Growth model of the reared sea urchin Paracentrotus ... - SciViews

General introduction
diets rich in proteins (Klinger et al, 1997; Spirlet, 2001). Gonad
enhancement in culture is a necessity in Canada because sea urchins are at
the right stage of maturity during the winter. At this time, the sea is frozen
and the collection of sea urchins under the ice by scuba divers is a painful
and dangerous activity. One solution is to collect animals during autumn,
store them in tanks, and feed them with an adequate diet before marketing
them (Motnikar et al, 1997).
The use of cages in sea ranching operations is also an alternative and
may be used in mono- or polycultures (Keats et al, 1983; Kelly et al,
1998). As for any mariculture activity, degradation of cages by waves and
storms is a major problem, and site location is critical. Suitable sites are
limited, and there is often strong competition for space with other
mariculture activities like salmoniculture or mytiliculture on long lines.
Because of their grazing activity, sea urchins erode the cage nets and are
also a direct cause of depredation which increases maintenance costs
(Kelly et al, 1998).
The ultimate step in the aquaculture production of sea urchin is
independence from natural resources, that is, to control the whole life cycle
in culture, from spawning to gonad enhancement (Le Gall, 1990; Hagen,
1996a). This is the goal we established for the experimental facility in
Normandy. It is called "closed-cycle echiniculture" (Grosjean et al, 1998,
see Part I). Somatic growth of juveniles untill they reach market size is a
process that requires major improvements in current technology and is key
to the successful development of closed-cycle echiniculture. The present
work is devoted to achieving this goal.
Overview of the biology of Paracentrotus lividus
The common European sea urchin, Paracentrotus lividus (Lamarck,
1816) (Echinodermata : Echinoidea : Echinidae) is a marine invertebrate
that lives along European coasts of the North Atlantic (Ireland, Brittany,
Spain) and troughout the Mediterranean Sea. It colonizes two types of
35