Rainbow trout (Oncorhynchus mykiss) – Current status … · Current status of selective breeding...

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The research leading to these results has received funding from the European Union's Seventh Framework Programme (KBBE.2013.1.2-10)

under grant agreement n° 613611. www.fishboost.eu This publication reflects the views only of the author, and the EU cannot be held responsible for any use which may be made of the information contained therein.

Rainbow trout (Oncorhynchus mykiss) – Current status of selective breeding in Europe

Kasper Janssen1, Hervé Chavanne2, Paul Berentsen1 and Hans Komen1

2015

1: Wageningen University

2: University of Padova

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Table of Contents 1. Introduction ..................................................................................................................................... 3

2. Materials and Methods ................................................................................................................... 4

2.1. Characteristics of breeding companies ................................................................................... 4

2.2. Egg production ........................................................................................................................ 5

2.3. Market share of breeding companies ..................................................................................... 5

3. Results ............................................................................................................................................. 5

3.1. Characteristics of breeding companies ................................................................................... 5

3.2. Egg production ........................................................................................................................ 7

3.3. Market share of breeding companies ..................................................................................... 8

4. Discussion ........................................................................................................................................ 8

5. Conclusion ..................................................................................................................................... 11

6. Acknowledgements ....................................................................................................................... 11

7. References ..................................................................................................................................... 11

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Summary This report provides information on the current status of selective breeding of rainbow trout

(Oncorhynchus mykiss) in European aquaculture. A survey among breeding companies provided

insight into the main characteristics of breeding companies and their egg production. Data on

national egg production were collected in order to estimate the market share of eggs produced by

breeding companies in the total European egg production. Compared to other aquaculture species,

relatively many breeding programs for trout exist. Six breeding companies perform mass selection

and selected traits include growth performance and morphology. Nine breeding companies perform

family selection and selected traits include growth performance, morphology, disease resistance and

reproduction related traits. Illustrative for the achieved genetic gain is a threefold increase of the

thermal growth coefficient of strains of breeding companies compared to wild strains. Up to 14

generations of selection have been performed in family selection and up to 20 in mass selection. In

20111 an estimated 1543 million eggs were produced in Europe of which 1006-1048 million

originated from breeding companies. Therefore the market share of breeding companies in the

European production was 65-68%.

1. Introduction Rainbow trout is one of the main aquaculture species in Europe: its production exceeds 250 million

tonnes with a value close to 700 million Euro (table 1). The major producing countries are Norway,

Italy, France and Denmark. Rainbow trout is a highly versatile species which is reflected by its wide

geographic distribution and the various culture methods applied. Trout production methods are very

diverse and vary from freshwater ponds where trout is grown to portion sized fish of 300g to sea

cages where it is grown up to a size of 3.5kg.

1 At the start of this study production data of 2012 were not available yet, hence 2011 data were collected.

Table 1. Rainbow trout production volume in Europe in 2012

Country a

Portion size b

(<1.2kg)

(tonnes)

Large fish b

(>1.2kg)

(tonnes)

Total production b

volume

(tonnes)

Production c

value (1000 €)

Denmark 21 415 10 491 31 906 76 691 Finland 0 9 000 9 000 30 010 France 23 500 12 500 36 000 88 553 Germany 11 713 1 278 12 991 30 173 Italy 1 500 36 300 37 800 86 017 Norway 0 75 000 75 000 226 147 Poland 14 500 0 14 500 24 603 Spain 14 400 1 600 16 000 39 643 Sweden 0 10 499 10 499 33 339 United Kingdom 2 000 10 996 12 996 32 100

Total 132 824 123 868 256 692 667 276 a Countries with a production <3000 tonnes are not presented

b (FEAP, 2014)

c (FAO, 2014)

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Rainbow trout is native to the Western part of North America and the Kamchatka region in the North

East of Asia. During the period 1880-1900 it was extensively introduced from the USA to many

European countries, quickly followed by secondary intra-European transfers (Crawford & Muir,

2008). Many of these first egg shipments originated from fish of the McCloud river in California and

these fish have formed the genetic basis for modern trout farming (Gall & Crandell, 1992 ; Gross et

al., 2007). The intent of these early introductions was the development of recreational fisheries

(Crawford & Muir, 2008). The hatcheries at that time were part of (re)stocking programs and in the

selection of broodstock most emphasis was placed on the improvement of fecundity, early sexual

maturity and off-season spawning (Gall, 1975 ; Donaldson & Olson, 1957 ; Millenbach, 1950). The

oldest European rainbow trout hatchery was run by Howietoun Fishery in Scotland, which imported

rainbow trout in 1892/1893 (Hill, 1995 ; Gall & Crandell, 1992). One of the first hatcheries in

Germany started its operations in 1896 (Hofer_Forellen, 2014). Aquaculture of rainbow trout started

to develop in the 1950’s (Paisley et al., 2010). In the 1970’s multiple hatcheries performed selection

schemes with the aim to improve traits relevant for aquaculture, although the scientific basis of

these breeding programs was limited (Guyomard, 1981 ; Morkramer et al., 1985 ; Gjedrem, 2012 ;

Aulstad et al., 1972). Since then huge scientific progress has been made in the field of genetics and

multiple advanced selective breeding programs for rainbow trout have been established.

It is evident that all rainbow trout which is currently produced in Europe has experienced some

degree of domestication. On the other hand it is unclear to what extent advances in selective

breeding techniques have been adopted by European breeding companies and what part of the

current production originates from breeding companies. Therefore this report aims to:

1. Describe the main characteristics of breeding companies.

2. Estimate the market share of breeding companies in Europe.

2. Materials and Methods

2.1. Characteristics of breeding companies In a first survey conducted in collaboration with AQUATRACE2, questionnaires were distributed

among 15 breeding companies in Europe. Breeding companies were identified by the

AQUABREEDING3 research project, complemented by internet search and snowball sampling

(Goodman, 1961). This first extensive questionnaire included questions related to the type of

selection, the number of selected generations, selected traits, the application of genetic markers and

genomic selection, the monitoring of inbreeding, protection strategies and the quantity of eggs

produced.

As not all companies completed the extensive questionnaire, a second survey was carried out

involving a limited number of questions. The aim of this survey was to identify whether a breeding

2 AQUATRACE - https://aquatrace.eu/ - 7

th Framework Programme for research (FP7)

3 AQUABREEDING - 6

th Framework Programme for research (FP6)

https://aquatrace.eu/

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company employed family or mass selection and how many eggs it produced in 2011. The market for

selected seeds is dominated by the trade in eggs, hence the production of juveniles was ignored.

2.2. Egg production The total European egg production was calculated as the sum of all national egg productions.

National egg production statistics are not routinely collected in many countries. For countries of

which the egg production was unknown, it was estimated from the quantity of eggs used in

production, import and export of eggs. The quantity of eggs used in production was estimated from

fish production, assuming a mean harvest weight and survival.

2.3. Market share of breeding companies The market share is defined as a firm’s sales relative to the total sales of all firms in the same industry

(Ghosh, 2004). Here it is used as the total egg production of European breeding companies relative to

the national and relative to the total European egg production. Both surveys provided information on

the quantity of eggs produced per breeding company. These data were compared to national and

European egg production statistics in order to estimate market shares. On a national level the market

share of breeding companies was determined by comparing the pooled egg production of breeding

companies per country to the national egg production. On a European level the market share of

breeding companies was determined by comparing the pooled egg production of breeding

companies to the total European egg production.

3. Results

3.1. Characteristics of breeding companies Of the nine breeding companies that completed the extensive questionnaire of the first survey, three

performed mass selection and six performed family selection (table 2). All companies applied

artificial fertilisation and in most cases one male was mated to two to four females. The number of

selected lines varied between 1 and 8. In 2014 the number of selected generations varied between 1

and 14 in the companies that performed family selection and between 3 and 20 in companies that

performed mass selection. Considering a three year generation interval the oldest family selection

program started in 1972 (AquaGen, 2015) and the oldest mass selection program started around

1955. The companies with a smaller number of selected generations often started their current

breeding program with material from a previous breeding program.

The companies that performed mass selection, selected mainly on growth performance and

morphology. Next to growth performance and morphology, the companies that performed family

selection also selected on traits related to processing yield, product quality, disease resistance,

reproduction and feed efficiency. Most companies monitored the rate of inbreeding and genetic

fingerprints for parentage assignment were commonly applied. Two companies indicated to apply

marker assisted selection and none of the companies applied genomic selection. Strategies to

protect the genetically improved material from further use included sterilisation, genetic traceability,

hybridisation with other species and in one case the introduction of recessive alleles.

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An additional six companies participated in the second survey, hence the egg production data of 15

companies were collected. It was expected that over 95% of the European egg production by

breeding companies originates from the survey’s participants. The breeding company with the

highest egg production produced 210 million eggs (figure 1). The three biggest companies together

produced 60% of the total egg production by breeding companies. There was no evident relation

between the scale of production and the selection strategy employed. Of the total egg production by

the 15 breeding companies that participated in the surveys, over 75% was produced by the nine

companies that performed family selection.

Figure 1. The egg production of the 15 rainbow trout breeding companies in Europe in 2011.

0

50

100

150

200

250

f f f m m f f f f m f f m m m

Egg

pro

du

ctio

n (

mill

ion

)

Light blue bars indicate uncertainties in egg production

m = mass selection f = family selection

Table 2. Traits in selection of rainbow trout breeding companies in Europe

Selected traits Mass selection a Family selection

a

Growth performance 3 6

Processing yield 1 3 Product quality 1 2 Disease resistance 0 4 Reproduction (maturity, fecundity)

0 5

Morphology 3 4 Feed efficiency 0 2 a Number of respondents that performed selection on a trait. Nine companies completed the questionnaire, of

which three applied mass selection and six applied family selection

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3.2. Egg production The total European egg production was 1543 million (table 3). The major egg producing countries

were Denmark, France, Italy and Spain.

For several countries official egg production statistics were lacking and had to be derived. The French

egg production was estimated based on the assumption that approximately 90% of the egg

production originated from the breeding programs in the survey (Haffray, 2015). The Polish egg

production was estimated from fish production assuming a mean survival of 35% and a harvest

weight of 350g, corrected for the import of 8 million eggs (Anonymous, 2015). The egg production in

Sweden was estimated from production assuming a mean survival of 45% and a harvest weight of

2kg (Funcke, 2015). The number of eggs used in production in England and Wales was estimated at

39 million, based on a fish production of 6 824 tonnes (Reese, 2013), an egg to harvest survival of

50% and a harvest weight of 350g. This figure was used together with data of Northern Ireland

(DARD_Fisheries, 2014) and Scotland (Munro & Wallace, 2012) to estimate the egg production in the

UK.

On a European level 71.2 million eggs were exported from Denmark to Chili (Sernapesca, 2014).

Additional exports were directed to Northern Africa and Eastern Europe, but the quantities were

unclear. It is noteworthy that despite its large production (75000 tonnes) of rainbow trout, Norway is

not a major producer of eggs. Most of the Norwegian eggs are used in domestic production and

many eggs are imported. As Norway produces large trout and survival is generally high, relatively few

eggs are required per kg fish production.

Table 3. Production of eyed eggs of rainbow trout in Europe in 2011

Country Production (million)

Reference

Denmark 324 (Thomsen, 2014)

Finland 21 (Kause, 2014)

France 400 (Haffray, 2015)

Germany 13 (Bundesamt, 2012)

Isle of Man 50 (Dentler, 2015)

Italy 265 (Grossi, 2014)

Norway 40 (Korsvoll, 2014)

Poland 110 Estimated from fish production

Spain 259 (Ministerio_de_Agricultura, 2014)

Sweden 13 Estimated from fish production

United Kingdom 48 (DARD_Fisheries, 2014 ; Reese, 2013 ; Munro & Wallace, 2012)

Total 1543

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3.3. Market share of breeding companies The combined egg production of the 15 breeding companies was 1006-1048 million (figure 1),

corresponding to 65-68% of the total European egg production (table 3). The market share of

breeding companies on a national level is illustrated in figure 2. The countries with the largest

quantity of egg production by breeding companies were Denmark, France and Spain. The breeding

companies were located all over Europe.

Figure 2. The distribution of rainbow trout breeding companies across Europe, the egg production per

country and the national market share of breeding companies in 2011.

4. Discussion The production strategies among trout producers differ greatly and therefore different breeding

objectives can be expected among breeding companies. For example flesh colour and late sexual

maturation are unimportant traits in the production of portion sized fish, but they are important in

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1

1

2

1

1

2

1

1

= Number of breeding companies

= Total egg production

= Market share of breeding companies

..

0

0

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large trout production. In general only a few productivity related traits are of importance for the

production of portion size trout, while for large trout a broader breeding objective is required which

includes traits related to product quality and sexual maturation (Sae-Lim et al., 2012). Mass selection

can only be performed on traits that are measured on the selection candidate itself, while in family

selection related individuals can be used to measure traits for which the animal is sacrificed (e.g.

disease resistance, processing yield) allowing for a more sophisticated breeding strategy. Therefore it

could be expected that breeding companies that perform mass selection direct their sales primarily

to producers of portion size fish, while breeding companies that perform family selection are better

suited to serve both portion size and large trout producers. Indeed based on the company websites

such a segregation of markets appears to exist to some extent, where companies that perform family

selection commonly supply both portion size and large trout producers.

There is a lack of reliable data on egg production and trade in Europe. These data are not recorded

on a European level and national data are often fragmented or incomplete. The derivation of a

quantity of eggs used in production from national fish production statistics is not accurate due to a

general lack of production performance data such as survival and mean harvest weight. These

problems could be overcome by the routinely collection of data, for example as performed by a

survey among fish farmers in Scotland (Munro & Wallace, 2012).

With respect to the coverage of the surveys it is expected that all larger companies were included in

the surveys, as they are well known. Possibly some small scale breeding companies were not

included in the survey, but it is expected that over 95% of the European egg production by breeding

companies originates from the survey’s participants. Thereby the potential effect of missing

companies on the estimated market shares is limited.

When compared to Atlantic salmon, breeding of trout is remarkably different. Compared to seven

companies that operated breeding programs for salmon in Europe in 2012, the number of breeding

companies for trout is surprisingly large, especially considering that the production of salmon is six

times larger than that of trout. While breeding companies of salmon have a rather uniform

organisation, breeding companies of trout are quite diverse. The relatively large number and

diversity of trout breeding companies may be explained by three factors. First of all trout is produced

all across Europe (table 1), as opposed to salmon which is only produced in the North Western part.

Secondly culture systems and production strategies are highly variable, demanding different genetic

properties of the stocking material. The wide range of conditions that trout are exposed to results in

a strong genotype by environment interaction (Sae-Lim et al., 2013). Therefore different breeding

companies may be best suited to serve different markets. The third factor is the difference in roles

that breeding companies play in trout production. Roughly three types of breeding companies can be

distinguished, that appear to be mutually exclusive:

1. National research institutes that operate a breeding program.

2. Companies that integrate a breeding program in the production process.

3. Companies that specialize on breeding.

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The first type of breeding company aims it production at the national market, is supported by

government subsidies, has a firm knowledge base for its operations and cooperates closely with the

local industry. Due to government support and its objectives in research and development, it is

relatively insensitive to competition from other players. There are two breeding companies of this

type in Europe.

The second type includes companies that have integrated the breeding program in the entire

production process, either in one company or a cooperative of multiple farmers. The integration of

the breeding program in the entire production process offers the advantage of a farm specific

breeding program with a high degree of control by the farmers themselves. Thereby this type of

breeding company does not experience a high degree of competition. There are five breeding

companies of this type in Europe.

The third type of breeding companies includes those of which the breeding program is the core

business. These companies supply eggs to an international market in which they experience

competition from other breeding companies. In Europe eight such companies are active and they

largely correspond to the top eight producers in figure 1. It is expected that the number of breeding

companies in this category will decrease in time, following the same trend as observed in other

livestock species.

Selective breeding has resulted in improvements of many different traits and most illustrative for the

achieved genetic gain may be improvements in growth performance. Different values for the genetic

gain on growth performance per generation have been published in literature. Gjerde (1986)

reported a 10-13% increase in growth rate per generation and Kause et al. (2005) reported an

average 7% increase per generation. As genetic gain is cumulative, it can be expected that trout that

has been selected for several generations grows much faster than wild trout in the same rearing

conditions. The thermal growth coefficient (TGC) is a temperature corrected measure of growth

performance and can therefore be used to compare the growth performance across different

environments (Cho, 1992 ; Iwama & Tautz, 1981), although factors other than temperature also play

a role and are not included. When fed ad libitum the TGC of feral juvenile rainbow trout was 0.67

g(1/3)(°C d)-1 (Martens et al., 2014 ; Martens, 2013). Tymchuk and Devlin (2005) studied the growth of

wild rainbow trout fed ad libitum. At a constant temperature of 11°C at 637 days after fertilisation,

the fish reached a weight of about 47g, corresponding to a TGC around 0.5 g(1/3)(°C d)-1. A much

higher growth performance has been reported for strains that have been selected for several

generations. (Sae-Lim et al. (2013)) reported TGC values of 1.43 to 2.07 g(1/3)(°C d)-1 for variety over

culture systems around the globe in 2009/2010. (Grisdale-Helland et al. (2007)) reported TGC values

of 2.43 to 2.53 g(1/3)(°C d)-1 for a commercial strain that was grown from 400 to 850 g in seawater at

11 °C. At the USDA National Center for Cool and Cold Water Aquaculture strains from three different

suppliers of the European market were tested for their growth potential during nine months at a

temperature around 11 °C. They found TGC values of 2.05, 2.09 and 2.40 g(1/3)(°C d)-1 for the three

different strains, corresponding to a growth from about 6 grams to a final weight of 700-1000g

(Cleveland, 2015). Assuming an average TGC of 0.6-0.7 g(1/3)(°C d)-1 for wild trout, it can be concluded

that the TGC of commercially available strains is roughly three times as high as that of wild strains.

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5. Conclusion 1. There are 15 breeding companies in Europe of which 6 perform mass selection and 9

perform family selection.

2. Commonly selected traits are related to growth, morphology, processing yield, disease

resistance and reproduction.

3. In 2014 the highest number of selected generations in family selection was 14 and 20 in mass

selection.

4. The market share of breeding companies in the total European egg production was 65-68% in

2011.

5. Selective breeding has resulted in a threefold increase in TGC of strains of breeding

companies compared to wild strains.

6. Acknowledgements This work is the result of the collaborative effort of researchers in the FP7 projects ‘Aquatrace’ and

‘Fishboost’. We gratefully acknowledge the contribution of the companies that participated in the

surveys. We also acknowledge the contribution of the national statistic institutes in several countries

that helped us to collect the relevant data on the trade and production of eggs.

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