Getting picky with paua: selective breeding to improve productivity
Jane Symonds and Phil Heath are working with industry partners to develop superior broodstock.
There’s a high demand worldwide for the seafood delicacy known here as paua, and elsewhere as abalone. A decline in wild stocks due to over-fishing and poaching means that the global market for this tasty gastropod is greatly undersupplied. In New Zealand, the black-footed paua (Haliotis iris) is commercially fished, and farming trials have been conducted since the 1980s. Paua farming has excellent potential for further development in New Zealand because of strong overseas demand and high prices; the goal is to exceed 100 tonnes per annum of farmed paua production over the next few years.
NIWA scientists developed techniques for hatching paua in the 1980s and now we are working on the challenges of growing paua to marketable size. A key issue for paua farmers is slow growth: it can take over four years for a cultured paua to reach current market size of 85–100 mm. This is where NIWA scientists specialising in broodstock development and selective breeding can help.
Taming the wild paua
Most people are aware of the importance that farmers placeon stud animals for breeding. The careful selection of the best performing farm animals has progressed for centuries, and livestock-improvement companies invest heavily in selective breeding programmes to improve stock performance and increase productivity.
Compared to terrestrial farming, marine farming is a relatively new activity. Consequently, high-performing selected stocks have been established for only a few of the major fish species, with most marine farmers relying on wild caught fish and shellfish for breeding stock. This is the case for paua and currently much of the paua farmed in New Zealand comes from wild-caught parents. With wild broodstock, farmers cannot know whether the offspring will be fast-growing or slow growing. Recognising the significant opportunity selective breeding offers to improve performance, NIWA scientists have established a broodstock-development programme for paua at our Mahanga Bay facility in Wellington.
NIWA’s paua broodstock development
For several years, we have collaborated on selective breeding with the paua aquaculture industry, in particular with OceaNZ Blue Ltd, based at NIWA’s Bream Bay Aquaculture Park. As part of this work, wild paua broodstock have been collected from several locations around New Zealand to breed for evaluation. One of the goals of a successful programme is to generate enough offspring to be able to identify and select the families that perform better than the others. To achieve this, around 100 adults must be ready to spawn at exactly the same time. The paua broodstock have therefore been nurtured in a carefully controlled environment – a combination of lighting,water flow and temperature, and feeding – to ensure that they are all in spawning condition at the desired time.
To induce spawning, we place specific males and females into individual tanks and soak them in a dilute solution of hydrogen peroxide. This induces a hormone change in the paua and they spawn a few hours later. By placing the paua in individual containers, we can collect eggs and sperm separately and set up specific crosses by fertilising the eggs from one female with the sperm from one male. The resulting ‘family’ can then be reared as an identifiable group until they are big enough to be tagged (about 15 mm) by fixing coloured numbered discs to their shells. Once tagged, individuals can be easily tracked throughout their life in the culture facility and can be reared communally with other families, reducing the risk that differences in growth between families are caused by their rearing environment.
Selecting the best paua families
NIWA’s paua-family selective breeding programme, which commenced in June 2007, builds on a 2003 industry-led broodstock development initiative. In the new programme,individual families have been established and are being reared separately until tagging in March 2008. The tagged individuals from all families will then be grown together for four years before we can identify the best performing families.
There’s a risk that the early rearing environment may have an influence on growth later in life and thus impact family performance. To test this, the same families have also been reared together right from fertilisation and we will later use their DNA fingerprints to identify their parents. This will show us how the families perform under both types of conditions. Understanding the influence of environment on family performance is important for all shellfish and fish-breeding programmes.
The next steps are to determine which families are the best performers, and also to select the best individuals to be the parents of future generations. We will track growth rate and survival until the paua reach market size, and analyse the data to identify the best families and the best individuals within each family. We aim to breed from the best when they reach sexual maturity at 4–5 years.
Animal breeders have developed complex mathematical models to analyse this sort of family data and to estimate the ‘breeding value’ or potential for each individual to pass on a benefit to the next generation. All the potential parents can be ranked based on their breeding values for different attributes of economic value, such as growth, product quality, and yield. These high-performance broodstock are valuable assets at this stage and can be used to create the next generation of offspring for farming.
Benefits for the future
The ultimate goal of the project is to produce paua that grow rapidly to market size and yield a premium-grade product for the consumer. Based on other studies, we estimate a trait such as growth can be improved by 10–20% per generation. Improved growth can reduce the time to harvest, or provide the market with larger individuals.Either way the economic reward is considerable. For example, at current costs, a 15% increase in growth rate could save an industry based on 100 tonnes of paua per year over half a million dollars in production and infrastructure costs. It may be a while before we see prize paua ‘bulls’ at aquaculture shows, but establishing a broodstock programme alongside the developing paua industry is essential to ensure the future success of paua farming in New Zealand.
Teachers’ resource for NCEA Achievement Standards or Unit Standards:
Aquaculture Level 2 US17254
Biology Level 1 US6299,Level 2 AS90459, US8929
Economics Level 1 AS90196
Geography Level 1 AS90204, US5085