Ms. Pascual et Ea. Zampatti, EVIDENCE OF A CHEMICALLY MEDIATED ADULT LARVAL INTERACTION TRIGGERINGSETTLEMENT IN OSTREA-PUELCHANA - APPLICATIONS IN HATCHERY PRODUCTION, Aquaculture, 133(1), 1995, pp. 33-44
A broodstock of flat oysters, Ostrea puelchana, was collected in natur
al grounds from San Matias Gulf (Argentina: 41 degrees 63'S) and trans
ported to France with the purpose of rearing larvae in a hatchery and
growing juveniles in a nursery. The parental stock was conditioned for
maturation, spawning was induced, and larvae were cultured in tanks.
Larval planktonic life lasted from 17 days (23-25 degrees C) to 20 day
s (19-20 degrees C). Settlement rates, estimated on nylon film, ranged
from 50 to 70%; estimates from spat survival on the sieves were 38 to
98%. The rate of settlement increased when water from the tanks conta
ining the parental stock was added to the sieves, confirming the exist
ence in this species of a chemically mediated adult-larval interaction
. This was further investigated on the natural oyster grounds in Argen
tina. The spatial pattern of recruitment on natural substrata, studied
during a settlement season, shows that larvae settle on all the hard
surfaces, but preferentially on the shells of living oysters. The numb
er of recruits settled during the settlement peak was significantly hi
gher on living oysters than on dead oysters. Density of recruits on li
ving oysters decreased as shell surface increased, while no such trend
was apparent in the case of dead oyster shells. This pattern suggests
that the total number of larvae attracted by each oyster is independe
nt of its size. Elucidation of the chemical nature of the attractant w
ould be of interect due to its potential importance in commercial oyst
er hatchery production.