New fish sterilisation method ready for trials

“We envisage that the technology we work with will be able to become a form of treatment for all fish transferred to sea in the future, said Mariann Dønnum, chief executive of Oslo-based ACD Pharma.

Dønnum told kyst.no that in ACD Pharma has been working on the development of the technology for more than five years.

“We have conducted numerous small-scale tank experiments where a number of parameters such as dose response have been evaluated. Based on the documentation that ACD Pharma together with partners in Baltimore have gathered, we hope to start clinical field trials, to look at the growth / feed conversion rate / fish welfare and more, during the year.”

Drug approval

These trials must be conducted to gather enough evidence for authorities to provide a drug approval.

Is this technology being used on fish that are being farmed today?

“No. The company is working on the development of a totally new concept for the production of sterile Atlantic salmon for an environmentally conscious Norwegian aquaculture industry. Our goal is to develop a method to produce sterile fish that only involves minimal intervention, and which only affects the development of reproductive organs. This avoids gender maturation with the problems it causes for both sexually mature fish and the rest of the cage.”

ACD Pharma has collaborated with Dr Ten-Tsao Wong and Professor Yonathan Zohar at the University of Maryland Baltimore County (UMBC) to develop a "silencing" technology for bath treatment of eggs for the production of sterile fish.

Fish develops normally

“The strategy is to use a compound that, for a short period of time very early in the development, blocks a gene necessary to develop genital cells. Once the fish has developed and the link that blocks the genetic cell development gene is broken down, the gene is again functional for the fish.”

Dønnum says that in the short-term experiments in both zebrafish and salmon have shown that if you block this gene gametes are prevented from finding their way to the genitals / gonads.

“The fish develops quite normally and has normal genitals, but it has also no germ cells and therefore cannot reproduce. The consequence is that a fish is sterile without other physiological processes being affected,” she explains.

She states that the method does not involves making changes in the DNA of salmon, which would otherwise be regarded as genetic modification (GMO).

Easily integrated

“We have a strategy where we only specifically "turn off" the gene for a short period of time, very early in the salmon development. This means that the treatment can be done as early as the unfertilised egg. This is the first time a non-GMO silencing technology, which can be easily integrated into the production process of eyed eggs, has shown good results,” she says.

She says that maturation in farmed fish is a global problem.

“Both in Tasmania, Chile and the east and west coasts of North America the proportion of sexually mature salmon in the latter part of the production cycle is generally greater than in Norway. This may be due to a combination of inferior breeding stock and less use of light.

“The need for sterile fish is thus as great in other salmon producing countries as in Norway. The method is not limited to salmon, either. The technology could be adapted to other farmed species both nationally and internationally. These are markets we want to enter when the technology is established on salmon.”

How far would you say you have come in relation to the commercialisation of the product / technology?

“We are working on getting large-scale field trials started, and obtaining the documentation required by the authorities. We see for ourselves that the technology we are working on could be a form of treatment for all fish that is put into the sea in the future, desired by both authorities, environmental organisations and not least the breeders themselves. We consider the potential for this form of treatment is significant.”

Industry's reputation

Dønnum says an introduction and use of sterile fish in aquaculture, is the wish of both the industry itself, river owners, central government and various environmental organisations.

"For the aquaculture industry, the work of this method to prevent gender maturation will be important for the industry's reputation," she says.

She notes that several methods of sterilisation have been tested, including trials of triploid fish, which have an extra set of chromosomes.

“Until now, unfortunately, none of these methods have shown satisfactory results either in terms of animal welfare or performance characteristics, despite many years of active research.”

The technology will also help to increase the quality of the fish.

“Norwegian salmon farming is still experiencing a very costly downgrading of approximately 4.3 per cent due to maturation. This despite the fact that late maturation has been one of the most expressed breeding objectives for many years. For egg producers sterile fish be a welcome opportunity to protect their distinctive roe bloodlines.”