Keywords: Fish
CRISPR-Cas9 suppression gene drives for Nile tilapia control: prospects in sub-Saharan African freshwater ecosystems
35509Bobo, E. D., All Life, 19. 2026-03-16 15:14:01.
CRISPR-based suppression gene drives represent a promising tool for managing invasive Nile tilapia (Oreochromis niloticus) populations in sub-Saharan Africa’s freshwater ecosystems. Introduced through aquaculture, Nile tilapia supports livelihoods but also causes severe biodiversity loss. This review explores the technical feasibility of CRISPR-Cas9 suppression gene drives, specifically homing and Driving-Y drive systems, as species-specific, potentially self-sustaining biocontrol strategies. The theoretical effectiveness of these gene drive systems in reducing invasive Nile tilapia and restoring ecological balance is discussed within a precautionary framework. This study addresses the urgent need to protect native tilapia species, which are listed as Critically Endangered, Endangered, and Vulnerable by the IUCN. Gene drives have the potential to reduce invasive populations and restore ecological balance. However, their effectiveness can be compromised by extensive hybridization with native Oreochromis species and resistance evolution in genetically diverse populations. Therefore, the ecological, ethical, and socioeconomic risks of gene drive systems were examined in the context of the Convention on Biological Diversity and Cartagena Protocol. Hence, integrating molecular innovations with strong policy frameworks, stakeholder engagement, and comprehensive risk assessment is essential. CRISPR-Cas9 suppression drives deployment requires careful evaluation across ecological, ethical, and governance contexts to safeguard native ichthyofauna.
Inhibiting invasive fish reproduction via germ cell xenotransplantation and hybrid lethality
35292Amano, Y., Baba, H., Kishi, D. et al., Scientific Reports, 15. 2025-11-09 17:56:43.
Invasive alien fish constitute a major problem in the conservation of aquatic ecosystems. The most common method of exterminating invasive fish is physical capture by fishing gear; however, it is extremely difficult to eradicate them. Here, we developed a novel methodology to inhibit the reproduction of invasive fish by releasing surrogate males of the same species, which produce sperm of different species, into rivers, allowing them to produce lethal hybrids through natural spawning. This study focused on rainbow trout, an invasive fish that negatively impacts ecosystems worldwide. Since rainbow trout × brown trout hybrids are lethal, surrogate rainbow trout producing brown trout sperm were created by germline stem cell transplantation. Releasing the surrogate males into an experimental river inhabited by wild-type rainbow trout females revealed that they naturally mated and produced lethal hybrid offspring. This is a novel and powerful methodology for eradicating invasive fish.
Coproducing a Technology Readiness Level framework for non-persistent genetic biocontrol of aquatic invasive species
34984Julie Badger, Rex Alirigia, Isabel Ameli, et al, Journal of Environmental Management, 391. 2025-07-24 10:00:28.
Developing and implementing novel pest control technologies requires coordination and communication between technology developers, funding agencies, federal and state regulators, and early technology adopters. Efficient communication is particularly important for first-in-class technologies. Misunderstandings or lack of communication may hinder social engagement, jeopardize regulatory approval, decrease utility of the technology, deter public adoption, or compromise risk mitigation approaches. We, a team of diverse stakeholders in aquatic invasive species (AIS) control, here propose a shared language for discussing the development of non-persistent genetic biocontrol methods. Specifically, we adapted the existing Technology Readiness Level framework to apply to the development of non-persistent genetic biocontrol for invasive Cyprinus carpio (common carp) as a model case. The result of this effort is a tool for designing responsible technology development of a promising new class of pest management tools.
Assessing the suitability of YY males and ZZ females as an invasive species population control method across life histories
28170R. A. Erickson, H. M. Thompson, S. A. Kageyama, G. M. Andriacchi, A. R. Cupp, R. Patiño and J. J. Amberg, Biological Invasions, 25:3737-3751. 2023-08-12 12:16:15.
Natural resource managers use tools to control invasive species. In theory, stocking YY males or ZZ females would allow managers to skew sex ratios until populations collapse. In combination with other suppression methods, such as removal, this approach could be incorporated into Integrated Pest Management plans. For example, fishery managers have stocked YY males to control isolated non-native brook trout (Salvelinus fontinalis) populations. However, life histories and demographic factors (e.g., lifespans) vary across species and could affect the feasibility of skewing sex ratios as an effective control strategy for a given population. Likewise, some species may have sex determinations that do not allow population control through sex-skewing methods. We compared five representative aquatic invasive species with global invasion ranges for potential control by skewing the sex ratio through closed population simulations: red swamp crayfish (Procambarus clarkii), zebra mussels (Dreissena polymorpha), lake trout (Salvelinus namaycush), silver carp (Hypophthalmichthys molitrix), and Nile tilapia (Oreochromis niloticus). We determined that Nile tilapia, red swamp crayfish, and zebra mussels would be the most suitable to control through skewing the sex ratio assuming appropriate sex determination exists in the species. Lake trout could be eliminated by stocking YY males but would require either long stocking periods or high stocking numbers because of the long lifespan of the species. Silver carp populations were more difficult to crash because they live longer and produce many recruits. Broadly, these patterns demonstrated that short lived species lend themselves to control by skewing the sex ratio.
B Chromosomes in Psalidodon scabripinnis (Characiformes, Characidae) Species Complex
23552D. Silva, J. P. Castro, C. A. G. Goes, R. Utsunomia, M. R. Vidal, C. N. Nascimento, L. F. Lasmar, F. G. Paim, L. B. Soares, C. Oliveira, F. Porto-Foresti, R. F. Artoni and F. Foresti, Animals (Basel), 12. 2022-08-25 06:15:39.
B chromosomes are extra-genomic components of cells found in individuals and in populations of some eukaryotic organisms. They have been described since the first observations of chromosomes, but several aspects of their biology remain enigmatic. Despite being present in hundreds of fungi, plants, and animal species, only a small number of B chromosomes have been investigated through high-throughput analyses, revealing the remarkable mechanisms employed by these elements to ensure their maintenance. Populations of the Psalidodon scabripinnis species complex exhibit great B chromosome diversity, making them a useful material for various analyses. In recent years, important aspects of their biology have been revealed. Here, we review these studies presenting a comprehensive view of the B chromosomes in the P. scabripinnis complex and a new hypothesis regarding the role of the B chromosome in the speciation process.
Meiotic behavior, transmission and active genes of B chromosomes in the cichlid Astatotilapia latifasciata: new clues about nature, evolution and maintenance of accessory elements
22951A. L. Cardoso, N. B. Venturelli, I. da Cruz, F. M. de Sá Patroni, D. de Moraes, R. A. de Oliveira, R. Benavente and C. Martins, Molecular Genetics and Genomics, 2022-06-15 06:37:12.
Supernumerary B chromosomes (Bs) are dispensable genetic elements widespread in eukaryotes and are poorly understood mainly in relation to mechanisms of maintenance and transmission. The cichlid Astatotilapia latifasciata can harbor Bs in a range of 0 (named B -) and 1-2 (named B +). The B in A. latifasciata is rich in several classes of repetitive DNA sequences, contains protein coding genes, and affects hosts in diverse ways, including sex-biased effects. To advance in the knowledge about the mechanisms of maintenance and transmission of B chromosomes in A. latifasciata, here, we studied the meiotic behavior in males and transmission rates of A. latifasciata B chromosome. We also analyzed structurally and functionally the predicted B chromosome copies of the cell cycle genes separin-like, tubb1-like and kif11-like. We identified in the meiotic structure relative to the B chromosome the presence of proteins associated with Synaptonemal Complex organization (SMC3, SYCP1 and SYCP3) and found that the B performs self-pairing. These data suggest that isochromosome formation was a step during B chromosome evolution and this element is in a stage of diversification of the two arms keeping the self-pairing behavior to protect the A chromosome complement of negative effects of recombination. Moreover, we observed no occurrence of B-drive and confirmed the presence of cell cycle genes copies in the B chromosome and their transcription in encephalon, muscle and gonads, which can indicates beneficial effects to hosts and contribute to B maintenance.
Aquatic invasive species specialists’ perceptions on the importance of genetic tools and concepts to inform management
22482T. A. Bernos, K. M. Jeffries and N. E. Mandrak, Biological Invasions, 24:1863-1879. 2022-05-14 07:09:36.
Perceptions related to the importance of genetic research influence the mobilization of genetic tools and concepts to inform conservation actions. Research characteristics, stakeholders’ perspectives, knowledge, and social linkages with geneticists influence the outcome of genetic information for management practices. We surveyed a broad range of aquatic invasive species (AIS) specialists whose opinions, perspectives, and decisions influence AIS decision-making. We assessed perceptions related to the importance of genetic tools and concepts, as well as the appropriateness of genetic biocontrol, and tested whether their expertise, background, and experience influenced perceptions in a predictable way. While perceptions towards genetic tools and concepts were generally heterogeneous, there was a high consensus (84%) related to the importance of eDNA. Most predictors were weakly correlated with importance ratings. Specialists’ genetic knowledge was the strongest predictor of higher importance ratings: the odds of AIS specialists giving higher ratings increased by up to 1.5-fold with increasing genetic knowledge. When evaluating the appropriateness of genetic biocontrol, level of support was lower for approaches based on gene editing (58%) than those relying on traditional hatchery techniques (70%). Support for gene editing varied by geographic location and with specialists’ knowledge of genetics and AIS management. These findings suggest that perceptions towards genetic research vary between genetic tools and concepts and are shaped by the interplay of individual’s values, expertise, experience, and background. To collaborate more effectively, genetic scientists must understand the extent of genetic knowledge of their AIS management partners and recognize that their conceptions of the conservation genetics research-practice space may vary.
Trojan trout: could turning an invasive fish into a ‘super-male’ save a native species?
21823J. Miller, The Guardian, 2022-04-21 06:11:45.
Brook trout may greatly outnumber the Rio Grande cutthroat here, but nearly every brookie the team captures is male. That’s because many are a lab-produced variety known as “Trojan” brook trout. They are unique in that they carry not one, but two copies of the Y chromosome that codes maleness; they have no X chromosome to pass on. Since 2018, various streams across the Vermejo reserve have been stocked with this strain in an attempt to tilt the brook trout sex ratio so far male that eventually the population will stop breeding and die out on its own. Similar efforts are under way in a handful of creeks in Idaho, Washington and Oregon, and Nevada plans to embark on its own stocking programme this summer. Until now, the main tool to eliminate invasive fish species has been the potent chemical rotenone. The trouble is that “it also kills all the other fish, including the ones you are trying to conserve,” says Colleen Caldwell, a professor of fish and wildlife at New Mexico State University and a principal investigator overseeing the Leandro Creek project.
The prince, the mayor, and the U.S. fish that ate Japan
20103C. Elliot, National Geographic, 2022-01-11 16:44:32.
When Crown Prince Akihito visited Chicago on October 3, 1960, his sole request was to visit Shedd Aquarium. Then Mayor Richard J. Daley, an avid angler, presented the prince with a gift that he scooped with a net from one of the tanks himself: 18 bluegills, the official Illinois state fish. The 26-year-old future emperor was already a passionate ichthyologist, and he planned to stock the exotic fish in the moat surrounding his palace, according to accounts in the Chicago Tribune at the time. At windy Chicago O’Hare International Airport the next day with Princess Michiko, Akihito bid the city farewell, carrying a gift that he couldn’t have imagined would cause a decades-long ecological crisis in his homeland. In the intervening six decades, the bluegills became an invasive, species-destroying nightmare, crowding Japanese freshwater lakes and rivers and destroying native fish biodiversity, says Kenji Saitoh, a researcher at the country’s Fisheries Resources and Education Agency. Fortunately, science has marched on in 60 years. Now, Japanese geneticists are experimenting with the gene editing wizardry of CRISPR to sterilize the invasive bluegills. If the initiative succeeds, wildlife managers could use the same technique to rid the U.S. of damaging aquatic invasives such as the Asian carp.
Applying functional genomics to the study of lamprey development and sea lamprey population control
19946J. R. York, R. E. Thresher and D. W. McCauley, Journal of Great Lakes Research, 47:S639-S649. 2021-12-01 09:30:24.
Lampreys are one of the few survivors of an ancient lineage of jawless vertebrates and have become an important study organism in numerous disciplines in the biological sciences, including evolutionary biology, embryology, ecology, physiology and biomedicine. At the same time, however, lampreys have created economic and ecological problems due, primarily, to the invasion of parasitic sea lamprey (Petromyzon marinus) into the North American Great Lakes and consequent negative impacts on local fish populations. Barriers, trapping and lampricide treatments have reduced these impacts, but concern for habitat restoration, non-target effects and possible evolution of resistance to lampricides suggests the need to develop additional strategies that supplement current control measures. The advent of functional genomics, and in particular CRISPR/Cas9 genome editing, offers a molecular approach to this on-going problem. Here, we review the successful application of functional genetic, transcriptomic, and CRISPR/Cas9 genome editing technologies in lampreys to address basic research questions in the fields of evolutionary and developmental biology. We then describe how these tools may be repurposed for use by fishery and conservation biologists to approach the problem of invasive sea lamprey from a molecular-genetic perspective.
Genetic control of invasive sea lamprey in the Great Lakes
19270D. Ferreira-Martins, J. Champer, D. W. McCauley, Z. Zhang and M. F. Docker, Journal of Great Lakes Research, 2021-11-08 16:16:20.
The invasive sea lamprey was a significant factor in the collapse of fish stocks in the Great Lakes, and it continues to threaten the multi-billion-dollar fishing industry. Thus, substantial resources are invested annually on sea lamprey control. Current control strategies have reduced sea lamprey populations by up to 90%, but they are expensive and have some limitations, e.g., lamprey-specific biocides applied to larval habitat impact native lampreys, and physical barriers that block adult lamprey access to spawning habitat impede migration of other fishes. Therefore, genetic control options which offer a theoretically powerful and effective pest control tool are being explored, although they have uncertain sociopolitical support, especially given the need to protect sea lamprey in their native range in Atlantic drainages. Here, we present an overview of genetic approaches with potential for application to sea lamprey control in the Great Lakes. We classify these approaches into two major categories: self-limiting (heritable sex ratio ratchet, Trojan gene, split gene drive) and self-sustaining (gene drive-based sex ratio distortion, homing suppression gene drive, toxin-antidote gene drives, and modification-type gene drives to aid suppression). We describe the technical aspects, challenges, and potential application of each method, focusing on gene drives, a fast-evolving research area that was only a distant option for sea lamprey control in previous reviews. We conclude that, given the risk of undesired spread of deleterious alleles from the Great Lakes, self-limiting genetic control options and confined gene drives will likely be preferred over unconfined gene drive options for sea lamprey control.
Meiotic self-pairing of the Psalidodon (Characiformes, Characidae) iso-B chromosome: A successful perpetuation mechanism
18905D. Silva, C. Araya-Jaime, M. Yamashita, M. R. Vidal, C. Oliveira, F. Porto-Foresti, R. F. Artoni and F. Foresti, Genetics and Molecular Biology, 44:e20210084. 2021-10-08 14:29:15.
B chromosomes are non-essential additional genomic elements present in several animal and plant species. In fishes, species of the genus Psalidodon (Characiformes, Characidae) harbor great karyotype diversity, and multiple populations carry different types of non-essential B chromosomes. This study analyzed how the dispensable supernumerary B chromosome of Psalidodon paranae behaves during meiosis to overcome checkpoints and express its own meiosis-specific genes. We visualized the synaptonemal complexes of P. paranae individuals with zero, one, or two B chromosomes using immunodetection with anti-medaka SYCP3 antibody and fluorescence in situ hybridization with a (CA)15 microsatellite probe. Our results showed that B chromosomes self-pair in cells containing only one B chromosome. In cells with two identical B chromosomes, these elements remain as separate synaptonemal complexes or close self-paired elements in the nucleus territory. Overall, we reveal that B chromosomes can escape meiotic silencing of unsynapsed chromatin through a self-pairing process, allowing expression of their own genes to facilitate regular meiosis resulting in fertile individuals. This behavior, also seen in other congeneric species, might be related to their maintenance throughout the evolutionary history of Psalidodon.
Genetically Engineered Fish: Potential Impacts on Aquaculture, Biodiversity, and the Environment
15290R. A. Dunham and B. Su, GMOs: Implications for Biodiversity Conservation and Ecological Processes, 2020-12-02 17:03:48.
Studies on transgenic fish for the aquaculture industry have focused on improving growth rates, enhancing disease resistance, altering body composition, acting as biological factories for medical proteins, and even altering temperature tolerance and coloration. The future impact of transgenesis will likely be quite large. Growth hormone-transgenic salmon has been approved for human consumption and has been introduced to the market in Canada and soon to the USA. This is the first human consumption of approved transgenic meat. Transgene insertion has many pleiotropic effects. Several studies have projected the fitness of transgenic fish to be low, in general, compared to non-transgenic and wild fish; thus, their environmental risk is likely low and they would have minimal, if any, long-term impact on ecosystems or biodiversity. However, there have been no actual escapements; thus, only projections of risk are available based on small-scale experiments and the characteristics of transgenic fish compared to controls. An active area of research is repressible transgenic sterilization and sterilization using gene editing, both of which would allow application of transgenic fish with only short-term consequences for ecosystems in the worst-case scenario. Transgenic technology could also be potentially used to reduce or eliminate populations of nuisance species.
Report of the ad hoc technical expert group on risk assessment
16095Ad Hoc Technical Expert Group on Risk Assessment, Convention on Biological Diversity, 2020-04-15 15:54:41.
The Conference of the Parties serving as the meeting of the Parties to the Cartagena Protocol further decided to extend the Online Forum on Risk Assessment and Risk Management to assist the AHTEG and invited submissions of information relevant to the work of the online forum and the AHTEG from Parties, other Governments, and indigenous peoples and local communities. The AHTEG is to submit the outcomes of its work for consideration by the Subsidiary Body on Scientific, Technical and Technological Advice at its twenty-fourth meeting, prior to the tenth meeting of the Parties to the Protocol.
Development of control and sterilization technology for bluegill by genome editing
20100M. A. Madsen, Nippon Suisan Gakkaishi, 86:100-100. 2020-03-31 09:55:36.
This article is in Japanese
Simulating effects of fitness and dispersal on the use of Trojan sex chromosomes for the management of invasive species
11488C. C. Day, E. L. Landguth, R. K. Simmons, W. P. Baker, A. R. Whiteley, P. M. Lukacs and A. Bearlin, Journal of Applied Ecology, 2020-03-19 20:15:27.
The use of Trojan Y chromosomes (TYC) for controlling invasive species involves manipulating the sex chromosomes of captive-raised individuals. Following release, the offspring of these individuals consist of only one sex, thereby skewing the sex ratio of the invasive population and potentially leading to eradication. Simulation models are needed that can inform managers about how to maximize the likelihood of invasive species eradication, since implementation of this novel management approach in the field is still rare. Here, we present the first spatially explicit, mechanistic simulation model of a real-world TYC program for invasive species eradication. Using a brook trout Salvelinus fontinalis system model, we investigated the effects of competitive and reproductive fitness of the captive-raised YY males, dispersal behaviour upon their release and landscape heterogeneity on eradication success. Likelihood of eradication was dependent on both the competitive and reproductive fitness of the Trojan individuals. Competitive fitness (i.e. survival) had a higher threshold for eradication, below which the invasive populations were not eradicated. Movement ecology of both the wild and YY male populations was important for eradication. Under a restricted dispersal scenario for YY males following their release, the wild population was not extirpated but maintained a stable, yet reduced, population size. Analysis of landscape configuration indicated that time to eradication of local patches increased with greater connectivity within the stream network. In addition to sex ratio distortion, density-dependent mortality resulting from outplantings made an important contribution to population decline and therefore may also affect native competitors. Synthesis and applications. The use of Trojan sex chromosomes to skew population sex ratios is a novel method for the suppression and eradication of aquatic invasive species. Results from our modelling work indicate that while eradication is possible, maximizing its likelihood requires an understanding of the fitness and movement ecology of both the wild and YY male populations of the invasive species. Both our model and the principles derived from this study related to fitness and behavioural landscape ecology can be broadly applied to other invaded species and systems.
Optimal control and analysis of a modified trojan Y-Chromosome strategy
11491M. A. Beauregard, R. D. Parshad, S. Boon, H. Conaway, T. Griffin and J. J. Lyu, Ecological Modelling, 416. 2020-01-15 20:19:52.
The Trojan Y Chromosome (TYC) strategy is a promising eradication method that attempts to manipulate the female to male ratio to promote the reduction of the population of an invasive species. The manipulation stems from an introduction of sex-reversed males, called supermales, into an ecosystem. The offspring of the supermales is guaranteed to be male. Mathematical models have shown that the population can be driven to extinction with a continuous supply of supermales. In this paper, a new model of the TYC strategy is introduced and analyzed that includes two important modeling characteristics, that are neglected in all previous models. First, the new model includes intraspecies competition for mates. Second, a strong Allee effect is included. Several conclusions about the strategy via optimal control are established. These results have large scale implications for the biological control of invasive species.
Genetic control of Invasive carp
13941MAISRC, Minnesota Aquatic Invasive Species Research Center, 2019-10-16 15:08:53.
This project focuses on a novel method of biocontrol for common carp which will complement existing technologies by introducing a synthetic species-like barrier to reproduction. Researchers will use programmable transcription activators to drive lethal embryonic overexpression of endogenous genes in hybrid embryos.
Biocontrol in Australia: Can a carp herpesvirus (CyHV-3) deliver safe and effective ecological restoration?
3924Kopf, RKB, M.; Finlayson, C. M.; Hodges, K.; Humphries, P.; King, A.; Kingsford, R. T.; Marshall, J.; McGinness, H. M.; Thresher, R.; Vanderplasschen, A., Biological Invasions, 21:1857-1870. 2019-01-02 00:00:00.
The Australian Government is considering Cyprinid herpesvirus 3 (CyHV-3) for biocontrol of invasive common carp (Cyprinus carpio L.). We review the evidence-base for its potential ecological risks, benefits and effectiveness. Lower carp abundance may boost native fish biomass and improve water clarity, but there is little evidence available to suggest that the virus, alone or used in combination with other methods, can deliver effective or safe biocontrol. Further, the virus may already be present in Australia. Overseas, the virus has caused sporadic and localized mortalities of carp in lakes and rivers, but has generally had no long-term measurable effect on wild carp or native fish populations. The temperature range of disease (18-28 degrees C), unknown co-factors causing outbreaks, and predictable re-colonization and recruitment boom of immune and virus-resistant carp, following a biocontrol release, remain formidable and unmitigated barriers to success. CyHV-3 infection trials on Australian biota have unexplained high mortality rates of recreationally-important and threatened fishes, and the role of asymptomatic carriers remains uncertain. Finally, Australia has national and international obligations to ensure that there are no perverse outcomes from biocontrol actions. Despite political pressure, there is no environmental justification to rush the release of this virus. To achieve the Government goals of restoring native biodiversity we advocate that key uncertainties, risks and efficacy barriers first need to be addressed. It is only then that viral biocontrol could be considered a viable tool to complement broader ecological restoration strategies for Australia's waterways.
Population Consequences of Releasing Sex-Reversed Fish: Applications and Concerns
11500C. Wederkind, Sex Control in Aquaculture, Chp 8:179-188. 2018-11-02 20:38:44.
Sex differentiation is generally more labile in gonochoristic fish than it is, for example, in birds and mammals. Environmentally induced sex reversal is, therefore, often possible, and creates genotype‐phenotype mismatches that can be useful in population management. Interestingly, sex chromosomes of fish are typically not significantly decayed (i.e., all types of offspring of sex‐reversed individuals may be viable, including YY and WW individuals that can then often be sex reversed again). Releasing sex‐reversed fish, or releasing untreated YY and WW offspring of sex‐reversed fish, into natural populations can, therefore, affect the sex ratio of the population in the following generations and, hence, affect population growth.
A spatially discrete, integral projection model and its application to invasive carp
11503R. A. Erickson, E. A. Eager, P. M. Kocovsky, D. C. Glover, J. L. Kallis and K. R. Long, Ecological Modelling, 387:163-171. 2018-09-21 20:46:26.
Natural resource managers and ecologists often desire an understanding of spatial dynamics such as migration, dispersion, and meta-population dynamics. Network-node models can capture these salient features. Additionally, the state-variable used with many species may be appropriately modeled as a continuous variable (e.g., length) and management activities sometimes can only target individuals of certain sizes. Integral projection models (IPMs) can capture this life history characteristic and allow for the examination of size-specific management. We combined an IPM with a network-node model to capture both of these salient features. We then demonstrated how this model could be used to understand and manage populations of invasive species focusing on grass carp as an example. Grass carp disrupt ecosystems outside of their native range and have spread around much of the world, including North America. The impacts of grass carp include adversely changing aquatic plant communities, which in turn affect a wide range of endpoints ranging from water quality to waterfowl recruitment. We specifically examined two theoretical systems using parameters from the literature. First, we modeled a lake with two tributaries and examined how modified sterile males could be used as a control tool. We found that modified sterile males may be a feasible control tool to limit population growth. Second, we modeled a series of river pools and examined how harvest and deterrents could be used to decrease the risk of expanding grass carp's range within a river system. Within this system, we also compared the impacts of size specific harvest and uniform harvest across all sizes. We found that targeting the largest, spawning populations may be more important than targeting the populations close to the invasion front for reducing the risk of spreading grass carp. We also demonstrate that size of harvested fish was important for controlling populations.
Sex determination in Neotropical fish: Implications ranging from aquaculture technology to ecological assessment
11495J. I. Fernandino and R. S. Hattori, General and Comparative Endocrinology, 273:172-183. 2018-07-07 20:24:06.
The high biodiversity of fish in the Neotropical region contrasts with scarce or biased studies on the mechanisms involved in the sex determination in members of this fauna. In this review, we attempted to compile the information available on determination, differentiation, and manipulation of sex for Neotropical species, with special focus on silversides and other two speciose groups, known as characins (Characiformes) and catfishes (Siluriformes). Currently, there is plenty of information available on chromosomal sex determination systems, which includes both male and female heterogamety with many variations, and sex chromosomes evolution at the macro chromosomal level. However, there is hitherto a blank in information at micro, gene/molecule levels and in research related to the effects of environmental cues on sex determination; most of reported studies are limited to silversides and guppies. In view of such a high diversity, it is critically necessary to establish key model species for relevant Neotropical fish taxa and also multi-disciplinary research groups in order to uncover the main patterns and trends that dictate the mechanisms of sex determination and gonadal differentiation in this icthyofauna. By increasing our knowledge on sex determination/differentiation with the identification of sex chromosome-linked markers or sex-determining genes, characterization of the onset timing of morphological gonadal differentiation, and determination of the environmental-hormonal labile period of gonadal sex determination in reference species, it will be possible to use those information as guidelines for application in other related groups. Overall, the strategic advance in this research field will be crucial for the development of biotechnological tools for aquaculture industry and for conservation of fish fauna from the Neotropical Region.
Evaluating active genetic options for the control of Sea Lampreys (Petromyzon marinus) in the Laurentian Great Lakes
4020Thresher, REJ, Michael; Drake, D. Andrew, Canadian Journal of Fisheries and Aquatic Sciences, 76:1186-1202. 2018-01-18 00:00:00.
For more than two decades the Great Lakes Fishery Commission has sought tactics to complement, and potentially replace, the use of barriers and lampricides to control Sea Lamprey in the Great Lakes, but thus far without success. This paper examines the potential of modern genetic technology to suppress these invasive populations. We identified six recombinant options that appeared to be moderately to highly feasible, most of which were judged by an expert panel as extremely low or low risk, and for which R&D was broadly supported by stakeholders. The two options judged to overall best combine high efficacy and low risks were a Mendelian “sex ratio drive” and genetically modifying a prey species as to kill or sterilize Sea Lamprey that fed on it. Core issues regarding use of genetic biocontrol in the Great Lakes include technical problems associated with maintaining a Sea Lamprey brood line, information gaps for most options, the extent of broader public support, and the extent and nature of national and international consultation required in making decisions about control options.
Production of YY Supermale and XY Physiological Female Common Carp for Potential Eradication of this Invasive Species
11508M. Y. Jiang, X. X. Wu, K. X. Chen, H. R. Luo, W. Yu, S. T. Jia, Y. M. Li, Y. F. Wang, P. H. Yang, Z. Y. Zhu and W. Hu, Journal of the World Aquaculture Society, 49:315-327. 2018-01-03 15:22:53.
The common carp, Cyprinus carpio, is the third most cultivated freshwater species worldwide, but is also considered an invasive species. The Trojan Y chromosome strategy is one of the most promising methods to eradicate this invasive species. However, obtaining fertile YY supermale (MYY) and YY physiological female (FYY) common carp was thought to be very difficult. The present study focused on the production of androgenetic MYY and XY physiological female (FXY) common carp. We first optimized the conditions for artificially induced androgenesis. The results indicated that the optimum ultraviolet (UV) exposure time was 4min at an irradiation distance of 26cm and the optimum initiation time with heat shock (40 +/- 0.5C for 2min) was 30min after fertilization. Then, we produced androgenetic MYY Yellow River carp with only paternal inheritance, which were viable and identified by paternity testing and test crossing. Finally, we successfully produced FXY Yellow River carp by feeding 60-d-old MXY with commercially available feed mixed with 17-estradiol (200mg/kg) and Flutamide (200mg/kg) for 3mo. In conclusion, by combining artificially induced androgenesis with an artificially induced sex reversal technique, we could cost-effectively produce MYY and FXY common carp.
The optimal implementation of the Trojan Y chromosome eradication strategy of invasive species
11510M. R. Kelly and X. Y. Wang, Journal of Biological Systems, 25:399-418. 2017-08-02 15:25:17.
Invasive aquatic species continue to be a persistent problem around the world. The Trojan Y Chromosome (TYC) eradication strategy has recently been developed to help fight the problem in aquatic systems by targeting only the invasive species, sparing native marine stock. It involves rearing genetically modified samples of the invasive species and introducing them into the environment to alter the sex ratio of the invasive population. The paper is devoted to finding the optimal implementation of the TYC eradication strategy of an invasive species as well as a modified, potentially more cost-effective strategy. The modified TYC strategy (MTYC) eliminates one round of exposure to sex hormones compared to the TYC strategy. After introducing both strategies, the optimal control problems for each are formulated. The two strategies are compared through numerical simulations. Our results illustrate that the MTYC strategy, with lower implementation costs, is a better strategy option when trying to minimize the overall effective cost in most scenarios.
Production of a YY Male Brook Trout Broodstock for Potential Eradication of Undesired Brook Trout Populations
11516D. J. Schill, J. A. Heindel, M. R. Campbell, K. A. Meyer and E. Mamer, North American Journal of Aquaculture, 78:72-83. 2015-12-31 15:35:45.
Brook Trout Salvelinus fontinalis introduced outside of their native range often negatively impact native aquatic fauna or provide marginal fisheries and are frequently targeted for manual or piscicide removal in lakes and streams. Unfortunately, complete eradication of exotic Brook Trout populations via these methods is rarely achieved; new approaches are needed. A potential alternative is a Trojan Y Chromosome (TYC) program in which hatchery-produced genetically YY male fish would be regularly released into an undesired population over time, skewing the population towards 100% males, theoretically resulting in wild population extirpation. We developed two genetic sex markers for Brook Trout and employed juvenile sex reversal methods commonly used in commercial aquaculture to develop a YY broodstock that can produce offspring for possible future use as biological control agents. Our search for genetic sex markers proved successful, with genotypic sex determination for two assays matching the observed phenotype for 90 out of 90 individuals. In the first phase of the program, estradiol-infused feed readily feminized genetic XY males into neofemales (FXY fish) at a high rate (99.6%; n = 224). Survival of progeny from such egg-laying FXY fish averaged 88% to eye-up and 91% from eye-up to ponding, values similar to untreated Brook Trout reared at the same facility. In the second program phase, we cultured both sperm-and egg-producing supermales (YY fish), a vital step towards development of TYC technology on a large aquaculture scale. Results showed that, in the hatchery, estradiol treatment does not reduce Brook Trout growth. This study demonstrates that hatchery production of a YY Brook Trout broodstock is feasible, modest in cost (less than US$10,000), and can be completed in 4 years. Although several hurdles remain before a full-scale stocking program could occur, we believe that future work on the TYC strategy for Brook Trout is warranted.
Stochastic models for the Trojan Y-Chromosome eradication strategy of an invasive species
11514X. Y. Wang, J. R. Walton and R. D. Parshad, Journal of Biological Dynamics, 10:179-199. 2015-12-16 15:32:37.
The Trojan Y-Chromosome (TYC) strategy, an autocidal genetic bio-control method, has been proposed to eliminate invasive alien species. In this work, we develop a Markov jump process model for this strategy, and we verify that there is a positive probability for wild-type females going extinct within a finite time. Moreover, when sex-reversed Trojan females are introduced at a constant population size, we formulate a stochastic differential equation (SDE) model as an approximation to the proposed Markov jump process model. Using the SDE model, we investigate the probability distribution and expectation of the extinction time of wild-type females by solving Kolmogorov equations associated with these statistics. The results indicate how the probability distribution and expectation of the extinction time are shaped by the initial conditions and the model parameters.
Ecological and evolutionary applications for environmental sex reversal of fish
11518A. McNair, P. M. Lokman, G. P. Closs and S. Nakagawa, Quarterly Review of Biology, 90:23-44. 2015-03-01 15:38:29.
Environmental sex reversal (ESR), which results in a mismatch between genotypic and phenotypic sex, is well documented in numerous fish species and may be induced by chemical exposure. Historically, research involving piscine ESR has been carried out with a view to improving profitability in aquaculture or to elucidate the processes governing sex determination and sexual differentiation. However, recent studies in evolution and ecology suggest research on ESR now has much wider applications and ramifications. We begin with an overview of ESR in fish and a brief review of the traditional applications thereof We then discuss ESR and its potential demographic consequences in wild populations. Theory even suggests sex-reversed fish may be purposefully released to manipulate population dynamics. We suggest new research directions that may prove fruitful in understanding how ESR at the individual level translates to population-level processes. In the latter portion of the review we focus on evolutionary applications of ESR Sex-reversal studies from the aquaculture literature provide insight in to the evolvability of determinants of sexual phenotype. Additionally, induced sex reversal can provide information about the evolution of sex chromosomes and sex-linked traits. Recently, naturally occurring ESR has been implicated as a mechanism contributing to the evolution of sex chromosomes.
Sperm traits of masculinized fish relative to wild-type males: a systematic review and meta-analyses
11512A. M. Senior, S. L. Johnson and S. Nakagawa, Fish and Fisheries, 17:143-164. 2014-09-11 15:29:18.
Environmental sex reversal (ESR), whereby environmental effects (e.g. exogenous chemicals) override genetic sex determination, is a commonly used technique in aquaculture and physiology research. We performed a systematic review and meta-analyses of the literature that compares the sperm characteristics of masculinized genotypic females to wild-type males. We detected no mean differences between the ejaculate volume, sperm motility, duration or linearity of each type of male. We found some large mean differences in sperm concentration (d=2.541, CI=-0.004 to 5.086), reproductive success (d=-1.400, CI=-2.943 to 0.142), semen osmolality (d=1.850, CI=0.622 to 3.077) and sperm velocity (d=-0.933, CI=-1.426 to -0.441); in the case of the latter two traits, the mean effect was statistically significant. However, any significance did not stand up to a more conservative analysis. Additionally, heterogeneity was high and we found that where large differences between the sperm of sex-reversed and wild-type males are reported, these effects are attributable to sperm sampling methodology. Overall, we found little evidence for large systematic differences between the sperm produced by masculinized and wild-type male fish. Thus, masculinized genotypic females may enjoy reproductive success comparable to genotypic males. This conclusion leads to two potential implications: (i) sex-reversed fish may influence the dynamics of wild populations and (ii) aquaculture practices may use ESR to produce males with sperm quality similar to that of genotypic males. Most studies appear to have been performed in aquaculture species (i.e. Salmonidae); thus future experiments in non-model organisms may provide important insights in to the uniformity of the effects described.
Genetic control of invasive fish: technological options and its role in integrated pest management
4158Thresher, REH, K.; Bax, N. J.; Teem, J.; Benfey, T. J.; Gould, F., Biological Invasions, 16:1201-1216. 2014-01-16 00:00:00.
Genetic options for the control of invasive fishes were recently reviewed and synthesized at a 2010 international symposium, held in Minneapolis/St. Paul, MN, USA. The only option currently available "off-the-shelf'' is triploidy, which can be used to produce sterile males for a release program analogous to those widely and successfully used for biological control of insect pests. However, the Trojan Y and several recombinant options that heritably distort pest population sex ratios are technologically feasible, are at or are close to proof-of-concept stage and are potentially much more effective than sterile male release programs. All genetic options at this stage require prolonged stocking programs to be effective, though gene drive systems are a potential for recombinant approaches. They are also likely to differ in their current degree of social acceptability, with chromosomal approaches (triploidy and Trojan Y) likely to be the most readily acceptable to the public and least likely to require changes in legislative or policy settings to be implemented. Modelling also suggests that the efficacy of any of these genetic techniques is enhanced by, and in turn non-additively enhance, conventional methods of pest fish control.
Evidence for meiotic drive as an explanation for karyotype changes in fishes
4148Molina, WFM, P. A.; Bertollo, L. A. C.; Bidau, C. J., Marine Genomics, 15:29-34. 2014-01-06 00:00:00.
The process of preferential chromosome segregation during meiosis has been suggested to be responsible for the predominance of certain chromosome types in the karyotypes of mammals, birds and insects. We developed an extensive analysis of the fixation of mono- or bibrachial chromosomes in the karyotypes of the large Actinopterygii fish group, a key link in the evolution of terrestrial vertebrates, in order to investigate the generality of meiotic drive in determining karyotypic macrotrends. Unlike mammals, fishes have markedly undergone several types of preferential chromosomal rearrangements throughout evolution. Data from the analyzed orders indicate a prevalence of karyotypes with few (<33%) or many (>66%) acrocentric chromosomes and a low number of karyotypes with balanced numbers of mono- and bi-brachial elements. Parallel trends towards a higher number of karyotypes with prevalence of monobrachial chromosomes occurred in phylogenetically close orders (e.g. Perciformes and Tetraodontiformes, and in the order Mugiliformes) and in clades with prevalence of bibrachial elements (e.g. Characiformes, Gymnotiformes, Siluriformes, and Cypriniformes). Some orders where fewer species were available for study, such as Atheriniformes and Anguilliformes, showed karyotype assemblages where both trends were present. Our results strongly suggest a primary role of meiotic drive in karyotypic evolution as indicated by the accumulation of monobrachial chromosomes in Perciformes and Cypriniformes, or bibrachial chromosomes in Siluriformes and Characiformes. Further examinations of the interaction between life history traits, environmental characteristics, and the fixation of chromosomal rearrangements would be exceedingly valuable.
Preferential accumulation of sex and Bs chromosomes in biarmed karyotypes by meiotic drive and rates of chromosomal changes in fishes
4147Molina, WFM, P. A.; Bertollo, L. A. C.; Bidau, C. J., Anais Da Academia Brasileira De Ciencias, 86:1801-1812. 2014-01-05 00:00:00.
Mechanisms of accumulation based on typical centromeric drive or of chromosomes carrying pericentric inversions are adjusted to the general karyotype differentiation in the principal Actinopterygii orders. Here, we show that meiotic drive in fish is also supported by preferential establishment of sex chromosome systems and B chromosomes in orders with predominantly bi-brachial chromosomes. The mosaic of trends acting at an infra-familiar level in fish could be explained as the interaction of the directional process of meiotic drive as background, modulated on a smaller scale by adaptive factors or specific karyotypic properties of each group, as proposed for the orthoselection model.
Analysis of the Trojan Y-Chromosome eradication strategy for an invasive species
11524X. Y. Wang, J. R. Walton, R. D. Parshad, K. Storey and M. Boggess, Journal of Mathematical Biology, 68:1731-1756. 2013-05-24 15:52:53.
The Trojan Y-Chromosome (TYC) strategy, an autocidal genetic biocontrol method, has been proposed to eliminate invasive alien species. In this work, we analyze the dynamical system model of the TYC strategy, with the aim of studying the viability of the TYC eradication and control strategy of an invasive species. In particular, because the constant introduction of sex-reversed trojan females for all time is not possible in practice, there arises the question: What happens if this injection is stopped after some time? Can the invasive species recover? To answer that question, we perform a rigorous bifurcation analysis and study the basin of attraction of the recovery state and the extinction state in both the full model and a certain reduced model. In particular, we find a theoretical condition for the eradication strategy to work. Additionally, the consideration of an Allee effect and the possibility of a Turing instability are also studied in this work. Our results show that: (1) with the inclusion of an Allee effect, the number of the invasive females is not required to be very low when the introduction of the sex-reversed trojan females is stopped, and the remaining Trojan Y-Chromosome population is sufficient to induce extinction of the invasive females; (2) incorporating diffusive spatial spread does not produce a Turing instability, which would have suggested that the TYC eradication strategy might be only partially effective, leaving a patchy distribution of the invasive species.
Guidance on the environmental risk assessment of genetically modified animals
16055European Food Safety Authority, European Food Safety Authority, 2013-05-23 20:45:04.
This document describes the six sequential steps for the ERA of GM animals, as indicated in Directive 2001/18/EC: (1) problem formulation including hazard and exposure identification; (2) hazard characterisation; (3) exposure characterisation; (4) risk characterisation; (5) risk management strategies; and (6) an overall risk evaluation. The Scientific Panel on Genetically Modified Organisms of the European Food Safety Authority follows Annex II of Directive 2001/18/EC, considering specific areas of risk to be addressed by applicants and risk assessors during the ERA of GM fish, GM insects and GM mammals and birds.
Combining the Trojan Y chromosome and daughterless carp eradication strategies
11522J. L. Teem and J. B. Gutierrez, Biological Invasions, 16:1231-1240. 2013-05-17 15:50:22.
The Trojan Y chromosome (TYC) strategy and the daughterless carp (DC) strategy represent two autocidal genetic biocontrol methods for eliminating invasive fish by changing the sex ratio of the population. Each strategy is designed to reduce the number of females in a target population, ultimately leading to local extinction of the population. In the DC approach, the proportion of males in the population is increased as a result of introducing an autocidal fish containing a transgenic aromatase gene insertion into multiple autosome sites. In the TYC approach, matings of an autocidal fish containing two Y sex chromosomes results in an increased proportion of males in the population. A mathematical model based upon coupled ordinary differential equations was constructed to observe the effect of an autocidal fish with the combined genetic features of both strategies (TYCDC) on a target population. The model incorporated a fitness parameter associated with fish bearing aromatase inhibitor genes and for fish bearing two Y chromosomes. Under conditions where the fitness penalty of the autocidal fish was negligible, modeling results showed that a combined strategy produced a modest reduction in the time required for female eradication, and that fewer autocidal fish were required to achieve extinction. However, increasing the fitness penalty associated with the autocidal fish neutralized the benefits of the TYCDC strategy, and suggested that the effort and expense of a combined strategy may not be warranted if the fitness cost of the TYCDC autocidal fish is significant.
A comparison of the Trojan Y Chromosome and daughterless carp eradication strategies
11520J. L. Teem, J. B. Gutierrez and R. D. Parshad, 16, 16:1217-1230. 2013-05-08 15:46:59.
Two autocidal genetic biocontrol methods have been proposed as a means to eliminate invasive fish by changing the sex ratio of the population: the Trojan Y Chromosome (TYC) strategy and the Daughterless Carp (DC) strategy. Both strategies were modeled using ordinary differential equations that allow the kinetics of female decline to be assessed under identical modeling conditions. When compared directly in an ordinary differential equation (ODE) model, the TYC strategy was found to result in female extinction more rapidly than a DC strategy (in each of three models tested in which the Daughterless autocidal fish contained an aromatase inhibitor gene in either two or eight copies). The TYC strategy additionally required the introduction of fewer autocidal fish to the target population to achieve local extinction of females as compared to the DC approach. The results suggest that the relatively lower efficiency of female reduction associated with the DC approach is a consequence of a greater capacity to produce females and also a reduced capacity to produce males as compared to the TYC system.
Analysis of the Trojan Y chromosome model for eradication of invasive species in a dendritic riverine system
11532J. B. Gutierrez, M. K. Hurdal, R. D. Parshad and J. L. Teem, Journal of Mathematical Biology, 64:319-340. 2011-03-04 17:07:15.
The use of Trojan Y chromosomes has been proposed as a genetic strategy for the eradication of invasive species. The strategy is particularly relevant to invasive fish species that have XY sex determination system and are amenable to sex-reversal. In this paper we study the dynamics of an invasive fish population occupying a dendritic domain in which Trojan individuals bearing multiple Y chromosomes have been released as a means of eradication. We demonstrate the existence of a bounded absorbing set that represents extinction of the invasive species irrespective of the dendritic configuration. The method of analysis used to obtain global estimates could be applied to other population problems and other geometries.
On the global attractor of the Trojan Y chromosome model.
11536R. D. Parshad and J. B. Gutierrez, Communications on Pure and Applied Analysis, 10:339-359. 2010-01-01 17:11:02.
We consider the Trojan Y Chromosome (TYC) model for eradication of invasive species in population dynamics. We present global estimates for the TYC system in a spatial domain. In this work we prove the existence of a global attractor for the system. We derive uniform estimates to tackle the question of asymptotic compactness of the semi-group for the TYC model in H(2)(Omega). This along with the existence of a bounded absorbing set, which we also derive, demonstrates the existence of a global attractor for the TYC model. The present analysis reveals that extinction of an invasive species is always possible to achieve irrespective of geometric considerations of the domain. This result is valid for TYC systems in which advection is negligible. This theoretical work lays the foundation for experimental studies of the application of the TYC eradication strategy in spatial ecology, since the outcome is in principle guaranteed.
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