A test of two methods for
marking larvae and postlarvae of the giant freshwater prawn, Macrobrachium
rosenbergii
J.H. Brown, S. McCauley, B. Ross, A. Taylor, F.
Huntingford-2003
Aquaculture
Research, 34(1):
49-55
Abstract:
This paper describes the successful use of two
tagging systems, both produced by Northwest Marine Technology Inc., on
larval and postlarval giant freshwater prawns, Macrobrachium rosenbergii.
Visible implant (VI) elastomer tags (a coloured liquid that solidifies under
the epidermis) were used on stage XI larval prawns (mean weight 0.01 g)
and postlarval prawns (mean weight 0.07 g). VI alphanumeric tags (small
biocompatible plastic labels also inserted under the epidermis) were tested
on postlarval prawns (from a weight of 0.5 g). Tags were inserted using
clove oil as anaesthetic, and survival, mortality and growth rates of tagged
animals were compared with those of controls that were handled but not
anaesthetized or marked. Twenty per cent of the larval prawns (the smallest
of the group) died just after tagging, but thereafter the remaining prawns
survived well, as did all the tagged postlarval prawns. Visibility of the VI
elastomer tags in larval prawns deteriorated with time, though 79% of marks
were still visible to the naked eye 70 days after tagging. VI elastomer
tags in the postlarval group remained clearly visible for up to 100 days.
Visibility of the VI alphanumeric tags fell shortly after tagging, but
remained adequate thereafter. Moult rates in control and tagged animals were
the same in larvae with VI elastomer tags and postlarvae with VI
alphanumeric tags, but the moult rate in the postlarval prawns given
elastomer tags was slower than in controls. Rates of growth were similar in
tagged (elastomer and alphanumeric) and control postlarval prawns, once the
size-dependent mortality of tagged larval prawns was taken into account. We
conclude that VI elastomer tags could be used to mark small numbers of
individual larval and immediately postlarval prawns for periods of several
months, and that VI alphanumeric tags could be used to mark an unlimited
number of individuals from a size of approximately 0.5 g.
(Institute of Aquaculture, University of Stirling,
Stirling, FK9 4LA, UK. E-mail: j.h.brown@stir.ac.uk)