Seed production of Great
Atlantic Scallop, Variegated scallop and Queen scallop
Aquaflow Technical Leaflet 2003-113
European Network for the Dissemination of Aquaculture
RTD Information (Q5CA-2000-30105) and previously FAIR-3837, URL: http://www.aquaflow.org/
The principal objective of this project was further
knowledge of the reproduction, settlement, nursery technology, intermediate
growout and final growout in raft culture
for 3 bivalve species Great Atlantic Scallop (Pecten
maximus), Variegated scallop (Chlamys
varia) and Queen scallop (Aequipecten
opercularis). This projects focussed on three areas: 1) The effect of
broodstock conditioning on spawning and egg quality, with spawning yield
assessment in different seasons of the year. 2) Optimisation of the
settlement and maintenance of spat in the nursery and up to sea transfer
size. 3) Development of intermediate grow-out and final grow-out technology.
Viable gametes of Great Atlantic scallop were
successfully obtained between December and June, and the possibility of
broodstock conditioning between December and March is of high interest.
Previous studies showed the existence of two peaks in gonadal size that can
be related to sexual maturation and spawning. One of these events takes
place in winter, and is associated with a relatively high rate of atresia in
(or closing of) the gametes and low larval recruitment in the natural
habitat. It is reasonable to suppose that viable gamete production during
winter depends on external feed sources, as broodstock conditioning was
undertaken at ambient temperature and by supplying high quantities of feed. Despite the difficulties in obtaining variegated scallop
broodstock (due to the scarcity of the species), maturation and gamete
production was obtained while conditioning during winter and part of the
spring. The larvae produced from these spawnings were successfully cultured
up to the settlement stage, thereby showing the promise of this species for
commercial culture. The Queen scallop showed a negative response to spawning
induction methods, failing to react to conditioning and showing no gamete
release.
Improvements in the settling and maintenance of spat
during the nursery phase were achieved with the Great Atlantic scallop, by
using an artificial seaweed system (compared to the traditional method of
bottom-netted cylindrical containers). However, this technique was not found
to be appropriate for the Variegated scallop. Round trays for oyster culture
were used in the nursery phase at sea of the great Atlantic scallop spat and
these produced outstanding results in both growth and survival. Initial spat
lengths of 2.9 mm, showed survival rates of approximately 84% and a final
length of 12.5 mm 40 days after sea transfer. This same technique applied to
the variegated scallop posed problems, which could be due to the animal
density in the tray collectors.
Among the technological results produced by this
project it is important to emphasise the development of a standardised
methodology for the conditioning, stimulation, larval culture and the
settlement for the great Atlantic and Variegated scallops, which showed
considerable improvements to previous protocols. The system developed for
the intermediate grow-out of small-sized great Atlantic scallop spat has
solved a persistent problem in its culture concerning both growth and
survival.
For more information:
Dr. Guillermo Román Cabello
Centro Costero Oceanográfico de La Coruña
Instituto Español de Oceanografia
Muelle de Ánimas
15080 A Coruña - Spain
Tel.: +34 981 205362
Fax: +34 981 22 90 77
Email: guillermo.roman@co.ieo.es