Age, growth, population dynamics and stock status of Perna perna in Omani waters

Abstract

Aim: Population parameters such as growth, recruitment pattern, mortality, exploitation rate and the length-weight relationship were investigated for the brown mussel, Perna pernain Omani waters. Methodology: Monthly shell-length frequency of P. perna were collected from three different locations, namely, Mirbat, Ra's Al-Had and Ra's Madrakah for one year from December 2010 to November 2011. The data were analysed using the FiSAT (FAO-ICLARM Stock Assessment Tools) software to estimate population parameters. Results: The length of individuals ranged from 10.34 to 104.03 mm and the weight from 0.12 to 52.45 g. The estimated relative growth coefficient (b) was 3.079(±0.019), and the 95% confidence levelof branged from 3.045 to 3.116. The annual recruitment pattern of P. perna showed a continuous trend throughout the year. The peak recruitment at Mirbat (19%) and Ra'sAl Had (21%) was observed in June, whereas at Ra's Madrakah (24%)it was observedinJuly. The estimated total mortality values ofP. pernawere 2.84 yr-1, 3.28 yr-1 and 2.48 yr-1 at Mirbat, Ra's Al Had and Ra's Madrakah, respectively, while the natural mortality rates were 1.25 yr-1 at Mirbat, 1.29 yr-1 at Ra'sAl Had, and 1.23 yr-1 at Ra's Madrakah. The fishing mortality rates were 1.59 yr-1 at Mirbat, 1.99 yr-1 at Ra'sAlHad and 1.25 yr-1 at Ra's Madrakah. The Perna perna attained an approximate length of 53.5 mm at the end of one year. Exploitation rate (E) was 0.56, 0.60 and 0.50 at Mirbat, Ra'sAlHad and Ra's Madrakah, respectively. Interpretation : The results revealed that the stock of P. perna at Mirbat and Ra's Al Had areas was over exploited. However, currentlyatRa's Madrakah the stock ofP. pernais currently optimally exploited.