Sex Ratio Response to High Temperature During Early Development of Rainbow Trout (Oncorhynchus mykiss) in Farmed Stocks

Çalışmanın amacı birbirinden uzak kuluçkahanelerde ticari olarak yetiştirilen alabalık (Onchorhynchus mykiss) popülasyonlarında erken dönemde uygulanan yüksek sıcaklığın cinsiyet oranları üzerine etkisini araştırmaktır. Denemelerde sıcaklık ve kontrol grupları olmak üzere beş farklı çiftlikten yaklaşık 32500 larva kullanılmıştır. Sıcaklık denemeleri 17.5°C' de 10 günlük larvalara 40 gün olarak uygulanmıştır. Kontrol grubu (%52.1) ve beklenen teorik cinsiyet oranı (1:1) dikkate alındığında, çalışılan popülasyonların sadece birinde sıcaklık cinsiyet oranı üzerinde dişilik yönünde (%67.5) önemli bir etki oluşturmuştur. Aynı popülasyonda dişiler erkeklere göre %8.3 daha fazla gelişmiştir. Buna rağmen bu sonucun popülasyon genelinde tekrarlanabilirliğinin ve fotoperiyot uygulanan stoklarda ise benzeri cinsiyet eğiliminin olmadığı anlaşılmıştır. Sıcaklık uygulamaları yaşama oranlarını olumsuz etkilememiştir. Bu sonuçlar kültürü yapılan stoklarda popülasyonun genetik geçmişinden çok termal duyarlılığa sahip bireylerin sayısına bağlı olarak mümkün olabileceğini göstermiştir.

Erken Gelişim Döneminde Uygulanan Yüksek Sıcaklığın Gökkuşağı Alabalığının (Oncorhynchus mykiss) Çiftlik Stoklarındaki Cinsiyet Oranına Etkisi

The objective of the study was to investigate the effect of high temperature on sex ratios of early stage rainbow trout (Onchorhynchus mykiss) in commercially farmed populations from distinct hatcheries. Almost 32500 larvae from five different farms were used in experiments as thermal groups and their corresponding controls. Temperature treatments were conducted at 17.5°C for 40 days starting at day 10 after hatching. In only one population, the sex ratio was skewed significantly in favor of females in thermally treated group (67.5%), when compared to control group (52.1%) and there was deviation from the expected 1:1 ratio. In the treatment group the females grew 8.3% more than males. However there was no repeatiblity and any skewness in sex ratio of progenies from photoperiod induced spawning. Survival rates were not affected by the thermal treatments. The results showed that the increasing of femaleness of farmed stocks is possible by thermal treatment in rainbow trout and which depends on percentage of thermosensitive individuals rather than genetic background of population.

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