Research Question:
The main issues that the authors did not deal with are those surrounding real world applications. They mention that the findings may be used towards both conservation biology and commercial exploits, but leave it at that. Though I firmly believe that this research has great potential to aid in the restoration of wild fish populations, the reality is that expensive technological advances such as these will only be further pursued if there are significant commercial benefits. To this end, these breakthroughs have the potential to increase the viability and genetic variability of existing brood stocks of current aquaculture projects. More importantly though, is the potential to successfully breed fish that otherwise would be impossible, either physically or financially, to culture on a commercial scale. Take for instance tuna; there is a high demand for several species, but wild supply is unable to keep up with the demand and capture fisheries are crashing. At this time however, tuna are only pen-raised and not truly cultured because of difficulties with life cycles and financial accessibility. As with most marine fish, tuna have planktonic larvae. In addition to the difficulties associated with rearing such larvae, tuna do not nest on any kind of substrate and are far too large and active to be bred in tanks. This eliminates all possibilities of controlling the breeding environment and creates serious issues with collection of eggs or larvae. All of these combined problems would make it next to impossible to perform any type of selective breeding to create better genetic lines for broodstock establishment. In addition, there are many legal issues with rearing genetically altered fish in the open ocean, as experienced by Aquabounty; a company designing genetically engineered salmon broodstock. The solution: on shore breeding programs with a surrogate species.
Proposed approach:
As the experiments proved, primordial germ cells from one species can be transplanted, colonize, and develop inside of another species that is closely related. The research papers previously discussed involved trout and salmon; both members of the family Salmonidae, that are well known and studied in the aquaculture industry. I propose that the same procedure might also work between tuna and mackerel. Bonito, another member of the family Scombridae, is another possibility, but since mackerel are more often used as a commercially viable food source I will focus on their use instead. Tuna can reach hundreds of pounds in weight, and though this is much above market size, it provides a glimpse of the issue of rearing in tanks. The average mackerel however, may reach about 10-15 pounds when fully matured, a much more manageable size. To begin, the same basic procedures will be necessary (4). To ensure that the process will work between these species, it will be necessary to create a generation of tuna that have PGC’s marked by green florescent protein. Though extremely difficult and expensive, it would still be relatively cost effective because it would require relatively few tuna to produce enough offspring for initial broodstock. After successfully creating a generation expressing the GFP marked cells, some PGC’s could be transplanted into developing embryos of mackerel. It would require several trials to determine the most effective timing of transplantation. In trout that meant thirty-five to forty days post fertilization. It may very well be different in the Scombridae family, so these tests are crucial. After the most effective timing is recorded, a series of transplants from donor tuna PGC’s to appropriately developed mackerel larvae recipients would be performed. Once this generation of surrogate mackerel mature, they would be crossed with wild-type mackerel to determine what percentage of the offspring are donor-type. Though probably a small percentage, this would prove whether or not the hypothesis would work. Assuming that it did, the next step would be to increase the number of donor-type offspring. As recently proved, sterile triploid salmon that had transplants of viable rainbow trout PGC’s sometimes developed fully functioning gametes. Of the fish that developed functional gametes, 100% of the progeny produce were that of the donor-type (3). If this same principle worked in my hypothesis, then genetically altered mackerel could give birth to 100% tuna offspring. Of course there are many restrictions on rearing genetically engineered fish in offshore net pens. However, because mackerel are so much smaller, all of the complicated breeding and analysis could be performed onshore, in tightly controlled laboratory conditions where legality is not as much of an issue. The resulting broodstock is not genetically altered, but true tuna proved by DNA analysis techniques. It has also already been established that onshore facilities can be successful in rearing planktonic larvae as can be seen in pacific abalone farms. The veligers of abalone are smaller than fish fry, and are still successfully cultured. The ability to control the conditions so tightly is what enables the process to work effectively. Tuna fry could then be grown under these conditions, fed live and formulated food, and then like salmon smolts (lecture #), get transported into net-pens. From that point the grow-out process is no different than what is already in practice (2). With time and effort, genetic lines could be established to achieve better growth rates and disease resistance, as was performed with salmon and trout. These could then be used as donors of PGC’s to be hosted by the surrogate mackerel at onshore breeding facilities. The main issue with the practical application of this hypothesis is the high cost to perform the initial tests and procedures. Even after that, the cost of growing out such a predatory fish as tuna would be extremely inhibitive. Despite the extremely high costs though, I feel that profit would still be considerable. Tuna is one of the most sought after marine food fish. It demands a high market price, especially for the sushi grade meat that can be produce more easily with farmed fish. With this in mind I feel that it would be worthwhile to further pursue my hypothesis. If proven successful then not only would there be a huge commercial market, but the process could also be used to help restore some of the wild populations so devastated by over fishing. In theory this same process could be used with most other closely related species, and would have the most significant impacts on difficult to breed, valuable, marine species such as tuna.
I was actually wondering if you would stumble upon my thread...
