Photo by Tom Chan. Source: The Nature Conservancy

Oyster hatchery pursues vision of sustainable aquaculture

5 December 2022

Marine scientists develop an initiative to help Hong Kong’s centuries-old oyster farms thrive in a sustainable way. Researchers from the University of Hong Kong discuss how they are leading the way to oyster aquaculture’s future as well as the social, ecological, and economic impacts.

Oyster aquaculture has been around for centuries in Hong Kong, but growers now face critical threats to their livelihood, such as pollution and climate change. To help the industry thrive sustainably, marine scientists at the Hong Kong Oyster Hatchery & Innovation Research Unit using the funding support from government-established Sustainable Fisheries Development Fund in close collaboration with local oyster growers, Deep Bay oyster growers association, and the oyster industry, such as Lee Kum Kee Ltd, and moreLeading the project to set up the hatchery is Dr Thiyagarajan Vengatesen of the Swire Institute of Marine Science, referred in this interview by its acronym SWIMS, and the School of Biological Sciences at the University of Hong Kong. He shares his insights about its aims and progress so far.

Why are oyster hatcheries important?

Dr Thiyagarajan Vengatesen leads the team at the Hong Kong Oyster Hatchery and Innovation Research Unit. Source: HKO-HIRU

Oysters grow from ‘seeds’ – immature larvae – that are then distributed across an oyster bed and left to grow on ropes. In Hong Kong, these seeds are sourced from the wild, but because of the threats that face oyster aquaculture, we need to make sure to grow and distribute seeds with useful properties, such as high heat or salt tolerance. This is where our hatchery comes in.

For example, oysters usually experience mortality in the summer when temperatures are high and their immune systems are weakened, leaving them vulnerable to pathogens. But as oyster farming has been pushed further out of estuaries into saltier water, and as the waters warm up under climate change, we are seeing oysters dying off in the summer.

These infections can spread rapidly, making business uncomfortable for growers who can lose their whole stock. We need high salinity and high stress tolerance seeds that are suitable for growing in these areas.

How can the hatchery help improve the sustainability of oyster aquaculture?

We aim to help make oyster aquaculture in the region more sustainable in three dimensions: socially, ecologically and economically.

The oyster is very much in the heart of the people of Hong Kong and southern China because it’s an indigenous, endemic species, which has been cultivated for hundreds of years. Oyster aquaculture is largely a family business though, so while we are working to increase production and income, we have to maintain that traditional relationship and sense of social sustainability.

Ecologically, oyster aquaculture is a green industry because it requires no food input – the oysters feed naturally in the water. On top of this, they filter out nitrogen, which is in excess in the relatively polluted coastal areas of Hong Kong and southern China. These species are playing an important role in maintaining ecological sustainability in the coastal areas.

Hatchery technology has been developed in other oyster areas like the US and Australia, but we need our own technologies for our specific setting and uses. For example, here the oyster meat is mostly extracted and used for cooking, so the shells are not as important.

The technologies we develop will have these considerations in mind, and we will disseminate them to the local growers by inviting them into the hatchery and sharing the results with the community. Our aim is that within five years we will be able to increase the value of oysters so it can be an economically sustainable business for growers.

The hatchery began operations this summer. What has happened so far?

Our aim is to create new strains of oyster suited to the local environment through breeding. The wild population has a variety of features, and those that live in very polluted areas have been naturally selected for high stress tolerance. Our work is to identify these strains and verify their genes for stress tolerance, ensuring they can be inherited. We also need to regularly bring in new strains to reduce the chance of genetic bottlenecks that will compromise the longevity of the strains.

We are also working to produce seeds in a confined space. Space and labour are limited in the area, so we need to show how we can increase production in as tiny space as possible. We recently brought the growers and stakeholders together to show them how the hatchery is capable of producing seeds in a small area with a relatively small amount of investment. Our hatchery is around 2,000 square feet in area, and we are able to produce several million seeds.

The interdisciplinary team of researchers from marine biology, mechanical engineering, molecular biology and materials science background work together to develop modern and sustainable aquaculture technology. Source: HKO-HIRU.

What do you hope the hatchery will look like in five years?

I would like to see our hatchery well established at the University of Hong Kong and focusing more on developing new strains and new technologies, for the growers in Hong Kong and southern China but also for around the world. Once we address the basic requirements and basic technology that’s needed for the local growers, we will move onto to more advanced technology development through our research innovations.

I would also like to see a couple of commercial hatcheries set up in Hong Kong following technology we developed with scientists that we have brought together here. It would be good to see them economically sustainable, with Hong Kong oyster seeds seen as high value across southern China.