Growth and survival of the freshwater clam, Galatea paradoxa (Born 1778) cultured on different substrata at the Volta estuary, Ghana

摘要

This study was conducted to assess the optimum clam size and substratum type for the culture of Galatea paradoxa. The experiment was conducted over a 90-day period at the Volta Estuary, Ghana. Three size classes of G. paradoxa categorized as small (27.6 +/- 0.4mm), medium (36.8 +/- 0.4mm) and large (50.0 +/- 0.6mm), were used to ascertain the effect of a sandy and muddy substratum on growth performance and survival. Growth increased from the small-sized clams to the large-sized clams at 2.54, 3.03 and 3.43g, respectively, over the experimental period. Growth was higher (P < 0.05) in the muddy substratum (3.58g) compared with sandy (2.41g). Similarly, the specific growth rate increased from 0.99%day-1 in the small-sized clams to 1.36%day-1 in the large-sized clams. Survival rates were significantly higher (99.4%) for the large-sized clams compared with the medium (78.8%) and the small-size clams (74.1%). There was significant interaction between the size class and the substratum type with a trend towards increasing survival rate from the small to the large size clams in both substrata. The survival rate was lower in the muddy substratum (71.4%) compared with the sandy substratum (96.7%). The yield was significantly higher in the muddy (2.01kg m-290 day-1) compared with sandy substratum (1.87kgm-290day-1). The results of this study indicate that the culture of small-sized clams is best practiced on sandy substratum due to their elevated survival rates, whereas the muddy substratum appears most suitable for the culture of larger clams (>40mm) because of their relatively higher survivorship and better growth performance.