Age determination and growth of the night shark (Carcharhinus signatus) off the northeastern Brazilian coast

Age and growth of the night shark (Carcharhinus signatus) from areas off northeastern Brazil were determined from 317 unstained vertebral sections of 182 males (113–215 cm total length [TL]), 132 females (111.5–234.9 cm) and three individuals of unknown sex (169–242 cm). Although marginal increment (MI) analysis suggests that band formation occurs in the third and fourth trimesters in juveniles, it was inconclusive for adults. Thus, it was assumed that one band is formed annually. Births that occur over a protracted period may be the most important source of bias in MI analysis. An estimated average percent error of 2.4% was found in readings for individuals between two and seventeen years. The von Bertalanffy growth function (VBGF) showed no significant differences between sexes, and the model derived from back-calculated mean length at age best represented growth for the species (L∞=270 cm, K=0.11/yr, t0=–2.71 yr) when compared to the observed mean lengths at age and the Fabens’ method. Length-frequency analysis on 1055 specimens (93–260 cm) was used to verify age determination. Back-calculated size at birth was 66.8 cm and maturity was reached at 180–190 cm (age 8) for males and 200–205 cm (age ten) for females. Age composition, estimated from an age-length key, indicated that juveniles predominate in commercial catches, representing 74.3% of the catch. A growth rate of 25.4 cm/yr was estimated from birth to the first band (i.e. juveniles grow 38% of their birth length during the first year), and a growth rate of 8.55 cm/yr was estimated for eight- to ten-year-old adults.

Spatial variability in water quality and surface sediment diatom assemblages in a complex lake basin,lake of the woods,ontario,canada

Lake of the Woods (LOW) is an international waterbody spanning the Canadian provinces of Ontario and Manitoba, and the U.S. state of Minnesota. In recent years, there has been a perception that water quality has deteriorated in northern regions of the lake, with all increase in the frequency and intensity of toxin-producing cyanobacterial blooms. However, given the lack of long-term data these trends are difficult to verify. As a first step, we examine spatial and seasonal patterns in water quality in this highly complex lake on the Canadian Shield. Further, we examine surface sediment diatom assemblages across multiple sites to determine if they track within-take differences in environmental conditions. Our results show that there are significant spatial patterns in water quality in LOW. Principal Component Analysis divides the lake into three geographic zones based primarily on algal nutrients (i.e., total phosphorus, TP), with the highest concentrations at sites proximal to Rainy River. This variation is closely tracked by sedimentary diatom assemblages, with [TP] explaining 43% of the variation in diatom assemblages across sites. The close correlation between water quality and the surface sediment diatom record indicate that paleoecological models could be used to provide data on the relative importance of natural and anthropogenic sources of nutrients to the lake.

Prevalence of Asthma Symptoms and Associated Factors in Schoolchildren from Brazilian Amazon Islands

Objectives. To determine the prevalence of asthma symptoms among schoolchildren living on two different Brazilian Amazon islands and to identify the risk factors related to this condition. Methods. A cross-sectional study of 400 schoolchildren (5-8 years old) using written questionnaires produced by the International Study of Asthma and Allergies in Childhood, a skin prick test (allergic sensitization), and a stool examination (for helminthic infection). Nonparametric tests were carried out, and the risk factors were identified by logistic regression. Results. the prevalence of active asthma symptoms was markedly higher in children living on Outeiro Island (OI) than those living on Comb Island (CBI) (30.5% and 16.5%, respectively). the logistic regression identified several risk factors of asthma symptoms on CBI: parental history of asthma, night coughing in the past year, and currently have a cat. On OI, the major risk factors were parental history of asthma, personal history of eczema, having two or more older siblings, and night coughing in the past year. the risk factors in common on both the islands were night coughing in the past year and parental history of asthma. Conclusions. the prevalence of asthma symptoms was higher in those with a lifestyle closer to that observed in urban areas (i.e., better sanitation and hygiene), reinforcing the protective effect of a rural environment. Different risk factors were associated with asthma symptoms in schoolchildren living on OI and on CBI. This fact may reflect the environmental individuality and particularities of each island.