Reproductive biology of the Brazilian guitarfish,Pseudobatos horkelii (Müller & Henle, 1841) from southeastern Brazil,western South Atlantic

This study provides information on the seasonal occurrence, length‐width relationship, sexual development and size at first maturity of the critically endangered Brazilian guitarfish Pseudobatos horkelii in southeastern Brazil. Samples were obtained from September 2007 to August 2009 from commercial fisheries off São Paulo State coast at depths of 10–50 m, with net mesh sizes of 150 mm in the main net and 100 mm in the cod end. A total of 143 specimens (71 males, 72 females) were analyzed. Total length (TL), disc width (DW), sex and reproductive variables were recorded for each individual. Pseudobatos horkelii presents sexual dimorphism in length‐width relationships, with females attaining larger TL and DW. Females also mature at a larger TL, at 81.1% of the maximum TL, while males mature at 67.8% of the maximum TL. No specimens were captured in winter, and only a small sample size was observed in autumn. Males captured in spring and summer presented semen in the seminal vesicle, indicating that this species may reproduce in the warmer months, as already observed for other Rhinobatidae as well as for P. horkelii in southern Brazil.     

Age and growth of three endemic threatened guitarfishes Pseudobatos horkelii,P. percellens and Zapteryx brevirostris in the western South Atlantic Ocean

The age and growth of three endemic threatened guitarfish species were analysed using vertebrae of Pseudobatos horkelii, P. percellens and Zapteryx brevirostris. Edge and marginal-increment analyses were used to evaluate the periodicity of the formation of the band-pairs, suggesting deposition of one band-pair per year, from late winter to late spring. The von Bertalanffy growth model was used to describe the growth of these species with the following parameters, for pooled sexes: P. horkelii L_∞ = 126.93, k = 0.19 and t₀ = −1.51; P. percellens L_∞ = 109.31, k = 0.16 and t₀ = −1.78; Z. brevirostris L_∞ = 60.37, k = 0.24 and t₀ = −1.42. Our results are essential to understanding the resilience and vulnerability of these species to harvest, which can contribute to management and conservation actions of these species.     

Feeding of the Brazilian sharpnose shark Rhizoprionodon lalandii (Müller & Henle, 1839) from southern Brazil

Stomach contents of 175 Brazilian sharpnose sharks, Rhizoprionodon lalandii, were examined to assess their feeding habits. Caught by artisanal fishers between June 2006 and July of 2007 at Ipanema Beach, on the central coast of the state of Paraná, southern Brazil, R. lalandii appears to be piscivorous (89.7% IRI), feeding mainly on families of Clupeidae (5.1% IRI) and Sciaenidae (3.7% IRI) and secondarily on squid Lolliguncula brevis (8.6% IRI). Diets were similar between sexes and seasons. However, there were ontogenetic changes in their diets. The major items for neonates were Penaeidae crustaceans (%IRI = 56.4) and Engraulidae fishes (%IRI = 29.3); for the juveniles, Sciaenidae (%IRI = 62.5) and Clupeidae (%IRI = 19.7), and for adults Clupeidae (%IRI = 45.8) and Sciaenidae (%IRI = 15.9). Only neonate sharks consumed crustaceans, whereas all size classes consumed cephalopods and teleosts. Neonates had the lowest trophic level (TR = 3.8), with the diet of juveniles and adults the highest (TR = 4.2). Given its abundance and diet, R. lalandii may be an important predator of demersal and pelagic prey in coastal waters of Brazil.     

New insights to discriminate between Sympterygia acuta Garman 1877 and Sympterygia bonapartii Müller & Henle, 1841 (Rajidae) of the Southwest Atlantic Ocean: on the use of geometric morphometrics and spinulation patterns

Geometric‐morphometric and spinulation pattern approaches were employed to assess the discrimination of two species of Sympterygia skates in the Southwest Atlantic: Sympterygia acuta Garman 1877 and Sympterygia bonapartii Müller & Henle, 1841. Two types of variables were employed: linear morphometrics measurements (LMMs), and interlandmark distances (IlDs). The Principal Component Analysis (PCA) and the discriminant analysis (DA) do not overlap between the species. Morphometrically, S. bonapartii is characterized by a wider disc, larger pelvic fins, larger eyes, a greater distance between nostrils and between the first pair of gill slits, a greater interorbital distance between spiracles, and a wider mouth. On the other hand, S. acuta has a larger disc due to the snout size. Regarding the allometric coefficient analysis performed on the IlDs, S. bonapartii showed a positive allometry for the variables that comprise the Box‐Truss 3 (Ventral protocol), which can be related to the mouth width and the first gill slits. This growth type is consistent with those observed in the Box‐Truss 3 (Outline protocol), which is related to the disc width. It has been interpreted that both structures could develop together. In opposition, S. acuta showed isometric growth for the above‐mentioned variables; on the other hand, S. acuta showed positive allometry for all variables that defined the snout in the three protocols, indicating that the snout has a distinctive growth relative to the size through ontogeny. S. bonapartii, however, showed an isometric snout growth. The remaining variables that defined the morphogeometrical protocols displayed the same type of growth. Regarding spinulation, the thorns and dermal denticles proved to be useful to discriminate both species. Thorns of the caudal region were large and oval with smooth edges in S. bonapartii, and oval with lobed edges in S. acuta. Dermal denticles in S. acuta also presented two elongated ridges with a third small ridge between them, whereas those of S. bonapartii presented three elongated ridges of the same size.     

Feeding habits of ocellate spot skate,Okamejei kenojei (Müller & Henle, 1841), in coastal waters of Taean,Korea

The feeding habits of Okamejei kenojei were studied using 592 specimens collected in the coastal waters of Taean, Korea from April 2008 to March 2009. O. kenojei is a bottom‐feeding carnivore that consumes mainly shrimp, fishes, and crabs. Its diet also includes small quantities of amphipods, mysids, cephalopods, euphausiids, copepods, isopods, and polychaetes. The total length (TL) of individuals in this study ranged from 8.2 to 49.0 cm. Cluster analysis based on %IRI (index of relative importance) identified three size classes. Group A (< 20 cm TL) ate primarily caridean shrimp and amphipods; group B (20–30 cm TL) ate exclusively shrimp; and group C (> 30 cm TL) ate penaeoidean shrimp, fishes, and crabs. O. kenojei showed ontogenetic changes in feeding habits. Although shrimps were the primary food consumed by all size groups, the proportion of shrimp in the total diet decreased and the consumption of fishes and crabs gradually increased with the body size of O. kenojei. Size of the prey organisms also increased. Smaller individuals fed mainly on small prey, such as amphipods, mysids, and small shrimp, whereas larger individuals preferred larger prey, such as larger shrimp, fishes, and crabs. The size‐related diet breadth and the percentage of empty stomachs were significant; the diet breadth gradually increased with body size, whereas the percentage of empty stomachs decreased. Seasonal changes in the O. kenojei diet were not significant, but shrimp constituted 97.3% of the summer diet by %IRI. Seasonal changes in diet breadth and the percentage of empty stomachs were not significant.     

Length–weight relationship and condition factor of the Characidae matrinxã, Brycon falcatus (Müller & Troschel, 1844), in the Teles Pires River,southern Amazon

The aim of this study was to verify whether the in situ supply of soybean as a fish attractant bears any influence on the length–weight relationship and condition factor of the omnivorous fish species, Brycon falcatus. In addition, estimated was the length–weight relationship, standard and total length, condition factor, and size of B. falcatus in the spawning period in the Teles Pires River Basin. In the experimental design, rivers of the Teles Pires Basin containing soybean attractant (Verde River, Celeste River, Teles Pires River and the Tapaiuna River) were mapped. Fish were also collected from the Cristalino River, which contained no soybean attractant (treatment control). Samples were collected from August 2012 to July 2013. Length–weight relationship of B. falcatus in the Teles Pires River Basin can be obtained by the expression: Wt = 0.0091*SL^3.376, r² = .97, n = 102, and length‐length relationship: TL = 1.128*SL + 3.978, r² = .96. The condition factor of all specimens collected in the Teles Pires Basin was k = 1.055. Size at capable phase (L50) of spawning was estimated at 23 cm standard length. Results showed no significant difference in the length–weight relationship or condition factor of B. falcatus collected from rivers with or without soybean attractant. Concluded is that the in situ supply of soybean as a fish attractant does not interfere with the wellbeing of B. Falcatus in the Teles Pires River Basin.     

Food habits of the silky shark Carcharhinus falciformis (Müller & Henle, 1839) off the western coast of Baja California Sur,Mexico

The objective of this study was to establish the trophic niche of the silky shark and to determine the ecological role of this predator in the ecosystem close to Baja California. The trophic spectrum was analyzed from samples taken during summer and autumn (2000–2002) from the fishing camps of Punta Lobos and Punta Belcher on the western coast of Baja California Sur. A total of 263 stomach contents were analyzed (143 with food; 120 empty). The index of relative importance (IRI) showed that at Punta Lobos, silky sharks fed mainly on red crabs Pleuroncodes planipes (%IRI = 83%), whereas at Punta Belcher the main food item was the jumbo squid Dosidicus gigas (%IRI = 41%), followed by chub mackerel Scomber japonicus (%IRI = 33%). According to the Levin Index (Bi), the trophic niche breadth in silky sharks is low (Bi = <0.6), which means that silky sharks are specialist predators because they mainly consume three prey types: red crab, chub mackerel, and jumbo squid. The Shannon‐Wiener Index indicated that all trophic categories at Punta Belcher (0.85–1.22) had lower diversity than at Punta Lobos (0.50–1.6), because the silky shark feeds more on tropical prey found close to Punta Lobos. The Morisita‐Horn Index (Cλ) showed an overlap in the diet between the two areas analyzed and between sexes (Cλ = >0.6). The juveniles and adult females did not show any overlap. In the caloric analysis of the main prey, the jumbo squid (D. gigas) contributed the most calories to the silky shark diet (76%).     

Reproductive biology of the skate, Rioraja agassizii (Müller and Henle, 1841), off Puerto Quequén, Argentina

A total of 230 specimens of the skate, Rioraja agassizii, was collected from the commercial bottom trawl fishery of Puerto Quequén, Argentina. During the warmer seasons greater proportions of females were sampled. The largest male and female sampled were 629 and 698 mm total length (TL), respectively. Sexual dimorphism was detected in the relationship between weight ( W )−TL and disc width (DW)−TL, in that females were heavier and wider than males. The smallest mature male and female were 485 and 530 mm TL, respectively. TL at 50% maturity (TL_50%) was estimated at 504 and 570 mm for males and females, respectively. Females exhibited heavier livers than males throughout their lifetimes. Seasonal variations in the gonadosomatic (GSI) and hepatosomatic (HSI) indices, and in the width of the left oviducal gland (OG), along with the greater number of pregnant females sampled during spring, suggested that the peak of the egg laying season could be during this season. The egg cases presented a mean length of 69.01 ± 5.53 mm, mean width of 43.40 ± 1.86 mm and mean weight of 17.00 ± 4.59 g. According to these results specimens from Puerto Quequén and southern Brazil appeared to differ in size, the peak of the egg-laying season and in egg dimensions.     

Length–weight relationship of 37 fish species from the Taquari River (Paranapanema Basin,Brazil)

This work describes the length–weight relationship (LWR) of 37 fish species from the Taquari River, one of the tributaries of the Jurumirim Reservoir in the high Paranapanema Basin, São Paulo, Brazil. Information was not yet available in FishBase on LWRs of 22 of the fish species and maximum weights (Wt) of 24 of the fish species. New maximum standard lengths are presented for nine species as well as weights for two fish species.     

Length‐weight relationship of three cichlid species in a stream in southwestern Amazon,Brazil

The paper investigates the length‐weight relationship of three cichlids species for the southwestern Amazon, Acre state. The individuals were collected at five sites during one year among august/2016 and june/2017 in Quinoá stream (10°06′03.33″S/67°40′11.50″W). The individuals were collected using: seine net, 6 m length, 2.25 high, and mesh size 5 mm, two dip nets, 5 mm mesh, 30 cm width, and 50 cm in length and two sieve with 5 mm mesh, 50 cm width, and 80 cm in length. The results show that one species presented positive allometric growth (Aequidens tetramerus) and the others negative allometric growth (Apistogramma acrensis and Crenicichla semicincta).     

Function of the liver and hepatic lipids of the lesser sand shark, Rhinobatos annulatus (Müller & Henle)

Seasonal variation recorded in the hepatosomatic index for sand sharks, Rhinobatos annulatus, was primarily due to accumulation of hepatic lipids. The contribution of liver lipids to the formation of egg yolk was estimated and found to be secondary to lipid reserves for metabolic functions. Maximum liver lipid content in mature sand sharks coincided with peak breeding activities. Hepatic lipids and their derivatives are an important fuel for muscle and thus needed for migration which occurred soon after parturition and mating. Liver colour was in synchrony with the variation in the total liver lipid content in both sexes of sand sharks.     

Length–weight relationship of 10 freshwater fish species in Amazonian streams,Trombetas River basin (Brazil)

Length–weight relationships (LWR) were analyzed for 10 fish species from 26 Amazonian streams located in four micro‐basins in the Trombetas River basin, Pará State, Brazil. LWRs were calculated based on 1831 individuals sampled between 2010 and 2012 using a manual trawl. The coefficients of proportionality and allometry were within the ranges estimated for most fishes. No previous LWR information was available for these species in the literature.     

Length–weight relationship of three annual fishes (Rivulidae) from temporary freshwater wetlands of southern Brazil

The present study describes length‐weight relationships (LWRs) of three species of the family Rivulidae, Austrolebias nigrofasciatus, Austrolebias wolterstorffi and Cynopoecilus melanotaenia, captured in temporary freshwater wetlands of southern Rio Grande do Sul, Brazil from May to December 2011. The growth pattern for both species was predicted using a linear regression of LWR. Estimates of parameter b ranged from 2.81 in male C. melanotaenia to 3.34 for females A. nigrofasciatus. The present observations are significant for conservation and management because these species are threatened and their habitats are under pressure.     

Length–weight relationships of five fish species from an Atlantic coastal drainage in Brazil

Length–weight relationships (LWR) are presented for five fish species from the Restinga de Maricá, southeastern Brazil. Specimens were caught in pools and streams with different types of fishing gear: seine net, dip net, and sieve. The LWRs of three species are new for this region, and of Phalloptychus januarius are published for the first time.     

Length–weight relationship of seven marine catfishes (Siluriformes: Ariidae) in the Amazon Coastal Zone (Brazil)

Length–weight relationships (LWR) were determined for seven commercially important species of catfishes (Siluriformes, Ariidae) from the Amazon Coastal Zone (ACZ), Brazil. The analyses included 3628 specimens sampled in three trawling expeditions: dry season of 1996 (111 hauls), rainy season of 1997 (120 hauls), and dry season of 1997 (120 hauls). Bottom‐trawl nets were utilized for sampling. Length‐weight estimates for Amphiarius phrygiatus, Amphiarius rugispinis, Aspistor quadriscutis, Notarius grandicassis, Sciades couma, Sciades parkeri and Sciades proops.     

Length–weight relationship of six freshwater fish species in upper‐middle Tocantins River basin (Brazil)

Length–weight relationships (LWRs) were analyzed for six abundant fish species in the upper‐middle Tocantins River, northeastern Brazil. Analyses included data from 486 specimens sampled in five expeditions between August 2013 and May 2015 by gillnets. New maximum values of total lengths for the literature and FishBase were presented for six species, as well as first time estimates of LWR for Galeocharax gulo, Curimata acutirostris and Aphanotorulus emarginatus.     

Length–weight relationships for 35 fish species of the Atlantic Forest,SP/RJ—Brazil

Length–weight relationships (LWRs) for 35 freshwater fish species from the SP/RJ coastal basin in Brazil are presented in this paper. Fishes were captured between 2011 and 2015 on an irregular basis using electrofishing, sieves, trawl nets, cast nets and fish‐traps. In this study new LWRs are reported for 28 species, plus the total weight and length for 34 and nine species, respectively. The study provides new information on less‐studied species and can serve as a basis for management and conservation in this area.