Life history, population dynamics and production of eastern mosquitofish, Gambusia holbrooki (Pisces, Poeciliidae), in rice fields of the Lower Mondego River Valley, West Portugal.
Data
1999
Autores
Cabral, João Alexandre
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Resumo
The introduced population of Gambusia holbrooki from the rice fields of the lower Mondego River Valley, Portugal, was studied
for 15 months, relating their life cycle and population dynamics with its production, in order to assess the role of the species in the energy flow
and secondary production in this type of agro-ecosystem. Two main annual cohorts (1995 and 1996 cohorts) were identified. The females
outnumbered males and the average female/male-ratio was 4. The inspection of ovary developmental stages of this viviparous fish, revealed that
the most important reproductive period was between April and August. The first recruits were recorded in June and were present thereafter until
October. Males from the parental cohort died before August, whereas parental females could survive until October. Mean adjusted fecundity
(number of embryos divided by female standard length) peaked in July 1996 (0.95) and in June 1997 (1.05). Females reached greater sizes, had
a higher growth rate and lived longer than males. Annual production was estimated at 3.101 g×m–2×year–1 (ash-free dry weight, AFDW), the
average biomass at 2.896 g×m–2 (AFDW), and the P/B ratio was 1.071. A conjugation of life history, population dynamics, production and
ecological traits (e.g. fast growth, reduced longevity, viviparity, high productivity, an intermediate position in food chain, and no special habitat
requirements for reproduction) clearly show that the populations of G. holbrooki, introduced into rice fields all over the world, may play an
important role in the structure and functioning of the biological communities of these important agro-ecosystems.
Descrição
Palavras-chave
Mosquitofish , Gambusia holbrooki , Poeciliidae , Growth , Reproduction , Population dynamics , Production
Citação
Cabral J. A. and Marques J. C., 1999