Estimation of horse mackerel (Trachurus mediterraneus Steindachner, 1868) stock in the Eastern Black Sea by acoustic method

Horse mackerel (Trachurus mediterraneus, Steindachner, 1868) is one of the most commercially important pelagic species in the Black Sea in Turkey. Although, the variety of catching amount of the species fluctuate by years, it is obvious that the stocks are getting smaller. For this reason, in order to observe the alterations in horse mackerel fish stocks over the years, the a survey was conducted to estimate stocks by acoustic method. Due to the obtained data from this survey, mean length was determined by years (2013, 2014, 2015) as 8,21±1,95 cm, 7.97±2,22 cm, and 8.40±1,41 cm respectively. Likewise, stock of horse mackerel was estimated as 19516 kg/nm2, 12306 kg/nm2 and 2622 kg/nm2 by years respectively. Water temperature in Turkey's eastern Black Sea coast has been decreasing from west to east. It was confirmed that, horse mackerel remain in relatively warmer parts of the water when thermocline layer exists. When the thermocline layer disappears and temperature begins to decrease, horse mackerel has an eastward migration. Water salinity did not differ between west and east. However, water salinity changed depending on the depth varying between 18-18.5 ‰ and this alteration did not affect stock distribution.