The autochthonous caramote prawn, Penaeus kerathurus, is highly exploited and widely studied throughout its distribution range in the Mediterranean. However, in Algeria, very few studies have been conducted on its biological aspects. In this research article, we provided for the first time a detailed analysis of the key parameters: length-weight relationships (LWRs) and condition factor (K) of prawns harvested from the unique coastal lagoon in the country, El Mellah Lake. Thus, the morphometric relationships between the total and carapace lengths against body weight were established for 1066 males, 608 females, and grouped individuals, revealing a negative allometric   growth in all cases. Similarly, all K-obtained average values were less than the unit, indicating the poor nutritional status of prawns. Overall, the present findings showed that both parameters were sex-dependent and more likely reflect the population response to species growth and reproductive traits, biotic (new predator-prey relationship), and abiotic (lagoon's meso-oligotrophic status) stimuli. The present study will be useful for better enhancing our understanding about P. kerathurus in southwestern Mediterranean and lagoon habitats.