Angler and environmental influences on walleye Sander vitreus and muskellunge Esox masquinongy angler catch in Escanaba Lake, Wisconsin 2003–2015

Angler trip success and catch rates are dependent upon a fishes’ vulnerability to angling. Angling vulnerability can be influenced by angler-specific attributes (i.e., bait choice, lure size, use of a guide), and individual fish traits (i.e., boldness, aggression, stress responsiveness, and memory retention). The mechanisms that function in a fishes’ angling vulnerability, and contribute to catch rate, are likely correlated with environmental factors however, the influence of environmental factors on angling vulnerability are not well understood. We used the long-term (1946 –present) compulsory creel dataset from Escanaba Lake, WI, USA to test for interactions between angling vulnerability (i.e., angler trip success and catch rates) and environmental factors to better understand these dynamics in recreational fisheries. Our objective was to test for the influence of angler associated variables and environmental factors on open water angler trip success (i.e., catch ≥ one fish) and catch rate of walleye Sander vitreus and muskellunge Esox masquinongy during 2003–2015 using a hurdle model approach. Fishing trip success and catch rates for both species were most strongly influenced by angler-related variables (i.e., guide status, bait type, the proportion of the fish population previously caught). Environmental factors associated with lower light intensity (i.e., diel period, mean daily solar radiation, solar-Julian day interaction) had a positive influence on walleye vulnerability. Lower air temperatures and lunar position (moon overhead or underfoot) and phase (gibbous’ and full moon) also had a positive effect on walleye angling. Muskellunge trip success and catch rate were positively influenced by light metrics (i.e., diel period and mean daily solar radiation) and increased with air temperature. Lunar variables (position and phase), as well as wind speed and direction also influenced muskellunge angling vulnerability. A better understanding of the influence of environmental factors on angling vulnerability is an important component of fisheries management as management goals focus on balancing fish populations and creating satisfactory catch rates to enhance the angling experience. Our results suggest that angler-specific variables, light, temperature, lunar, and weather conditions influenced species-specific angling vulnerability for walleye and muskellunge.

Signatures of Selection and Genomic Diversity of Muskellunge (Esox masquinongy) from Two Populations in North America

Muskellunge (Esox masquinongy) is the largest and most prized game fish in North America. However, little is known about Muskellunge genetic diversity in Iowa’s propagation program. We used Whole-Genome Sequencing of 12 brooding individuals from Iowa and publicly available RAD-seq of 625 individuals from the St. Lawrence River in Canada to study the genetic differences between populations, analyze signatures of selection, and evaluate the levels of genetic diversity in both populations. Given that there is no reference genome available, reads were aligned to the genome of Pike (Esox lucius). Variant calling produced 7,886,471 biallelic variants for the Iowa population and 16,867 high-quality SNPs that overlap with the Canadian samples. Principal component analysis (PCA) and Admixture analyses showed a large genetic difference between Canadian and Iowan populations. Window-based pooled heterozygosity found 6 highly heterozygous windows in the Iowa population and Fst between populations found 14 windows with fixation statistic (Fst) values larger than 0.9. Canadian inbreeding rate (Froh = 0.32) appears to be higher due to the inbreeding of Iowa population (Froh = 0.03), presumably due to isolation of subpopulations. Although inbreeding does not seem to be an immediate concern for Muskellunge in Iowa, the Canadian population seems to have a high rate of inbreeding. Finally, this approach can be used to assess the long-term viability of the current management practices of Muskellunge populations across North America.

Signatures of selection and genomic diversity of Muskellunge (Esox masquinongy) from two populations in North America.

Muskellunge (Esox masquinongy) is the largest and most prized game fish in North America. However, little is known about Muskellunge genetic diversity in Iowa’s propagation program. We used Whole Genome Sequencing of 12 brooding individuals from Iowa and publicly available RAD-seq of 625 individuals from Saint-Lawrence river in Canada to study the genetic differences between populations, analyze signatures of selection, and evaluate the levels of genetic diversity in both populations. Given that there is no reference genome available, reads were aligned to the genome of Pike (Esox lucius). Variant calling produced 7,886,471 biallelic variants for the Iowa population and 16,867 high-quality SNPs that overlap with the Canadian samples. PCA and Admixture analyses showed a large genetic difference between Canadian and Iowan populations. Window-based pooled heterozygosity found 6 highly heterozygous windows in the Iowa population and Fst between populations found 14 windows with Fst values larger than 0.9. Canadian inbreeding rate (Froh=0.32) appears to be higher to the inbreeding of Iowa population (Froh=0.03), presumably due to isolation of subpopulations. Although inbreeding does not seem to be an immediate concern for Muskellunge in Iowa, the Canada population seems to have a high rate of inbreeding. Finally, this approach can be used to assess the long-term viability of the current management practices of Muskellunge populations across North America.

Signatures of selection and genomic diversity of Muskellunge (Esox masquinongy) from two populations in North America.

Background Muskellunge (Esox masquinongy) is the largest and most prized game fish for anglers in North America. However, little is known about Muskellunge genetic diversity in Iowa’s propagation program. We used whole genome sequence from 12 brooding individuals from Iowa and publicly available RAD-seq of 625 individuals from Saint-Lawrence river in Canada to study the genetic differences between populations, analyze signatures of selection that might shed light on environmental adaptations, and evaluate the levels of genetic diversity in both populations. Given that there is no reference genome available for Muskellunge, reads were aligned to the genome of Pike (Esox lucius), a closely-related species.Results Variant calling produced 7,886,471 biallelic variants for the Iowa population and 16,867 high-quality SNPs that overlap with the Canadian samples. The Ti/Tv values were 1.09 and 1.29 for samples from Iowa and Canada, respectively. PCA and Admixture analyses showed a large genetic difference between Canadian and Iowan populations. Moreover, PCA showed clustering by sex in the Iowan population although widow-based Fst did not find outlier regions. Window-based pooled heterozygosity found 6 highly heterozygous windows containing 244 genes in the Iowa population and Fst comparing the Iowa and Canadian populations found 14 windows with Fst values larger than 0.9 containing 641 genes. One enriched GO term (sensory perception of pain) was found through pooled heterozygosity analyzes. Although not significant, several enriched GO terms associated to growth and development were found through Fst analyses.Inbreeding calculated as Froh was 0.03 on average for the Iowa population and 0.32 on average for the Canadian samples. The Canadian inbreeding rate appears to be higher, presumably due to isolation of subpopulations, than the inbreeding rate of the Iowa population.Conclusions This study was the first to document that brood stock Muskellunge from Iowa showed marked genetic differences with the Canadian population. Additionally, despite genetic differentiation based on sex has been observed, no major locus has been detected. Inbreeding does not seem to be an immediate concern for Muskellunge in Iowa, but apparent isolation of subpopulations has caused levels of homozygosity to increase in the Canadian Muskellunge population. Finally, these results prove the validity of using genomes of closely related species to perform genomic analyses when no reference genome assembly is available.

Signatures of selection and genomic diversity of Muskellunge (Esox masquinongy) from two populations in North America.

Background Muskellunge (Esox masquinongy) is the largest and most prized game fish for anglers in North America. However, little is known about Muskellunge genetic diversity in Iowa’s propagation program. We used whole genome sequence from 12 brooding individuals from Iowa and publicly available RAD-seq of 625 individuals from Saint-Lawrence river in Canada to study the genetic differences between populations, analyze signatures of selection that might shed light on environmental adaptations, and evaluate the levels of genetic diversity in both populations. Given that there is no reference genome available for Muskellunge, reads were aligned to the genome of Pike (Esox lucius), a closely-related species.ResultsVariant calling produced 7,886,471 biallelic variants for the Iowa population and 16,867 high quality SNPs that overlap with the Canadian samples. The Ti/Tv values were 1.09 and 1.29 for samples from Iowa and Canada, respectively. PCA and Admixture analyses showed a large genetic difference between Canadian and Iowan populations. Moreover, PCA showed a clustering by sex in the Iowan population although widow-based Fst did not find outlier regions. Window based pooled heterozygosity found 6 highly heterozygous windows containing 244 genes in the Iowa population and Fst comparing the Iowa and Canadian populations found 14 windows with Fst values larger than 0.9 containing 641 genes. One enriched GO term (sensory perception of pain) was found through pooled heterozygosity analyzes. Although not significant, several enriched GO terms associated to growth and development were found through Fst analyses.Inbreeding calculated as Froh was 0.03 on average for the Iowa population and 0.32 on average for the Canadian samples. The Canadian inbreeding rate appears is presumably due to isolation of subpopulations.ConclusionsThis study is the first of its kind in Muskellunge from Iowa in which captured brood stock showed marked genetic differences with the Canadian population. Additionally, despite genetic differentiation based on sex has been observed, no major locus has been detected. Inbreeding does not seem to be an immediate concern for Muskellunge in Iowa, but apparent isolation of subpopulations has caused levels of homozygosity to increase in the Canadian Muskellunge population.These results prove the validity of using genomes of closely related species to perform genomic analyses when no reference genome assembly is available.

Signatures of selection and genomic diversity of Muskellunge (Esox masquinongy) from two populations in North America.

Background Muskellunge (Esox masquinongy) is the largest and most prized game fish for anglers in North America. However, little is known about Muskellunge genetic diversity in Iowa’s propagation program. We used whole genome sequence from 12 brooding individuals from Iowa and publicly available RAD-seq of 625 individuals from Saint-Lawrence river in Canada to study the genetic differences between populations, analyze signatures of selection that might shed light on environmental adaptations, and evaluate the levels of genetic diversity in both populations. Given that there is no reference genome available for Muskellunge, reads were aligned to the genome of Pike (Esox lucius), a closely-related species. Results Variant calling produced 7,886,471 biallelic variants for the Iowa population and 16,867 high quality SNPs that overlap with the Canadian samples. The Ti/Tv values were 1.09 and 1.29 for samples from Iowa and Canada, respectively. PCA and Admixture analyses showed a large genetic difference between Canadian and Iowan populations. Moreover, PCA showed a clustering by sex in the Iowan population although widow-based Fst did not find outlier regions. Window based pooled heterozygosity found 6 highly heterozygous windows containing 244 genes in the Iowa population and Fst comparing the Iowa and Canadian populations found 14 windows with Fst values larger than 0.9 containing 641 genes. One enriched GO term (sensory perception of pain) was found through pooled heterozygosity analyzes. Although not significant, several enriched GO terms associated to growth and development were found through Fst analyses. Inbreeding calculated as Froh was 0.03 on average for the Iowa population and 0.32 on average for the Canadian samples. The inbreeding rate appears is presumably due to isolation of subpopulations. Conclusions This study is the first of its kind in Muskellunge from Iowa in which captured brood stock showed marked genetic differences with the Canadian population. Additionally, despite genetic differentiation based on sex has been observed, no major locus has been detected . Inbreeding does not seem to be an immediate concern for Muskellunge in Iowa, isolation of subpopulations has caused levels of homozygosity to increase in the Canadian Muskellunge population. These results prove the validity of using genomes of closely related species to perform genomic analyses when no reference genome assembly is available.

Validity of age estimates from muskellunge (Esox masquinongy) fin rays and associated effects on estimates of growth

Accurate age estimates are critical for understanding life histories of fishes and developing management strategies for fish populations. However, validation of age estimates requires known-age fish, which are often lacking. We used known-age (ages 1–25) muskellunge (Esox masquinongy) to determine the precision and accuracy of age estimates from fin rays. We also determined whether fin location (anal or pelvic), fin ray number, and preparation methods affected accuracy and precision. Lastly, we determined whether von Bertalanffy growth parameters estimated from fin ray ages were similar to parameters estimated from known ages. Precision and accuracy of age estimates from anal and pelvic rays were similar and estimates were relatively precise (coefficient of variation = 8.5%) and accurate (mean absolute difference from known age = 0.85 years) for ages 4–15, but ages were overestimated for younger fish and underestimated for older fish. Growth models based on estimated age were similar to models based on known age. Anal and pelvic rays offer a nonlethal alternative for age estimation of muskellunge ages 4–15 and for producing reliable estimates of growth.