Species Composition, Distribution, Biomass Trends and Exploitation of Dominant Fish Species in Manila Bay using Experimental Trawl Survey

An experimental trawl fishing survey was conducted in Manila Bay from March 2014 to October 2015 at sixteen (16) pre-established dragging stations adapted from an earlier study (MADECOR, 1995). Using a commercial otter trawl, the average trawling speed during fishing operations was 6-7 km/hour. Analysis of catches focused on biomass trends, species composition, distribution and exploitation of dominant species. A total of 146 fish and invertebrate species belonging to 48 families were recorded during the survey period wherein most of the catches were dominated by small pelagic species such as anchovies and sardines. Exploitation rates (E) for the six (6) dominant species (Sardinella gibbosa, Sardinella fimbriata, Valamugil seheli, Mugil cephalus, Encrasicholina devisi and Stolephorous commersonnii) shows signs of overfishing. The estimated demersal fish biomass of the bay revealed that the relative decline was about 90% from the 1947 baseline study

Reproductive Biology of Common Small Pelagic Fishes in Manila Bay, Philippines

Reproductive biology of the three dominant species (Sardinella gibbosa, Sardinella fimbriata, and Rastrelliger kanagurta) were studied in Manila Bay from January 2014 to December 2015. The data were collected from landed catch (coming from gillnet, lift net, purse seine, ringnet, and trawl) and during the actual trawl fishing survey. A total of 2,383 Sardinella gibbosa, 2,334 Sardinella fimbriata, and 549 Rastrelliger kanagurta were analyzed by pooling the two years data. The overall female to male ratio conformed to the expected 1:1 sex ratio. These species spawn throughout the year with major peak in March and April and minor peak in October to December for Sardinella gibbosa; with major peak in February to May and minor peak in October to December for Sardinella fimbriata; and for Rastrelliger kanagurta, with major peak in October to December and minor peak in May and June. The GSI values correlate with the maturation of the gonads of these species. The length at maturity (Lm50) was calculated at 12.75 cm in males and 13.25 cm in females for S. gibbosa; 12.25 cm in males and 12.75 cm in females for S. fimbriata; and 25.5 cm in males and 24.5 cm in females for R. kanagurta