Yellow perch (Perca flavescens) are a popular game and food fish in the Great Lakes region. However, intensive culture of this species in the North Central Region is still in its infancy. In this species, females grow faster and to a larger size than males, making them more valuable in aquaculture. In fact, a population of 1,000 female yellow perch can gross approximately $555 more than the same number of fish exhibiting a 1:1 male:female ratio at the current fillet value of $14 per pound. Attempts have been made to produce monosex populations of yellow perch through sex reversal, but have resulted in the formation of nonfunctional, intersex fish due to the initiation of treatment after the beginning of gonadal differentiation. Yellow perch require more elaborate techniques to conduct sex reversal than many other species due to the beginning of sexual differentiation occurring before the transition to formulated feeds. This thesis consists of two sex reversal experiments carried out in 2015 and 2016. The 2015 studies evaluated the success of hormonal masculinization using the synthetic steroid hormone 17a- methyltestosterone (MT) by two treatment methods, diet enrichment and immersion, as well as two initiation times with respect to fish size, 12 mm and 14 mm total length. This study also evaluated the feminizing capacity of another steroid hormone, estradiol-17ß, in yellow perch exposed via immersion treatments beginning at the same two size classes. All fish were checked for spermiation by manual stripping in late January/early February of 2016. Although the groups that had been exposed to the masculinizing hormone beginning at 12 mm total length displayed significantly more spermiating males than those exposed beginning at 14 mm (P
Aquaculture is the fastest growing food production sector globally, with freshwater fish making up the majority of aquaculture production today. An important commercial species throughout the Great Lakes with current demand as both a game and food fish, is Yellow perch Perca flavescens. Yellow perch is a species well-suited for commercial aquaculture; however, there are several challenges to perch culture operations that have limited further growth of this species commercially. One challenge is dimorphism for body size in this species; males grow at a much slower rate (30%) and have a shorter life span than females. Another challenge is that the onset of sexual maturity begins before male Yellow perch reach marketable size (100-150g). The combination of dimorphic growth and the early onset of male sexual maturity results in a more rapid growth rate in female Yellow perch than in males. Therefore, traditional mixed-sex stocks of Yellow perch exhibit large size variation, with half of the stock (females) reaching market size significantly earlier than the other half (males). A possible solution to the challenge that Yellow perch sexual dimorphism presents to culture operations is the production of monosex female populations, as all-female stocks would reach market size faster than mixed sex stocks, with lower overall costs. There are several potential methods to produce all-female Yellow perch. This work focused on the development of gynogenesis methods, as well as the evaluation of the efficacy for temperature exposure. Production of Yellow perch gyngoens will directly result in all-female progeny. However, induction of gynogenesis requires application of physical shocks to newly fertilized embryos, which can negatively impact survival and cause deformities. There is the potential for gyngoens to be sex-reversed to phenotypic males (genetic (XX) females capable of producing sperm), which could then be used to produce an all-female generations that has not been exposed to physical shocks. Application of sex hormones has traditionally been used; however, temperature exposure has also shown to have the potential to produce phenotypic males, which can then be used to produce all-female Yellow perch in the next generation. Access to cryopreserved Yellow perch sperm will be crucial to the application of these methods to industry; therefore, we first improved the effectiveness of simple cryopreservation techniques of Yellow perch sperm by examining different cryoprotectants (dimethylsulfoxide [DMSO] versus methanol [MetOH]) utilizing two simple cryopreservation methods, the effect of absence versus presence of seminal plasma, and the effects of UV irradiation on sperm physiology following cryopreservation. Cryopreservation and cryoprotectants were evaluated based on post-thaw motility as well as on fertilization rate, embryonic survival, and hatching rate. We determined that both simple methods with either cryoprotectant in the presence of seminal plasma are efficient to cryopreserve Yellow perch sperm. We also determined based on survival and growth results from the larval rearing experiment that progeny derived from cryopreserved sperm do not experience growth suppression or higher mortality than progeny obtained from fresh control sperm. Results from the cryopreservation of UV irradiated sperm suggests that the combination of UV-irradiation and cryopreservation does not result in lower sperm motility than is expected after UV-irradiation alone, a promising result for future work with cryobanks for female monosex production. We then successfully produced triploid Yellow perch utilizing heat shocks and raised triploid individuals until sexual maturation in order to evaluate their reproductive ability, as well as the viability and performance of resulting progeny. Successful induction of triploidy was an important first step for determining conditions to achieve gynogenesis in Yellow perch. Further, results demonstrate that triploid Yellow perch females possess well-developed ovaries with no reduction, that are highly capable of being fertilized. However, triploid females are sterile, as majority of progeny produced were aneuploids and mass to total mortality was observed before progeny reached juvenile stage. We then utilized this experience with triploidy to begin developing methods of producing Yellow perch gyngoens. Methods of UV-irradiating sperm of Yellow perch and heterologous sperm were also evaluated. Various heat and pressure shock conditions were determined to be effective in restoring diploidy, including a pressure shock of 9,000 psi applied at 5 minutes post fertilization (mpf) for a 10 minute duration and a heat shock of 28-30°C applied at 5 mpf for a 12 minute duration. Unreliable availability of heterologous sperm from wild sources resulted in majority of gynogenesis trials to be conducted utilizing UV-irradiated sperm of Yellow perch. We found high variability in the required doses for full irradiation of sperm from different Yellow perch males, likely due to high and variable sperm concentration and inadequate dilution. As a result, majority of gynogen groups produced by irradiated perch sperm contained normal, diploid individuals produced by non-irradiated sperm fertilizing an egg. However, when heterologous Walleye sperm was used, the resulting gynogen group contained 100% gynogenetic individuals, as hybrids of Walleye and Yellow perch are nonviable. Based on our results, we suggest use of Walleye sperm (diluted 1:10 with extender and UV-irradiated at 7,000-9,000 J/m2) for production of Yellow perch gynogens. We also produced a series of progenies that included all-female, female-biased, male-biased, and mixed-sex cohorts in order to compare the growth and survival between these groups and further define the benefits of mono-sex culture of Yellow perch. We determined that all-female groups grew significantly better than all other groups, and there were no impacts on survival. Therefore, we can conclude that all-female Yellow perch stocks will increase the profitability and efficiency of aquaculture operations. Finally, we conducted an investigation into the influence of temperature on gonad differentiation in Yellow perch. Research has shown that exposure to high temperature during the labile sex determination phase can lead to the masculinization and production of phenotypic males in fishes. Such a mechanism in Yellow perch would provide an alternative, cost-effective method for farmers and industry personnel to produce their own stocks of neomales, which could then be used to produce all-female Yellow perch. We evaluated the effect of high temperature exposure from the time of first exogenous feeding, to the end of sex determination, in two generations of Yellow perch and observed masculinization effect in 6 of the 11 progenies produced in the first generation. The second generation has not yet reached sexual maturation, therefore, sex ratio results for the F2 will be reported in future studies. This collection of studies provides an integrated, comprehensive approach to the production of all-female Yellow perch stocks for increasing Yellow perch aquaculture production and provides highly valuable and novel information to the industry, which will open new avenues for increasing the production of Yellow perch through intensive culture.
Awarded Bookauthority's "Best Aquaculture Books of all Time" A comprehensive resource that covers all the aspects of sex control in aquaculture written by internationally-acclaimed scientists Comprehensive in scope, Sex Control in Aquaculture first explains the concepts and rationale for sex control in aquaculture, which serves different purposes. The most important are: to produce monosex stocks to rear only the fastest-growing sex in some species, to prevent precocious or uncontrolled reproduction in other species and to aid in broodstock management. The application of sex ratio manipulation for population control and invasive species management is also included. Next, this book provides detailed and updated information on the underlying genetic, epigenetic, endocrine and environmental mechanisms responsible for the establishment of the sexes, and explains chromosome set manipulation techniques, hybridization and the latest gene knockout approaches. Furthermore, the book offers detailed protocols and key summarizing information on how sex control is practiced worldwide in 35 major aquaculture species or groups, including fish and crustaceans, and puts the focus on its application in the aquaculture industry. With contributions from an international panel of leading scientists, Sex Control in Aquaculture will appeal to a large audience: aquaculture/fisheries professionals and students, scientists or biologists working with basic aspects of fish/shrimp biology, growth and reproductive endocrinology, genetics, molecular biology, evolutionary biology, and R&D managers and administrators. This text explores sex control technologies and monosex production of commercially-farmed fish and crustacean species that are highly in demand for aquaculture, to improve feed utilization efficiency, reduce energy consumption for reproduction and eliminate a series of problems caused by mixed sex rearing. Thus, this book: Contains contributions from an international panel of leading scientists and professionals in the field Provides comprehensive coverage of both established and new technologies to control sex ratios that are becoming more necessary to increase productivity in aquaculture Includes detailed coverage of the most effective sex control techniques used in the world's most important commercially-farmed species Sex Control in Aquaculture is the comprehensive resource for understanding the biological rationale, scientific principles and real-world practices in this exciting and expanding field.
This is a comprehensive overview of the Iraqi freshwater fishes containing of identification keys with original b/w total drawings, complete checklist and detailed species accounts with data on common names, systematics, key characters and morphology, distribution, habitat, biology, economic importance and conservation. The book contains also 16 color plates. BRIAN W. COAD has worked at the Canadian Museum of Nature, Ottawa since 1981. He was Curator of the National Fish Collection and is now a Research Scientist. From 1976 to 1979 he was an Associate Professor in the Department of Biology at Shiraz University, Iran and led expeditions to most parts of that country, collecting fishes for his systematic studies. His main research interests are on the systematics and faunistics of Canadian and Middle Eastern fishes. He is the author of over 320 scientific and popular works on fishes including such books as Guide to the Marine Sport Fishes of Atlantic Canada and New England (1992), Encyclopedia of Canadian Fishes (1995), Expedition Field Techniques: Fishes (2nd revised edition, 1998), and Fishes of Tehran Province and adjacent areas (2008). Books on the Arctic Marine Fishes of Canada and the Fishes of Afghanistan are in preparation. His website www.briancoad.com has a Dictionary of Ichthyology with over 23,000 terms defined, Fishes of Canada: Annotated Checklist, and booklength presentations on the Fishes of Canada's National Capital Region and Freshwater Fishes of Iran. He received his B.Sc. in Zoology in 1970 from the University of Manchester, England, an M.Sc. in 1972 from the University of Waterloo, Ontario and a Ph.D. in 1975 from the University of Ottawa.
