page 1
page 2
page 3
page 4 page 5
page 6
page 7
page 8
page 9
page 10
page 11
page 12
page 13
page 14
page 15
page 16
page 17
page 18
page 19
page 20
page 21
page 22
page 23
page 24
page 25
page 26
page 27
page 28
page 29
page 30
page 31
page 32
page 33
page 34
< prev - next > Fisheries Farming fish and aquaculture food_livelihood_and_freshwater_ecology (Printable PDF)
It is feared that these natural resources are in decline (in both diversity and number), thus jeopardizing the prospects for
sustainable development. The transformation of the aquatic habitats and loss of wild species is increasing this vulnerability of
Bangladesh's food production systems. It is further undermining the traditional rights of the rural population to open access to
common property resources. The sustainable development of millions of people whose nutrition and livelihood depend on
continued open access to the common property resources of the flood plain, is inextricably linked to protecting and
conserving Bangladesh's renewable aquatic biological resources.
Small Indigenous Fish
Of the 260 species of freshwater fish in Bangladesh, over 140 species have been classified as "small indigenous species"
(SIS). The term SIS would seem to be a recent re-interpretation of the Bangla word chotomach (literally, small fish), as
opposed to boromach (literally, large fish). Chotomach are generally regarded as the small fish eaten by poorer households
as a subsistence food. By contrast, boromach are generally considered to be a commercial crop, either wild caught species
(like Hilsa) or produced in ponds (like the Indian major and Chinese carps).
However, equating the term SIS too closely with chotomach can be misleading. According to recent studies, SIS are not
necessarily small: some species may grow up to 9 inches (or larger). Also chotomach is now a term commonly used for
small exotic species (e.g. Chinese carps and tilapia), whereas SIS applies only to indigenous fish species. However, SIS
(like chotomach) make a significant contribution to the diet, and nutritional surveys show that around 80% of the fish eaten in
Bangladesh are small indigenous species. Their significance is however often overlooked by many observers.
The other value of SIS is that collectively they provide a flotilla of flagship species. Their relative abundance is an indication
of a healthy ecosystem, whilst a decline in diversity and numbers warns that all is not well.
Human Impact
Freshwater ecosystems are highly vulnerable, and the impact of human activities can be profoundly damaging on them. In
Bangladesh human interventions are the root cause of destructive impacts in 3 main areas: over exploitation of resources;
habitat destruction and pollution. Also the introduction of several species of exotic fish to Bangladesh over the last 3 decades
is providing an additional threat, of as yet unknown consequence.
Over exploitation: Population growth over the past three decades has increased pressure on aquatic resources: the need to
provide both food and water to a growing population as well as a medium for domestic waste disposal is stretching the
productive and self renewing capacity of aquatic resources to their limit. Although fish production over the past decade has
shown an increasing trend, indications are that individual catch rates (catch/unit effort) have declined.
According to official sources (Government of Bangladesh), total fish production has increased from some 7.71akh tonnes in
1984, to 13.7Iakh tonnes in 1996. Over this period catches from freshwater capture fisheries have increased by a factor of
about 1.4, from 4.6 to 6.6 lakh tonnes. By contrast aquaculture production has increased by more than 3 fold, from 1.23 to
4.2 lakh tonnes. Over the same period, the population has increased from around 90 million to 115 million. Fish production
would therefore seem to have grown at a faster rate than the population. What is not known is how much longer these
production increases can be sustained. Fishing pressure has increased many-fold over the last decade, due to the entry of
fishermen from outside the fishing sector, and through the use of more intensive (and non-selective) methods of fishing.
Increasing competition for limited (and increasingly valuable) resources has also encouraged the use of non-selective fishing
techniques such as the "current Jal", exacerbating an already acute problem.
Another potentially negative factor which this success story masks, relates to exotic species and genetic diversity. A
significant proportion of the production increases has been based on the introduction of exotic species (mainly Chinese carps
and Tilapia), which have now become a part of Bangladesh's freshwater fisheries. More recently, the introduction of African
Magur, a large predatory fish, has set alarm bells ringing. There are no detailed record either of when these introductions
were made, or the extent of their colonization, and its impact on the freshwater ecosystems. As most of the increases in
aquaculture production have come from hatchery produced fish of exotic origin, it is possible that inbreeding and stock
deterioration have taken place. This could result in negative future effects such as retarded growth, reduction in reproduction
rate, and reduced disease resistance.
There are two further issues of concern which relate to aquaculture production. Firstly, hatchery produced fish have been
stocked extensively in flood plains. In addition to the negative impact of exotic species on indigenous species (e.g. through
competition and perdition), this could also cause the weakening of the gene pool of wild fish. Secondly, SIS are considered
"weed fish" by the advocates of the blue revolution. Thus, most of the aquaculture systems promote poisoning of ponds