Environmental influences on the reproductive biology and population dynamics of Sardinella tawilis in Lake Taal, Philippines / Ma. Theresa Mercene-Mutia ; Macrina T. Zafaralla, chair, advisory committee.

Date

8-2015

Abstract

Environmental factors influencing the reproductive biology and population dynamics of Sardinella tawilis in Taal Lake [Philippines] were studied to address the problem on declining catch and population. Length weight relationship analysis showed negative allometry with an equation of W = 0.0151 TL sup 28. The females are more than males with a ratio of 1:06 (F:M) with size at first maturity at total length 11.5 cm in both sexes. Two peak spawning seasons were observed from February to April and July to September with an estimated average fecundity of 8,895 ova. The estimated L sub max, L sub beta and K value were 15.39, 15.5cm and 0.98 cm respectively. Meanwhile, fishing mortality, natural mortality and exploitation values were noted at 4.77, 2.15 and 0.62, respectively. The main diet comprised of 52% calonoid copepods. Tawilis larvae were identified morphologically with a total of 337 ind/100 m sup 3 collected in 9 out of 15 stations in the southeastern and western part of the lake and were barcoded through DNA analysis. Majority of the fisherfolk (95%) are highly dependent on fishing using two types of gear, namely gill net and beach seine. The average catch per unit effort of gill net and beach siene were 5 kg/day and 29 kg/day, respectively. Multivariate analysis showed that among the environmental variables, salinity and temperature were found to be the predominnat factors that influence the biological parameters of tawilis. Temperature and salinity facilitate gonadal development and spawning during the months of February to April and July to September. The high values of fish catch and catch per unit effort in March and September indicates fishing pressure which is also coincided with the spawning season of tawilis.

Document Type

Dissertation

Degree

Doctor of Philosophy in Environmental Science

College

Graduate School (GS)

Adviser/Committee Chair

Macrina T. Zafaralla

Committee Member

Macrina T. Zafaralla, Enrique P. Pacardo, Rafael D. Guerrero III, Josefina T. Dizon

Language

English

LC Subject

Sadinella, Fish populations, Fisheries, Fishing, Lakes, Fish stock assessment, Environment Environmental Science School of Environmental Science and Management

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 996 2015 E8 M47

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