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Size Related Dietary Variations and Morphological Correlates in Three Freshwater Fishes from Shatt Al-Arab River, Basrah, Iraq

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Abstract

This study was carried out to investigate the possible relationships of some morphometrics of gillrakers and intestine with size-related dietary variations in three sympatric freshwater fishes. A total of 245specimens of yellowfin porgy, Acanthopagrus latus, redbelly tilapia, Tilapia zilli and greenback mullet, Lizasubviridis (73, 90 and 82 specimens, respectively) were collected from Shatt Al-Arab River from Sep. 2010 toAug. 2011. To facilitate the follow up of size-related variations, specimens of each fish species were dividedinto three representative size groups. Results of food analysis using the index of relative importance, IRI,indicated noticeable iter- and intra-specific variations in food habits between the examined species, where A.latus demonstrated evident carnivorous mode of feeding, T. zilli was herbivore and L. subviridis was mostlyplanktivore. Feeding mode was reflected obviously on gill arch length, gill raker number, length and width.Liza subviridis was characterized by more numerous (41-42), longer (3.38-5.83 mm) and thinner (0.09-0.14mm) gill rakers, in comparison with other two species. Calculated gill raker gap and filtration area was variedalso between species and size groups reflecting distinctive adaptive mechanisms for feeding modes. Filtrationarea was smaller in the planktivore L. subviridis (108.9-195.5), medium in the herbivorous T. zilli (151.7-267.5) and larger in the carnivore A. latus (174.4-331.2 mm2). Relative gut length, RGL, showed relativelyopposite trend appearing larger in T. zilli (1.86-3.11), medium in L. Subviridis (1.89-2.51) and smaller in A.latus (0.9-1.06). All the studied morphometrics exhibited reasonable correlations with fish size denotingpossible ontogenetic food shifts in these species.

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Article
Some reproductive characters of the fantail goldfish Carassius auratus auratus females from rearing ponds in Basrah, Southern Iraq.
بعض الخصائص التكاثرية لإناث السمك الذهبي مروحي الذيل Carassius auratus auratus من برك الإكثار في البصرة جنوب العراق

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Abstract

This study was carried out to determine some reproductive characteristics of the fantail goldfish Carassius auratus auratus females (standard length 69-224 mm. and total weight 21.1- 255.35 g.) from rearing ponds in Basrah province, Southern Iraq. Standard length, total weight, gonad weight, absolute fecundity, relative fecundity, gonadosomatic index (GSI) and egg diameter were determined from October 2010 to April 2011 in 77 fantail goldfish females. Results showed that the studied reproductive parameters increased gradually from October, to attain peak in March and decreased again thereafter. Absolute fecundity ranged between 2877- 357246 eggs, GSI 7.28-19.11 and egg diameter 298-1006 micron. Regression relationships between the various studied morphometric and reproductive parameters were calculated and the importance of these results to the culturists of this commercially important ornamental fish species was discussed.

أجريت الدراسة لتحديد بعض الخصائص التكاثرية لإناث السمك الذهبي مروحي الذيل Carassius auratus auratus ( بطول قياسي 69-224 ملم ووزن كلي 21.1-255.35 ) من بعض برك الإكثار في البصرة. حدد الطول القياسي (ملم) والوزن الكلي للأسماك (غم) ووزن المناسل (غم) والخصوبة المطلقة (بيضة) والنسبية (بيضة/غم) والدالة المنسلية GSI وأقطار البيض( ميكرون) خلال الفترة بين تشرين الأول (أكتوبر) 2010 و نيسان (أبريل) 2011 في 77 أنثى. أظهرت النتائج إن الخصائص التكاثرية المدروسة قد ارتفعت تدريجيا من تشرين الثاني (أكتوبر) وبلغت قيم الذروة خلال آذار (مارس) ثم انخفضت بعد ذلك. وقد تراوحت الخصوبة المطلقة بين 2877-357246 بيضة والدالة المنسلية بين 7.28- 19.11 وقطر البيضة بين 298-1006 ميكرون. كما حسبت علاقات الانحدار الخطي الإحصائية بين مختلف الصفات المظهرية والتكاثرية المدروسة لتكون هذه النتائج في متناول مربي هذا النوع من أسماك الزينة ذي المردود الاقتصادي.

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