Using Condition Index to Assess the Effects of Calcium Substitution by Marine Snail Shells in the Diets of Juvenile Kuruma Shrimps, Marsupenaeus Japonicus

Citation

Moss AS, Koshio S, Ishikawa M, Yokoyama S & Dawood MAO (2018) Using Condition Index to Assess the Effects of Calcium Substitution by Marine Snail Shells in the Diets of Juvenile Kuruma Shrimps, Marsupenaeus Japonicus. Asian-Pacific Aquaculture 2018, Taipei, Taiwan, 23.04.2018-26.04.2018. https://wasblobstorage.blob.core.windows.net/meeting-abstracts/APA2018AbstractBook.pdf

Abstract
Shells derived from marine mollusks represent over 80% of shellfish waste. Therefore, a trial was conducted to assess the efficacy of snail shells (SS) as a calcium replacement in the diets of kuruma shrimps over a period of 42 days. Evaluation of shells’ ability to replace calcium was done by applying principles from previously researched condition criteria index to quantify the external characteristics of juvenile kuruma shrimps (initial body weight, 0.12± 0.01g each) with relation to their growth performance. Five pellet diets were formulated to include increasing levels of snail shells at 0%, 2%, 5%, 10%, and 0% (D1, D2, D3, D4 and D5, respectively). D5 was the negative control with no snail shells and no calcium included in the diet. Each diet was randomly allocated to triplicate groups of 15 shrimps per tank. Survival, body weight gain, specific growth rate, apparent feed efficiency ratio, individual dry weight, total body length, condition index, freshwater stress resistance and fatty acid composition were evaluated. Results indicated that shrimps fed 2% and 10% SS had significantly higher stress resistance (P < 0.05). Generally, dietary SS supplementation improved growth performances (such as final body weight, % weight gain, specific growth rate, apparent feed efficiency ratio), where significantly highest performance was found in shrimps fed 10%SS. Diets with ≤ 2% SS supplementation had significantly lower condition index and hepatosomatic index (D1, D2 and D5). Under the present experimental environment, using the condition index as a tool to evaluate kuruma shrimps’ fitness was beneficial, however it was a poor indication of freshwater stress resistance. Instead, the ratio of n-3/n-6 in the shrimps’ bodies seemed to be correlated with stress resistance. Additionally, supplementing SS in place of Ca is recommended for better growth performance.