Akın Türker İLKYAZ, Hasan Tuncay KINACIGİL, Gülnur METİN

Growth, mortality, and reproduction of poor cod (Trisopterus minutus Linn., 1758) in the central Aegean Sea

Trol çekimleri ile 1.527 adet tavuk balığı (Trisopterus minutus Linn., 1758) Nisan 2001 ile Mart 2002 tarihleri arasında İzmir Körfezi’nden (Orta Ege Denizi) örneklenmiştir. Örneklenen bireylerin total boylarının 10,6 cm (minimum, Eylül) ile 24,8 cm (Nisan) arasında dağılım gösterdiği gözlenmiştir. Bireylerin %53’ünün erkek, %41’inin dişi ve %6’sının eşeysel olgunluğa ulaşmamış bireylerden oluştuğu tespit edilmiştir. Stokdaki dişi:erkek oranının 1:1,3 olduğu ve bireylerin I-V yaşları arasındaki dağılım gösterdiği gözlenmiştir. Von Bertalanffy büyüme parametreleri; L∞= 28,1 cm, W∞= 254,0 gr, K = 0,26 yıl–1 ve to = –1,52 yıl olarak hesaplanmıştır. Dişilerde ilk üreme boyunun 13,3 cm, erkeklerde ise bu boyun 12,5 cm olduğu bulunmuştur. Yumurtlamanın Aralık ayında başladığı, Ocak ayında maksimum seviyeye ulaştığı ve Nisan ayına kadar sürdüğü gözlenmiştir. Yumurta verimliliğinin 1,236 ile 21,463 yumurta/dişi arasında olduğu ve bu verimin balık boyu ve ağırlığı ile ilişkili olduğu tespit edilmiştir. Stoktaki toplam (Z), doğal (M) ve balıkçılıktan gelen ölüm (F) ile sömürülme oranları (E) sırası ile Z = 0,82, M = 0,38, F = 0,44 ve E = 0,57 yıl–1 olarak hesaplanmıştır. Elde edilen bilgiler ışığında, tür için minimum avlama boyunun 14 cm, av sezon yasağının Ocak ile Nisan ayları arasında olması önerilmektedir. Sömürülme oranı dikkate alındığında, stok üzerindeki av baskısının normalin biraz üzerinde gerçekleştiği gözlenmektedir.

Orta Ege denizi tavuk balığı (Trisopterus minutus Linn., 1758)’nın büyüme, ölüm ve üreme özellikleri

A total of 1527 of poor cod (Trisopterus minutus Linn., 1758) were collected by trawl hauls between April 2001 and March 2002 from ‹zmir Bay (central Aegean Sea). The size of the fish (total length) ranged from 10.6 cm (minimum, September) and 24.8 cm (April). The population was composed of 53% males, 41% females, and 6% immature individuals, with a female to male ratio of 1:1.3. The age composition of the samples was from I to V. The von Bertalanffy growth parameters were L∞ = 28.1 cm, W∞ = 254.0 g, K = 0.26 y–1, and to = –1.52 y. The length at first sexual maturity was 13.3 cm in females and 12.5 cm in males. Spawning season begins in December and reaches its maximum level in January while continuing April. Fecundity ranged from 1236 to 21,463 eggs/female and showed significant correlation with fish length and weight. The total (Z), natural (M), and fishing mortality (F) rates, and the exploitation ratio (E) for all individuals were estimated respectively as Z = 0.82, M = 0.38, F = 0.44, and E = 0.57 y–1. This shows that the poor cod smaller than 14 cm must not be harvested and fishing should be prohibited from January to April and that the poor cod stock in the central Aegan Sea is being exploited at a slightly higher than the optimal level.

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