Environmental and Culturing Conditions
Discuss about the Biology of the Rainbow Trout and key factors for cultivation.
The Rainbow Trout(Oncorhynchus, mykiss) is a North American native fish to Pacific drainages that runs from Alaska to Mexico(Parol, Pietrzak-Fiecko & Smoczynski, 2014). It has been introduced to other continents and countries since 1874 where most of the trout fisheries are maintained and cultured(Parol, Pietrzak-Fiecko & Smoczynski, 2014). The rainbow trout has a wide range of tolerance in different environments since it is fast growing, hardy and easy to pawn and can be easily weaned to artificial food(Tower, 2012). The rainbow trout is capable of occupying a wide range of habitats ranging from rivers, lakes, and streams. It has a capability of archiving a rapid growth where within a period of about three to four years, the weight of a rainbow trout can be 7 – 10 kg(Omaima Harun, Zou, Zhang, Nie & Secombes, 2014). The fish is capable of withstanding a range of temperatures starting from 0-27 degrees(Tower, 2012). However growing and spawning only occurs in a narrower range of between 9-14 degree Celsius(Parol, Pietrzak-Fiecko & Smoczynski, 2014). The optimum temperature need for a rainbow trout is around 21 degrees Celsius. Due to this characteristic, rainbow trout is highly influenced by temperatures and food availability in terms of growth and maturation making the maturity age to vary between 3 – 4 years(Omaima Harun, Zou, Zhang, Nie & Secombes, 2014).
The female trout has a capability of producing over 200eggs per kilogram body weight. The rainbow trout eggs are generally large in diameter ranging from 3 to 7 mm(Berrill, MacIntyre, Noble, Kankainen & Turnbull, 2012). Most of the fish only spawn once although research has been done and various bleeds developed which can spawn throughout the year(Omaima Harun, Zou, Zhang, Nie & Secombes, 2014). Rainbow trout can develop superior characteristic through cross bleeding which may end up increasing growth rate, resistance to diseases, improvements in meat quality and taste, prolificacy and weight(Tower, 2012). Several countries like the United State have also developed a genetic manipulation of rainbow trout embryo sex chromosomes that lead to the production of triploid females which do not possess a characteristic of hook-like jaws ensuring customers attraction(Omaima Harun, Zou, Zhang, Nie & Secombes, 2014). Rainbow trout do not naturally spawn naturally in the culture system making the juveniles to be obtained by the collecting eggs from a wild stock or from the artificial hatchery(Tower, 2012).
Different populations of a rainbow trout will require various habitats including small to large livers, cool lakes, cold headwaters, oceans, and tributaries(Heather, 2012). Rainbow trout will use almost all these habitats depending on the genetic habitants and trout population(Tower, 2012). The prime rainbow trout water habitats are usually clear, clean and cold(Berrill, MacIntyre, Noble, Kankainen & Turnbull, 2012). Rainbow trout rely on different types of food substances making them be opportunistic feeders. Their feeds range from small insects to crayfish( FAO ,2015). The advantage of farming rainbow trout in the artificial pound is that they quickly adapt to different types of artificial food provided. Rainbow trout normally spawn in main river channels and in lakes tributaries including both inlets and outlets( FAO ,2015). This usually happens once or twice in a year during the spring and early summer. The female rainbow trout normally lay a portion of her eggs where male will later pass on and fertilize them(Heather, 2012). Farmers can harvest juveniles later and take them to their fish ponds. Rainbow trout do not spawn on the fisheries thus the juveniles can only be artificially hatched or collected in the tributaries(Heather, 2012). A sufficient water depth is required in the tributaries to ensure the eggs get enough oxygen and the metabolic waste can be freely be removed.
The ideal intersection of habitat components will require a cool and clean water. with overlapping riparian vegetation on the undercut banks(Heather, 2012). The water should be slow- flowing to deep pools with one to three-inch diameters gravels. In addition, aquatic weed beds are required with submerged branches or logs(Tower, 2012). Since the rainbow trouts are more solitary than social, more partitions should be used with small sizes and territories allowing more fish to coexist during the winter periods. Deep sides of the pools are important during the winter survival(Hayes, 2013).
A study by Dr. Hayes in 2013 concerning trout spawning in Wellington region proved that New Zealand can make a great environment for rainbow trout farming (Fish and Game Organization ,2018). The study demonstrated that the Wellington Region has significant streams and rivers that support trout fisheries and trout spawning( FAO ,2015). Specifically, the Ruamahanga and Hutt rivers were found to contain a large number of anglers in all years(Trout aquaculture ,2018). The rivers also have many tributaries like Waihoinie River that had a great reputation in providing an adequate aquatic ecosystem for spawning of rainbow trout (Trout aquaculture, 2018). Other than that, the whole of New Zealand has significant large water bodies than land which provide great environments with streams, rivers, and tributaries that allow Rainbow trout survive and spawn(Fish and Game Organization ,2018).
A consistent water supply is needed in Rainbow trout farming. The replacement of water should be continuous to allow only fresh, clean and oxygen-rich water remains in the fisheries(Tower, 2012). The quantity of eggs per unit is primarily determined by the amount of fresh water a unit can hold. The frequency of water exchange varies depending on where the fish are grown( FAO ,2015). Water supply in earth ponds should be exchanged in about 5 to 5 times a day but typically it is exchanged twice a day(Berrill, MacIntyre, Noble, Kankainen & Turnbull, 2012). There various production options required depending on the type of farming one is desiring to do(Tower, 2012). This includes the eyed egg production, fry production fingering production, and table fish production.
Various production devices are required in rainbow trout farming. This includes hatching trays, polypropylene or fiberglass rearing trough and tanks, membrane tanks, lined and unlined tanks and concrete tanks may be used in all types of productions(Tower, 2012). Earth ponds have been used for a long duration though lately, most farmers do not prefer them (Ministry for Environment 2018). Water supply and drainage should be well constructed in earth ponds allowing inlets and outlets plus deep ends and shallow ends. Mechanical and biological filters are other crucial requirements for Rainbow trout farming in order to avoid environmental pollution(Tower, 2012). During the site selection, the basics of selection should primarily depend on the availability of water supply including both the quality and quantity of available water as well as the suitability of the site. A rule of thumbs by Edwards in 1989 suggest that per every tonne of rainbow trouts produce, water should run at a rate of ten liters per second. Human resource, especially in management and planning, is also essential in starting a new production unit(Berrill, MacIntyre, Noble, Kankainen & Turnbull, 2012). There are various stems involve in planning which includes knowing the existence of capital needed and available markets, elaboration of engineering design, acquisition of permission, construction, and a trial run(Tower, 2012). For proper growth and development of rainbow trouts high protein feeds is usually the first line of desired feed.
Potential Risks and Mitigation
Currently, in New Zealand, rainbow fish are prohibited to farm, therefore, government interventions need to be addressed. The demand and automatic feeders are usually released when the fish has an appetite( FAO ,2015). However, rainbow fish are usually greedy which may read unnecessary feeding thus high cost of feed may be one of the major problems during farming. Poor feeding, on the other hand, may lead to feeding problems that make larger rainbow fish bite or eat the smaller fish therefore there will be poor production. Other than that, Rainbow trout should be grown in areas which are not prone to predators such as crocodiles and snakes or other larger fish like sharks. Other than that, there are a variety of diseases and parasites that can affect the rainbow trout in any production unit(PAEK & PARK, 2016). Such diseases include Furunculosis, bacterial kidney disease, vibrosis, bacterial gill disease, infective pancreatic necrosis and viral haemorrhage septicaemia . Some of the parasites that attack the trout include white spots, fluke, trematode parasite and hexamiatatic ostomies. Most of them especially the parasites have no treatment available thus their effects can be vast. Construction of production units need technical know-how and education hence it can be expensive in terms of human resources and materials of construction.
There are very strong markets for rainbow trout that exist across Europe and the USA, where only in Chile, USA and Norway have a significant amount of rainbow fish produced( FAO ,2015). The trout prices have demonstrated an increase over the years(Waynarivich, 2015). For example in Norway, between the 2012 and 2013, there was a significant increase in the prices by 10%. Their first sale exports ranged around NZ$9.50/ kg. This is a good indication that rainbow trout have a possible international market(Waynarivich, 2015). A projection done by European Maritime and Fisheries Fund(EMFF) showed that about 158 million tones of fish were produced worldwide by the year 2015. However, the demand has been increasing day by day due to change in lifestyles as affected by most chronic diseases and from medical advice(Settera, 2016). The change is expected to change over the time with an increase of about 35% by the year 2022(Hayes, 2013). This creates a potential market for the Rainbow trout(Waynarivich, 2015). A debate by federal farmers and Sanford limited in the year 2012 concerning rainbow trout showed that New Zealand is missing out hundreds of millions of dollars in export due to the banishment of rainbow trout(Settera, 2016). Other works in branding techniques need to be addressed. Freeze branding of young trout has demonstrated to be effective(PAEK & PARK, 2016).
The initial cost of rainbow trout farming is quite expensive ( FAO ,2015). This is due to various construction and purchase of assets and liabilities(PAEK & PARK, 2016). Expensive facilities are generally needed for example construction of concrete ponds. The frequent years, the cost is minimized with an increase in production. This makes the benefits to outweigh the cost(Settera, 2016). However, a study that was done in Nepal showed that the cost varies depending on the amount of production. The result showed that per every NRs255 used in the production of one kilogram a sale of NRs 300 was archived(Hayes, 2013). New Zealand target a net profit of one billion dollars in all aquatic fish. This can only be archived only if the government reinforce and support trout farmers(Settera, 2016).
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