Fish Farming Technology

H. Reinersten, L.A, Dahle, L. Jorgensen

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9781000162394
• Edition: 1
• Topic: Technologie et ingénierie
• Subtopic: Ingénierie

Over the past few years, it has become more and more obvious that fish farming will become increasingly important in the future. As fish farming moves into its industrial phase, technology will be an important factor in determining its successful development. It is therefore important for scientists & representatives from the aquaculture industry to meet to define state of the art and explore future development of fish farming technology for different fish species. 81 papers and abstracts were presented at the conference. The proceedings reflect the different sections of the conference: the plenum sessions and three parallel sessions: Juvenile marine fish, open production plants, closed production plants and poster sessions.

Closed production systems

Critical factors in fish farming in closed production systems

K.Tvinnereim

SINTEF Norwegian Hydrotechnical Laboratory, Trondheim, Norway

ABSTRACT: This paper gives a review of the main research activity attended to the NTNF-program: Closed production systems for the rearing of Atlantic Salmon and other species on shore and at sea.

The main aim at the program as well as the research projects has been to focus on the most critical factors which influence on the economical results.

Within the program there are 7 sub-programs:

• Technical/hydraulic and environmental control in closed fish farms.

• Biological operating parameters.

• Water analyses and treatment.

• Characterization and treatment of sludge.

• Management in closed fish farms.

• Development of rearing units, design criteria for closed fish farms.

• Technology transfer.

The program started in 1989 and will be finished this year. As the program proceeded, special attention had to be paid to a few “bottlenecks”:

• Development of methods for injection of oxygen into the water (sea water).

• Equipment, routines and manuals for submerged systems for transport and grading of fish.

• Development of equipment and manuals for secure operating of closed farms.

We believe that the solutions to these problems will be reached within this year.

More detailed information from different projects in the program will be given from the speakers later in this session.

1 INTRODUCTION

Farming of Salmonids in closed fish farms is a rather new kind of rearing profession.

Rearing in open cages at sea has lasted for some 20–25 years in Norway and the operating staff has certainly more or less found a satisfactory way to design, locale, mour and operate that kind of concepts.

During the NTNF’s program: Closed production systems, many Norwegian scientists, research engineers and biologists have been involved in a 5 years process in order to draw the guidelines for designing of closed farms, technical/hydraulic operating procedures and handling of the fish.

This paper gives a review of the knowledge that is a result of the program activity and the most critical factors which should be considered when rearing fish of different species in closed farms.

2 METHODS

2.1 Environmental condition in tanks

Of major importance when rearing salmonids and other species in closed fish farms, is the complete control of the environmental conditions.

The research work connected to this may be carried out in tanks at several scale; laboratory scale, pilot and fully commercial scale.

The main task is to improve tank design and operating quality by varying the depth/diameter ratio, the water flow into the tank and the inlet and outlet arrangements. The main aim for the experiments have been:

• The water injection (inlet arrangement) should be designed in a way that provides sufficient flow distribution, satisfactory water exchange and stable oxygen level in the tank.

• Adequate current velocities corresponding to fish size.

• Bottom current of sufficient strength for continuously cleaning of the tank bottom.

2.2 The research fish

The fish size has ranged from 60–80 grams (smolt) and up to 3–5 kg in weight. At different stages during the program period the stocking density has varied from 20–120 kg/m³ volume.

Some of the fish have been vaccinated before setting into the tanks. Unvaccinated fish have been reared as control groups.

2.3 Injection of oxygen

Methods for injection of oxygen into the water have been tested, developed and improved. Such systems include:

• The “Cone system” operating with an inside pressure of 3–4 bar.

• The “diffusor system” where the oxygen gas is injected through perforated tubes placed at the tank bottom.

• The “deep shaft system” where the oxygen is mixed into the water in the upper part of a double shaft 6 to 40 m deep.

• The “direct method” where the oxygen is injected directly into the inlet water through an injection unit at approx the same level as the water surface in the tank.

Effectiveness and expenses of the different methods have been recorded and calculated.

2.4 The growth rate

The growth rate certainly vary with many factors as:

• Water temperature and quality.

• Fish size and tank dimension.

• Stocking density and oxygen level.

• Stocking density and light regime.

• Feeding strategy.

Subeffects of different rearing strategies as sickness, stress, mortality, maturity and quality has been recorded and analysed.

2.5 Internal transport and grading

Different kind of equipment and arrangements for transport and grading of fish have been tested in pilot and commercial scale.

The main aim of this research should be to transport and grad the fish submerged.

There are certainly many ways to look into that problem. It is very important to study the fish itself and to observe different reaction pattern dependent on several effects as:

• The water flow regime, current velocity and direction.

• The light regime above the tank.

• Use of equipment for directing the fish towards the wanted area.

• Using decreasing water level for directing the fish.

3 RESULTS

Most of the results from the research in NTNF’s program will be given in a more detailed presentation in later speeches.

3.1 Tank operation

Research work in laboratory scale, pilot and commercial scale have given basic knowledge of design and operating criteria for tank units and closed fish farms.

Analysis of test results have given:

• Guidelines have been established for the designing of tanks, inlet- and outlet arrangements.

• Limits for water injection volume for hydraulic operation of the tank, max and min retention time.

• Necessary strength of bottom current for sufficient selfcleaning of the tank bottom.

• The most practical and less expensive way for oxygen supply; partly from pumped water, partly from injected oxygen.

3.2 Biological parameters

Research over a whole production cycle, from smolt to slaughtering, have given results as:

• Oxygen demand for salmon in closed fish farms.

• Optimal oxygen concentration in a tank for maximum growth of the fish.

• Stocking density limits for commercial rearing conditions.

More research is certainly needed for sophistication and accuracy in the future.

4 DISCUSSION

The major aim in all kind of fish farming is to earn money!

In closed production systems the experiences up to now have shown that several critical conditions have to be met before profit can be obtained.

The aim may possibly be reach if:

• We are able to decrease the investment to approx NOK 25.00 per kg fish (over the year).

• The internal environment can be fully controlled.

• The most efficient method for oxygen injection should be chosen. The oxygen concentration in the effluent should be stable at a level of 7–7.5...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Organization
• Plenary lectures
• Juvenile marine fish
• Open production plants
• Closed production systems
• Posters
• Author index