Advances in Aquaculture Hatchery Technology

Geoff Allan, Gavin Burnell

• Publisher: Woodhead Publishing
• Year: 2013
• Print ISBN: 9780857091192
• eBook ISBN: 9780857097460
• Topic: Technology & Engineering
• Subtopic: Fisheries & Aquaculture
• Index: Technology & Engineering

Aquaculture is the fastest-growing food production sector in the world. With demand for seafood increasing at astonishing rates, the optimization of production methods is vital. One of the primary restrictions to continued growth is the supply of juveniles from hatcheries. Addressing these constraints, Advances in aquaculture hatchery technology provides a comprehensive, systematic guide to the use of current and emerging technologies in enhancing hatchery production.Part one reviews reproduction and larval rearing. Aquaculture hatchery water supply and treatment systems, principles of finfish broodstock management, genome preservation, and varied aspects of nutrition and feeding are discussed in addition to larval health management and microbial management for bacterial pathogen control. Closing the life-cycle and overcoming challenges in hatchery production for selected invertebrate species are the focus of part two, and advances in hatchery technology for spiny lobsters, shrimp, blue mussel, sea cucumbers and cephalopods are all discussed. Part three concentrates on challenges and successes in closing the life-cycle and hatchery production for selected fish species, including tuna, striped catfish, meagre, and yellowtail kingfish. Finally, part four explores aquaculture hatcheries for conservation and education.With its distinguished editors and international team of expert contributors, Advances in aquaculture hatchery technology is an authoritative review of the field for hatchery operators, scientists, marine conservators and educators.- Provides a comprehensive guide to the use of technologies in enhancing hatchery production- Examines reproduction and larval rearing, including genetic improvement and microdiets- Discusses challenges in hatchery production of specific species

Part I

Reproduction and larval rearing

1

Aquaculture hatchery water supply and treatment systems

O.-I. Lekang, Norwegian University of Life Sciences, Norway

Abstract:

Good water quality is of major importance to production results in a hatchery, particularly in those which work more intensively. A low cost water transfer system is also important economically, affecting both investment and running costs. The low cost, however, should not be allowed to compromise the efficacy of the system, leading to operating problems or a lower water quality, for example. This chapter will take a brief look at some important factors in the location of hatcheries, before progressing to assess different water supply systems, encompassing both fresh water and sea water. Before the water enters the production unit, it has to be treated to fulfill the requirement of the aquatic organism as closely as possible. A description of different water treatment equipment/methods is also included in the chapter.

Key words

hatchery

water supply

site selection

water treatment

1.1 Introduction

Water quality is integral to the production results of any hatchery. Larvae/ fry have higher water quality requirements than larger fish - the larger the fish, the less significant the water quality - and it is therefore crucial to find suitable sites for the establishment of hatcheries and to ensure that the water is treated in the optimal way before it is used in the hatchery.

The water quality requirements will, to a certain extent, be dependent on the given species. Larvae or fry may be divided into two different categories: fish such as cod which, in their natural environment, will drift passively around the water, and 'stationary' species such as salmonids, which remain still in a continuous water flow. For the former, the water volume around the larvae is quite constant, while for the latter, the larvae must adapt to the quality of the given water.

Hatcheries can be categorized, based on the intensity of production (in other words, the number of produced larvae/fry per m³ water and growth rate), into extensive, semi-intensive and intensive. They may also be divided into freshwater or seawater hatcheries depending on the species grown and if sea water or fresh water is used. Hatcheries that use fresh water may, furthermore, be separated into hatcheries that utilize gravity for water transport into the farm and ones which use pumped water which must be lifted into the hatchery. The former is preferable due to lower running costs. In this chapter, the general focus will be on land-based hatcheries with intensive production. Hatcheries may, however, also float in the sea, which reduces the pumping cost but makes it difficult to control water quality and renders them more exposed to weather.

1.1.1 Site selection

The selection of a suitable site for a hatchery is crucial to the cost of establishing and running the hatchery, and thus to the hatchery's economic efficiency. The better and more suitable the raw water quality is, the less water treatment is necessary, leading to a reduction in investment and running costs. Theoretically, hatcheries may also be established where the raw water sources are less than optimal, but these will require more water treatment, resulting in higher production costs. For sub-optimal sites, recirculation aquaculture systems (RAS) are an alternative because the amount of raw water that has to be treated will be reduced.

Normally, inlet pipe(s) represent an important cost in hatchery installation. The pipes can be up to several kilometers long, in order to get enough water of satisfactory quality. The same might be the case with the outlet pipes, in order to reach a depth and an area where contaminated outlet water can be sufficiently diluted and local pollution avoided. The ideal is, of course, to find a site where both a short inlet and outlet pipe can be used while still achieving satisfactory water quality. In addition, for optimum efficiency to be maintained, the raw water quality ought to be as stable as possible throughout the year in order to avoid both expensive systems for water quality regulation and fluctuation in water quality. If it is not possible to utilize gravity water and pumps have to be used, sites with lower lifting heads are favorable. Large tide differences offer no advantage regarding the pumping cost, unless the hatchery is established in the tidal zone and the tide is utilized for water exchange. The location of the inlet pipes when they meet the shore and that of the pumping station must not be too exposed to the elements. Waves can be particularly dangerous in this regard.

1.1.2 Brief characterization of water

Small, newly hatched larvae or fry in particular need a good water quality to achieve optimal growth and survival rate. Natural water may have a sub-optimal temperature – typically it is too cold but it may also be too warm – and water temperature regulation may be necessary. The gas saturation in the incoming water may also be sub-optimal – generally, this is due to a high content of nitrogen gas, or super-saturation. The oxygen content may also be too low, leaving the water under-saturated, resulting in a higher water supply than necessary. The CO₂ content may also be too high on some sites, such as those using groundwater. A high content of foreign particles in the water – typically a result of sand or clay – is also detrimental, as it may clog the gills. Water sources with too high content of particles should therefore be avoided. A high concentration of micro-organisms, such as bacteria, virus and fungi, is, of course, also unfavorable. The pH in the water, either alone or in association with dissolved metallic ions, may also be significant for the survival and growth rate.

For newly hatched fry it is of major importance that the water quality is stable; there should be no fluctuation. However, even if the raw water quality is stable, it might become unstable after water treatment. During treating, there will be reactions in the water of a chemical, microbiological or physical nature. Such reactions may take some time to be completed, meaning that the water composition may still be changing when the water reaches the production units, leading to instability. For this reason, it may be advisable to mature the water in large tanks with a long retention time to ensure that water quality is stable prior to its entry into the larva/fry tanks.

Another notable feature of water treatment in hatcheries is that water velocity in the production units must be very low. The water exchange rate will thus be low, as will the water supply to the production unit. Long water retention time in the production unit, together with high concentrations of organic substances/nutrients – such as dead larvae, feed loss, eventually live feed (rotifers and artemia) and microalgae – provide good conditions for the growth of micro-organisms and of biofilm. This often results in sub-optimal water quality in the rearing unit. Opportunistic, pathogenic bacteria may follow the raw water to the production unit or follow the added live feed when this is used in the production (Vadstein et al., 2004; Brunvold et al., 2007). Microbial maturation of the water prior to the production unit may thus be necessary to control growth of useful bacteria. Water quality inside the production unit is currently one of the major challenges in all hatcheries growing species with small larvae size or species using live feed.

1.1.3 The components in a system

The main components in any water supply system are the inlet pipe, the pumping station and the water treatment. The suitability of the last two components to the given water treatment depends on the raw water quality, the species grown and the intensity (number of kg of aquatic organisms per kg water supplied). For intensive hatcheries, water treatment typically includes units for particle removal, micro-organism control, heating/cooling, pH adjustment (freshwater sites) and degassing before the water reaches the production units.

1.2 The water supply and its main components 1.2.1 Inlet pipes

1.2.1 Inlet pipes

Inlet pipes are conventionally used to bring the water from the desired depth in the water source to the hatchery if gravity water is used, or to the pumping station if the water has to be lifted to the hatchery (Huguenin and Colt, 2002; Colt et al., 2008; Pulido-Calvo et al., 2008). It is also possible to utilize the tide to ‘pump’ the water into the hatchery or to place the hatchery in the tidal zone, but water quality control is more difficult in such cases. Materials commonly used in the inlet pipe are polyethylene plastic (PE) and PVC. PE is a low cost material that is eas...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Food Science, Technology and Nutrition
• Foreword
• Preface
• Part I: Reproduction and larval rearing
• Part II: Closing the life-cycle and overcoming challenges in hatchery production for selected invertebrate species
• Part III: Closing the life-cycle and overcoming challenges in hatchery production for selected fish species
• Part IV: Aquaculture hatcheries for conservation and education
• Index