Broodstock Selection Research Articles

Transcriptome analysis of germ cell changes in male Chinese mitten crabs (Eriocheir sinensis) induced by rhizocephalan parasite, Polyascus gregaria

The parasitism by Polyascus gregaria on Eriocheir sinensis induces feminization of the appearance of male crabs, misleading fishermen to bring them to the breeding ponds as female crabs to cultivate broodstock selection. However, there are few studies on whether P. gregaria feminizes the male germ cells, resulting in a decline in the fecundity of male crabs. Therefore, this study aims to clarify the changes in gene expression levels of male crab testes after being parasitized by P. gregaria through transcriptome sequencing to evaluate the change in fecundity. We selected parasitized and healthy male crabs from a pond culture for comparison of gene expression in germ cells. The results showed that, compared with healthy male crabs, there were 104 genes with significantly different expressions, of which 79 were up-regulated and 25 were down-regulated. These genes are mainly focused on the cytoskeleton pathway in cell components and cellular protein complex assembly in biological processes. Several spermatogenesis-related genes, such as Kazal-type protease inhibitor, which inhibits gelatinolytic activities of sperm proteases, and juvenile hormone esterase 6, which degrades methyl farnesoate, were up-regulated; while the down-regulated expression of certain heat shock proteins may lead to spermatogenic dysfunction. In addition, some immune-related genes, such as double whey acidic protein domain-containing protein and serine proteinase inhibitor 3, were significantly up-regulated. These results indicated that P. gregaria changed the development process and cell structure of male host germ cells to inhibit sperm proliferation and maturation, while multiple immune pathways in the hosts were activated to resist P. gregaria invasion.

Applying coral breeding to reef restoration: best practices, knowledge gaps, and priority actions in a rapidly‐evolving field

Reversing coral reef decline requires reducing environmental threats while actively restoring reef ecological structure and function. A promising restoration approach uses coral breeding to boost natural recruitment and repopulate reefs with genetically diverse coral communities. Recent advances in predicting spawning, capturing spawn, culturing larvae, and rearing settlers have enabled the successful propagation, settlement, and outplanting of coral offspring in all of the world's major reef regions. Nevertheless, breeding efforts frequently yield low survival, reflecting the type III survivorship curve of corals and poor condition of most reefs targeted for restoration. Furthermore, coral breeding programs are still limited in spatial scale and species diversity. Here, we highlight four priority areas for research and cooperative innovation to increase the effectiveness and scale of coral breeding in restoration: (1) expanding the number of restoration sites and species, (2) improving broodstock selection to maximize the genetic diversity and adaptive capacity of restored populations, (3) enhancing culture conditions to improve offspring health before and after outplanting, and (4) scaling up infrastructure and technologies for large‐scale coral breeding and restoration. Prioritizing efforts in these four areas will enable practitioners to address reef decline at relevant ecological scales, re‐establish self‐sustaining coral populations, and ensure the long‐term success of restoration interventions. Overall, we aim to guide the coral restoration community toward actions and opportunities that can yield rapid technical advances in larval rearing and coral breeding, foster interdisciplinary collaborations, and ultimately achieve the ecological restoration of coral reefs.

Analisis Finansial Usaha Pembenihan Ikan Pada Kondisi Pandemi Covid-19 Di Desa Ponoragan Kecamatan Loa Kulu Kabupaten Kutai Kartanegara

The research objective is to determine the technical and management aspects, feasibility hatchery business, the difference in the income of cultivator in the conditons of the covid-19 pandeic and before the covid-19 pandemic, as well as knowing the obstacles and solutions fish hatchery business in Ponoragan Village. The research was carried out from September 2021 to March 2022 in Ponoragan Village, Loa Kulu District, Kutai Kartanegara Regency. A sample of 20 respondents with reference to the method purposive sampling. 
 The results showed that the technical aspects consisted of pond preparation, selection of broodstock, spawning, stocking of larvae, rearing nener and harvesting seeds. The management functions used by hatchery cultivators are planning, implementation and monitoring management functions. Then, based on the criteria of BCR, NPV, IRR, BEP and Payback Period, it shows that the fish hatchery business in Ponoragan Village is feasible to run. The results of the T-test showed that there was a significant difference between the income of cultivators before and during the covid-19 pandemic, as well as the problems faced by hatchery cultivators, namely weather, pests and varieties. The solution is that farmers make fences from nets around the pond to prevent flooding, while for pests, farmers make snares from threads that are pulled on each side above the pond.

Selecting goldfish broods use the weighted product and simple additive weighting methods

Majalaya carp is a freshwater fish that has important economic value and is widespread in Indonesia. Goldfish is the most cultivated fish because it has many advantages both physiologically and genetically. Several factors of assessment in the selection of superior brood stock that can be considered in the cultivation of goldfish cultivators are; ideal body weight, fish movement, physical deformities, scales, and the base of the tail. All of these factors can help in the decision-making process for superior goldfish. This study uses two methods, namely the simple additive weighting (SAW) method and the weighted product (WP) method. Based on the results of research that has been carried out on 20 superior broodfish of Majalaya goldfish, the level of accuracy is obtained by comparing with existing data. The WP method gets an accuracy value of 90% while the SAW method gets an accuracy value of 80%.

Opportunities for improving feed efficiency and spinal health in New Zealand farmed Chinook salmon (Oncorhynchus tshawytscha) using genomic information

Chinook salmon (Oncorhynchus tshawytscha) is an important aquaculture species in New Zealand and selective breeding since the 1990s has resulted in significant gains in growth related traits. However, feed conversion ratio (FCR) remains highly variable in this species and higher than in other farmed salmonids. Some farmed Chinook salmon are also susceptible to late onset spinal curvature, which further reduces production efficiency. Therefore, the objective of this study was to determine the potential for selecting for improved FCR and reduced spinal curvature while also improving growth. For the evaluation, 82 pedigree families were obtained from two commercial breeding programmes and genotyped using genotyping-by-sequencing to generate a genomic relatedness matrix. Genotyped and tagged juveniles were reared together for 12 months in seawater trial tanks up to ∼2.0 Kg. Multiple assessments of weight, condition factor (CF), feed intake (FI), FCR and skeletal deformity were completed and analysed to estimate genetic parameters (heritability, phenotypic and genetic correlations). High heritabilities were estimated for weight and CF and moderate for spinal curvature. Growth, feed intake and FCR traits had low to moderate heritabilities and demonstrated potential for improvement through selection. Genetic correlations suggested some progress in FCR would be made through selection for growth, but larger gains will be achieved by quantifying FI. An unfavourable genetic correlation was uncovered between CF and spinal curvature and this should be considered when developing breeding goals for commercial broodstock selection.

Evaluation on feeding with sente leaves and enrichment on the conditioning of giant gourami (Osphronemus gouramy) broodstock

Spawning in the aquaculture of giant gourami is an important factor which determines the success of production because it supports the sustainability and improvement of the quality and quantity of giant gourami fry in aquaculture activities. The purpose of this study was to evaluate the feeding in the conditioning of giant gourami (Osphronemus gouramy) broodstock. The methodology carried out included the preparation of spawning ponds, broodstock selection, broodstock feeding, spawning, conditioning, nest inspection and egg collection, egg handling, egg hatching, and larval rearing. The eggs produced were 21.452 eggs with 18.714 fertilized eggs and 2,738 unfertilized eggs, and the Fertilization Rate (FR) value obtained during the study was 87.3%. Eggs that successfully hatched into larvae were as many as 16.238 while eggs that did not hatch were as many as 2.341 eggs, and the Hatching Rate (HR) value obtained was 87%. The water quality data obtained from the broodstock pond and the hatching pond included DO with a range of 5.88 – 6.11 mg/L, a temperature of 27.2°C – 28.2°C, and a pH ranging from 7.21 to 7.27.

Molecular markers for differentiation of Fenneropenaeus merguiensis among Penaeus species

The banana shrimp Fenneropenaeus merguiensis is a favourite among consumers. Therefore, overfishing has occurred. Conservation of this shrimp in the wild is essential. Conservation technologies, such as broodstock selection and germ cell transplantation, require molecular markers to discriminate F. merguiensis from other shrimps. This study developed biomarkers to distinguish F. merguiensis from other cultivated shrimps: Penaeus vannamei, Penaeus monodon and Macrobrachium rosenbergii. VASA 160 was used to differentiate F. merguiensis spermatogonia from the other three shrimps. Digestion of the amplified COI (cytochrome oxidase I) fragment with XbaI could discriminate the DNA of F. merguiensis and P. monodon from P. vannamei or M. rosenbergii. In comparison, SpeI digestion of the COI fragment differentiated F. merguiensis from P. monodon. COI266 identified the DNA of F. merguiensis from that of P. vannamei, P. monodon, and the PCR of Fm-15 showed a distinct pattern in F. merguiensis. Besides, the sensitivity of the biomarkers was determined by mixing the DNA of F. merguiensis with that of P. vannamei. VASA160, COI-RFLP and COI266 had a high sensitivity of 1:1000, while Fm 15 was at 1:100. Consequently, 30 processed shrimp foods were identified using these developed markers, and these markers will help monitor these four shrimp species in the future.

Manajemen Pembenihan Ikan Kerapu Bebek (Chromileptes Altivelis) Untuk Menghasilkan Benih Yang Optimal

Humpback grouper Chromileptes altivelis is a marine fish that lives in tropical waters, especially in Indonesia. This fish has a high economic value and is the most expensive type of grouper in Indonesia. It can be used as ornamental fish or raised for consumption. Hatchery activities were started from brood rearing to produce productive broodstock, proper broodstock selection, multivitamin administration, and good environmental management. Humpback grouper was spawned en masse with a male to female ratio of 1:2. Fecundity of 1 female humpback grouper >300,000 eggs with a rematuration period of 20-30 days. Spawning using natural techniques accompanied by environmental manipulation, fish spawn for seven days during the dark moon. The number of eggs obtained was 560,000-2,000,000 eggs, with fertilization rate was 30-60%, and the hatching rate was 65-88%. The eggs that hatch into larvae were stocked with a density of 15-25 L-1. The larvae were transferred to a seed container at a size of 2-3 cm with a maintenance period of 40-45 days. Feeding at satiation using pellets measuring 1.1-2.0 mm with a protein content of 52-54% and 9-12% fat. Seeds were harvested at the age of 60 days when they reached a size of 5-6 cm, the survival rate was 3-5%.

Histology and External Morphological Assessment on Ovarian Maturation Stages of Wild Female Banana Shrimp, Penaeus merguiensis (de Man, 1888) for Broodstock Selection Purpose.

Study on ovarian maturation stages were carried out using external morphological assessment of ovarian colourations and histological assessment of Oocyte structure for broodstock selection purpose. Stage 1 to Stage 4 of female shrimps broodstock were sampled from Kuala Muda, Kedah, Malaysia. Four obvious colourations of ovary stages were identified which are: yellow (Stage 1), green yellowish (Stage 2), light greenish (Stage 3) and dark green (Stage 4) through the morphological assessment. The Gonadosomatic Index (GSI) showed significant increment as the gonad reach advance stages. Histological assessment of Stage 1 ovary identified perinucleolar oocyte (PO) with small size oocytes. Stage 2 ovary was identified with yolkless oocyte (YO), Stage 3 ovary was identified with late stage of yolky globules and Stage 4 ovary was identified with fully yolky globules. From the results achieved, it can be concluded that the ovarian colourations and GSI can be applied to identify the ovarian maturation stages, meanwhile, the histology assessment is the most precise method to determine the ovarian maturation stages in more details and accurate for each of the ovarian maturation stages.

Peningkatan Produktivitas Usaha Budidaya Ayam Kampung UKM Putra Budi Kecamatan Mojolaban Kabupaten Sukoharjo

<p><em><strong>Increasing the Productivity of Kampong Chicken in the Putra Budi SME’s Mojolaban District Sukoharjo Regency</strong></em>. Putra Budi Small and Medium-Sized Enterprises (SMEs) located in Bekonang Village, Mojolaban Subdistrict, Sukoharjo Regency, is a business unit owned by Mr Apri with traditional kampong chicken breeding with a capacity of 50-100 chickens/period. Mr Apri. Putra Budi SMEs is engaged in traditional village chicken farming with a capacity of 50-100 chickens/period. Mr Apri started this business 5 years ago, but the maintenance method is still simple and has not been carried out intensively so that the productivity is low. Chicken sales are carried out on a wholesale basis, causing lower prices. Providing feed that does not meet the standard needs of livestock. The main problem faced by Putra Budi SME’s lies in the management of native chicken maintenance which includes management of feed, cages, sanitation, selection of broodstock, and hatching which are carried out traditionally (extensively). This service aims to increase the business of native chicken cultivation by implementing intensive cultivation, diversifying the marketing pattern of native chickens, and being able to increase partner income. Some of the solutions offered are to provide broader knowledge about the management of domestic chicken rearing which is still extensive/traditional towards programmed intensive management. The result of this service activity is that SME’s can apply feed management by selecting feed raw materials around the location and the practice of compiling quality native chicken rations, broiler-type chicken maintenance systems that are free from dangerous diseases/viruses, increasing productivity, efficiency, and speed of return on investment, and can establish cooperation with restaurants or SMEs processing native chicken. Based on the economic analysis carried out, the maintenance of the Putra Budi village chickens with 200 chickens experienced a 5% depletion and earned a profit of IDR 1,400,000 per breeding period.</p>

Sablefish ( Anoplopoma fimbria ) parentage analyses in aquaculture

Sablefish (Anoplopoma fimbria) is a commercially valuable species in Canada with limited aquaculture development. In this study, we partner with Golden Eagle Sablefish in British Columbia (Canada) to assess the role of brood stock selection in hatchery production. Mortality in the hatchery setting is high, especially during the first year of development; thus, interventions that enhance early survival have the potential to dramatically improve productivity. Here, we determined the parentage of offspring produced by a brood stock population of 12 females and 6 males. Focusing on a 2019 hatchery cohort (‘Implant 5 2019’), we sampled offspring at 9 months (N = 70) and 12 months of age (N = 124). We observed considerable family-level variation in productivity; out of 30 crosses, 5 pairs produced 69% of the progeny. At the individual level, 5 of the 12 brood stock females produced 90% of the offspring surveyed, and 3 of the 6 males sired 93% of the offspring. These data provide strong support for the hypothesis that sablefish survival in the hatchery setting can be improved through selective breeding.

Genetic Variability, Population Structure, and Relatedness Analysis of Meagre Stocks as an Informative Basis for New Breeding Schemes

This study evaluates the genetic diversity of different meagre broodstocks sampled in Greece. A multiplex of twelve microsatellite markers was used to genotype 946 fish from eleven stocks and batches used for broodstock selection, and the genetic data was used to calculate genetic population parameters as well as to investigate the genetic differentiation between stocks. The results from a relatedness analysis were used as the guiding lines for a fine-tuned and overall evaluation of the genetic distance between stocks, and the choice of candidate breeders from some of them. The approach implemented in this study uses well-established population genetics methods to evaluate the selection of breeder candidates in aquaculture commercial conditions utilizing a descriptive genetic data set based on microsatellite analyses, and to outline an efficient methodology for establishing the basis of new breeding schemes.

THE RELATIONSHEEP OF THE BREEDING VALUE OF BULLS WITH THE PRODUCTIVITY OF THEIR MOTHERS AND THE BREEDING VALUE OF THEIR PARENTS BREEDING

THE RELATIONSHEEP OF THE BREEDING VALUE OF BULLS WITH THE PRODUCTIVITY OF THEIR MOTHERS AND THE BREEDING VALUE OF THEIR PARENTS BREEDING

Freshwater, Landlocked Grand Lake Strain of Atlantic Salmon (Salmo salar L.) as a Potential Genetic Source of Long Chain Polyunsaturated Fatty Acids Synthesis

Selection efforts focused on adaptation to plant-based diets, particularly the ability to synthesize polyunsaturated fatty acids (PUFA), are now emerging in aquaculture. Landlocked salmon (Grand Lake population; GL) may differ from the commercial Saint John River (SJR) strain in terms of PUFA metabolism. The objective of this study was to determine if GL salmon can contribute toward broodstock selection for enhanced PUFA synthesis. Two diets containing either fish oil (FO) or plant-based oil (FO-free) were fed to the SJR and GL strains (∼58 g/fish) for 16 weeks. Growth, liver, and muscle fatty acid (FA) content, and transcript expression of lipid metabolism and inflammation-related genes were evaluated. GL salmon fed the FO diet showed reduced growth compared to SJR salmon (fed either diet); however, GL salmon fed the FO-free diet, growth was not significantly different compared to any group. In liver, SJR salmon fed the FO-free diet had higher levels of n-6 PUFAs (21.9%) compared to GL fed the same diet (15.9%); while GL salmon fed the FO-free diet had higher levels of monounsaturated FAs (48.9%) compared with SJR salmon fed the same diet (35.7%). 20:5n-3 and 22:6n-3 were the same in GL and SJR salmon liver and muscle, respectively, fed the FO-free diet. In liver, GL salmon fed the FO-free diet had higher acac and acly compared to all treatments and had higher fasb compared to both strains fed the FO-diet. GL salmon fed the FO-free diet had higher cd36c and fabp3b in liver compared to GL salmon fed the FO diet and SJR salmon fed either diet. GL salmon fed the FO-free diet had higher lect2a and pgds in liver compared to SJR salmon fed the FO-free diet. In muscle, GL salmon fed the FO-free diet had higher fadsd5 and fadsd6b compared with both strains fed the FO diet. These results suggest there is a genetic basis behind the potential for GL salmon to utilize FO-free diets more efficiently than SJR salmon, with regards to FA metabolism.

Differentially methylated gene regions between resistant and susceptible heat-phenotypes of the Pacific oyster Crassostrea gigas

Heat stress is one of the factors that affect aquaculture production of the Pacific oyster Crassostrea gigas in Mexico, and research aiming to improve heat tolerance is required. C. gigas breeding stock, produced for genetic improvement, is being implemented, and breeding lines available with 50 families were characterized for their heat-tolerance, selecting the two-most heat-resistant and the two-most heat-susceptible families. These families were analyzed for differences in their DNA methylation patterns after maintaining them for 30 days in a regime of oscillating temperatures (26 °C to 34 °C), similar to what is found in culture areas of Mexico. Whereas no differences were found in global methylation among heat-phenotypes, differentially methylated regions (DMRs) were found between phenotypes. Temperature modifies the methylation in gene bodies of C. gigas, where the heat-resistant phenotype (RR) showed more genes with DMRs in promoters (3672), exons (6340), and introns (18,685). Hyper-methylated genes among phenotypes were more abundant in RR introns (122), followed by exons (23), and promoters (2), whereas hypo-methylated regions corresponded to ten in introns, three in exons, and one in promoters. Hyper-methylated DMRs were mostly found in genes associated with processes such as regulation of gene expression, ions interactions, metabolism, and production of cellular components. This suggests that DMRs among heat-phenotypes in C. gigas families are involved in the heat-shock stress response regulated by methylation. The DMRs reported in this study could be used as methylation markers for a future broodstock selection.

Отримання та вирощування мальків великоротого окуня (Micropterus salmoides (Lacеpеde, 1802)) в умовах тепловодних ставових рибних господарств (огляд)

Purpose. Largemouth bass (Micropterus salmoides), a fish species native to freshwaters of North America, is a promising object of aquaculture all over the world. This is evidenced by the fact that this species is currently actively cultivated in aquaculture of more than 50 countries worldwide, on all continents, with the exception of Antarctica and Australia, both for recreational fishing and as a table fish. If we consider the history of breeding and cultivation of the largemouth bass, we can note a tendency to a continuous expansion of the stages of cultivation and transition from polyculture to monoculture. For example, in the first half of the last century, fish farms in the United States raised mainly juveniles of largemouth bass for stocking to natural water bodies, but currently most farms use the full production cycle from fry to marketable fish. In addition, earlier largemouth bass was used in many countries mainly as an additional object of aquaculture (biomeliorator) to increase the production of common carp, but now, thanks to the development of recreational fishing, it is increasingly becoming the main object of aquaculture, which is facilitated by the intensification of cultivation methods. Nowadays, there are many methods of growing largemouth bass, from the simplest, extensive, when fish are raised on natural food supply, to most intensive using flow-through aquaculture systems and off-season spawning. On the territory of Ukraine, it may be effective to use pond aquaculture of largemouth bass, which begins from the production of larvae and fry at fish farms. This stage of fish farming will be discussed in this article. Findings. This article contains brief information on method of natural spawning of largemouth bass, filling ponds with water, selection of broodstock and norms for their stocking to spawning ponds, spawning behavior of fish, peculiarities of caring for larvae and fry, sorting juveniles, as well as minimizing injuries during manipulations with fish. Practical value. Information from this review can be used for development of a new method for production of largemouth bass larvae and fry at warm-water pond farms in Ukraine, taking into account climatic conditions and local specificities of aquaculture. Key words: Largemouth bass, Micropterus salmoides, recreation fishing, sport fishing, pond fish farm, aquaculture, biomeliorator, larvae, fry, polyculture, monoculture, intensification, perspective species.

The technology of striped catfish broodstock (Pangasius hypophthalmus) in high-quality maintenance

Striped catfish (P. hypophthalmus) is a high economic value and is a determining factor at the hatchery stage. Quality catfish brooders that can produce superior seeds can be obtained through good handling. The purpose of this study is to gain knowledge in the maintenance techniques of catfish broodstock. The working methods used in the study is a descriptive method with primary and secondary data collection. Striped catfish broodstock uses a recirculation system which includes preparation of pond maintenance, broodstock maintenance, feed management, water quality management, broodstock selection, and spawning. The results of the average water quality parameters for 25 days are turbidity 17.85 cm, temperature 29.51°C, DO 4.23 mg/L, ammonium 0.005 mg/L, and pH 7.54. The average weight measurements in the first and second sampling are 3.11 kg and 3.13 kg, while the average length measurements in the first and second sampling are 55 cm and 56.05 cm. The growth rate in the maintenance of catfish broodstock for 21 days is 9.52 grams/day, and the specific growth rate is 0.028%. Catfish spawning uses a ratio of ten males and three females.

Identification of Priority Sites to Support Management of Commercially Important Sea Cucumber Species by Applying Infomap and Habitat Filters to Larval Dispersal Data

Stocks of commercially valuable sea cucumber species have declined in most tropical countries, which supply majority of the global demand. This work aimed to locate priority sites for the management ofHolothuria scabraandStichopus horrensin the western central Philippines. A passive larval dispersal model was run under four monsoonal regimes (Northeast monsoon, dry-transition, Southwest monsoon, and early Northeast monsoon), and the results subjected to theInfomapnetwork detection algorithm. Three clusters of closely related geographical nodes were identified [southeastern Palawan (Group I), western Panay and eastern Mindoro (Group II), and northern and western Palawan with western Mindoro (Group III)]. Remotely sensed habitat data were used to parameterize the degree of connectivity observed among sites (H. scabraspawning and settlement requires the presence of seagrass and mangrove, whileS. horrensrequires corals and seagrass). Local retention, self-recruitment, settlement success and sink diversity were then calculated for each node with suitable habitat. The locations were ranked according to each metric and those with higher larval export rates, a higher diversity of larval sources and a high degree of successful larval contribution to other sites were deemed crucial for the management of wild populations. Sixteen high-priority sites were identified, distributed mainly along northern Palawan and western Panay. Six sites were common for both species at different seasons, and no single location fulfilled all stated criteria across the four seasons and both sea cucumber species considered. The priority sites for management could serve as broodstock selection and juvenile restocking areas for aquaculture production clusters, which when properly implemented, could lead to an increase in sea cucumber production and contribute to natural populations. On a broader scale, the designation of closely related clusters and incorporation of habitat requirements to dispersal data provided critical input for the delineation of ecologically meaningful management units for sea cucumbers within the region.

Manifestation And Endoparacitic Intensity On Gonggong Conch (Laevistrombus turturella)

Habitat the gonggong conch (Laevistrombus turturella) also known as Dog conch is a species from the Gastropod class that can be found in shallow waters with muddy sand substrate. In Kepulauan Riau Province, these animals are hunted by fishermen to sell to consumers since gonggong conch is a favourite culinary in this province. The availability of conch in the market has only relied on natural catches. The high consumption and natural fluctuations have decreased the conch population. To maintain the sustainability of the dog conch, it is necessary to carry out the cultivation activities. The cultivation begins with the selection of quality broodstock. The gonggong conch of natural origin needs to be determined before cultivation, in order to prevent the entry of disease in the cultivation system i.e. parasites. This study includes the determination, prevalence and infection intensity of endoparasites in conch from Madong Bay, Tanjungpinang. The results showed that the total length of the conch shells ranged from 55.5 to 79.5 mm with an average length of 67.72 mm and a frequency mode of 64.6 mm. The sex ratio between male and female conch is 1:1.1 (not ideal) n=30. Two kinds of parasites were found in the digestive tract of gonggong conchs are conoidacid oocysts and trematode sporocysts. The number of endoparasites, prevalence and intensity in wild caught has high numbers involving conoidacid oocysts (prev=100%; I=48.23 ind/conch) and trematode sporocysts (prev=100%; I= 135.33 ind/conch). It was concluded that the level of endoparasites infection in the dog conch from the Madong Bay was categorized as moderate-to-severe.

Spontaneous hybridization and introgression between walleye (Sander vitreus) and sauger (Sander canadensis) in two large reservoirs: Insights from genotyping by sequencing.

Anthropogenic activities may facilitate undesirable hybridization and genomic introgression between fish species. Walleye (Sander vitreus) and sauger (Sander canadensis) are economically valuable freshwater species that can spontaneously hybridize in areas of sympatry. Levels of genomic introgression between walleye and sauger may be increased by modifications to waterbodies (e.g., reservoir development) and inadvertent propagation of hybrids in stocking programs. We used genotyping by sequencing (GBS) to examine 217 fish from two large reservoirs with mixed populations of walleye and sauger in Saskatchewan, Canada (Lake Diefenbaker, Tobin Lake). Analyses with 20,038 (r90) and 478 (r100) single nucleotide polymorphisms clearly resolved walleye and sauger, and classified hybrids with high confidence. F1, F2, and multigeneration hybrids were detected in Lake Diefenbaker, indicating potentially high levels of genomic introgression. In contrast, only F1 hybrids were detected in Tobin Lake. Field classification of fish was unreliable; 7% of fish were misidentified based on broad species categories. Important for activities such as brood stock selection, 12 of 173 (7%) fish field identified as pure walleye, and one of 24 (4%) identified as pure sauger were actually hybrids. In addition, two of 15 (13%) field‐identified hybrids were actually pure walleye or sauger. We conclude that hybridization and introgression are occurring in Saskatchewan reservoirs and that caution is warranted when using these populations in stocking programs. GBS offers a powerful and flexible tool for examining hybridization without preidentification of informative loci, eliminating some of the key challenges associated with other marker types.