The population dynamics and reproductive strategy of the polychaete Scolelepis goodbodyi (Jones, 1962), were investigated between June 2009 and May 2010 at Manguinhos beach, southeastern, Brazil. A total of 9,242 individuals were collected. The density did not differ significantly from one month to another. The estimated values of the growth, recruitment, and mortality rates were studied using the width of the third setiger and the growth curves for the populations were adjusted by the Bhattacharya method (L'= 1.23, K = 1.2, mortality = 0.73). Two annual cohorts were identified in the period. Significant differences between males and females were observed in the population (x² = 71.6, p < 0.01) and between sexually defined and sexually indeterminate individuals (x² = 158.4, p < 0.01). Five stages of gonadal development were identified. The coexistence of recruits and mature individuals throughout the study period suggests that this population presented continuous reproduction.

Trawling is known as one of less selective fishing gears and presents high index of accidental captures. The objective of this paper is to characterize the population structure, fecundity and relative growth of Leurocyclus tuberculosus often caught as bycatch in pink shrimp trawl. Sampling occurred between October 2008 and September 2009 in the coast of Rio de Janeiro State, using commercial shrimp trawl. The sample totalized 269 crabs, 168 males and 101 females (42 ovigerous). The sex ratio was 1:1.66 (M:F) and differed statistically from the expected (X²=16.68; p > 0.05). The carapace width (CW) ranged from 12.81 to 71.67 mm (mean ± SD: 48.77 ± 13.75 mm) and from 15.33 to 55.44 mm (36.19 ± 8.66 mm) in males and females, respectively. The size at onset of sexual maturity was estimated at 30 mm (females) and 55 mm (males). The individual fecundity ranged from 3,450 to 23,680 eggs/brood (10,327.3 ± 4,827.7). The analysis of relative growth did not differ from the Brachyura predictions. The histogram analysis showed that shrimp trawl affects the L. tuberculosus population equally, capturing from very young individuals to adults.

A população de Catapaguroides microps A. Milne-Edwards and Bouvier, 1892 da foi analisada com foco na abundância de indivíduos, diferença de tamanho entre machos e fêmeas, razão sexual e distribuição dos indivíduos nas classes de tamanho, ao norte e ao sul da Bacia de Campos. As amostras foram coletadas pelo Programa de Caracterização Ambiental da Bacia de Campos em fevereiro e agosto de 2003. O total de indivíduos analizados foi de 339. A abundância foi maior no norte da Bacia de Campos. Catapaguroides microps mostrou dimorfismo sexual no tamanho do corpo, sendo os machos maiores que as fêmeas. A razão sexual favorece as fêmeas (1:0,7), de forma similar a outros estudos efetuados com populações de águas rasas.

The population of Catapaguroides microps A. Milne-Edwards and Bouvier, 1892 in the Campos Basin was studied with an emphasis on its composition in the Northern and Southern parts of the Basin, the different gender sizes, sex ratio, and size class distribution. Specimens were collected under the "Program for the Environmental Characterization of the deep waters of the Campos Basin" ("Programa de Caracterização Ambiental das Águas Profundas da Bacia de Campos") in February and August 2003. A total of 339 hermit crabs were analyzed. Individual abundance was higher in the North. C. microps shows sexual dimorphism for body size, the males being larger than the females. The sex ratio is skewed in the female's favor (1:0.7), as shown by previous studies on shallow-water populations.

A population of the fiddler crab Uca rapax (Smith, 1870) found in Itaipu Lagoon, southeast Brazil, was sampled monthly from July 2006 to June 2007 in order to study population and reproductive features. The sex ratio of the population was statistically different from the expected (1:1) in almost every month, with a predominance of males. The reproductive cycle and the recruitment of juveniles were continuous, with two peaks. The fecundity ranged from 1.110 to 13.189 eggs (4.984 ± 2.493.8), not differing statistically among seasons. In contrast, the relative fecundity (F') and the reproductive intensity index (RII) were highest in the summer. Female size at the onset of sexual maturity was estimated as 6.1 mm and egg diameter ranged from 0.20 to 0.28 mm. The anthropogenic impact on the environment of Itaipu Lagoon probably had adverse effects on the local U. rapax population, as inferred by its low fecundity rates, early maturation age and biased sex ratio.