El Nino and La Nina effects
on reproductive cycle of the pearl oyster Pinctada mazatlanica (Hanley,
1856) (Pteriidae) at Isla Espiritu Santo in the Gulf of California
J.A.
Garcia-Cuellar, F. Garcia-Dominguez, D. Lluch-Belda, S.
Hernandez-Vazquez-2004
Journal
of Shellfish Research, 23(1): 113-120 (from ISI Current Contents)
Abstract:
The
impact of El Nino (1997-1998) and La Nina (1998-1999) on the reproductive
cycle of the pearl oyster Pinctada mazatlanica was studied by histologic
observation of gonads. determination of the conditioning index, and oocyte
monthly mean diameter. which are related to sea surface temperature and
availability of food. Available food was determined by comparison between
seasonal and a standard concentration of chlorophyll a. Oyster specimens
were collected from Isla Espiritu Santo in the Gulf of California front May
1997 to November 1999. A direct relationship of spawning to temperature was
observed from July to October. Concentrations of chlorophyll a were related
to the stage of gonad development. The reproductive process was related to
the conditioned index. Reproductive activity during El Nino was longer with
spawning in July to November 1997 and July to October 1998, and more
intensive (in terms of population spawning frequency) than that during the
La Nina event. when the spawning occurred during August to November 1999.
(Inst. Politecn. Nacl., Cicimar, La Paz 23000,
Mexico, e-mail: angelbio@prodigy.net.mx)