The general consensus is that most of the fisheries resources in the APFIC region, especially in Asia, are showing signs of overexploitation and severe degradation. This is particularly evident in the inshore coastal areas where (i) stock assessments of major species, (ii) historic research surveys, (iii) analyses of ecosystem changes and (iv) perceptions of fishers all show the same trends. The evidence is so overwhelming that any call to delay management action until more scientific assessments are available must be seen as irresponsible.
In inland waters, most fisheries are small-scale activities where the catch per capita is relatively small and used mainly for subsistence purposes. The lack of accurate reporting of these small-scale fisheries makes it difficult to describe their status, but it is generally felt that they are under considerable pressure from loss and degradation of habitat as well as overfishing.
In many of the seas of the APFIC region, traditional methods of assessing the status of fisheries resources, using scientific stock assessments, setting of reference points and monitoring performance against these reference points, is not really practical. This is due, firstly, to the complexity of the tropical systems that predominate in the region - the multi-species/ multi-gear nature of the fisheries and, secondly, the lack of capacity to carry out the necessary assessments and/or monitoring, especially in areas where fish are landed in multiple small landing sites or along the beaches.
Reporting of total production also often masks what is actually happening in the fishery, and should not be used as an indicator of resource status.
In this analysis we look at the evidence on the status of marine resources based on four methods:
Regular stock assessments are conducted in some of the more developed countries of the region (Table 14). However, even in these countries the number of species regularly assessed is often relatively low. In the case of Japan and Malaysia these assessments are used in day-to-day fisheries management, but in the other countries the scientific results are only partially integrated into management decision-making. In cases where it is possible to assess the status of individual stocks, current catch levels often exceed Maximum Sustainable Yield (MSY) estimates and many of these stocks are designated as over-fished.
In many other countries, single species stock assessments are not conducted regularly but a common practice is to conduct "multi-species" assessments from time to time using aggregated catch and effort data in simple production and similar models. The reliability of these types of assessments is known to be very low and the degree of uncertainty very high (the basic assumption that the catch per unit effort (CPUE) is a good indicator of fish relative abundance is often not met). The results are not in a form that can be used regularly in management but are often used to set targets for future fishing capacity and total yields. In many cases, the uncertainty of these assessments has not been taken into account and the predictions have proved to be too optimistic, often accelerating the decline in the resources.
The results of the WorldFish Center (WorldFish) study on scientific trawl surveys (Trawlbase)1 was reported in the previous APFIC "Status and potential of fisheries and aquaculture in Asia and the Pacific". These analyses were available on the status of fisheries from eight APFIC States (Bangladesh, India, Indonesia, Malaysia, the Philippines, Sri Lanka, Thailand and Viet Nam), based on trawl survey data spanning the period 1920 to the present. The surveys covered a wide area of the Asian sub-region (Figure 26). Unfortunately, funding for this project has finished and there is no update on earlier findings. There are also other very comprehensive survey data available for other areas, especially those carried out by the Fishery Survey if India (FSI) that started in 1946 and currently deploys more than 12 vessels along the Indian coast and the Andaman and Nicobah Islands that could be included in future analyses.
Table 14
Summary
of stock assessments in selected APFIC countries
Country |
Regular stock assessment |
Number of species |
Resource surveys |
Reference points |
Used in management |
China PR |
Yes |
8 |
Yes* |
MSY, MCY etc. |
Yes (Selected species) |
India |
Yes |
~50 |
Yes |
MSY |
Yes (partial) |
Indonesia |
No |
Multi-species** |
Yes* |
Generic MSY |
Yes (partial) |
Japan |
Yes |
Main species** |
Yes |
MSY, MEY etc. |
Yes |
Korea RO |
Yes |
9 |
Yes (Yellow Sea) |
MSY, MEY etc. |
Yes (partial) |
Philippines |
No |
Multi-species** |
Yes |
Generic MSY |
No |
Malaysia |
Yes |
Main species** |
Yes |
MSY, MEY etc. |
Yes |
Myanmar |
No |
Multi-species** |
Yes* |
Generic MSY |
No |
Thailand |
No |
Multi-species** |
Yes |
Generic MSY |
No |
Viet Nam |
No |
Multi-species** |
Yes* |
Generic MSY |
No |
* Resources surveys not regular.
** "Multi-species" assessments based on aggregated catch and effort data.
Figure 26
Trawl surveys in the Asian region
From Silvestre, G.T., Garces, L.R., Stobutzki,
I., Ahmed, M., Santos, R.A.V., Luna, C.Z. and Zhou, W.
(2003). South and Southeast Asian coastal fisheries: Their status and directions for improved management. Conference Synopsis and recommendations,
p. 1-40 in Silvestre, G.T., Garces, L.R.,
Stobutzki, I., Ahmed, M., Santos, R.A.V., Luna, C.Z., Lachica-Alino, L.,
Christensen, V.,
Pauly, D. and Munro (eds.) Assessment, Management and Future Directions for Coastal
Fisheries in Asian Countries. WorldFish Center Conference Proceedings 67, 1 120 pp.
However, despite the fact that the work is not on-going, we consider these WorldFish analyses based on scientific surveys the most convincing evidence that is available on the status of resources in trawled areas in the Asian sub-region and worth reiterating.
The analyses of the trawl surveys showed considerable degradation and overfishing of coastal stocks. In surveys that were carried out for periods greater than 25 years, the amount of fish (measured as tonnes/km2) had declined to between 6 and 33 percent of the original earlier value. The amount of fish available to today's fishers had declined in all countries, some as much as 40 percent in five years. The most dramatic declines were in the Gulf of Thailand and the East Coast of Malaysia. Two examples, one for the Gulf of Thailand and one for Manila Bay are given in Figure 27.
The Trawlbase study also enabled an estimation of the exploitation rate for 427 stocks in the region. With the exception of the coast of Brunei Darussalam, where fishing pressure is less intense, the majority of stocks were being fished at levels above the recommended optimum range.
The surveys also demonstrated that the abundance of larger, more valuable species (e.g. groupers, snappers, sharks and rays) higher up in the food chain have declined, while smaller species lower in the food chain (e.g. triggerfish, cardinal fish and squids/octopus) have increased to relative abundance. In the Gulf of Thailand trawl survey catch in the 1960s, the top ten species (or species groups) were made up of rays, bream, goatfish with some squid, lizard fish and snapper (Figure 28). By contrast, in the mid-1990s less desirable pony fish, squid, barracuda, and lizard fish had become much more prevalent. This "fishing down the food chain" appeared to be a common phenomenon in many of the trawl survey data.
Socio-economic assessments
WorldFish also carried out some in-depth socio- economic assessments of the eight participating States. This allowed an assessment of the importance of coastal fisheries in terms of earnings, employment, trade and nutrition and their contribution to the economy. The profitability of fishing operations in Malaysia, Thailand and Viet Nam was studied, and broken down into several sub-sectors.
In general, fishing is still a profitable enterprise in all of these three States, particularly for the owners of industrial fishing vessels. Owners of industrial craft and gear earn large profits (up to 30 percent per year) while artisanal, small-scale fishers often have an extremely marginal livelihood, although benefits are not evenly distributed. Unfortunately, profits from industrial fishing do not flow into the rural communities as it employs few crew and provides little opportunity for unemployed or under-employed small-scale fishers.
The loss in revenue and profits associated with overfishing and degraded resources were demonstrated using the Gulf of Thailand as an example (Table 15). Based on 1995-96 data, large rent dissipation and excess capacity (in both labour and capital) can be clearly seen. Similar analyses have been done for the Philippines and other areas in the past. More of these sorts of analyses should be carried out to guide future policy decision-making.
APFIC's Large Marine Ecosystems
To date, 63 LMEs have been described worldwide with twenty of these being in the APFIC region.
Much of the information used below has been taken from the NOAA website, which acknowledges sources of information and has an extensive reference list,2 as well as an analysis of the FAO catch database as modified by the University of British Columbia3 ("Sea around us" project).
The Asia-Pacific region is characterized by considerable diversity in LMEs in terms of their fisheries and driving forces (Table 16). The table has excluded four LMEs from Australia as well as the large Western and Central Pacific. The four Australian LMEs were excluded as their catches were very small and not important to the analysis. In the case of Western and Central Pacific, this area was not included as an LME on the "Sea around us" website.
Figure 27
Declines
in the abundance of fish in (i) Manila Bay and (ii) Gulf of Thailand as
measured by trawl surveys.
From same source as Figure 26
Figure 28
Changes
in the composition of the top ten species taken from trawl survey catches in
the Gulf of
Thailand between 1966 and 1995. Data from same source as Figure 26
Table 15
Comparison
of catch, revenues, costs and profits at different levels of fishing effort
(MSY = maximum sustainable
yield; MEY = maximum economic yield). From same source as Figure 26
State of fishery |
Effort |
Catch |
Revenue |
Costs |
Profit |
MSY |
28.57 |
985 |
6 578 |
1 992 |
4 586 |
MEY |
21.75 |
952 |
6 359 |
1 517 |
4 842 |
Open access |
62.70 |
654 |
4 372 |
4 372 |
0 |
Actual (1995) |
56.88 |
728 |
4 862 |
3 966 |
896 |
In terms of the total recorded catch since 1950, the most productive LMEs are the East China Sea, the Kuroshio Current and the South China Sea. Following closely behind are the Yellow Sea, the Sea of Japan, the Bay of Bengal and the NW Pacific high seas area.
The Indonesian Sea, the Gulf of Thailand and the Sulu-Celebes Seas are clustered in another group, followed by the much smaller catches in New Zealand and Australia LMEs.
All LMEs have a mixture of pelagic and demersal species, although pelagics dominate in most LMEs, especially in the Kuroshio Current, Sea of Japan, Yellow Sea, East China Sea, South China Sea, Arabian Sea, Sulu-Celebes Sea, and Indonesian Sea.
In the Kuroshio Current, Sea of Japan, Yellow Sea, East China Sea and South China Sea, the major species are the Japanese pilchard (Sardinops sagax - melanostictus) , chub mackerel (Scomber japonicus) and the largehead hairtail (Triciurus lepturus).
In the Bay of Bengal, Arabian Gulf, Sulu-Celebes Seas, Indonesian Sea and NW Australia, anchovies Stolephorus spp. and Engraulidae) form a large part of the catch with other small pelagic species such as the sardine (Sardinella spp.) common in some areas. Pacific saury (Colobis saira) has formed a large part of the catch in the high seas of the NW Pacific.
Exceptions to this pattern are the heavily trawled areas of the Gulf of Thailand and Northern Australia where more demersals, threadfin breams and shrimps, respectively, are taken, although even in these areas catches of anchovies are almost as high as the demersal catches.
In terms of total catch, bottom trawling takes the largest proportion of the catch in 12 out of the 15 LMEs included in Table 16. This includes pair trawling that, in many areas of the region, operates high-lift nets that catch significant quantities of bentho-pelagic species, such as the largehead hairtail and pelagic species such as Japanese anchovy. As expected from the nature of these fisheries, catches from mid-water trawls and purse seines are also large, especially in the more pelagic LMEs.
These statistics, however, tend to mask the importance of the small-scale fisheries to these LMEs, and although no firm data are available they are known to constitute a large proportion of the catch from many areas.
Many LMEs are shared by several countries. For example, the Bay of Bengal is bordered by eight countries that all contribute to its catch. Table 16 shows the distribution of catch by countries as estimated by reported landings and distributed on the basis of known access agreements in other country's EEZ. There are some obvious discrepancies in this analysis (e.g. high catch by Indonesia in Southeast Australia), but it does demonstrate the multi -national nature of the sector and the many shared fish stocks that are taken by several countries in each LME.
Catch trends in selected Large Marine Ecosystems
Based on their overall trends in catches, the LMEs of the APFIC region were categorized into four major groups in the 2004 "Status and potential of fisheries in Asia and the Pacific":
i. |
Offshore deepwater systems dominated by pelagic fishes (e.g. Kuroshio Current and NW Pacific); |
ii. |
Heavily fished coastal systems that display sequential depletion of species groups characteristic of "fishing down the food chain" (e.g. Yellow Sea, Gulf of Thailand and NW Australia); |
iii. |
Coastal systems that are still showing increasing reported catches in all species groups (e.g. Bay of Bengal and South China Sea); and |
iv. |
Fisheries managed under tight access right controls (e.g. Southeast Australia and New Zealand Shelf). |
One example of each of these categories is analysed in some detail below.
Kuroshio Current
The catch in the Kuroshio Current showed a sharp peak in the mid-1980s with catches of 2.9 million tonnes. Since then there has been a dramatic decrease and in 2003 the total catch for the area was only 684 thousand tonnes. The peak in 1986 was dominated by medium pelagic species, mainly the Japanese pilchard that comprised 78 percent of the catch. In 2003 this figure decreased to 26 percent. Instead, small pelagic fish, such as Japanese anchovy, are now the most commonly caught group of species.
Table 16
The large marine ecosystems of the
Asia-Pacific (excluding W Australia, E Australia, NE Australia and SW
Australia)
LME |
Fishery |
Gear |
Country fishing |
Trends |
Driving Force(s) |
Sea of Japan |
Mixed |
Bottom trawl (29%) |
Japan
(54%) |
Demersals
peaked in 1970s |
Climate |
Kuroshio Current |
Mixed |
Bottom trawl (33%) |
Japan
(81%) |
Small
pelagics and pelagics peaked in mid-1980s |
Climate |
Yellow Sea |
Mixed |
Driftnets
(26%) |
China
(72%) |
Medium
pelagics dominating with a peak in 1980 |
Climate |
East China Sea |
Mixed |
Bottom trawls (34%) |
China
(68%) |
Small
pelagics peaked in late 1990s |
Fishing |
South China Sea |
Mixed |
Bottom trawls (37%) |
China
(39%) |
Increasing
trends in all groups up until late 1990s |
Fishing |
Bay of Bengal |
Mixed |
Bottom trawls (34%) |
Myanmar (26%) |
All groups increasing |
Fishing |
Gulf of Thailand |
Mixed |
Bottom trawls (35%) Gillnets (11%) Purse seines (9%) Mid-water trawls (8%) |
Thailand (38%) |
Demersals
peaked in early 1970s
followed by a sudden decline during 1980s and 1990s |
Fishing |
Arabian Sea |
Mixed |
Bottom trawls (35%) |
India (62%) |
Pelagics
stable since mid-1980s but increasing recently |
Fishing |
Sulu-Celebes Sea |
Mixed |
Bottom
trawl (23%) |
Philippines (78%) |
Small
pelagics increasing with annual fluctuations |
Fishing Pollution Habitat |
Indonesian Sea |
Mixed |
Bottom trawls (26%) |
Indonesia (71%) |
Pelagics
peaked in late 1980s but stable since early
1990s |
Fishing Pollution Habitat |
Insular Pacific Hawaiien |
Mixed |
Purse
seines (37%) |
USA (85%) |
Small
pelagics cyclical peaking in late 1950s and late 1980s |
Climate |
N Australia |
Mixed |
Bottom trawls (31%) |
Indonesia (37%) |
Shrimp
catches cyclical |
Climate |
NW Australia |
Mixed |
Bottom trawls (26%) |
Australia (52%) Indonesia (25%) Thailand (21%) |
Small
demersals peaked in early 1970s and early 1990s |
Fishing |
SE Australia |
Mixed |
Bottom trawls (43%) |
Australia (67%) |
Small
pelagics peaked in early 1990s |
Climate |
New Zealand Shelf |
Mixed |
Bottom trawls (62%) |
New
Zealand (90%) |
Large demersals cyclical but stable since 1990 |
Climate |
This LME shows the typical longer-term cycle of pelagic fisheries, in which one group of species is often replaced by another. This decadal change is usually attributed to climatic cycles.
In 2003 there were four countries fishing in the area. Japan is the dominating country (81 percent), followed by China PR (11 percent), Korea RO (6 percent) and Taiwan POC (2 percent).
The trend for gear used in the area follows the trend of the catches, showing a large peak for purse seines in 1986. In 2003, 33 percent of the catch was taken by bottom trawl which makes it the main used gear in the area. It is followed by purse seines (25 percent) and mid-water trawls (13 percent).
Yellow Sea
The Yellow Sea is one of the most intensively exploited areas in the world, and has exhibited a pronounced change in ecosystem structure and "fishing down the food chain" effect. Due to overexploitation and natural fluctuations in recruitment, some of the larger-sized and commercially important species were replaced by smaller, less valuable, forage fish. When bottom trawlers were introduced in the early twentieth century, many stocks were intensively exploited by Chinese, Korean and Japanese fishers and all the major stocks were heavily fished in the 1960s, which had a significant effect on the ecosystem. Pacific herring and chub mackerel became dominant in the 1970s. Smaller-bodied and economically less profitable anchovy and scaled sardine increased in the 1980s and took a prominent position in the ecosystem.
Drift nets have always been a major gear in this LME but the catch from bottom trawls has also been increasing and in 2003 accounted for 25 percent of the catch.
The countries bordering the Yellow Sea take most of the catch - China PR 72 percent, Japan 11 percent and Korea RO 11 percent.
Bay of Bengal
Commercial species for the Bay of Bengal LME include anchovies, croakers, shrimp and tuna (yellowfin, bigeye and skipjack). Shrimp is a major export earner.
FAO data show a steady rise in total landings in all major groups since the 1950s. This appears to be largely as a result of increased marine landings reported for Indonesia, Myanmar, Malaysia and Bangladesh. The other Bay of Bengal counties (India, Pakistan, Maldives and Sri Lanka) have all reported losses in production in recent years, the greatest being from India. Increased competition and conflicts between small-scale and large-scale fishers and reports of declining catches and catch rates by fishers indicate that much of the Bay of Bengal is also over-fished.
There is an alarming increase in cyanide fishing in this LME's coral reefs for the lucrative live food fish markets in Hong Kong and Singapore. Mangroves and estuaries - critical fish spawning and nursery areas - are also under stress or threatened by pollution, sedimentation, dams for flood control (as in Bangladesh), and intensive coastal aquaculture. States bordering the Bay of Bengal rate overexploitation of marine resources as the number one problem in the area.
Catches coming from bottom trawling dominate the catch, although the LME is characterized by many small-scale fishers using a wide variety of gears.
As with the Yellow Sea, it is the countries surrounding the Bay of Bengal that record the greatest catches, although not only in their own EEZs. Thai trawlers are common in Myanmar and known to operate as far away as Bangladesh. There is also a relatively large high sea area that supports caches of tuna and other large pelagics that are also fished by several distant-water fishing nations.
Southeast Australian Shelf
The main species harvested are scallops (in Bass Strait), rock lobster (Tasmania), and abalone (Tasmania and Victoria) and finfish in the Southeast trawl fishery and shark in the shark fisheries. The long-standing trawl fishery has seen serial depletion of several of its important fish stocks, including eastern gemfish and more recently the deepwater orange roughy that is found associated with sea mounts. The fishery has been managed under individual transferable catch quotas (ITQ) since the early 1990s, but to date these do not appear to have been very effective in reducing overfishing in this multi-species fishery.
The main gear across the entire LME is bottom trawling, with other specialized gears catching scallops, lobsters and sharks (traps, dredges, and gillnets).
Trends in the trophic indices
The "Sea around us" project also provides calculations of the mean trophic level of the annual catches. In theory, changes in the mean trophic level reflect changes in the ecosystem structure, a higher value indicating a greater presence of larger predators, and vice versa.
In the Kuroshio Current LME, because this system is dominated by a few species groups, the change in trophic structure reflects the changing species mix. The low trophic index corresponds to the peak in the medium pelagic species group, mainly Japanese pilchards that are relatively low in the food chain. More recently, the switch to the relatively higher trophic level species can also be seen (Figure 29).
In contrast, the Yellow Sea LME shows less dramatic changes but a steady decline in the mean trophic level, consistent with "fishing down the food chain", is apparent (Figure 30). In the Bay of Bengal that has reported increased catches in all major groups, a decline in the mean trophic level can also be detected, suggestive of an overall shift in trophic structure in the Bay, or at least in the targeted species (Figure 31).
In SE Australia, the overall pattern in the mean trophic level is more similar to that of the Kuroshio Current, but in the Australian case (Figure 32) reflects changes in catch composition that occurred as a result of overfishing as well as management interventions. Catches of fish high on the trophic scale, such as Southern Bluefin tuna, were very high in the 1960s. The collapse of these catches and the introduction of strict quotas brought about a shift to lower food chain species after this time. However, since the mid-1980s the mean trophic index has increased again, driven by increased catches of sharks and species such as blue grenadier.
Ecosystem modelling
Fishery assessments based on ecosystem modelling have also been carried out in the region, especially in the eight States with extensive historic trawl survey data that allow better estimates on the amount of fish present in the sea. This approach is based on ecosystem modelling (e.g. Ecopath and Ecosim) that allows an analysis of the structure and function of whole ecosystems and how they have changed overtime. Christensen and his co-workers at the UBC are pioneering the approach and conducting analyses for the major LMEs. In the APFIC region they have concluded an analysis of the impact of fishing in the South China Sea.4 This analysis clearly showed that for this large sea, "fishing down the food chain" has occurred, indicating gradual replacement of large, long-lived predators by small, short-lived fish lower down the food chain, often referred to now as "trash fish". The only exception to these trends was off the coast of Brunei Darussalam where fishing pressure is much lighter than in other States, since it effectively has marine protected areas (MPAs) around its oil rigs.
Evidence gained directly from fisher's and fishing communities perceptions are perhaps the most difficult to describe and quantify but are always consistent with the evidence derived from other sources. There are many studies documented throughout the region where participatory assessments have been carried out, on a range of scales focussing on one or two selected villages to large organized fishing associations (e.g. trawl-owners associations). The APFIC Secretariat did not have the resources to provide a comprehensive review but in many cases the story seems to be the same - catches and catch per boat (gear, fishing lot etc.) have declined dramatically over the past 10-20 years. The status of the tuna species in the Western and Central Pacific and in the Indian Ocean can be seen in Table 17.
Figure 29
Mean
trophic level index for the Kuroshio Current LME
Copied from http://www.seaaroundus.org/lme/lme.aspx
Figure 30
Mean
trophic level index for the Yellow Sea LME
Copied from http://www.seaaroundus.org/lme/lme.aspx
Figure 31
Mean
trophic level Index for the Bay of Bengal LME
Copied from http://www.seaaroundus.org/lme/lme.aspx
Figure 32
Mean
trophic level index for the Southeast Australia LME
Copied from http://www.seaaroundus.org/lme/lme.aspx
Table 17
Status of tuna species
in the Western and Central Pacific and in the Indian Ocean
Species |
Central & Western Pacific |
Indian Ocean |
Skipjack tuna |
Underexploited |
Underexploited |
Yellowfin tuna |
Under/fully exploited |
Fully exploited |
Bigeye tuna |
Fully/overexploited |
Fully/overexploited |
Albacore tuna |
Underexploited |
Underexploited |
Swordfish |
Overexploited |
FAO has recently commissioned several participatory assessments across the region, including Timor-Leste, Viet Nam, Cambodia. As part of the response to the 2004 tsunami, FAO has supported rapid but limited assessments of the impacts of the tsunami on the fisheries resources of some affected areas of Sri Lanka, Indonesia and Thailand. The objective of these assessments was to inform the fisheries sector rehabilitation and reconstruction planning efforts.
Findings from these assessments to date indicate that in the perceptions of the fishers there has been no significant direct impact of the tsunami on the fisheries resources. However, localized impacts due to habitat modification (closing of lagoons, destruction of mangrove and reef etc.) have been reported.
In terms of long-term trends prior to the tsunami, fishers in all these countries reported declining catches and increasing numbers of vessels in the fisheries.
Because of the high population density in Asia, the per capita availability of freshwater is the lowest in the world and competing usages of freshwater have a major impact on fisheries. The main water resources for fisheries are the rivers and flood plains, natural lakes and man-made impoundments. The seasonal floodplains of States such as Myanmar and Bangladesh all have major fisheries. In contrast, Asia has relatively few natural lakes and most of these are confined to volcanic areas, notably in the Indonesian and Philippine archipelagos, and in northern India. The major exception is the Great Lake or Tonle Sap in Cambodia which occupies 200-300 km2 in the dry season, expanding to 10 000-12 000 km2 in the wet.
Over the centuries, reservoirs have been constructed in some States in Asia (e.g. Sri Lanka), but more recently construction of reservoirs for irrigation, hydropower and flood protection has become common in many parts of the Asia-Pacific region.
The reservoir resource in Asia is large and accounts for over 40 percent of the global large reservoir capacity. These range from large impoundments resulting from damming major rivers to small rainfed ponds. It has been estimated that developing States in Asia have 66.7 million ha of small to medium reservoirs with 85 thousand ha occurring in China.
Most inland fisheries are small-scale activities where the catch per craft (or catch per capita) is relatively small and the catch more often than not disposed of on the same day. The main exceptions are the industrialized fisheries in the lower Mekong Basin and the "fishing lots" in the Tonle Sap of Cambodia and the fishing "inns" of Myanmar. The lack of accurate reporting of these small-scale fisheries makes it difficult to assess their status but they are under considerable pressure from both the loss and degradation of habitat and from overfishing.
Freshwater fishes are reported to be the most threatened group of vertebrates harvested by man. It has been estimated by the World Resources Institute that half of the world's species were lost during the last century and that dams, diversions and canals have fragmented many major rivers, severely impacting fisheries resources.
Many of the inland water habitats have been altered and degraded. Rivers and floodplains, in particular, have been heavily impacted with the construction of dams, roads, channels and other irrigation systems. The training of water to reduce the impacts of flooding has probably had widespread effects on inland fisheries in the region, although the real impacts are poorly documented. Fishers regularly complain that catches are declining, but it is uncertain to what extent this is an effect of increasing fishery pressure or the loss of fishery resources through habitat degradation and changing water flow regimes.
Major changes in the way large systems function have enormously altered some areas by greatly reducing the seasonal "flood pulse" that previously resulted in large areas of land becoming flooded during the wet season. This has impacted on the ability of many species of fish to migrate to their spawning grounds and has also altered the flow pattern with accompanied habitat changes (e.g. running water to lakes). Some mitigation attempts have been made in terms of fish ladders to allow fish to migrate around dams but their success compared with original conditions is unknown.
Changing agricultural patterns including irrigation development and the increased use of chemicals and pesticides in intensified agricultural production have all had some impact on wild fishery resources.
As in the marine environment, changes in species composition are also occurring. Catches of large, long lived species such as the giant catfish and large cyprinid species are becoming rare and there is evidence of "fishing down the food chain" in some inland areas. In the Mekong River, for example, the giant catfish (Pangasianodon gigas) has now become extremely rare and endangered.
On the other hand, the status of some inland fishery resources has been enhanced through stocking programmes, introductions of exotic species, habitat engineering and habitat improvement. Stock enhancement is an integral part of most inland fisheries in the Asia-Pacific region and is increasing, particularly where some sort of access restriction or user rights are in place. In general, fisheries in large lakes and rivers depend on naturally recruited stocks and the economic viability of stock enhancement has not been demonstrated in any Asian State. In floodplain depressions and in small water bodies, stock enhancement has proven to be very successful. These cultured-based fisheries are seen as a way forward in China PR and many States in the region.5
Of particular importance to many States of the Asia-Pacific region are rice-field fisheries that either depend on natural introduction of wild fish or stocking fish, either simultaneously or alternately with the rice crop (probably more correctly defined as aquaculture). The fish are important for local consumption and marketing, and support rural livelihoods in developing States. It is particularly important for food security as it is the most readily available, reliable and cheapest source of animal protein for farming communities as well as the landless. This importance is generally underestimated and undervalued. It is reported that the availability of this aquatic resource is declining. Anecdotal evidence from China, Viet Nam, Lao PDR, Cambodia, Thailand and elsewhere suggests that it is considerably more difficult to find such food now than a decade or so ago. This is a result of increasing demand through human population increases and activities such as the use of pesticides, destruction of fish breeding grounds and the use of illegal fishing methods such as poisons and electro-fishing.
1 Silvestre, G.T., Garces, L.R., Stobutzki, I., Ahmed, M., Santos, R.A.V., Luna, C.Z., Lachica-Alino, L., Christensen, V., Pauly, D. & Munro (eds.) (2003). Assessment, management and future directions for coastal fisheries in Asian States. WorldFish Center Conference Proceedings 67, 1 120 pp.
2 Large Ecosystems of the World: http://www.edc.uri.edu/lme/
3 UBC large Marine ecosystems: http://www.seaaroundus.org/lme/lme.aspx
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