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Papers by Dawn Dittman

Growth differences in oysters, Crassostrea virginica, from different estuaries

Journal of Shellfish Research

The protistan parasite Perkinsus marinus has been responsible for high mortality of eastern oyste... more The protistan parasite Perkinsus marinus has been responsible for high mortality of eastern oysters, Crassostrea virginica, along the Atlantic and Gulf Coast of the United States. It also causes sublethal effects, although an impact on reproduction has heretofore been difficult to demonstrate. We examined the effect of P. marinu.s infection on growth, reproduction (as measured by relative gonadal size, and the proportional representation of gametogenic tissue and gametes in the gonad), and condition index of eastern oysters. Oysters of known age and genetic history were exposed to P. marinus infection and sampled at24 week intervals over an 1l-month period during the 1990-1991 epizootic in Delaware Bay. During this time, 50 to l00%o of the oysters had detectable infections and nearly 55%o died. Shell growth rates were inhibited as infections intensified during initial exposure in autumn 1990, but resumed in the spring and remained high, even after infection became heavy. The effect on reproduction varied with the stage of the gametogenic cycle. The relative gonadal size and the proportion of gametogenic tissue in the gonad, as well as the condition index, were most strongly depressed during the spring gametogenic period; however, there was no significant effect of parasite burden when the oysters were reproductively mature and ready to spawn. Data suggested that infected oysters, recovered, produced gametes, and spawned in early summer. Other studies have found inconsistent evidence of sublethal deleterious effects of P. marinu.s on reproduction. By sampling throughout the year and employing oysters of known genetic background, of the same age, reared in a common environment, and for which the timing of initial infection was known, we were able to show that P. marinus does have significant negative effects on oyster reproduction, measurable primarily during gametogenesis, rather than at spawning.

Recovery and Decline of Lake Whitefish in U.S. Waters of Eastern Lake Ontario, 1980-2001

... predation on young-of-the-year (YOY) whitefish by the exotic rainbow smelt (Osmerus mordax, h... more ... predation on young-of-the-year (YOY) whitefish by the exotic rainbow smelt (Osmerus mordax, hereafter, smelt)(Warner and Fenderson 1963; Bergstedt 1983; Evans and Loftus 1987), and perhaps degradation of water quality (Christie 1973; Hoyle et al., 2003; Owens et al ...

Journal of Advanced Research, 2015

Reference intervals for select hematologic and plasma biochemical analytes of wild Lake Sturgeon ( Acipenser fulvescens ) from the St. Lawrence River in New York

Veterinary Clinical Pathology, 2013

Lake Sturgeon (Acipenser fulvescens) is a long-lived freshwater fish distributed throughout the G... more Lake Sturgeon (Acipenser fulvescens) is a long-lived freshwater fish distributed throughout the Great Lakes region and is a threatened species in New York State. The species' unique life cycle makes it useful as an indicator of ecosystem health, and efforts to repatriate Lake Sturgeon to their historic range are underway. However, comprehensive hematologic and biochemical reference intervals that would be valuable for assessing the health status of individual animals have not been reported. The objective of this study was to determine normal hematologic and plasma biochemical reference intervals for healthy wild Lake Sturgeon. Blood samples were collected from 52 wild Lake Sturgeon caught in gill nets in the St. Lawrence River. Heparinized whole blood and plasma samples were analyzed using standard techniques. Reference intervals were calculated using the robust method following elimination of outliers and Box-Cox transformation of data. Hematologic reference intervals were as follows: PCV 17-38%, estimated WBC count 2740-23,150/μL, neutrophils 193-6121/μL, eosinophils 0-558/μL, other granulocytes/heterophils 0-488/μL, lymphocytes 1447-14,044/μL, and monocytes 55-1684/μL. Plasma biochemical reference intervals were as follows: aspartate aminotransferase 333-1746 U/L, calcium 1.85-2.80 mmol/L, chloride 95-123 mmol/L, creatine kinase 776-35,536 U/L, glucose 2.94-14.76 mmol/L, glutamate dehydrogenase 6-30 U/L, phosphate 2.03-5.81 mmol/L, potassium 2.34-4.24 mmol/L, sodium 122.9-151.1 mmol/L, total protein 2.0-4.4 g/dL, triglycerides 1.07-5.12 mmol/L, and uric acid 1-251 μmol/L. Reference intervals reported here will be useful for health assessment of wild and repatriated Lake Sturgeon.

Transactions of the American Fisheries Society, 2007

Populations of American eel Anguilla rostrata along the eastern coast of North America have decli... more Populations of American eel Anguilla rostrata along the eastern coast of North America have declined drastically for largely unknown reasons. We examined the population dynamics of American eels in six tributaries of the Hudson River, New York, to quantify their distribution and the impacts of anthropogenic stressors. With up to 155 American eels per 100 m 2 , tributary densities are greater than those within the main stem of the Hudson River and are among the highest reported anywhere. The predominance of small American eels (,200 mm) and wide range of ages (from young-of-year glass eels to 24-year-old yellow eels) suggest that tributaries are an important nursery area for immature American eels. However, upstream of natural and artificial barriers, American eel densities were reduced by at least a factor of 10 and condition, as measured by mass, was significantly lower. Significantly lower American eel condition was also found with increasing riparian urbanization. Density-dependent growth limitations below barriers are suggested by increased growth rates above the first tributary barrier. We suggest that (1) tributaries are important habitat for the conservation of American eels and (2) mitigation of anthropogenic stressors is vital for complete utilization of available habitat and conservation of the species.

North American Journal of Fisheries Management, 2010

Walleyes Sander vitreus are stocked into Owasco Lake, New York, to provide a sport fishery, but t... more Walleyes Sander vitreus are stocked into Owasco Lake, New York, to provide a sport fishery, but the population must be sustained by annual hatchery supplementation despite the presence of appropriate habitat. Therefore, we evaluated walleye spawning success in Dutch Hollow Brook, a tributary of Owasco Lake, to determine whether early survival limited recruitment. Spawning success during spring 2006 and 2007 was evaluated by estimating egg densities from samples collected in the lower 725 m of the stream. Environmental variables were also recorded to characterize the selected spawning habitat. Drift nets were set downstream of the spawning section to assess egg survival and larval drift. We estimated that 162,596 larvae hatched in 2006. For 2007, we estimated that 360,026 eggs were deposited, with a hatch of 127,500 larvae and hatching success of 35.4%. Egg density was significantly correlated to percent cover, substrate type, and depth : velocity ratio. Two sections had significantly higher egg deposition than other areas. Adult spawning walleyes selected shallow, slow habitats with some cover and gravel substrate in the accessible reaches of Dutch Hollow Brook. Our results show that walleyes found suitable spawning habitat in Dutch Hollow Brook and that egg and larval development does not appear to limit natural reproduction.

Marine Biology, 1998

We analyzed a data set collected over 15 yr, containing growth data from strains of eastern oyste... more We analyzed a data set collected over 15 yr, containing growth data from strains of eastern oysters, Crassostrea virginica (Gmelin, 1791), initiated from parent populations in Long Island Sound, Delaware Bay, and lower Chesapeake Bay. The long-term growth data proved to be a powerful tool for examining patterns of growth dierentiation among separated populations of C. virginica. The oyster strains had been grown in a common environment in lower Delaware Bay for up to seven generations. We found that the oyster strains with origins in Long Island Sound were signi®cantly larger over several generations than oyster strains from Delaware Bay and Chesapeake Bay. Chesapeake Bay oyster strains were larger than Delaware Bay oyster strains at 1.5 yr old, but Delaware Bay oysters were larger at 2.5 yr. Year-to-year variation in environmental conditions had a strong signi®cant eect on absolute oyster size and the relative sizes of the oyster strains. Persistent dierences between oyster strains from dierent origins over several generations support a hypothesis that these estuarine populations have experienced long-term genetically-based population dierentiation. This result is consistent with hypotheses of population dierentiation of oysters based on observations of local reproductive timing.

Comparison of Select Hematology and Serum Chemistry Analtyes Between Wild-Caught and Aquarium-Housed Lake Sturgeon ( Acipenser Fulvescens )

Journal of Zoo and Wildlife Medicine, 2013

Hematology and serum chemistry analytes were compared between wild-caught and aquarium-housed lak... more Hematology and serum chemistry analytes were compared between wild-caught and aquarium-housed lake sturgeon (Acipenser fulvescens) to potentially improve understanding of medical issues in lake sturgeon. Blood samples were taken from 30 lake sturgeon exhibited in 11 institutions in the United States and from 23 experimentally stocked lake sturgeon caught in gill nets in the lower Genesee River in Rochester, New York, USA. For hematology, only segmented neutrophil count was significantly different, with wild-caught fish having a higher number of circulating neutrophils. For clinical chemistry analytes, chloride, uric acid, calcium, phosphate, glucose, aspartate aminotransferase, triglycerides, and creatine kinase were significantly different between the two cohorts. These differences are likely not clinically significant and are attributable to handling stress, variability in environmental parameters, or differences in nutritional status. This is the first report of hematology and serum chemistry values in aquarium-housed lake sturgeon and provides useful reference intervals for clinicians.

Diel variation of intertidal foraging by Cancer productus L. in British Columbia

Journal of Natural History, 1989

... removed from the holding tanks, carapace widths measured, the water allowed to drain from the... more ... removed from the holding tanks, carapace widths measured, the water allowed to drain from the outer shell and gill cavities, and ... Discussion Previous studies (Prasad and Tampi, 1951; Cleaver, 1949; Knudsen, 1964; Haefner, 1976, 1977) report segregation of sizes in portunid ...

Journal of Molluscan Studies, 1996

The moUuscan radula is a dynamic organ, both m terms of its use and production. New rows of teeth... more The moUuscan radula is a dynamic organ, both m terms of its use and production. New rows of teeth are constantly produced at the posterior end of the radula, while older, worn teeth are shed anteriorly, producing a dynamic equilibrium. We used a coldshock to mark the radular ribbon and measure tooth row production rates in two gastropod species, Lacuna vmcta (Montagu) and L. vanegata Carpenter. We found that the average tooth row production rate at 10-ll°C did not differ between these two species, and was 2.94 (SE = 0.002) rows per day for Lacuna vmcta and 2.97 (SE = 0 002) for L. vanegata Inter-individual variability in production rate was very low, and was correlated with shell length, smaller individuals had slightly higher production rates. The total length of the radular nbbon varied greatly among individuals, ranging from 47 to 94 (2.57 to 5.68 mm) rows in L vincta and 53 to 99 rows (2.80 to 7.14 mm) in L vanegata, and was only somewhat correlated with the length of the shelL This great variability will result in large differences among individuals in the time it takes to replace the radula totally, from 14.96 to 35.44 days in L vincta and from 17 43 to 39 69 days in L. vanegata.

Journal of Great Lakes Research, 2007

Little is known about the ecology of round goby (Neogobius melanostomus), an invasive benthic fis... more Little is known about the ecology of round goby (Neogobius melanostomus), an invasive benthic fish, in the profundal zone of the Great Lakes. In April 2002April -2005 we caught increasing numbers of round gobies with a bottom trawl in the 45-150 m depth range of southwestern Lake Ontario. In 2005, we examined gut contents of 30 round gobies from each of three depths, 55, 95, and 130 m, and qualitatively compared gut contents with density of benthic invertebrates determined by Ponar grabs. Round goby guts contained mostly Dreissena spp. and opposum shrimp, Mysis relicta (Mysis); the frequency of occurrence of dreissenids in guts decreased with depth, whereas the frequency of occurrence of Mysis in guts increased with depth. Abundance of these invertebrates in the environment followed the same pattern, although dreissenids of optimum edible size (3-12 mm) were still abundant (1,373/m 2 ) at 130 m, where round gobies primarily consumed Mysis, suggesting that round gobies may switch from dreissenids to more profitable prey when it is available. Other food items were ostracods and fish, with ostracods generally eaten by smaller round gobies and fish eaten by larger round gobies. Occurrence and increasing abundance of round gobies in the profundal zone and predation on Mysis by round goby could have far-reaching consequences for the Lake Ontario fish community.

Journal of Great Lakes Research, 2006

High-resolution seismic reflection profiles, side-scan sonar profiles, and surface sediment analy... more High-resolution seismic reflection profiles, side-scan sonar profiles, and surface sediment analyses for grain size (% sand, silt & clay), total organic carbon content, and carbonate content along shore-perpendicular transects offshore of Olcott and Rochester in Lake Ontario were utilized to investigate cm-thick sands or absence of deepwater postglacial sediments in water depths of 130 to 165 m. These deepwater sands were observed as each transect approached and occupied the "sills," identified by earlier researchers, between the three deepest basins of the lake. The results reveal thin (0 to 5-cm) postglacial sediments, lake floor lineations, and sand-rich, organic, and carbonate poor sediments at the deepwater sites (> 130 m) along both transects at depths significantly below wave base, epilimnetic currents, and internal wave activity. These sediments are anomalous compared to shallower sediments observed in this study and deeper sediments reported by earlier research, and are interpreted to indicate winnowing and resuspension of the postglacial muds. We hypothesize that the mid-lake confluence of the two-gyre surface current system set up by strong storm events extends down to the lake floor when the lake is isothermal, and resuspends and winnows lake floor sediment at these locations. Furthermore, we believe that sedimentation is more likely to be influenced by bottom currents at these at these sites than in the deeper basins because these sites are located on bathymetric highs between deeper depositional basins of the lake, and the bathymetric constriction may intensify any bottom current activity at these sites.

Interactions between invasive round gobies ( Neogobius melanostomus ) and fantail darters ( Etheostoma flabellare ) in a tributary of the St. Lawrence River, New York, USA

Journal of Freshwater Ecology, 2013

ABSTRACT The initial, rapid expansion of the invasive round goby (Neogobius melanostomus) through... more ABSTRACT The initial, rapid expansion of the invasive round goby (Neogobius melanostomus) throughout the Great Lakes drainage was largely confined to lentic systems. We recently observed round gobies ascending two tributaries of the St. Lawrence River. The expansion of gobies into small lotic environments may place ecologically similar species at risk. Fantail darter (Etheostoma flabellare) is one of the several benthic species of the New York Great Lakes drainages that are threatened by round goby invasion. We examined the habitat use and diet composition of fantail darters and round gobies in Mullet Creek, a third-order tributary of the St. Lawrence River, NY, USA. The objectives of this study were to determine the degree of habitat and diet overlap between fantail darters and round gobies in a tributary of the St. Lawrence River. Gobies and darters co-occurred at 22% of capture sites. Of the four habitat variables examined (cover, depth, substrate and velocity), only depth use was significantly different with gobies using deeper habitats than darters. Among the two species and size classes sampled (large vs. small), large darters had the most restricted habitat use requirements. There was variation in round goby and darter diet composition, but only moderate diet overlap occurred between fantail darters and round gobies (Cλ = 0.43). Conditions in Mullet Creek were appropriate for the evaluation of possible spatial and dietary competition between round goby and native darters. Early detection and management of round goby invasions is critical to maintaining ecological integrity of lotic ecosystems in the St. Lawrence Valley.

Fall diel diet composition of American eel ( Anguilla rostrata ) in a tributary of the Hudson River, New York, USA

Journal of Freshwater Ecology, 2013

ABSTRACT American eel (Anguilla rostrata), a once common species, is now in decline throughout mu... more ABSTRACT American eel (Anguilla rostrata), a once common species, is now in decline throughout much of its native range in North America. There is little information on the role of American eel in river food webs. A better understanding of the diet and ecological role of American eel will help in the conservation of this important species. During autumn 2009, eel and aquatic invertebrate samples were collected from Hannacroix Creek, a tributary of the Hudson River, in Albany and Greene counties, New York, USA. Eel diet was analyzed by the eel size and time period (day or night). A high proportion of eel stomachs were empty (73%). Eel diets varied among size classes and day and night feeding periods (p = 0.001). Diet overlap was significant between small and medium eels caught both during the day (α = 0.71) and at night (α = 0.84). Nocturnal diet and nocturnal invertebrate samples were similar (α = 0.65), indicating a preference for bottom feeding during the night. Mayfly nymphs were the major prey consumed in each period by all size classes. Among eels that fed, night-feeding eels had the greatest stomach weight (as a percent of total body weight). The swim-bladder parasite, Anguillicoloides crassus, was also observed in eels of all size classes with nearly 50% afflicted.

Effect of Algal Epiphytes on the Mussel Mytilus Californianus

Ecology, 1991

... Vance (1978) found that epibionts on the bivalve Chama pellucida de-creased the probability t... more ... Vance (1978) found that epibionts on the bivalve Chama pellucida de-creased the probability that the host would be detected by ... The frequencies of survivorship among treatment groups were analyzed using chi-square goodness-of-fit tests applied to a hierarchical series of ...

Shifts in the Diets of Slimy Sculpin ( Cottus cognatus ) and Lake Whitefish ( Coregonus clupeaformis ) in Lake Ontario Following the Collapse of the Burrowing Amphipod Diporeia

Aquatic Ecosystem Health & Management, 2003

ABSTRACT

The American Midland Naturalist, 2011

North American Journal of Aquaculture, 2014

Optimal fish husbandry to reduce the risk of disease is particularly important when using wild fi... more Optimal fish husbandry to reduce the risk of disease is particularly important when using wild fish as the source for gametes. The propagation and reestablishment of Lake Sturgeon Acipenser fulvescens in New York waters to become a viable self-sustaining population is considered a high priority by managers. While standard hatchery egg disinfection practices have been used to prevent the transmission of diseases, data on the bacterial loads present on egg surfaces following iodine disinfection is lacking. Our study investigated the bacteria present on the outer surface of Lake Sturgeon eggs and the effectiveness of an iodine disinfection treatment in eliminating bacteria that could pose a threat to egg survival and cause hatchery disease outbreaks. During the springs of 2011-2013, 12 to 41 different species of bacteria were recovered from the outer egg surfaces prior to an iodine treatment; Aeromonas, Pseudomonas, Shewanella, and Chryseobacterium were the most common genera identified. Cohort eggs treated using the standard protocol of a single treatment of 50 mg/L iodine for 30 min resulted in an average of 57.8% reduction in bacterial CFU/g. While this is a significant reduction, bacteria were not completely eliminated and hatchery managers should be aware that pathogens could remain on Lake Sturgeon eggs following the standard iodine disinfection treatment.

Spread of released Lake Sturgeon: Oswego River basin NY

As part of an ongoing program to restore lake sturgeon (Acipenser fulvescens) in New York, hatche... more As part of an ongoing program to restore lake sturgeon (Acipenser fulvescens) in New York, hatchery-produced juveniles have been stocked into Oneida (8,127) and Cayuga (3,752) lakes, 1995-2004. Release of juveniles as a restoration strategy assumes movement into available suitable habitat. This part of the New York Canal system consists largely of a highly altered barge canal, with the majority habitat consisting of relatively homogenous depths, substrates maintained by regular dredging, and somewhat degraded water quality. Migration of these fish into the Seneca and Oswego Rivers ( Oswego and Erie Canals) is documented. Measurable local populations appear to be developing in the system upstream and downstream of barriers (lock/dam complexes). The 2009 average size in the Seneca River was 1.21 m and 9.03 kg. In the Oswego River it was 1.3 m and 11.94 kg. The sizes and size distributions of these relatively young fish are contrasted with that of similar age sturgeon in other systems....

Growth differences in oysters, Crassostrea virginica, from different estuaries

Journal of Shellfish Research

The protistan parasite Perkinsus marinus has been responsible for high mortality of eastern oyste... more The protistan parasite Perkinsus marinus has been responsible for high mortality of eastern oysters, Crassostrea virginica, along the Atlantic and Gulf Coast of the United States. It also causes sublethal effects, although an impact on reproduction has heretofore been difficult to demonstrate. We examined the effect of P. marinu.s infection on growth, reproduction (as measured by relative gonadal size, and the proportional representation of gametogenic tissue and gametes in the gonad), and condition index of eastern oysters. Oysters of known age and genetic history were exposed to P. marinus infection and sampled at24 week intervals over an 1l-month period during the 1990-1991 epizootic in Delaware Bay. During this time, 50 to l00%o of the oysters had detectable infections and nearly 55%o died. Shell growth rates were inhibited as infections intensified during initial exposure in autumn 1990, but resumed in the spring and remained high, even after infection became heavy. The effect on reproduction varied with the stage of the gametogenic cycle. The relative gonadal size and the proportion of gametogenic tissue in the gonad, as well as the condition index, were most strongly depressed during the spring gametogenic period; however, there was no significant effect of parasite burden when the oysters were reproductively mature and ready to spawn. Data suggested that infected oysters, recovered, produced gametes, and spawned in early summer. Other studies have found inconsistent evidence of sublethal deleterious effects of P. marinu.s on reproduction. By sampling throughout the year and employing oysters of known genetic background, of the same age, reared in a common environment, and for which the timing of initial infection was known, we were able to show that P. marinus does have significant negative effects on oyster reproduction, measurable primarily during gametogenesis, rather than at spawning.

Recovery and Decline of Lake Whitefish in U.S. Waters of Eastern Lake Ontario, 1980-2001

... predation on young-of-the-year (YOY) whitefish by the exotic rainbow smelt (Osmerus mordax, h... more ... predation on young-of-the-year (YOY) whitefish by the exotic rainbow smelt (Osmerus mordax, hereafter, smelt)(Warner and Fenderson 1963; Bergstedt 1983; Evans and Loftus 1987), and perhaps degradation of water quality (Christie 1973; Hoyle et al., 2003; Owens et al ...

Journal of Advanced Research, 2015

Reference intervals for select hematologic and plasma biochemical analytes of wild Lake Sturgeon ( Acipenser fulvescens ) from the St. Lawrence River in New York

Veterinary Clinical Pathology, 2013

Lake Sturgeon (Acipenser fulvescens) is a long-lived freshwater fish distributed throughout the G... more Lake Sturgeon (Acipenser fulvescens) is a long-lived freshwater fish distributed throughout the Great Lakes region and is a threatened species in New York State. The species' unique life cycle makes it useful as an indicator of ecosystem health, and efforts to repatriate Lake Sturgeon to their historic range are underway. However, comprehensive hematologic and biochemical reference intervals that would be valuable for assessing the health status of individual animals have not been reported. The objective of this study was to determine normal hematologic and plasma biochemical reference intervals for healthy wild Lake Sturgeon. Blood samples were collected from 52 wild Lake Sturgeon caught in gill nets in the St. Lawrence River. Heparinized whole blood and plasma samples were analyzed using standard techniques. Reference intervals were calculated using the robust method following elimination of outliers and Box-Cox transformation of data. Hematologic reference intervals were as follows: PCV 17-38%, estimated WBC count 2740-23,150/μL, neutrophils 193-6121/μL, eosinophils 0-558/μL, other granulocytes/heterophils 0-488/μL, lymphocytes 1447-14,044/μL, and monocytes 55-1684/μL. Plasma biochemical reference intervals were as follows: aspartate aminotransferase 333-1746 U/L, calcium 1.85-2.80 mmol/L, chloride 95-123 mmol/L, creatine kinase 776-35,536 U/L, glucose 2.94-14.76 mmol/L, glutamate dehydrogenase 6-30 U/L, phosphate 2.03-5.81 mmol/L, potassium 2.34-4.24 mmol/L, sodium 122.9-151.1 mmol/L, total protein 2.0-4.4 g/dL, triglycerides 1.07-5.12 mmol/L, and uric acid 1-251 μmol/L. Reference intervals reported here will be useful for health assessment of wild and repatriated Lake Sturgeon.

Transactions of the American Fisheries Society, 2007

Populations of American eel Anguilla rostrata along the eastern coast of North America have decli... more Populations of American eel Anguilla rostrata along the eastern coast of North America have declined drastically for largely unknown reasons. We examined the population dynamics of American eels in six tributaries of the Hudson River, New York, to quantify their distribution and the impacts of anthropogenic stressors. With up to 155 American eels per 100 m 2 , tributary densities are greater than those within the main stem of the Hudson River and are among the highest reported anywhere. The predominance of small American eels (,200 mm) and wide range of ages (from young-of-year glass eels to 24-year-old yellow eels) suggest that tributaries are an important nursery area for immature American eels. However, upstream of natural and artificial barriers, American eel densities were reduced by at least a factor of 10 and condition, as measured by mass, was significantly lower. Significantly lower American eel condition was also found with increasing riparian urbanization. Density-dependent growth limitations below barriers are suggested by increased growth rates above the first tributary barrier. We suggest that (1) tributaries are important habitat for the conservation of American eels and (2) mitigation of anthropogenic stressors is vital for complete utilization of available habitat and conservation of the species.

North American Journal of Fisheries Management, 2010

Walleyes Sander vitreus are stocked into Owasco Lake, New York, to provide a sport fishery, but t... more Walleyes Sander vitreus are stocked into Owasco Lake, New York, to provide a sport fishery, but the population must be sustained by annual hatchery supplementation despite the presence of appropriate habitat. Therefore, we evaluated walleye spawning success in Dutch Hollow Brook, a tributary of Owasco Lake, to determine whether early survival limited recruitment. Spawning success during spring 2006 and 2007 was evaluated by estimating egg densities from samples collected in the lower 725 m of the stream. Environmental variables were also recorded to characterize the selected spawning habitat. Drift nets were set downstream of the spawning section to assess egg survival and larval drift. We estimated that 162,596 larvae hatched in 2006. For 2007, we estimated that 360,026 eggs were deposited, with a hatch of 127,500 larvae and hatching success of 35.4%. Egg density was significantly correlated to percent cover, substrate type, and depth : velocity ratio. Two sections had significantly higher egg deposition than other areas. Adult spawning walleyes selected shallow, slow habitats with some cover and gravel substrate in the accessible reaches of Dutch Hollow Brook. Our results show that walleyes found suitable spawning habitat in Dutch Hollow Brook and that egg and larval development does not appear to limit natural reproduction.

Marine Biology, 1998

We analyzed a data set collected over 15 yr, containing growth data from strains of eastern oyste... more We analyzed a data set collected over 15 yr, containing growth data from strains of eastern oysters, Crassostrea virginica (Gmelin, 1791), initiated from parent populations in Long Island Sound, Delaware Bay, and lower Chesapeake Bay. The long-term growth data proved to be a powerful tool for examining patterns of growth dierentiation among separated populations of C. virginica. The oyster strains had been grown in a common environment in lower Delaware Bay for up to seven generations. We found that the oyster strains with origins in Long Island Sound were signi®cantly larger over several generations than oyster strains from Delaware Bay and Chesapeake Bay. Chesapeake Bay oyster strains were larger than Delaware Bay oyster strains at 1.5 yr old, but Delaware Bay oysters were larger at 2.5 yr. Year-to-year variation in environmental conditions had a strong signi®cant eect on absolute oyster size and the relative sizes of the oyster strains. Persistent dierences between oyster strains from dierent origins over several generations support a hypothesis that these estuarine populations have experienced long-term genetically-based population dierentiation. This result is consistent with hypotheses of population dierentiation of oysters based on observations of local reproductive timing.

Comparison of Select Hematology and Serum Chemistry Analtyes Between Wild-Caught and Aquarium-Housed Lake Sturgeon ( Acipenser Fulvescens )

Journal of Zoo and Wildlife Medicine, 2013

Hematology and serum chemistry analytes were compared between wild-caught and aquarium-housed lak... more Hematology and serum chemistry analytes were compared between wild-caught and aquarium-housed lake sturgeon (Acipenser fulvescens) to potentially improve understanding of medical issues in lake sturgeon. Blood samples were taken from 30 lake sturgeon exhibited in 11 institutions in the United States and from 23 experimentally stocked lake sturgeon caught in gill nets in the lower Genesee River in Rochester, New York, USA. For hematology, only segmented neutrophil count was significantly different, with wild-caught fish having a higher number of circulating neutrophils. For clinical chemistry analytes, chloride, uric acid, calcium, phosphate, glucose, aspartate aminotransferase, triglycerides, and creatine kinase were significantly different between the two cohorts. These differences are likely not clinically significant and are attributable to handling stress, variability in environmental parameters, or differences in nutritional status. This is the first report of hematology and serum chemistry values in aquarium-housed lake sturgeon and provides useful reference intervals for clinicians.

Diel variation of intertidal foraging by Cancer productus L. in British Columbia

Journal of Natural History, 1989

... removed from the holding tanks, carapace widths measured, the water allowed to drain from the... more ... removed from the holding tanks, carapace widths measured, the water allowed to drain from the outer shell and gill cavities, and ... Discussion Previous studies (Prasad and Tampi, 1951; Cleaver, 1949; Knudsen, 1964; Haefner, 1976, 1977) report segregation of sizes in portunid ...

Journal of Molluscan Studies, 1996

The moUuscan radula is a dynamic organ, both m terms of its use and production. New rows of teeth... more The moUuscan radula is a dynamic organ, both m terms of its use and production. New rows of teeth are constantly produced at the posterior end of the radula, while older, worn teeth are shed anteriorly, producing a dynamic equilibrium. We used a coldshock to mark the radular ribbon and measure tooth row production rates in two gastropod species, Lacuna vmcta (Montagu) and L. vanegata Carpenter. We found that the average tooth row production rate at 10-ll°C did not differ between these two species, and was 2.94 (SE = 0.002) rows per day for Lacuna vmcta and 2.97 (SE = 0 002) for L. vanegata Inter-individual variability in production rate was very low, and was correlated with shell length, smaller individuals had slightly higher production rates. The total length of the radular nbbon varied greatly among individuals, ranging from 47 to 94 (2.57 to 5.68 mm) rows in L vincta and 53 to 99 rows (2.80 to 7.14 mm) in L vanegata, and was only somewhat correlated with the length of the shelL This great variability will result in large differences among individuals in the time it takes to replace the radula totally, from 14.96 to 35.44 days in L vincta and from 17 43 to 39 69 days in L. vanegata.

Journal of Great Lakes Research, 2007

Little is known about the ecology of round goby (Neogobius melanostomus), an invasive benthic fis... more Little is known about the ecology of round goby (Neogobius melanostomus), an invasive benthic fish, in the profundal zone of the Great Lakes. In April 2002April -2005 we caught increasing numbers of round gobies with a bottom trawl in the 45-150 m depth range of southwestern Lake Ontario. In 2005, we examined gut contents of 30 round gobies from each of three depths, 55, 95, and 130 m, and qualitatively compared gut contents with density of benthic invertebrates determined by Ponar grabs. Round goby guts contained mostly Dreissena spp. and opposum shrimp, Mysis relicta (Mysis); the frequency of occurrence of dreissenids in guts decreased with depth, whereas the frequency of occurrence of Mysis in guts increased with depth. Abundance of these invertebrates in the environment followed the same pattern, although dreissenids of optimum edible size (3-12 mm) were still abundant (1,373/m 2 ) at 130 m, where round gobies primarily consumed Mysis, suggesting that round gobies may switch from dreissenids to more profitable prey when it is available. Other food items were ostracods and fish, with ostracods generally eaten by smaller round gobies and fish eaten by larger round gobies. Occurrence and increasing abundance of round gobies in the profundal zone and predation on Mysis by round goby could have far-reaching consequences for the Lake Ontario fish community.

Journal of Great Lakes Research, 2006

High-resolution seismic reflection profiles, side-scan sonar profiles, and surface sediment analy... more High-resolution seismic reflection profiles, side-scan sonar profiles, and surface sediment analyses for grain size (% sand, silt & clay), total organic carbon content, and carbonate content along shore-perpendicular transects offshore of Olcott and Rochester in Lake Ontario were utilized to investigate cm-thick sands or absence of deepwater postglacial sediments in water depths of 130 to 165 m. These deepwater sands were observed as each transect approached and occupied the "sills," identified by earlier researchers, between the three deepest basins of the lake. The results reveal thin (0 to 5-cm) postglacial sediments, lake floor lineations, and sand-rich, organic, and carbonate poor sediments at the deepwater sites (> 130 m) along both transects at depths significantly below wave base, epilimnetic currents, and internal wave activity. These sediments are anomalous compared to shallower sediments observed in this study and deeper sediments reported by earlier research, and are interpreted to indicate winnowing and resuspension of the postglacial muds. We hypothesize that the mid-lake confluence of the two-gyre surface current system set up by strong storm events extends down to the lake floor when the lake is isothermal, and resuspends and winnows lake floor sediment at these locations. Furthermore, we believe that sedimentation is more likely to be influenced by bottom currents at these at these sites than in the deeper basins because these sites are located on bathymetric highs between deeper depositional basins of the lake, and the bathymetric constriction may intensify any bottom current activity at these sites.

Interactions between invasive round gobies ( Neogobius melanostomus ) and fantail darters ( Etheostoma flabellare ) in a tributary of the St. Lawrence River, New York, USA

Journal of Freshwater Ecology, 2013

ABSTRACT The initial, rapid expansion of the invasive round goby (Neogobius melanostomus) through... more ABSTRACT The initial, rapid expansion of the invasive round goby (Neogobius melanostomus) throughout the Great Lakes drainage was largely confined to lentic systems. We recently observed round gobies ascending two tributaries of the St. Lawrence River. The expansion of gobies into small lotic environments may place ecologically similar species at risk. Fantail darter (Etheostoma flabellare) is one of the several benthic species of the New York Great Lakes drainages that are threatened by round goby invasion. We examined the habitat use and diet composition of fantail darters and round gobies in Mullet Creek, a third-order tributary of the St. Lawrence River, NY, USA. The objectives of this study were to determine the degree of habitat and diet overlap between fantail darters and round gobies in a tributary of the St. Lawrence River. Gobies and darters co-occurred at 22% of capture sites. Of the four habitat variables examined (cover, depth, substrate and velocity), only depth use was significantly different with gobies using deeper habitats than darters. Among the two species and size classes sampled (large vs. small), large darters had the most restricted habitat use requirements. There was variation in round goby and darter diet composition, but only moderate diet overlap occurred between fantail darters and round gobies (Cλ = 0.43). Conditions in Mullet Creek were appropriate for the evaluation of possible spatial and dietary competition between round goby and native darters. Early detection and management of round goby invasions is critical to maintaining ecological integrity of lotic ecosystems in the St. Lawrence Valley.

Fall diel diet composition of American eel ( Anguilla rostrata ) in a tributary of the Hudson River, New York, USA

Journal of Freshwater Ecology, 2013

ABSTRACT American eel (Anguilla rostrata), a once common species, is now in decline throughout mu... more ABSTRACT American eel (Anguilla rostrata), a once common species, is now in decline throughout much of its native range in North America. There is little information on the role of American eel in river food webs. A better understanding of the diet and ecological role of American eel will help in the conservation of this important species. During autumn 2009, eel and aquatic invertebrate samples were collected from Hannacroix Creek, a tributary of the Hudson River, in Albany and Greene counties, New York, USA. Eel diet was analyzed by the eel size and time period (day or night). A high proportion of eel stomachs were empty (73%). Eel diets varied among size classes and day and night feeding periods (p = 0.001). Diet overlap was significant between small and medium eels caught both during the day (α = 0.71) and at night (α = 0.84). Nocturnal diet and nocturnal invertebrate samples were similar (α = 0.65), indicating a preference for bottom feeding during the night. Mayfly nymphs were the major prey consumed in each period by all size classes. Among eels that fed, night-feeding eels had the greatest stomach weight (as a percent of total body weight). The swim-bladder parasite, Anguillicoloides crassus, was also observed in eels of all size classes with nearly 50% afflicted.

Effect of Algal Epiphytes on the Mussel Mytilus Californianus

Ecology, 1991

... Vance (1978) found that epibionts on the bivalve Chama pellucida de-creased the probability t... more ... Vance (1978) found that epibionts on the bivalve Chama pellucida de-creased the probability that the host would be detected by ... The frequencies of survivorship among treatment groups were analyzed using chi-square goodness-of-fit tests applied to a hierarchical series of ...

Shifts in the Diets of Slimy Sculpin ( Cottus cognatus ) and Lake Whitefish ( Coregonus clupeaformis ) in Lake Ontario Following the Collapse of the Burrowing Amphipod Diporeia

Aquatic Ecosystem Health & Management, 2003

ABSTRACT

The American Midland Naturalist, 2011

North American Journal of Aquaculture, 2014

Optimal fish husbandry to reduce the risk of disease is particularly important when using wild fi... more Optimal fish husbandry to reduce the risk of disease is particularly important when using wild fish as the source for gametes. The propagation and reestablishment of Lake Sturgeon Acipenser fulvescens in New York waters to become a viable self-sustaining population is considered a high priority by managers. While standard hatchery egg disinfection practices have been used to prevent the transmission of diseases, data on the bacterial loads present on egg surfaces following iodine disinfection is lacking. Our study investigated the bacteria present on the outer surface of Lake Sturgeon eggs and the effectiveness of an iodine disinfection treatment in eliminating bacteria that could pose a threat to egg survival and cause hatchery disease outbreaks. During the springs of 2011-2013, 12 to 41 different species of bacteria were recovered from the outer egg surfaces prior to an iodine treatment; Aeromonas, Pseudomonas, Shewanella, and Chryseobacterium were the most common genera identified. Cohort eggs treated using the standard protocol of a single treatment of 50 mg/L iodine for 30 min resulted in an average of 57.8% reduction in bacterial CFU/g. While this is a significant reduction, bacteria were not completely eliminated and hatchery managers should be aware that pathogens could remain on Lake Sturgeon eggs following the standard iodine disinfection treatment.

Spread of released Lake Sturgeon: Oswego River basin NY

As part of an ongoing program to restore lake sturgeon (Acipenser fulvescens) in New York, hatche... more As part of an ongoing program to restore lake sturgeon (Acipenser fulvescens) in New York, hatchery-produced juveniles have been stocked into Oneida (8,127) and Cayuga (3,752) lakes, 1995-2004. Release of juveniles as a restoration strategy assumes movement into available suitable habitat. This part of the New York Canal system consists largely of a highly altered barge canal, with the majority habitat consisting of relatively homogenous depths, substrates maintained by regular dredging, and somewhat degraded water quality. Migration of these fish into the Seneca and Oswego Rivers ( Oswego and Erie Canals) is documented. Measurable local populations appear to be developing in the system upstream and downstream of barriers (lock/dam complexes). The 2009 average size in the Seneca River was 1.21 m and 9.03 kg. In the Oswego River it was 1.3 m and 11.94 kg. The sizes and size distributions of these relatively young fish are contrasted with that of similar age sturgeon in other systems....