أقلمة اصبعيات البوري دهبان (Liza aurata) للمياه العذبة و لدرجة ملوحة منخفضة
Abstract
تم إجراء البحث لدراسة مدى تأثير الأقلمة الفورية و المتدرجة للمياه العذبة و كذلك الأقلمة المتدرجة عند درجة ملوحة3‰ على معاملات النمو عند اصبعيات البوري دهبان التي تم جمعها مباشرة من البحر و بعد استراحة قصيرة قمنا بتوزيع الاصبعيات الى أحواض زجاجية سعتها 100 ليتر و بمعدل 30 إصبعية لكل حوض. تم أقلمة اصبعيات الحوض الأول بشكل فوري مباشر للمياه العذبة, بينما أقلمت اصبعيات الحوض الثاني تدريجيا" للمياه العذبة, أما اصبعيات الحوض الثالث فتم أقلمتها بشكل تدريجي لدرجة ملوحة مختارة (3‰) و تركت اصبعيات الحوض الرابع كشاهد في مياه البحر. تم تغذية الاصبعيات بعليقه تحوي 35 % بروتين و 500 كح/100 غ عليقة بمعدل مرتين في اليوم حتى الشبع لمدة 75.يوما".
أشارت النتائج أن اصبعيات الحوضين الأول و الثاني نفقت كلها و بشكل تدريجي مظهرة نفس العوارض المرضية و المتضمنة الإجهاد و اللون الأسود و فقدان الشهية و السباحة غير الطبيعية.
بينما بقيت اصبعيات الحوض الثالث على قيد الحياة حتى نهاية التجربة و أظهرت معدلا ت نمو و معامل تحويل غذاء مقارباً (P>0.05) لتلك الاصبعيات المرباة في مياه البحر و كلاهما أظهرا معدل وفيات متقاربة (P>0.05) .
This study was conducted to investigate the effect of abrupt and gradual acclimation of Liza aurata fingerlings to fresh water and gradual acclimation to a selected salinity 3‰. L.aurata fingerlings were collected directly from the sea and duplicate groups of 30 fingerlings were distributed after rest to glass aquaria (100 liter capacity). The first group was acclimated abruptly to fresh water, the second gradually to fresh water, the third was acclimated gradually to 3‰ and the last group was left as control in sea water. The fingerlings were fed artificial diet (35% protein and 500 kcal GE/100g), twice a day to satiation for 75 days.
The results revealed that the first and the second group of fingerlings died gradually showing the same symptoms including stress, dark coloration, loss of appetite and abnormal swimming behavior.
While the fingerlings in the third aquarium stayed alive to the end, and even their growth rates and feed utilization efficiency were comparable (P>0.05) to those lived in sea water.
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