bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow-Through Fourier Transform Infrared Sensor for Total Hydrocarbons Determination in Water
Authors: Pérez-Palacios David , Armenta Sergio , Lendl Bernhard
Published: October 2009

A new flow-through Fourier transform infrared (FT-IR) sensor for oil in water analysis based on solid-phase spectroscopy on octadecyl (C18) silica particles has been developed. The C18 non-polar sorbent is placed inside the sensor and is able to retain hydrocarbons from water samples. The system does not require the use of chlorinated solvents, reducing the environmental impact, and the minimal sample handling stages serve to ensure sample integrity whilst reducing exposure of the analyst to any toxic hydrocarbons present within the samples. Fourier transform infrared (FT-IR) spectra were recorded by co-adding 32 scans at a resolution of 4 cm−1 and the band located at 1462 cm−1 due to the CH2 bending was integrated from 1475 to 1450 cm−1 using a baseline correction established between 1485 and 1440 cm−1 using the areas as analytical signal. The technique, which provides a limit of detection (LOD) of 22 mg L−1 and a precision expressed as relative standard deviation (RSD) lower than 5%, is considerably rapid and allows for a high level of automation.
Fishing Mortality in North Carolina's Southern Flounder Fishery: Direct Estimates of Instantaneous Fishing Mortality from a Tag Return Experiment
Authors: Smith William E. , Scharf Frederick S. , Hightower Joseph E.
Published: October 2009

Estimation of harvest rates is often a critical component of fishery stock assessment and management. These assessments are often based on catch-at-age data sets generated over many years, but estimates of instantaneous fishing mortality (F) can also be obtained from a shorter-term tag return study. We conducted a 2-year tag return experiment to generate direct estimates of F for southern flounder Paralichthys lethostigma in a North Carolina estuary. The southern flounder supports lucrative commercial and recreational fisheries within the state and has experienced heavy fishing pressure for more than a decade. During 2005 and 2006, fish were captured and tagged with the assistance of commercial harvesters in the New River estuary. Tag returns were used to generate monthly estimates of F, which demonstrated a clear seasonal pattern that was consistent between years. Several important assumptions of the tag return model were accounted for through the use of double-tagged individuals, the distribution of both high- and standard-reward tags, and the completion of an independent controlled experiment to evaluate mortality related to tagging. Annual estimates of F exceeded the short-term management target in both years. Residual patterns suggest that the estimates may actually have been biased low, possibly due to delayed mixing of tagged fish. Thus, despite recently amended fishery regulations, F in the North Carolina southern flounder gill-net fishery still has the potential to greatly exceed targeted levels, which may delay stock recovery. Tag return studies can provide reliable (and nearly real-time) information about F and natural mortality as long as the experimental design addresses specific assumptions related to tagging-induced mortality, tag shedding, and nonreporting of tags.
Postmortem Length Changes in Six Florida Fish Species Stored on Ice
Authors: Chesnes Thomas C. , Waldner Raymond E. , Krahforst Cecilia S.
Published: October 2009

Representatives of six species of fishes belonging to the families Lutjanidae, Centropomidae, Pomatomidae, Scombridae, Carangidae, and Sciaenidae were stored on ice for 6 h after being euthanatized, in order to assess postmortem length changes. Standard length, fork length (where applicable), total length using the relaxed caudal fin method, and rigor mortis were measured immediately after deaths and at 30 min intervals thereafter. Two species, lane snapper Lutjanus synagris and common snook Centropomus undecimalis, showed an increase in mean total lengths during the first hour after death. Common snook continued to increase in mean total length for the duration of the study, while lane snapper subsequently decreased. Declines in mean standard, fork, and total lengths also were observed in bluefish Pomatomus saltatrix, Spanish mackerel Scomberomorus maculatus, and Florida pompano Trachinotus carolinus. Minimal changes in mean standard and total length were observed for spotted seatrout Cynoscion nebulosus. There was little direct correlation between rigor mortis and length variation for any of the studied species. The observed length changes may have implications for both law enforcement personnel and anglers.
Stock Assessment of Scalloped Hammerheads in the Western North Atlantic Ocean and Gulf of Mexico
Authors: Hayes Christopher G. , Jiao Yan , Cortés Enric
Published: October 2009

The status of the western North Atlantic Ocean population of scalloped hammerheads Sphyrna lewini (Sphyrnidae [hammerhead sharks]) was assessed from 1981 through 2005 by using Schaefer (logistic) and Fox surplus-production models. The population declined rapidly before 1996 but began rebuilding in the late 1990s as fishing pressure decreased. The Akaike information criterion for small sample sizes—a test of goodness of fit for statistical models—indicated that the Fox model provided a slightly better fit to the data. Bootstrapped parameter values showed that in 2005 the probability of the scalloped hammerhead's being overfished was greater than 95% (the population was estimated to be 45% of that which would produce the maximum sustainable yield [MSY]) and a 73% probability that overfishing was occurring (fishing mortality was approximately 129% of that associated with the MSY). The size of this population was estimated to be 17% of what it had been in 1981, that is, it has been depleted by about 83% from the virgin stock size. Monte Carlo simulation predicted that the population had a 58% probability of rebuilding in 10 years if the 2005 catch level (4,135 individuals) were maintained and an 85% probability of rebuilding if the 2005 total catch were halved. Sensitivity analyses showed that the stock assessment results were most sensitive to removing the University of North Carolina longline survey index of relative abundance, the method of weighting indices, and excluding fishery-dependent indices of relative abundance.
Use of a Volunteer Angler Survey for Assessing Length Distribution and Seasonal Catch Trends of Trophy Largemouth Bass
Authors: De Jesus Marcos J. , Magnelia Stephan J. , Bonds C. Craig
Published: October 2009

A volunteer angler survey was conducted from October 2004 to May 2006 at Fayette County Reservoir, Texas, to help determine the seasonal catch trends and length distribution of trophy (≥21 in long) largemouth bass Micropterus salmoides. Although previous Texas Parks and Wildlife creel and electrofishing surveys had collected data on the reservoir's largemouth bass fishery, little information was obtained on trophy bass. Quarterly catch and length distribution data from a volunteer angler survey were compared with data collected concurrently during an agency-staffed creel survey as a means to validate the volunteered data. The costs associated with each survey method were also compared. Anglers voluntarily reported catches of 177 trophy largemouth bass during the 20-month survey period. The length distributions by inch-group 21 in or longer were not significantly different between survey methods, validating the fish lengths reported by volunteers. The quarterly catch trends over a 1-year period were also similar between methods. The monetary costs of the 20-month volunteer survey were 16% those of the 12-month staffed creel survey. Managers should consider similar volunteer surveys on small impoundments when relatively low-cost length distribution and catch trend data are needed for trophy fish. Volunteer data may help justify the cost associated with additional creel surveys when more extensive data are needed. This information can also be used to complement data gathered in previous creel surveys.
A Spatial Model to Assess the Effects of Hydropower Operations on Columbia River Fall Chinook Salmon Spawning Habitat
Authors: Hatten James R. , Tiffan Kenneth F. , Anglin Donald R. , Haeseker Steven L. , Skalicky Joseph J. , Schaller Howard
Published: October 2009

Priest Rapids Dam on the Columbia River produces large daily and hourly streamflow fluctuations throughout the Hanford Reach during the period when fall Chinook salmon Oncorhynchus tshawytscha are selecting spawning habitat, constructing redds, and actively engaged in spawning. Concern over the detrimental effects of these fluctuations prompted us to quantify the effects of variable flows on the amount and persistence of fall Chinook salmon spawning habitat in the Hanford Reach. Specifically, our goal was to develop a management tool capable of quantifying the effects of current and alternative hydrographs on predicted spawning habitat in a spatially explicit manner. Toward this goal, we modeled the water velocities and depths that fall Chinook salmon experienced during the 2004 spawning season, plus what they would probably have experienced under several alternative (i.e., synthetic) hydrographs, using both one- and two-dimensional hydrodynamic models. To estimate spawning habitat under existing or alternative hydrographs, we used cell-based modeling and logistic regression to construct and compare numerous spatial habitat models. We found that fall Chinook salmon were more likely to spawn at locations where velocities were persistently greater than 1 m/s and in areas where fluctuating water velocities were reduced. Simulations of alternative dam operations indicate that the quantity of spawning habitat is expected to increase as streamflow fluctuations are reduced during the spawning season. The spatial habitat models that we developed provide management agencies with a quantitative tool for predicting, in a spatially explicit manner, the effects of different flow regimes on fall Chinook salmon spawning habitat in the Hanford Reach. In addition to characterizing temporally varying habitat conditions, our research describes an analytical approach that could be applied in other highly variable aquatic systems.
Factors Affecting Fish Entrainment into Massive Water Diversions in a Tidal Freshwater Estuary: Can Fish Losses be Managed?
Authors: Grimaldo Lenny F. , Sommer Ted , Van Ark Nick , Jones Gardner , Holland Erika , Moyle Peter B. , Herbold Bruce , Smith Pete
Published: October 2009

We examined factors affecting fish entrainment at California's State Water Project and Central Valley Project, two of the largest water diversions in the world. Combined, these diversions from the upper San Francisco Estuary support a large component of the municipal and agricultural infrastructure for California. However, precipitous declines in the abundance of several estuarine fish species, notably the threatened delta smelt Hypomesus transpacificus, have generated major concern about entrainment as a possible cause of the declines. We examined a 13-year data set of export pumping operations and environmental characteristics to determine factors affecting entrainment (as indexed by salvage at fish screens) and the potential for manipulation of these factors to improve conditions for fish. Entrainment of three migratory pelagic species—delta smelt, longfin smelt Spirinchus thaleichthys, and striped bass Morone saxatilis—was primarily determined by the seasonal occurrence of particular life stages close to the export facilities. We also found that the direction and magnitude of flows through the estuary and to the export facilities were reasonable predictors of pelagic fish entrainment. Entrainment of resident demersal species (prickly sculpin Cottus asper and white catfish Ameiurus catus) and littoral species (Mississippi silverside Menidia audens and largemouth bass Micropterus salmoides) was not explained by diversion flows, although large numbers of individuals from these species were collected. Our study suggests that entrainment of pelagic species can be effectively reduced by manipulating system hydrodynamics.
Evaluating the Reintroduction Potential of Lahontan Cutthroat Trout in Fallen Leaf Lake, California
Authors: Al-Chokhachy Robert , Peacock Mary , Heki Lisa G. , Thiede Gary
Published: October 2009

We evaluated the potential for reintroducing Lahontan cutthroat trout Oncorhynchus clarkii henshawi, a species listed under the Endangered Species Act, into a lacustrine system where the biotic community has changed dramatically since the species' extirpation there. Since 2002, 76,547 Lahontan cutthroat trout have been reintroduced into Fallen Leaf Lake, California; we used creel surveys, diet data, mark–recapture methods, bioenergetics modeling, and netting data across seasons to evaluate the habitat use, growth, and relative abundance of Lahontan cutthroat trout and the abundance, diet, habitat use, and predation by nonnative species. Sampling totals (n = 2) and survey observations (n = 3) indicate low survival and abundance of reintroduced fish and together with creel data indicate the importance of epilimnetic habitats across size-classes. Despite substantial growth, Lahontan cutthroat trout exhibited low condition factor values (average = 0.69). We found substantial predation pressure from a large population of lake trout Salvelinus namaycush (Ṋ = 8,799 fish; 95% confidence interval [CI] = 4,990–16,530 fish); analysis of lake trout diets showed an increase in piscivory and in the percentage of stomachs containing Lahontan cutthroat trout anchor tags with increasing predator size. Overall, we estimated that lake trout consumed over 38% of reintroduced Lahontan cutthroat trout (mean number consumed = 7,736 fish; 95% CI = 4,388–14,534 fish). With bioenergetics modeling, however, we estimated that lake trout consumed considerable amounts of salmonid biomass during this period (mean biomass = 3,137 kg; 95% CI = 1,779–5,893 kg), which greatly exceeded the biomass of Lahontan cutthroat trout reintroduced in 2006. During the stratification period, there was little overlap in habitat use between lake trout and Lahontan cutthroat trout, but overlap was high during the spring and autumn. We found moderate-sized populations of nonnative brown trout Salmo trutta, kokanee O. nerka (lacustrine sockeye salmon), and rainbow trout O. mykiss. Together, our results suggest that Lahontan cutthroat trout have few refugia from direct and indirect negative interactions with nonnative species and that alternative approaches are needed.
Use of Carcass Recovery Data in Evaluating the Spawning Distribution and Timing of Spring Chinook Salmon in the Chiwawa River, Washington
Authors: Murdoch Andrew R. , Pearsons Todd N. , Maitland Travis W.
Published: October 2009

Spawning ground surveys are routinely conducted to assess status and trends for many populations of Pacific salmon Oncorhynchus spp. Biological data from carcasses recovered during spawning ground surveys are used for various stock assessment purposes but may also be useful in comparing the spawning distribution and timing of hatchery- and naturally produced fish. The objective of this study was to measure the distance between redd and carcass locations of spring Chinook salmon O. tshawytscha in the Chiwawa River and assess whether carcass location adequately represents spawning location. We also estimated the redd residence time (d) of hatchery- and naturally produced spring Chinook and compared the spawn timing using both redd and carcass data for hatchery- and natural-origin fish. We determined the redd location, spawn timing, and carcass location of individual hatchery- and naturally produced spring Chinook salmon during spawning ground surveys using passive integrated transponder tags implanted during the adults' migration to the spawning grounds. Differences in mean carcass drift (the distance between redd location and carcass location) were detected between male (4,465 m) and female (150 m) spring Chinook salmon (P < 0.003) but not between hatchery- and naturally produced females (P = 0.32). The mean spawn date and the estimated spawn date derived from carcasses were not significantly different for either hatchery- or natural-origin spring Chinook salmon (P > 0.05). We concluded that the use of carcass data from female spring Chinook salmon to estimate the spawning location and timing is appropriate when surveys are conducted on a consistent weekly schedule throughout the entire spawning period.
Morphological Patterns of Hybridization between Yellowstone Cutthroat Trout and Introduced Rainbow Trout in the South Fork of the Snake River Watershed, Idaho and Wyoming
Authors: Seiler Steven M. , Gunnell Kelly , Ptacek Margaret B. , Keeley Ernest R.
Published: October 2009

Hybridization between native and introduced species is considered a serious threat for many native fish populations. In western North America, native cutthroat trout Oncorhynchus clarkii subspecies are declining dramatically across their ranges; competition and hybridization with nonnative rainbow trout O. mykiss are recognized as key factors in their decline. Presently, identification of cutthroat trout × rainbow trout hybrids is commonly made using molecular genetic markers because morphological differences are thought to be inaccurate. We sampled trout from the South Fork of the Snake River and 10 tributary streams to test for morphological differences that could predict genetic identity of individual Yellowstone cutthroat trout O. clarkii bouvieri, rainbow trout, and their hybrids. We found distinctive body shape differences among the three groups: Yellowstone cutthroat trout and hybrids had larger heads than rainbow trout. Yellowstone cutthroat trout had shallower bodies and caudal peduncles than rainbow trout, whereas hybrids exhibited intermediate body depth and caudal peduncle depth. Using logistic regression with a suite of morphological measurements, we found an overall rate of 92% for correctly classifying trout as Yellowstone cutthroat trout, hybrids, or rainbow trout. Over 99% of Yellowstone cutthroat trout and 80% of rainbow trout were correctly categorized; however, the correct classification rate for hybridized individuals was considerably lower. This study demonstrates that consistent morphological differences exist between Yellowstone cutthroat trout and rainbow trout in the wild, and the degree of introgression accounts for a significant portion of morphological variation in Yellowstone cutthroat trout × rainbow trout hybrids, thus causing difficulty in the use of morphology alone to classify trout.
Seasonal Comparison of Catch Rates and Size Structure Using Three Gear Types to Sample Sturgeon in the Middle Mississippi River
Authors: Phelps Quinton E. , Herzog David P. , Brooks Ronald C. , Barko Valerie A. , Ostendorf David E. , Ridings Joseph W. , Tripp Sara J. , Colombo Robert E. , Garvey James E. , Hrabik Robert A.
Published: October 2009

We evaluated the efficacy of three gears commonly used to sample shovelnose sturgeon Scaphirhynchus platorynchus, pallid sturgeon S. albus, and lake sturgeon Acipenser fulvescens in large rivers. We stratified habitats and randomly sampled sites with trawls, gill nets, and trotlines in the middle Mississippi River from June 2003 through May 2005 (N = 3,476 samples). A total of 3,523 shovelnose sturgeon, 31 pallid sturgeon, and 13 lake sturgeon were captured. When sample sizes were adequate (based on power analysis), we used a mixed analysis of variance (ANOVA) procedure to determine the relative impact of season and gear type on sturgeon catch per unit effort (CPUE). Kolmogorov–Smirnov tests were used to determine whether the length frequency distributions for each species differed among gears. Overall, the power analyses indicated that there were adequate sample sizes for comparing standardized CPUE for shovelnose sturgeon among seasons; however, too few pallid or lake sturgeon were collected to make statistical comparisons. Shovelnose sturgeon catch rates varied among gears and seasons; season and gear type interacted in the ANOVA model. Among gear types, 5.08-cm gill nets produced the highest standardized CPUE, and catch rates were highest during spring. The length frequency distributions of shovelnose sturgeon depended on gear type. Shovelnose sturgeon can be sampled in large rivers using stratified random sampling with this combination of gear. However, pallid sturgeon and lake sturgeon may be too rare to sample with this approach.
Impacts of Commercial Gill-Net Bycatch and Recreational Fishing on a Florida Black Crappie Population
Authors: Dotson Jason R. , Allen Micheal S. , Johnson William E. , Benton John
Published: October 2009

Commercial bycatch can potentially induce high fishing mortality and represents serious concerns for the sustainability of some fisheries. We evaluated the potential population-level impacts of commercial gill-net bycatch and recreational fishing mortality on black crappie Pomoxis nigromaculatus in Lake Dora, Florida. We assessed total black crappie bycatch and the mortality rates of black crappie entangled in gill nets, quantified recreational fishing effort and harvest, and estimated exploitation for the recreational and commercial (bycatch) fisheries. We used an equilibrium age-structured population model to assess potential population-level impacts of bycatch and recreational fishing mortality. Onboard observer data of commercial fishers showed that about 17,000 and 30,000 black crappie were captured in gill nets in 2005 and 2006, respectively. Cage experiments revealed that about 30% and 47% of black crappie captured in gill nets experienced mortality after 72 h in 2005 and 2006, respectively. The recreational fishery exploitation rate was estimated to be 42% based on angler tag returns in 2006, and commercial exploitation via bycatch from commercial gill nets was 15%. The population model suggested that the level of recreational fishing mortality observed in 2006 was probably sustainable but that additional commercial or recreational exploitation would create a risk of recruitment overfishing. The greatest risk for recruitment overfishing via bycatch occurs when other sources of exploitation are also high (e.g., via a recreational fishery).
Effects of Temporary Tributary Use on Escapement Estimates of Adult Fall Chinook Salmon in the Deschutes River, Oregon
Authors: Naughton George P. , Jepson Michael A. , Peery Christopher A. , Brun Christopher V. , Graham Jennifer C.
Published: October 2009

International managers use escapement estimates of the Deschutes River, Oregon, population of fall Chinook salmon Oncorhynchus tshawytscha to forecast abundance and assess population health. Fish are externally marked in the Deschutes River, and a subsample of the marked fish is recovered on the spawning grounds to provide data for estimating escapement. Escapement would be overestimated if some of the marked fish exited the Deschutes River prior to spawning (i.e., used this tributary temporarily). We used mark–recapture and radiotelemetry techniques to calculate (1) the proportion of adult fall Chinook salmon that entered the Deschutes River and subsequently exited the river prior to spawning and (2) the effect of such temporary entrances on spawning ground escapement estimates. We used separate criteria to calculate maximum and minimum temporary tributary use rates, which were then used to adjust the escapement estimates made with external-tag data alone. Over the 3 years of study, the adjusted estimates were approximately 4–29% lower than the unadjusted estimates. We conclude that failure to adjust escapement estimates for temporary tributary use might lead to inflated harvest targets. To partially account for temporary tributary use, the lower 95% confidence limit for an escapement estimate could be used to regulate harvest.
A Preliminary Fishery Quality Index for Portuguese Streams
Authors: Oliveira João M. , Ferreira Maria T. , Morgado Paula , Hughes Robert M. , Teixeira Amílcar , Cortes Rui M. , Bochechas Jorge H.
Published: October 2009

There is a need to quantify the multivariate quality of a recreational fishery at the site scale to better communicate the relative quality among sites to the public and anglers. Borrowing on the general approach of multimetric indices of biotic integrity (IBIs), we developed fishery quality indices (FQIs) from species quality indices (SQIs) based on measures of fish abundance and size structure for northern and central Portuguese streams. Our FQIs showed regional patterns indicating a range in fishery quality. Higher coldwater FQI scores were mostly found in the northwestern (Minho and Lima), northeastern Douro, and northern Tagus basins. Higher warmwater FQI scores occurred in the eastern Tagus basin. The species that contributed the most to warmwater FQI scores were largemouth bass Micropterus salmoides, pumpkinseed Lepomis gibbosus, the cyprinid Luciobarbus bocagei, chubs Squalius carolitertii and S. pyrenaicus, and nases Pseudochondrostoma duriense and P. polylepis. The chubs, nases, and brown trout Salmo trutta contributed the most to coldwater FQI scores. As expected, our indices were correlated with river size and with disturbance at the catchment, segment, and site scales. Regression models for separate coldwater and warmwater FQIs were stronger than those for the individual SQIs and for an all-site FQI. The correlation was positive between the coldwater FQI and a coldwater IBI but negative between the warmwater FQI and warmwater IBIs. The proposed FQIs offer a quantitative approach for assessing relative fishery quality among sites and for making regional assessments given an appropriate study design. The component SQIs and SQI metrics of the FQIs can be disassociated to determine the population and species characteristics most affected by various environmental variables.
Fish Assemblage Relationships with Physical Habitat in Wadeable Iowa Streams
Authors: Rowe David C. , Pierce Clay L. , Wilton Thomas F.
Published: October 2009

Fish assemblages play a key role in stream ecosystems and are influenced by physical habitat. We analyzed fish assemblages and physical habitat at 93 randomly selected sites on second- through fifth-order wadeable Iowa streams to explore fish assemblage relationships with reach-scale physical habitat in this agriculturally dominated landscape. Sites were sampled using DC electrofishing and the wadeable streams physical habitat protocol of the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program. In all, 82 species were collected, with species richness at sites averaging 14. Over 80% of the sites had fish assemblages rated as fair (53%) or poor (32%) based on a fish index of biotic integrity (FIBI). Ordination separated sites from the two major river drainages along an axis of impairment, with sites in the Missouri River drainage exhibiting lower FIBI scores than sites in the Mississippi River drainage. Physical habitat at most sites exhibited fine substrates, eroding banks, and low-gradient, nonmeandering channel and was dominated by glides. Thirty physical habitat variables describing channel morphology, channel cross section and bank morphology, fish cover, human disturbance, large woody debris, relative bed stability, residual pool, riparian vegetation, and substrate differed significantly between sites with FIBI scores rated as poor and those with FIBI scores rated as good or excellent. Eighteen physical habitat variables were significant predictors of fish assemblage metrics and FIBI in multiple linear regression models, with adjusted R2 values ranging from 0.12 to 0.58. Seventy percent of the model coefficients reflected substrate (40%), residual pool (21%), and fish cover (9%) variables. Fish assemblages in wadeable Iowa streams are strongly associated with the quality of physical habitat. Thus, understanding and addressing the determinants of physical habitat are crucial for managing streams in Iowa and other agricultural regions.
Physical Habitat and Fish Assemblage Relationships with Landscape Variables at Multiple Spatial Scales in Wadeable Iowa Streams
Authors: Rowe David C. , Pierce Clay L. , Wilton Thomas F.
Published: October 2009

Landscapes in Iowa and other midwestern states have been profoundly altered by conversion of native prairies to agriculture. We analyzed landscape data collected at multiple spatial scales to explore relationships with reach-scale physical habitat and fish assemblage data from 93 randomly selected sites on second- through fifth-order wadeable Iowa streams. Ordination of sites by physical habitat showed significant gradients of channel shape, habitat complexity, substrate composition, and stream size. Several landscape variables were significantly associated with the physical habitat ordination. Row crop land use was associated with fine substrates and steep bank angles, whereas wetland land cover and greater sinuosity and catchment land area were associated with complex channel and bank morphology and greater residual pool volume, woody debris, and canopy cover. Thirteen landscape variables were significant predictors of physical habitat variables in multiple linear regressions, with adjusted R2 values ranging from 0.07 to 0.74. Inclusion of landscape variables with physical habitat variables in multiple regression models predicting fish assemblage metrics and a fish index of biotic integrity resulted in negligible improvements over models based on only physical habitat variables. Physical habitat in wadeable Iowa streams is strongly associated with landscape characteristics. Results of this study and previous studies suggest that (1) landscape factors directly influence physical habitat, (2) physical habitat directly influences fish assemblages, and (3) the influence of landscape factors on fish assemblages is primarily indirect. Understanding how landscape factors, such as human land use, influence physical habitat and fish assemblages will help managers make more informed decisions for improving Iowa's wadeable streams.
An Ecosystem Perspective on Re-establishing Native Deepwater Fishes in the Laurentian Great Lakes
Authors: Zimmerman Mara S. , Krueger Charles C.
Published: October 2009

Herein we examine scientific questions related to successful re-establishment of native deepwater fish communities in the Laurentian Great Lakes, and we (1) propose a conceptual model for native deepwater fish communities; (2) review current research and identify research hypotheses for lake trout Salvelinus namaycush, pelagic ciscoes Coregonus spp., and sculpins (Cottus spp. and Myoxocephalus spp.); (3) pose research questions emerging at community and ecosystem levels; and (4) identify high-priority research topics related to population re-establishment. The conceptual model is based on a generalized life cycle nested within processes at the population, metapopulation, community, and ecosystem levels. The conceptual model assumes that variation in population abundance is a natural phenomenon and that biodiversity contributes to ecosystem stability. Key research topics related to lake trout re-establishment include understanding recruitment variation over space and time, identifying sources of early life history mortality, determining the level of genetic differentiation among morphotypes and populations, and comparing the life history and ecology of lean lake trout with those of other lake trout morphotypes. Key research topics related to re-establishing deepwater species of cisco include resolving uncertainties in species identifications, understanding processes maintaining distinctiveness among species, understanding processes leading to cyclic and erratic recruitment, and developing effective propagation methods. Key research topics related to re-establishment of sculpin species include comparing spawning ecology and early life history of each species, determining population structure, and evaluating the feasibility of live-transfer methods. Key research topics related to community- and ecosystem-level interactions include understanding large-scale directional influences on community function, expanding current views on ecological succession in large lakes, and determining the evolutionary role of diel vertical migration in phenotypic diversification of deepwater fishes. Finally, we propose that research in four topical areas are most pertinent to re-establishing native deepwater fishes: life history bottlenecks, population and metapopulation dynamics, matching fish phenotypes to stocking sites, and propagation and stocking methods.
Detection and Longevity of Uncured and Cured Visible Implant Elastomer Tags in Larval Pacific Lampreys
Authors: Silver Gregory S. , Luzier Christina W. , Whitesel Timothy A.
Published: October 2009

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 VIE tags can be effectively used to tag larval Pacific lampreys. Tagging with uncured VIE is a convenient and economical alternative to cured VIE tagging, particularly when tagging over protracted periods or small sample sizes.
Genetic Evaluation of a Conservation Hatchery Program for Reintroduction of Sicklefin Redhorse Moxostoma sp. in the Tuckasegee River, North Carolina
Authors: Moyer Gregory R. , Rousey J. D. , Cantrell M. A.
Published: October 2009

Restoration and reintroduction efforts for the sicklefin redhorse Moxostoma sp. have been initiated by state, tribal, and federal agencies owing to the limited geographic distribution of this species and threats associated with the physical alteration of its habitat. A critical component of a successful reintroduction is that the source and recipient populations have similar genetic resources and life history patterns. We used 10 microsatellite loci to estimate and compare indices of genetic diversity between the Little Tennessee River population of wild adults and the hatchery broodstock being used for initial reintroduction efforts. We also compared relatedness values for the broodstock used for restoration efforts. There were no significant differences between hatchery broodstock and wild adults with respect to average gene diversity, but the average number of alleles for each brood year was significantly less than that for wild adults. While this trend persisted when the 2007 and 2008 brood years (combined) were compared with wild adults, the reduction was not significant. Finally, all hatchery crosses were among unrelated individuals. Our results highlight the importance of using genetic information to assist restoration and reintroduction efforts.
Utility of a Probabilistic Sampling Design to Determine Bull Trout Population Status Using Redd Counts in Basins of the Columbia River Plateau
Authors: Jacobs Steven E. , Gaeuman William , Weeber Matt A. , Gunckel Stephanie L. , Starcevich Steven J.
Published: October 2009

Redd counts are commonly used to monitor the current population status, trends in abundance, and distribution of bull trout Salvelinus confluentus. In many cases redd counts are conducted at subjectively selected sites, and there has been limited evaluation of statistical sampling designs. We evaluated the utility of the generalized random tessellation stratified (GRTS) sampling design to determine bull trout population status through redd counts. We tested a sampling effort that would be economically practical to implement on a continuous basis in multiple drainages within the southeastern Washington and Oregon portions of the Columbia River plateau. We evaluated the logistics of a pilot application of the GRTS design, compared GRTS-based estimates of redd abundance with those from census surveys, determined the precision of the GRTS estimates and the associated power for abundance comparisons, and compared the performance of the GRTS design with that of other probability sampling designs through simulation. A target of 50 sites per basin can be sampled by a two-person survey crew multiple times over the spawning season. At that level of effort, the precision of redd abundance estimates ranges from 15% to 35%, depending on the patchiness of the redd distribution and the extent of the target population. These levels of precision are suitable for detecting a 30–70% change in redd abundance. Direct comparisons of GRTS-based estimates with those obtained from a census showed mixed results. However, in a simulation study with three other probability sampling designs, GRTS consistently outperformed all but systematic sampling, which provided slightly better precision at intermediate sample sizes. Depending on the scale of inference, GRTS is useful in monitoring bull trout conservation units through redd counts, though a census may provide a more practical design for monitoring core areas as defined by the U.S. Fish and Wildlife Service.
Poststocking Harvest of Catchable-Sized Rainbow Trout Enhanced by Dietary Supplementation with a Fully Fermented Commercial Yeast Culture during Hatchery Rearing
Authors: Barnes Michael E. , Simpson Greg , Durben Dan J.
Published: October 2009

Catchable-sized salmonids are often stocked without regard to their hatchery rearing history, including the diets used. To evaluate the possible effects of a proprietary, fully fermented yeast Saccharomyces cerevisiae dietary supplement (DVAqua; Diamond V Mills, Cedar Rapids, Iowa) on poststocking harvest, Shasta-strain rainbow trout Oncorhynchus mykiss (280 mm) were fed either a hatchery diet containing 0.125% yeast product or a control diet prior to four stockings over the course of 3 months in two small put-and-take fishing lakes (Upper Mirror and Lower Mirror lakes, South Dakota). An angler census indicated that for each lake on each of four stocking dates, rainbow trout receiving yeast supplementation were harvested at higher rates than fish fed the control diet; each lake had one stocking for which the percent harvest of fish fed the yeast-supplemented diet was more than 30% higher than that of control fish. Overall, returns to the creel in Upper Mirror and Lower Mirror lakes were 17% and 13% higher, respectively, for fish fed the yeast-supplemented diet than for control fish. Most of the rainbow trout were harvested within 2 weeks after stocking, with no difference in timing of harvest observed between the two diet groups. In addition to experiencing greater harvest by anglers during the census, more fish fed the yeast-supplemented diet were recovered from each lake after the census through a combination of gillnetting and voluntary tag reporting by fishermen. The results suggest that rainbow trout fed the yeast-supplemented diet during hatchery rearing consistently returned to the creel in significantly greater numbers than fish receiving the control diet. Fisheries managers may want to consider these results when requesting hatchery-produced catchable rainbow trout for put-and-take waters.
Accounting Explicitly for Predation Mortality in Surplus Production Models: An Application to Longfin Inshore Squid
Authors: Moustahfid Hassan , Tyrrell Megan C. , Link Jason S.
Published: October 2009

One approach to better account for ecosystem considerations in fisheries science is to incorporate ecological interactions into conventional stock assessment models. The longfin inshore squid Loligo pealeii is one of two squid species of ecological and commercial significance in the northwest Atlantic Ocean. A surplus production model with quarterly time steps was fitted to longfin inshore squid total removal (fishing and predation removal) and tuned with fishery-dependent, fishery-independent, and predation-dependent indices to examine the effect of incorporating predation into a single-species model. Total consumption of squid by all predatory fish exceeded the landings in most years of this analysis. The model output indicated that biological reference points for longfin inshore squid differ considerably when predation removals are included. It appears that by not including predation, the model underestimates stock biomass and overestimates fishery surplus production. Short-term stochastic projections of such estimates demonstrate that increasing predation mortality and fishing mortality will decrease the biomass of longfin inshore squid. Failing to account for predation when performing stock assessments for longfin inshore squid and other similar forage species may misrepresent reference point estimates and result in management advice that could lead to biomass declines. We envision that the approach presented here will provide requisite information and a useful example towards improving the current modeling practices for longfin inshore squid and similar forage species.
Effects of Striped Bass Stocking on Largemouth Bass and Spotted Bass in Lewis Smith Lake, Alabama
Authors: Shepherd Michael D. , Maceina Michael J.
Published: October 2009

Introductions of striped bass Morone saxatilis into U.S. reservoirs have caused concern among anglers that target other species owing to the perception that this predator reduces the number of other sport fish and can limit available prey supplies. Recently, this controversy arose in Lewis Smith Lake (8,583 ha), Alabama, prompting this study to examine the effects of stocking striped bass on the resident population of black bass Micropterus spp. From October 2006 to August 2007, the diets of striped bass, largemouth bass M. salmoides, and spotted bass M. punctulatus were examined in this reservoir. The density and biomass of striped bass and black bass were computed from estimates of age-0 black bass abundance, striped bass stocking rates, growth, and survival. Bioenergetics models were used to estimate striped bass and black bass consumptive food demands. Striped bass diets (by weight) were dominated by shad Dorosoma spp. (64%), followed by crayfish Oronectes spp. (12%), while black bass and sunfish Lepomis and crappies Pomoxis spp. comprised 5% and 6% of the diet, respectively. Numerically, sunfish–crappies and black bass only comprised 0.28% and 0.16% of the diets of striped bass. The diets of largemouth bass and spotted bass (by weight) were dominated by crayfish (72% and 75%, respectively) and sunfish–crappies (21% and 9%, respectively), while shad comprised 6% and 14% of the diets, respectively. Diet overlap values between striped bass and black bass were generally low but varied seasonally among species. The highest overlap between the diets of striped bass and black bass was observed in April and June. However, the relative weights of black bass did not decline or the frequency of empty stomachs among these species did not increase during or after this time. Overall, consumptive prey demand was similar between striped bass and black bass. Bioenergetics modeling estimated striped bass consumption of shad, bass–sunfish–crappies, and crayfish averaging 14, 3, and 5 kg/ha, respectively, compared with 3, 6, and 16 kg/ha, respectively, for black bass. Shad consumption by striped bass and black bass (relative to the total annual supply) was within acceptable levels. Striped bass consumption of black bass was low, striped bass and black bass partitioned prey resources, and the temporal differences in maximum consumptive demand varied between black bass and striped bass. Thus, we found that the impact of striped bass stocking on the black bass population was minimal.
Estimates of Predator Consumption of the Northern Shrimp Pandalus borealis with Implications for Estimates of Population Biomass in the Gulf of Maine
Authors: Link Jason S. , Idoine Josef S.
Published: October 2009

Globally, shrimp stocks are important both economically and ecologically, and this is true for the northern shrimp Pandalus borealis in the Gulf of Maine. Understanding and modeling of shrimp stock dynamics have often posed challenges, leading to the suggestion that inclusion of more multidisciplinary data may help to better elucidate shrimp stock dynamics. Thus, we explored the potential implications of including additional information for northern shrimp biomass estimates by examining fish food habits from the Gulf of Maine. We estimated the consumptive removals by 18 predators of northern shrimp. Summed across all predators, the consumptive removals for northern shrimp in recent years were on the order of 20,000–30,000 metric tons. These estimates are generally conservative based upon consumption model assumptions. Compared with survey indices, the trends in consumptive removals were out of phase in the 1990s but both trended upwards in the early 2000s. Compared with the base assessment model, consumptive removals were of the same order of magnitude, trended similarly, and were two to four times higher than estimates of northern shrimp biomass. Changing the natural mortality (M) parameter in the assessment model to higher levels (M from 0.25 to 0.50 or 0.60) reconciled the difference in estimates of biomass. Our objective was neither to fit a new assessment model nor to provide precise estimates of northern shrimp biomass; rather, we demonstrate that including food habits data as contextual information in such assessments is feasible and should lead to enhanced estimates of M. Improvements in obtaining relative estimates of biomass could then result from these enhanced estimates of M, particularly as it would allow for evaluating the tradeoffs between fishing and predation as sources of northern shrimp removals.
The Differential Response to Decompression in Three Species of Nearshore Pacific Rockfish
Authors: Pribyl Alena L. , Schreck Carl B. , Kent Michael L. , Parker Steven J.
Published: October 2009

The genus Sebastes (rockfishes) is an ecologically diverse group of fish, more than 60 species occurring off the Oregon, Washington, and California coasts. As of 2004, seven species of rockfish were classified as overfished by the Pacific Fishery Management Council. Because rockfishes often experience barotrauma to varying degrees when forced up from depth, the management of discard mortality has been difficult. In this study, the macroscopic, morphological, and physiological responses to decompression of black rockfish S. melanops, blue rockfish S. mystinus, and yellowtail rockfish S. flavidus, all nearshore species, were investigated. The rockfish were adjusted to 4.5 atmospheres absolute (ATA; 35 m) over a period of 7–10 d in hyperbaric pressure chambers and when neutrally buoyant were rapidly brought to surface pressure in a simulated ascent. They were then examined for barotrauma injury, and the heart ventricle, head kidney, liver, gill, and pseudobranch were collected for histological analysis. We observed more macroscopic barotrauma indicators in black rockfish and blue rockfish than in yellowtail rockfish. Histological analysis showed emphysema was present in the heart ventricle of more than one-half of the black rockfish, 11% of the blue rockfish, and none of the yellowtail rockfish. No other tissue had observable injury at the histological level that was attributable to barotrauma. The lack of injury at the tissue level for black, blue, and yellowtail rockfishes decompressed from 4.5 ATA is remarkable.