Sablefish (Anoplopoma fimbria), also known as black cod or butterfish, is a relatively new marine aquaculture species in the United States and Canada, but wild stock of this tasty, buttery fish have been harvested since the late 1800s by west coast fishermen. Indeed, sablefish are currently the highest valued finfish per pound in Alaskan fisheries. And the largest consumer of the species is Japan.
The all-female production of sablefish has been a near-term goal for researchers at NOAA’s Northwest Fisheries Science Center in Seattle who have recently developed a 100% female generation of the species. The goal is to boost production value and efficiency for hatcheries and farms since females grow faster than males and are up to 30% larger at 24 months in aquaculture environments.
Dr. Adam Luckenbach
Dr. Adam Luckenbach collecting data on sablefish reared in the net pen system at NOAA's Manchester Research Station.
At the forefront of this research is Adam Luckenbach, PhD, a Research Physiologist for NOAA who conducted his postdoctoral work at the University of Washington. Adam's areas of expertise include reproductive and growth physiology and sexual differentiation in fishes. He and primary collaborator Bill Fairgrieve, PhD, started working on monosex female production of sablefish in 2011. They wanted to determine if it was physiologically possible to manipulate the phenotype of females during early sexual development.
Early in their research, Adam and Bill determined that sablefish were genetically sex determined (GSD) as opposed to some types of fish and reptiles that are environmentally, or temperature- dependent (TSD). This made working with this species a little trickier, as it required a genetic override rather than just controlling temperature during incubation.
But the researchers were up for the challenge, and with sablefish bringing in up to $10 a pound it proved to be a worthy species for continued effort. So in 2011 a new generation of neo-males was born, or more importantly, created.
Today the magic happens in an aquaculture facility at the NOAA Manchester Research Station in Washington State where the next generation of “neo-males” are being raised. These are genetically female sablefish that are hormonally induced to become phenotypically male. This means that while the fish is still chromosomally “XX,” it can now produce sperm which will also only contain “X” chromosomes.
Typically, the process of masculinization of females is induced by a brief oral administration of androgen methyltestosterone through feed in the early stages of sex differentiation. This occurs at least two years prior to maturation and their subsequent use as broodstock. The sex reversed females (neo-males) can then be crossed with female stock and used to produce a “treatment-free” generation of all-female XX individuals. At about 24 months this all-female stock of sablefish can then be used for consumption and will be a full generation removed from the neo-male parental stock.
In 2014 that first generation of neo-males were crossed with females, resulting in 100% female offspring. Those females were examined and … success … they proved to have normal ovaries and were fully functional in every way. Now, in 2015 the emphasis has been on ramping up production of all-female larvae.
Sablefish can be completely reared inside a land-based facility, but most often the “growout” phase is done using net pens in open water. Luckenbach explains, “Different companies use different approaches. We’ve been told by industry that growout for mixed sex aquaculture of sablefish is typically 24-30 months.”
“…Our experience rearing sablefish in land-based tanks has resulted in roughly 25% of the mixed sex crop being sold at a loss to get rid of runts, and those are primarily males,” explained Jim Parsons of Troutlodge Marine.
With monosex stocks it’s hoped to significantly reduce the growout period and increase production efficiency.
At the Manchester facility NOAA is using behavioral approaches to optimize aquaculture and identify the best environmental, feeding and weaning conditions for rearing larval sablefish. This includes studying the effects of light intensity on feeding, growth and survival, and the use of odorant attractants to optimize weaning to dry diets using video analysis of feeding behavior. All of this is part of a larger NOAA effort to develop this sector of the aquaculture industry.
Among the benefits of sablefish monosex aquaculture is that the “product” should reach market size earlier as females grow faster than males (time=money) and have more uniformity in size. The exact numbers of production value increase are still to be determined for monosex sablefish, but the more uniform size should translate to a higher percentage of fish being sold at market value. The obvious benefits have induced producers in Canada, Mexico and even Korea to become interested in obtaining monosex stock for production.
This new generation of sablefish stands apart from other GMO, transgenic, and growth hormone treated agricultural products… during a time when the consumer is demanding wild, sustainable, non-GMO food sources and products in their diet.
Sablefish also contain a high amount of important fats compared to other fish – it contains about as much omega 3 fatty acids as salmon – and can reach market value for aquaculture production in just two years (at about 5-6 lbs).
To mitigate risks of cross-breeding with wild populations, researchers are continuing to work on producing reproductively sterile sablefish. This would likely improve production and profits to fish farmers as well.
Most importantly, Adam would like to get his current product into the hands of the aquaculture industry: “We are currently partnering with Troutlodge to establish commercial-scale monosex sablefish production.” Troutlodge Marine is only the third company in the world to commercialize this valuable species.
— Heather Wiedenhoft
Heather Wiedenhoft is a research scientist at Washington State University Department of Neuroscience in Vancouver Washington.