bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical Properties of the Relative Weight (W
r) Index and an Alternative Procedure for Testing W
r Differences between Groups
Authors: Brenden Travis O. , Murphy Brian R. , Birch Jeffrey B.
Published: June 2004

Fishery managers commonly test for differences in relative weight (Wr) between or within populations using standard parametric or nonparametric statistical tests. However, the statistical properties of the Wr index have not been studied; consequently, we cannot be certain that Wr data satisfy the theoretical assumptions upon which many standard tests are based. In particular, we do not know if Wr data are independent and identically distributed (i.i.d.), which is an assumption made by most standard statistical tests and which can increase the type I error rate of a statistical test when it is violated. We derived approximations to the expectation, variance, and covariance of the Wr index using the Delta method and estimated these parameters with sample data for muskellunge Esox masquinongy, largemouth bass Micropterus salmoides, and black crappie Pomoxis nigromaculatus. Additionally, we devised a likelihood ratio test (R-test) that tests for differences in Wr between groups and that does not assume i.i.d. data. We applied the R-test to the sample data and compared the results with those obtained from traditional statistical tests. The statistical properties of the Wr index were conditionally dependent on fish length. This conditionality prevents the covariance from equaling zero across an entire fish sample, so that Wr data will be inherently correlated. For the sample data, parameter estimates increased with fish length and typically were above realistic Wr values. This bias was attributed to variability in sample length-weight data. Traditional statistical tests were more liberal than the R-test in declaring statistical significance when testing for differences in Wr between groups. Based on our derivations, we conclude that Wr data will violate an i.i.d. assumption to some extent. To avoid falsely declaring statistical significance when testing group differences, we recommend that the R-test be used with Wr data.
Regurgitation Rates of Intragastric Radio Transmitters by Adult Chinook Salmon and Steelhead during Upstream Migration in the Columbia and Snake Rivers
Authors: Keefer M. L. , Peery C. A. , Ringe R. R. , Bjornn T. C.
Published: June 2004

Regurgitation rates for radio tags gastrically implanted into adult salmon Oncorhynchus spp. and steelhead O. mykiss are difficult to estimate in the wild because most fish are never recaptured to allow inspection of secondary tags. During 1996–2000, 9,006 Chinook salmon O. tshawytscha and steelhead with both radio tags and secondary tags were released near Bonneville Dam on the Columbia River (Washington–Oregon), and 1,764 fish were recaptured in mid-migration 460 km upstream on the lower Snake River. Minimum annual regurgitation rates ranged from 0.4% to 10.9% for spring–summer Chinook salmon (pooled rate = 3.0%; n = 838), from 3.5% to 4.3% for steelhead (pooled rate = 4.0%; n = 881), and from 0% to 5.6% for fall Chinook salmon (pooled rate = 2.2%; n = 45). Fish that lost transmitters retained them a median of 7 d (average = 14.1 d) before regurgitation, and a majority of losses occurred in the lower Columbia River. Transmitter retention was improved by placing rubber bands or a ring of surgical tubing around part of each tag.
Great Blue Heron Predation on Stocked Rainbow Trout in an Arkansas Tailwater Fishery
Authors: Hodgens Lynn S. , Blumenshine Steven C. , Bednarz James C.
Published: June 2004

Fisheries managers seldom have adequate information to assess their stock losses to avian piscivores, which function as apex predators in many aquatic food webs. Our primary objective was to estimate the number of stocked rainbow trout Oncorhynchus mykiss consumed by great blue herons Ardea herodias on the Bull Shoals and Norfork tailwaters of north-central Arkansas. Between November 2000 and December 2001, we periodically surveyed great blue herons along 150.7 river km on the tailwaters of the Bull Shoals and Norfork dams. Heron density (number/km) in or along the river ranged from 0 to 4/km per survey, with the highest mean number located near the Bull Shoals Dam (2.31 herons/km). We recorded 467 prey captures by herons during 202 observation hours. Sculpin Cottus spp. were the most common prey (N = 120). Most prey (87%) measured 14 cm or less in length, and most captured live trout (85.4%) fell between 10.5 and 28.0 cm in length. While live trout represented only 48 of 359 identifiable prey items (13%), they comprised an estimated 62.8% of heron diet biomass. We developed a bioenergetics model that combined our observations with published metabolic coefficients and relationships to estimate heron energy demand during breeding and nonbreeding seasons. This analysis revealed that trout comprised an estimated 67% of heron daily energy demand in the study area. Heron daily energy demand peaked during the breeding season (March–May). Based on a mean monthly population estimate of 227 great blue herons requiring 156 million kJ of total energy/year, we calculated that herons consumed just under 50,000 catchable-sized stocked trout annually. This loss to great blue herons represents an estimated 2.4% of the approximately 2 million trout stocked in the study area. Thus, great blue heron predation likely represents only a minor source of trout mortality in the Bull Shoals and Norfork tailwaters.
Applications of New Technologies to Instream Flow Studies in Large Rivers
Authors: Gard Mark , Ballard Ed
Published: June 2004

An acoustic Doppler current profiler, underwater video system, hand-held laser range finder and global positioning receiver were used to collect data for instream flow studies on the Sacramento and lower American rivers in California. The use of the equipment decreased the time required to collect spawning criteria data for Chinook salmon Oncorhynchus tshawytscha in deep water in a given area by a factor of 3.4 and doubled the number of transects that could be modeled with the same budget. With the application of quality control criteria, discharges could be measured with an average accuracy of 2.7% versus gauge data with an accuracy of 5%. The total time required to collect data for two-dimensional habitat sites varied with the length and complexity of the sites, and was equivalent to the total time required for physical habitat simulation (PHABSIM) data collection for shorter sites, and less for longer sites.
Simple Control Method to Limit the Spread of the New Zealand Mudsnail Potamopyrgus antipodarum
Authors: Richards David C. , O'Connell Pat , Shinn Dianne Cazier
Published: June 2004

The invasive New Zealand mudsnail Potamopyrgus antipodarum is now well established in rivers in the western United States and is rapidly expanding its range. Potamopyrgus antipodarum is most likely to be spread to new waters via contaminated equipment. To assess a possible method for controlling their spread, we conducted a desiccation and freezing experiment on seven size-classes of P. antipodarum to determine mortality at different temperatures and low or high humidity. Our results show that P. antipodarum does not survive freezing or desiccation at high temperatures with low humidity. At all temperatures, larger P. antipodarum generally survived desiccation longer than smaller ones, and for all size-classes mortality generally increased with increased exposure time. We recommend thoroughly freezing or drying potentially contaminated equipment to limit the spread of P. antipodarum to uninfected aquatic ecosystems.
Effect of Electrofishing Effort on an Index of Biotic Integrity
Authors: Dauwalter Daniel C. , Pert Edmund J.
Published: June 2004

We sampled fishes at 15 stream sites in the Ozark Highlands ecoregion of Arkansas and examined the effects of sampling effort on an index of biotic integrity (IBI). We found that sampling effort affected component metric scores, IBI scores, and qualitative site classifications. The scores of taxonomic richness metrics increased with increasing effort, while relative abundance metrics were inconsistently affected by sampling effort. The scores of all metrics stabilized with increasing effort. Although some deviation from the sampling effort designated for the IBI appeared acceptable, we found that even a sampling effort deviation of 10 mean stream widths from the designated effort (19.6%) caused one qualitative site classification to change. Our results showed that differences in sampling effort can affect IBI scores and result in erroneous stream assessments. They also indicated that an accurate assessment of regional stream conditions relies on incorporating the specific sampling effort designated for the Ozark Highlands IBI.
Producing Fluorescent Marks on Atlantic Salmon Fin Rays and Scales with Calcein via Osmotic Induction
Authors: Mohler Jerre W.
Published: June 2004

Calcified tissues of Atlantic salmon in both larval and postscale developmental life stages became labeled with the fluorochrome dye known as calcein in 7 min by sequential immersion in salt and calcein solutions. I introduce the term “osmotic induction” to describe this process. At 47 d posttreatment, fish that had been exposed to osmotic induction of calcein as nonfeeding larvae exhibited mortality and growth equivalent to that of nonexposed fish (P < 0.05). Atlantic salmon parr (at 5 months posthatch) exposed to osmotic induction of calcein exhibited no mortality during a 120-d posttreatment period. In addition to inducing a calcein mark on fin rays of all larvae and parr, the procedure also produced a distinct calcein mark on scales of parr. A second exposure of parr to osmotic induction 90 d after the first produced a conspicuous 2-band pattern on scales which corresponded to the two separate marking events. Calcein marks are invisible to the unaided eye but were observed without sacrificing the experimental fish by employing a calcein detection device (patent applied for) and fluorescence microscopy. Osmotic induction of calcein marks is a potentially useful technique for batch-marking fish because it greatly reduces the amount of contact time between the fish and marking solution and produces an easily identified mark; this may enable salmon fishery managers and researchers to perform a variety of nonlethal fisheries evaluations not practical or possible using previous marking and tagging techniques.
Immersion Marking of Juvenile Midas Cichlids with Oxytetracycline
Authors: Barker Jennifer M. , McKaye Kenneth R.
Published: June 2004

Laboratory experiments were conducted on the use of oxytetracycline hydrochloride (OTC) for marking juvenile Midas cichlids Amphilophus citrinellus. Juveniles were immersed in tris-buffered OTC solutions of 200, 400, or 600 mg/L for 4, 8, or 16 h. Marked juveniles were detected by the presence of a fluorescent mark on spines and rays when viewed under an ultraviolet light. Immersion in 600-mg/L OTC solution for 8 h produced the optimum mark intensity. No immediate mortality occurred after the marking procedure. Retention of the externally visible marks and effect of OTC treatment on long-term survival were examined by rearing both marked and unmarked juveniles for 6 weeks. Marks were visible for 2–7 weeks, depending on the size of the juveniles when marked. Marking with OTC had no effect on survival over the 6-week period. The effects of light exposure on retention and intensity of externally visible marks were examined by rearing marked fry under both dark and light conditions. Retention and intensity of externally visible marks were greater in juveniles held in the dark. The effect of OTC treatment on the vulnerability of juveniles to predation was determined by subjecting both marked and unmarked juveniles to predation by bigmouth sleepers Gobiomorus dormitor 72 h after OTC treatment. OTC marking did not affect the vulnerability of juveniles to predation. Our results indicate that this OTC marking technique would be suitable for short-term mark–recapture, growth, and alloparental care studies of Midas cichlids.
Effectiveness of Electrical Fish Barriers Associated with the Central Arizona Project
Authors: Clarkson Robert W.
Published: June 2004

The Central Arizona Project (CAP) canal delivers Colorado River water into the Gila River basin. During its planning and construction, issues arose regarding the unwanted entrainment and transport of nonindigenous fishes and other aquatic biota into, through, and out of the canal. One control strategy was the emplacement of electrical fish barriers on two CAP distributary canals to prevent fishes from moving upstream into the Gila River drainage. The operation, maintenance, and effectiveness of these barriers are described for the period 1988–2000. Documented outages totaled more than 100 h, representing less than 0.001% downtime since installation. It is nearly certain that outages allowed immigration by undesired fish(es). Immigrations that occurred when the barriers were operating according to design criteria indicate that the barriers do not totally block the passage of upstream-migrating fish. The proximate sources of electrical barrier outage included component damage from lightning strikes, component breakdowns, failure to adhere to component maintenance and replacement schedules, failure to incorporate adequate protection and redundancies to certain system components, inadequate training of personnel, and unknown causes. Known outages of remote monitoring systems (which are necessary to document outages and understand the potential for undocumented barrier outages) totaled more than 400 d, representing about 3% of the period of barrier operations. The complexity of electrical barrier systems and the problems such intricacy creates for operation and monitoring may always preclude absolute effectiveness. Additional refinements to system components, personnel training, and operation procedures may reduce barrier failures but add further to that complexity. Management agencies will have to determine the cost-effectiveness of such refinements.
Largemouth Bass Abundance and Angler Catch Rates following a Habitat Enhancement Project at Lake Kissimmee, Florida
Authors: Allen Mike S. , Tugend Kimberly I. , Mann Marty J.
Published: June 2004

A habitat enhancement project was conducted at Lake Kissimmee, Florida, during 1995-1996 to improve fish habitat and remove dense inshore vegetation caused by stabilized water levels. We evaluated abundance of age-1 (<250 mm total length (TL)) and adult (fish at least 356 mm TL and all sizes of fish caught by anglers) largemouth bass Micropterus salmoides before and after the habitat enhancement. Mean electrofishing catch per hour (CPH) of age-1 largemouth bass increased significantly after the 1995-1996 habitat enhancement, suggesting strong year-classes for 2 years after the habitat enhancement (i.e., 1997-1998 year-classes). Growth of age-1 largemouth bass also increased following habitat enhancement; mean total length of age-1 fish averaged 143 mm before enhancement and 186 mm after enhancement. Catch curves conducted in 2001 and 2002 corroborated historical electrofishing data indicating that the 1997 and 1998 year-classes were abundant as adults compared with other year-classes in the age frequencies. Age-1 largemouth bass electrofishing catch rates were not related to seasonal water levels or coverage of hydrilla Hydrilla verticillata. Despite the rapid growth rates and high abundance of the 1997 and 1998 year-classes, neither electrofishing catch rates of largemouth bass at least 356 mm TL nor angler catch rates of largemouth bass (fish/h, all sizes of fish, harvested or released; data from creel surveys) differed significantly between preenhancement and postenhancement periods. Thus, we were unable to detect a change in adult largemouth bass abundance or angler catch rates following the habitat enhancement. Fishing effort directed toward largemouth bass declined after enhancement for the winter period (November-February) but did not differ significantly between preenhancement and postenhancement periods for the summer (May-August) period. Benefits of muck removal concurrent with lake drawdowns include increased recreational opportunities and improved habitat. However, our results indicate that fish population responses to drawdowns and muck removals may vary and detecting effects on the adult largemouth bass populations can be difficult. Therefore, habitat enhancement efforts should focus on lakewide recreational benefits rather than benefits to a single preferred species (e.g., largemouth bass).
Seasonal Daphnia Biomass in Winterkill and Nonwinterkill Glacial Lakes of South Dakota
Authors: Isermann Daniel A. , Chipps Steven R. , Brown Michael L.
Published: June 2004

We compared the seasonal biomass (μg dry weight/L) and body size of Daphnia pulex populations between South Dakota lakes that experienced nearly complete winterkill (n = 2) and those that did not experience fish winterkill the previous winter (n = 2). In spring (March–May), D. pulex biomass was substantially lower in winterkill lakes (0.4–1.9 μg/L) than in nonwinterkill lakes (13.8–129.4 μg/L). In summer months (June–July), D. pulex biomass increased in all lakes but was generally higher in winterkill lakes (332.1–469.3 μg/L) than in nonwinterkill lakes (88.6–204.2 μg/L). By September, D. pulex biomass was substantially higher in winterkill lakes (243.8 μg/L) than in nonwinterkill lakes (1.0 μg/L). The mean size of D. pulex increased significantly from March to August in winterkill lakes but not in nonwinterkill lakes. The seasonal differences in D. pulex biomass and size may have been related to size-selective predation by planktivorous fishes because the ratio of spine length to body length in D. pulex was significantly lower in winterkill lakes (mean, 0.34) than in nonwinterkill lakes (mean, 0.43). Moreover, seasonal patterns in chlorophyll-a biomass were inversely related to D. pulex biomass. The production and subsequent hatching of resting eggs may be important for recolonization of Daphnia populations after severe winter conditions. The survival and growth of zooplanktivorous fish that are stocked to repopulate winterkill lakes may be increased by delaying stocking until Daphnia populations recover from severe winterkill.
Conservation of Population Diversity of Pacific Salmon in Southeast Alaska
Authors: Halupka Karl C. , Willson Mary F. , Bryant Mason D. , Everest Fred H. , Gharrett Anthony J.
Published: June 2004

We analyzed intraspecific variation in selected biological characteristics of five species of Pacific salmon Oncorhynchus spp. in southeast Alaska and adjacent areas of Canada with a particular interest in describing the variation among populations and suggesting conservation priorities to preserve existing variation. We identified traits that showed high levels of among-population variation, evaluated the interspecific consistency of variation patterns, and noted the relationship of these traits to potential adaptive variation. In addition, we graphically identified populations with distinctive phenotypic and demographic characteristics as outliers from the distribution of mean values of traits taken from populations throughout the region. We also reviewed allozyme surveys to identify populations that differed in terms of the geographic clustering patterns of allele frequencies. Approximately 9,000 salmon populations occur in the study area, and sufficient data were available from 2,062 (23%) of them to analyze at least one characteristic. We identified 47 populations represented by adequate data sets that have distinctive characteristics. An additional 35 populations, represented by limited samples or unusual nominal traits, may be regionally distinctive. Of the 47 adequately sampled, distinctive populations, 22 met our criteria for conservation consideration: (1) high potential for adaptive variation (including distinctive run timing), (2) a distinctive trait combined with high spawner abundance or allozyme frequencies that diverge from geographic clustering patterns, and (3) more than one distinctive characteristic or freshwater habitat shared with other distinctive populations. Freshwater habitats for 6 of those 22 populations are located in watersheds that do not have restrictive land use designations and warrant the highest conservation priority.
Evaluation of Stomach Tubes and Gastric Lavage for Sampling Diets from Blue Catfish and Flathead Catfish
Authors: Waters D. Scott , Kwak Thomas J. , Arnott Joshua B. , Pine William E.
Published: June 2004

We compared the ability to extract all stomach contents by using stomach tubes or gastric lavage to sample diets from blue catfish Ictalurus furcatus and flathead catfish Pylodictis olivaris. Pulsed gastric lavage (PGL) removed a significantly greater proportion of stomach content mass (95.6%) from blue catfish than did stomach tubes (14.6%). Percent mass of flathead catfish contents removed with PGL (96.0%) was not significantly different from that removed with stomach tubes (86.9%). Based on the greater effectiveness of PGL for blue catfish, combined with a shorter mean time required per sample (69 versus 118 s) and the better preservation of extracted diet material, we recommend using PGL as a nonlethal technique to collect diet samples from large catfishes.
Portable Floating Electrofishing Unit for Fish Collections in Freshwater Stream Systems
Authors: Price David J. , Beiting Michael G. , Birge Wesley J.
Published: June 2004

Fish collection can be difficult if the stream being sampled is too deep for backpack electroshockers and does not allow boat access. A design for a portable, flat-bottomed, floating electroshocking unit is described. The unit consists of a one-piece, structural-foam big-wheel cart from which the wheels and stand were removed. In tests, the unit was able to float loads weighing up to 90.8 kg. The total weight of the unit with the electronics and generator installed is approximately 68.1 kg, which allows two persons to transport the unit to a stream and lift it over shallow riffles and log jams. The unit allows sampling of stream pools that can be waded and provides greater mobility and less fatigue for the sampler carrying the anode and cathode poles. Due to its larger electrical field, this unit offers greater sampling distance than backpack electroshockers. The total cost, including the electronics, anode and cathode poles, and generator, was about US$3,800.
Relationship between Surface Water Temperature and Steelhead Distributions in Lake Michigan
Authors: Höök Tomas O. , Rutherford Edward S. , Brines Shannon J. , Schwab David J. , McCormick Michael J.
Published: June 2004

Salmonines support valuable recreational fisheries and are the predominant predators in the open waters of the Great Lakes, yet the spatial distributions of salmonines in these systems have not been fully documented. We analyzed the horizontal distributions of steelhead Oncorhynchus mykiss in Lake Michigan from 1992 to 1997 and related these distributions to mean surface temperature and temperature variation. We used angler catch rate data from Lake Michigan natural resources agencies to index the spatial and temporal distributions of steelhead and obtained surface water temperature data from advanced very-high-resolution radiometer satellite imagery through the National Oceanic and Atmospheric Administration's CoastWatch Program. During most months, steelhead catch rates were negatively related to surface temperature and were highest in areas of high temperature variation (i.e., vertical thermal fronts and upwelling zones) where thermal conditions and prey densities may have been optimal for growth. Our results demonstrate how remotely sensed and creel survey data can be integrated to allow for more effective exploitation and management of lakewide fish stocks while enabling researchers to generate and test hypotheses regarding the spatial distributions of fish populations.
Verifying Residuals from Catch Curves to Detect Recruitment Variation in Largemouth Bass and Crappies
Authors: Maceina Michael J.
Published: June 2004

Residuals associated with catch-curve regressions can represent variable recruitment in fish populations, but the use of this method to quantify recruitment variation has not been verified. I computed age-0 and age-1 catch rates of crappies Pomoxis spp. collected with trap nets set in the fall in three Alabama reservoirs and the age-1 catch rate of largemouth bass Micropterus salmoides captured with electrofishing during spring over a 13-year period in a single Georgia reservoir. These indices of juvenile abundance were correlated (r = 0.52–0.81, P < 0.01) to residuals generated from catch-curve regressions for electrofishing data collected when these same year-classes recruited to the fishery at age 3 and older. At higher age-0 crappie and age-1 largemouth bass catch rates, these relations became curvilinear, and improved fit was computed with data transformation and nonlinear fits to the data. An asymptotic relation was observed between age-0 and age-1 catch rates for the same crappie year-classes, and an inverse relation was evident between mean length at age 1 and juvenile crappie catch rates. This result suggested that density-dependent growth suppression and mortality occurred, as age-0 fish did not proportionally recruit to the age-3+ fishery. However, the age-1 crappie (about 18 months old) catch rate was linearly related (r2 = 0.48–0.55; P < 0.01) to residuals when data were compared separately for each reservoir, which suggested that full recruitment to the population occurred at this age. For largemouth bass, mean length at age 1 was positively related to age-1 catch rate, and recruitment of strong year-classes to the fishery appeared proportionally greater than for abundant age-0 crappies. Residuals generated from catch-curve regressions can serve as a useful quantitative index of juvenile crappie and largemouth bass abundance that can be used in subsequent analyses to explain recruitment variation. However, in some instances, initial strong year-class abundance may not be fully expressed in the fishery later in life.
Species Richness and Centrarchid Abundance in Littoral Habitats of Three Southern U.S. Reservoirs
Authors: Hugh Barwick D.
Published: June 2004

Species richness and centrarchid abundance associated with coarse woody debris (CWD), residentially developed habitats (DEV), and undisturbed (UND) habitats in Lake James (North Carolina), Lake Hickory (North Carolina), and Fishing Creek Lake (South Carolina) were evaluated by use of a boat-mounted electrofisher in spring, summer, and fall of 1999–2000. Species richness and centrarchid abundance were generally higher in CWD and DEV habitats than in UND habitat during most seasons in all reservoirs. Higher species richness and centrarchid abundance in CWD and DEV habitats were probably related to greater habitat complexity than in UND habitat, which made these two habitats more desirable to fish. My findings indicate the beneficial role of complex littoral structure on the distribution of fish in these reservoirs and the need for natural resource managers, riparian landowners, and reservoir owners to work cooperatively to protect and enhance habitat where possible.
Prevalence of Myxobolus cerebralis at Juvenile Salmonid Acclimation Sites in Northeastern Oregon
Authors: Sollid Sarah A. , Lorz Harriet V. , Stevens Donald G. , Reno Paul W. , Bartholomew Jerri L.
Published: June 2004

Fry of rainbow trout Oncorhynchus mykiss held as sentinel fish became infected with Myxobolus cerebralis when held at all juvenile acclimation sites for spring Chinook salmon O. tshawytscha and steelhead O. mykiss (anadromous rainbow trout) and thus expand the known range of M. cerebralis in northeastern Oregon. In spring 2001, replicate cages of rainbow trout fry were placed at the intake site of each facility and sampled at approximately 14, 28, and 50 d. Infection prevalence, as determined by the presence of M. cerebralis DNA following polymerase chain reaction (PCR) amplification, was relatively low (<17.5%) at most acclimation sites. However, a significantly higher prevalence of infection in sentinel fry held at the Wallowa facility (65%) identified this site as presenting a higher risk for juvenile steelhead to M. cerebralis exposure than other sites. Further, PCR analysis of ossified cranial elements from steelhead juveniles held at the Wallowa facility for 6 weeks demonstrated a comparable prevalence of infection, 52%. Detection of similar infection prevalence in fry and juveniles at the same site demonstrates the usefulness of sentinel exposures as a surrogate for lethally sampling valuable salmonid juveniles. In addition, this study suggests that infection of anadromous salmonids may complicate management efforts to contain the parasite within northeastern Oregon.
Coded Wire Tag Retention in Ebonyshell Mussels Fusconaia ebena
Authors: Layzer James B. , Heinricher Jackie R.
Published: June 2004

Ebonyshell Fusconaia ebena (38–75 mm long) were collected from Kentucky Lake, Tennessee, and tagged in the hinge ligament with coded wire tags. Mussels were then suspended in pocket nets in an embayment of Kentucky Lake. After 2 years, the 50 tagged individuals were retrieved. Survival and tag retention were 100%. Eleven individuals were sacrificed and their tags were retrieved by making a longitudinal cut through the hinge ligament. Because coded wire tags are not visible externally, they are especially useful for detecting illegally harvested mussels.
Length at Release Affects Movement and Recapture of Lake-Stocked Brown Trout
Authors: Hyvärinen Pekka , Vehanen Teppo
Published: June 2004

The effect of length (total length = 15-50 cm) at release on the yield and recapture of stocked brown trout Salmo trutta was examined by tagging experiments in a large boreal lake, Lake Oulujärvi in Finland (928 km2). The time the fish spent in the lake before harvesting and the size of the area from which they were harvested diminished with increasing length at release. Small brown trout (<40 cm) moved towards a part of the lake where the highest densities of pelagic prey fish are found, whereas large brown trout (≥40 cm) were captured near their release sites. The longer the distance between the release site of the small brown trout and the good foraging area, the lower their recapture rate. Both relative yield and recapture rate (per 1,000 fish released) increased with increasing fish length at release. However, the positive relation between recapture rate and fish length at release disappeared or turned negative (depending on the release site) when the production costs of fish were taken into account and the recapture rate was calculated per constant investment (€100,000 (euros)).
Oviduct Insertion of Radio Transmitters as a Means of Locating Northern Pike Spawning Habitat
Authors: Pierce Rodney B.
Published: June 2004

I inserted radio transmitters into the oviducts of northern pike Esox lucius in an attempt to find their spawning grounds. Oviduct insertion of miniature radio transmitters was quick and easy. I hoped that transmitters would be expelled with the eggs to aid in identifying critical habitat used for egg deposition. Ten transmitters were implanted in the egg masses of female northern pike that were staging for spawning. Four of the transmitters were expelled during the spawning period, two in emergent shoreline vegetation and two in submerged vegetation. Northern pike that retained transmitters were smaller than fish that expelled them, indicating that expulsion was influenced by the size of the transmitter in relation to the fish's size. Although transmitters were not expelled by all study fish, advances in miniaturization and refinements in transmitter shape hold promise for future application of this technique.
Evaluation of the Use of Visible Implant Tags in Age-0 Atlantic Cod
Authors: Olsen Esben M. , Gjøsæter Jakob , Stenseth Nils C.
Published: June 2004

The visible implant elastomer (VIE) tag and the soft visible implant alphanumeric (VIAlpha) tag were evaluated as methods for tagging age-0 Atlantic cod Gadus morhua. Tank experiments on laboratory-bred Atlantic cod (82–141 mm) lasted 150 d. The VIE tag proved to be a good alternative when put on the dorsal part of the fish, with no tag loss and good tag visibility. When put on the ventral part of the fish, however, many VIE tags were covered by growing silvery scales. Retention of soft VIAlpha tags injected behind the eye was quite low (67%), but larger fish had higher tag retention than smaller fish. Survival of experimental fish was high (96%). Mean specific growth rates ranged from 0.46% to 0.51% per day. Both VIE and soft VIAlpha tags were used to individually tag age-0 Atlantic cod (85–290 mm) in the wild. Skin pigmentation of wild Atlantic cod made reading soft VIAlpha tags difficult, while VIE tagging on the dorsal part of the fish still worked well. We suggest that VIE tags are a good alternative for short-term demographic studies on age-0 Atlantic cod, while low retention rates cast doubt on the use of soft VIAlpha tags on these small fish.
Influence of Habitat Type on Food Supply, Selectivity, and Diet Overlap of Bonneville Cutthroat Trout and Nonnative Brook Trout in Beaver Creek, Idaho
Authors: Hilderbrand Robert H. , Kershner Jeffrey L.
Published: June 2004

We collected invertebrate drift samples and stomach contents of native Bonneville cutthroat trout Oncorhynchus clarki utah and nonnative brook trout Salvelinus fontinalis in Beaver Creek, Idaho, during August 1995 to assess food availability and the potential for competition. Regardless of whether samples came from beaver pond or from high-gradient or low-gradient reaches, aquatic Diptera numerically dominated drifting invertebrates by at least fivefold over all other categories captured in 1-h drift samples. Abundances and drift densities of drifting invertebrates were high in the three reach habitat types sampled: beaver pond (3,152 individuals; 18.9 invertebrates/m3), high-gradient reach (5,216 individuals; 26.5 invertebrates/m3), and low-gradient reach (4,908 individuals; 17.2 invertebrates/m3). Cutthroat trout consumed significantly more invertebrates per individual than did brook trout. However, there was no relationship between fish length and consumption. Diets of both brook and cutthroat trout were dominated by Diptera in beaver ponds and terrestrial invertebrates in the high-gradient reach. In the low-gradient reach, Diptera dominated brook trout diets, whereas both Diptera and terrestrial invertebrates dominated diets of cutthroat trout. Both trout species consistently selected terrestrial invertebrates and Trichoptera in all reach types. Diet overlap between brook and cutthroat trout was 92% in beaver ponds, 75% in the high-gradient reach, and 65% in the low-gradient reach. The high degree of diet overlap suggests the possibility of competition between nonnative brook trout and cutthroat trout if food should become limiting, but we found little evidence that food was limiting during late summer in Beaver Creek.
Development and Use of a Simple DNA Test to Distinguish Larval Redhorse Species in the Oconee River, Georgia
Authors: Wirgin Isaac , Currie Diane D. , Stabile Joseph , Jennings Cecil A.
Published: June 2004

The robust redhorse Moxostoma robustum is a rare catostomid species that was recently “rediscovered” in three Atlantic slope drainages in the southeastern United States, including the Oconee River, Georgia. Adult population size in the Oconee River is declining, and the population may be senescent due to recruitment failure. Evaluation of the environmental factors affecting the success of young life stages requires the ability to distinguish robust redhorse larvae from those of other redhorse species in the Oconee River. The use of morphological approaches, including size at collection date, have proven to be problematic in distinguishing larval robust redhorse from notchlip redhorse M. collapsum from the Oconee River. We developed a mitochondrial DNA (mtDNA) assay to distinguish between reference adults of these two redhorse species from the Oconee, Savannah, and Pee Dee rivers. This mtDNA assay was then applied to unknown larval redhorse collections from the Oconee River. In one collection, discordance was revealed in 40% of the individual larvae identified by both size at collection date and mtDNA. Of these, 75% of the fish thought to be notchlip redhorses based on size at date of collection exhibited robust redhorse mtDNA haplotypes. These results illustrate the utility of DNA techniques in characterizing the young life stages of fish and suggest that earlier surveys underestimated the abundance of larval robust redhorses in the Oconee River.
Construction of a Junction Box for Use with an Inexpensive, Commercially Available Underwater Video Camera Suitable for Aquatic Research
Authors: Cooke Steven J. , Bunt Christopher M.
Published: June 2004

Underwater video camera apparatus is an important fisheries research tool. Such cameras, developed and marketed for recreational anglers, provide an opportunity for researchers to easily obtain cost-effective and waterproof video apparatus for fisheries research. We detail a series of modifications to an inexpensive, commercially available underwater video camera (about US$125) that provide flexibility for deploying the equipment in the laboratory or in the field. Specifically, we describe the design of a junction box between the camera cable and the power supply and video feed that can be constructed for about $25. We also describe different deployment configurations and detail several examples of the data we have been able to collect using this technology.
Electrofishing Injury and Short-Term Mortality in Hatchery-Reared Rainbow Trout Stocked into an Ozark Stream
Authors: Walsh Maureen G. , Winkelman Dana L. , Bahr Robert J.
Published: June 2004

We conducted an electrofishing injury study to evaluate potential effects of sampling procedures on survival and health of hatchery rainbow trout Oncorhynchus mykiss (187–307 mm total length) stocked into an Ozark stream. We assessed two groups of trout: one group had acclimated to stream conditions for 1 month; the other group was handled and transported just before the study. Each group was sampled by electrofishing (boat-mounted, 60-Hz AC) and seining (controls), resulting in four treatment groups (N = 21). We held fish for 48 h to evaluate mortalities in that period, then euthanized all fish and examined them for hemorrhages and spinal damage. No fish died during the 48-h holding period, indicating that our procedures did not cause significant sampling-related mortality among stocked trout in Brush Creek. Spinal damage was observed in 5% of fish collected with electrofishing but in none of the control fish. We found hemorrhages in 90% of electrofished trout but none in control fish, and recently handled and hauled trout had a greater occurrence and severity of hemorrhaging.
Movement, Home Range, and Site Fidelity of Bluegills in a Great Plains Lake
Authors: Paukert Craig P. , Willis David W. , Bouchard Michelle A.
Published: June 2004

Little is known about the distribution, movement, and home ranges of bluegills Lepomis macrochirus in lentic environments. Therefore, the objectives of this study were to evaluate the seasonal and diel differences in movement rates, site fidelity, and home range of bluegills in a shallow, natural Great Plains lake. A total of 78 bluegills (200–273 mm total length) were implanted with radio transmitters in March and May 2000. Of these fish, 10 males and 10 females were randomly selected and located every 2 h during one 24-h period each month from April to September 2000. Bluegill movement peaked during midsummer; however, there was little difference in diel movements, suggesting relatively consistent movement throughout the 24-h period. Home range estimates (which included the 24-h tracking plus an additional six locations from the same fish located once per day for six consecutive days each month) ranged up to 172 ha, probably because only about half of the bluegills exhibited site fidelity during any month sampled. Bluegill movement did not appear to be strongly linked with water temperature, barometric pressure, or wind speed. These results suggest that bluegills move considerable distances and that many roam throughout this 332-ha shallow lake. However, diel patterns were not evident. Sampling bluegills in Great Plains lakes using passive gears (e.g., trap nets) may be most effective during the summer months, when fish are most active. Active sampling (e.g., electrofishing) may be more effective than the use of passive gears in spring and fall, when bluegills are less active.
Population Characteristics of Greenback Cutthroat Trout in Streams: Their Relation to Model Predictions andRecovery Criteria
Authors: Young Michael K. , Guenther-Gloss Paula M.
Published: June 2004

Fishes listed under the U.S. Endangered Species Act receive intensive management, but evaluations of population characteristics are rare. We report population and habitat characteristics of federally threatened greenback cutthroat trout Oncorhynchus clarki stomias in 12 streams in north-central Colorado surveyed in 1998 and 1999. Our objectives were to assess population size, structure, and distribution, to evaluate a model developed by Harig and Fausch (2002) to assess translocation success, and to compare population characteristics to those reported in the recovery plan. Allopatric population sizes in 10 streams varied from 170 to 7,347 greenback cutthroat trout at least 75 mm long, whereas the 2 streams with brook trout throughout supported 0–142 greenback cutthroat trout. Populations displayed few upstream–downstream trends in fish abundance or mean length, and the coefficient of variation among sampled reaches within streams averaged 61%. As the density of fish at least 75 mm long increased, the percentage of juvenile (<75 mm) fish in a population increased, the percentage of adult (>125 mm) fish longer than 200 mm decreased, and the average weight of a 200-mm fish declined. The abundance of juvenile fish was positively correlated with summer water temperature. Population estimates were highly correlated with the translocation model index values, suggesting that the translocation model may apply to other cutthroat trout taxa in similar environments. Of the 12 streams for which our extensive field data are available, 4 satisfied the recovery criteria we studied and other criteria in the recovery plan; 8 did not. We conclude that many populations of greenback cutthroat trout, including some that meet recovery criteria, are still at risk of extinction and that a reliable monitoring protocol needs to be established.
A Conditional Constant Catch Policy for Managing the Pacific Halibut Fishery
Authors: Clark William G. , Hare Steven R.
Published: June 2004

Since 1985, the staff of the International Pacific Halibut Commission (IPHC) has used a constant harvest rate policy—currently 20% of exploitable biomass—to estimate the yield currently available from Pacific halibut Hippoglossus stenolepis stock. This paper outlines a more stable alternative policy in which yield is held constant at some ceiling level so long as taking that yield would not result in a total exploitation rate exceeding a specified ceiling rate. During any periods of low abundance, the policy would revert to a constant harvest rate policy at the ceiling rate. The ceiling harvest rate would be chosen so as to assure that spawning biomass remained above a specified minimum. A policy of this kind could produce a yield similar to the present 20% constant harvest rate policy but with much less year-to-year variation attributable to changes in stock abundance, assessment methods, and estimated removals by other fisheries.
Effects of Acoustic Transmitters on Swimming Performance and Predator Avoidance of Juvenile Chinook Salmon
Authors: Anglea Steven M. , Geist David R. , Brown Richard S. , Deters Katherine A. , McDonald Robert D.
Published: June 2004

The objective of this study was to determine whether juvenile Chinook salmon Oncorhynchus tshawytscha are negatively influenced by the intraperitoneal implantation of acoustic transmitters. We evaluated swimming performance and predator avoidance of juvenile salmonids implanted with acoustic transmitters that weighed up to 6.7% of the fish's body weight in air. Critical swimming speeds (Ucrit) of tagged, sham-tagged (surgery but no tag), and control fish were measured in a respirometer to determine tag effects on swimming performance. Swimming performance was similar among treatment groups at 1-d and 21-d postsurgery intervals. Predator avoidance of fish implanted with active tags was evaluated to determine whether tagged fish were impaired by the operation of the tags or predators were attracted to the signals emitted from the tags. Predator avoidance was evaluated by comparing the proportion of each treatment group consumed (active tag, inactive tag, sham, and control) during exposure to piscivorous adult rainbow trout O. mykiss. Surgical implantation of acoustic tags in juvenile fall Chinook salmon did not significantly affect swimming performance. Implantation of acoustic transmitters (active and inactive) did not result in greater predation susceptibility in tagged fish than in untagged fish.
Electrofishing Effort and Fish Species Richness and Relative Abundance in Ozark Highland Streams of Arkansas
Authors: Dauwalter Daniel C. , Pert Edmund J.
Published: June 2004

We sampled 15 stream sites in the Ozark Highlands ecoregion of Arkansas and examined the effect of increased backpack electrofishing effort on the richness and relative abundance estimates of fish species. Each site was 75 mean stream widths (MSWs) long and was divided into 15 consecutive segments that were each 5 MSWs long. For each site the percent of empirical and theoretical species richness and the percent of relative abundance similarity to the entire fish assemblage were calculated by adding consecutive segments using an approach that resulted in 15 accumulation curves per assemblage character for each stream site. On average, a distance of 53.8 MSWs (SD = 7.4) was needed to sample 95% of empirical species richness at a stream site, which was equal to an area of 2,722.0 m2 (SD = 1,967.0). For sampling 95% of theoretical species richness, an average of 101.8 MSWs (SD = 34.5), or 5,055.7 m2 (SD = 3,667.4), was needed. Obtaining 95% relative abundance similarity required an average sampling effort equivalent to 24.0 MSWs (SD = 8.9), or 1,269.7 m2 (SD = 932.1). Mean stream width explained more variance in the reach lengths and areas needed for estimates of species richness and relative abundance than did riffle-pool sequence length or watershed size. Our results should offer insight into species richness and relative abundance accumulation rates when using a one-pass backpack electrofishing sample in Ozark Highland streams of Arkansas.