YEAR: 2020
Occurrence and recurrence: the fish kill story in Lake Buhi,
Philippines
Plutomeo M. Nieves, Antonino B. Mendoza Jr., Sandy Rey B. Bradecina
Abstract. Fish cage farming is of paramount importance to lake dwellers income and livelihood
and to domestic fish supply. However, the occurrence and recurrence of fish kill have been
reported annually with serious economic losses. This work explored the causes of occurrence
and recurrence of fish kill in the context of finding adaptive solution. Dataset for the study was
generated through key informant interview, focused group discussion and secondary data
analysis. Problem Tree was used to identify the root-cause and SWOT analysis was employed to
craft best practice guideline for Local Government Unit in outlining the action plans for
management of cage aquaculture. Findings reveal the fish kill occurrence can be traced from the
natural and human-induced stresses and mismanagement of lake’s resources. Typhoons and
prevailing trade winds play a major role as triggering factor while the uncontrolled number of
cages and unsustainable farming practices are the major determinants of fish kill event. The
interaction between water temperature, dissolved oxygen, wind mixing and by-products of
decomposition (i.e. ammonia-nitrogen and H2S) as a result of overfeed and lake over-use are the
key elements of fish kill in the lake. Monitoring critical levels of water temperature and dissolved
oxygen is useful information in fish kill prediction. Finally, given that the lake is a common property
with multiple use nature, a multisectoral management approach is necessary to sustain the fish
cage industry.
Key Words: fish cage, fish kill, eutrophication, problem tree analysis, dissolved oxygen.
Sinusoidal growth, recruitment, mortality, yield-per-recruit analysis
of Buried fan scallop Mimachlamys funebris (Reeve, 1853) and
their implications for mariculture
Ian Cris R. Buban; Christian D. Cabiles; Renan U. Bobiles; Alex P. Camaya; Victor S.
Soliman
Abstract
This study described the growth, mortality, recruitment pattern and exploitation rate of the
Buried fan scallop (Mimachlamys funebris) in Asid Gulf, Philippines. Monthly length-frequency data
(N=3988) from April 2018 to March 2019 were used to examine population parameters using FISAT
II. Two estimates of natural mortalities were used to compare variability of limit exploitation rates.
Modelling through the oscillating von Bertalanffy growth function revealed that the species is fast
growing (K=1.1 year–1) attaining SH∞ of 10.5 cm. Adequacy in the use of the sinusoidal version of the
growth formula hinges on the mean annual temperature difference reported in the gulf to be 2°C.
Recruitment pattern was continuous and bimodal throughout the year with two high pulses in April–
May and September consistent with the reproductive seasonality reported for congeneric species.
Fishing mortality coefficients (4.26 and 4.82 year–1) were higher than the natural mortality coefficients
(0.543 and 1.1 year–1). Yield and biomass-per-recruit analysis showed that the current exploitation
rates are 112% (Ecurr1 = 0.90) and 92% (Ecurr2 = 0.80) higher than the biological reference points adopted
for the study particularly E50. These results demonstrate that M. funebris stock is overexploited, which
necessitates effective management measures including mariculture.
Keywords: Length-frequency analysis, population parameters, stock assessment, sustainable
management
YEAR: 2021
Virtual Population Analysis of Glory Scallop (Mimachlamys
gloriosa, Reeve 1853) in Asid Gulf, Philippines
Abstract
Virtual population analysis using the Jones’ length-based cohort method was conducted to the
Glory scallop (Mimachlamys gloriosa Reeve, 1853) from Asid Gulf, Philippines. The study aimed
to reconstruct the biomass and population structure as inputs to estimating the maximum
sustainable yield (MSY) along with the fishing mortality expended on the stock and evaluate the
effect of introducing minimum size restriction to the yield and biomass of M. gloriosa. Lengthfrequency data sampled from commercial catches covering 12 months from April 2018 to March
2019 were used and analyzed. The proportion of M. gloriosa from the total scallop production was
transformed into total catches (in numbers) using the allometric length–weight relationship
W = 0.5632L2.295 (R2 = 0.90). The estimated population of M. gloriosa is about 300,000
individuals, equivalent to a mean biomass of 6.76 tonnes (T). The estimated total yield of 8.09 T
is relatively higher than the estimated maximum sustainable yield (MSY = 5.88 T), indicating
unsustainable harvesting and high fishing pressure. This excessive harvest coupled with high
exploitation ratios (E yr−1) ranging from 0.65 to 0.84 directed toward the larger length-groups
(5.65–8.45 cm, SH) would imperil the breeding stock and lead it to recruitment overfishing. Using
Thompson and Bell model, the effect of imposing minimum size (6.35 cm shell height) restriction
shows an increase of 7.62% and 20.45% to the annual yield and biomass, respectively which is
a positive implication of this strategy.
The Eel Fishery in Tributaries Along Lagonoy Gulf: Implications
for Management and Conservation
Plutomeo M. Nieves1,*, Antonino B. Mendoza Jr.1 , Raul G. Bradecina2 , John Christopher C.
Nolial1 , Niño C. Celestial1 , Satoshi Kubota3 , and Katrina L. Canon3
Abstract
This study provides a discussion of the eel fishery in the tributaries and rivers along
Lagonoy Gulf primarily to formulate management and conservation strategies supportive of the
economic potentials and sustainability of the resources. Data collection employed key informant
interview and focus group discussion to collect fishery-based data together with the collection of
300 samples per month. Caudal cutaneous pigmentation method was used in species
identification. GIS map was prepared to identify the potential eel habitats. The species
composition across the study area include: Anguilla marmorata (89.80%), A. bicolor pacifica
(10.10%) and A. japonica (0.10%). The wide-distribution of A. marmorata could be explained by
the fastness of leptocephalus metamorphosis. Two gears type were identified: modified fyke net
was mainly used in glass eel collection while the remaining gears for adult eel. Post-harvest
practices are similar to milkfish. Finding showed no clear indication of the status and trend of the
fishery. Supply and value chain is limited to 30 collectors, 93 fishers and 5 traders, their number
increases proportionately in-line with increasing catch. Estimated annual production for glass eel
is 4,626 kg - 1,386 kg valued at ₱9.4M to ₱12.67M and about 325MT to 81.3 MT adult eel annually
valued at ₱23.3M to ₱6.6M. Policies and strategies supportive of economic potential of eel
resources are recommended alongside the development of sustainable management
interventions to sustain the fishery. Further study on species identification using a combination of
morphological and molecular technique is recommended.
Keywords: modified fyke net, ichthyotoxic plant, caudal cutaneous pigmentation, and glass eel
Factors Linking Declining Reef Health Ecosystem to
Poverty in Lagonoy Gulf, Eastern Bicol, Philippines
Antonino B. Mendoza, Jr. (Corresponding author); Plutomeo M. Nieves ; Michael C. Borejon
Abstract
This paper provided likely linkage between poverty and reef health status in Lagonoy Gulf.
It showed that fishers are poor as reflected by their weekly income ranging from PhP 2,500.00 to
to <500.00 averaging PhP 1,214.00 which is way below the PhP 3,596 week-1 poverty threshold
for Bicol Region. Population density in coastal municipalities is highest in Albay with 512 ind. km2 and least in Catanduanes with 325 ind. km-2 . Fishers are relatively ageing with mean age of
48 years and average fishing experience of 29 years. Majority only reached or finished primary
level, and only 6% reached college. Five out of six do not own boat and gears, showing financial
incapacity. Hook and lines were used by 66% of the fishers while, nets comprised 32%. Living
coral cover declined from 1993 to 2018 by almost 25%. High dependence to coastal resources,
high demand for seafood, destructive gears, lack of supplemental sources of income, low
educational background, lack of skills, low income are identified contributory factors to habitat
degradation. With the declining reef health and fish catch, fishers that are living below poverty
threshold are more likely to become poorer because the reef’s capacity to provide goods and
services is lost.
Tidal periodicity of molting in giant mud crab, Scylla serrata
(forskål, 1775)
Darwin C Biag 1, 2, *, Antonino B Mendoza Jr 2, 3, Renan U Bobiles 2, 3, Alex P Camaya 2, 3,
Skorzeny C De Jesus 2, 3 and Plutomeo M Nieves 2, 3
Abstract:
Molting is the most crucial phase in the life cycle of mangrove crabs, leading to mortality
in various culture systems. As a result of this exigency, this study was conducted to offer a cue in
molting using the tidal cycle as one of the visible events in a natural context. Monitoring was
carried out at every 1-hour interval (24 hours) day and night for 57 days to check for molting while
taking into account key environmental elements such as tidal cycles, water current speed, and
flow rate. The results showed that 70.6% of molting happened during high tide, with 93.8% of it
occurring at night and 6.3% during the day. By contrast, only 29.4% occurred during low tide,
showing a significant difference (T-test = 0.011, p < 0.05) between mean molts. Hence, the
highest molting rate (88.2%) was observed between tidal episodes between the neap and middle
cycles, with the middle tide (55.9%) occurring at 12.4±0.9 m/s, neap tide (32.4%) occurring at
16.8±2.0 m/s, and spring tide (11.8%) occurring at 9.5±1.2 m/s. Molting occurs at high tide
because crabs' rheotactic behavioral responses to incoming new water help the crab's body fill
with air and water throughout the molting process. Mangrove crabs employ their tidal periodicity
of molting as a defense strategy against potential predators and mortality, and it can be used as
a molting indicator in many culture systems.
Keywords: Tidal cycles; Water current; Molting schedule; Indicators; Mangrove crab
YEAR: 2023
Knowledge and awareness on the fishery resources of
elementary and high school students
Antonino B. Mendoza Jr 1 * , Mariel B. Bernadas 1 , Aileen B. Rances 1 , Michael C. Borejon 1 ,
Maria Luisa U. Tango 1 , Raul G. Bradecina 2
ABSTRACT
Knowledge and awareness on the natural resources among elementary and high school
students are important attributes for future resource conservation and management. However,
the enslaving features of gadgets and technologies has shifted the focus of the students away
from nature-based knowledge and has motivated the government to integrate environmental
education (EE) to the basic education programs. However, its implementation has not been
successful due to lack of teaching materials and limits on teachers’ capabilities. As such, it was
found out that knowledge of elementary, junior high school (JHS) and senior high school (SHS)
students on the native and unique natural resources of Bicol Region are almost the same, with
an average score of 40%. But intervention through the use of EE teaching materials developed
from the research publications and reports of Bicol University Tabaco Campus facultyresearchers showed that an increase of 31%, 21%, and 28% have been observed for elementary,
JHS, and SHS students, respectively. However, a significant difference (p<0.05) was observed
between high schoolers from urban setting as compared to the upland and island students with
regards to the prior knowledge on naturalresources, on the other hand, significant change was
also observed in the increase of knowledge in upland (30% increase for JHS, and 42% for SHS)
and island students (22% and 27% for JHS and SHS, respectively) as compared to the urban
students (12% and 17% for JHS and SHS, respectively). No differences were observed for the
elementary students across sites. Several factors were identified to influence knowledge and
awareness of students such as, access to internet and mass media, exposure to local situations
and prior knowledge, and influence of family and community. Overall, knowledge and awareness
of elementary and high school students on the local natural resources are relatively low but
existence of local and relevant EE learning materials can help increase them. It is therefore,
recommended that EE through the KADUNUNG program should be institutionalized to improve
knowledge and awareness of students in Tabaco City.
Keywords: KADUNUNG, environmental education, DepEd Tabaco, learning material
Community Structure of Herbivore Reef Fishes in Lagonoy Gulf,
Eastern Philippines
Antonino B. Mendoza
Abstract
Reef herbivory is a critical ecological process that can control community structure
in a reef and can determine recovery potential; therefore, herbivores are an important
input in coral reef resiliency. In Lagonoy Gulf, herbivorous reef fishes were surveyed from
22 sampling stations with 93 transects of which 149 species belonging to 14 families were
recorded. Although no differences between stations were detected among their
biomasses, sizes, abundance and number of species; clustering of stations showed
significant differences between clusters. Functional grouping suggests that almost all
reefs experienced overfishing as average biomasses were relatively low, with grazers
weighing only 112 kg ha-1, scrapers with 56 kg ha-1, browsers 14 kg ha-1, and territorial
damselfish 70 kg ha-1. Marine Protected Areas (MPA) were noted to have no impact on
reefs’ herbivore community structure since it was almost similar with outside-MPAs and
non-MPAs, but then, MPAs have higher overall values than the two other areas.
Generally, presence of herbivore fishes in Lagonoy Gulf is a good indicator of the reef’s
potential recovery before and after a disturbance event. Furthermore, the diverse
herbivore population of the Gulf enhances functional redundancy.