Aquaculture’s contribution to the global supply of fisheries products has grown from 4 percent in 1970 to over 50 percent today. However, that capability faces constraints, and aquaculture’s productivity may not be sustainable due to extreme weather situations like the current El Niño weather phenomenon in the Philippines.
While genetic engineering applications to aquaculture research is at its incipient stage worldwide, the technology has great promise in helping the sector mitigate the adverse impacts of climate change, and sustain its contribution to world’s fish supply.
This is according to Dr. Eric Hallerman, a professor at the Department of Fish and Wildlife Conservation at Virginia Polytechnic Institute and State University.
He discussed how biotechnology could contribute to climate change resiliency of aquaculture and fisheries during a webinar via Zoom organized by the International Service for the Acquisition of Agri-biotech Applications, Inc. (ISAAA Inc.) on March 31.
Aquaculture is a diverse sector with about 600 cultured species, as the Food and Agriculture Organization (FAO) of the United Nations reported.
However, only 15 species contribute significantly to world production.
With the prevailing and worsening conditions brought about by climate change to the fishes’ natural habitats, tools that can improve the species’ resiliency are necessary.
Hallerman presented gene transfer and gene editing as promising techniques to shield the world’s aquaculture from the climate crisis.
“Fishes are excellent systems for gene transfer and gene editing,” Hallerman pointed out.
The main reason behind this is that fish can produce multiple offspring. At the same time, researchers have designed protocols for the successful artificial induction of spawning in cultured fish species.
Furthermore, fish eggs are large, and the development of the embryo or larvae occurs outside the mother’s body, enabling successful modification of valuable traits in fish.
Gene editing has been used to improve fish species’ productivity, disease resistance and sustainability.
The current thrust of aquaculture research worldwide is to improve fish species’ growth and muscle development.
The growth hormone gene has been successfully employed in Nile tilapia, channel catfish, carps, loach, and other species through traditional gene transfer.
A research breakthrough occurred in 2015 when Aquabounty, a US biotech firm, developed the AquAdvantage Atlantic.
Approved for commercialization by the US Food and Drug Administration, a genetically engineered salmon grows rapidly, causing the production time to be halved and feed efficiency boosted by 10 percent.
It was the world’s first commercialized product of animal biotechnology. Besides the US, AquAdvantage is also available in Canada and pending approval in other countries.
Inspired by a double muscling that naturally occurs in some cattle breeds, scientists have used gene editing to knockout fish’s myostatin gene. This technique has been proven effective in increasing the muscle growth of Nile tilapia, common carp, rainbow trout, yellow catfish, olive flounder, and other species.
In 2022, Japan approved the production of two fish species exhibiting doubled muscle production. The red sea bream and tiger pufferfish, developed by the Regional Fish Institute, are sold online in Japan and recognized as no different from conventionally-bred fish.
With the advent of extreme weather situations, biotech applications in aquaculture have expanded to improving fish species’ resilience to climate change.
One focus of this research is improving tolerance of fish to heat stress. This has been achieved in earlier studies employing conventional selective breeding and molecular marker-assisted breeding.
The current thrust of aquaculture research is finding molecular targets for gene transfer or gene editing.
Hallerman also mentioned the need to edit aquatic species’ hemoglobin to improve their oxygen uptake.
This research thrust has a great promise for sustaining productivity in the Philippines’ milkfish industry.
Largely grown in land-based bonds in Pangasinan, milkfish farms are highly densely populated, which subjects fish stocks to physiological and social stress.
Fish kills are not uncommon particularly in hot weather phenomenon, like what the country experiences these days.
High fish densities in ponds increase susceptibility of fish stocks to parasites and pathogens, making genetic improvement for disease resistance a high breeding priority.
Researchers from the University of Idaho and partners successfully knocked out a gene in grass carp which led to a reduced viral infection that causes hemorrhagic disease affecting the kidney cells.
Besides fish, protocols for gene editing of other aquaculture species have been published. University of China researchers have used the CRISPR system in Pacific oyster eggs, addressing the challenge of editing mollusks’ tiny eggs distributed in the water column.
CRISPR, which stands for Clustered Regularly Interspaced Short Palindromic Repeats, is the most popular gene editing tool. It was designed based on some bacteria’s natural gene-editing system and works like molecular scissors to cut a particular DNA sequence to improve the quality of the target plant or animal.
For crustaceans, which fertilize internally, the Chinese Academy of Sciences has used CRISPR for ridgetail white prawns. There are no reports yet about the use of gene editing in seaweeds.
“Biotechnology can make unique contributions that classical breeding cannot,” Hallerman concluded.
However, biotechnology will only serve those contributions by conducting more fundamental research on molecular mechanisms for critical traits, risk-scaled enabling policies, and better public understanding and acceptance of the technology.
Applications of biotechnology in aquaculture will only be available to help address food security and mitigate climate change, with the approval of the concerned government agencies to put animal biotechnology regulations in place, pointed out Dr. Ramon Clarete, chief of party of Building Safe Agricultural Food Enterprises (B-SAFE), a US Department of Agriculture-funded Food for Progress program.
B-SAFE, in partnership with ISAAA Inc., has been conducting webinars on biotechnology to assist the public in understanding the benefits and potential of biotechnology. Through these continuous activities, the general public is being helped to become aware of biosciences’ power in improving people’s lives.
Kristine Grace Tome is a Program Officer at ISAAA Inc.
Image credits: WorldFish Center