Background:The Pharmaceutical companies are very interested in the discovery of new natural bioactive molecules with an impoortant effect and less toxicity, in order to replace old drugs, especially antibiotics which had lost their effectiveness following the spread of multi-resistant bacteria. This study was aimed to investigate, in vitro, some extracts (aqueous extracts, oily extracts and essential oils) of arabic and myrrh gums, plant exudates commonly used in folk medicine for treating several diseases. Materials and Methods: The antimicrobial activity against clinical bacterial and fungal strains was carried out using disk diffusion and broth dilution methods. Cytotoxic activity was mesured using the brine shrimp lethality bioassay determining the LC 50 and genotoxic activity by the preincubation Ames Test using Salmonella strains TA100, TA98 and TA1535 treated with or without the metabolic activation (S9 fraction). Results: An interesting antimicrobial activity was demonstrated, especilly against Gram negative strains. Inhibition zones vary between 16 and 30 mm and MIC's values between 15.62 and 250 μg/ml. All the tested extracts exhibited a bactericidal activity.The arabic gum extracts showed no cytotoxic effect with LC 50 > 100 µg/ml. Myrrh gum extracts showed a significant toxicity to the brine shrimp nauplii with LC 50 < 100 µg/ml. Results of the Ames test indicated that all tested extracts did not possess genotoxic potential. Conclusion: Our study highlighted the antimicrobial potential of gums extracts, making them an excellent drug candidates against resistant pathogens.

Length-weight relationship was estimated for three fish species, including: Lethrinus microdon (Valenciennes, 1,830), Sphyraena jello (Cuvier, 1829) and Euthynnus affinis (Cantor, 1849). Specimens were sampled between May 2014 and June 2015 from the fish caught by the local artisanal fishery and landed in main fishing landing site of Mocka city. Values of b for fish ranged from 2.644 for S. jello to 2.706 for E. affinis and 3.187 for L. microdon. The determination coefficient (r 2 ) between total length and total body weight ranged from .952 in E. affinis to 0.957 in S. jello and 0.960 in L. microdon. K E Y W O R D S allometric, isometric, Mocka, Red Sea

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