Timothy A. Whitesel

Larval Metamorphosis of Individual Pacific Lampreys Reared in Captivity

Abstract This study is one of the first to follow individual Pacific lampreys Lampetra tridentata through the process of metamorphosis. Readily observable external changes were described for 13 individual Pacific lampreys undergoing metamorphosis. Changes occurred to the mouth, eyes, and branchial region from July to at least November. During metamorphosis, Pacific lampreys also exhibited asymmetric growth, including an increase in snout depth, that had not previously been reported in the literature. The order of the morphological changes and the patterns of asymmetric growth in the Pacific lamprey closely matched those reported for another Lampetra species, the American brook lamprey L. appendix, but exhibited unexpected variations from those reported in other species of lampreys. Excepting one catastrophic event, under captive rearing conditions 96.4% of the ammocoetes survived and the maximum growth rates of 0.040-0.071 mm/d were within the range of those estimated for ammocoetes rearing naturally in s...

Occupancy and Detection of Larval Pacific Lampreys and Lampetra spp. in a Large River: the Lower Willamette River

Abstract Pacific lampreys Entosphenus tridentatus (formerly Lampetra tridentata) are declining in the Columbia River basin, and the use of large, main-stem river habitats by larvae of this species is unknown. We used a deepwater electrofisher to explore occupancy, detection, and habitat use of larval Pacific lampreys and larval Lampetra spp. in the lower Willamette River, Oregon. We used a generalized random tessellation stratified approach to select sampling quadrats (30 × 30 m) in a random, spatially balanced order. Pacific lampreys, Lampetra spp., and unidentified lampreys were found in the Willamette River; larvae were detected in all areas except the Multnomah Channel. We calculated reach- and quadrat-specific detection probabilities and the amount of sampling effort required for 80% confidence that larval lampreys were in fact absent when they were not detected. Lampreys were detected in a variety of areas (although relatively low numbers were collected), including shallow, nearshore areas; midchann...

Detection and Longevity of Uncured and Cured Visible Implant Elastomer Tags in Larval Pacific Lampreys

Abstract Studies of the biology, ecology, and status of the Pacific lamprey Lampetra tridentata may require effective means of tagging larval Pacific lampreys. However, few assessments of the methods suitable for tagging larval Pacific lampreys have been conducted. We evaluated the performance of visible implant elastomer (VIE) tags in larval Pacific lampreys, specifically testing the effects of elastomer treatment (uncured versus cured VIE) and inspection light source (ambient light versus blue light-emitting diode [LED] flashlight) on tag detection in 40 larvae. Through day 251 after tagging, tag detection was 100% for both uncured and cured VIE tags observed under ambient light and blue LED light. Longevity of uncured VIE tags was assessed in a second cohort of 32 VIE-tagged larval Pacific lampreys over a 2-year captive rearing period. Percent VIE tag detection was 91% for red tags, 90% for orange tags, and 64% for green tags through day 699 after tagging. This study affirms that both uncured and cured...

Detection of Uncured Visible Implant Elastomer Tags in Larval Pacific Lampreys

Abstract Lampreys in the Columbia River basin are a conservation concern, and understanding their status is a priority among managers. Many population assessment techniques depend on the ability to tag fish so that these tags are retained for the duration of the study with minimal effect on survival. There are several methods for tagging small fishes in streams, including passive integrated transponders, coded wire tags, and visible implant elastomer (VIE) tags. Of these, VIE tags have not been extensively tested on larval or juvenile lampreys. We evaluated the performance of uncured VIE tags on ammocoetes of Pacific lampreys Lampetra tridentata in a laboratory experiment to determine tag detection and the influences of color and tag position on detection. Additionally, we examined the effects of transformation (ammocoete to macrophthalmia) on tag detection. Though survival was not specifically tested, 0 of the 84 lampreys died as a result of tagging. Tag detection was 87% after 168 d in lampreys that did...

Characterization of ten microsatellite loci for western brook lamprey Lampetra richardsoni

We describe the isolation and development of ten polymorphic microsatellite loci for western brook lamprey (Lampetra richardsoni). Two to nine alleles were observed per locus in a sample of 35 fish. Gene diversity ranged from 0.000 to 0.792 in six populations. Cross-species amplification was successful as nine, seven and eight loci were polymorphic in Lampetra pacifica, Entosphenus hubbsi, and Entosphenus tridentatus, respectively. These markers will aid in evaluating the population structure of lamprey that are native to western North America.

An Experimental Evaluation of Electrofishing Catchability and Catch Depletion Abundance Estimates of Larval Lampreys in a Wadeable Stream: Use of a Hierarchical Approach

AbstractSome lamprey species are in decline, and assessments of local abundance could benefit research and conservation. In wadeable streams, larval lampreys are collected by using specialized backpack electrofishing techniques, although catchability has not been sufficiently evaluated. We assessed removal models for estimating the local abundance of larval lampreys in experimental net-pen enclosures within a wadeable stream. Known numbers of larvae were seeded at densities of 4–130 larvae/m2 into 1-m2 enclosures that were lined with fine sand and placed into Cedar Creek, Washington (Columbia River basin). Depletion sampling in each enclosure (n = 69) was conducted by three to five electrofishing passes, and abundance was estimated by six removal models that assumed different catchability functions. Catchability averaged 0.28. For the standard removal model, which assumed that catchability varied independently by enclosure but not by pass, the 95% highest posterior density credible intervals (95% HPD-CIs)...

Genetic characteristics of coastal cutthroat trout inhabiting an urban watershed

Watersheds in urban areas are often heavily degraded due to human activity, which can have negative impacts on freshwater fishes. Monitoring the genetic characteristics of urban populations can provide insights into the impact of development on aquatic ecosystems. We performed a genetic analysis of coastal cutthroat trout (Oncorhynchus clarkii clarkii) inhabiting urban tributaries in Portland, OR. By analyzing nuclear microsatellite genotypes, we were able to assess population structure, genetic diversity, and effective population size for six locations across two tributaries on opposite sides of the Willamette River. Genetic diversity was generally equivalent across all sampling locations, although populations from smaller tributaries higher in the stream network had lower levels. Levels of effective population size were low but within expected ranges for small salmonid populations. As anticipated, smaller populations had higher levels of inter-individual relatedness. The primary genetic structure divided populations on opposite sides of the Willamette River, although there was evidence of dispersal between the two groups. Our results suggest that cutthroat trout inhabiting metropolitan areas are not necessarily genetically impoverished and may exhibit characteristics typical of populations in more ‘natural’ environments. Understanding how fish, especially anadromous species, respond to urban environments is essential to evaluating the value of these areas for conservation planning.

Western Pearlshell Mussel Life History in Merrill Creek, Oregon: Reproductive Timing, Growth, and Movement

Abstract Most freshwater mussel species in North America are imperiled. Life history traits of many species have been documented but information regarding western pearlshell mussels (Margaritifera falcata Gould) is scarce. Our goal was to improve understanding of western pearlshell mussel reproduction, growth, and movement. The study area was a 250 m reach in Merrill Creek, Oregon. We examined 1389 mussels for gravidity and examined water samples for glochidia during presumed spawning times over a 4-year period. We tagged 415 mussels for mark-recapture observations for growth and movement. No mussels showed signs of gravidity. However, four mussels near our study transects were observed releasing conglutinates. Glochidia were present from April to mid-June. Glochidia were not detected until maximum daily water temperature had reached 10.0 °C, and were no longer detected once minimum daily water temperature remained above 9.0 °C. There was a negative relation between growth rate and mussel size. Growth rate was not significantly different than 0.0000 mm d-1 for large mussels and 0.0011 mm d-1 for small mussels. For movement, 60% (n = 15) of mussels were recaptured at the same transect as originally marked, 32% (n = 8) were recaptured 3.7–115.6 m downstream and 8% (n = 2) were recaptured 12.0 m upstream. This basic life history information is essential to consider when developing management plans associated with the conservation of western pearlshell mussels and their habitat. Our results indicate they are slow-growing, slow-moving, long-lived, and thus likely slow to adapt to environmental change and respond to habitat perturbations.

Evaluation of Methods to Measure Condition in Pacific Northwest Larval Lampreys

Abstract Pacific lamprey (Entosphenus tridentatus) populations are declining and western brook lamprey (Lampetra richardsoni) status is unknown in the Pacific Northwest. Accurate measures of fish condition are a basic requirement to monitor health and status of fish populations. Fultons condition factor has traditionally been used to assess condition of larval lamprey but alternative field-based and laboratory-based measures have not been assessed. We compared condition factor, body density, and lipid content of sympatric larval Pacific lamprey and western brook lamprey in 2010 and 2011 from two rivers of the Pacific Northwest. Condition factor was higher for Pacific lamprey than it was for western brook lamprey. All measures were variable and correlations among condition indices were weak. Body density and lipid content were higher in western brook lamprey in one year suggesting the possibility of increased energy requirements of metamorphosis to a nontrophic adult stage. The body density technique was onerous and likely has little field-based practicality. Body density and lipid content had a negative relationship as increased lipids leads to a more buoyant and less dense fish. Condition factor did not appear to be a good predictor of lipid content in our study and a suite of complex factors, including lipid dynamics prior to metamorphosis and nutritional resources, may underlie these results. This study provides one of the few empirical datasets on sympatric lampreys with different life history strategies.