en |
Impact of Thermal stress on the growth, Size-distribution and Biomass of Estuarine Populations of a Benthic Gastropod Pachymelania aurita MÜLLER
UWADIAE, ROLAND EFE
Abstract
This paper reports an in-vivo account of the impact of thermal stress on the biomass and size-distribution
of estuarine populations of Pachymelania aurita in Epe Lagoon, Nigeria. Off all physicochemical variables
investigated only water temperature was statistically different among study stations. A total of 7626 individuals of the
organism comprising 2,371juveniles, 3586 immature adults and 2,034of spawning adults were collected from the study
area. Highest populations of juveniles and immature adults occurred in station 3 where the highest water temperature
occurred while, station 1 recorded lowest populations of the two size classes. Spawning adults occurred in highest
number in station 2 while their lowest population was observed in station 3.Of the total biomass of 2491 g recorded,
juvenile population recorded a total biomass of 143.401 g, immature adults contributed 874.424 g while spawning adults
recorded 1473.19 g. Highest juvenile biomass (34.7 g) occurred in station 5 while, the least (17.7 g), was recorded in
station 1. Station 3 accommodated the highest biomass (233.60 g) of immature adults and the least biomass for this
group was observed in station 1.Biomass of the spawning adults was highest (475.08 g) in station 2 and the lowest
biomass (162.03 g) for this class was observed in station 3. The elevated water temperature observed in station 3
affected the growth of the organism such that only few individuals developed to spawning adult. It is therefore important
that, the regulatory agencies should carry out regular monitoring of cooling water discharge from Egbin Power Station
to ensure compliance with stipulated laws.
Keywords
Thermal stress; gastropods; growth; biomass; size distribution
|