Fish farms - A special application for Krah pipes
Introduction
Around 17% of the world population reach their protein level by eating fish. That’s even more than vegetables or pork. Accordingly, fish farms have become an important factor in the worldwide fish supply, as wild caught fishes can’t meet the demands anymore. Overfishing and mass mortality rates in seas and oceans are the result. The following report shows a typical “cycle” of fish living in such farms and how Krah Pipes are helping to guarantee a safe and appropriate handling of the fishes, using the example of salmon.
Salmonid lifecycle in nature
The salmonid species most commonly farmed in Chile are the Atlantic salmon (Salmo salar), Coho salmon (Oncorhynchus kisutch), and rainbow trout (Oncorhynchus mykiss). These species are anadromous, meaning they spawn in freshwater and remain there until reaching the juvenile phase. They then undergo smolting, a fundamental physiological change that allows them to migrate to the ocean where they grow and mature sexually. The following few graphics show the lifecycle of a salmon, from the fertilized egg to a finished, grown salmon:
Salmonid lifecycle Lifecycle in captivity
Salmon lifecycle in captivity
Attempts to domesticate and raise salmon have focused on recreating the natural conditions of their lifecycle in the wild. In order to achieve this, fish are kept in net pens, land-based flow-through systems or recirculating aquaculture systems where the overall biological process of the fish can be controlled by regulating water parameters such as temperature, dissolved oxygen and pH. The lifecycle can be altered by manipulating breeders during spawning using hormones and/or modifying the photoperiod or temperature during the alevin phase in the farming systems. In addition to temperature, fish growth rates also depend on the amount of feed provided. This factor determines metabolic efficiency, which is generally expressed as the feed conversion rate.
Water quality
Available dissolved oxygen is the primary determining factor for maximum farm biomass, which, in turn, depends on temperature, conductivity and atmospheric pressure. Greater farm density results in higher demand for oxygen by fish. It is therefore essential to maintain the quality of the water in which the fish develop in order to obtain the required production and ensure the animals’ well-being. Keeping physical, chemical and biological water conditions within appropriate limits will have a positive effect on growth rates and will lower fish stress levels, resulting in a lower risk of disease outbreaks.
At a farm with low water renewal or circulation rates, phytoplankton alone can consume up to five times more oxygen per day than the fish. So what exactly does a fish farm? Fish farming or pisciculture involves raising fish commercially in tanks or enclosures such as fish ponds, usually for food. It is the principal form of aquaculture, while other methods may fall under mariculture. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species' natural numbers is generally referred to as a fish hatchery. Worldwide, the most important fish species produced in fish farming are carp, tilapia, salmon, and catfish.
Demand is increasing for fish and fish protein, which has resulted in widespread overfishing in wild fisheries. China provides 62% of the world's farmed fish. As of 2016, more than 50% of seafood was produced by aquaculture. Farming carnivorous fish, such as salmon, does not always reduce pressure on wild fisheries. Carnivorous farmed fish are usually fed fishmeal and fish oil extracted from wild forage fish. The 2008 global returns for fish farming recorded by the FAO totaled 33.8 million tons worth about $US 60 billion.
The year 1985 marked the beginning of the boom of the salmon industry, when Chile entered to the exclusive club of producing countries of salmon. Between 1991 and 2005 the industry grew in an explosive way: of 33 thousand tons for a value of 159 million dollars, it passed to 384 thousand tons equivalent to 1.721 millions.
Different types of fish farms
Flow-through land-based farms Open farms in lakes, estuaries and rivers Land-based recirculating aquaculture systems
Land-based recirculating aquaculture systems
An aquaculture recirculation system is that which includes water treatment and re-use in the farming process. Approximately 10% of the water volume is replaced daily, although this figure can range from 5 to 20% depending on the type of cultivation tank and filtration. A recirculation system is comprised of mechanical and biological filtration components, pipes, pumps and containment tanks, and may also include additional water treatment elements to improve water quality and disease control in the system.
Case Study “ PISCICULTURA RIO LLAIMA – CHERQUEN”
Country: Chile
Region: IX Region of Araucanía, Commune: Cunco
Category: Fishing and Aquaculture
Start of activities: 2007
System schematic
Krah pipes in use at every system step
- Water collection
The water intake must be done ensuring the quality and continuity of water supply. Normally water sources are not too close to consumption, so it must be brought safely.
- Water transportation
Once captured, the water must be transported to the source of consumption quickly and safely. Normally natural obstacles such as streams, creeks, canyons, forests and others must be avoided. For this, the pipe must be strong and flexible enough to adapt to these conditions. In this case, water is transported by gravity from intake to consumption.
- Filtering, treatment and pumping
The collected water, although it has ideal characteristics for the smoltification process, must be controlled, treated and finally pumped to the different ponds.
For this, the flow of water passes through a treatment and pumping unit and through pipes specially designed to not affect the original water conditions.
- Distribution
Once the water is treated, it is distributed among the different ponds. The water must be constantly monitored to avoid changes in the parameters of temperature, oxygen and biological load that could negatively affect the growth of the colony and even cause mortality.
- Discharging
The water in the ponds must be renewed to avoid contamination and loss of temperature and oxygen conditions. Therefore, between 5% and 20% of the total volume of water used must be renewed daily. The supply and discharge of the water cannot be stopped, with the risk of losing the entire colony in a few hours.
Overview about the ued Krah Pipe products for the project:
3 km of Krah pipes in different stiffness and pressure classes, all jointed by electrofusion:
Item |
Material |
Unit |
Qty |
26 |
Krah Pipe Profiled (PR), DN 1000, PN 0.5, EF |
m |
800 |
1 |
Krah Pipe Profiled (PR), DN 900, PN 0.5, EF |
m |
350 |
6 |
Krah Pipe Profiled (PR), DN 600, PN 0.8, EF |
m |
550 |
13 |
Krah Pipe Profiled (PR), DN 500, PN 1.0, EF |
m |
350 |
17 |
Krah Pipe Profiled (PR), DN 400, PN 1.2, EF |
m |
950 |
Multitude of fittings (bends, Tee’s, reducer etc.) and manifolds:
Item |
Material |
Unit |
Qty |
32 |
Tee, solid wall (VW), DN900/900 (section Nº2) |
pcs. |
1 |
33 |
Tee, DN 1000 / DN 250 (section Nº7) |
pcs. |
1 |
34 |
Manifold tangential, DN 1000/ DN 400 (section Nº4) |
pcs. |
2 |
35 |
Manifold with reducer, solid wall (VW), DN900/500 (section Nº3) |
pcs. |
1 |
36 |
Manifold centric, DN 400 (section Nº6) |
pcs. |
3 |
37 |
Manifold centric, DN 1000/ DN 400 (section Nº3) |
pcs. |
1 |
38 |
Bend, solid wall (VW), DN900, 53º (section Nº1) |
pcs. |
1 |
39 |
Bend, solid wall (VW), DN900, 29º (section Nº7) |
pcs. |
1 |
40 |
Bend, solid wall (VW), DN500, 90º (section Nº4) |
pcs. |
2 |
41 |
Bend, solid wall (VW), DN500, 90º (section Nº11) |
pcs. |
1 |
42 |
Bend, solid wall (VW), DN400, 90º (section Nº10) |
pcs. |
1 |
43 |
Bend, 53º, DN 400 (section Nº8) |
pcs. |
1 |
44 |
Bend, 47º, DN 1000 (section Nº1) |
pcs. |
1 |
45 |
Bend, 27º, DN 1000 (section Nº2) |
pcs. |
1 |
46 |
Adaptor flange (section Nº5a) |
pcs. |
9 |
47 |
Adaptor flangesection Nº5b) |
pcs. |
9 |
48 |
Adaptor flange, DN500 (section Nº6a) |
pcs. |
3 |
49 |
Adaptor flange, DN400 (section Nº5a) |
pcs. |
4 |
50 |
Adaptor flange, DN500 (section Nº6b) |
pcs. |
3 |
51 |
Adaptor flange, DN400 (section Nº5b) |
pcs. |
4 |
52 |
“Y-piece” with bend and reducer, DN900/400 (section Nº9) |
pcs. |
1 |
53 |
"S-piece" DN900 (section Nº8) |
pcs. |
1 |
- Conclusion:
Water transportation in fish farms is a complex venture, so it must be done professionally and quickly. Any “natural” disturbances in the water flow must be avoided. That’s where Krah pipes come in very handy, as they have the well-known smooth inner surface, are completely tight connected by welding and can be inspected easily due to their bright yellow inner layer. The variety of Krah pipe accessories can be seen in the table above, for every situation and load case Krah has a solution. The plastic pipe market has been significantly growing in the past decade, and Krah pipes are used for more and more sorts of application. Especially today, where sustainability and environmental protection are becoming more and more important, since we do not have a planet B, Krah pipes are getting more popular due to their more than 100-year-lifetime and their recyclability of up to 100%.
Author:
Gustavo Mastelono
Krah América Latina SA