Reference

Sellars, M. J., S. J. Arnold, P. J. Crocos, G. J. Coman. 2004. Physical changes in brown tiger shrimp (Penaeus esculentus) condition when reared at high-densities and their capacity for recovery. Aquaculture 232:395–405.

Abstract

Juvenile brown tiger shrimp, Penaeus esculentus, have been observed to sustain external damage to their appendages and exoskeleton when reared at high densities above 2000 shrimp m^-3 for the purpose of restocking into natural populations. This damage principally includes missing appendage segments, broken rostrums and necrotic lesions on the external body surface. Such damage could reduce post-release survival when the juveniles are stocked into wild populations. This study examined both the physical condition of juveniles reared to approximately 1.0 g in a high-density production system and their post-production recovery.

Physical condition, measured as the level of damage sustained to a shrimps appendages and exoskeleton, was compared among four treatment groups relative to a control. Two of the treatments were reared at a single density (2860 shrimp m^-3) on two different physical substrate types (A and B), and the other two treatments were reared on a single physical substrate (C) but at two different stocking densities, 5720 shrimp and 11,430 shrimp m^-3. Juvenile P. esculentus reared in sandy-bottom tanks at 75 shrimp m^-3 were maintained as a control. Shrimp in the treatment groups were reared until they reached an average weight of 1 g. The rate of recovery of damage sustained during high-density rearing was determined for all density treatments and the control, when released into sandy-bottom tanks at 100 shrimp m^-3 over a period of 22 days.

Shrimp reared at all treatment densities (2860, 5720 and 11,430 m^-3) became significantly more damaged over time ( P<0.05), whereas shrimp reared in sandy-bottom tanks at 75 m^-3sustained no damage over time. The difference in the mean level of damage between the 5720 and 11,430 m^-3 treatments was not significant ( P>0.05). Similarly, physical substrate type (A and B) had no significant effect on the level of damage sustained by shrimp stocked at 2860 m^-3 ( P>0.05). These results indicate that shrimp become damaged when reared at densities of 2860 m^-3or greater under these production conditions, and that damage increases over time.

The physical signs of appendage recovery of juvenile P. esculentus reared under high-density conditions were studied by tagging and releasing shrimp from each of the stocking densities (2860, 5720 and 11,430 m^-3) and the low-density (75 m^-3) sandy-bottom tank control treatment, into sandy bottom tanks at 100 shrimp m^-3. Damage decreased significantly (P<0.05) over time and more than 65% of damaged units were recovered within 7 days of release. There were no significant differences ( P>0.05) between the rates of appendage recovery by shrimp reared at different densities. These results indicate that appendage recovery for shrimp reared in the three high-density treatments was rapid. Despite shrimp sustaining damage during the production phase, high-density rearing is still a suitable method of high throughput seedstock production, provided that shrimp can survive the 7-day recovery period once released.

Tag

Visible Implant Elastomer (VIE)

Objective