Menzelet Baraj Gölündeki Doğal Yayın, Silurus glanis L., 1758, Populasyonunda Üreme Biyolojisi
Türkiye’nin Do¤u Akdeniz Bölgesi’nde bulunan Menzelet Baraj Gölü’ndeki Silurus glanis‘in üreme aktiviteleri 12 ayl›k bir periyotta incelenmifltir. ‹ncelenen 245 adet S. glanis bireylerinde total boylar 33,4 cm (220 g) ile 195,0 cm (48.000 g) aras›nda ve yafl kompozisyonu ise 1-14 aras›nda da¤›l›m göstermifltir. Ayl›k Gonadosomatik Index (GSI) ve olgunluk safhalar›n›n incelenmesiyle Silurus glanis’in yumurta dökme periyodunun Haziranda bafllay›p A¤ustos’a kadar sürdü¤ü tesbit edilmifltir. Erkekler 3 yafl›nda ve 78,82 cm total boyda, diflifller ise 87,05 cm total boy ve 4. yaflta efleysel olgunlu¤a gelmifl ve erkeklerin daha erken olgunlaflt›¤› görülmüfltür. Av yasa¤›n›n May›s ay› sonunda bafllay›p A¤ustos ay› bafl›na kadar sürmesi gerekti¤i ve yaklafl›k 90 cm’den küçük bireylerin avlanmamas› gerekti¤i kanaatine var›lm›flt›r. Toplam 49 difli bireyde incelenen yumurta say›lar› 9033 ile 340.461 yumurta/bal›k aras›nda de¤iflmifl ve fekondite ile total boy (ln F = 5,4034 x ln L – 14,126; r = 0,8987), vücut a¤›rl›¤› (ln F = 1,7171 x ln W – 4,440; r = 0.9062) ve ovaryum a¤›rl›¤› F = 115,36x OW + 30.105; r = 0,8721) aras›nda pozitif bir korelasyon bulunmufltur. K›smi fekondite ± CI(%95), 8434 ± 1114 yumurta/kg bal›k olarak bulunmufl ve üreme dönemi öncesi bir gram ovaryum parças›nda 195 adet yumurta tesbit edilmifltir. Yumurta büyüklü¤ünde ayl›k farkl›l›klar gözlenmifl ve May›s ay›nda yumurta çaplar› 1,00 mm ile 3,63 mm aras›nda de¤iflmifltir. Yumurta büyüklü¤ü ile ovaryumdaki yumurta say›s› aras›nda negatif bir korelasyon vard›r.
Reproductive Biology in a Native European Catfish, Silurus glanis L., 1758, Population in Menzelet Reservoir
The reproductive activities of Silurus glanis were investigated over 12 months in Menzelet Reservoir, in the East Mediterranean region of Turkey. Total length of the examined 245 S. glanis varied from 33.4 cm (220 g) to 195.0 cm (48,000 g), and age distribution ranged between 1 and 14. Observations on the seasonal distribution of the maturity stages and variations in the gonadosomatic index (GSI) confirmed that Silurus glanis has a prolonged spawning period extending from the beginning of June to August. The males mature earlier than the females, at a minimum size of 78.82 cm in total length and at age 3, while the females mature at a minimum size of 87.05 cm in total length and at age 4. It was determined that a fishing ban should be applied from the end of May to the beginning of August and fish smaller than 90 cm in length should not be caught. Fecundity estimates based on 49 mature females ranged from 9033 to 340,461 eggs/fish and correlated positively with total length (ln F = 5.4034 x ln L - 14.126; r = 0.8987), body weight (ln F = 1.7171 x ln W - 4.440; r = 0.9062) and ovary weight (F = 115.36 x OW +30105 r = 0.8721). Relative fecundity ± CI(95%) for each kilogram of female fish was 8434 ± 1114 eggs and each gram of ovaria consists of 195 eggs prior to the spawning season. Egg size varied monthly and egg diameters ranged from 1.00 mm to 3.63 mm in May. Egg size correlated negatively with the number of eggs in the ovaria.