No abstract

In this study, we aimed to record, for the first time, parasitic infestation by the isopod Probopyrus pandalicola on the prawn Macrobrachium acanthurus, as well as to register some ecological interactions. We hypothesized that the parasitic infection is able to negatively affect the prawn's nutritional condition and that this interaction can modify growth relationships in male individuals. We collected both parasitized (n = 25) and parasite-free (n = 25) individuals in several locations of the Contas River, state of Bahia, Brazil, which had their morphometric characteristics determined, including of the parasites. Relative growth models were constructed for both groups in order to compare slopes and intercepts and determine if the growth patterns are modified by the parasite. We also determined the body condition of the prawns, which was also compared between the two groups. Our results clearly demonstrated that the parasitic infection is able to induce modifications in relative growth patterns in male individuals and that this isopod is capable of reducing the nutritional condition of the prawns. This study indicates that this parasite can induce deleterious effects in the prawn, but individually. Further studies should be conducted to assess the relevance of our findings in conservation and management.

Abstract. Introduction: Crustaceans have economic and ecological importance and the role of caridean crustaceans in lentic environments is crucial to maintain the trophic structure. The species Atya scabra is occasionally associated with fisheries, especially in Northeast and Northern Brazil. Objective: To determine the population structure, reproductive period, patterns of growth and distribution of size classes among sexes in a population of the prawn A. scabra in the De Contas River, Bahia, Brazil. Methods: Individuals were sampled in a period of one year by passing sieves through marginal vegetation and using dragnets. In the laboratory, we recorded the sex of the individuals and measured them using a pachymeter with 0.001 mm precision. The dimensions measured were CL (carapace length), TL (total length) and CW (carapace width). In order to analyze data, linear models for the relationships CL × CW were constructed and the type of allometry for each sex was determined. Individuals were grouped into size classes of 5 mm intervals. A chi-square test (χ2) was used to test deviation from the 1:1 sex ratio. The proportion of ovigerous females was registered for each month to determine the breeding period. Results: A total of 517 individuals were collected, 328 were males and 186 females of which 169 were ovigerous. Males showed a polymodal distribution in size classes and were significantly larger than females, which presented a unimodal distribution in size classes. The observed growth patterns demonstrated that both sexes present negative allometry. However, sexual dimorphism was detected when comparing the growth parameters. Ovigerous females were sampled the entire year and size-frequency data demonstrated that recruitment also occurs throughout the year, which allowed us to classify their reproduction as continuous. Conclusions: Our data is essential to draw sustainable fishery management strategies. We suggest a minimum capture size of 70 mm and capture restrictions from May to August. Key words: ecology; freshwater; limnology; conservation; morphometry.

Here, we present results from a study conducted in two major shrimp fishing grounds in the Northeastern Brazil Marine Ecoregion (NBME) that determined reproductive dynamics of the penaeid shrimps Xiphopenaeus kroyeri and Penaeus schmitti. We aimed to verify if the current closed season is appropriate and untangle the environmental drivers that control their dynamics. The periods of recruitment and reproduction of both species overlap significantly, with a major spawning peak taking place in the dry season and recruitment in the wet season. The recruitment process in both species seem to be indirectly controlled by the onset of the rainfall season, which triggers an increase in primary productivity. This indirect effect also appears to affect growth increments positively. Our results suggest that both species evolved to recruit in the wet and spawn at the dry season as mechanisms to maximize reproductive fitness. They also highlight the possible negative influence of climate change in tropical shrimp stocks and that the current local regulations must be adjusted to better protect them from overfishing. Therefore, we present multiple possibilities to the closed fishing season (CFS) addressed to local decision-makers and reinforce that environmental parameters and effects of environmental changes should be considered when planning management measures.

The aim of this study was to investigate the plastic consumption by the rocky shore crab Pachygrapsus transversus and its effects in the species feeding activity. Specimens were collected monthly from August 2019 to January 2020 in a coral reef located in the north-eastern Brazilian coast, taken to the research laboratory, where they had their stomach removed, degree of fullness determined for each stomach and presence/absence of plastic debris assessed. Frequencies of occurrence of each degree of fullness were compared between sexes and contaminated/non-contaminated individuals. At total, 209 specimens were sampled and high levels of plastic contamination were detected: 47.4% of the sample had plastic fibres in the foregut. All contamination consisted only of nylon filaments, suggesting that irregularly discarded fishing equipment is the source. The frequencies of contaminated individuals among sexes did not differ. However, differences were detected in the comparison between degrees of fullness, demonstrating that there is significant influence of plastic ingestion in the stomachs volume. It is possible that the discrepant frequencies of occurrence of gut fullness were due to false satiation effects and blockage of the digestive tract provided by the fibres.

No abstract

Proper management of shark populations is an immediate concern due to their high vulnerability. In this study, we applied stochastic demographic models for four shark species (bull shark Carcharhinus leucas, tiger shark Galeocerdo cuvier, blue shark Prionace glauca and bonnethead Sphyrna tiburo) to test how population growth behaved under different exploitation scenarios, such as the exclusion of older sharks from fisheries. Populations grew at considerably slow rates when unfished, except for P. glauca. When fisheries targeted all individuals, populations started to decline at generally very low fishing mortality and harvest rates. Conversely, when adult individuals were excluded from fisheries, population resiliency increased despite higher fishing pressures, with no negative growth rates even if harvest levels were doubled.This study indicates that conservation of these species may benefit from protecting adult stocks.

Information on crustacean ovary development is important to properly understand many life story traits. This study aimed to describe macroscopic and microscopic stages of gonad development in females of Plagusia depressa (Fabricius, 1775). Thirty females of P. depressa were captured manually and underwent analgesia by decreasing temperature to collect the gonads, which underwent standard histological techniques. The macroscopic and microscopic appearance of the ovaries and the frequency of germ cells and their location in the organ were used to determine the stage of gonadal development. A total of four stages were defined. Stage 1: marks the end and beginning of gonadal maturation cycle. The germinal zone is tightly reduced with few oogonia and pre‐vitellogenic oocytes are rarely observed. Stage 2: yellow to orange colour and firm consistency. Oogonias and pre‐vitellogenic oocytes can be observed at this stage, as well as a few vitellogenic oocytes at organ limits. Stage 3: colour between red and dark brown. The gonad already presents many mature oocytes. Stage 4: characterized by the abundance of mature oocytes that occupy almost the entire organ. Macroscopic appearance of the female reproductive system, cell characteristics and changes during maturation of P. depressa corroborate with the normally found in Malacostraca.