I. Wirgin - Academia.edu (original) (raw)
Papers by I. Wirgin
Biology Letters, 2008
Anadromous fishes are believed to make regular circuits of migration in the sea before homing to ... more Anadromous fishes are believed to make regular circuits of migration in the sea before homing to their natal rivers. Sea lampreyPetromyzon marinusis an anadromous fish that is an exception to this life-history pattern. It also differs from other anadromous fishes in that its adult phase is parasitic, a feeding strategy that should make homing problematic for lamprey cohorts that become widely dispersed through transport by the diverse hosts they parasitize. We sequenced a portion of the mitochondrial DNA control region from sea lampreys collected from 11 North American east coast rivers to test for genetic evidence of homing. There were no significant differences (Χ2=235.1,p=0.401) in haplotype frequencies among them, with almost 99 per cent of haplotypic diversity occurring within populations. These findings, together with concordant genetic results from other geographical regions and ancillary information on pheromonal communication, suggest that sea lamprey does not home but rath...
North American Journal of Fisheries Management, 2004
The robust redhorse Moxostoma robustum is a rare catostomid species that was recently ''rediscove... more The robust redhorse Moxostoma robustum is a rare catostomid species that was recently ''rediscovered'' in three Atlantic slope drainages in the southeastern United States, including the Oconee River, Georgia. Adult population size in the Oconee River is declining, and the population may be senescent due to recruitment failure. Evaluation of the environmental factors affecting the success of young life stages requires the ability to distinguish robust redhorse larvae from those of other redhorse species in the Oconee River. The use of morphological approaches, including size at collection date, have proven to be problematic in distinguishing larval robust redhorse from notchlip redhorse M. collapsum from the Oconee River. We developed a mitochondrial DNA (mtDNA) assay to distinguish between reference adults of these two redhorse species from the Oconee, Savannah, and Pee Dee rivers. This mtDNA assay was then applied to unknown larval redhorse collections from the Oconee River. In one collection, discordance was revealed in 40% of the individual larvae identified by both size at collection date and mtDNA. Of these, 75% of the fish thought to be notchlip redhorses based on size at date of collection exhibited robust redhorse mtDNA haplotypes. These results illustrate the utility of DNA techniques in characterizing the young life stages of fish and suggest that earlier surveys underestimated the abundance of larval robust redhorses in the Oconee River.
American Shad Alosa sapidissima in the Hudson River, New York, and coastwide have shown major lon... more American Shad Alosa sapidissima in the Hudson River, New York, and coastwide have shown major long-term
declines. A possible contributing factor is commercial fisheries that harvest this population outside of the Hudson
River estuary. Using previously published and new reference microsatellite data from 33 baseline populations, our
goals were (1) to estimate the proportion of Hudson River American Shad contributing to the two remaining major
mixed-stock fisheries along the Atlantic coast in Delaware Bay and the Bay of Fundy and (2) to estimate the
proportions of other American Shad stocks contributing to these two fisheries at the highest level of stock
specificity. Stock composition estimates for 2009 and 2010 Delaware Bay collections were made using three models
that ranged from the most simple question (Hudson River and Delaware Bay populations) to one with all 33
baseline populations included. In all cases, a Hudson River contribution nearly equal to that of the Delaware Bay
contribution was observed, indicating a substantial take on the otherwise protected Hudson River population.
When all baseline populations were included for the larger 2010 Delaware Bay collection, 19 showed nonzero
contributions, largely drawn from mid-Atlantic U.S. rivers. The 2009 Bay of Fundy collection showed
contributions from across most of the species’ range but was dominated by northern populations. Mixed-stock
analyses of collections from the two sites together indicate that these estuarine fisheries harvested not only proximal
populations but those originating from a wide latitudinal range.
Estuaries, 2001
Shortnose sturgeon, Acipenser brevirostrum, is a small, endangered species which occurs in 19 est... more Shortnose sturgeon, Acipenser brevirostrum, is a small, endangered species which occurs in 19 estuary systems along the east coast of North America. These populations are considered as separate entities by the U.S. National Marine Fisheries Service although evidence of morphologic or genetic differentiation among populations has not been documented. The purpose of this study was to compare morphological and genetic attributes among shortnose sturgeon collected from the Kennebec and Androscoggin Rivers, Maine, and the Hudson River, New York. Six morphometric and five meristic characteristics were quantified. Multivariate and univariate analyses of covariance and variance were used to assess differences among populations. Our analyses provided evidence for distinct populations in the Androscoggin and Kennebec Rivers, but character differentiation was greater between fish from these two locations and the Hudson River. Analysis of morphometric characters indicated significant differences in fish shape among the three rivers, with Hudson River sturgeon differing from the Maine rivers for the characters of head length, snout length, and mouth width. Significant differences were observed for meristic characters, but pairwise comparisons did not reflect a clear pattern of variability. Sequencing of a portion of the mitochondrial DNA control region revealed 15 haplotypes among 73 total specimens from the three rivers. Shortnose sturgeon from the Kennebec and Androscoggin Rivers were different from each other (p ؍ 0.0260); both differed significantly (p Ͻ 0.0001) from the Hudson River collection. Gene flow was estimated at approximately 7 female migrants per generation between the two Maine populations and about 1 per generation between each of the Maine populations and the Hudson River population. Such strong stock structuring among presumably recently established post-Pleistocene (Ͻ 10,000 yr) populations suggests that this species occurs in highly discrete units. Morphological and genetic variation observed in this study combined with current knowledge of life history attributes of shortnose sturgeon indicate that conservative management decisions are necessary until the patterns and extent of differentiation among populations species-wide can be investigated further.
Biology Letters, 2008
Anadromous fishes are believed to make regular circuits of migration in the sea before homing to ... more Anadromous fishes are believed to make regular circuits of migration in the sea before homing to their natal rivers. Sea lampreyPetromyzon marinusis an anadromous fish that is an exception to this life-history pattern. It also differs from other anadromous fishes in that its adult phase is parasitic, a feeding strategy that should make homing problematic for lamprey cohorts that become widely dispersed through transport by the diverse hosts they parasitize. We sequenced a portion of the mitochondrial DNA control region from sea lampreys collected from 11 North American east coast rivers to test for genetic evidence of homing. There were no significant differences (Χ2=235.1,p=0.401) in haplotype frequencies among them, with almost 99 per cent of haplotypic diversity occurring within populations. These findings, together with concordant genetic results from other geographical regions and ancillary information on pheromonal communication, suggest that sea lamprey does not home but rath...
North American Journal of Fisheries Management, 2004
The robust redhorse Moxostoma robustum is a rare catostomid species that was recently ''rediscove... more The robust redhorse Moxostoma robustum is a rare catostomid species that was recently ''rediscovered'' in three Atlantic slope drainages in the southeastern United States, including the Oconee River, Georgia. Adult population size in the Oconee River is declining, and the population may be senescent due to recruitment failure. Evaluation of the environmental factors affecting the success of young life stages requires the ability to distinguish robust redhorse larvae from those of other redhorse species in the Oconee River. The use of morphological approaches, including size at collection date, have proven to be problematic in distinguishing larval robust redhorse from notchlip redhorse M. collapsum from the Oconee River. We developed a mitochondrial DNA (mtDNA) assay to distinguish between reference adults of these two redhorse species from the Oconee, Savannah, and Pee Dee rivers. This mtDNA assay was then applied to unknown larval redhorse collections from the Oconee River. In one collection, discordance was revealed in 40% of the individual larvae identified by both size at collection date and mtDNA. Of these, 75% of the fish thought to be notchlip redhorses based on size at date of collection exhibited robust redhorse mtDNA haplotypes. These results illustrate the utility of DNA techniques in characterizing the young life stages of fish and suggest that earlier surveys underestimated the abundance of larval robust redhorses in the Oconee River.
American Shad Alosa sapidissima in the Hudson River, New York, and coastwide have shown major lon... more American Shad Alosa sapidissima in the Hudson River, New York, and coastwide have shown major long-term
declines. A possible contributing factor is commercial fisheries that harvest this population outside of the Hudson
River estuary. Using previously published and new reference microsatellite data from 33 baseline populations, our
goals were (1) to estimate the proportion of Hudson River American Shad contributing to the two remaining major
mixed-stock fisheries along the Atlantic coast in Delaware Bay and the Bay of Fundy and (2) to estimate the
proportions of other American Shad stocks contributing to these two fisheries at the highest level of stock
specificity. Stock composition estimates for 2009 and 2010 Delaware Bay collections were made using three models
that ranged from the most simple question (Hudson River and Delaware Bay populations) to one with all 33
baseline populations included. In all cases, a Hudson River contribution nearly equal to that of the Delaware Bay
contribution was observed, indicating a substantial take on the otherwise protected Hudson River population.
When all baseline populations were included for the larger 2010 Delaware Bay collection, 19 showed nonzero
contributions, largely drawn from mid-Atlantic U.S. rivers. The 2009 Bay of Fundy collection showed
contributions from across most of the species’ range but was dominated by northern populations. Mixed-stock
analyses of collections from the two sites together indicate that these estuarine fisheries harvested not only proximal
populations but those originating from a wide latitudinal range.
Estuaries, 2001
Shortnose sturgeon, Acipenser brevirostrum, is a small, endangered species which occurs in 19 est... more Shortnose sturgeon, Acipenser brevirostrum, is a small, endangered species which occurs in 19 estuary systems along the east coast of North America. These populations are considered as separate entities by the U.S. National Marine Fisheries Service although evidence of morphologic or genetic differentiation among populations has not been documented. The purpose of this study was to compare morphological and genetic attributes among shortnose sturgeon collected from the Kennebec and Androscoggin Rivers, Maine, and the Hudson River, New York. Six morphometric and five meristic characteristics were quantified. Multivariate and univariate analyses of covariance and variance were used to assess differences among populations. Our analyses provided evidence for distinct populations in the Androscoggin and Kennebec Rivers, but character differentiation was greater between fish from these two locations and the Hudson River. Analysis of morphometric characters indicated significant differences in fish shape among the three rivers, with Hudson River sturgeon differing from the Maine rivers for the characters of head length, snout length, and mouth width. Significant differences were observed for meristic characters, but pairwise comparisons did not reflect a clear pattern of variability. Sequencing of a portion of the mitochondrial DNA control region revealed 15 haplotypes among 73 total specimens from the three rivers. Shortnose sturgeon from the Kennebec and Androscoggin Rivers were different from each other (p ؍ 0.0260); both differed significantly (p Ͻ 0.0001) from the Hudson River collection. Gene flow was estimated at approximately 7 female migrants per generation between the two Maine populations and about 1 per generation between each of the Maine populations and the Hudson River population. Such strong stock structuring among presumably recently established post-Pleistocene (Ͻ 10,000 yr) populations suggests that this species occurs in highly discrete units. Morphological and genetic variation observed in this study combined with current knowledge of life history attributes of shortnose sturgeon indicate that conservative management decisions are necessary until the patterns and extent of differentiation among populations species-wide can be investigated further.