en Biology & physiology Biology & physiology پژوهشي Orginal research papers <div style="text-align: justify;"><span style="font-size:11pt"><span style="line-height:120%"><span style="font-family:Calibri,sans-serif"><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">Knowledge of the reproductive biology of fish is essential for the local fish population management in marine protected areas. The objective of the present study is to determine the sex ratio, reproductive period, and sexual maturity size classes of the blackchin tilapia (<i>Sarotherodon melanotheron</i>) in the marine protected area of Niamone-Kalounayes, located in Casamance, Senegal. A total of 471 individuals including 305 females and 166 males were sampled from June 2021 to July 2022, using an experimental beach seine (250 m long, 25 mm side mesh). The sex ratio (M: F = 1.0: 1.8) was in favor of females. <span style="background:white"><span style="color:black">The size at first sexual maturity (L_m50) </span></span>was obtained 11.00 cm for <span style="background:white"><span style="color:black">males and 11.71 cm for females.</span></span> The</span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""> seasonal variation</span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""> in the </span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">gonadosomatic</span></span></span> <span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">index</span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""> (</span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">GSI</span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">) </span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">indicates that this population has an extended reproduction period,</span></span></span> <span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">ranging from</span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""> March </span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">to </span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">September, with a clear peak </span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">in March, followed by a period of sexual rest (October-December), and a period of maturation of the gonads </span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">from </span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">January through March. R</span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times="">esults of this investigation provided insights for better management practices for this specie.</span></span></span></span></span></span></div> Reproductive biology, Sarotherodon melanotheron, Sex ratio, Maturity, GSI Senegal 1069 1083 http://jifro.ir/browse.php?a_code=A-10-4848-1&slc_lang=en&sid=1 S. Alassane alassanesarr@hotmail.com 100319475328460051193 100319475328460051193 No Cheikh Anta Diop, University of Dakar, University Institute of Fisheries and Aquaculture (UCAD/IUPA), Dakar, Senegal D. Patrick patrickdiedhiou76@yahoo.com 100319475328460051194 100319475328460051194 Yes Cheikh Anta Diop, University of Dakar, University Institute of Fisheries and Aquaculture (UCAD/IUPA), Dakar, Senegal N. Waly lywa01@yahoo.fr 100319475328460051195 100319475328460051195 No Cheikh Anta Diop, University of Dakar, University Institute of Fisheries and Aquaculture (UCAD/IUPA), Dakar, Senegal S. Ousseynou ousseynou0303@gmail.com 100319475328460051196 100319475328460051196 No Cheikh Anta Diop, University of Dakar, University Institute of Fisheries and Aquaculture (UCAD/IUPA), Dakar, Senegal T. Marème maremetall93@gmail.com 100319475328460051197 100319475328460051197 No Cheikh Anta Diop, University of Dakar, University Institute of Fisheries and Aquaculture (UCAD/IUPA), Dakar, Senegal L.B. Alexandre alex.langlaisb@gmail.com 100319475328460051198 100319475328460051198 No Independent biologist, Montreal, Canada