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Length – Weight and Length – Length Relationships,
Condition Factor, Sex Ratio and Gonadosomatic Index of
the Ariid Catfishes Arius dispar and Arius manillensis
(Siluriformes: Ariidae) in Laguna de Bay, Philippines

Brian S. Santos1, Reynand Jay C. Canoy1, 2,
Jazzlyn M. Tango-Imperial1,3, and Jonas P. Quilang1*

1Institute of Biology, College of Science, University of the Philippines,
1101 Diliman, Quezon City, Philippines
2Institute of Human Genetics, National Institutes of Health,
University of the Philippines Manila, 625 Pedro Gil St, Ermita, Manila, 1000 Philippines
3Department of Biology, College of Science, Bicol University, 4500 Legazpi City, Philippines

corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

ABSTRACT
The ariid catfishes Arius dispar and Arius manillensis are commercially important in the Philippines and have been overexploited in the past. This study describes for the first time the length-weight and length-length relationships, condition factor, sex ratio, and gonadosomatic index of the two species. A total of 1,698 A. dispar and 874 A. manillensis were collected from Laguna de Bay over the period of 12 months to assess the aforementioned parameters. For both species, the sex ratio significantly differed from equality, the length-length relationships were highly significant and the coefficients of determination (r2) were all greater than 0.96. Length frequency analysis indicates overfishing for both species. The average monthly gonadosomatic index (GSI) ranged from 0.04 to 0.15 in A. dispar males and from 0.23 to 2.99 in females. The average monthly GSI ranged from 0.04 to 0.49 in A. manillensis males and from 0.28 to 4.02 in females. For females of each of the two species, the GSI had two peaks: one from February to May (dry months) and the other from July to September (wet months). These peaks might correspond to the spawning runs of these two species. This study provides baseline information which can be used for the management and conservation of these economically important fishery resources.

INTRODUCTION
The ariid catfishes Arius dispar Herre, 1926 and A. manillensis Valenciennes, 1840 are both commercially important in the Philippines. A. dispar is a native species in the Philippines and is found also in Taiwan and possibly northern Borneo (Kailola 1999). The species A. dispar was described and named by Herre in 1926 from the specimens he obtained from Laguna de Bay, Pasig River, and Quiapo Market in Manila. Arius manillensis is an endemic species in the Philippines. Both species, locally known as kanduli, are found in Laguna de Bay, the largest lake in the Philippines, with an area of about 90,000 ha and an average depth of 2.8 m. The lake is located on the Philippine island of Luzon and lies in about 14°0’0” N latitude and 121°5’59” E longitude. In addition to A. dispar and A. manillensis, three other species of kanduli have been reported in Laguna de Bay, namely, Arius goniaspis, A. thalassinus, and Hemipimelodus manillensis (Herre 1926; Aldaba 1931). Mane (1929) and Aldaba (1931) reported that commercial catches of kanduli consisted mainly of A. manillensis and that the other species were very rare. Only A. dispar and A. manillensis were found in this study and in the study by Vallejo (1985), Santos and Quilang (2012), and Yu and Quilang (2015). . . . . read more

 

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