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Objective: Arctic Lampreys Lethenteron camtschaticum are harvested by subsistence and commercial fisheries in the Yukon–Kuskokwim River region of Alaska; however, baseline population data are deficient. For mark–recapture and telemetry studies to be effectively implemented to assess Arctic Lamprey abundance, migratory and dispersal patterns, and spawning locations, tags must not impact fish survival, physiology, or behavior. Methods: For this laboratory evaluation, we examined survival, tag retention, swim endurance at short‐term (1 day posttreatment) and long‐term (43 days [~6 weeks] posttreatment) intervals, and incision healing for T‐bar‐tagged and radio‐tagged prespawn Yukon River Arctic Lampreys (N = 216). Six treatment groups were evaluated: control; sham surgery; external T‐bar anchor tag; and small (0.30 g; 0.1–0.4% tag burden [ratio of tag weight to fish body weight]), medium (0.57 g; 0.2–0.8% tag burden), and large (1.50 g; 0.6–1.9% tag burden) internal dummy radio transmitter tags. Result: Although all lampreys survived tagging and surgical procedures through the first 4 weeks of the experiment, a higher tag burden was associated with an increased mortality hazard up to 35 weeks postsurgery. Over the 14‐week experimental period, one T‐bar tag and one small radio tag were shed by lampreys. Although treatment was not a significant predictor of swim endurance, a higher tag burden led to reductions in swim endurance at 1 day posttreatment but not at 43 days posttreatment. Healing did not differ among surgical treatment groups, but persistent inflammation was observed at incision sites and skin erosion was observed at antenna protrusion locations. Conclusion: These results indicate that T‐bar anchor tags and internal radio tags are acceptable for Arctic Lamprey tagging studies if the radio tag burden is ≤1.3% for short‐term (≤14‐week) studies and ≤0.5% for long‐term (≥14‐week) studies. Impact statementWe tested the efficacy of using radiotelemetry and T‐bar anchor tags on Arctic Lampreys for future data collection. Our results provide insight on the use of these tag types as well as a maximum tag size standard for future field studies utilizing the radiotelemetry tagging of Arctic Lampreys. These tagging methods will be instrumental for collecting information on this species for informed subsistence resource management practices in Alaska. [ABSTRACT FROM AUTHOR]

Long‐term effects of evolving fisheries management, changing angler practices, and stream habitat development on stream trout fisheries in southeastern Minnesota, USA, were examined by analyzing data on >1,000 weekly winners from a single‐watershed, catch‐and‐harvest Brown Trout Salmo trutta fishing contest spanning 54 years. The weights of winning fish declined significantly across the period examined. No‐entry weeks increased within the past two decades, corresponding to expanding catch‐and‐release fishing. The streams that produced winning fish shifted as stream access increased, degraded stream habitat was improved, and various angling restrictions were instituted. Most winning fish were caught with live or preserved bait, although the proportion of winners caught with artificial lures doubled from the 1960s to the 2010s. The interpretation of contest results must consider various angling regulations (e.g., protected slot lengths, artificial lures only, catch and release only) that were placed on some reaches during and after the 1980s, increasing voluntary catch‐and‐release practices of contemporary anglers, and expanding stream access and habitat improvements within the watershed. [ABSTRACT FROM AUTHOR]

Frozen storage can affect the physical characteristics of biological samples, and the effects can vary based on the frozen storage method that is used. We compared four frozen storage treatments: (1) flash frozen in liquid nitrogen (LN2) and stored at −20°C, (2) flash frozen in LN2 and stored at −65°C, (3) frozen in a saline solution (0.9% NaCl) and stored at −20°C, and (4) glazed with deionized (DI) water and stored at −20°C, to investigate the effects of frozen storage on wet weight, percent dry weight, and length of Mummichogs Fundulus heteroclitus. Mummichog wet weights differed from Prestorage wet weights for all treatments. Postthaw wet weight increased from the Prestorage wet weight for Mummichogs that were frozen in a saline solution (3–5% for 4–12 g fish). Conversely, Postthaw wet weight decreased from Prestorage wet weight (1–4% for 4–12 g fish) for Mummichogs that were frozen with LN2 and stored at −20°C or −65°C and Mummichogs that were glazed with deionized water and stored at −20°C. Subsequently, percent dry weight was underestimated by 0.77% for the Mummichogs that were frozen in a saline solution and overestimated for those that were frozen with LN2 and stored at −20°C (0.94%) or −65°C (0.60%) and those that were glazed with deionized water and stored at −20°C (0.71%). Fish total length decreased 2–3% after the samples had been frozen, and they did not differ among the four treatments. When possible, fish that are stored frozen should be measured and weighed alive or immediately after being euthanized, and if this is not possible, we suggest glazing the fish with water and developing correction factors for water loss and shrinkage. [ABSTRACT FROM AUTHOR]

In diet studies, stomach contents from predatory fish may be difficult to identify due to digestion. The Gizzard Shad Dorosoma cepedianum is an important prey species for sport fish; thus, determining the size of ingested shad can assist with evaluating competitive interactions, bioenergetic patterns, and niche partitioning and can add precision to predictive models. The gizzard organ of clupeids appears to be more resistant to digestion compared to other tissues and can often be found in the stomachs of predatory fish after other tissues from Gizzard Shad are digested. If the gizzard diameter is proportional to Gizzard Shad weight or length, it could be a useful structure for estimating the size of partially digested Gizzard Shad when other structures that are traditionally used to estimate weight or length (e.g., backbones) are damaged due to advanced digestion. For this reason, we evaluated the allometry relating gizzard diameter and Gizzard Shad weight and TL. We sampled a total of 936 Gizzard Shad from nine Oklahoma reservoirs. Fish were frozen and later thawed; they were measured for weight (±0.01 g) and TL (±1 mm), and the gizzard was then removed. Gizzard diameter was measured (±0.1 mm) at its widest point using calipers. Eight different equations were evaluated to find the best relationship (lowest Akaike's information criterion) between gizzard diameter and weight or length. The relationship between gizzard diameter and fish weight was best modeled as a second‐order polynomial, whereas the relationship between gizzard diameter and fish TL was best described by a five‐parameter Richard's equation. Both relationships explained over 80% of the variation in Gizzard Shad size. The 95% CIs for weight (±4–7%) and TL (±2–7%) indicated good overall precision for mean fish size based on gizzard diameter. Therefore, we recommend using gizzard diameter to determine weight and TL from diet samples when advanced digestion of Gizzard Shad limits the use of more traditional metrics (TL, backbone length, etc.). [ABSTRACT FROM AUTHOR]

Inferences based on tagged individuals from a population are limited in part by the minimum size of fish that can be tagged. Smaller tags allow a greater proportion of a population to be represented by tagging and should reduce potential tag effects on fish performance. We evaluated different performance metrics of juvenile fall Chinook Salmon Oncorhynchus tshawytscha tagged with 8‐, 9‐, and 12‐mm PIT tags in the Snake River. We did not find evidence that posttagging mortality of 45–49‐mm‐FL fish tagged with 8‐mm tags was higher than the posttagging mortality of larger fish tagged with 9‐ and 12‐mm tags. The incisions of fish tagged with 8‐mm tags using 14‐guage needles healed faster than those of fish tagged with larger tags using 12‐guage needles. For individuals that received 8‐mm tags, growth in length and mass was higher for 45–49‐mm fish than for 50–59‐mm fish and 60‐mm and larger fish. Growth of the larger size‐classes (50–59 and ≥60 mm) was also generally higher for those tagged with 8‐mm tags compared to those tagged with 9‐ and 12‐mm tags, respectively. There were no strong relationships between tag burden (i.e., tag weight expressed as a percentage of fish weight) at the time of tagging and growth metrics for any tag size or fish size‐class. Releases made to compare the detection efficiency of the three tag types in the juvenile fish bypass at Lower Granite Dam, Washington, showed that 99–100% of all fish were detected. Survival of fish from rearing areas to Lower Granite Dam generally increased with fish size and varied by year, but there was no strong evidence of a tag size effect. The 8‐mm PIT tag allowed us to represent a larger portion (i.e., 6.2–24.1%) of the subyearling fall Chinook Salmon population in the Snake River without compromising fish performance or detectability at the dam. [ABSTRACT FROM AUTHOR]

To better understand the reliability of fin clipping as an external mark for early‐summer (<100 mm TL) age‐0 Northern Pike Esox lucius, we experimentally evaluated fin regeneration following complete excision of a pelvic fin over 98 d. The Northern Pike were also marked with a unique visible implant elastomer tag to allow for repeated measures of individuals. Survival, growth, and fin regeneration were evaluated among three treatment groups to determine whether the fish that received a fin clip following anesthetic (n = 17) differed from those that were fin‐clipped without anesthetic (n = 17) and unclipped control fish (n = 10). The fish were distributed proportionally by treatment group between two outdoor rearing tanks, but one of the rearing tanks experienced a mortality event from an unknown source. Consequently, the evaluations were based on the 25 surviving Northern Pike, with treatment‐specific sample sizes of seven fish for both the control and nonanesthetic treatments and 11 fish from the anesthetized treatment group. Despite the mortality event in one of the two rearing tanks, survival was similar among the three treatment groups when the rearing tanks were evaluated independently and pooled rearing‐tank data revealed no difference in growth rates between fin‐clipped and unclipped control fish for TL and weight. By day 46, the clipped fin had regenerated to approximately 80% the length of the unclipped counterpart and by the end of the study many of the clipped fins were nearly indistinguishable from the unclipped fins. This represents the fastest age‐0 esocid fin regeneration reported. The results from this study demonstrate that marking early‐summer age‐0 Northern Pike during the growing season with pelvic fin clips is likely inappropriate for mark–recapture studies that span beyond 3 months. The use of fin clips on age‐0 Northern Pike should be restricted to shorter‐term studies, or an alternative marking technique should be adopted for the reliable identification of the fish. [ABSTRACT FROM AUTHOR]

We conducted laboratory experiments to parameterize a bioenergetics model for wild Bull Trout Salvelinus confluentus, estimating the effects of body mass (12-1,117 g) and temperature (3-20°C) on maximum consumption (Cmax) and standard metabolic rates. The temperature associated with the highest Cmax was 16°C, and Cmax showed the characteristic dome-shaped temperature-dependent response. Mass-dependent values of Cmax (N = 28) at 16°C ranged from 0.03 to 0.13 g·g-1·d-1. The standard metabolic rates of fish (N = 110) ranged from 0.0005 to 0.003 g·O2·g-1·d-1 and increased with increasing temperature but declined with increasing body mass. In two separate evaluation experiments, which were conducted at only one ration level (40% of estimated Cmax), the model predicted final weights that were, on average, within 1.2 ± 2.5% (mean ± SD) of observed values for fish ranging from 119 to 573 g and within 3.5 ± 4.9% of values for 31-65 g fish. Model-predicted consumption was within 5.5 ± 10.9% of observed values for larger fish and within 12.4 ± 16.0% for smaller fish. Our model should be useful to those dealing with issues currently faced by Bull Trout, such as climate change or alterations in prey availability. [ABSTRACT FROM AUTHOR]

Three common cross-sectional catch-curve methods for estimating total mortality rate (Z) are the Chapman–Robson, regression, and Heincke estimators. There are five unresolved methodological issues: (1) which is the best estimator, (2) how one should determine the first age-group to use in the analysis, (3) how the variance estimators perform; and, for regression estimators, (4) how the observations should be weighted, including (5) whether and how the oldest ages should be truncated. We used analytical methods and Monte Carlo simulation to evaluate the three catch-curve methods, including unweighted and weighted versions of the regression estimator. We evaluated four criteria for specifying the first age-class used. Regression estimators were evaluated with four different methods of right data truncation. Heincke's method performed poorly and is generally not recommended. The two-tailed χ2test and one-tailedz-test for full selectivity described by Chapman and Robson did not perform as well as simpler criteria and are not recommended. Estimates with the lowest mean square error were generally provided by (1) the Chapman–Robson estimator with the age of full recruitment being the age of maximum catch plus 1 year and (2) the weighted regression estimator with the age of full recruitment being the age of maximum catch and with no right truncation. Differences in performance between the two methods were small (<6% ofZ). The Chapman–Robson estimator of the variance ofhad large negative bias when not corrected for overdispersion; once corrected, it performed as well as or better than all other variance estimators evaluated. The regression variance estimator is generally precise and slightly negatively biased. We recommend that the traditional Chapman–Robson approach be corrected for overdispersion and used routinely to estimateZ. Weighted linear regression may work slightly better but is completely ad hoc. Unweighted linear regression should no longer be used for analyzing catch-curve data. Received November 30, 2011; accepted July 4, 2012 [ABSTRACT FROM PUBLISHER]

Relative weight (Wr ) is an index of condition that enables evaluation of the well-being of fish by comparing the actual weight of a specimen with the ideal weight of a specimen of the same species and the same length that is in good physiological condition (i.e., the standard weight [Ws ]). This index was primarily developed to assess the status of sport fishes. Recently, however, many authors have encouraged the use of this index as a fisheries assessment tool for nongame species as well, especially those that are endangered or threatened. Length and weight data on brook chub Squalius lucumonis, an Italian endemic species listed as endangered by the International Union for the Conservation of Nature, were collected across its area of distribution and used to compute a standard weight (Ws ) equation by means of the empirical percentile method. The Ws equation thus obtained (log10 Ws = –7.75 + 5.75 log10[total length {TL}] – 0.66 [log10TL]2; TL range of application = 90–210 mm) was not biased by length and is recommended as a way to compute Wr for brook chub. Received October 11, 2011; accepted January 12, 2012 [ABSTRACT FROM PUBLISHER]

The study of movement in catfish via telemetry can be problematic because of transmitter expulsion. Information regarding transmitter retention in blue catfish Ictalurus furcatus is limited. We examined transmitter retention and physical condition after implantation in adult blue catfish (≥600 mm) for two surgical implantation methods. Fifteen fish were implanted with Vemco V16 transmitters that were left free floating in the abdominal cavity (traditional method). Another fifteen fish were implanted with capsules constructed to duplicate externally mounted Vemco V16 transmitters. These capsules were implanted in the abdominal cavity and then anchored to the pectoral girdle using sterile pseudo-monofilament suture (modified method). Fish were held in a flow-through circular tank for 244 d following surgery. Sixteen fish expelled their capsules, 10 from the traditional procedure and 6 from the modified procedure. Expulsions were observed between 23 and 243 d post surgery. The condition of fish with retained transmitters after 244 d, as measured by relative weight, was significantly higher for fish in the traditional treatment group. Gross necropsy revealed that retained traditionally implanted transmitters were free floating in the abdominal cavity with no visible interaction with internal organ structures. In the modified surgery group, retained transmitters remained tethered to the pectoral girdle but were located in various positions within the abdominal cavity, including encased in the intestine or stomach, and pushed through the body wall. Our study demonstrated unacceptable health effects associated with the modified procedure. We do not recommend it as a transmitter attachment method for telemetry studies of catfish movement. Further study is suggested to better determine the rates of retention associated with the traditional procedure that was tested. Received August 2, 2011; accepted January 4, 2012 [ABSTRACT FROM AUTHOR]

We collected and compiled length and weight information from four countries and one commonwealth to develop standard weight ( Ws) equations for three amphidromous fish species native to the Caribbean and Gulf of Mexico regions: mountain mullet ( N = 9,768 individuals, 52 populations), river goby ( N = 1,847 individuals, 62 populations), and bigmouth sleeper ( N = 2,983 individuals, 53 populations). Linear and quadratic Ws equations for three quartiles (25%, median, 75%) are presented for these three species. The length-weight relationship from eight lentic bigmouth sleeper populations was significantly different from that of lotic populations, reflecting higher weights of juvenile fish (<70 mm total length) in lentic environments. Thus, independent Ws equations were developed for lotic populations of bigmouth sleepers. Ws equations were not developed from lentic bigmouth sleeper populations alone due to the low number of applicable populations caused by life history constraints; the equation from combined lentic and lotic populations is suggested for application to lentic bigmouth sleeper populations. These morphometric relationships for amphidromous fishes may improve the ability to assess existing and potential sport fisheries and allow ecological assessment based on fish condition. [ABSTRACT FROM AUTHOR]

We examined differences in sex specific growth and weight-length relationships for five Minnesota populations of black crappies Pomoxis nigromaculatus. Male black crappies typically grew slightly faster than females, but observed differences minmean total lengths (TLs) at age were always 15 mm or less and were typically less than 10 mm. We detected few differences in log10(weight)-log10(TL) regressions between sexes, and predicted weights at 200 and 250 mm differed between sexes by less than 10 g. Our results indicate that biologists are justified in pooling sexes when estimating population metrics such as growth and condition because the minor differences in growth and weight-length relationships we observed would be unlikely to affect management decisions. Furthermore, while our evaluation did not specifically examine angler harvest selectivity, the small differences in growth and weight-length relationships observed between sexes seemed unlikely to promote sex selective angler harvest within the lakes we examined. However, it remains possible that male growth advantages of more than 10 mm may promote selective removal of male fish in black crappie fisheries regulated by minimum length limits, where anglers may use the minimum length limit as a target when selecting fish for harvest and are more likely to measure individual fish. [ABSTRACT FROM AUTHOR]

Physiological status of wild fish is inherently variable in time and space, and investigators need to understand how this variation affects the interpretation of condition indices. Our objective was to describe the relationship of relative weight (Wr) to several indicators of nutritional status (lipid, protein, and water content, and weights of internal organs) in two populations of bluegill Lepomis macrochirus and see how well this relationship performed when tested against an independent data set, a third population. We used four samples from the third population to evaluate the relationship of Wr to nutritional status through the annual cycle. The regression model relating Wr to the component variables was highly significant (R² = 0.573, F = 14.97, P < 0.001). The most influential variables in the model were liver--somatic index and viscerosomatic index. In the testing data, mean bias was significantly greater than zero in three of four cases, and unexplained variance was much greater than in the model-building data in two of four cases. Most prediction errors were noticeably positive and tended to be greater at lower predicted Wr. The model-testing exercise showed that the relationships of condition indices to nutritional variables in wild fish are imprecise and qualitative. Bluegill Wr should be interpreted cautiously because of its imprecise relationship to compositional variables and the many potentially confounding factors. In this regard, we offer several recommendations for the use and interpretation of Wr in wild fishes. [ABSTRACT FROM AUTHOR]

We used quantile regression to compare the body condition of walleye Sander vitreus and white bass Morone chrysops before (1980-1988) and after (1989-2004) the establishment of alewives Alosa pseudoharengus in Lake McConaughy, Nebraska. Higher quantiles (percentiles = 100% x quantiles [0, 1]) of weight (W) at the same total length (TL) were indicative of better body condition in an allometric growth model that included separate slopes and intercepts for the before and after groups. All quantiles of walleye weights by TL increased in the years after alewife introduction, ranging from 1.01 to 1.12 times weights in the years before alewife introduction, with greatest increases for the lower (<0.50) quantiles and greater TLs. Quantiles up to 0.25 (the lowest 25th percentiles) of white bass weights were reduced in years after alewife introduction for TLs less than 300 ram, ranging from 0.78 to 0.98 times weights in the years before alewife introduction. However, quantiles greater than or equal to 0.50 (the upper 50th percentiles) of white bass weights increased for all TLs, ranging from 1.01 to 1.06 times the pre-1988 weights. A three-group analysis, which improved the model fit for longer white bass, indicated a reduction (0.80-1.0) in white bass body condition across all TLs in the first 2 years (1989-1990) after alewife introduction, whereas body condition actually improved (1.02-1.12) across all TLs in later years (1991-2004). Thus, after the establishment of alewives in 1988, walleye body condition improved for all fish at all lengths (the greatest improvement occurring among fish in poorer condition), whereas white bass body condition was initially reduced for all fish at all lengths for 2 years and improved in subsequent years. The approach that we developed for comparing fish body condition before and after a management action in Lake McConaughy could be applied to other weight-length data sets typically evaluated with relative weight indices. [ABSTRACT FROM AUTHOR]

Due to the increasing interest in biochemical indices such as the RNA-DNA ratio used to measure fish growth, fish often need to be stored frozen with dry ice (i.e., -80°C). The objectives of this study were to (1) quantify the effects of dry ice on both the length and weight of larval and juvenile yellow perch Perca flavescens preserved for storage periods of 15 d and 7-8 months, (2) compare these effects with those of two commonly used preservatives (a 10% solution of formalin and a 75% solution of ethanol), and (3) provide equations to convert the lengths and weights of larval and juvenile yellow perch preserved with dry ice, formalin, and ethanol back to their initial unpreserved values. For all preservation methods, fish weight was more affected than length. The smallest length reduction was observed with formalin (short term: 2.1% and 0.1% for larvae and juveniles, respectively; long term: 10.1% and 1.2%), followed by dry ice (short term: 4.0% and 1.4%; long term: 7.2% and 3.9%) and ethanol (short term: 9.6% and 1.2%; long term: 11.7% and 1.2%). The smallest weight reduction was also observed with formalin (short term: 21.9% and 2.2%; long term: 23.2% and 3.9%), followed by dry ice (short term: 54.0% and 11.1%; long term: 52.8% and 8.4%) and ethanol (short term: 61.1% and 22.0%; long term: 66.0% and 26.0%). Except for one case, all of the regression equations that were built to convert the lengths and weights of larval and juvenile yellow perch preserved with dry ice, formalin, and ethanol back to initial measurements were highly significant. [ABSTRACT FROM AUTHOR]

Fisheries assessment tools originally created for use with game fish populations are now helping to assess individual nongame species and to evaluate fish communities. Length and weight measurements of individuals within a species can be summarized into condition indices that give insight into the health and condition of the individual and the aquatic community. Such data (weight [g] and total length [TL, mm]) were obtained for 105 populations of bridgelip suckers Catostomus columbianus and 135 populations of largescale suckers C. macrocheilus from three northwestern states. These data were used to develop standard weight (Ws) equations via the regression-line percentile (RLP) and empirical percentile (EmP) methods. Length constraints were 130-460 mm TL for bridgelip suckers and 1704540 mm TL for largescale suckers. The data set was limited by TL constraints and split into development and validation sets. The RLP method yielded the following W equations: log10W s = -5.01699 + 3.02648·log10TL for bridgelip suckers and log10Ws = -4.94684 + 2.99720-log10TL for largescale suckers. Equations based on the EmP method were log10Ws = -5.09721 + 3.04947·log10TL for bridgelip suckers and log10Ws = -5.2586 + 3.12136·log10TL for largescale suckers. For both species, the relative weights produced from RLP and EmP equations differed by less than 10%. However, differences were inconsistent over the length range, indicating a length-related bias. Based on this assessment, use of EmP Ws equations for bridgelip suckers and largescale suckers is recommended. Further, the EmP method should be used to establish new Ws equations. [ABSTRACT FROM AUTHOR]

We compared two external transmitter styles on two size-classes of bluegills Lepomis macrochirus (laterally compressed) and yellow perch Perca flavescens (fusiform) to determine the effects of (1) even distribution of transmitter weight and (2) transmitter weights above and below the recommended 2% of fish body weight. Fish were collected, acclimated for 3 weeks before transmitter attachment, measured for length and weight, Floy tagged, and randomly assigned to treatments (single-sided transmitter, saddle transmitter, and control). Weight and length of individual fish were recorded every 5 d through day 20 and every 10 d through day 40. On day 40, we classified tag migration, wound redness, and organosomatic indices. Saddle transmitters required the longest handling time of all treatments and did not outperform single-sided transmitters. On day 40, only small yellow perch had gained more weight with saddle transmitters than with single-sided transmitters. Transmitters that exceeded 2% of fish weight slowed bluegill growth, whereas transmitters that were less than 2% of fish weight negatively affected yellow perch growth. Our results suggest that even the distribution of external transmitter weight may be less important than the method of attachment and transmitter weight. Development of improved attachment methods for saddle transmitters may prove beneficial for use in long-term studies of small, fusiform fish. [ABSTRACT FROM AUTHOR]

Little information exists regarding the biological attributes and stock dynamics of flathead catfish Pylodictis olivaris in lotic systems throughout the northern United States. We examined the population abundance, annual survival, growth, condition, size structure, and age structure of flathead catfish in the lower St. Joseph River, Michigan, to direct future management efforts in this system and increase our knowledge of northern flathead catfish stocks. Fish were collected by means of electrofishing during June through September 2002 and 2003. Population abundance was estimated at 5,452 individuals (range, 3,985-7,277 fish), and annual survival was estimated at 67%. Analysis of pectoral spine cross sections revealed that growth was greatest for fish younger than age 6 (range, 83-98 mm/year) and decreased among older age-classes (range, 18-70 mm/year). Relative weight was greatest for individuals less than 300 mm total length (TL; 115%) and declined with increasing fish length. The size structure and age structure of flathead catfish were dominated by fish less than 400 mm TL and younger than age 4 (89% and 79%, respectively), although individuals greater than 1,100 mm TL and up to age 17 were present in the population. Relative stock density estimates indicated that 58% of fish greater than the minimum stock size were of quality length, while flathead catfish of preferred, memorable, and trophy sizes represented 28, 7, and 1% of fish collected, respectively. Despite their presence on the northern fringe of the species' geographic distribution, the flathead catfish in the lower St. Joseph River exhibited biological characteristics and stock dynamics that were similar to those reported for other lightly exploited stocks throughout the midwestern United States. [ABSTRACT FROM AUTHOR]

Our objective was to compare the ability of brown bullheads Ameiurus nebulosus to tolerate the implantation of ultrasonic transmitters with different coatings. A total of 14 brown bullheads were surgically implanted with ultrasonic transmitters; 7 transmitters were coated with paraffin wax and 7 with Scotchcast, an inert epoxy resin. Six brown bullheads were held as controls with no surgical procedures. Fish were held for 75 d in a flow-through, gravity-filtered series of tanks and monitored for transmitter expulsion, growth (i.e., percent relative weight change), condition (i.e., relative weight), and mortality. All fish with paraffin-coated implants retained their transmitters for the duration of the experiment, whereas two fish with Scotchcast implants expelled their transmitters within 50 d. All fish in the experiment survived, and the implanted fish exhibited growth and condition similar to those of the controls. On the basis of these results, we conclude that brown bullheads tolerate implantation of paraffin-coated transmitters and this attachment method may be used for brown bullheads in telemetric field studies. [ABSTRACT FROM AUTHOR]

We used information from an angler recognition program to assess the relationship between lake-record weights of freshwater fishes captured by Texas anglers and two predictors of fish production and growth: reservoir surface area and growing-season length. The lake-record weights of two species, largemouth bass Micropterus salmoides and flathead catfish Pylodictis olivaris, were directly related to the logarithm of surface area. The record weights of all species studied were unrelated to growing-season length. Regardless of the statistical significance of individual correlations, there was a significant excess of positive correlations across all species between lake-record weights of fish and log surface area. This indicates the presence of a general relationship between the record weights of fish and reservoir area. Our results suggest that record weights of fish may be constrained by reservoir surface area. [ABSTRACT FROM AUTHOR]

Standard weight (Ws) equations have been used extensively to examine body condition in sport fishes. However, development of these equations for non-game fishes has only recently been emphasized. We used the regression-line-percentile technique to develop standard weight equations for four rare desert fishes: flannelmouth sucker Catostomus latipinnis, razorback sucker Xyrauchen texanus, roundtail chub Gila robusta, and humpback chub G. cypha. The Ws equation for flannelmouth suckers of 100-690 mm total length (TL) was developed from 17 populations: log10Ws, = -5.180 + 3.068 log10Ts. The Ws equation for razorback suckers of 110-885 mm TL was developed from 12 populations: log10Ws = -4.886 + 2.985 log10TL. The Ws equation for roundtail chub of 100-525 mm TL was developed from 20 populations: log10Ws = -5.065 + 3.015 log10TL. The Ws equation for humpback chub of 120495 mm TL was developed from 9 populations: log10Ws = -5.278 + 3.096 log10TL. These equations meet criteria for acceptable standard weight indexes and can be used to calculate relative weight, an index of body condition. [ABSTRACT FROM AUTHOR]

Length and weight data were obtained from 46 populations of blue suckers Cycleptus elongates (N = 8,811 fish) across the species' geographic distribution to develop a standard weight (Ws) equation. The Ws equation was derived using the empirical percentile technique applied to fish between 240 and 809 mm total length (TL). We calculate a quadratic model and a linear model to derive Ws. The proposed 75th-percentile quadratic equation (metric units) is log10Ws =-2.980+0.977 log10TL+0.461 (log10TL)², where Ws is expressed in grams and TL is expressed in millimeters. The proposed English-equivalent 75th-percentile quadratic Equation is log10Ws = -3.354 + 2.273 log10 TL + 0.461 (log10TL)², where Ws is expressed in pounds and TL is expressed in inches. The 75th-percentile linear equation (metric units) is log10Ws = -6.301 + 3.456 log10TL, and the proposed English equivalent is log10Ws = -4.104 + 3.456 log10TL. [ABSTRACT FROM AUTHOR]

The author comments on an article that explored how to estimate quartiles using the Blom method. He explains that the creation of standard weight equations using empirical data requires computation of quartiles derived from samples of mean weights of fish in a given length-class. He claims that the use of the Blom estimator for the third quartile will lessen bias in estimates and explains the computational algorithm.