Spatio - temporal distribution of ichthyoplankton in Manila Bay in relation to oceanographic conditions / Elsa F. Furio and five others

Includes bibliographical references

Manila Bay faces serious problems today such as pollution, coastal area reclamation and infrastructure, overfishing, and other activities that worsen the present condition of the bay. It is considered as one of the major fishing grounds in the Philippines. Fish eggs and larvae collection was carried out to determine their distribution, abundance, and composition in the bay. Eight established sampling stations were placed throughout the bay with an average distance of 5-6 nautical miles apart and sampled every other month on a monsoonal basis. Bongo net (360 microns mesh size, 1.5 meters in length, and a diameter of 50-centimeter mouth opening) with attached calibrated flowmeter was used in collecting fish larvae. Physical (salinity, temperature,), chemical (nitrite, nitrate, phosphate, silicate, dissolved oxygen), and biological (phytoplankton, zooplankton) parameters were also carefully studied to be able to explain such uncommon event within the bay. In spite of the current status and worsening condition of water quality of the bay, high abundances of fish eggs and larvae were consistently observed during the northeast monsoon surveys (March) from 2012 to 2015. A total of 3,008 individuals were identified belonging to 34 fish families. The highest fish egg density was observed during March 2013 with 1,550 ind./100m3, followed by March 2012 and 2015 with 1,484 ind./100m3 and 1,182 ind./100m3, respectively. An abundance of fish larvae was observed during March 2015 with 414 ind./100m3, followed by March 2012 (329 ind./100m3), and March 2014 (311 ind./100m3). The lowest density observed was in September 2012 with a density of 132 ind/100m3 fish eggs and 46 ind/100m3 fish larvae. The results were consistent that most fish eggs aggregate in the middle part of the bay especially in Stations 4 and 2 from 2012-2015. For fish larvae, they were consistently found in the eastern part of the bay (stations 6, 8, and 7) throughout the duration of the study, it was also the areas where high concentrations of phytoplankton, zooplankton, and nutrients were observed. A high abundance of fish eggs and fish larvae was observed during northeast monsoon than southwest monsoon. In addition, fish larvae family was dominated by small pelagic fish such as sardines, slipmouths, and mullets. The most dominant fish families found were Clupeidae, followed Leiognathidae, and Nemipteridae. Sillaginidae and Mugilidae were also included in the top five abundant families that occur during every sampling period were.

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