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ECOSYSTEM SERVICES BY ARTIFICIAL REEF STRUCTURES IN MARINE ENVIRONMENT ALONG TAMIL NADU COASTS

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Abstract

Age old indigenous traditional knowledge on artificial reef has been used as the base for the development of three types of concrete artificial reef structures namely grouper module, reef fish module and well ring module, by improving their longevity and ecosystem services to suit the modern requirements so that it will serve not only as biological, biodiversity enhancement tool but also a technology to improve livelihood options and socio economic conditions of the poor traditional coastal fishers. These artificial reef structures each 70 in number have been deployed in the near shore water of Tamil Nadu coasts and their impact on the ecosystem have been studied. Maturation process of artificial reef structures, such as the biological processes, composition of sessile benthic organisms, fouling biomass, assemblage of fauna, predation on the fouling organisms, succession of different species and enhancement value of biomass have been described. Various ecosystem services provided by the artificial reef structures have been reported. This study reveal a total of 137 taxas were identified living within the artificial reef habitats and were colonized by on an average 423,948 individuals of marine organisms and had a total mean biomass of individual and colonial organisms of 5,.835g per m². Comparatively the artificial reef structures were more complex and had greater surface area than most other reef structures and consequently had a greater density of marine life. There were considerable year-to-year fluctuations in sampling unit total biomass and dominant species. The artificial reef habitats provided refuge cover for a large numbers of small and bigger fish (135.3/m²), crab (3,445.9/m²) and lobster (22.9/m²). The biomass enhancement ratios of the artificial reef structures broadly ranged between 123 and 2,195 times. Fossil fuel is saved and CO2 emission is reduced leading to a nominal contribution to the reduction if global warming and a considerable savings on fuel cost. Robust economic benefit is recorded with a short duration payback period coupled with gain in empowerment of the fisher community which enjoys a series of social benefits also. Hence this environment friendly technology is strongly recommended for implementation all along the Indian coastal waters to improve the inshore ecosystem and the livelihoods of traditional fishers and other coastal community.
ECOSYSTEM SERVICES BY ARTIFICIAL REEF STRUCTURES IN MARINE
ENVIRONMENT ALONG TAMIL NADU COASTS
H. Mohamad Kasim, G. Syda Rao, M. Rajagopalan, E. Vivekanandan, G. Mohanraj, D.
Kandasami, P. Muthiah, I. Jagdis, G. Gopakumar and S. Mohan
Central Marine Fisheries Research Institute, Kochi 682018
ABSTRACT
Age old indigenous traditional knowledge on artificial reef has been used as the base
for the development of three types of concrete artificial reef structures namely grouper
module, reef fish module and well ring module, by improving their longevity and ecosystem
services to suit the modern requirements so that it will serve not only as biological,
biodiversity enhancement tool but also a technology to improve livelihood options and socio
economic conditions of the poor traditional coastal fishers. These artificial reef structures
each 70 in number have been deployed in the near shore water of Tamil Nadu coasts and their
impact on the ecosystem have been studied. Maturation process of artificial reef structures,
such as the biological processes, composition of sessile benthic organisms, fouling biomass,
assemblage of fauna, predation on the fouling organisms, succession of different species and
enhancement value of biomass have been described. Various ecosystem services provided by
the artificial reef structures have been reported. This study reveal a total of 137 taxas were
identified living within the artificial reef habitats and were colonized by on an average
423,948 individuals of marine organisms and had a total mean biomass of individual and
colonial organisms of 5,.835g per m². Comparatively the artificial reef structures were more
complex and had greater surface area than most other reef structures and consequently had a
greater density of marine life. There were considerable year-to-year fluctuations in sampling
unit total biomass and dominant species. The artificial reef habitats provided refuge cover for
a large numbers of small and bigger fish (135.3/m²), crab (3,445.9/m²) and lobster (22.9/m²).
The biomass enhancement ratios of the artificial reef structures broadly ranged between 123
and 2,195 times. Fossil fuel is saved and CO2 emission is reduced leading to a nominal
contribution to the reduction if global warming and a considerable savings on fuel cost.
Robust economic benefit is recorded with a short duration payback period coupled with gain
in empowerment of the fisher community which enjoys a series of social benefits also. Hence
this environment friendly technology is strongly recommended for implementation all along
the Indian coastal waters to improve the inshore ecosystem and the livelihoods of traditional
fishers and other coastal community.
Introduction
Food security and Standard Nutrition are the two main priorities often stressed in the
developmental plans of most of the developing countries. The land under cultivation now will
not be able meet the ever increasing demand of food due to limitation on cultivable land for
raising agricultural crops, cattle and poultry. Naturally we have to depend on sea for our
future food requirement as the production in sea is three dimensional and can be increased
manifold by harnessing the production from natural resource with conservation and resource
enhancement activities coupled with mariculture. It is understood that the biological
production in coastal water is 12 times higher than the deep sea oceanic waters (Devaraj and
Vivekanandan, 1999) simply because of the penetration of sun light to the bottom of the sea
in shallow waters lead to higher primary production (Thorson, 1964). which triggers better
secondary and tertiary production ie., fishery resources. Hence the near-shore waters are the
breeding, feeding and nursery grounds for many species leading to the concentration of a
variety of species in good abundance.
Marine fish production in India increased continuously from a meagre 0.38 m t in
1950 to 3.2 m t in 2008 and it is stagnating around 3 million t in recent times as the Indian
inshore waters are almost over fished. The estimated potential yield of 2.2 million t from the
inshore waters has already been achieved where almost 90% of fishing effort is spent.
Further, the shallow inshore waters of Indian coasts are exposed to uninterrupted misuse by
adverse impacts of various developmental activities, pollutants, excessive, intensive and
extensive bottom trawling, inappropriate, illegal and unethical fishing practices. Added to
these, absence of proper management practices and conservation measures have consequently
led to senseless destruction of the inshore ecosystem, resulting in the reduction of stocks of
the component species of many fishery resources which may ultimately, adversely affect the
country‟s food security. Concerted effort is spent to develop the age old indigenous
traditional knowledge on artificial reefs called Mullam” (Sanjeevaraj, 1996) by improving
its longevity and ecosystem services to suit the modern requirements so that it will serve not
only as biological, biodiversity enhancement tool but also a technology to improve livelihood
options and socio economic conditions of the poor traditional coastal fishers. One such
practice advocated by CMFRI is the deployment of artificial reefs all along the near shore
coastal waters to reconstruct the coastal ecosystem (Adams et al., 2011), in general and in
particular the biodiversity and fishery resources through an execution process where the
community participation is blended with the technology transfer to reap the sustained benefit
from the nature.
Objective
The objective of the deployment of artificial reef modules in inshore water
ecosystems is to improve the environment by providing ample substrata for the settlement of
bottom living flora and fauna in the euphotic zone, so as to enable the production of
phytoplankton, algae and sea weeds, which in turn adequately support the enhanced
production of invertebrates and vertebrates in region concerned (Thorson, 1964).
Concept
The traditional concept of the artificial reef is to attract fish or a variety of fishes at
one location and harvest them with suitable fishing method during a particular season.
Traditionally fishers used either a whole tree or branches of trees bound together and sunk
weighted with stones as anchors in near shore water which attract a good amount fish due to
the biodegradation of the leaves and barks of the tree. These age old reefs are temporary,
often get dislocated by the mechanised bottom trawlers, forcing the fishers to spend every
season periodically a recurring expenditure in erecting these temporary reefs, which is cost
prohibitive and less remunerative.
The concept of the modern artificial reef is to construct them in reinforced concrete in
different shapes depending on the behaviour of different species of fishery resource with sole
aim to increase the hard substratum in the sea floor to enable the bottom living benthic flora
and fauna to settle on these hard substrata and grow lavishly so that they provide the basic
food, shelter and congenial environment which favours the visiting animals mostly fishes to
settle down there, live and breed to produce their young ones. Thus their population increases
in size and number. This makes a variety of commercially and economically valuable fish
species available for the fishers at all time to harvest in the artificial reef area (Kasim, 2009).
In coastal aquatic ecosystems biological production is three dimensional
encompassing length, breadth and depth. The biomass can be increased in this frame work of
volume dependent production by increasing the spread area of sea floor in the light
penetrating shallow waters. As an example, construction of a 10‟ x 10‟ wall with a thickness
of 1‟ in 10 m water depth, biological production will be lost in 10 square feet of the sea floor
which is covered by the wall. Whereas, the wall has increased the spread area by 23 times as
the wall has 230 square feet of spread area available for settlement and shelter of living
organisms. This enables the establishment of a colony of living resources in shallow inshore
waters. Deployment of complex concrete artificial reef structures with more spread area
enables the settlers and fouling organisms to colonise leading to an increase in the
biodiversity. This initially attracts many small fishes and then large fishes migrate into the
artificial reef area. Availability of sumptuous food and protective shelters encourages the
visiting fish population to settle in the reef areas and breed, which lead to a sustained increase
in the population size of various fish species. Most of the artificial reefs are established very
near to the fishing village and the fishermen need to travel very short distance to the fishing
ground. This results in a reduction in fuel consumption, expenditure and considerable amount
of savings. Assured availability of fish at all time leads to fishing in short duration of time,
ensuring good quality of fish. This leads to realization of better price. All these activities lead
to a sustained growth in the economy of coastal fishermen (Kasim et al., in press).
Artificial Reef Modules
Different structures like the pilings, pontoons and rock reefs have been studied
by Connell and Glasby (2001) to serve as marine habitats exhibiting variations in the
settlement composition and abundance of subtidal epibiota. Ryder (1981) reported different
materials such as the concrete, rubber and other miscellaneous materials were observed to
serve as the artificial reef materials. Extensive studies revealed that designed and
prefabricated artificial reef modules serve the purpose more effectively than the other
materials (Sheeby, 1982; Raja, 1986). Therefore, in this study following .
Grouper Module (GM)
A composite modular artificial reef apparatus
made of cement & concrete moulded with a large
subsurface framework, otherwise termed as grouper
module of fish aggregating device, for the purpose of
aggregating marine fish, which comprises of welded
grills of dimension of 0.75m x 0.75m with 6 mm M.S.
rods for reinforcement, coated with zinc chromate paint,
whereas the grills are placed in the oiled M.S. angle
mould with 1.25 cm bottom cover has been described. This artificial reef apparatus is made
with cement concrete with about 1:1:2 ratio using about 10 to 20 mm stone jelly mix filled in
the mould to 6.25 cm thickness and well consolidated, whereas after setting and removal of
the mould, the sides are dressed and finished with 1:2 mortar and allowed to cure in
freshwater for a minimum period of about 7 days. In addition to this, cement & concrete
moulded R.C.C pipe in a cylindrical mould is made with casting of about 0.75 meter long and
28 cm diameter with M.S. weld mesh cut in a cylindrical of about 0.75 meter length as the
inner reinforcement and cured in freshwater for about 7 days. Then the above mentioned 3
well cured concrete plates joined by welding the extended rods as triangular cube and the
joints are dressed and finished with 1:2 cement mortar and chips, whereas three numbers of
about 28 cm diameter pipes are placed in the triangular cube and fixed tight with the plates by
concrete mortar of 1:2 to avoid movement of the pipes. The outer sides of the triangular
cubes are finished with stucco plastering, and the plastered finished cubes are cured in
freshwater for a minimum period of about 5 days. These cement & concrete moulded
artificial reef apparatus to aggregate marine fish is used to aggregate marine groupers.
Reef Fish Module (RFM)
This cement & concrete moulded artificial reef
apparatus termed as reef fish module, comprises of
welded M.S. grills of dimension of 1.2 m x 1.2 m and are
coated with zinc chromate paint. The apparatus is made
with 1.2 m x 1.2 m steel mould with 23 cm x 23 cm
diameter square opening in the centre and 12 numbers of
15 cm diameter circular holes on the sides and are
prepared with coating of waste oil on inner side of the
mould. The grill is placed in the mould with 1.25 cm bottom cover and filled with 1:1:2
cement concrete mixed with 10 to 20 mm stone jelly to a thickness of 6.25 cm. After
consolidation and setting the steel moulds are removed, the sides are dressed with 1:2 mortar
and allowed to cure in freshwater for a minimum period of about 7 days.
Three such well cured concrete plates are joined to form a triangular cube by welding
the extended rods. The joints are dressed and finished with 1:2 cement mortar and chips, and
the outer sides of the triangular cubes are finished with stucco plastering, and cured in
freshwater for a minimum period of about 5 days.
Well Ring Module (WRM)
This cement & concrete moulded artificial reef
apparatus, otherwise termed as well ring module of fish
aggregating device, to aggregate marine fish, which
comprises of a well ring module, whereas this module
comprises of the grills prepared to the dimension of about
76 cm diameter and of about 30 cm depth, with 3 round
rings overlapping each other. This well ring module is
made with grills coated with zinc chromate paint, and whereas after fixing the grills in the
mould, cement concrete of 1:1:2 ratio mixed with 5 mm size baby jelly is filled in the mould
with proper consolidation and whereas after setting and removal of the mould, the sides are
dressed with 1:2 mortar and allowed to cure in freshwater for a minimum period of 7 days.
The plan and elevation the artificial reef modules are given below.
Salient characteristics of the
structures
1. Optimum spread area of the
substratum for the settlement of
foulers and other benthic encrusters
to attach and grow luxuriously.
2. Ample opening, holes and
crevices for the free gentle flow of
sea water to ensure availability of
better nutrient rich water with
sufficient dissolved oxygen and to
remove the excreted metabolites of
the living organisms from the
interior and surrounding of the reef structures.
3. Optimum weight of the structure for easy handling by the fishers to load on the boats for
self deployment and also not to get easily dislocated by seawater current and the trawlnets
of mechanised bottom trawlers.
4. With variable shapes so as to provide required shelters and desirable by different bottom
and column living demersal fin fish and other invertebrate resources in tune with their
behaviour.
5. Combination of the structures should provide an optimum biomass production ensuring
luxurious growth of flora and fauna of diversified taxa, genera, families and species
leading to an enhancement in the biodiversity of the region concerned.
6. The shape should not permit sinking of the structures even in semihard sandy terrain and
loose the functional ability in due course of time.
7. External surface is made rough with stucco plastering to promote easy settlement of the
spats, larvae and young ones of the fouling organisms.
8. The structures are designed in such a way that they may continue to be productive even for
a couple decades and more and the production capability of these structure may get
reduced afterwards owing to the filling of the gaps, holes, crevices and inner space by the
encrustation of the hard materials of the fouling organisms which turn these complex
structure into a heavy mass of rocky boulder devoid of complexity.
Spread area of AR Modules
The substratum provided by a single Grouper Module is estimated to be 16.04 m2 and
70 numbers of Grouper Modules provide a total area of 112.8 m2 (16.04*70=112.8 m2), one
Reef Fish Module provides an area of 13.5 m2 and 70 numbers of Reef Fish Modules provide
a total area of 945 m2 (13.5*70=945 m2) and a Well Ring Module is estimated to provide
10.2 m2 and 70 Well Ring Modules provide a total area of 714 m2 (10.2*70=714 m2). Total
substratum provided by all the 210 numbers of modules is worked out to be 2781.8 m2. The
cost of one cluster of 210 numbers of artificial reef was Rs.11,50,000 including fabrication
and deployment during 2006 and it must be higher owing to the escalation in the prices of the
raw materials such as the cement, steel rods, sand and blue metals and labour cost. Total
volume of these 210 artificial reef structures is estimated to be 446.25 m3 were deployed in
one cluster in a spread area of 1000 m2.
Methodology
The above described 3 types of artificial reef modules were fabricated at two places in
Tuticorin Fishing harbour for two sites at Vellapatti and Vembar in Gulf of Mannar and at
Sethubavachathiram in Tanjore District for the rest of 9 sites in Palk Bay and Bay of Bengal.
The AR modules have been deployed with the help of Tuticorin type cargo vessel called
Thoni in Tamil in Gulf of Mannar and with a steel barge towed by wooden trawlers in Palk
Bay and Bay of Bengal.
Roving Diver Technique (RDT; Schmitt and Sullivan 1996), a visual survey method
was employed for studying the flora and fauna assemblage, abundance and succession during
study period. During the underwater survey, the SCUBA divers swim freely throughout a
artificial reef site and record every fish species that can be positively identified. The goal is to
identify as many species as possible, so divers are encouraged to look under ledges and up in
the water column. At the conclusion of a survey, each recorded species is assigned one of
four abundance categories based on how many individuals were seen throughout the dive
(single [1]; few [2-10], many [11-100], and abundant [>100]).
The most common method to quantify fairly uniform fouling is by stating the average
deposit surface loading, i.e., kg of deposit per of surface area (Rutecki et al., 1985). The
fouling rate can be expressed in kg/m², and it is obtained by dividing the deposit surface
loading by the effective operating time. The data analysis has been recruitment, colonization
and seasonality of plant, crustacean, molluscan and fish species at natural and artificial reef
sites. Video observations suggest that algal cover was intense and protracted with seasonal
variation.
The artificial reefs were also monitored using underwater video and diver census
during 2007 and 2008. Results also indicate that the use of underwater video is an effective
method for monitoring fish populations and a cost effective means of carrying out monitoring
programs associated with artificial structures. Although similarities between artificial reefs
and naturally occurring reefs were evident, some differences in relative abundances and
species diversity were observed at Vellapatti and Vembar in Gulf of Munnar. These
differences are attributed to the presence of live coral islands nearer to the artificial reef sites
in Gulf of Mannar and absence of such environment in the rest of the sites in Palk Bay and
Bay of Bengal. It is difficult to estimate the overall productive value of artificial reefs.
However the productive value of the artificial reefs over larger spatial scales was attempted
indirectly by this study by collecting fishery data from the reef area and as well from the non
reef area. The summaries/conclusions of all these analyses have been used to deduce the
ecosystem services of artificial reefs in this study.
Biological processes
Artificial reef is an eco-friendly bio-resource enhancement technology. These
artificial reef modules settle easily at the sea bottom floor and enable the floral growth on the
surface with associated fauna within 4-6 months, which is the time necessary for maturation
of the reef. Immediately after the deployment of the artificial reef modules biological fouling,
an accumulation process of micro-organisms, algae and diatoms, plants, and animals started
taking place on surfaces of the artificial reef structures. Initially the bacteria form biofilms or
slimes on the rough surface of the artificial reef modules and then organisms aggregate on
surfaces using colloidal hydrogels of water and extracellular polymeric substances (EPS)
(polysaccharides, lipids, nucleic acids, etc. Bacterial fouling is observed to occur under either
aerobic (with oxygen dissolved in water) or anaerobic (no oxygen) conditions. Under aerobic
condition bacteria prefer open systems, when both oxygen and nutrients are constantly
delivered, often in warm and sunlit environments. Anaerobic fouling is reported to occur in
closed systems when sufficient nutrients are present. This type of fouling leads to the
settlement of more than one fouling mechanisms working simultaneously. The process of
multiple fouling in which, the mechanisms may interact with each other resulting in a
synergistic fouling which is more than a simple arithmetic sum of the individual components.
It was observed that massive settlement process of bio-foulers like the barnacles, coral line
algae, ascidians, tunicates, sponges, soft corals, hard corals, algae and sea weeds of different
species takes place immediately after the biofilm formation. Cuttlefish and squids have
deposited voluminous egg-masses amidst these concrete modules, and crabs and lobsters
crawled on their surfaces, Algae, bivalves and barnacles literally choked the hollow of these
concrete rings. New food-chains were formed at these reefs.
The initial colonisation of lower invertebrates itself attracted a succession of fish
species. In the beginning first to visit the artificial reef were the different species of
carangids, coral fishes like the damsels, clownfish, dumbheads, wrasses, squirrel fish, perches
like lethrinids, balistids, parrotfishes, Diagramma spp, Epinephelus spp, rays, squids and
cuttlefishes. All these species may be called as the „visitors‟ and they were visiting the
artificial reef temporarily for feeding purpose. The abundant availability of live food in the
artificial reef area and protective shelters induced some of the species to stay back and
continue to live in the reef area. These species may be called the „residents‟. Latter these
species started to breed in the reef area and contributed to the recruitment into their
population leading to an increase in the population size of these species.
Sessile epibenthos
The samples collected from artificial reefs off Vellapatti and Vembar in Gulf of
Mannar had better standing stock biomass of sessile epibenthos of 2,468 to 3,919 g/m² on
horizontal surfaces and 4,218 to 7,726 g/m² on vertical surfaces than those recorded in other
area. Along Palk Bay and Bay of Bengal the average sessile biomass was estimated to be
1,838 g/m² on the exposed outside of concrete reef structures and 3,318 g/m² on the protected
interior of the reef structure.
Composition of fouling biomass
The faunal community eventually consisted representatives of seven phyla and about
38 species, as followed: 8 polychaetous annelids, 9 crustaceans, 7 mollusks, 6 coelenterates, 2
bryozoans, and 2 others. The amphipod crustaceans, three caprellids and three tube-building
gammatid amphipods, were the earliest and most abundant settling foulers. This
unexpectedly high abundance of amphipod crustaceans is assumed to result from the high
turgidity in the study area. Polychaetes (nereids and polynoids), molluscs (sessile bivalves),
and other fouling organisms such as hydroids, actinians, and bryozoans, were lately
represented. Algal succession on artificial reefs was comprised of filamentous algae were the
primary colonizers; the fleshy brown alga, appeared soon after. Low light penetration through
the water owing to the suspended sold load during certain period and selective browsing by
herbivorous fishes favour the blue-greens to be the dominant algae in the climax community
which, occurs within a 1-year period.
Assemblage of fauna
The samples from the Gulf of Mannar indicated significantly higher abundances of
total infauna, and of polychaetes, bivalves, isopods and cephalopods. Within a few weeks,
research divers had observed lobsters on the reef, even though the reef blocks had been
deposited on flat sand some distance (3 km) from the nearest natural reefs. Colonization by
epibiota was monitored using direct observation and photographic recording of block
surfaces. Epibiota showed seasonal variations in abundance throughout the year overlain with
a progression in the numbers of species present and a maturation of the population towards
the epibiotic populations seen on local natural reefs. Adult lobsters and crabs from the local
natural reefs were recruited to the reef within 3 weeks. The most numerous shoaling fish
congregating around the reef units has been the caranagids and rays, Diagramma sp, butterfly
fish, squirrel fish, groupers, sweet-lipped breams, red snappers, catfish, small coloured coral
fishes like the blue damsel, wrasses and dumbheads. Shoal size was commonly estimated at
around 200 individuals per reef unit.
Predation
The grazing of reefs by both vertebrate and invertebrate predators can greatly reduce
the biomass of the fouling community. Significant grazing of macrophyta by sea urchins on
the reef in Vellapatti and Vembar was quite common. Dense mats of blue green algae that
appear in spring are often grazed clean by fish, crustaceans and starfish before winter. Since
there were also predators, such as crabs, lobsters, starfish and sea urchins, on the inside of the
unit that undoubtedly grazed on the protected fouling growth, the actual predation rate on the
unprotected exposed area was probably considerably higher than that observed. Standing
stock biomass is only a static measurement of the productivity of a reef. It is not an indication
of all the biomass that was produced over the extended time period before samples were
collected.
Succession
It is generally noted that fast-growing, short-lived species are usually the first fouling
organisms to colonize tropical reefs, followed by slow-growing, long-lived species which
eventually replace the initial colonizers. Off Gulf of Mannar, hydroids, bryozoans, barnacles
and ascidians are the first visible organisms to appear on reef substrates, followed by
anemones, stony coral and sponges. The following succession stages on reef structures was
identified over a 2-year period: a. Bacteria Algae, b. Barnacle Hydroid, c. Mollusk
Polychaete, d. Sponges - Ascidian and e. Anemone Stony coral.
Enhancement Value
When the benthic community is dominated by a mixture of polychaetes, small
crustaceans such as amphipods, smaller less-domineering molluscs, and other macrofauna the
wet weight biomass of the area greatly exceed 500 g/m². When these species are not
colonizing an area, the wet weight benthic community biomass is commonly less, about 30-
50 g/m². The enhancement ratios of standing stock biomass of the artificial reef habitats
(57,075 g/m², minus fish biomass) vs. sand sediment infauna range from 24 to 123 times for
clam-dominated sand substrate and 771 to 2,195 for polychaete crustacean-dominated
sediments. Concrete reef exhibited an enhancement ratio of 168 to 354 times the infaunal
biomass from an equivalent area of the surrounding sandy sediments. Another ultimate
succession stage is dominated by cnidarians, such as anemones, coral and hydroids.
Cnidarians are of little value as food for other marine life, and this represents a much less
productive reef community in terms of providing habitat for fish and lobster. Therefore, the
enhancement ratio of a cnidarians-dominated reef would be much lower than that of other
reef structure. The high biomass of clam-dominated sand bottom illustrates the importance of
the open sand in providing a food resource for reef inhabitants. For this reason, reefs should
be constructed apart from each other, separated by extensive expanses of sandy bottom.
Economic benefits
Artificial reef is an appropriate low-cost rural technology highly suitable for the
betterment of the economy of the artisanal and traditional coastal fishermen of the Indian
coast, especially for the coast where the exploitation is intensive and extensive, leading to the
depletion of the fishery resources. Even the poorest of the poor artisanal fishermen who
cannot afford a net, can easily afford a hook & line, to earn his daily bread by venturing to
the AR areas for fishing. Artificial reefs made of concrete modules are one-time investment,
with no recurring costs for fishermen. Cost-benefit analysis worked out from the landing
details from a reef area deployed off Pulicat near Sathankuppam in 2007 reveal that for a
period of six months the economics of artificial reef seems to be incredibly remunerative. A
sum of Rs. 20 lakhs has been realized as gross annual sale proceed from the fish caught from
a single artificial reef site established at a total cost of Rs. 5,00,000. After deducting a sum of
Rs.7,67,000 towards the operational expenses, depreciation of craft and gear, interest on
capital investment, opportunity cost etc the net income is estimated to be Rs. 12,33,000 and
the payback period is estimated to be 0.4 years (Jhon,2007; per. Commn.).
The assessment of fisheries service provided by an artificial reef at Chinnandikuppam,
20 km south of Chennai by Vivekanandan et al., (2006) revealed that in 16 months, the hooks
& line fishermen expended 3843.7 hrs of fishing in the AR ground and landed 6404 kg. The
catch index was 14.2 kg/ m3 and the total income was Rs.2.74 lakhs. Comparatively Kasim et
al., in press IJF) have reported that a single hooks & line unit in 16 months, fished in artificial
reef area for 2821 hrs and produced 23,812.5 kg, which yielded an income of Rs.21.4375
lakhs. This shows that the catch is 3.7 times more and the income is 7.82 times higher than
that reported by Vivekanandan et al., (2006). This may be owing to better performance of the
concrete reef structures with more surface area (2781.8 m2) which might have lead to higher
biological production and better fish catch. Vivekanandan et al., (2006) and Kasim et al., (in
press) have also observed that the hooks & line operation in the AR area (Rs.71.3 kg/h) was
more remunerative than the gillnet operation (Rs.52.5/kg/h) in the NAR area and they also
attribute this to the aggregation of high quality fish such as the snappers, emperor and
carangids in the AR area. The payback period of artificial reef at Chinnandikuppam works
out to 1.22 years (Vivekanandan et al., 2006), whereas Kasim et al., (in press) have reported
0.23 year, may be owing to better performance of the concrete structures of ARs.
Social benefits
Artificial reefs can be established as the common village property and can be operated
by the village fishermen as a whole by evolving a system of sharing the fishery resource
among them by appropriate fishing practices. Since the whole community is expected to
participate in installing the artificial reef, the entire community has the right to fish at the
reefs through custom evolved fishing practice. This incidentally strengthens the community
to build up the solidarity of the fishing village community, without any disparity between the
richer and poorer fishermen, within the village. The fringe benefit for the traditional
fishermen is that the artificial reefs may help to prevent the operation of mechanized trawlers
in the area where the artificial reef structures are deployed into the coastal waters and this
will minimize the long-standing enmity between traditional fishermen and mechanised
trawler operators.
Artificial reefs in due course of time evolve as a natural reef almost imitating the
natural coral reef if there happen to be a coral reef available in the nearby area. This reduces
the dependence of the fishermen on the natural coral reefs and provides alternative livelihood
for the coastal fishermen. Further the artificial reefs support a good population of ornamental
fishes. Harvesting of these ornamental fishes by traps may provide additional income for the
fishermen. Artificial reefs may be used as the site for ecotourism by the fishermen. Above all
these the payback period of one artificial reef is less than a year and makes the proposal of
artificial reef as a bankable project. The combined benefits of artificial reefs are conservation,
better fish catch, fuel saving, fish available throughout the year, better economic return for
the poor coastal fisher men. This leads to an increase in the biodiversity also.
Ecosystem services
A series of ecosystem services as detailed below have been recorded due to the
deployment of artificial reefs.
1. Approximately an estimated 1000 sq m (31.63 x 31.63 m) primary core
surface area is created as an indigenous and community conserved areas (ICCAs) for basic
biomass production.
2. Nearly 5000 sq m (70.71 x 70.71 m) of protected secondary core area is
created where secondary and tertiary producers thrive well over a short period of 6 months.
3. An estimated 10000 sq m (100 x 100 m) of buffer zone is created which serves
as a significant coastal ecosystem with improved conservation status and support wide variety
of biodiversity.
4. As much as 10 ha of additional fishing grounds have been developed for the
poor traditional fishers to carry on sustainable fishing leading to improvement in their socio
economic condition.
5. Nearly 10 ha of deteriorated, battered almost barren sea bottom due to
constant bottom trawling by the mechanized trawlers has been restored and made suitable for
thriving of various bottom benthic and free living flora and fauna leading to enhanced fishery
resources in the area.
6. Immigration and emigration of different varieties of fishes have been observed
to occur in the 10 ha buffer zone, where some of them become resident population which
breed and consequently an increase in the population size of various fish species was
observed in the artificial reef area and serves as a source uninterrupted supply of food, shelter
and congenial environment for living by many species of diversity which ensures the fish
availability in the artificial reef area at all time. All the traditional coastal fishermen have
sustainable fishing in the artificial reef zone and there is no fish famine.
7. On an average about 600 fishers have been empowered in artificial reef
building, deployment and management through this proven age old technology and the
community has been subjected to capacity building and management skill of the artificial reef
and fishery resources.
8. As many as 600 fishers have participated in the process of conservation and
restoration of coastal ecosystem and have been diverted from the traditional fishing grounds
to artificial reef zone leading to a considerable reduction in the age old traditional fishing
ground. These fishers have started practicing “Joint fishery management” where such practice
was non existence in olden times.
9. The increased availability of fishes adds to the income of artisanal fishermen
particularly those involved in coastal fishing using hooks & lines and surface gillnetting.
10. The unregulated illegal dynamite fishing and inappropriate fishing like pair
trawling will be prohibited in the artificial reef area through community managed fishing
system which avoids disparity in benefit sharing of the biological resources and to avoid over
fishing.
11. To completely enclose a portion of the ocean environment as a measure of
conservation is impressively costly, compared to simply controlling the area with the
deployment of artificial reefs modules, which comparatively represent only minor cost per
unit area controlled. Accordingly, there exists a need for a means by which fish habitats can
be reconstructed or created in a manner which is quick, easy and effective.
12. Since the artificial reefs are deployed in shallow waters within 20 m depth
range and this will limit the extent of operation of mechanized trawlers. An estimated 10000
sq m area will be developed as a conserved area devoid of the ill effects of mechanized
bottom trawling and made available as micro marine protected area (MPA).
13. Biomass production in the artificial reef structures is estimated to vary
between 2.5 and 5 tons per year.
14. An estimated 1,90,000 US$ worth of biodiversity product/ecosystem service
produce per annum.
15. Planting of one artificial reef module can sequester in the sea between 3.66 to
10 kg of carbon dioxide every year and 210 artificial reef modules reduced annual CO2
emissions by 732 to 2000 kg every year.
16. There will be no scouting time in search of fish and considerable reduction is
there in fishing time.
17. Considerable savings is observed in fossil fuel and fishing time due to the
proximity of the fishing ground in the artificial reef area. 5 l of fossil fuel saved per boat per
day as they limit the travel to and fro the fishing ground which is on an average below 5km
distance from the fishing village and the fishers need not hunt for fish far and wide wasting
their fuel.
18. Consequently the reduction in CO2 emission per boat per day is estimated
roughly to be 13.25kg. Approximately 150 boats conduct fishing in the reef area every day
which reduce the emission of 1987.5 kg CO2 per day. 2 tons of CO2 is estimated to be
avoided by implementing this low carbon technology and 150 boats reduce an estimated
496.875 t of CO2 per year. 2625 mt Green House Gas reduced per year @10.5 mt per day.
19. In addition to saving 750 l of kerosene/diesel every day by these 150 boats,
there will be further savings of 150 l a day on fuel while these boats can frequent the fishing
ground in the reef area with the help of sail if the wind is favourable or the fishers may use
their muscle power to oar their way to the fishing ground and back to the village.
20. Approximately an estimated Rs.37,500 per day is being saved on all the
fishing days by these 150 boats and there will be an additional Rs.7,500 on all the days when
all the boats either use sail or oar for their fishing trip. 150 boats saved 1,87,500 l of diesel
every year since they fish in the artificial reef zone on an average 250 days in a year.
Rs.93,75,000/- value of transportation service for fuel consumption being saved per day.
21. Artificial reef provide an opportunity to fishers to exercise community based
participatory joint fishery management practices resulting in socio economic betterment of
the community.
22. Almost all the fishers employ ecofriendly fishing methods such as the hand
lines with small to moderate sized hooks, traps with different mouth size and to some extent
drift gillnetting on the adjacent areas of the artificial reef zone.
23. When the cumulative impact of all these interactions may be considered as
significant achievements and replication of this all along the coast in almost all the near shore
waters of all fishing villages may produce an excellent improvement in the ecosystems and
livelihoods of the fishers.
24. Compared to the agricultural activities in an Agrarian Village, as the usage of
harmful chemicals is totally avoided in artificial reef zone, fish production in this area may be
considered as purely organic. Hence this practice of providing an artificial reef with 10 ha of
area for fish production in one fishing village may be insufficient and replication of this at
different areas is strongly advocated to create better organic natural coastal ecosystem.
Summary
During the 24-months study, a total of 137 taxas were identified living within the
artificial reef habitats and the artificial reef habitats were colonized by on an average 423,948
individuals of marine organisms and had a total mean biomass of individual and colonial
organisms of 58,35g per m². Comparatively the artificial reef structures were more complex
and had greater surface area than most other reef structures and consequently had a greater
density of marine life. There were considerable year-to-year fluctuations in sampling unit
total biomass and dominant species. The artificial reef habitats provided refuge cover for a
large numbers of small and bigger fish (135.3/m²), crab (3,445.9/m²) and lobster (22.9/m²).
The biomass enhancement ratios of the artificial reef structures broadly ranged between 123
and 2,195 times. Fossil fuel is saved and CO2 emission is reduced leading to a nominal
contribution to the reduction if global warming. Robust economic benefit is recorded with a
short duration payback period coupled with gain in empowerment of the fisher community
which enjoys a series of social benefits also. Hence this environment friendly technology is
strongly recommended for implementation all along the Indian coastal waters to improve the
inshore ecosystem and the livelihoods of traditional fishers and other coastal community.
Acknowledgements
The authors are sincerely thankful to the Commissioner of Fisheries, Joint Directors
and other Staff of the Tamil Nadu Fisheries Department for providing the consultancy and
assistance in the field for fabrication and deployment and during the study on the impact of
artificial reef on the socio economics of the coastal fishery and fishers. The technical
assistance rendered by the FRA Division, SCUBA divers, all other divisions who were
involved with this project and specially the coordination rendered by the Consultancy Cell of
CMFRI are gratefully acknowledged. We are immensely grateful to Dr. M.J. Modayil,
Former Director, CMFRI, but for him this project would have not come to CMFRI, for his
guidance, constant encouragement and support all through the implementation of this project
and final report preparation. Many fishermen leaders, fishers and others worked hard with us
which is gratefully acknowledged.
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... Based on the threshold value of depth, the unsuitable and suitable areas have been represented in red and blue, respectively ( Figure 1A). The cost-effective distance is very useful since the ARs give an excellent chance for impoverished artisanal fishermen who can't afford a net can easily use a hook and line, to earn their livelihood by venturing to the AR areas for fishing (Kasim Mohamad et al., 2015). While, the optimal depth range helps in larval settlement on the AR structure (Duzbasilar et al., 2006). ...
... In-situ and satellite data validation is well reported for selected physicochemical parameters, e.g., chlorophyll-a, in southeast coast of India and it revealed good correlation coefficient (r 2 = 0.89) (Selvavinayagam et al., 2003). Though the present study was limited to site suitability for AR deployment, earlier reports on the postdeployment study indicated a higher aggregation of juvenile fishes at the AR site along the Tamil Nadu coast. 1 A systematically planned site selection approach contributes to the development of an ecosystem around the AR, which in turn promotes sustainable rural technology highly suitable for the livelihood enhancement of artisanal and traditional coastal fishermen (Kasim Mohamad et al., 2015). It is claimed that biomass output in the ARs regions ranges between 2.5 and 5 tons per year, with biodiversity products/ecosystem services valued at USD 190,000 per year (Kasim Mohamad et al., 2015). ...
... Though the present study was limited to site suitability for AR deployment, earlier reports on the postdeployment study indicated a higher aggregation of juvenile fishes at the AR site along the Tamil Nadu coast. 1 A systematically planned site selection approach contributes to the development of an ecosystem around the AR, which in turn promotes sustainable rural technology highly suitable for the livelihood enhancement of artisanal and traditional coastal fishermen (Kasim Mohamad et al., 2015). It is claimed that biomass output in the ARs regions ranges between 2.5 and 5 tons per year, with biodiversity products/ecosystem services valued at USD 190,000 per year (Kasim Mohamad et al., 2015). Increase productivity by reducing fishermen's reliance on natural coral reefs; it also promotes a healthy ornamental fish population, ecotourism, and natural resource conservation. ...
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