Population of the Flathead Grey Mullet (Mugil cephalus, L. 1758) from the Bay of Burgas, Bulgarian Black Sea Coast.

The study is aimed to investigate the dynamics of age distribution, size structure and annual growth rates of Mugil cephalus from the Bay of Burgas. The species inhabits inshore marine waters, as well as estuaries, lagoons and rivers and has high economic importance. Only four age groups were determined for the recent period (2015-2018), compared to the previous period (2010 - 2013) when the flathead grey mullet population has eight age groups. For the period 2010-2013, the size classes ranged from 3.1 cm to 49 cm. For the period 2015-2018, the maximum total length registered was 27 cm. The equation describing the relationship between the length of the body and the radius of the scale is L=0.4177S + 0.376, r²=0.9769. The von Bertalanffy's equation for length growth of the flathead mullet is L_t=139.8[1-e^{-0.04(t+0.07)}], r²=0.9996 and for the weight growth is W_t = 3139[1-e^{-0.1723 (t-0.372)}]30654, r²=0.9328. The equation describing the length-weight relationship of Mugil cephalus is W=0.0122*L^3.0961, r²=0.991. Values of Fulton's condition index for the age groups from 1 to 4 varied between 1.54 and 1.82. Comparison between the results obtained for the periods 2010-2013 and 2015-2018 shows deterioration of the population of the flathead grey mullet in the surveyed area. [ABSTRACT FROM AUTHOR]