Determination of algal content of the stomach of tilapia grown in Laguna de Bay

Date

3-1989

Degree

Bachelor of Science in Agriculture

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Macrina T. Zafaralla

Abstract

The algal contents of the stomach and the large intestine of tilapia caught in Laguna de Bay during the dry months of March and April, and wet months of September and October were determined.

The sampling sites were the open-waters of Mayondon, and a fishpen in Sta. Cruz. The collected fish were dissected from the anus to the jugular region and the stomach and the large intestine were preserved in 10% FAA solution prior to microscopic examination. Water samples were also collected along with the fish samples to determine the relative density of algal species at the time the fish were caught. Water samples were preserved with a drop of I2 Lugol's solution prior to the determination of algal species composition and abundance. Species identifications were verified from fresh water samples.

Each food item was counted according to group except for the algal contents which, with exception to the diatoms, were identified and counted down to species level. The same was done with the water samples. Assessment of food composition of tilapia was done using the occurrence, % dominance, and % relative density. Base of on occurrence, Melosira sp. alone had 100% occurrence in fish stomach, followed by C. vulgaris which had 87.5% occurrence. With respect to the large intestine, M. glauca occurred in all fishes examined during the dry month of March in Mayondon while for Sta. Cruz, Melosira sp. occurred in 87.5% of the fish samples.

The species that least appeared in the stomach were P. boryanum, C. sphaericum, S. guadricauda, and Tetraedron sp. For the large intestine, P. simplex and C. sphaericum both least appeared. All of these had a 12.5% occurremnce.

Based on % dominance, Melosira sp. generally predominated with 100% dominance, followed by C. vulgaris and M. glauca both of which had a 60% dominance during the dry month of March in Mayondon. Other algae which tended to dominate were O. chalybea, 40%; and P. tenue, 30%. Basically the same species dominated in water samples except S. major.

Based on % relative density, Melosira sp. had a relatively higher % relative density among the other algal species, followed by C. vulgaris. M. glauca also tended to have a higher % relative density particularly during the dry month of March.

The digestible algae which were not found in the large intestine but were present in the stomach were the myxophytes, P. bor yanum,Anabaena sp .; the chlorophytes, S. quadricauda, Tetraedron sp., D. pulchellum, S. schroeteri; and the diatom, Cymbella sp.

The zooplankton found in water samples were Lecane- Monostyla, Keratella, Bosmina, Cyclopoida and Calanoida. These were found only in the stomach particularly Lecane, Monostyla. Keratella and Bosmina.

In general, the density of algae eaten by tilapia and those present in the water samples was higher during the dry months of March and April than during the wet months of September and October. Also, the algal species were more varied and numerous in the sampling area of Mayondon than that in Sta. Cruz.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Notes

Botany

Document Type

Thesis

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