Habitat and Biology
Climatic zone: Tropical; Temperate; Polar.
The northern part of the area coincides with the Bay of Bengal and is located in the tropical monsoon belt, with sea surface circulation reversing in the monsoon period (clockwise from January to July, counter-clockwise from August to December) (Lamboeuf, 1987). In addition to the monsoon cycles, this region is affected by storm surges and cyclones. Moreover, the presence of large rivers (such as the Ganges–Brahmaputra and the Irrawaddy Rivers) strongly affects the water salinity in large parts of the bay. They provide considerable sediment loads to the shelves and lowered salinities.
Water Area Overview
The Eastern Indian Ocean covers an area extending west to 80°E, south to 55°S and mainly delimited by landmasses in the north and east (Figure B9.1). These landmasses include the countries of the Bay of Bengal in the north, and Malaysia, Indonesia and Australia in the east. The main shelf areas include those of the Bay of Bengal, the Gulf of Martaban and the narrower shelf areas on the west and south sides of Indonesia and Australia, for a total of 2.37 million km2 of shelf area.
Because of its extensive latitudinal (north–south) span, this region includes tropical, subtropical and temperate regions. Tropical species and communities are found mainly in the north and central parts, while temperate species are found in the southern latitudes of west and south Australia.
|Figure B9.1 The Eastern Indian Ocean (Area 57) |
Considered a single stock: No
On the shelf of the Bay of Bengal, the main type of demersal fish communities can be largely correlated with the type of bottom on which they occur. On muddysoft bottoms, sciaenids (drums) dominate within a diverse and complex community including polynemids, sea catfishes, shads, hairtails, various flatfish species and crustaceans. On sandy shelf bottoms, such as off the Thai coast of the Andaman Sea, slipmouths, goatfishes, sciaenids and lizardfishes dominate.PROFILE OF CATCHES
The Indian Ocean shelves of Indonesia (Sumatra and Java) are relatively narrow and steep, mostly with coralline and sandy bottoms. The northern part of this area was affected by the tsunami in 2004. There is evidence of coral reefs having been affected by this event, through deposits of debris and siltation, as well as tectonic uplift. However, overall fish productivity in this region does not seem to have suffered. The south coast of Indonesia and the north coast of Australia are in the path of a low-salinity warmwater current flowing west from the Pacific into the Indian Ocean, the Indonesian Throughflow.
Overall, shelves have relatively low productivity, which is also reflected in the low abundance of fish. The southward flow of the warm and low-nutrient Leeuwin Current allows tropical fish fauna off west Australia to be found farther south than anywhere else in the world. However, this current is also responsible for the low productivity of these waters. Farther south, along the southwest and south coasts of Australia, the climate becomes more temperate with high rainfall in the west.
The oceanic regions are characterized by low overall productivity except for higher primary productivity resulting from equatorial upwelling. However, this is a more limited phenomenon in this area compared with the Atlantic and Pacific Oceans. The primary productivity of the Bay of Bengal is considered lower than that of the Arabian Sea, largely as a consequence of stronger stratification and lack of upwelling (Prasanna Kumar et al., 2002).
The countries surrounding the northern and central parts of the region (Bay of Bengal and western Indonesia) include some of the largest populations on earth, with India, Indonesia and Bangladesh being among the world’s top ten. The coastal population living around the Bay of Bengal is estimated to be about 450 million, with fisheries employing about 4.5 million people, of whom 2.2 million are fishers. Marine living resources are extremely important for the livelihoods of millions of people and their communities, in particular as a source of food.
Despite the increasing trends in the total catches reported from this region (Figure B9.2), there is a general perception that marine living resources are overexploited and critical habitats are becoming degraded, particularly in the northern area. Key factors that contribute to this situation are socio-economic, such as those resulting from population growth and increasing migration to the coast, and lack of alternatives for securing food, livelihoods and shelter in the poor rural coastal communities. Other factors are largely institutional, such as poor enforcement of policies, laws and regulations. Climate change resulting in ocean acidification, sea-level change (rises in most areas); and increased frequency or intensity of storms and cyclones is also considered as an emerging key concern.
The southern area is sparsely populated. Here, key environmental concerns include the impact of increased shipping activities, development of oil and gas deposits, mining, nutrient inputs from land-based activities and tourism. These concerns are addressed through a strong legislative framework combined with an advanced environmental monitoring system. Climate change has been recognized as one of the most important factors affecting fisheries in this region (Irvine et al., undated).
Catches in Area 57 have increased steadily since 1950 (Figure B9.2,Table D10). The rapid increase began in the 1970s and is still continuing, with the total catch exceeding 5 million tonnes in 2002. Since then, the total catch has increased to more than 6.5 million tonnes in 2009. The majority of this increase continues to be comprised of the “marine fish NEI” group and the five ISSCAAP fish groups that together accounted for almost 85 percent of the catches in 2009. The largest individual contribution (43 percent) remains marine fishes not identified (Group 39), followed by miscellaneous pelagic fishes (Group 37) at 12 percent and miscellaneous coastal fishes (Group 33) at 11 percent. The large contribution that these groups make to the total is a reflection of the multispecies nature of most fisheries in the region, particularly those in the tropical and subtropical areas. However, this is also the result of the way national reporting systems are organized. Countries have tended to pull statistics together into larger categories and disregard the advantages that a higher resolution in the statistics would bring. This is particularly in relation to the insights it would provide as a basis for policy-making. The other major groups include herrings, sardines and anchovies (Group 35) at 8.4 percent, and tunas, bonitos and billfish (Group 36) at 7.9 percent.
For the purpose of this review, Area 57 was divided into a northern area (Bay of Bengal and the Indian Ocean side of western Indonesia, including coastal and oceanic adjacent waters) and a southern area (mainly west and south Australia and adjacent oceanic waters). This was done to reflect the different climatic and oceanographic conditions as well as the types of fisheries and data availability.
|Figure B9.2 Annual nominal catches by ISSCAAP species groups in the Eastern Indian Ocean (Area 57) |
Much of the catch in the northern area comes from coastal fisheries. These fisheries are typically multispecies and multigear, and their catch is mostly used for local consumption. Fish represent one of the few affordable sources of protein for people in the region. The high proportion of the marine fishes not identified (ISSCAAP Group 39) in the catch is a reflection of both the types of fisheries that operate here and the relatively weak fishery statistical systems that exist in many of the countries of the region. Croakers (Sciaenidae), sea catfish and pony fish remain the largest components of the miscellaneous coastal fishes catch (Group 33). While catches of these species groups have largely stabilized in the past seven years (Figure B9.3), the catch of the entire group increased in this period from about 500 000 tonnes to 700 000 tonnes in 2009 (Table D10).
|Figure B9.3 Annual nominal catches of selected species in ISSCAAP Group 33, Eastern Indian Ocean (Area 57) |
For the herring, sardines and anchovies (ISSCAAP Group 35), the catch of anchovy (Stolephorus spp.) and Indian oil sardine(Sardinella longiceps) increased until the end of the 1990s. Since this time, the anchovy catches have remained in the range of 53 000 to 82 000 tonnes. In contrast, the oil sardine declined from more than 80 000 tonnes to 13 000 tonnes in 2003, but has since recovered to some extent with catches of more than 60 000 tonnes in 2008 and 2009 (Figure B9.4).
The total catch of Group 35 has continued to increase, rising from 384 000 tonnes in 2002 to more than 550 000 tonnes in 2009, with much of this increase due to the clupeoids NEI (Figure B9.4).
|Figure B9.4 Annual nominal catches of selected species in ISSCAAP Group 35, Eastern Indian Ocean (Area 57) |
The catches of the miscellaneous pelagic species (ISSCAAP Group 37) increased from 524 000 tonnes in 2002 to 794 000 tonnes in 2009 (Figure B9.5). The major components for this increase include the catch of Indian mackerels (Rastrelliger spp.), which recovered from the downturn in the early 2000s to be 235 000 tonnes in total in 2009. There has also been a continual increase in the other miscellaneous pelagic catch, which has risen from 200 000 tonnes to 300 000 tonnes. The total catch of the miscellaneous demersal fishes (ISSCAAP Group 34) has been relatively stable for the past decade, which is reflected in the catches of the two largest components of this group (Figure B9.5).
|Figure B9.5 Annual nominal catches of selected species in ISSCAAP Groups 34 and 37, Eastern Indian Ocean (Area 57) |
The catches of shads (ISSCAAP Group 24) seem to have stabilized. This statistical group includes several species, with the hilsa shad (Tenualosa ilisha) making up most of the catches (almost 200 000 tonnes in 2007). Catches of the second-most important species in this group, the kelee shad (Hilsa kelee), have dropped substantially from almost 50 000 tonnes to less than 20 000 tonnes in more recent years. This drop is not visible in Figure B9.6 given the lower level of catches of this species as compared with the hilsa shad.
Cephalopods (ISSCAAP Group 57), tunas (ISSCAAP Group 36) and, to a lesser extent, shrimps (ISSCAAP Group 45) appear to have all reached a plateau in the past decade (Figure B9.6).
The catches of tuna, which are one of the major export-earning fisheries for the region, are now oscillating around 500 000 tonnes. Skipjack tuna make the largest species contribution to the catch with 100 000–135 000 tonnes. In comparison, the catch of yellowfin has now declined from its peak in the late 1990s to be almost 70 000 tonnes/year. The catches of cephalopods, which is also a major commercial fishery, have not expanded as expected, with the total remaining close to 100 000 tonnes since 2002. This is despite an expansion in fishing activities from mainly around Thailand into Malaysia and Indonesia. The catch of shrimps, which appeared to peak at 270 000 tonnes in 2000, has rebounded to now be above 300 000 tonnes (Figure B9.6). The majority of this comes from the continued increase in catches of the giant tiger prawn (Penaeus monodon) and the recovery of the catch of natantian decapods (Table D10).
|Figure B9.6 Annual nominal catches of selected species in ISSCAAP Groups 24, 36, 45, 57 Eastern Indian Ocean (Area 57) |
The main fisheries in the southern area of the Eastern Indian Ocean are off the west and southwest of Australia. Total catches in the 1970s were about 60 000 tonnes, increasing to an initial peak of 127 800 tonnes in 1993 before fluctuating and then declining to 110 000 tonnes in 2001. In the last decade, the catch again increased to another peak of 160 000 tonnes in 2004 before again declining to 110 000 tonnes in 2009. This total catch is considerably less than in the northern areas and reflects the very low nutrient content of the waters occurring in this region.
The most important groups in this region in terms of economic value and export earnings are the spiny lobsters, abalone and tuna (ABARE, 2009). Lobster catches (other ISSCAAP groups) increased slowly from 6 000 tonnes in the 1950s and gradually reached a peak of almost 20 000 tonnes in 2000 before declining to 11 000 tonnes in 2009. These recent reductions reflect increased management restrictions introduced in response to a series of poor recruitments that have affected both lobster species (DOF, 2010). Abalone catches have been relatively stable at about 5 000 tonnes/year for the past ten years despite an outbreak of a disease in one of the regions. The tuna captured in this region are mostly southern bluefin tuna, which had a peak catch of 20 000 tonnes in 1982. After that time, TAC quotas were introduced when assessments indicated that the stock was overexploited. A series of quota reductions have been introduced in order to recover the stock towards an interim rebuilding target reference point (CCSBT, 2009). Much of the current quota of only 4 000 tonnes of southern bluefin tuna caught in this area is being value-added through sea ranching (ABARE, 2009).
The catches of herrings, sardines and anchovies (ISSCAAP Group 35) form the largest volume catch for this region. The catch peaked at 17 800 tonnes in 1988 and then subsequently declined to 4 377 tonnes in 1999 after two very large mass mortalities of pilchards occurred across the entire southern and lower east and west coasts of Australia in the mid- and late 1990s (Jones et al., 2008). The stock has subsequently recovered in most locations (Ward, Ivey and McLeay, 2007; Gaughan et al., 2008) with catches for the last six years having increased substantially to above 30 000 tonnes. Most of this catch is used as food for tuna ranching.
The other group contributing to the variations in overall catch for this area is scallops (ISSCAAP Group 55). There were two major peaks in scallop catches (more than 25 000 tonnes) in 1983 and 1993 and a minor peak of 12 000 in 2005. In between these peaks in catch have been periods where the annual catches sometimes declined to less than 2 000 tonnes. This boom–bust cycle has been experienced by these scallop fisheries over a long period. Recruitment events in scallops appear to be very episodic, but there is increasing evidence that overfishing can affect the frequency and intensity of these events (DOF, 2010).
Management unit: NoNorthern area
The Bay of Bengal Large Marine Ecosystem Project has recently completed a draft transboundary diagnostic analysis of this region to identify key sustainability issues as well as their causes.Southern area
Overfishing is a key issue in this region, with excess fishing capacity in many of the region’s coastal fisheries reducing productivity and threatening long-term sustainability.
Fisheries management within the region encompasses a range of situations and scales, from customary systems of marine tenure practised by coastal communities, to national fishery governance and participation in management of tuna stocks of the Indian Ocean. Despite the shared nature of many stocks within the Bay of Bengal region, there has been no effort in the past to assess and manage resources. The Bay of Bengal Large Marine Ecosystem Project is now attempting to address these issues. In some countries, customary rights are still in place, but these have often been replaced by open access. This has led traditional user rights to be eroded in favour of commercial fisheries development.
A number of destructive fishing practices, such as using dynamite and toxins to capture fish, small-mesh net fishing for prawn larvae, and live coral mining have been common and widespread in this area. Weak governance (inadequate monitoring and control systems, weak fisheries management decision-making processes, poor information on resources, and limited national and regional capacity) has also contributed to coastal fish stocks being under serious threat with the present level of exploitation and the types of fishing methods used. It should also be recognized that, in addition to fishing pressure, fishery resources are also threatened by other factors such as destruction of the mangrove ecosystems for timber or construction of shrimp ponds, pollution from land-based activities and coastal development.
The Bay of Bengal Large Marine Ecosystem Project is addressing the above fisheries governance and environmental issues and it is hoped that the above negative trends will be reversed. The project has adopted the ecosystem approach to fisheries as the framework to promote sustainable fisheries. As part of this effort, fisheries and environmental information is being compiled in order to formulate advice to the government agencies concerned.
The most valuable fisheries in the southern area include rock lobster, abalone, prawns and tuna, which are all export fisheries. The fisheries management responsibility for these generally falls under the relevant state government agency (COA, 1980). The exception is for tuna, which is managed by the Government of Australia but as part of the Commission for the Conservation of Southern Bluefin Tuna (CCSBT). The CCSBT commission also includes Indonesia, Japan, the Republic of Korea, New Zealand, and the fishing entity Taiwan Province of China, plus a number of cooperating non-member countries (the Philippines, South Africa and the EU). The CCSBT is responsible for setting the TAC for southern bluefin tuna and its allocation among members.High seas
All commercial fisheries in this region now have at least some form of limited entry management. Most have specific allocation of tradable fishing rights or access either in the form of catch and or effort (Rogers, 2000). In addition, in Australia, all export fisheries and all managed fisheries must now be assessed regularly against the “Guidelines for ecologically sustainable management of fishing” in order to meet the requirements of the Environment Protection and Biodiversity Conservation Act 1999, which is administered by the Federal Environment Agency (DEWR, 2007).
In tuna fisheries in the Indian Ocean, compliance seems to be the main problem. At its most recent meeting (March 2011), the IOTC Compliance Committee meeting, identified several shortcomings, especially regarding the tracking of catch data for science and management. In particular, there is a need to improve the information from the northeast Indian Ocean coastal States. While the IOTC is moving towards also considering bycatch and ecosystem issues relevant to these fisheries, there seems to be still some reluctance to comply with conservation and management proposals made at the commission level. For example, there is still no prohibition of retention on board of endangered species such as hammerhead or oceanic white tip sharks. Moreover, a proposal for mandatory collection of data on bycatch of endangered species by the gillnet fisheries, mainly in the northern part of Area 57, was downgraded to voluntary measure at the above meeting. Illegal fishing is also a major issue in the region and, to date, no serious effort has been made to combat it. This situation undermines the region’s capacity to implement sustainable management efficiently.
Biological State and Trend
To access all FIRMS State and Trend summaries available for this Area, please look at: Table D10
Status and Trend Summaries (extracted from reports)
shows the assessments for Area 57. There is a difficulty in obtaining stock assessments for individual stocks and species within Area 57. Consequently, drawing more general conclusions about the status of individual stocks in the whole area are not possible. Thus, the results presented in Table D10
are based on regional catch data available in the FAO FishStat database and follow the methodology presented in this review. Stock assessments are available for the Australian fisheries, but because of their limited share in the totals for the region, they are not used for the regional assessment. Although very approximate, the assessments presented in Table D10
can still provide an indication of regional trends.
Of a total of 43 species and species groups assessed, 17 percent are non-fully exploited, 58 percent are fully exploited and 21 percent are overexploited. Among the overexploited groups of concern are the kelee shad, the largehead hairtail, sardinellas, silky shark, rays, penaeid shrimps, cephalopods and octopuses. Most of these fisheries take place in the northern area.High seas
The main targets in the high seas of Area 57 are tuna and tuna-like species. Distantwater fleets from Asia (China, Japan, the Republic of Korea and Taiwan Province of China) and from Europe (primarily France and Spain) are playing a major role. As most of these high seas resources are shared throughout the Indian Ocean, the resource status adopted here is based on the results of the 13th session of the Scientific Committee of the IOTC (IOTC, 2011) covering whole stocks.
Yellowfin tuna (Thunnus albacares) is likely to be currently in, or approaching, an overfished state and overfishing has probably been occurring in recent years. The IOTC has recommended that catches not exceed 300 000 tonnes for the whole Indian Ocean. However, bigeye tuna (Thunnus obesus) and albacore (Thunnus alalunga) do not seem to show signs of overexploitation. Skipjack tuna is a species considered to be highly productive and robust to fisheries. Within Area 57 (and the Indian Ocean as a whole), it can still be considered as moderately exploited in the region. The IOTC advises government agencies of member countries to monitor this species closely as there are signs of local overexploitation.
Stock status of other tuna and tuna-like species (such as billfishes) is highly uncertain because of lack of data and formal assessments. Catch data seem to indicate a situation of the whole group of “other tunas, bonitos, billfishes, etc.” being fully exploited.
Source of information
Marine and Inland Fisheries Service, Fisheries and Aquaculture Resources Use and Conservation Division. FAO Fisheries and Aquaculture Department “Review of the state of world marine fishery resources” FAO FISHERIES AND AQUACULTURE TECHNICAL PAPER.
No. 569. Rome, FAO. 2011.
The bibliographic references are available through the hyperlink displayed in "Source of Information".ACKNOWLEDGEMENTS
The authors wish to thank Simon Funge-Smith (FAO Regional Office for Asia and the Pacific) and Rudolf Hermes (Bay of Bengal Large Marine Ecosystem Project, BOBLME) for their valuable comments and revisions of the initial draft of this chapter.