Life history and production of Capitella capitata (Polychaeta: Capitellidae) in Río de la Plata Estuary (Argentina)

摘要

A benthic survey was carried out from Novemberud1998 to December 1999 in the tidal flats of BahíaudSamborombón (Río de la Plata estuary, Argentina),udin order to study the population structure,udreproductive aspects, growth and secondaryudproduction of Capitella capitata (Fabricius, 1780).udGrowth was analyzed using ELEFAN routine, andudthe secondary production was estimated by Hynesudand Coleman's method (1968). C. capitata did notudpresent periods of very important recruitmentsudthroughout the year; however, the abundance ofudsmallest size classes was higher during summer andudautumn. The summer cohort showed a growth rateud(K) of 2.05 and a seasonal growth oscillation (C) ofud0.6, pointing out that worms grew very slowlyudduring winter months. The life span of this cohortudwas 13 months. The autumn cohort showed a lowerudgrowth rate (K= 1.5) and its growth was lowestudduring winter. The life span was 15 months for thisudcohort. C. capitata in Punta Rasa presented anudextended reproductive period, with absence ofudactivity during winter months. The type of eggs andudlarvae suggest that C. capitata has benthic larvaluddevelopment in the study area, destining its reproductive effort to the production of a low number of eggs, and assuring larvae survival through incubation in brooding tubes. The annual mean biomass in Punta Rasa was 0.117 g m-2 (AFDW), with a mean secondary production of 0.23 g m-2 y-1 and a P/B ratio of 1.96 y-1. The relatively low density, biomass production and P/B ratio of C.udcapitata in Punta Rasa can be considered as reference values for this species inhabiting undisturbed or moderately disturbed areas.