Tagging of Litopenaeus vannamei(Boone) by uropod cutting: a comparison of two methods

Abstract

Two uropod-cutting methods were used and compared as a means of long-term tagging on juvenile (mean weight: 1.77±0.5 g) and sub-adult (mean weight: 18.7±0.2 g) Litopenaeus vannamei: (a) cutting half of the left exopod (LE); and (b) cutting the whole right uropods (WR). Shrimp with uncut uropods served as controls. Regeneration of uropods in juvenile shrimp commenced within a week and complete regeneration was evident after 2 weeks. In sub-adult shrimps, incomplete regeneration (IG) was observed within 1 month of culture in both cutting methods. Complete regeneration was observed in 2 months among shrimps in LE but not in WR. Abnormal growths (AGs) on regenerated uropods (91.1%) were observed in juvenile shrimp including hollow-type (HT; 77.8%) and flat-type (FT; 13.3%). Among sub-adult shrimp, 87.6% produced AG including HT (68.8%) and FT (18.8%). In WR, regenerated uropods among juvenile shrimp were of a normal type (N) which was indistinguishable from the control treatment. On the other hand, normal growth (with less pigmentation, 5.2%), IG (26.3%), and AG (68.5%) were observed among sub-adult shrimp. After 4 months of culture, with average final weights of 18–19 g, tag retention rate in juvenile shrimps was 91.1% for LE treatment, and 87.6% (LE) and 100% (WR) in sub-adults. Survival rate was about 98% for both cutting methods in juvenile and 53–63% for sub-adult.