Broodstock Conditioning of the Yellow Clam (Amarilladesma mactroides)

Broodstock conditioning involves maintaining adult animals in optimal environmental conditions to ensure that the largest number of breeders reach maturity. We evaluated the gonadal development and the occurrence of spawns in the yellow clam (Amarilladesma mactroides) and estimated the duration of conditioning that results in the highest maturity rate. Clams were kept buried in a 10 cm sand bed within Ø = 15 cm containers. A concentrate of Isochrysis galbana and Chaetoceros muelleri was supplied daily. Four conditioning periods (14, 28, 45 and 60 days) with four replicates were used. On the day of collection and at the end of each conditioning period, clams were induced to spawn with thermal shocks (16.7 °C to 26 °C) and sperm. The first spawns were observed on day 28, but only 50% of the males and 33% of the females were mature, and their mean oocyte diameter (36.33 µm) was smaller than the minimum (45–50 µm) considered for ready-to-spawn clams. However, on day 45, all males and females were mature (mean oocyte diameter = 45.14 µm) and 1102 × 103 eggs were released. To ensure a high maturity rate, yellow clams should be conditioned in captivity for 45 days. Monitoring gonadal development in the wild to collect clams at advanced stages of gonadal development may be a less expensive strategy worth considering.