with about 15 oocytes at about the ninth or tenth row of stigmata in the thorax; large number of embryos incubated in the atrial cavity in the right side of the thorax; larvae oval with a 0.65 mm long trunk, four club-shaped ectodermal ampullae in each side and three, linear and evenly spaced, adhesive papillae with thin stalks, two clusters of ectodermal vesicles, one postero-ventral (around 15 vesicles) and another antero-dorsal (around eight vesicles) between the ampullae and the oral siphon. This paper describes this new species and reports its occurrence in Brazil, where it is most likely introduced. The hypothesis that it is introduced is based on 1) it was never found in previous surveys, 2) in Brazil, it has a restricted and local distribution, 3) its type locality is near a major international port, and 4) the genus, prior to this description, had never been found in the Atlantic Ocean. Considering the great abundance found on the underside of natural boulders, it is imperative that S. peregrinus population growth be studied to evaluate the possibility of rapid distribution expansion.

A new look into the small-scale dispersal of free-living marine nematodes

We tested experimentally the hypothesis that prevailing locomotion/feeding strategies and body morphology may lead to more active dispersal of free-living marine nematodes, besides passive transport. Neutral Red was applied to the sediment inside cores and the red plume formed during the flood tide was divided into near, middle, and distant zones. At 0.5 m and 1 m from the stained cores, sampling nets were suspended 5 and 10 cm above the sediment-water interface. Dispersion behaviors were defined as a function of a) the numbers of stained recaptured nematodes in comparison to their mean densities in the sediment, b) movement in the sediment or swimming in the water column, and c) body morphology. Tidal currents with average velocities of 9 cm/s resuspended the numerically dominant nematode taxa Sabatieria sp., Terschellingia longicaudata de Man, 1907, Metachromadora sp. and Viscosia sp. The recapture of stained nematodes as far as 2 m from the original stained cores showed that, despite their small body size, they can disperse through relatively large distances, either passively or actively, via the water column during a single tidal event. Recapture patterns in the sediment and in the water column indicate that nematode dispersal is directly influenced by their body morphology and swimming ability, and indirectly by their feeding strategies, which ultimately define their position in the sediment column. Besides stressing the role played by passive transport in the water column, our experiment additionally showed that mobility and feeding strategies also need to be considered as determinant of short-scale nematode dispersal.

A new look into the small-scale dispersal of free-living marine nematodes

We tested experimentally the hypothesis that prevailing locomotion/feeding strategies and body morphology may lead to more active dispersal of free-living marine nematodes, besides passive transport. Neutral Red was applied to the sediment inside cores and the red plume formed during the flood tide was divided into near, middle, and distant zones. At 0.5 m and 1 m from the stained cores, sampling nets were suspended 5 and 10 cm above the sediment-water interface. Dispersion behaviors were defined as a function of a) the numbers of stained recaptured nematodes in comparison to their mean densities in the sediment, b) movement in the sediment or swimming in the water column, and c) body morphology. Tidal currents with average velocities of 9 cm/s resuspended the numerically dominant nematode taxa Sabatieria sp., Terschellingia longicaudata de Man, 1907, Metachromadora sp. and Viscosia sp. The recapture of stained nematodes as far as 2 m from the original stained cores showed that, despite their small body size, they can disperse through relatively large distances, either passively or actively, via the water column during a single tidal event. Recapture patterns in the sediment and in the water column indicate that nematode dispersal is directly influenced by their body morphology and swimming ability, and indirectly by their feeding strategies, which ultimately define their position in the sediment column. Besides stressing the role played by passive transport in the water column, our experiment additionally showed that mobility and feeding strategies also need to be considered as determinant of short-scale nematode dispersal.

Description of Sidneioides peregrinus sp. nov. (Tunicata: Ascidiacea: Polyclinidae): a possible exotic species in the Atlantic Ocean

Three species of Sidneioides Kesteven, 1909 were known until now, all of them from the western Pacific. Sidneioides peregrinus is a new species we found in Paranaguá Bay, southern Brazil. Diagnostic characteristics of the species are: colonies with 1-5 lobes, closely clumped, and attached by the entire basal area or by a common smaller area; seven to ten thin longitudinal fiber muscles (some branched) along the anterior two thirds of the thorax; no transverse muscle fibers; more than 30 tentacles of three orders forming one circle; pharynx with 10 to 12 rows of stigmata with 13 to 15 stigmata in each half row; bilobed anus at the level of the fourth or fifth row of stigmata; posterior abdomen not very elongated, oval, and joined to the abdomen by a narrow neck; numerous (> 30) testicular follicles; ovary with about 15 oocytes at about the ninth or tenth row of stigmata in the thorax; large number of embryos incubated in the atrial cavity in the right side of the thorax; larvae oval with a 0.65 mm long trunk, four club-shaped ectodermal ampullae in each side and three, linear and evenly spaced, adhesive papillae with thin stalks, two clusters of ectodermal vesicles, one postero-ventral (around 15 vesicles) and another antero-dorsal (around eight vesicles) between the ampullae and the oral siphon. This paper describes this new species and reports its occurrence in Brazil, where it is most likely introduced. The hypothesis that it is introduced is based on 1) it was never found in previous surveys, 2) in Brazil, it has a restricted and local distribution, 3) its type locality is near a major international port, and 4) the genus, prior to this description, had never been found in the Atlantic Ocean. Considering the great abundance found on the underside of natural boulders, it is imperative that S. peregrinus population growth be studied to evaluate the possibility of rapid distribution expansion.

Description of Sidneioides peregrinus sp. nov. (Tunicata: Ascidiacea: Polyclinidae): a possible exotic species in the Atlantic Ocean

Three species of Sidneioides Kesteven, 1909 were known until now, all of them from the western Pacific. Sidneioides peregrinus is a new species we found in Paranaguá Bay, southern Brazil. Diagnostic characteristics of the species are: colonies with 1-5 lobes, closely clumped, and attached by the entire basal area or by a common smaller area; seven to ten thin longitudinal fiber muscles (some branched) along the anterior two thirds of the thorax; no transverse muscle fibers; more than 30 tentacles of three orders forming one circle; pharynx with 10 to 12 rows of stigmata with 13 to 15 stigmata in each half row; bilobed anus at the level of the fourth or fifth row of stigmata; posterior abdomen not very elongated, oval, and joined to the abdomen by a narrow neck; numerous (> 30) testicular follicles; ovary with about 15 oocytes at about the ninth or tenth row of stigmata in the thorax; large number of embryos incubated in the atrial cavity in the right side of the thorax; larvae oval with a 0.65 mm long trunk, four club-shaped ectodermal ampullae in each side and three, linear and evenly spaced, adhesive papillae with thin stalks, two clusters of ectodermal vesicles, one postero-ventral (around 15 vesicles) and another antero-dorsal (around eight vesicles) between the ampullae and the oral siphon. This paper describes this new species and reports its occurrence in Brazil, where it is most likely introduced. The hypothesis that it is introduced is based on 1) it was never found in previous surveys, 2) in Brazil, it has a restricted and local distribution, 3) its type locality is near a major international port, and 4) the genus, prior to this description, had never been found in the Atlantic Ocean. Considering the great abundance found on the underside of natural boulders, it is imperative that S. peregrinus population growth be studied to evaluate the possibility of rapid distribution expansion.

A new look into the small-scale dispersal of free-living marine nematodes

We tested experimentally the hypothesis that prevailing locomotion/feeding strategies and body morphology may lead to more active dispersal of free-living marine nematodes, besides passive transport. Neutral Red was applied to the sediment inside cores and the red plume formed during the flood tide was divided into near, middle, and distant zones. At 0.5 m and 1 m from the stained cores, sampling nets were suspended 5 and 10 cm above the sediment-water interface. Dispersion behaviors were defined as a function of a) the numbers of stained recaptured nematodes in comparison to their mean densities in the sediment, b) movement in the sediment or swimming in the water column, and c) body morphology. Tidal currents with average velocities of 9 cm/s resuspended the numerically dominant nematode taxa Sabatieria sp., Terschellingia longicaudata de Man, 1907, Metachromadora sp. and Viscosia sp. The recapture of stained nematodes as far as 2 m from the original stained cores showed that, despite their small body size, they can disperse through relatively large distances, either passively or actively, via the water column during a single tidal event. Recapture patterns in the sediment and in the water column indicate that nematode dispersal is directly influenced by their body morphology and swimming ability, and indirectly by their feeding strategies, which ultimately define their position in the sediment column. Besides stressing the role played by passive transport in the water column, our experiment additionally showed that mobility and feeding strategies also need to be considered as determinant of short-scale nematode dispersal.

Reproduction of the flatfish Achirus lineatus (Pleuronectiformes: Achiridae) in Paranaguá Bay, state of Paraná, a subtropical region of Brazil

The present study characterizes the oogenesis and the ovarian maturation scale, and determines the reproductive period, type of spawning, recruitment period, and population variations in the reproductive process of the flatfish Achirus lineatus (Linnaeus, 1758). Specimens were sampled on a monthly basis in the shallow near shore area of the Paranaguá Bay, state of Paraná, Brazil, from March 2006 to February 2007. The specimens collected were measured for morphometric data (total length and total weight) and their gonads were exposed for macroscopic evaluation. The gonads were subsequently removed, weighed and processed for microscopic analyses. Six phases of the ovarian follicle development were defined, as well as five ovarian development stages. Growth patterns differed between the sexes: negative allometry for females and positive allometry for males. Based on the seasonal assessments of the distribution of individual GSI values, the distribution of stages of gonadal development, individual body size, sex ratio, the ratio of juveniles to adults, and histological examination of the ovaries, reproduction was found to occur in the spring (spawning in batches), and recruitment in the autumn. These results show that A. lineatus is an estuarine-resident species that uses the study area for reproduction and recruitment, providing an argument in favor of the need to conserve the estuarine environment in order to preserve stocks.

Reproduction of the flatfish Achirus lineatus (Pleuronectiformes: Achiridae) in Paranaguá Bay, state of Paraná, a subtropical region of Brazil

The present study characterizes the oogenesis and the ovarian maturation scale, and determines the reproductive period, type of spawning, recruitment period, and population variations in the reproductive process of the flatfish Achirus lineatus (Linnaeus, 1758). Specimens were sampled on a monthly basis in the shallow near shore area of the Paranaguá Bay, state of Paraná, Brazil, from March 2006 to February 2007. The specimens collected were measured for morphometric data (total length and total weight) and their gonads were exposed for macroscopic evaluation. The gonads were subsequently removed, weighed and processed for microscopic analyses. Six phases of the ovarian follicle development were defined, as well as five ovarian development stages. Growth patterns differed between the sexes: negative allometry for females and positive allometry for males. Based on the seasonal assessments of the distribution of individual GSI values, the distribution of stages of gonadal development, individual body size, sex ratio, the ratio of juveniles to adults, and histological examination of the ovaries, reproduction was found to occur in the spring (spawning in batches), and recruitment in the autumn. These results show that A. lineatus is an estuarine-resident species that uses the study area for reproduction and recruitment, providing an argument in favor of the need to conserve the estuarine environment in order to preserve stocks.

Reproduction of the flatfish Achirus lineatus (Pleuronectiformes: Achiridae) in Paranaguá Bay, state of Paraná, a subtropical region of Brazil

The present study characterizes the oogenesis and the ovarian maturation scale, and determines the reproductive period, type of spawning, recruitment period, and population variations in the reproductive process of the flatfish Achirus lineatus (Linnaeus, 1758). Specimens were sampled on a monthly basis in the shallow near shore area of the Paranaguá Bay, state of Paraná, Brazil, from March 2006 to February 2007. The specimens collected were measured for morphometric data (total length and total weight) and their gonads were exposed for macroscopic evaluation. The gonads were subsequently removed, weighed and processed for microscopic analyses. Six phases of the ovarian follicle development were defined, as well as five ovarian development stages. Growth patterns differed between the sexes: negative allometry for females and positive allometry for males. Based on the seasonal assessments of the distribution of individual GSI values, the distribution of stages of gonadal development, individual body size, sex ratio, the ratio of juveniles to adults, and histological examination of the ovaries, reproduction was found to occur in the spring (spawning in batches), and recruitment in the autumn. These results show that A. lineatus is an estuarine-resident species that uses the study area for reproduction and recruitment, providing an argument in favor of the need to conserve the estuarine environment in order to preserve stocks.