Population dynamics of the mud shrimp Upogebia omissa (Crustacea: Gebiidea: Upogebiidae) from the southwestern Atlantic coast of Brazil

Abstract

The present study provided the first information about the population structure, reproduction, growth and mortality rates of Upogebia omissa Gomes Corrêa, 1968 from the southwestern Atlantic coast. Shrimp were collected monthly between October 2011 and October 2012. A total of 1578 specimens were examined. The overall sex ratio was significantly male-biased. Carapace length ranged from 2.9 mm to 12.91 mm for males and from 4.27 mm to 11.77 mm for females. The von Bertalanffy growth parameters were estimated as: L∞ = 13.90 mm, K = 0.7 yr-1, C = 0.85 for males and L∞ = 12.20 mm, K = 0.8 yr-1, C = 0.85 for females. The slow-growth phase of females occurred in the dry season (November–December) and of males in the rainy season (March). The Growth Performance Index (Φ’) was compatible with those reported for other burrowing shrimps and indicated different growth patterns for males and females. The estimated 3 to 4-year life span is similar to other upogebiids. Natural mortality was estimated at 1.05 yr-1 for males and 1.27 yr-1 for females. Reproduction was continuous. Recruitment occurred mainly in the rainy season. The smallest ovigerous female had a carapace length of 6.33 mm. Fecundity ranged from 450 to 6250 eggs per female and was positively related to individual size. This study contributes to the understanding of life-history strategies of mud shrimps and establishes a baseline for future monitoring programmes and conservation of this species, which is potentially threatened by habitat change and fishing pressure.