Age and size at sexual maturity of white goby (Glossogobius Giurus), a common species of fish of Laguna de Bay with notes on its food habits / Josefina R.S. Marquez

Includes bibliographical references

The pronounced depletion of the goby fishery of Laguna de Bay after 1950, probably resulting from the use of a non-selective fishing gear, the geket, initiated this study of the biyang puti (Glossogobius giurus). The analysis of the length frequencies of 3,768 specimens, the examination of the ovaries of 1,019 female specimens and the measurement of the diameters of 3,233 ova formed the bases for the determination of the age and size at first sexual maturity of this species, collected from the Cardona and Taguig areas of Laguna de Bay, from August 1958 to August 1959. The fish, on the average, matures at the end of its first year of life at size range 105-114.9 millimeters. The expanded or multiple spawning habit is characteristic of the species. However, maximum spawning activity takes place from June to August. Mature eggs measure from 0.55 to 0.83 mm. in diameter. Although the detailed study of the sexual maturity stages of the male biyang puti was not done, yet a close correlation with the maturity stages of corresponding female size groups was observed. It was found from the 161 stomachs examined that although biyang puti is predominantly a vegetarian, yet it also utilizes zooplankton foi'ms and other miscellaneous food items. Furthermore, it is at the same time a piscivore, feeding on its own kind. There is no significant variation in the kind of food items taken in by the different size groups. The presence of an unidentified fluke in the majority of the size ranges of fish examined suggests a case of parasitism which might be worthy of future study.

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