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The process of cooling and cryopreservation of prawn embryos is a viable alternative for a continuous supply of larvae for freshwater prawn farming ponds. However, studies involving the application of those techniques as well as on toxicity of cryoprotectants in freshwater prawn embryos are scarce. Thus, this study aims to test the toxicity of methylic alcohol (MET), dimethyl sulfoxide (DMSO) and ethylene glycol (EG) on Macrobrachium amazonicum embryos. For the present experiment, pools of embryos were taken from 15 M. amazonicum females and were divided into three groups and tested in duplicate at concentrations of 10, 5, 3; 1, 0.5 or 0.1%. Toxicity tests were conducted for 24 h in Falcon® pipes to obtain the lethal concentration for 50% of the larvae (LC50). After the set period for testing, random samples of embryos were removed for morphological analysis under stereoscopic microscopes. Results were analysed using analysis of variance (ANOVA) and Tukey's test at a 5% significance level and Trimmed Spearman-Karber Analysis to determine LC50-24 h. DMSO toxicity tests revealed that 5% and 10% concentrations showed the highest toxicity and differed from the control (P ≤ 0.05), 24h-LC50 was 437.4 ± 14.4 µL. MET was less toxic among the tested cryoprotectants and concentrations did not allow the determination of its LC50-24h. For tests with EG, concentrations of 3, 5 or 10% solutions resulted in a 100% mortality to tested embryos; EG was the tested cryoprotectant with the highest toxicity, with an LC50-24h average of 81.91 ± 35.3 µl.

Cooling techniques have several applications for reproduction in aquaculture. However, few studies have sought to create protocols for cooling and cryopreservation of Macrobrachium amazonicum embryos. Thus, the objective of this work was to verify the survival of M. amazonicum embryos and the correlation between embryonic volume and mortality of M. amazonicum embryos after cooling. Embryo pools were collected from three females and divided into two treatment groups: dimethyl sulfoxide (DMSO) 3% and ethylene glycol (EG) 0.5%, both of them associated with 2 M sucrose. Positive and negative control groups consisted of seawater 10%. Aliquots of 10 µg of embryos were placed in Falcon® tubes containing a cryoprotectant solution and submitted directly to the test temperature of 2°C for 2 and 6 h of cooling. Further analysis of survival and embryonic volume were performed under a stereoscopic microscope. Data were subjected to analysis of variance (ANOVA), and means were compared using the Tukey test at 5%. The highest embryonic survival rate was observed after the shortest storage time for both the DMSO 3% and the 0.5% EG groups, with survival rates of 84.8 ± 3.9 and 79.7 ± 2.8%, respectively. There was a reduction in survival after 24 h, with the DMSO 3% group presenting a survival rate of 71.7 ± 6.6%, and the EG 0.5% group, 66 ± 6.9%. Survival showed a statistically significant difference when compared with the positive controls after 2 h and 24 h of cooling, with 99 ± 0.5% and 95.8 ± 1.5% survival rates, respectively. There was no significant statistical difference in the embryonic volume, but it was possible to observe a change in the appearance of the embryos, from a translucent coloration to an opaque white or brownish coloration, after 24 h in incubators. Thus, it can be concluded that survival is inversely proportional to storage time and that, although there was no change in the embryonic volume after cooling, a change in the appearance of embryos could be observed.

RESUMOLocalizado a 48 km da cidade de Fortaleza, o distrito de Iguape possui uma pequena praia frequentada por moradores da região, sendo reduto de pescadores que trabalham de forma artesanal e tiram da pesca o seu sustento. Visto a importância que essa atividade econômica tem para a população local, o objetivo desta pesquisa foi caracterizar a pesca artesanal, analisar a biodiversidade da ictiofauna e saber quais aquelas que são de importância econômica para a comunidade. Os resultados mostraram que são utilizadas embarcações do tipo jangadas e paquetes a vela e botes a remo em pescarias de "ir e vir" e de "dormir". As pescarias são realizadas com linha de mão, tarrafas e redes de espera. Foram capturados 2.655 espécimens, inseridos em duas classes, sete ordens, 18 famílias e 32 espécies, revelando uma elevada diversidade e riqueza de espécies, com destaque para Harengula clupeola, Opisthonema oglinum, Haemulon parra e Haemulon plumierii, que contribuem acentuadamente para a renda da comunidade pesqueira.Palavras-chave: atividade econômica, peixe marinho, embarcações. ABSTRACTLocated at 48 km from Fortaleza, the district of Iguape has a small beach frequented by residents of the region, it is a redoubt of artisanal fishermen that have the fishing as the main income. Considering the importance of this economic activity to the local population, the objective of this research was to characterize the artisanal fishery, to analyze the biodiversity of the fish fauna and to know which ones are of economic importance to the community. The fleet is composed by small wooden rafts that are hollow or filled with Styrofoam and driven by sail or paddle. The fishing activities last from some hours to 2 days. The fisheries are carried out with handlines, casting nets and gillnets. A total of 2.655 specimens were caught, belonging to 2 classes, 7 orders, 18 families and 32 species, revealing a high diversity and species richness, mainly from Harengula clupeola, Opisthonema oglinum, Haemulon parra and Haemulon plumieri, contributing significantly to the fishing community income.

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