Age Determination and Body Length Relationship of Two-Spot Red Snapper (Lutjanus bohar)

Otolith study on fifty two-spot red snappers (Lutjanus bohar) in the Davao Gulf, Philippines, was conducted to describe their growth pattern, determine the age structure, and estimate their age at sexual maturity. Samples were obtained from Toril and Bankerohan Public Markets in Davao from Februay to June 2015. Fish morphometrics, otolith extraction, and age determination followed. Length-weight relationship showed that L. bohar follows isometric growth pattern (b = 3.0015). Somatic and otolith morphometrics gave significant correlations where otolith length and total length relationship had the highest R2 value (R2= 0.9382). Out of the samples, twenty-one of the sagittal otoliths ranges from three to seven years old. The parameters obtained from the age-at-length data fitted to von Bertalanffy growth function were K = 0.81 and L∞ = 28.9 cm, with estimated age at maturity of six years old. The growth performance index (φ = 2.83) revealed that L. bohar in Davao Gulf has a faster growth rate. Faster growth rate leading to earlier maturity and smaller size-at-maturity may indicate the effects of environmental factors and fishing pressure to slow-growing fishes. We recommend studying the population ecology of L. bohar in Davao Gulf and considering a larger sample size in future researches

Spatio-temporal Distribution and Abundance of Crown-of-Thorns Starfish (Acanthaster planci L.) in Three Marine Protected Areas (MPAs) around the Island Garden City of Samal, Philippines

The spatial and temporal distribution of crown-of-thorns starfish or COTS (Acanthaster planci L.) was investigated in three marine protected areas (MPAs) around the Island Garden City of Samal (IGaCoS), Philippines, from December 2008 to December 2009. Methods include photo quadrat for the live coral cover and belt transect for the density of COTS and its predators. There was a significant difference in the spatial distribution of COTS among MPAs. Sanipaan Marine Park (SMP) had the highest COTS density while Coral Garden and Aundanao MPAs had the least. Variability of COTS density was attributed to percent coral cover and human intervention (i.e., COTS clean-up drive). At temporal scale, only data from SMP fitted for the analysis. There was no significant difference observed during the sampling periods conducted in April, August, and November 2009. The results suggest longer time of monitoring to cover the life span of COTS, taking into consideration  the probable causes for infestation, whether anthropogenic (i.e., harvesting leading to mass spawning) or natural. In conclusion, the spatial distribution of COTS depends on the abundance of their preferred food while the temporal distribution is probably influenced by environmental conditions over time

Measuring the Economic Impact of Weather Determinants on Aquaculture in the Davao Region, Philippines

Aquaculture is an important determinant of economic growth in the Davao Region in the Southern Philippines because it contributes towards increasing employment and agribusiness development opportunities. However, the industry faces various issues that affect farm productivity. One of these challenges pertains to welfare effects emanating from changing patterns of weather variables. Hence, this research aimed to measure the impact of weather determinants on aquaculture production’s net income based on surveyed farms in the Davao Region. Based on the Ricardian approach, our econometric model specifies the dependent variable as net income (PhP/ha) and this is a function of weather variables such as precipitation, humidity, and agro-climatic and socio-demographic variables. From the results, weather and agro-climatic variability have statistically significant effects on aquaculture’s net income. More specifically, a unit increase in the standard deviation of rain value increases net income by PhP12,730. However, an increase in one standard deviation of average air humidity decreased net income by approximately PhP2,940. Finally, unit increases in the standard deviation of soil moisture and soil temperature translate to increases in net income by approximately PhP16,150 and PhP16,170. Thus, given the results, strategies that would enable aquaculture farmers to mitigate and adapt to changing weather conditions should be implemented. Also, weather stations should be updated and upgraded in order to provide accurate readings and forecasts so that aquaculture farmers’ decision making will be improved with regards to their farm practices

Changes in the fish diversity and abundance on a heavily fished fringing reef on Santiago Island, Pangasinan, Philippines

Fish assemblages on the reef slope, reef flat, and seagrass beds on Santiago Island were sampled over 18 months in 1992-1993 as part of a 6-year reef monitoring project started in 1986. Abundance and species diversity were analyzed by a variety of indices, and by multi-dimensional scaling and correlated ordered similarity matrix. The monitoring showed a distinct shift in the reef slope fish composition during the first half of 1988. Of the 100 most abundant species, 21 species showed significant reductions in abundance, and 20 species showed significant increases. Differences were not due to depth preference or feeding habits. Fishing pressure was apparently responsible for declines in Cheilinus trilobatus, Acanthurus nigricauda, and Naso literatus, as well as a general decline in the family Acanthuridae (surgeonfishes). However, analysis of site preferences of the decreasing species and the increasing species indicated a shift in community composition from those species preferring more coral cover to those preferring more sand, rock, and possibly Sargassum seaweed. Site preferences were determined from benthic life form transects done in 1992. Of 35 significantly changing species for which habitat data was obtained, 24 fit the hypothesis of habitat change. This supports the proposition from previous studies that the major cause of change in the reef slope fish community was the destructive fishing activity associated with Malthusian overfishing. Similar analyses of the fish assemblages on the reef flat and on the seagrass beds showed seasonal effects, particularly in the latter, but no strong shift comparable to that of the reef slope. These latter areas had been subjected to greater fishing pressure for a longer period. Reef fish populations such as those in Bolinao tend to be highly resilient provided the larval supply is not adversely affected. However, subtle changes in the cover of coral on a reef can lead to major changes in the composition of the fish community. Coral cover is being widely diminished on Philippine reefs, and substantial changes in the fish communities may be anticipated, even on reefs with initially low coral cover. These changes may affect the utility and immediate value of the fish to local fishers and the market systems they supply. It is of great urgency to stop destructive fishing practices such as blasting and use of cyanide, and to develop anchoring methods that are minimally destructive. There is a strong predictive relation between the numbers of fish (abundance) in an area and the numbers of species (biodiversity) they include. As fish populations decline due to destructive fishing, or highly concentrated non-destructive fishing, the local species richness may be expected to decline. This decline may have serious short-term social and economic consequences, as well as far-reaching long-term environmental effects. Efforts to reduce overfishing must be intensified—though reduction of birth rate, provision of alternative livelihoods, and curbing of destructive fishing — in order to prevent a very distressing future for the Philippine marine environment and the people it supports

Percentage of destroyed and declining reef in each species' range vs Red List Category.

<p>Center line = median value, box boundaries = 25^th and 75^th percentiles, whiskers = 10^th and 90^th percentiles, black dots = outliers.</p

Red List Category by Proportion of MPA in each species' range.

<p>Center line = median value, box boundaries = 25^th and 75^th percentiles, whiskers = 10^th and 90^th percentiles, black dots = outliers.</p

Feeding classification of parrotfishes and surgeonfishes based on dietary targets and post-digestive processes.

<p>Feeding classification of parrotfishes and surgeonfishes based on dietary targets and post-digestive processes.</p

Regional Red List Assessments of commercially important parrotfishes and surgeonfishes in the Coral Triangle (EN = Endangered, VU = Vulnerable, NT = Near Threatened, LC = Least Concern, DD = Data Deficient).

<p>Regional Red List Assessments of commercially important parrotfishes and surgeonfishes in the Coral Triangle (EN = Endangered, VU = Vulnerable, NT = Near Threatened, LC = Least Concern, DD = Data Deficient).</p

Percentage of parrotfishes and surgeonfishes in each habitat type.

<p>Percentage of parrotfishes and surgeonfishes in each habitat type.</p

Number of species threatened by fisheries.

<p>Number of species threatened by fisheries.</p