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Vol. 52, 2013
Abundance, recruitment, and shell growth of the exotic mussel
Limnoperna fortunei in the Río de la Plata (Argentina)
Fernando
Spaccesi
Laboratorio
de Bentos, Instituto de Limnología Dr. Raúl A Ringuelet (ILPLA)-CCT
CONICET-UNLP, Boulevard 120 y 62, CC 712, La Plata, Buenos Aires CP
1900, Argentina
Abstract
Background: Since its accidental
introduction in 1991, - Limnoperna
fortunei has spread
throughout the del Plata basin becoming established as a new
non-indigenous freshwater bivalve in South America.
Results: .I compared its population dynamics
between two - sites in the Río de la Plata Estuary at Bagliardi Beach
(freshwater) and Punta Indio Beach (saltwater-influenced) 90 km to the
south, by monthly sampling of mussel
conglomerates on hard substrate - during low tides for 1 year and
observed significant variability over space and time. Punta Indio
exhibited lower abundances of recruits (<1 mm) and post-recruits
along with a larger adult size
than those at Bagliardi Beach. The extent of air exposure appeared to
be a major constraint regulating mussel densities in these areas. The
high recruitment at Bagliardi Beach indicated continuous reproduction
that was
positively correlated with temperature changes. Recruits survived in
low water temperatures (10.7°C). The species' abundance had stabilized
by several years after the invasion. In contrast, at Punta Indio,
settlement availability
depended on critical environmental conditions. The multivariate
analysis- identified a combination of physicochemical variables, of
temperature, dissolved solids, and oxygen saturation, that best
explained the golden
mussel's abundance. Possible north-to-south larval dispersal may have
influenced recruitment patterns. The von Bertalanffy growth model
suggested that populations consisted of three principal cohorts at both
Bagliardi Beach
and Punta Indio: Lt
= 18 to 20 mm (first-year growth) and Linf
= 30 mm. Mussels of Punta Indio showed faster growth rates (k) than those at Bagliardi Beach,
probably because of wave exposure and low population densities.
Conclusions: This work provides
specific information that complements our present knowledge of the
ecology of this invasive mollusk. Further studies will be essential to
gain an understanding of the population dynamics and the way in which
the golden mussel reacts to stressful conditions.
Key words: Biological invasion; Brackish
water; Hard substrate; Population dynamics; South America.
*Correspondence: E-mail: pachamo@yahoo.com
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