بررسی حضور و تعیین رژیم غذایی شنگ (Lutra lutra) در ناحیة مصبی رودخانه‌های شرق استان گیلان: پل رود، خشک‌رود و آچارود

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه محیط زیست، دانشکده منابع طبیعی، دانشگاه گیلان، صومعه‌سرا، ایران

2 سازمان تحقیقات و آموزش کشاورزی، موسسه تحقیقات علوم شیلاتی کشور، پژوهشکده آبزی پروری آبهای داخلی (بندر انزلی)، ایران

چکیده

شنگ اوراسیایی (Lutra lutra) از جمله پستانداران ساکن گسترة زیستگاهی آب‌های داخلی ایران به‌‌شمار می‌رود که در رأس هرم غذایی و در خطر انقراض قرار دارد. مطالعات رژیم غذایی، برای درک بوم‌شناسی حیات­وحش و حفظ جمعیت آن‌ها حیاتی است. اهداف این مطالعه شامل بررسی حضور و تعیین رژیم غذایی شنگ در رودخانه­ های آچارود، خشک‌رود و پل ­رود واقع در شرق استان گیلان، و نیز بررسی میزان وابستگی این گونه به ماهیان دریای کاسپین بوده است. طول پنج کیلومتر انتهایی هر رودخانه­، در قالب سه بخش با طول تقریبی 1700 متر، بر حسب دوری یا نزدیکی به دریا مورد بررسی قرار گرفتتد. نتایج بررسی نشان داد که از طول پنج کیلومتری مورد بررسی رودخانه ­ها، شنگ تا 4/3 کیلومتری مصب حضور داشته است. در مجموع، 511 نمایة حضور با تغییرات فصلی مشخص در هر یک از بخش­ های رودخانه‌ها، مشاهده ­شد. بیشترین نمایة مشاهده ­شده در فصل پاییز و کمترین آن در فصل تابستان بود. بر اساس تجزیه و تحلیل و بررسی مدفوع‌­ها، 955 مورد طعمه شامل ماهی­ ها، سخت ­پوستان، خزندگان، دوزیستان، پرندگان و حشرات مشاهده شد. بالاترین شاخص تغذیه‌ای در سه رودخانة مورد بررسی، مربوط به ماهیان و کمترین شاخص تغذیه ­ای مربوط به حشرات بوده است. تغییرات فصلی در اقلام غذایی میان بخش ­ها نیز مشاهده شد. به‌‌طوری‌که در دو فصل پاییز و زمستان در هر سه بخش رودخانه ­ها، بیشترین شاخص تغذیه ­ای مربوط­ به ماهیان بود. در فصل بهار و پاییز، شاخص تغذیه ­ای ماهیان تغذیه ­شده عمدتاً مربوط ­به دسته ماهیان رودخانه ­ای و ماهیان مشترک رودخانه‌ای-دریایی بود. در فصل‌های تابستان و زمستان، درصد ماهیان دریایی نسبت ­به بهار و پاییز بیشتر بود. شاخص تغذیه ­ای اقلام غیرماهی نیز در فصل تابستان نسبت ­به فصول دیگر افزایش داشته است.

کلیدواژه‌ها

عنوان مقاله [English]

Investigating the presence and diet of otter (Lutra lutra) in the estuary region of eastern rivers of Guilan province: Polrood, Khoshkrod and Acharod

نویسندگان [English]

  • Saeid Eshagh Nimvari 1
  • Saeid Naderi 1
  • Alireza Mirzajani 2

1 Department of Environment , Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Iran

2 Inland Water Aquaculture Research Center,, Iranian Fisheries Science Research, Institute, Agricultural Research Education and Extension Organization (AREEO), Bandar Anzali,, Iran

چکیده [English]

The Eurasian otter (Lutra lutra) as one of the mammals of the inland waters of Iran is at the top of the food pyramid and encounter to endanger of extinction. The diet studies are critical to understanding the ecology of wildlife and preserving their populations. The objectives of this study were the presence and diet of otter in estuary region of Acharod, Khoshkrod and Polrood rivers, in the east of Guilan province, and also the study of the level of dependency of this species on fish species of the Caspian Sea. The length of the last five kilometers of each river, as three sections with an approximate length of 1700 meters, was examined in terms of distance or proximity to the sea. The results showed that of the five km length studied of the rivers, the Eurasian Otter was present up to 4/3 km of the estuary. In total, 511 presence indices with specific seasonal changes were observed in each of the river sections. The highest index was observed in the autumn season and the lowest in the summer season. Based on the analysis and investigation of spraints, 955 prey items including fishes, crustaceans, snakes, frogs, birds and insects were observed. The highest feeding index (FI) in three studied rivers was for fish and the lowest FI was for insects. Also, the seasonal changes in food items between sections were observed. So that in the two seasons of autumn and winter in all three sections of the rivers, the highest FI was for fish. In the spring and autumn, the feeding index of the fed fish was mainly related to river fish and common river-sea fish. In summer and winter, the percentage of sea fish was higher than in spring and autumn. The feeding index of non-fish items has also increased in the summer compared to other seasons.

کلیدواژه‌ها [English]

  • Eurasian otter
  • Feeding index
  • Presence
  • Caspian Sea
  • Guilan province
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