Influence of salinity on the size at maturity for fish species reproducing in contrasting West African estuaries

Abstract

International audienceThe influence of salinity on life-history traits was tested using two adjoining West African estuaries: the Gambia with a 'normal' salinity gradient (salinity always <40 and decreasing from the mouth upstream) and the Sine Saloum (Senegal) with an inverse gradient (from 35 at the estuary mouth up to >130 in the upper reaches). The breeding seasons and subsequent fork length (LF) at first maturity (LF50) were estimated for different fish species reproducing both in the Sine Saloum and in the Gambia River estuaries using a database built from experimental fish samplings between 1990 and 2003 with a purse seine (30 locations in the Sine Saloum and 44 in the Gambia). The database contained 30 553 individuals belonging to 60 different species among which only 20 species reproduced in both estuaries. The breeding seasons peaked just before, or at the beginning of the rainy season (June to July), and there were almost no sexually mature fishes at the beginning of the dry season (November to December). Patterns of differences between LF50 of the two estuaries did not follow a general trend (positive or negative), but varied in the same way for females and males of a given species. The LF50 was only systematically reduced with increasing salinity in species living in high-salinity waters (>70). For species living below 70, differences in sizes at first maturity between the two estuaries did not show any clear relationship with salinity. The smallest mature individual found in an environment was a good indicator of the size at first maturity reached in a particular ecosystem because the trend of the species differences between the two ecosystems generally followed that of the differences in size at maturity

Evaluation of zootechnical and reproductive parameters of wild populations of Sarotherodon melanotheron Rppell, 1852 of Southern Benin raised in captivity

“…The optimal temperature range for its reproduction spreads between 17 and 32°C (Philippart and Ruwet, 1982). What is most characterizes this species is its strong euryhalinity (Panfili et al, 2006;Yoboué et al, 2012) that allows to survive at salinities superior than 0.3 mg l -1 (case of Lake Nokoué in Benin) (Chikou et al, 2013) and probably develop a normal gametogenesis and reproduce at high salinities (fry were observed up to 85,10 3 mg l -1 in the wild) (Pauly, 1976).…”

Caractéristiques biologiques et zootechniques des tilapias africains <i>Oreochromis niloticus</i> (Linnaeus, 1758) et <i>Sarotherodon melanotheron</i> Rüppell, 1852 : une revue

“…Elle présente également une forte tolérance à la turbidité et à la pollution de l'eau (Jennings et Williams, 1993). Elle est aussi caractérisée par sa forte euryhalinité (Lemarié et al, 2004;Panfili et al, 2004;Panfili et al, 2006;Ouattara et al, 2009) qui lui permet de survivre à des salinités supérieures à 0,3 mg/l (Chikou et al, 2013). Sa gamme de tolérance à la salinité va de 0 à 110 g/l (Gilles, 2005).…”

Using oocyte essential fatty acid composition to assess spawner reproductive potential under hypersaline conditions

“…In the estuary's middle reaches, water temperatures regularly exceed 30°C and salinity surpasses 50 by the end of the dry season in June/July (Simier et al 2004). E. fimbriata exhibits significantly higher batch fecundity when spawning in these hypersaline conditions compared to marine water or freshwater (Scheffers et al 1972, Albaret & Gerlotto 1976, Panfili et al 2006.…”

“…In the Sine Saloum estuary, this batch-spawning species exhibits a protracted reproductive period that usually lasts from January to August (Albaret & Gerlotto 1976, Panfili et al 2004. Its physiology, which is adapted to eurysaline conditions allows the species to cope with varying salinities from around 0 to 97 (Panfili et al 2006) and even to reproduce in waters with salinities up to 66 (Charles-Dominique & Albaret 2003). E. fimbriata is considered a passive filter feeder and undergoes an ontogenetic diet shift, with copepods representing the main prey item for larvae and phytoplankton for adults (Facade & Olaniyan 1972, Blay & Eyeson 1982a, Lazzaro 1987.…”