Abstract
The present work studied the reproduction of the flatfish Etropus crossotus in the Paranaguá Estuarine Complex, Paraná State, subtropical region of Brazil. Monthly collections of biological material occurred from October 2008 to October 2009, at seven sampling sites, through ten-minute otter trawl surveys in the shallow infralittoral areas of the estuary. Temperature, water salinity, photoperiod, and rainfall data were also recorded. Ovarian histology was used to: 1 - describe ovarian development microscopically, 2 - make the quantitative analyses of both sexes more precise. The maturation curve, the frequency of gonadal maturation states and the condition factor verified that the reproductive period occurred from October to January. The frequency of young and adult individuals established that the recruitment period occurred in January and February. There were no significant differences in the sex ratio during the study period. The studied species completes its entire life cycle in an estuary and its reproduction is well-synchronized with the temporal variations implicit in subtropical regions.
Highlights
Studies of the reproductive process help support the inferences made about the biology of analyzed species and their relation to the environment, making possible the evaluation of stocks, the regulation of the fishery and the implementation of management plans when necessary (Fávaro & Oliveira, 2011).This process is responsible for the viability of fish populations and is synchronized with environmental variations
The data of the former were furnished by Instituto Nacional de Meteorologia (INMET) and the data of the latter were supplied by Instituto Tecnológico – Sistema Meteorológico do Paraná (SIMEPAR)
In the present work, gonadal development was not correlated with water temperature, but with rainfall, salinity, and mainly, photoperiod
Summary
Studies of the reproductive process help support the inferences made about the biology of analyzed species and their relation to the environment, making possible the evaluation of stocks, the regulation of the fishery and the implementation of management plans when necessary (Fávaro & Oliveira, 2011). The species Etropus crossotus Jordan & Gilbert, 1882, object of this study, belongs to the family Paralichthyidae, with the flatfish as the most frequent and abundant of the Paranaguá Estuarine Complex, Paraná, Brazil (Queiroz et al, 2006; Felix et al, 2007), study area of the present work It is a small-sized species (up to 17 cm in total length) that frequently occurs in shallow estuarine areas with a sandy substrate (Figueiredo & Menezes, 2000), feeds on, mainly, crustaceans, polychaetes and small-sized fishes (Lunardon-Branco & Branco, 2003) and is ecologically important in the maintenance of the trophic chain. Etropus crossotus presents wide geographic distribution along the Atlantic, occurring from Chesapeake Bay (USA) to southern Brazil (Rio Grande do Sul) (Figueiredo & Menezes, 2000) This characteristic shows the adaptability of the species to the different climatic conditions imposed by the tropical, subtropical and temperate regions. Water temperature and water salinity data, measured using a mercury thermometer and a refractometer, respectively, were recorded together with rainfall and photoperiod data of the municipality of Paranaguá
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