Unit 10 Fishery Production and Management PDF

 Learning Outcomes At the end of this unit, you will be able to: recognize farmed fish species in Ethiopia. explain basic anatomy of bony fishers. describe fish feeds and feeding practices. examine the fish culture techniques. explain fish rearing methods. identify fishin...

 Learning Outcomes At the end of this unit, you will be able to: recognize farmed fish species in Ethiopia. explain basic anatomy of bony fishers. describe fish feeds and feeding practices. examine the fish culture techniques. explain fish rearing methods. identify fishing methods. express the handling of fish and fish products list the major disease of fish and control methods. elaborate the application of indigenous knowledge in fish processing. give values for indigenous knowledge in fishery management. ƒpractice handling fish and fish products effectively.  10.1. Basic terms in aquaculture and farmed fish species in Ethiopia Aquaculture is the farming of aquatic organisms. Ethiopian fish fauna are the bony fish. Fresh water contains the majority of teleost (bony fishes) fish type. Ethiopian fish fauna consists of 153 indigenous and 10 exotic species. The Ethiopian indigenous freshwater fauna is a mixture of three different forms. Nilo-sudanic forms, East African high land forms and ƒEndemic forms Nilo-sudanic forms are represented by a large number of species found in the Omo-Gibe, Baro-Akobo, Tekeze and Abay drainage basins. These forms also occur in the Southern Rift Valley Lakes and The Shebelle-Ghenale basins. The Grand Ethiopian Renaissance Dam (GERD) is also expected to have potential for fish farming. The Nilotic fishes are almost entirely absent from the Awash and northern rift valley lakes. The East African highland forms  are those related to fishes of eastern and southern Africa  include genera such as  Labeo  Barbus  Clarias: Catfish  Garra  Oreochromis, and  Varicorhinus. These are found in the northern Rift Valley lakes (e.g. Lakes Hawassa, Ziwai, Langano), the highland lakes (e.g. Tana and Hayq), and associated river systems, and the Awash drainage basin. Labeo Barbus Clarias Garra Oreochromis Varicorhinus  The endemic forms are very few comprising about 38 species and 2 subspecies. Examples include a few genera such as Danakilia Nemacheilus and Garra (Lakes Abaya and Chamo), Barbus (Lakes Tana and Chamo) Exotic fish that were introduced to Ethiopian water bodies include fish such as carp in Koka and Fincha dams. Danakilia Nemacheilus Exotic fish: Carp  Economically important family includes three species of tilapi 1. Family Cichlidae (Cichlids) This family includes three species of tilapias in Ethiopia. These are Oreochromis niloticus Tilapia zilli and ƒTilapia galilaea O. niloticus is found in most Ethiopian freshwaters and Commonly known as “Qoroso”, St. Peter fish, Chogofe,. 2. Family Centropomidae (Centropomids) Most members of this family are marine and only genus Lates is a freshwater form both in Ethiopia and in other parts of Africa. L. niloticus (commonly called the Nile perch) is the major species of the genus found in Ethiopian Lakes such as Chamo, Abaya, Gambella lakes and Baro River. Centropomidae L. niloticus is carnivorous on other fish and is not good to introduce them into water bodies other than their natural habitats.  3. Family Claridae (Clarids) The common example is Clarias gariepinus (commonly Catfish, “Ambaza”) found in Lake Tana, Lake Abaya and the Awash River. C. gariepinus can be easily recognized by their elongated body and long hair like barbells around their mouth.  4. Family Cyprinidae (Cyprinids) This family includes genera such as Barbus (commonly in Nechasa), Labeo and Carp. Barbus is more common in rivers than in lakes and is much common in Lake Tana. Three carp species Cyprinidae Common carp, grass carp and Silver carp are introduced Species  10.2. Basic Anatomy of Bony Fishes Bony fishes have a bony skeleton. They have five pairs of gills protected by an operculum, and a mouth at or near the tip of the snout. The dermis (skin) is covered with overlapping scales. Bony fish have a swim bladder which helps them maintain a constant depth in the water column. The main external features of the fish, are composed of either bony or soft spines called rays which,  with the exception of the caudal (tail) fins, have no direct connection with the spine.  10.3. Fish feeds and feeding practices The survival, growth and reproduction of fish depends on fish-feeding activities. Fish have a considerable capacity to resist starvation. Feeding: food preparation, feeding mechanism of fish Food capture: most food eaten by fish is obtained through three basic feeding styles. i.e. Ram feeding: a method of feeding underwater in which the predator moves forward with its mouth open, engulfing the prey along with the water surrounding it Suction feeding: the primary mode of prey capture in fishes, a method used to draw prey into the mouth by using the density of water as a tool for prey transport Manipulating or Biting feeding method: bite off small pieces of plants. jawless fishes also use manipulation in order to obtain food.  Feeding habits of fish The food and feeding behavior, varies characteristically in different species of fish. There are four categories of fish food.  basic food,  secondary food,  incidental food, and  obligatory food. Fishes occupy almost all trophic (relating to nutrition ) categories. i.e., from herbivores to piscivores (fish eater). Trophic categories in fishes are:  Detrivorous fish: feed on the dead and partially decomposed plants  Scavengers: feed on the decaying animal flesh  Plankton feeders: feed upon the planktons, both on phyto and zooplankton  Plankton is the aggregate of small plant and animal organisms that float or drift in great numbers in fresh or salt water  Herbivorous fishes : feed on the plant materials (vegetation)  10.4. Fish culture techniques Types of aquaculture can be classified on the basis of  fish culture,  enclosure density or  integration. 10.4.1. Aquaculture classification on the basis of Fish culture: Sub divided into four 1. Monoculture: Raising only one species of fish in available water body. For example, tilapia, rainbow trout, catfish, etc. 2. Polyculture: Culturing two or more than two species of fish in the same water body. For example, rearing of bighead carp and grass carp. 3. Mono-sex culture: Raising either male or female of single fish species. It is practiced for maintaining breeding male and female fish. Mono-sex culture Advantages:  feeding, disease diagnosis and treatment is easier  Typical characteristics of fish can be studied more accurately Disadvantages:  Productivity of pond is not fully utilized  Market supply cannot be fulfilled and is riskier 4. Poly-sex culture : Either male or female of two or more species is reared in the same pond. Advantages:  Productivity of pond is fully utilized  Yield per unit area is higher  Less risky Disadvantages:  Cultivation practices is difficult  Costly and labor intensive  Selective harvesting is difficult 10.4.2. Aquaculture classification On the basis of enclosure Classification of fish culture based on the basis of enclosure can be further divided into Pond fish culture, Cage fish culture: Cage culture uses existing water resources (ponds, rivers, estuaries, open ocean, etc.) but confines the fish inside some type of mesh enclosure. The mesh retains the fish, making it easier to feed, observe and harvest them. Pen/enclosure fish culture: Pen culture is defined as raising of fish in a volume of water enclosed on all sides except bottom, permitting the free circulation of water at least from one side. This system can be considered a hybrid between pond culture and cage culture. 10.4.3. On the basis of density Intensive fish farming system Semi intensive fish farming system Extensive fish farming system 10.4.4. On the basis of integration Pig and fish farming Duck and fish farming Horticulture crop and fish farming Rice paddy and fish farming  10.5. Fish rearing management There are three main events in the fish rearing or farming timeline: hatching, Rearing (nurturing, raising), and harvesting. Hatching includes caring for breeding colonies, inducing spawning egg extraction or nursery isolation, etc. Once hatched, fry (young fish) are then collected and moved to grow out ponds. Unlike other fish, fresh water fish like tilapia tend to be hardier against poor water quality Best practice shows that Water quality should be maintained  the dissolved oxygen level should be around 4 mg/l.  Low oxygen levels in water often lead to mass fish death.  In terms of pH,  tilapia can tolerate a wide range but a pH over 6.5 is good for algae growth which is useful as feed for the fish.  Temperatures around 25 ºC are most favored by the fish. Stocked at recommended densities  Tilapia can be up to 60 kg/m3 (depending on water and management conditions).  high stocking densities may have a negative impact on growth performance and health status.  Low stocking densities, however, can often lead to aggression between the fish.  Rearing, or grow-out,  part of fish farming that picks up after the hatchery has raised them to fingerling size. Harvesting or processing  involves selecting of tilapia and moving them to a finishing pond.  10.6. Fishing methods A number of different fishing methods are employed to capture fish dependent upon  the species being harvested  available technology  local conditions such as bottom type and water depth. Fishing gears is a device used to capture fish. There are two major types of fishing gears, i.e.  passive fishing gear and  active fishing gear. Passive fishing gear is a device that is not moved by man or machine to capture fish. The machine is set at a given position in the water and left for some times until the fish come to the gear to be caught. It is placed stationary in one place.  Examples include long line, gill net, traps and pots, etc.  Longline fishing, or longlining, is a commercial fishing angling technique that uses a long main line with baited hooks attached at intervals via short branch. Stationary traps, or pots, typically made from wood, wire netting or plastic, are used to catch crustaceans such as lobsters and crabs  Active fishing gears are towed or pulled in water column using fishing crafts to catch the fish. These include trawl nets, seine nets, dredge nets, lift nets, etc. The major types of fishing methods used for fish include netting, lining, trolling, trawling and seining. dredging, jigging and pots are often used for capturing shellfish (such as squids and crabs). A fishing dredge, also known as a scallop dredge or oyster dredge, is a kind of dredge which is towed along the bottom of the sea by a fishing boat in order to collect a targeted edible bottom-dwelling species 10.7. Handling of fish and fish products Fish is a highly perishable food/product requiring proper handling processing and distribution Fish should be slaughtered in fishery abattoir equipped with the required facilities Fish should be eviscerated (surgically remove a part of a structure or an organ) immediately after slaughter and preserved until consumption.  Fish Processing Methods Fish processing associated with fish and fish products from the time fish are caught or harvested from capture fisheries and/or aquaculture to the time of the delivery of the final product to the end user. Deterioration in fish quality is because of the post-mortem (after death) biological changes that take place in the body of dead fish. Changes in fish quality indicators unpleasant odor microbial spoilage  Stages of fish processing Fish processing stages can be classified as  preliminary and  main stages  depending on the extent of application of techniques and skills. Preliminary Processing  also referred to as pre-processing stage.  usually consists of  grading  removal of slime (any thick, viscous matter)  Beheading (execution by cutting off the head)  Scaling (the act of arranging in a graduated series)  Washing  cutting of fins,  gutting and evisceration  slicing of whole fish into steaks and skinning. The process can also includes  Filleting (a longitudinal slice or boned side of a fish)  grinding of skinned fillets  meat-bone separation  Main Processing Stage Fish Preservation is the creation of unfavorable condition for the growth or survival of spoilage organisms. Ancient methods of preserving fish included drying, salting, pickling and smoking. This stage is mainly concerned with fish preservation processes. Techniques used in fish and fish products preservation Parameter to be controlled Method used Temperature Chilling, Refrigeration, Freezing Water activity Freeze-drying, Oxygen Vacuum pumping Chemical control of microbes (pH) Addition of acids Physical control of microbes Microwave heating, Ionizing  10.8. Diseases in Aquaculture Microorganisms such as viruses, bacteria, water molds (fungi), and parasites cause diseases of freshwater fish in warm-water aquaculture. Some of these agents are obligate pathogens (require a host for survival in nature), but many do not require a host and can be found living in aquaculture waters. These microorganisms facultative (not compulsory (not obligatory)) agents are opportunistic and cause problems when the host’s resistance is compromised. The most common pathogens that affect aquaculture include: Viral diseases: The most serious viral disease is channel catfish virus disease (CCVD). Channel catfish virus is a herpes virus (viral diseases causing eruptions of the skin or mucous membrane) that attacks swim-up fry to 10 cm fingerlings when water temperatures are 25 °C or above. Mortality due to CCVD can be acute and reach up to 90 percent, especially in densely populated tanks or ponds. Bacterial diseases: cause more infectious disease problems. The motile aeromonad septicemia (MAS) is a common disease of fish 10.9. Local knowledge in fish processing Ethiopian consumers prefer for whole fresh fish. However, frozen filets are increasingly being marketed in lakeside towns as well as in the capital city, Addis Ababa. Smoking and drying is carried out only on some remote fishing locations. Drying is increasingly becoming a method frequently used to preserve excess catches. Traders face major storage problems due to the shortage of cooling systems. “ Quanta ” is generally prepared in poor hygienic conditions, insufficiently dried and stored on bare ground. This often significantly decreases the quality