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The Composition in Different Size Groups and Index of Relative Importance (Iri) of Callinectes amnicola (De Rochebrune, 1883) Food from Okpoka Creek, Niger Delta, Nigeria

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Author(s): J.F.N. Abowei

Journal: International Journal of Animal and Veterinary Advances
ISSN 2041-2894

Volume: 1;
Issue: 2;
Start page: 83;
Date: 2009;
Original page

Keywords: Callinentes amnicola | sizes | food | importance | Okpoka creek | Nigeria

ABSTRACT
The composition in different size groups, and index of relative importance of Callinectes amnicolafood from Okpoka creek was studied for a period of two years (January 2006 –December 2007). Crabs less than10mm were absent in the catch. Crab appendages, bivalve shells, bivalve tissues, gastropod shells and annelidswere absent in smaller crabs (10-19.9 mm) and (20-29.9 mm). Algae cells were absent in crab (40-49.9 mmto 70-79.9 mm) size groups. Crustacean, Pisces and mollusca were common in the stomachs of the larger sizegroup. The numerical method showed that algae cells (46.9%) were most abundant in size group (10-19.9 mm)followed by 20-29.9 mm (33.1% ) size group and 30-39.9 mm (20.0% ) size group. Crustacean (shrimp parts32.7% and crab appendages 35.2%) was numerically higher in (70-79.9 mm) size class. The frequency ofoccurrence method showed that, Fish flesh accounted for 19.8% 17.6%, 15.4% 13.2%, 11.0% and 9.9% of thestomach contents in the 30-39.9 mm, 20-29.9 mm, 10-19.9 mm (50-59.9 mm, 70-79.9 mm), 40-49.9 mm, 60-69.9 mm size group respectively. Fish scales occurred most in (70-79.9 mm) size group with a value of 19.4%followed by 15.3% (50-59.9 mm) size group whereas the other size groups had between 10.4% and 14.6%in occurrence. The percentage occurrence of fish bones /spines in 10-19.9mm to 70-79.9mm size groups rangedbetween 8.7% and 17.4%. The highest (17.4%) was recorded in (40-49.9 mm) size group while the least (8.7%)was obtained in (10 – 19.9mm) size group. Bivalve shells (29.5%) and bivalve tissue (28.6%) led in occurrencein (70-79.9mm) size group whereas 28.6% (gastropod shells) encountered in (70-79.9 mm) size group, followedin decreasing order of occurrence by size groups 60-69.9mm (25.0%), 40-49.9 mm (21.2%), 50-59.9 mm(16.3%) and 30-39.9 mm (15.4%). Shrimp parts and crab appendages occurred consistently in (50-59.9 mmto 70-79.9 mm) size groups with the highest values (33.0% and 31.1%) in (70-79.9 mm) size group while thelowest (7.4%) was for (30-39.9mm) size group. Algae cells and higher plant parts accounted for 40.6% and28.0% respectively of the stomach contents in 10-19.9mm. The point’s method that showed shrimp partscontributed 33.3% and 26.3% of the stomach content in the 70-79.9mm and 60-69.9mm size groupsrespectively. Similarly, crab appendages accounted for 35.5% in 70-79.9mm size group and 31.2% in 60-69.99mm size group. In the 70 – 79.99mm size group, fish flesh was 38.0%, fish scales 18.9% and fishbones/spines (18.9%) respectively. The highest values bivalve shells (31.9%) and bivalve tissues (32.1% ) wererecorded in (50-59.9mm) and 60-69.9mm) size groups respectively. Whereas the 10-19.9mm and 20- 29.9mmsize groups had no bivalve shell or tissue in their stomachs. Gastropods shells values ranged from 17.7% to23.2% by points with the highest (23.2%) recording in size groups (30-39.99 to 70-79.99 mm) while the least(17.7%) was in (70-79.9 mm) size group. Annelids scored between 4.2% and 37.5% points amongst (30-39.9mm to 70-79.9 mm) size groups with the highest and lowest values recorded in (70-79.9 mm) and (30-39.9 mm)size groups respectively. Index of relative importance (IRI) in the food items showed importance ranged from7.14% to 0.07% in 2006 with the highest percentage index of relative importance recorded for bivalve shells(7.14%) and the lowest (0.07%) for the annelids. On the contrary, the percentage index of relative importancevalues varied from 0.34% to 21.67% based on increasing order of importance in 2007. Bivalve shells had IRIvalue of 427.44 (21.67%) whereas Annelids had IRI valve of 6.66 (0.34%). Similarly the highest value of21.67% and lowest (0.34%) were recorded for bivalve shells and annelids respectively.
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