Please provide the following details on the origin of this report

4. The Government has undertaken a project for preparation of Biodiversity Strategies and Action Plan (BSAP). GEF has approved the project for funding. The project will be placed for implementation soon. Strategies and actions for taking measures on the alien invasive species in Bangladesh will be incorporated in the BSAP.

Professor Mahmud-ul-Ameen

Department of Zoology, Dhaka University


Introduction:

Biodiversity is the basic biotic resource that sustains all human life-support systems on this earth (Kim 1993). Continuance of rich biodiversity is an assurance for our survival. However, it is declining rapidly and is a cause of alarm and distress all over the world. The major causes for this decline are:

2. Over exploitation of biotic resources.

3. Invasion of alien species.

4. Pollution.

5. Climate change.
This workshop will address the problem of invasive alien species and try to develop some guiding principles for preventing negative impacts of such invasion. Before proceeding further, let us examine the definitions of a couple of relevant terms developed by IUCN.
Alien species:

"is a species, subspecies of lower taxon occurring as a result of human agency in an area or ecosystem in which it is not native."

- "Belonging by nature or origin to another part of the world; brought in from abroad; foreign; strange".

"is an alien species which colonizes natural or semi-natural ecosystems, is an agent of of change, and threatens native biological diversity". It should not, however, be confused with those species which in nature colonize newly forming ecosystems in succession, subordinating the previously dominant species.

1. Precautionary approach as the pervading principle.

2. Sharing of relevant information.

3. Research and management of invasives.

1. 
   Utilization of a vacant niche in the native ecosystem(s).
   
2. 
   Increasing food production.
   
3. 
   Quality improvement of sport, like fishing and hunting.
   
4. 
   Control of undesirable species considered as pest, pestilence, weed, etc. as a tool for biological control.
   
5. 
   Decorative or ornamental species as pets, aquarium fish, etc.
   

The rationale for introduction of the listed alien or exotic fish into Bangladesh was to augment fish production in the country as a means to increase the per capita fish consumption. Let us discuss some of the fishes in Table 1. Some of these were treated in a chapter: "Prospects of Exotic Fish Culture in Bangladesh" of the book on fisheries Resources by Ameen (1987, pp. 184-209)

The arguments in favor of the introduction were:

2. They are highly fecund and produce a large number of fry.

3. They grow quickly, So, production is high.

4. They can be cultured in shallow, seasonal water bodies and ditches.

5. Said to be resistant to pesticides and other toxicants.

6. Tolerant to a wide range of temperature and salinity.

1. 
   Their prolific breeding surpasses the carrying capacity of the waterbody leading to stunting of individuals. Thus points I and 2 above negates point 3.
   

2. 
   There are many indigenous species which grow in shallow, seasonal waterbodies and ditches. These do not require annual stocking. They, in addition, control many pests.
   

3. 
   That they grow quickly and the argument that tilapia production is higher is disputed and evidence is scarce (Ameen et al. 1984, Ameen 1985a, b; 1987).
   

4. 
   Population of many indigenous small fish species has declined due to the invasion of tilapia and nilotica in our water bodies.
   

5. 
   Comparative production: Ameen et.al. (I984) demonstrated that in miniponds and small water bodies production of small irdigenous fishes are at par with tilapia production.
   

6. 
   Genetic erosion and loss of species diversity: Replacement / suppression of indigenous fish species has made our "gene rich" fish population "gene poor". Even species diversity is threatened. Some 57 species out of c.300 freshwater fish species have become vulnerable / endangered / critically endangered in Bangladesh (IUCN, 1999: in press).
   

7. 
   In fish landings from Kaptai lake tilapia had no contribution between 1976 and 1985 (ARG 1986), but in recent years they are contribution c.9% of the total landing while the contribution of major carps has declined (C.U 1999: M.Sc. Thesis of 1995 Exam., Department of Zoology).
   

8. 
   The consumable weight relative to total weight of indigenous fishes is higher than tilapia. Hard bony part is relatively high in tilapia. The soft bones of small indigenous species are consumed and are source of nutritive vitamins.
   

Tilapia may be recommended for those areas where native species are scarce of absent, e.g., in countries like Israel. In a country like Bangladesh which is rich in fish biodiversity, introductions should be very restricted.

Predation and voracity of this catfish is legendary. People do not like the meat of larger- sized fish of this species. Now there are attempts to keep its size smaller for easy marking. Production per unit area of acarnivore is much less that a herbibvore (theoretically as much as 80-90% less) from food chain computations. African magur escaped to the open waters during the floods and reported to have consumed even ducklings, let alone other fishes. This will lead to great reduction of population of the indigenous species, endangering their future existence. Therefore, increasing fisheries production to meet the national demand emphasis should be on the culture of dominantly herbivore species rather than on carnivores.

Culturable, popular and high-priced. Not extensively cultured because of secrecity of fry. Breeding through hy hypophysation achieved. But survival after yolk-sac stage critical and large scale mortality occur after this stage. Remedy: Supply of proper food (of the required size).

· Explore the possibility of culture of gang magur / kani magur (Plotosus canius).

• 
  Grows very fast, if provided with adequate grass and other vegetable food.
  
• 
  May be used effectively for aquatic weed control.
  
• 
  Its faccal matters manure ponds.
  
• 
  Does not compete with other cultured species.
  

Disadvantages:

• 
  Scarcity of grass during dry months
  
• 
  Competes with cattle in Bangladesh where natural cattle feed is in very short supply.
  
• 
  Response to hypophysiation unpredictable.
  
• 
  Apprehension of grazing on rice plants if escapes to open waters. (Corroborated by news of it destruction of paddy fields in media). However, cannot be a permanent nuisance because the possibility of its breeding in natural waters of Bangladesh is negligible because of high ambient temperature.
  

• 
  Breeds naturally in confined waters in Bangladesh conditions.
  
• 
  Hardy and disease resistant.
  
• 
  Release nutrient by turning bottom mud.
  
• 
  P.G. is more potent and extensively used for hypophysation.
  
• 
  Suitable for cage and pen culture.
  

Disadvantages:

• 
  Destroys pond embankments, makes water turbid by turning up mud.
  
• 
  Attains maturity early, thereby growth retarded
  
• 
  Tend to study at high density.
  
• 
  Eggs are easily infected by fungus.
  
• 
  Difficult to harvest with s' ',et.
  

Fast growing, planktivore and does not breed in ponds. They are easy to harvest. Silver carp feed mainly on small phytoplankton, as small as 30-40 up, which catla can not consume. Do not spawn in confined waters, but respond well to hypophysation.

• 
  Competes with catla.
  
• 
  Long distance transportation of fry needs special care.
  

At present the problem with silver carp, to my experience, is stocking it in densities higher than its niche can support and thereby putting catla to unnecessary competition. The rate and ratio of different species in composite culture should be carefully assessed.

Stock enhancement schemes for the open water fisheries provides some important information. Tsai & Ali (1987) reported that contribution of major carps in the beels of Sylhet-Mymensingh basin decreased considerably between 1963 and 1984. The major carps contributed 67% of the totaI in 1967, 50% in 1973,and 4% in 1984. Consequently DoF undertook several projects to enhance stocks in the openwaters by releasing fry of major carps and chinese carps into them. Some computed data from the reports on Hail haor project is shown in Table 2 and for five beels in Fig. 1.

Recommendations:

1. 
   Information on the biology of alien species and their probable impact on the indigenous biodiversity has to be evaluated on a pilot scale before listing as probable for introduction.
   
2. 
   Strict quarantine before entry into a new country / region.
   
3. 
   Dominantly herbivore species should get preference in selection for culture.
   
4. 
   No pesticide should be allowed in any openwater / natural aquatic ecosystems.
   
5. 
   Indigenous species should be preferred for stocking and given similar treatments as given to exotics.
   
6. 
   The term "trash fish" in polyculture should be dropped. They should be included in the production system and not belittled,
   
7. 
   Rate of stocking should be appropriately revised according to the carrying capacity (enhanced due to inputs), which should be determined if not know already. (For details see Ameen 1984, 1993).
   
8. 
   The ratio of stocking surface, column and bottom feeders should be relevant to the natural carrying capacity of these niches. (For details see Ameen 1984, 1993).
   

Does not include decorative aquarium species.

DoF =Department of Fisheries

P.C. = Personal communication

• 
  For details the Tables will be found in Ameen 1994 (Limnology and Fish Management)
  

INTRODUCTION

BACKGROUND

1. 
   Precautionary approach as the pervading principle
   
2. 
   Sharing of relevant information.
   
3. 
   Research and management of invasives.
   

Combating the invasive species in Bangladesh will be very difficult because of lack of awareness and proper initiatives. However, by influencing excessive harvest and discouraging the cultivation of these species may reduce the impact. No species should be introduced without evaluating their detailed life history, probable impacts, and probable benefits in Bangladesh. No predatory species should be introduced. And lastly, people should be motivated to cultivate indigenous species. The indigenous species of an ecosystem evolves after a long history of evolutionary process. Hence, it is extremely inter-linked and balanced with all the local biotic and abiotic factors. The indigenous species in no way replaceable with the alien invasive.