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Establishing the impacts of freshwater
aquaculture in tropical Asia: the potential role of
palaeolimnology
Kenoses Legaspi
1
, A. Y. Annie Lau
2
, Phil Jordan
3
, Anson Mackay
4
,
Suzanne Mcgowan
5,6
, Gayle Mcglynn
7
, Susana Baldia
8,9
,
Rey Donne Papa
8,9
and David Taylor
2
Freshwater aquaculture is an important source of protein worldwide. Over-exploitation of fisheries can, however,
add severely to pressures on ecosystem functioning and services. In Southeast Asia, aquaculture in freshwater lakes
contributes significantly to the economy and to reductions in poverty and nutritional insecurity. However,
overstocking and excessive feeding of fish can lead to a degradation of affected water bodies, manifest as eutrophi-
cation, toxic algal blooms, losses of biodiversity and amenity, anoxia and, in extreme cases, collapse of fisheries.
Projected increased warming and storminess associated with global climate change are likely to magnify existing
problems. Matching levels of aquaculture production with ecological carrying capacity is therefore likely to become
increasingly challenging, requiring levels of data and understanding that are rarely available, a problem that is im-
possible to rectify in the short term using standard limnological approaches. This paper reviews the development of
freshwater aquaculture in the Philippines, associated environmental impacts, and relevant environmental regula-
tions and regulatory bodies. The potential role of palaeolimnology, a science that is relatively under-utilised in
the tropics generally and in tropical Asia in particular, in complementing extant datasets, including monitoring re-
cords, is highlighted through reference to a preliminary study at Lake Mohicap. Lake Mohicap currently supports
aquaculture and is one of a cluster of seven volcanic crater lakes on Luzon, the largest of the archipelago of islands
forming the Philippines.
Key words Philippines; palaeolimnology; eutrophication; aquaculture
1
Graduate School, University of Santo Tomas, Manila 1015, Philippines
2
Department of Geography, National University of Singapore, 119260, Singapore
3
School of Environmental Sciences, University of Ulster, BT52 1SA, UK
4
Environmental Change Research Centre, Department of Geography, University College London, London WC1E 6BT, UK
5
School of Geography, University of Nottingham Malaysia Campus, 43500 Semenyih, Selangor, Malaysia
6
School of Geography, University of Nottingham, University Park, Nottingham NG72RD, UK
7
Department of Geography, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
8
Department of Biological Sciences, University of Santo Tomas, Manila 1015, Philippines
9
Graduate School and Research Center for the Natural and Applied Sciences, University of Santo Tomas, Manila 1015, Philippines
Email: reypaps@yahoo.com; rspapa@mnl.ust.edu.ph
Revised manuscript received 13 October 2015
Introduction
Globally, more than two billion people are exposed to
diseases linked to water supplies, through the consump-
tion of polluted drinking water or food that has been
contaminated by water-borne pollutants (Gleick 2011;
Prüss-Ustün et al. 2014). The problem is acute in parts
of Asia, where a combination of factors has severely
jeopardised water resources (Chellaney 2011) and the
ecosystem services provided (Clausen and York 2008).
The challenge of meeting the demand for aquatic eco-
system services in Asia, where abstraction rates are al-
ready the highest in the world, is likely to increase in
coming years, owing to projected changes in climate and
consumption, and the cumulative and combined effects
of pollution (Evans et al. 2012; Vorosmarty et al. 2013).
Environmental pollution is a major problem through-
out Asia (Evans et al. 2012), as is evident from an
escalation in accounts of the effects of pollution, such
as harmful algal blooms (Glibert 2013), toxic air
The information, practices and views in this article are those of the author(s) and do not necessarily reflect the opinion of the Royal Geographical
Society (with IBG).ISSN 2054-4049 Citation: 2015, 2, 148–163 doi: 10.1002/geo2.13 © 2015 The Authors. Geo: Geography and Environment
published by John Wiley & Sons Ltd and the Royal Geographical Society (with the Institute of British Geographers).
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and
distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are
made.
Open Access
(Zhou et al. 2015) and contaminated soils (Zhao et al.
2015). Long-term monitoring of ecological systems in
tropical Asia has tended to focus on rainforests and
coral reefs: relatively little research has been devoted
to understanding the ecological and chemical status
and functioning of freshwater bodies (Biswas and
Seetharam 2008). For example, of the lakes included
in the International Long Term Ecological Research
(ILTER) network, set up in 1993 to monitor environmen-
tal change impacts on ecological and socioeconomic sys-
tems, only three are located in Asia (Donghu and Taihu
in China and Yuan-Yang in Taiwan). Both Taihu and
Yuan-Yang also feature in the Global Lake Ecological
Observatory Network (GLEON), along with Lake
Soyang (South Korea). The four lakes featured are all
subtropical, while Lake Soyang –which is a reservoir –
formed behind a dam in the early 1970s. Lakes in tropical
Asia fare are similarly under-represented in the
GloboLakes(2015) database, which was set up to provide
a basis for investigating the state of lakes and their re-
sponse to climatic and other environmental drivers of
change using a combination of in situ and remotely sensed
data: of a total of 991 lakes in the database, only 12
(i.e. less than 1.5%) are located in tropical Asia. There-
fore, a shortage of data constrains the design of effective
measures for reducing or reversing aquatic degradation
and provides for only the most fragile and superficial of
platforms upon which to base assessments of the extent
of human perturbation and the effects of pollution on lake
functioning. Detecting change or impact in freshwater
ecosystems is dependent upon being able to determine
the amplitude of natural variability, and therefore the ex-
tent by which this has been exceeded by anthropogenic
activity, and the determination of baseline (or pre-impact)
conditions. Defining this envelope of variability can also
help to identify when ecosystem thresholds or carrying
capacities have been exceeded (Dalton et al. 2009).
The archipelago of islands comprising the Philippines
is relatively lake-rich when compared with other parts
of tropical Asia (69 freshwater lakes). Many of the
lakes support fish farms that, although important eco-
nomically and for food security, can be major sources
of pollution (Edwards 2015). In an effort to mitigate
negative environmental impacts arising from aquacul-
ture and other water-based or focused activities, the
Republic Act (RA) No. 9275 (The Philippine Clean
Water Act (CWA) of 2004) was implemented. The aims
of the CWA include the restoration and rehabilitation of
impacted ecosystems, the latter in part through the pro-
motion and acceleration of relevant research (DENR-
EMB 2014). However, implementation of the CWA has
been compromised by a dearth of long-term monitoring
data and relevant ecological studies. Indeed, lake-based
studies are rare in the Philippines, beyond a few basic
ecological surveys and research aimed at improving
aquaculture productivity (Papa and Mamaril 2011).
This paper contextualises concerns regarding the
risks to human and environmental health, and to eco-
nomic development, posed by the rapid expansion of
lake-based aquaculture and associated pollution in the
Philippines, and reviews the regulatory response. Lake
Mohicap, one of the seven crater lakes of San Pablo,
Laguna, on the island of Luzon, is a particular focus
of the paper. The island of Luzon is a centre for lake-
based aquaculture: the cluster of crater lakes that in-
cludes Lake Mohicap is currently associated with a high
Figure 1 Aquaculture, pollution and cyanobacteria (Microcystis spp.) blooms at the Seven Crater Lakes of San Pablo
Source: Photo by D. Taylor, May 2014
149Establishing the impacts of freshwater aquaculture in tropical Asia
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
© 2015 The Authors. Geo: Geography and Environment published by John Wiley & Sons Ltd and the Royal Geographical Society (with the
Institute of British Geographers)
intensity of fish farming that has greatly contributed to
the deterioration of water quality in the lakes (Figure 1).
The results of a preliminary palaeolimnological analysis
of a sediment core from Lake Mohicap are discussed in
the context of aquaculture and relatively recent changes
in sedimentation and water quality.
Aquaculture and water quality
Aquaculture is currently the fastest growing sector in live-
stock production globally (Sampels 2014), and fish protein
is important for the nutritional security of a substantial
proportion of the world’s population (Kawarzuka and
Béné 2011). Aquaculture worldwide produced over 58 mil-
lion tonnes of fish products and generated an estimated
US$144.4 billion in 2012, growing at an average rate annu-
ally of over 12% between 1976 and 2012 (Krause et al.
2015). Asian countries account for by far the largest share
of production –well over 80% according to the FAO
(2014). The total quantity of fish from aquaculture is
projected to reach 93.6 million tonnes by 2030, with China
and Southeast Asian countries the main producers (World
Bank 2013). Aquaculture also provides employment and a
reliable income, often in communities where both are
otherwise difficult to secure (Pant et al. 2014). Historically
the number of people employed in fisheries has grown
more quickly than global population, with employment
levels in aquaculture in Asiamorethandoublingoverthe
last c. 15 years to more than 18 million, or greater than 95%
of the total employed in the industry globally (FAO 2014).
Pollution associated with aquaculture is a significant
problem, but economic and social effects are also a con-
cern. In Asia, productivity per fish farmer is lower than
in any other region of the world, being c. 60% of that in
Africa and only c. 5% of that in North America (FAO
2014). Moreover, doubts have emerged over the ability
of small-scale or low-technology aquaculture to act as a
basis for economic development in rural areas (Stevenson
and Irz 2009), in part because of low survival rates among
farmed fish, a reliance on labour from unpaid family
members, and pressure to export nutritious produce
beyond the local area (Gehab et al. 2008; Jolly et al. 2009).
Although relevant empirical studies are few, particularly
with regard to freshwater aquaculture, there is evidence
that fish farming can have negative social effects, particu-
larly among the most vulnerable communities (Irz et al.
2007). A paradox exists: while the benefits of expanded
aquaculture may have helped alleviate poverty among
some communities, the costs of fish farming in terms of re-
sources consumed (including land for fishponds), disrupted
ecosystem functioning and reduced ecosystem services
(Figure 2), and the risks posed to health through farmed
fish contaminated by harmful pollutants entering the
food chain, may be more widely felt (Törnqvist et al. 2011).
Figure 2 Schematic representation of fish farming and its environmental impact
150 Kenoses Legaspi et al.
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
© 2015 The Authors. Geo: Geography and Environment published by John Wiley & Sons Ltd and the Royal Geographical Society (with the
Institute of British Geographers)
In the Philippines, a presidential decree (PD) by
President Marcos in 1973 (PD 43-A) targeting the con-
struction of small fishponds, later consolidated with
other related decrees into PD 704 (1975), sanctioned
an accelerated development of fisheries resources. A
boost in production from fish farms ensued. Production
of farmed fish has continued to climb, despite increased
intensity of aquaculture being implicated as a cause of
periodic mass die-offs of farmed fish (Jacinto 2011;
Magcale-Macandog et al. 2014), growing by more than
10% between 2007 and 2012 (DA-BFAR 2012). Tilapia
(Oreochromis niloticus) and milkfish (Chanos chanos)
are the most important farmed fish in, respectively,
lakes/ponds and brackish/marine waters (ADB 1996;
Cruz 2007; FAO 2009). This rapid rate of development
has not been without its environmental costs, however.
Environmental degradation linked to fish farming, in
the form of clearance of vegetation to construct fish-
ponds, contamination of drinking water supplies and
the food chain (for example, by environmental hor-
mones), eutrophication (due to high densities of fish
and low feed conversion ratios), introduced pathogens
and exotic invasive species, potentially undermines the
long-term sustainability of fish farming. In such situa-
tions, aquaculture may end up reducing resilience, par-
ticularly among the most vulnerable members of a
community (Troell et al. 2014). Negative environmental
impacts associated with aquaculture are set to deepen
in the future, in the absence of mitigating and adaptive
measures, as a result of climate change-driven warmer
waters, increased hypoxia, raised pollutant toxicities
and rates of bioaccumulation of toxins in farmed fish,
and the emergence or re-emergence of pathogens
(Ficke et al. 2007; De Silva and Soto 2009; Porter
et al. 2014).
Of 69 freshwater lakes in the Philippines, 36 are
classed in accordance with criteria laid out in DENR
Administrative Order No. 34, Series of 1990 (Guerrero
1999) into three categories: good lakes are regarded as
having water quality within acceptable standards and no
evidence of stress from overexploitation of fisheries;
threatened lakes show moderate pollution, sedimenta-
tion and ecological stress; while critically endangered
lakes are associated with heavy pollution and over-
fishing. Twenty-seven of the lakes classified are associ-
ated with water quality problems linked to
aquaculture. Laguna de Bay –lake number 18 in Table I
(Figure 3) –is a prime if perhaps an extreme example.
The lake provides a wide range of ecosystem services
to central Luzon, including to residents of the capital
Metropolitan Manila. Overexploitation and unsustain-
able aquaculture practices have contributed to a
marked decline in water quality, biodiversity, and pro-
ductivity (Zafaralla et al. 2002; Santos-Borja and
Nepomuceno 2006). Laguna de Bay has also been
categorised as a critically endangered lake, despite
being part of a candidate key biodiversity area (CKBA).
Key biodiversity areas (KBAs) build upon the National
Integrated Protected Areas System (NIPAS), were set
up in the early 1990s under the administration of the
Department of Environment and Natural Resources
(DENR), and aim to ensure the landscape-based con-
servation of globally important biodiversity. Areas that
are suspected of supporting globally important biodi-
versity, but for which there is no conclusive supporting
data, are designated CKBAs and are regarded as prior-
ities for research in the Philippines. A perhaps less
extreme and therefore more representative example of
the aquatic impacts of aquaculture is provided by
several of the lakes grouped as the Seven Crater Lakes
of San Pablo, which also form part of a CKBA and are
associated with high levels of pollution and occasional
mass die-offs of fish (Global Nature Fund 2015). Fish
farming and human settlement are the main sources
of pollution.
Towards a more ecologically sustainable
lake-based aquaculture: institutional and
regulatory responses to declining water
quality in the Philippines
Legislation implemented in different countries around
the world in response to a widespread degradation of
water bodies has tended to target levels of a relatively
narrow range of pollutants. Only rarely do water pollu-
tion regulations adopt a whole catchment approach,
cover all forms of water bodies and seek to put in place
mechanisms that will enable restoration or rehabilita-
tion of damaged ecosystems. The Water Framework
Directive (WFD) (2000) is an example of such all-
encompassing legislation, requiring that all water
bodies in European Union (EU) member states reach
at least ‘good’water quality status, or show little or no
human impact, by the end of the first implementation
period (2015) (Kirilova et al. 2010) or six-year targeted
cycles thereafter. However, development and effective
implementation of environmental legislation require
not only strong political will and buy-in from the main
interested parties, but also the availability of relevant
data (including datasets from long-term monitoring
studies) and a high level of understanding of the pres-
sures on water bodies and their effects, and range of
possible appropriate responses (Rola et al. 2004).
In the Philippines, growing concerns regarding the
overexploitation of natural resources and environmental
degradation allied to increased parliamentary democracy
provided the context for the creation in 1987 of the
DENR (BFAR-PHILMINAQ 2007). The Environmental
Management Bureau (EMB), the enforcement arm of
the DENR, is responsible inter alia for regulating the en-
vironment through close monitoring sources of pollution
and mitigate its effects to health and environment
151Establishing the impacts of freshwater aquaculture in tropical Asia
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
© 2015 The Authors. Geo: Geography and Environment published by John Wiley & Sons Ltd and the Royal Geographical Society (with the
Institute of British Geographers)
Table I The 69 major freshwater lakes in the Philippines
General
area of Philippines Lake # Lake name Region/province Coordinates (N, E)
Depth
(m)
Governing
bodies
Protective
status Class
Condition of the
lake
Northern and Western
Philippines
1 Alindayat* III, Zambales 15° 36’38", 119° 56’34" DD BFAR NP NC T
2 Bangalau II, Cagayan 18° 14’57.76", 121° 54’13.37" 2.5 NS NP NC NS
3 Baao V, Camarines Sur 13° 27’49.5138", 123° 18’
57.5388"
DD NS NP NC NS
4 Bato* V, Camarines Sur 13° 19’54.9984”, 123° 21’
32.0004”
4.5 DENR-BMB NIPAS B T
5 Buhi* V, Camarines Sur 13° 27’24.9984”, 123° 30’
51.0012”
7BFAR NP B T
6 Bulusan V, Sorsogon 12°45’41.688", 124° 5’29.781" DD DENR NIPAS NC NS
7 Bunot * IV, Laguna 14° 4’59.9982”, 121° 20’
59.9994”
23 LLDA-
BFARMC
CKBA NC T
8 Cabalangan* II, Cagayan 18° 10’59.99", 121° 45’0" DD NS NP NC NS
9 Calibato* IV, Laguna 14° 6’15.0012”, 121° 22’
37.9992”
156 LLDA-
BFARMC
CKBA NC T
10 Calig II, Cagayan 18° 12’29.88", 121° 49’18.12" DD NS NP NC NS
11 Caliraya IV, Laguna 14° 18’11.3178”DD NS NS NC NS
12 Caluangan* IV, Oriental Mindoro 13° 22’00.0120", 121° 07’
59.9880"
DD BFAR NIPAS NC T
13 Cansiritan II, Cagayan 17° 54’7.56”, 121° 42’2.71”DD NS NP NC NS
14 Cassily II, Cagayan 17° 40’19”, 121° 30’48”DD NS NP NC NS
15 Danao* V, Camarines Sur 13° 21’33”, 123° 34’24”DD NS NP NC NS
16 Danum CAR 17° 5’39.41", 120°53’4.97" DD NS NP NC NS
17 Kayangan IV, Palawan 11°57’12.40", 120°13’24.62" DD NS NP NC NS
18 Laguna de Bay* IV, Laguna, Metro Manila and
Rizal
14° 23’7.6812", 121° 17’
4.9698"
2.8 LLDA-
BFARMC
CKBA NC CE
19 Lumot-
Mahipon*
IV, Laguna 14° 15’20.934", 121° 32’
49.0884”
DD NS NS NC NS
20 Malbato IV, Palawan 12° 01’48.1008", 120° 06’
59.9004"
DD NS NP NC NS
21 Manguao IV, Palawan 10° 46’00.1200", 119° 33’
00.0000"
DD DENR-BMB NIPAS-KBA NC G
22 Mapanuepe III, Zambales 14° 59’2.22", 120° 17’40.33" DD NS NP NC NS
23 Mohicap* IV, Laguna 14° 7’22.53”, 121° 20’2.4318”30
m
LLDA-
BFARMC
CKBA NC T
24 Nagatutuan II, Cagayan 18° 3’46.36”, 121° 39’47.52”DD NS NP NC NS
25 Nalbuan II, Cagayan 18° 13’26”, 121° 46’51”DD NS NP NC NS
26 Naujan* IV, Oriental Mindoro 13° 10’10.9992”, 121° 20’
54.9996”
19 DENR-PAWB NIPAS B G
27 Paitan* III, Nueva Ecija 15° 49’59.99" ,120° 43’59.99" DD NS NP NC T
152 Kenoses Legaspi et al.
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
© 2015 The Authors. Geo: Geography and Environment published by John Wiley & Sons Ltd and the Royal Geographical Society (with the
Institute of British Geographers)
28 Palakpakin* IV, Laguna 14° 6’40.2798”, 121° 20’
19.8378”
8 LLDA-
BFARMC
CKBA NC T
29 Pandin* IV, Laguna 14° 7’0.0006”, 121° 22’
0.0012”
62 LLDA-
BFARMC
CKBA NC T
30 Pantabangan III, Nueva Ecija 15° 48’59.58”, 121° 8’58.31”DD NS NP NC NS
31 Paoay* I, Ilocos Norte 18° 7’16.2474”, 120° 32’
25.728”
3-5 DENR-PAMB NIPAS NC T
32 Pinatubo crater
lake
III, Zambales 14° 59’2.22”, 120° 17’40.33”DD NS NP NC NS
33 Sampaloc* IV, Laguna 18° 7’16.2474”, 120° 32’
25.728”
25 LLDA-
BFARMC
CKBA NC T
34 Taal* IV, Batangas 13° 56’54.999”, 121° 0’
26.9994”
90 PAWB-PPCT NIPAS-KBA NC T
35 Tadlak* IV, Laguna 14° 10’57.3528”, 121° 12’
23.3244”
58 LLDA-
BFARMC
CKBA NC NS
36 Tambo III, Tarlac 15° 17’45.87”, 120° 22’19.17”DD NS NP NC NS
37 Yambo* IV, Laguna 14° 11’66.667”, 121° 36’
66.667”
40
m
LLDA-
BFARMC
CKBA NC T
Central Philippines 38 Balinsasayaw* VII, Negros Oriental 9° 21’59.1042”, 123° 9’
18.9036”
134
m
DENR-PAWB NP NC G
39 Bito* VIII, Leyte 10° 47’19”, 124° 58’49”DD NS NP NC T
40 Danao* VII, Cebu 10° 40’35.274”, 124° 20’
34.299”
0.91–
54.9
NS NP NC G
41 Danao* VIII, Leyte 10° 52’5.001”, 124° 51’
20.9988”
DD NS NP A T
42 Danao* VII, Negros Oriental 9° 21’2.001”, 123° 10’
59.9988”
DD NS NP NP NS
43 Kabalin-an* VII, Negros Oriental 9° 21’11”, 123° 9’45”DD NS NP NP NS
44 Lanao VII, Calibao Island - Bohol 9° 52’47”, 123° 45’51”DD NS NP A T
45 Mantohod* VII, Negros Oriental 10° 10’60”, 123° 13’1”DD NS NP NC G
Southern Philippines 46 Apo X, Bukidnon 7° 52’50.10”, 125° 0’23.25”DD NS NP NC NS
47 Bulut XII, North Cotabato 7° 18’09.0000”, 124° 17’
35.0160”
DD NS NP NC G
48 Blingkong XII, North Cotabato 6° 39’0”, 124° 55’0.02”DD NS NP NC G
49 Buluan ARMM, Maguindanao 6° 38’42”, 124° 49’38”DD NS NP NC G
50 Butig ARMM, Lanao del Sur 7° 44’2”, 124° 17’27”DD NS NP NC G
51 Danao X, Misamis Oriental 8° 39’48.9996”, 124° 46’
48.2988”
DD NS NP NC NS
52 Dapao ARMM, Lanao del Sur 7° 47’12”, 124° 2’36”DD NS NP NC G
53 Gumaod X, Misamis Oriental 8° 39’7.14”, 124° 48’24.74”DD NS NP NC NS
54 Labas XII, North Cotabato 7° 15’00.0000”, 124° 30’
00.0000”
DD NS NP NC G
55 Lahit XII, South Cotabato 6° 15’6.9978”, 124° 42’54”DD NS NP NC NS
(Continues)
153Establishing the impacts of freshwater aquaculture in tropical Asia
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
© 2015 The Authors. Geo: Geography and Environment published by John Wiley & Sons Ltd and the Royal Geographical Society (with the
Institute of British Geographers)
Table I. (Continued)
General
area of Philippines Lake # Lake name Region/province Coordinates (N, E)
Depth
(m)
Governing
bodies
Protective
status Class
Condition of the
lake
56 Lanao* ARMM, Lanao del Sur 7° 51’00.0000”, 124° 15’
00.0000”
DD DENR-BMB NIPAS-KBA NC T
57 Mainit* XIII, Surigao del Norte-
Agusan
9° 26’2.0004”, 125° 31’
59.9982”
128 LMDA NIPAS-
CKBA
AT
58 Malinao XII, North Cotabato 7° 16’39.0000”, 124° 19’
06.9600”
DD NS NP NC G
59 Maughan XII, South Cotabato 6° 6’5”, 124° 53’20”DD NS NP NC T
60 Napalit X, Bukidnon 7° 52’5.59”, 124° 47’3.97”DD NS NP NC NS
61 Nunungan X, Lanao del Norte 7° 49’21”, 123° 57’19”DD NS NP NC G
62 Pagusi XIII, Agusan 9° 18’0”, 125° 33’0.01”DD NS NP NC G
63 Pinamaloy X, Bukidnon 7° 40’16.13”, 124° 59’58.35”DD NS NP NC NS
64 Pulangi X, Bukidnon 7° 48’27.13”, 125° 1’59.69”DD NS NP NC NS
65 Putian ARMM, Lanao del Sur 7° 48’24.012”, 124 34’3”DD NS NP NC T
66 Sebu XII, South Cotabato 6° 13’27.0006”, 124° 42’
11.9988”
5 NS NP B/C NS
67 Siloton XII, South Cotabato 6° 13’33.1896”, 124° 43’
51.657”
DD NS NP NC NS
68 Tutay X, Bukidnon 7° 40’00.8004”, 125° 01’
40.1988”
DD NS NP NC NS
69 Wood IX, Zambonga del Sur 7° 50’40”, 123° 9’54”DD NS NP NC T
Source: Information from Guerrero (1999), Papa et al. (2012), Pascual et al. (2014) and DENR-EMB (2014)
Abbreviations: *Lakes with aquaculture; A, class A, B, class B, C, class C (see Table II); CE, critically endangered lakes (are associated with heavy pollution and overfishing); CKBA, candidate key biodiversity
area; DD, data deficient; G, good conditioned lakes (having water quality within acceptable standards and no evidence of stress from overexploitation of fisheries); KBA, key biodiversity area;
m
, max; NC, not classified; NIPAS, National Integrated Protected Areas System; NP, not protected; NS, not specified; T, threatened lakes (show moderate pollution, sedimentation and ecological stress).
154 Kenoses Legaspi et al.
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
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Institute of British Geographers)
Figure 3 Philippine map showing the 69 freshwater lakes (information from Guerrero 1999; Papa et al. 2012; DENR-
EMB 2014; Pascual et al. 2014). For information on their protective status and water classification, see Table I
155Establishing the impacts of freshwater aquaculture in tropical Asia
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
© 2015 The Authors. Geo: Geography and Environment published by John Wiley & Sons Ltd and the Royal Geographical Society (with the
Institute of British Geographers)
(White 2009) using DENR Administrative Orders
(DAOs) (Figure 4). In addition to the DENR, aquacul-
ture activities are regulated through Fisheries Adminis-
trative Orders (FAOs) and the RA No. 8550 (Fisheries
Code of 1998) which are administered by the Bureau of
Fisheries and Aquatic Resources (BFAR), the govern-
ment agency responsible for overseeing the country’s
fisheries and aquatic resources, and under the Depart-
ment of Agriculture (Guerrero 1999; DA 2012).
Activities of the BFAR from the 1970s brought sig-
nificant developments to fisheries in the Philippines
and led the establishment of lake-based aquaculture
management programs (BFAR-PHILMINAQ 2007).
The campaign to improve lake management and ad-
dress problems of declining water quality intensified
on the island of Luzon during the 1990s upon the for-
mation of specialised management bodies for Laguna
de Bay, the Seven Crater Lakes of San Pablo, and Lake
Taal. For Laguna de Bay, the proclamation of RA
No. 4850 in 1996 paved the way for the establishment
of the Laguna Lake Development Authority (LLDA),
under the supervision of the DENR, and implemented
Figure 4 Schematic diagram of the key policymakers in the Philippines for water and environmental management (Makil
1984; AFMA 2004; COA 2014; Rola et al. 2004; DA 2012; FTTC-AP 2013; DENR-EMB 2014; DENR 2015; LLDA 2015)
156 Kenoses Legaspi et al.
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
© 2015 The Authors. Geo: Geography and Environment published by John Wiley & Sons Ltd and the Royal Geographical Society (with the
Institute of British Geographers)
an integrated lake basin management approach to the
management of the lake that included a levying of fees
on those responsible for discharging effluents to the
lake in proportion to the level of pollutants (Santos-
Borja and Nepomuceno 2006; LLDA 2015). Aside
from Laguna de Bay, LLDA has also taken on the re-
sponsibility for managing the Seven Crater Lakes of
San Pablo with the assistance from the San Pablo City
Government and non-governmental organisations
(Santos-Borja 1997; Zafaralla et al. 2002; Santos-Borja
and Nepomuceno 2006). Lake Taal was previously un-
der the jurisdiction of the Presidential Commission
on Tagaytay-Taal (PCTT), created under Executive
Order (EO) No. 84 in 1993 (TVPL-PAMB 2009;
COA 2014). Implementation of FAOs allowed for
establishment of a fish sanctuary in Lake Taal and the
prohibition of certain fishing technologies. In order to
facilitate management, aquaculture was restricted to par-
ticular parts of the lake (Santos-Borja and Nepomuceno
2006). Since 2008, a management plan for Lake Taal was
put into effect, and mandated new regulations for fisher-
ies, such as limiting the number of fish cages in the
aquaculture sites, introducing new methods of licensing
and taxing fish farms, and managing effluent inputs
(TVPL-PAMB 2009).
Implementation of the CWA (2004), and its Imple-
menting Rules and Regulations (IRR) by the EMB
sought to minimise human impacts and to facilitate im-
proved understanding of aquatic ecosystems as a basis
for their rehabilitation, restoration and protection
(DENR-EMB 2014) using the water standard parame-
ters listed in DENR Administrative Order (DAO)
Series No. 34 of 1990. The water standard parameters
provide a baseline against which future changes in wa-
ter quality, including those arising from the implemen-
tation of measures aimed at curbing pollution inputs,
can be assessed. Implementation followed on from
RA No. 7160 (Local Government Code of 1991), RA
No. 8435 (Agriculture and Fisheries Modernisation
Act of 1997) and RA 8550 (Fisheries Code of 1998)
(AFMA 2004; DA 2012; DENR 2015). The 27 lakes
supporting aquaculture mentioned previously are
among the 69 freshwater lakes monitored as part of im-
plementation of the CWA (Tables I and II). These
freshwater lakes are classed into one of five categories,
according to their use (AA, A, B, C and D), with AA
and A grouping those that are used for drinking water
supplies, while B, C and D represent those that are pri-
marily used for recreation, fisheries and agriculture/
irrigation/industrial purposes, respectively. In total, re-
gion IV-A to the south and east of Metropolitan Manila
in the central part of the island of Luzon has the largest
number of water bodies, mainly composed of principal
rivers, ponds, streams and lakes, and are (67) classified
under this system (DENR-EMB 2014). However, to
date, lentic (lake/pond) environments have received rel-
atively little attention, with the focus largely being on
rivers: more than 75% of inland water bodies classified
under the CWA are lotic (flowing water) ecosystems
(Table II).
Both DENR and the National Water Resources
Board oversee implementation of the CWA. Actual re-
sponsibilities for regulation, however, are divided
among several institutions, such as government-owned
and -controlled corporations and local government
units (LGUs) of cities, provincial, and municipal sectors
under RA No. 7160 (DENR-EMB 2014; DENR 2015).
Problems over implementation of the CWA and associ-
ated regulations have been attributed to a lack of coher-
ence and coordination between the various organisations
with regulatory responsibilities (Rola et al. 2004). For
instance, DENR has no explicit links to other local
government units under its jurisdiction, such as the
Forest Management Bureau which is responsible for
management of catchment forests under the PD No. 705
(The Revised Forest Code of the Philippines of 1975)
Table II Classification and usage of inland water bodies (DENR Administrative Order No. 34, Series of 1990)
For inland water bodies
Classification
Number of classified inland water
bodies Usage
AA: public water
supply
5 Waters that require disinfection to meet the National Standards for Drinking
Water (NSDW)
A: public water
supply
234 Waters that require complete treatment to meet the NSDW
B: recreational
water
197 Waters for primary contact recreation (e.g. bathing, swimming, skin diving,
etc.)
C 333 Water for fishery production; Recreational Water Class II
a
; Industrial Water
Supply Class I
b
D 27 For agriculture, irrigation, livestock watering; Industrial Water Supply Class
II
c
a
Recreational Water Class II (used for boating and tourism purposes).
b
Industrial Water Supply Class I (used for manufacturing processes after treatment and water supply for industrial sectors).
c
Industrial Water Supply Class II (used for cooling of industrial machinery after manufacturing processes).
157Establishing the impacts of freshwater aquaculture in tropical Asia
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
© 2015 The Authors. Geo: Geography and Environment published by John Wiley & Sons Ltd and the Royal Geographical Society (with the
Institute of British Geographers)
(Makil 1984; Rola et al. 2004). Problems also exist in the
crucial activity of monitoring water quality, where there
is little coordination of activities or uniformity of
methodologies and standards among agencies, despite
enactment of DAO 34, and frequent calls for the con-
trary (DENR-EMB 2014).
Improving the long-term prospects of aquaculture in
the Philippines requires an integrative approach to
management, extending beyond the fish pond to in-
clude broader considerations concerning social inequal-
ities, access to resources and environmental quality
(Costa-Pierce 2010; FAO 2010) and avoiding degrada-
tion of ecosystem function and services beyond their re-
silience. At the local level, attempts have been made to
incorporate the fundamental principles of ecologically
more sustainable forms of aquaculture in the manage-
ment plans of bodies such as the LLDA. One limiting
factor, however, has been a dearth of relevant scientific
data (Santos-Borja and Nepomuceno 2006). Despite
scientific advancements in recent decades, limnological
research and understanding in the Philippines remains
relatively poorly funded and developed, and has pri-
marily focused on increasing levels of aquatic produc-
tivity (Papa and Mamaril 2011), with a much smaller
number of studies examining the socio-economics of
fish farming (e.g. Krause et al. 2015). By comparison,
relatively little research has been carried out on varia-
tions in water quality over time, and the levels of aqua-
culture and other activities that a water body might be
able to support without long-term damage to ecosystem
status and functioning. Moreover, because of a shortage
of long time-series of monitoring data, little is known re-
garding the extent to which aquatic conditions may have
been modified by recent human activity. By providing
information that enhances ecological understanding, re-
search on long-term variations in (and drivers of) water
quality can support decisionmaking and facilitate a more
ecologically sustainable approach to lake management
(Sayer et al. 2012; Spruijt et al. 2014).
Palaeolimnological and limnological
research on Lake Mohicap
Lake sediments often comprise datable accumulations
of material that can be used as indicators, or proxies,
of past environmental conditions in the lake and sur-
rounding area. Palaeolimnology is the scientific study
of lake sediments and associated sources of informa-
tion: where long, complete time-series datasets are rare,
palaeolimnology has been useful as a source of informa-
tion on decadal-scale ecosystem variation and on the
extent of anthropogenic impact (Scheffer and Carpenter
2003; Parr et al. 2003; Leira et al. 2006; Bennion et al.
2011). Evidence derived from palaeolimnological tech-
niques has been used to extend or to close gaps in mon-
itoring records (Smol 2008; Battarbee et al. 2012), and
has the potential to address key questions relating to
biodiversity, conservation and ecosystem restoration
(Seddon et al. 2014). Lake sediments also preserve the
isotopic (or radiometric) basis for establishing absolute
ages for, or dates of, the reconstructed environments
and for establishing past rates of change (e.g.
14
C and
210
Pb) (Dalton et al. 2009). The following section pro-
vides a brief example of the use of palaeolimnology, in
combination with more conventional limnological
studies, aimed at improving understanding of temporal
variations in lake water quality in the Philippines over
the period that includes the more intense exploitation
of aquatic resources that characterises the last few de-
cades. The section focuses on Lake Mohicap (Figure 5),
one of the Seven Crater Lakes of San Pablo on the island
of Luzon.
Figure 5 Lake Mohicap, one of the Seven Crater Lakes of San Pablo
Source: Photo by D. Taylor, May 2014
158 Kenoses Legaspi et al.
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
© 2015 The Authors. Geo: Geography and Environment published by John Wiley & Sons Ltd and the Royal Geographical Society (with the
Institute of British Geographers)
Lake Mohicap (altitude ~99 m above sea level, sur-
face area ~229 000 m
2
, maximum depth ~30 m, lake
number 23 on Table I and Figure 3) has supported
aquaculture since the early 1970s. Tilapia is the main
species of fish farmed in the lake. The lake is consid-
ered a CKBA. Eutrophication is, however, clearly
evident –see Tables II and III, with a combination of
waste from aquaculture and from huts belonging to fish
farmers that fringe part of the lake the most likely
sources of excess nutrient inputs. Along with measure-
ments of water chemistry, limnological research has to
date largely focused on zooplankton and phytoplankton
distribution and community structure with a total of 86
taxa recorded in the lake (Papa et al. 2012; Cordero
et al. 2014; Pascual et al. 2014). The presence of
Arctodiaptomus dorsalis –an invasive calanoid species –
and rotifers (including members of the genera
Brachionus, Filinia and Keratella) suggest that the lake is
currently in an enhanced productive state (Berzins and
Pejler 1989; Papa et al. 2012).
In order to complement existing limnological data, a
95 cm long sediment core was collected from the
deepest point in Lake Mohicap using an UWITEC
gravity corer. The core was sectioned in the field and
sediment samples placed in labelled zip-lock bags and
refrigerated in the dark for subsequent laboratory anal-
ysis. Laboratory analysis focused on determining the
time period covered by the sediment core and on using
sedimentary evidence to reconstruct past variations in
water quality. A common exploratory approach to
palaeolimnological studies was adopted, involving the
investigation of sediment-based water quality proxies
in core bottom, middle and top samples, to determine
the nature of variations over the period of time re-
corded by the sediments (Smol 2008).
The time period covered by the sediment core was
estimated from a single radiocarbon (
14
C) date ob-
tained on plant macrofossils from a depth of 94–95 cm
using accelerated mass spectrometry (AMS). Radiocar-
bon analysis gave a date of 260 ± 30 years (Beta Ana-
lytic, US, Laboratory Reference number = 379190),
which when calibrated using Calib 7.1 and the IntCal13
calibration curve, yielded a median date of 1645 years
AD. The sediments in this core therefore were deposited
over the last c. 370 years. Isotopes with a shorter half-
life than
14
C(
210
Pb,
137
Cs,
241
Am) were used to establish
the rate of sedimentation in the upper-most part of the
core. Thus the sample depths of 41.5 cm, 29.5 cm and
11.5 cm were dated at, respectively, c. 1946, c. 1976 and
c. 2007. This suggests both a high rate of sedimentation
overall and an acceleration in sediment accumulation
over the last 60–70 years, with both characteristics pre-
sumably linked to catchment disturbance leading to sed-
iment inwash and increased productivity ofthe lake itself.
Given that the age of the sediment core from
Mohicap spans approximately the last 370 years, we
were able to test the hypothesis that recent changes in
trophic status of the lake have occurred, and that
changes in trophic status can be inferred from a number
of different sediment-based proxies and linked to
particular potential drivers of variations in water qual-
ity. Loss on ignition (LOI), a proxy for total organic
matter in lake sediments, was measured from 4 cm to
96 cm (Dean 1974). Percentage total organic carbon
(%TOC), percentage total nitrogen (%TN) and ratios
of carbon (δ
13
C) and nitrogen (δ
15
N) isotopes were mea-
sured in three samples from the sediment core (Meyers
and Teranes 2001). Diatom sample preparation followed
standard procedures (Battarbee 2001), and abundances
expressed as percentage relative to the total number of
valves counted in each sample. Concentrations of algal
chlorophyll and carotenoid pigments preserved in sedi-
ment samples were established using high performance
liquid chromatography (McGowan 2013) and are gener-
ally assumed to represent production of different algal
groups and, including zeaxanthin from cyanobacteria,
important bloom-forming and potentially toxic taxa
(Taranu et al. 2015). Chlorophyll a (Chl-a), which is pro-
duced by all algal groups, was used as an integrated
metric for algal production (McGowan et al. 2012).
Palaeolimnological results, summarised in Figure 6,
confirm the hypothesis that underpinned the prelimi-
nary palaeolimnological research at the lake. High rela-
tive abundances of Aulacoseira granulata towards the
Table III Summary of the physico-chemical variables data (with mean value and ranges) evaluated during the wet and
dry season in Lake Mohicap, San Pablo City, Laguna, Philippines (Cordero et al. 2014)
Physico-chemical factors Rainy season (Jun–Nov) Cool dry season (Dec–Feb) Hot dry season (Mar–May)
Rainfall
a
(mm) 417.55 (318.30–682.1) 81.1 (30–192.1) 75.23 (2–132.6)
Conductivity (us/cm) 471.52 (391.83–560.33) 469.79 (358.50–560.42) 458.83 (326.00–506.75)
pH 6.77 (5.72–7.55) 7.37 (7.12–7.57) 7.62 (7.22–7.93)
Temperature (°C) 28.3 (27.76–29.19) 26.84 (25.75–27.66) 28.64 (26.79–30.05)
Secchi disk transparency (m) 2.9 (2.04–4.11) 2.06 (1.51–3.96) 1.87 (1.38–2.42)
Dissolved oxygen (μg/l) 6.36(5.33–7.57) 4.59 (3.27–5.81) 6.39 (5.83–7.52)
Phosphates (mg/l) 1.53 (1.12–2.37) 0.97 (0.75–1.21) 1.33 (0.82–1.86)
Nitrates (mg/l) 10.1 (3.31–25.75) 3.6 (3.24–4.04) 16.08 (4.02–25.10)
a
Rainfall data are from Climate and Agromet Data Section, Climatology and Agro Meteorology Division, PAGASA-DOST, Quezon City.
159Establishing the impacts of freshwater aquaculture in tropical Asia
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
© 2015 The Authors. Geo: Geography and Environment published by John Wiley & Sons Ltd and the Royal Geographical Society (with the
Institute of British Geographers)
top of the core suggest that the lake may have become
hyper-eutrophic over the last c. 60–70 years (Alakananda
et al. 2010). Nutrient enrichment during this time is con-
firmed by high concentrations of zeaxanthin and Chl-a
pigment remains, indicating high algal production, espe-
cially from potentially bloom-forming cyanobacteria.
Diatom analysis suggests that Lake Mohicap has been
productive throughout the time period covered by the
sediment record (i.e. the past c. 370 years). However,
during the early part of the record, benthic habitats for
diatoms disappeared, resulting in a flora dominated by
only planktonic taxa. Nutrient enrichment, through its in-
fluence on enhanced productivity in the photic zone in
particular and a resultant shading of deeper habitats,
may have driven an increased prominence of planktonic
over benthic diatom taxa.
The stable isotope (
13
C and
15
N) data are intriguing.
High C:N values throughout the core suggest that the
catchment is a major source of carbon inputs to the
lake, although the proportion of carbon from algal pro-
duction shows a gradual increase (Araullo 2001; Meyers
and Teranes 2001). Changes in land use therefore likely
have an important impact on ecosystem function of
Lake Mohicap. Without more data, we can only specu-
late as to the cause of declining δ
13
C values between
the bottom and top of the core. In warm, strongly strati-
fied lakes, observed at Lake Mohicap, CO
2
exchange be-
tween the lake and the atmosphere is probably restricted
and in-lake processing of organic carbon by bacteria and
other heterotrophic organisms probably very intense
(Boehrer and Schultze 2008). δ
13
C values in the sediment
core may therefore be largely controlled by microbial
processinginthelake,butmoreworkisneededtode-
velop and test this idea (Torres et al. 2011).
Clearly, more research in Lake Mohicap and other
sites of freshwater aquaculture in the Philippines and
tropical Asia is required. That said, the preliminary
data reported here suggest that Lake Mohicap has long
been in a relatively productive state, possibly because of
local (volcanic) geological conditions or due to a pro-
longed period of human inputs from the catchment.
However, according to the sedimentary record, produc-
tivity has increased dramatically in recent decades, par-
ticularly following the introduction of caged fish-based
aquaculture in the early 1970s. Thus a realistic pre-
significant human impact baseline at Lake Mohicap
would appear to be before c. 1970. Establishing in
greater detail what those conditions entailed, and the
influence of past water quality fluctuations of more
broadly based processes, such as those occurring in
the catchment (e.g. soil erosion) and farther afield
(e.g. climate change), and/or of other in-lake changes in
physical conditions (e.g. variations in the degree of water
column mixing), ought to be a focus of further more de-
tailed palaeolimnological and limnological research.
Conclusion
Freshwater aquaculture in tropical systems has brought
economic benefits and increased food security to many
Figure 6 Multiproxy analyses of Lake Mohicap using diatom, stable isotopes, and algal pigments
160 Kenoses Legaspi et al.
ISSN 2054-4049 Citation: 2015 doi: 10.1002/geo2.13
© 2015 The Authors. Geo: Geography and Environment published by John Wiley & Sons Ltd and the Royal Geographical Society (with the
Institute of British Geographers)
communities. However, the practice is also associated
with negative environmental impacts that could jeopar-
dise future sustainability. This is particularly the case in
the Philippines, where government policies and decrees
have actively encouraged fish farming over the past four
decades or so. A substantial proportion of lakes in the
Philippines generally and the island of Luzon in partic-
ular now support aquaculture, with the lakeshores often
inhabited by local communities. Many of these lakes
provide important ecosystem services beyond the protein
and income from farmed fish and most are suffering from
excessive nutrient inputs despite a regulatory infrastruc-
ture being in place that aims to ensure environmentally
relatively benign forms of management. Also, despite
their significance (and importance as sentinels of environ-
mental change processes and impacts), almost all lakes in
the Philippines are understudied, especially when com-
paredwithloticandmarineecosystems.Tostrengthen
sustainability objectives in terms of economic develop-
ment and wider ecosystems services provision, there is a
clear need for policymakers to consider the use of scien-
tific evaluations generated by long-term monitoring stud-
ies, or adequate replacements for or complements to
these, and the application of novel techniques enabling
the restoration of degraded ecosystems.
To achieve this, and being cognisant of the lack of
long-term lake monitoring studies in the wider tropics,
palaeolimnology is proposed as a promising tool in
both applied and systematic sciences to augment
existing knowledge. For example, the application of
palaeolimnological techniques in the Lake Mohicap pi-
lot study in this review has been very useful in determin-
ing its baseline condition and the extent of change in the
past 370 years. In 2014 Lake Mohicap, along with the
other Seven Crater Lakes of San Pablo, was regarded
as threatened; the pilot study described here confirmed
the lake to have been long enriched with nutrients but
also suggested further increased pressure from nutrient
enrichment in recent decades, leading to the current
hyper-eutrophic conditions. With such diagnoses here
and across the tropics where freshwater aquaculture is
practiced or planned, additional work brings a little
closer the creation of sustainable and efficient environ-
mental policies and implementation of appropriate,
evidence-based responses that together can prevent the
further degradation of lake water quality. Moreover, the
same approach has the potential to provide information
on baseline (pre human impact conditions) that can un-
derpin the restoration of already degraded habitats and
the recovery of ecosystem services.
Acknowledgements
We would like to thank the two anonymous reviewers
for their constructive comments which helped to
improve the manuscript. The need for this review paper
emerged during a workshop and follow-up fieldwork in
the Philippines in May 2014. Thanks are due to staff
and students in the Research Center for the Natural
and Applied Sciences, University of Santo Tomas,
Manila, Philippines for hosting both the workshop and
the fieldwork, and to National University of Singapore,
Singapore, for the provision of financial support (HSS
Strategic Budget award number R-109-000-168-646).
Fieldwork in Lake Mohicap was funded by a Commis-
sion on Higher Education –Philippine Higher Educa-
tion Research Network (CHED PHERNet) grant
(Project A2) to S. Baldia and R.D. Papa. We would also
like to thank Tonolli Fund of the International Society
of Limnology for the research fund given to K.L.
Legaspi. We are grateful to Julie Swales for the assis-
tance with the pigment analyses and Atty. Ma. Paz Luna
for her comments on Figure 4. Special thanks are due to
Poonam Saksena-Taylor for producing Figure 3.
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Institute of British Geographers)
