Dr. Md. Kamal
Consultant, FAO/UNDP
1. Introduction
Shrimps are a major foreign exchange earner for most Asian countries including Bangladesh. A considerable quantity of by-catch hauled up with shrimp is discarded in the sea. In most shrimp fisheries, the by-catch comprises 80–95 percent of catch. It has been estimated that, in 1988, approximately 100,000 –130,000 MT of shrimp by catch was discarded by the east coast fleet of India (BOBP, 1991). The accurate information on by-catch especially by Bangladesh trawlers is poorly-known. Currently about 50 trawlers (both shrimp and finfish) of the country are operating in the Bangladesh sea water, harvesting shrimp and some selected high commercial value fish species like pomfrets and croakers. The post-harvest losses from discarded by-catch by these trawlers are estimated to be around 25,000–30,000 mt. annually in addition to some discards occur in artisanal fisheries (INFOFISH, 1986; FAO-TSS-Mission Report, 1991).
1.1 The Species and Size Distribution of By-Catch:
The information available on the species and size distribution of the discarded by-catch is general rather than specific. The mesh size used by these trawlers is between 40–45 mm at the cod end. The composition of by-catch is a mixture of small fish over 10–15 cm, mostly comprises juveniles of economic demersals and pelagics, as well as invertebrates. According to BOBP report (1991) in the east coast of India, everything less than 20 cm is discarded (80–90% of the catch volume).
BOBP conducted a study on catch composition of 40 commercial shrimp trawlers during 1985–86. The average catch composition found to be shrimp (4%), commercial fish (12.3%), juveniles of economic demersal by-catch (47.3%), trash fish (25.9%) and other discarded (9.7%). (Khan and Mustafa, 1992).
The dominant species of by-catch both landed and discarded are Sciaenidae (croakers or jew fish), Leiognathidae (silver bellies/pony fish), Nemipteridae (threadfin bream), Clupeidae (sardines, shads), Trichiuridae (ribbonfish), Carangidae (jacks, travallys), Mullidae (goatfish), Harpadontidae (Bombay duck), Ariidae (catfish), Synodontidae (lizardfish), Lutjanidae (snapper), Polynemidae (threadfins or tasselfish) etc (INFOFISH, 1986; Khan et al, 1989).
1.2 Present status of By-catch Utilization:
It is encouraging to see that BFDC has taken initiative in product development from by-catch. A fish processing laboratory was reported to be established in the premises of BFDC in Chittagong with the technical assistance from FAO. As reported earlier, a proposal to set up a pilot plant has been submitted to the Ministry of Fisheries for approval. Fish products such as burger, finger, cutlet, cake, balls and minced fish are prepared in limited scale from low-valued fishes harvested by BFDC trawlers. The products are yet to gain the market particularly, for city dwellers, restaurants and fast food shops. The poor quality of raw material upon arrival at the landing place, preparation of products from species of different flesh characteristics and uncertainity of regular supply, high amount of dark muscle and fat content as well as higher proportion of sarcoplasmic protein from muscles of multispecies probably make mince product less attractive for marketing.
Recently one private entrepreneur has come forward in setting up “surimi” processing industry in Chittagong in collaboration with a foreign country using by-catch as raw material.
The composition of raw material for the production of surimi, its production potential and marketing are not known yet. High degree of variation in catch composition and preparation of surimi from various fish species having different properties of muscle proteins adversely affected the quality of surimi product.
2. Prospects of Adding Value to By-Catch:
The prospects of adding value to by-catch largely depend on the demand. Conventional wisdom suggests that by the turn of the century the demand for fish and fishery products will exceed the currently available supplies, leading to intensified search for alternative sources.
The per capita fish consumption rate has shown declining trend in recent years due to the high population growth which is faster than the growth rate of fish production. It is becoming increasingly impossible to maintain the stable supply of foods, especially animal protein. The most direct and immediate contribution to increased food supplies could be made by reducing post harvest losses, which are very significant at various stages but are greatest in discards at sea in trawl fisheries.
2.1 Supply of By-catch as Raw Material:
Good quality raw material supplies are an essential prerequisite for any value-added processing activity. Once the quality of raw materials gets deteriorate there is no way to improve it by any means of preservation and processing. The organoleptic characteristics of fish species are important criteria to assess the quality of raw material for use in any value added activity.
Supply of raw material is a problem if by-catch is to be used in commercial scale through a bulk landing. Sorting, grading and gutting are labour intensive. Problems are also encountered in utilization of species having poor quality upon arrival at the landing place. High degree of variation in size make difficult for their efficient utilization.
Some form of partial processing of by-catch fish at sea, to reduce bulk, has been suggested as a solution to space constraints and rapid quality loss due to bulk landing. Partial processing at sea might be possible using a “meat/bones separator” to produce products, most probably in frozen form. This idea is currently receiving attention from public agencies serving the sector. In the system a specific vessel may collect partially processed by-catch from a fleet of trawlers to supply a land based plant. Improvement of handling of by-catch can be done by sorting, deheading and gutting during the towing of each catch. The sorted fish if necessary can be kept in ice for few days. Although storage life in ice varies from species to species, evidence suggests that gel strength of fish ball and surimi produced from stored by-catch kept in ice for 8–12 days was found fairly good (Suwanrangsi, 1986; Kamal et al, 1993a, 1993b).
2.2. Selection of Suitable Species:
All the species are not equally suitable for processing of various value added products. Fish muscle types such as ordinary and dark muscles, their properties, chemical composition and protein composition varies among the fish species. Different flesh characteristics in a product may influence the quality and make the product unattractive to the consumers in terms of appearance, flavour and odour.
Small pelagic fishes, such as sardine and mackerel, generally rich in lipid, have a large amount of superficial dark muscle. The proportion of dark to ordinary muscle is 20–30% (Watabe and Hashimoto, 1987; Suzuki and Watabe, 1987). The dark muscle is generally higher in lipid content and lower in moisture and protein content. Making minced fish block from pelagic fishes like sardine and mackerel is more difficult than lean fishes, because of high fat content and weak binding ability of meat. The most difficult points in minced and surimi processing from small pelagic fishes are (i) high fat content, (ii) instability of muscle proteins, (iii) large amount of sarcoplasmic proteins, and (iv) high proportion of dark to ordinary muscles. The gel forming ability of fish for processing of surimi also varies greatly from fish to fish, and depending on temperature conditions.
The small pelagic species, on the other hand, are suitable for processing of salting, canning, filleting and freezing. However, for the development of any value added products it is essential to know the characteristics and properties of fish muscle proteins such as distribution of ordinary and dark muscle, ratio of flesh, chemical composition and protein composition (myofibrillar, sarcoplasmic, myoglobin and stroma protein).
2.3. Processing of Value added Products:
Presently fishery industries of the country processing only shrimp as 100% export oriented commodity. Utilization of the rated capacity of processing plants has always been unsatisfactory due to inadeqate supply of raw material. Processing of by-catch into various value added products will bring immediate benefit to the industries. The following products could be prepared from by-catch depending upon size, yields and characteristics of muscle proteins, texture, appearance, flavour and odour.
2.3.1. Surimi Based Products:
The ideal characteristics of fish to be used would be an abundant low value white fleshed meso-pelagic or demersal species with good gelling capacity. Small size economic fish species such as catfish, lizard fish, pony fish and croakers are abundantly available and would provide an attractive source of raw material. The Surimi process results in a frozen intermediary product with a durability of more than one year without the loss of water binding capacity or elasticity. Cryoprotectants such as sucrose and sorbitol are added according to the needs of further uses and the degree of sweetness desired. The products which can be prepared from surimi are: (i) Kamaboko (chikuwa, fried surimi, hanpen); (ii) application as binder (artificial fish eggs, fish sausages, fish ball); (iii) production of seafood analogues and (iv) fabricated meats.
2.3.2. Minced Fish Products:
The fish mince is an intermediary product that is used for the production of laminated block, fish balls, roller dried fish, roller dried fish powder, fish noodles, and crackers.
2.3.3. Composite Fillets:
Small size fillets in combination with pieces of fish are formed by mechanic pressing into shape of large fillet- a product called composite fillets. This process is simple and is an inexpensive way of adding value to by-catch species.
2.3.4. Fish Blocks:
Smaller, irregular fillets and pieces of fillets from less fresh fish are used for the production of fish blocks. The output acts as an intermediary product for further processing.
2.3.5. Laminated Blocks:
Another type of block frozen product, laminated blocks, is produced on the basis of small and irregular fillets. The fillets and pieces of fillet of sometimes different species are mixed with up to 25% fish mince and frozen in block. This technology will able to utilize by-catch of multi species.
2.3.6. Battered and Breaded Products:
A variety of more value added products are manufactured usually from whole fillets, frozen blocks and laminated blocks. These products aim at satisfying the increasing market for ready-to-eat convenient products for direct household consumption and the catering and fast food markets.
2.3.7. Marinebeef from Small Pelagic Fishes:
This is a kind of fish protein concentrate made from under-utilized and abundantly caught fishes. Marinebeef can be rehydrated easily and cooked. It is less expensive and more easily handled for storage and transportation.
2.3.8. Semifermented fish products:
It is possible to produce highly stable nutritionally rich dried and powdered semifermented products from by-catch at low cost as protein supplement for human consumption.
3. Technology Transfer:
The traditional channels of industrial technology transfer have expanded in the past few years. Technology “package” that includes product, equipment and factory management is becoming very popular. The main transfer agents are: local or overseas R&D centres, joint ventures, equipment suppliers, study tours, trade fairs, courses and workshops, professional journals, local or international consulting and engineering firms. Many countries of the Asian region have created technological institutions which are responsible for the formulation, coordination and implementation of technology management.
4. Marketing:
The distribution of any value-added frozen products depend on the efficient functioning of cold chains, and would require significant inputs on the market development side.
The export market of value-added products is highly competitive, involving changes in type of products, forms and packaging as well as consumer behaviors. Often exporters are being disadvantage by the complexity of health and quality regulations. Therefore, processing industry, in particular, requires qualified fish processors, plant manager and post harvest technologists. Exporter must be aware of market requirements, regulations and standard of importing countries including any possible changes and should check with the importing countries before shipping their products.
5. Training and Research:
In order to promote the development of value added fish processing, training and research institutes should formulate programmes relevant to the countries requirements, taking into consideration type and quality of raw materials availability. Both training and research institutes should conduct fundamental and applied research to solve current problem in the processing of value added products.
References
BOBP (Bay of Bengal Programme) 1991 Post-Harvest Fisheries. The bycatch from Indian shrimp trawlers in the Bay of Bengal : The potential for its improved utilization, BOBP/ WP/68.
INFOFISH 1986. Product development in the use of shrimp by-catch in Bangladesh. Infofish Marketing Digest No. 5/86.
Kamal, M. Hossain, M.R.A., Hossain, M.A., Faruk, M.A.R. and Hossain, M.I. 1993. Development of fish products from under-utilized fish species of Bangladesh-1. Studies on the gelforming ability of some abundantly available under-utilized marine fish species of Bangladesh. Bangladesh Journal of Fisheries (communicated).
Kamal, M. Hossain, M.R.A., Faruk, M.A.R. and Hossain, M.I. 1993. Development of fish products from under-utilized fish species of Bangladesh-2. Studies on the effect of ice and frozen storage on gel-forming ability of marine catfish (Tachysurus thalassinus). Bangladesh Journal of Fisheries (communicated).
Khan, M.G., Mustafa, M.F., Sada, M.N.U. and Chowdhury, Z. A. 1989. Bangladesh off-shore marine fisheries resources studies with special reference to the penaeid shrimp stocks, 1988–89. Marine Fisheries Survey, Management & Development Project, Department of Fisheries, Government of Bangladesh, Chittagong.
Mustafa, M. and Khan, M.G. 1992. The off-shore trawl fisheries in Bangladesh. A paper presented at the BOBP seminar, Cox's Bazar, 12–15 January.
Suwanrangsi, S. 1986 Improved by-catch utilization in Thailand. Proceeding of the First Asian Fisheries Forum, Asian Fisheries Society, Manila, Philippines.
Suziki, T. and Watabe, S. 1987. New processing technology of small pelagic fish protein. Food Rev. Internat., 2, 271–307
UNIDO (United Nations Industrial Development Organization) 1991. Measures to increase the production and marketing of valueadded fish products in Asia and Pacific Island Countries. A paper presented in Regional Consultation on the Fisheries Industry for Asia and Pacific Island Countries, Vienna, 2–6 December.
Watabe, S. and Hashimoto, K. 1987. Temperature conditions for the frozen storage of representative marine products in Japan. Food Rev. Internat., 2, 353–393.
