OCCURRENCE, SIZE COMPOSITION AND GROWTH PATTERN OF TWO CARIDEAN SPECIESFROM THREE INTERCONNECTING LAGOONS IN SOUTH-WEST, NIGERIA

Abstract

The occurrence, size composition and growth pattern ofprawns, Macrobrachium macrobrachion (Herklots, 1851) and Macrobrachium vollenhovenii (Herklots, 1857) from Badagry, Lagos and Epe Lagoons were investigated for 24 months (June 2013 May 2015). The major ecological difference in the lagoons was salinity, with Badagry and Epe Lagoons being low brackish and Lagos Lagoon to be high brackish despite their interconnections. The size ranges of M. macrobrachion were 4.8 11.8cm; 4.9 11.9cm and 5.1 -12.8cm, while the size ranges for M. vollenhovenii were 5.4 15.9cm; 4.5 16.6cm and 4.3 22.6cm for Badagry, Lagos and Epe Lagoons respectively. M. macrobrachion had the highest occurrence from the three lagoons, occurring more in both Badagry (90.73%) and Lagos (84.20%) Lagoons while M. vollenhovenii occurred more in Epe Lagoon (55.28%). The prawns exhibited a positive allometric (b>3) and negative allometric (b<3) growth. The b (regression coefficient) values of M. macrobrachion ranged from 2.76 3.24 while that of M. vollenhovenii ranged from 2.81 - 3.68 for the three lagoons. There was a strong positive correlation between total length and weight in both species, which showed that an increase in length results in increase in weight of the organism. The coefficient of determination (R²) values for the combined sexes ofM. macrobrachion ranged from 0.9043 0.9377 and 0.8867 0.9712for Macrobrachium vollenhovenii. The implication of the estimated length-weight relationship (LWR) parameters of Macrobrachium species from the three lagoons confirmed that increase in length was proportional to increase in weight. The varied environmental factors (salinity) in the three lagoons could be said to have influence on the occurrence, size composition and growth of the species.Despite the variations in the salinity levels from the three interconnecting lagoons, the environment was still able to accommodate various sizes of the prawn species, thus making the lagoons suitable for existence of the species.