Álvaro González

Decapsulated Artemia Cysts: A Suitable Dietary Supplement for Juvenile Tench (Tinca tinca L.)

There are no specifically formulated dry foods for tench (Tinca tinca L.), which forces farmers to use diets formulated for other fish species. This has major drawbacks, such as high mortality, slow growth, and body deformities. A 120 day experiment was performed with five-month-old juvenile tench (initial mean weight: 0.388 g; total length: 31.78 mm) to evaluate decapsulated Artemia cysts as a supplement to a dry diet for other fish species. Three treatments, differing in the daily supplement, were tested: 1,800 freshly hatched nauplii, 1,800 cysts, and 300 cysts per g of tench biomass. Final survival ranged between 95.3% and 97.9%. Juvenile tench that received the supplement of 1,800 decapsulated Artemia cysts had a specific growth rate (1.28), weight (1.83 g), and total length (52.30 mm) significantly higher than those with the same amount of nauplii. The lowest supplement (300 cysts/g of fish biomass) allowed significantly lower growth and higher condition coefficient (1.40) than the rest. Animals with body deformities (1.06%) were only recorded in the groups that received the lowest cyst supplement. Results showed Artemia cysts are a suitable dietary supplement for juvenile tench, being an advantageous alternative to live nauplii.

Effects of Live Artemia Nauplii Supplementation for Different Periods on Survival and Growth of Juvenile Signal Crayfish Pacifastacus leniusculus in the First Six Months of Intensive Culture

Abstract The rearing of astacid crayfishes under controlled conditions requires the addition of live zooplankton to basal dry diets. To investigate the possibility of minimizing the labor and costs involved in providing live feed, a 180-d experiment that focused on reducing the brine shrimp Artemia spp. supply period was carried out with stage 2 signal crayfish Pacifastacus leniusculus. From the onset of exogenous feeding, juvenile crayfish were fed a dry diet (formulated for salmonids) that was supplemented with live Artemia nauplii. Five treatments were implemented, varying the time at which the Artemia supplement was withdrawn (at days 80, 100, 120, or 160, or no withdrawal). No significant differences in survival, growth, or cheliped loss were found among groups throughout the trial. Survival rates at the end of the experiment (180 d) ranged from 62.3% to 66.7%, final carapace length averaged 20.6 mm, and final weight averaged 2.29 g. The results presented here indicate that juvenile astacid crayfishe...