Juvenile population dynamics of Oreochromis mossambicus in an intermittently open estuary at the limit of its natural distribution

<strong><span style="font-size: xx-small; font-family: CharterBT-Bold;"><span style="font-size: xx-small; font-family: CharterBT-Bold;"><span style="font-size: xx-small; font-family: CharterBT-Bold;"><p>Juvenile</p></span></span></span><em><span style="font-size: xx-small; font-family: CharterBT-BoldItalic;"><em><span style="font-size: xx-small; font-family: CharterBT-BoldItalic;">Oreochromis mossambicus  </span></em></span></em><span style="font-size: xx-small; font-family: CharterBT-Bold;"><span style="font-size: xx-small; font-family: CharterBT-Bold;">in the 25 ha, temperate, intermittently open, East Kleinemonde <span style="font-size: xx-small; font-family: CharterBT-Bold;">Estuary in the Eastern Cape, South Africa (33°32</span></span></span><span style="font-size: xx-small; font-family: ZapfCalligraphic801BT-Bold;"><span style="font-size: xx-small; font-family: ZapfCalligraphic801BT-Bold;">’</span></span><span style="font-size: xx-small; font-family: CharterBT-Bold;"><span style="font-size: xx-small; font-family: CharterBT-Bold;">S,<span style="font-size: xx-small; font-family: CharterBT-Bold;">27°03</span></span></span><span style="font-size: xx-small; font-family: ZapfCalligraphic801BT-Bold;"><span style="font-size: xx-small; font-family: ZapfCalligraphic801BT-Bold;">’</span></span><span style="font-size: xx-small; font-family: CharterBT-Bold;"><strong><span style="font-size: xx-small; font-family: CharterBT-Bold;">E), </span></strong></span><strong><span style="font-size: xx-small; font-family: CharterBT-Bold;"><strong><span style="font-size: xx-small; font-family: CharterBT-Bold;">showed a seasonal shift in distribution, occupying all areas of the estuary in summer and, subsequently, being limited to the upper reaches in winter. The young of the year in the littoral zone were <strong><span style="font-size: xx-small; font-family: CharterBT-Bold;"><span style="font-size: xx-small; font-family: CharterBT-Bold;">rapidly depleted and resultant estimates of the <span style="font-size: xx-small; font-family: CharterBT-Bold;">instantaneous rate of total mortality (</span></span></span><em><span style="font-size: xx-small; font-family: CharterBT-BoldItalic;"><em><span style="font-size: xx-small; font-family: CharterBT-BoldItalic;">Z</span></em></span></em><span style="font-size: xx-small; font-family: CharterBT-Bold;"><strong><span style="font-size: xx-small; font-family: CharterBT-Bold;">) ranged from 5.4/yr to 6.9/yr. High annual rates of juvenile mortality and small adult populations imply that stock <strong><span style="font-size: xx-small; font-family: CharterBT-Bold;"><span style="font-size: xx-small; font-family: CharterBT-Bold;">recovery after a reduction in adult population numbers, through activities such as fishing, may be slow. This work adds to the knowledge base of </span></span><em><span style="font-size: xx-small; font-family: CharterBT-BoldItalic;"><em><span style="font-size: xx-small; font-family: CharterBT-BoldItalic;">O. mossambicus </span></em></span></em><span style="font-size: xx-small; font-family: CharterBT-Bold;"><p><strong><span style="font-size: xx-small; font-family: CharterBT-Bold;">ecology and population dynamics in temperate estuaries at the limit of its natural distribution</span></strong></p></span></strong></span></strong></span></strong></span></strong></span></strong></strong>