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At least 1,315 records · Page 73Linked to original sources
USGS2005

Low summer water temperatures influence occurrence of naturalized salmonids across a mountain watershed

We investigated relationships between the absence of salmonids and low summer water temperatures across a 150-km2 Rocky Mountain watershed. A model predicting maximum July water temperature (MJT) from measurements of perennial stream length, wetted width, and midrange basin elevation was developed from temperature data obtained at 20 sites across the watershed. The model was used to predict MJT in 75 reaches across the watershed where salmonids were sampled. The lowest predicted MJT in reaches where age-0 and juvenile-adult brook trout Salvelinus fontinalis were observed was 9??C. The lowest predicted MJT in reaches where age-0 progeny of the genus Oncorhynchus spp. (i.e., rainbow trout O. mykiss or cutthroat trout O. clarkii) were observed was 13??C and where Oncorhynchus spp. adults where observed was 12??C. The probability of occurrence of both age-0 and adult brook trout and Oncorhynchus spp. increased as MJT increased above these thresholds. Our results indicate that low MJT in some portions of a mountain watershed can be related to the absence of salmonids. Consequently, data on MJT may provide managers with a means of assessing where summer water temperatures are not suitable for establishment of naturalized salmonid populations. ?? Copyright by the American Fisheries Society 2005.

North American Journal of Fisheries Management↗
USGS2005

A new method to compute standard-weight equations that reduces length-related bias

We propose a new method for developing standard-weight (Ws) equations for use in the computation of relative weight (Wr) because the regression line-percentile (RLP) method often leads to length-related biases in Ws equations. We studied the structural properties of W s equations developed by the RLP method through simulations, identified reasons for biases, and compared Ws equations computed by the RLP method and the new method. The new method is similar to the RLP method but is based on means of measured weights rather than on means of weights predicted from regression models. The new method also models curvilinear W s relationships not accounted for by the RLP method. For some length-classes in some species, the relative weights computed from Ws equations developed by the new method were more than 20 Wr units different from those using Ws equations developed by the RLP method. We recommend assessment of published Ws equations developed by the RLP method for length-related bias and use of the new method for computing new Ws equations when bias is identified. ?? Copyright by the American Fisheries Society 2005.

North American Journal of Fisheries Management↗
USGS2006

Effects of live-well conditions on mortality and largemouth bass virus prevalence in largemouth bass caught during summer tournaments

We evaluated the effect of improved live-well conditions and the interaction of tournament stress and largemouth bass virus (LMBV) on tournament-associated mortality of largemouth bass Micropterus salmoides caught during 12 summer tournaments. Improvements in live-well conditions (reduction in water temperature by 2-5??C; addition of NaCl; continuous aeration) significantly reduced initial mortality of largemouth bass from 7% to 3% (F 1,11 = 10.29, P < 0.01). However, postrelease mortality of fish held for 5 d in net-pens or raceways was not reduced by the improved live-well conditions and averaged 76% for all tournament fish (F1,11 = 0.09, P = 0.77). The percentage of angler-caught fish infected with LMBV at the end of tournaments (14%) was significantly higher (P = 0.05) than the percentage infected in the general population (7%). The percentage of LMBV-infected fish increased during the post-tournament retention period to 64% for fish from live wells with improved conditions and 70% for fish from control live wells. Reference fish collected by electrofishing and held with tournament fish for 5 d also had high mortality (59%) and LMBV prevalence (47%), but these variables were significantly lower than those for tournament fish (mortality: F 2,30 = 3.63, P = 0.04; prevalence [Cochran-Mantel-Haenszel test]: P < 0.01). Many of the fish also had bacterial diseases during the post-tournament period, so the effect of LMBV on postrelease mortality could not be determined. However, the higher postrelease mortality of tournament and reference fish in our study relative to that observed in previous tournaments on lakes presumed free of LMBV suggests that this newly discovered pathogen influences measurement of post-tournament mortality. Increases in LMBV prevalence after typical fishing tournaments without prolonged post-tournament fish confinement will probably be lower than those we observed, but further research on the effects of LMBV on fish released from tournaments is warranted. ?? Copyright by the American Fisheries Society 2006.

North American Journal of Fisheries Management↗
USGS2006

Survival of largemouth bass from populations infected with largemouth bass virus and subjected to simulated tournament conditions

Mortality was measured for largemouth bass Micropterus salmoides in simulated tournaments conducted at 26??C to determine whether an easily accomplished live-well management protocol reduced mortality. Treatment fish, which received the live-well management protocol, were held for 8 h in live wells at 23??C with water containing more than 5 mg of dissolved oxygen/L and 0.3% salt (NaCl). Control fish, were confined for 8 h in live wells at 26??C (ambient temperature) with dissolved oxygen fluctuating from 3 to 5 mg/L and no salt, which simulated the live-well management practices used by largemouth bass tournament anglers. Mortality after live-well confinement was 0% for both treatment and control fish, and mortality during the first 24 h after the simulated tournaments was 2.5%. Mortality of fish observed for up to 5 d after the simulated tournaments was high for treatment fish (mean = 75%; SE = 16%) and control fish (mean = 85%; SE = 11%), and we conclude that the treatment conditions did not reduce postrelease mortality. We suggest that the unusually high posttournament mortality was related to largemouth bass virus infections. ?? Copyright by the American Fisheries Society 2006.

North American Journal of Fisheries Management↗
USGS2006

Improving the design of acoustic and midwater trawl surveys through stratification, with an application to Lake Michigan prey fishes

Reliable estimates of fish biomass are vital to the management of aquatic ecosystems and their associated fisheries. Acoustic and midwater trawl surveys are an efficient sampling method for estimating fish biomass in large bodies of water. To improve the precision of biomass estimates from combined acoustic and midwater trawl surveys, sampling effort should be optimally allocated within each stage of the survey design. Based on information collected during fish surveys, we developed an approach to improve the design of combined acoustic and midwater trawl surveys through stratification. Geographic strata for acoustic surveying and depth strata for midwater trawling were defined using neighbor-restricted cluster analysis, and the optimal allocation of sampling effort for each was then determined. As an example, we applied this survey stratification approach to data from lakewide acoustic and midwater trawl surveys of Lake Michigan prey fishes. Precision of biomass estimates from surveys with and without geographic stratification was compared through resampling. Use of geographic stratification with optimal sampling allocation reduced the variance of Lake Michigan acoustic biomass estimates by 77%. Stratification and optimal allocation at each stage of an acoustic and midwater trawl survey should serve to reduce the variance of the resulting biomass estimates.

North American Journal of Fisheries Management↗
USGS2005

Distribution and abundance of nonnative fishes in streams of the western United States

This report presents data from one of the largest standardized stream surveys conducted in he western United States, which shows that one of every four individual fish in streams of 12 western states are nonnative. The states surveyed included Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington, and Wyoming. The most widely distributed and abundant nonnative fishes in the western USA were brook trout Salvelinus fontinalis, brown trout Salmo trutta, rainbow trout Oncorhynchus mykiss, common carp Cyprinus carpio, smallmouth bass Micropterus dolomieu, largemouth bass M. salmoides, green sunfish Lepomis cyanellus, fathead minnow Pimephales promelas, yellow perch Percaflavescens, yellow bullhead Ameiurus natalis, cutthroat trout O. clarkii, western mosquitofish Gambusia affinis, golden shiner Notemigonus crysoleucas, channel catfish Ictalurus punctatus, and red shiner Cyprinella lutrensis. The greatest abundance and distribution of nonnative fishes was in interior states, and the most common nonnatives were introduced for angling. Nonnative fishes were widespread in pristine to highly disturbed streams influenced by all types of land use practices. We present ranges in water temperature, flow, stream order, riparian cover, human disturbance, and other environmental conditions where the 10 most common introduced species were found. Of the total western U.S. stream length bearing fish, 50.1% contained nonnative fishes while 17.9% contained physical environment that was ranked highly or moderately disturbed by humans. Introduced fishes can adversely affect stream communities, and they are much more widespread in western U.S. streams than habitat destruction. The widespread distribution and high relative abundance of nonnative fishes and their documented negative effects suggest their management and control should elicit at least as much attention as habitat preservation in the protection of native western U.S. stream biota. ?? Copyright by the American Fisheries Society 2005.

North American Journal of Fisheries Management↗
USGS2006

Abundance trends and status of the Little Colorado River population of humpback chub

The abundance of the Little Colorado River population of federally listed humpback chub Gila cypha in Grand Canyon has been monitored since the late 1980s by means of catch rate indices and capture-recapture-based abundance estimators. Analyses of data from all sources using various methods are consistent and indicate that the adult population has declined since monitoring began. Intensive tagging led to a high proportion (>80%) of the adult population being marked by the mid-1990s. Analysis of these data using both closed and open abundance estimation models yields results that agree with catch rate indices about the extent of the decline. Survival rates for age-2 and older fish are age dependent but apparently not time dependent. Back-calculation of recruitment using the apparent 1990s population age structure implies periods of higher recruitment in the late 1970s to early 1980s than is now the case. Our analyses indicate that the U.S. Fish and Wildlife Service recovery criterion of stable abundance is not being met for this population. Also, there is a critical need to develop new abundance indexing and tagging methods so that early, reliable, and rapid estimates of humpback chub recruitment can be obtained to evaluate population responses to management actions designed to facilitate the restoration of Colorado River native fish communities. ?? Copyright by the American Fisheries Society 2006.

North American Journal of Fisheries Management↗
USGS2007

Year-class formation of upper St. Lawrence River northern pike

Variables associated with year-class formation in upper St. Lawrence River northern pike Esox lucius were examined to explore population trends. A partial least-squares (PLS) regression model (PLS 1) was used to relate a year-class strength index (YCSI; 1974-1997) to explanatory variables associated with spawning and nursery areas (seasonal water level and temperature and their variability, number of ice days, and last day of ice presence). A second model (PLS 2) incorporated four additional ecological variables: potential predators (abundance of double-crested cormorants Phalacrocorax auritus and yellow perch Perca flavescens), female northern pike biomass (as a measure of stock-recruitment effects), and total phosphorus (productivity). Trends in adult northern pike catch revealed a decline (1981-2005), and year-class strength was positively related to catch per unit effort (CPUE; R2 = 0.58). The YCSI exceeded the 23-year mean in only 2 of the last 10 years. Cyclic patterns in the YCSI time series (along with strong year-classes every 4-6 years) were apparent, as was a dampening effect of amplitude beginning around 1990. The PLS 1 model explained over 50% of variation in both explanatory variables and the dependent variable, YCSI first-order moving-average residuals. Variables retained (N = 10; Wold's statistic ??? 0.8) included negative YCSI associations with high summer water levels, high variability in spring and fall water levels, and variability in fall water temperature. The YCSI exhibited positive associations with high spring, summer, and fall water temperature, variability in spring temperature, and high winter and spring water level. The PLS 2 model led to positive YCSI associations with phosphorus and yellow perch CPUE and a negative correlation with double-crested cormorant abundance. Environmental variables (water level and temperature) are hypothesized to regulate northern pike YCSI cycles, and dampening in YCSI magnitude may be related to a combination of factors, including wetland habitat changes, reduced nutrient loading, and increased predation by double-crested cormorants. ?? Copyright by the American Fisheries Society 2007.

North American Journal of Fisheries Management↗
USGS2006

Posttournament survival and dispersal of adult striped bass

We conducted a telemetry study from November 2004 to June 2005 at J. Strom Thurmond Reservoir in South Carolina and Georgia to quantify posttournament survival of striped bass and their dispersal from tournament weigh-in sites. During November-December 2004, 30 adult striped bass weighing 1.0-10.0 kg were angled, held in "striped bass tube" live-holding systems for 2-5 h, transported to a predetermined weigh-in and release site, and surgically implanted with telemetry transmitters. All striped bass survived transport, recovered from the surgical procedure, and were immediately released. The postrelease survival rate after 120 d was 87%. Surviving striped bass dispersed from the release site within 2-9 d. Fifty-four percent returned to their capture sites. Capture, holding, displacement, and weigh-in appeared to have no long-term adverse affects on behavior. Live release of striped bass may now be a viable option after tournaments during periods of cool water temperatures. ?? Copyright by the American Fisheries Society 2006.

North American Journal of Fisheries Management↗
USGS2006

Dietary calcein marking of brook trout, Atlantic salmon, yellow perch, and coho salmon scales

Brook trout Salvelinus fontinalis, Atlantic salmon Salmo salar, coho salmon Oncorhynchus kisutch, and yellow perch Perca flavescens fed calcein for 5 d showed characteristic calcein scale marks 7-10 d postmarking. In fish fed 0.75 or 1.25 g of calcein per kilogram of feed, the percentage of fish that exhibited a calcein mark was 100% in brook trout, 93-98% in Atlantic salmon, 60% in yellow perch, and 0% in coho salmon. However, when coho salmon were fed 5.25 g calcein/kg feed, 100% marking was observed 7-10 d postmarking. Brook trout were successfully marked twice with distinct bands when fed calcein 5 months apart. Brook trout scale pixel luminosity increased as dietary calcein increased in experiment 2. For the second calcein mark, scale pixel luminosity from brook trout fed 1.25 g calcein/kg feed was numerically higher (P < 0.08) than scales from fish fed 0.75 g calcein/kg feed. Mean pixel luminosity of calcein-marked Atlantic salmon scales was 57.7 for fish fed 0.75 g calcein/kg feed and 55.2 for fish fed 1.25 g calcein/kg feed. Although feed acceptance presented a problem in yellow perch, these experiments provide evidence that dietary calcein is a viable tool for marking fish for stock identification. ?? Copyright by the American Fisheries Society 2006.

North American Journal of Fisheries Management↗
USGS2007

Population dynamics and angler exploitation of the unique muskellunge population in Shoepack Lake, Voyageurs National Park, Minnesota

A unique population of muskellunge Esox masquinongy inhabits Shoepack Lake in Voyageurs National Park, Minnesota. Little is known about its status, dynamics, and angler exploitation, and there is concern for the long-term viability of this population. We used intensive sampling and mark-recapture methods to quantify abundance, survival, growth, condition, age at maturity and fecundity and angler surveys to quantify angler pressure, catch rates, and exploitation. During our study, heavy rain washed out a dam constructed by beavers Castor canadensis which regulates the water level at the lake outlet, resulting in a nearly 50% reduction in surface area. We estimated a population size of 1,120 adult fish at the beginning of the study. No immediate reduction in population size was detected in response to the loss of lake area, although there was a gradual, but significant, decline in population size over the 2-year study. Adults grew less than 50 mm per year, and relative weight (W r) averaged roughly 80. Anglers were successful in catching, on average, two fish during a full day of angling, but harvest was negligible. Shoepack Lake muskellunge exhibit much slower growth rates and lower condition, but much higher densities and angler catch per unit effort (CPUE), than other muskellunge populations. The unique nature, limited distribution, and location of this population in a national park require special consideration for management. The results of this study provide the basis for assessing the long-term viability of the Shoepack Lake muskellunge population through simulations of long-term population dynamics and genetically effective population size. ?? Copyright by the American Fisheries Society 2007.

Minnesota↗
USGS2006

Random versus fixed-site sampling when monitoring relative abundance of fishes in headwater streams of the upper Colorado River basin

Native fishes of the upper Colorado River basin (UCRB) have declined in distribution and abundance due to habitat degradation and interactions with normative fishes. Consequently, monitoring populations of both native and nonnative fishes is important for conservation of native species. We used data collected from Muddy Creek, Wyoming (2003-2004), to compare sample size estimates using a random and a fixed-site sampling design to monitor changes in catch per unit effort (CPUE) of native bluehead suckers Catostomus discobolus, flannelmouth suckers C. latipinnis, roundtail chub Gila robusta, and speckled dace Rhinichthys osculus, as well as nonnative creek chub Semotilus atromaculatus and white suckers C. commersonii. When one-pass backpack electrofishing was used, detection of 10% or 25% changes in CPUE (fish/100 m) at 60% statistical power required 50-1,000 randomly sampled reaches among species regardless of sampling design. However, use of a fixed-site sampling design with 25-50 reaches greatly enhanced the ability to detect changes in CPUE. The addition of seining did not appreciably reduce required effort. When detection of 25-50% changes in CPUE of native and nonnative fishes is acceptable, we recommend establishment of 25-50 fixed reaches sampled by one-pass electrofishing in Muddy Creek. Because Muddy Creek has habitat and fish assemblages characteristic of other headwater streams in the UCRB, our results are likely to apply to many other streams in the basin. ?? Copyright by the American Fisheries Society 2006.

North American Journal of Fisheries Management↗
USGS2007

Smallmouth bass and largemouth bass predation on juvenile Chinook salmon and other salmonids in the Lake Washington basin

We assessed the impact of predation by smallmouth bass Micropterus dolomieu and largemouth bass M. salmoides on juveniles of federally listed Chinook salmon Oncorhynchus tshawytscha and other anadromous salmonid populations in the Lake Washington system. Bass were collected with boat electrofishing equipment in the south end of Lake Washington (February-June) and the Lake Washington Ship Canal (LWSC; April-July), a narrow waterway that smolts must migrate through to reach the marine environment. Genetic analysis was used to identify ingested salmonids to obtain a more precise species-specific consumption estimate. Overall, we examined the stomachs of 783 smallmouth bass and 310 largemouth bass greater than 100 mm fork length (FL). Rates of predation on salmonids in the south end of Lake Washington were generally low for both black bass species. In the LWSC, juvenile salmonids made up a substantial part of bass diets; consumption of salmonids was lower for largemouth bass than for smallmouth bass. Smallmouth bass predation on juvenile salmonids was greatest in June, when salmonids made up approximately 50% of their diet. In the LWSC, overall black bass consumption of salmonids was approximately 36,000 (bioenergetics model) to 46,000 (meal turnover consumption model) juveniles, of which about one-third was juvenile Chinook salmon, one-third was coho salmon O. kisutch, and one-third was sockeye salmon O. nerka. We estimated that about 2,460,000 juvenile Chinook salmon (hatchery and wild sources combined) were produced in the Lake Washington basin in 1999; thus, the mortality estimates in the LWSC range from 0.5% (bioenergetics) to 0.6% (meal turnover). Black bass prey mostly on subyearlings of each salmonid species. The vulnerability of subyearlings to predation can be attributed to their relatively small size; their tendency to migrate when water temperatures exceed 15??C, coinciding with greater black bass activity; and their use of nearshore areas, where overlap with black bass is greatest. We conclude that under current conditions, predation by smallmouth bass and largemouth bass has a minor impact on Chinook salmon and other salmonid populations in the Lake Washington system. ?? Copyright by the American Fisheries Society 2007.

North American Journal of Fisheries Management↗
USGS2007

Temperature-mediated differences in bacterial kidney disease expression and survival in Renibacterium salmoninarum-challenged bull trout and other salmonids

Resource managers considering restoration and reconnection of watersheds to protect and enhance threatened populations of bull trout Salvelinus confluentus have little information about the consequences of bacterial kidney disease (BKD) caused by Renibacterium salmoninarum. To better understand the response of bull trout to R. salmoninarum challenge, we conducted several laboratory experiments at two water temperatures. The extent, severity, and lethality of BKD in bull trout were compared with those of similarly challenged lake trout S. namaycush, Arctic char S. alpinus, Chinook salmon Oncorhynchus tshawytscha, and rainbow trout O. mykiss. The lethal dose of bacterial cells necessary to induce 50% mortality (LD50) was 10-fold lower at the 15??C challenge than at the 9??C challenge. Of the species tested, bull trout were relatively resistant to BKD, Arctic char were the most susceptible among Salvelinus species, and Chinook salmon were the most susceptible among Oncorhynchus species tested. Mean time to death was more rapid for all fish tested at 15??C than for fish challenged at 9??C. These results suggest that infection of bull trout with BKD likely poses a low risk to successful restoration of threatened populations. ?? Copyright by the American Fisheries Society 2007.

North American Journal of Fisheries Management↗
USGS2007

Selection of spawning sites by coho salmon in a northern California stream

We assessed the relative importance of various factors contributing to spawning site use by a population of threatened coho salmon Oncorhynchus kisutch in Freshwater Creek, California, and created a predictive model of spawning habitat selection based on logistic regression analysis. We excluded sampling sites that previous studies had established as unsuitable on the basis of depth and substrate criteria and asked why fish chose particular locations and not others in seemingly suitable habitat. We evaluated surface water velocity, depth, substrate size composition, gravel inflow rates, vertical hydraulic gradient, geomorphic channel units, hyporheic water physicochemistry, cover, and proximity to other redds not in sampling sites during the 2004-2005 spawning season. In univariate comparisons with unused sites, coho salmon selected sites with a smaller median particle diameter, a larger percentage of gravel-pebble substrate, and higher gravel inflow rates. Based on multivariate logistic regression, the probability of a site's being used for spawning was best modeled as a positive function of the gravel-pebble fraction of the substrate, location at a pool or run tail, and the presence of existing redds in close proximity to the site. This model explained 38% of the variation in the data and was a better predictor of spawning habitat use than a more traditional model based on depth, velocity, and substrate. Our results highlight the potential importance of social behavior in contributing to habitat selection by spawning salmonids. ?? Copyright by the American Fisheries Society 2007.

North American Journal of Fisheries Management↗
USGS2008

Linking landscapes and habitat suitability scores for diadromous fish restoration in the susquehanna river basin

Dams within the Susquehanna River drainage, Pennsylvania, are potential barriers to migration of diadromous fishes, and many are under consideration for removal to facilitate fish passage. To provide useful input for prioritizing dam removal, we examined relations between landscape-scale factors and habitat suitability indices (HSIs) for native diadromous species of the Susquehanna River. We used two different methods (U.S. Fish and Wildlife Service method: Stier and Crance [1985], Ross et al. [1993a, 1993b, 1997], and Pardue [1983]; Pennsylvania State University method: Carline et al. [1994]) to calculate HSIs for several life stages of American shad Alosa sapidissima, alewives Alosa pseudoharengus, and blueback herring Alosa aestivalis and a single HSI for American eels Anguilla rostrata based on habitat variables measured at transects spaced every 5 km on six major Susquehanna River tributaries. Using geographical information systems, we calculated land use and geologic variables upstream from each transect and associated those data with HSIs calculated at each transect. We then performed canonical correlation analysis to determine how HSIs were linked to geologic and land use factors. Canonical correlation analysis identified the proportion of watershed underlain by carbonate rock as a positive correlate of HSIs for all species and life stages except American eels and juvenile blueback herring. We hypothesize that potential mechanisms linking carbonate rock to habitat suitability include increased productivity and buffering capacity. No other consistent patterns of positive or negative correlation between landscape-scale factors and HSIs were evident. This analysis will be useful for prioritizing removal of dams in the Susquehanna River drainage, because it provides a broad perspective on relationships between habitat suitability for diadromous fishes and easily measured landscape factors. This approach can be applied elsewhere to elucidate relationships between fine- and coarse-scale variables and suitability of habitat for fishes. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗
USGS2008

Detecting the response of fish assemblages to stream restoration: Effects of different sampling designsf

Increased trout production within limited stream reaches is a popular goal for restoration projects, yet investigators seldom monitor, assess, or publish the associated effects on fish assemblages. Fish community data from a total of 40 surveys at restored and reference reaches in three streams of the Catskill Mountains, New York, were analyzed a posteriori to determine how the ability to detect significant changes in biomass of brown trout Salmo trutta, all salmonids, or the entire fish community differs with effect size, number of streams assessed, process used to quantify the index response, and number of replicates collected before and after restoration. Analyses of statistical power (probability of detecting a meaningful difference or effect) and integrated power (average power over all possible ??-values) were combined with before-after, control-impact analyses to assess the effectiveness of alternate sampling and analysis designs. In general, the more robust analyses indicated that biomass of brown trout and salmonid populations increased significantly in restored reaches but that the net increases (relative to the reference reach) were significant only at two of four restored reaches. Restoration alone could not account for the net increases in total biomass of fish communities. Power analyses generally showed that integrated power was greater than 0.95 when (1) biomass increases were larger than 5.0 g/m2, (2) the total number of replicates ranged from 4 to 8, and (3) coefficients of variation (CVs) for responses were less than 40%. Integrated power was often greater than 0.95 for responses as low as 1.0 g/m2 if the response CVs were less than 30%. Considering that brown trout, salmonid, and community biomass increased by 2.99 g/m2 on average (SD= 1.17 g/m2) in the four restored reaches, use of two to three replicates both before and after restoration would have an integrated power of about 0.95 and would help detect significant changes in fish biomass under similar situations. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗
USGS2008

Validation of daily ring deposition in the otoliths of age-0 channel catfish

We developed and validated methods for estimating the daily age of age-0 channel catfish Ictalurus punctatus. Two clutches of channel catfish eggs were hatched in the laboratory; subsequently, one was stocked in a 186-m2 earthen nursery pond and the other in a 757-L outdoor circular tank. Before stocking, subsamples of fish were collected at swim-up and 3 d after swim-up to evaluate early ring formation. Fish were sampled from the pond and tank on eight occasions ranging from 30 to 119 d posthatch. Distinct differences in early ring formation were found between yolk sac and free-swimming larval stages. Mean ring count and known age were closely related for tank- and pond-raised fish, indicating that daily ring deposition occurred in the otoliths of age-0 channel catfish up to 119 d posthatch. The accuracy of daily age estimation was similar between tank and pond samples, and daily ring counts were considerably accurate up to 60 d posthatch. Pond-raised fish were more difficult to age than tank-raised fish, which we attributed to ring compression resulting from slower growth among pond-raised fish after 30 d. The total length of tank- and pond-raised fish was positively related to otolith size; however, the slopes of the relationships between fish length and otolith radius were different between treatments. Therefore, we could not confirm that the relationship between fish length and otolith size was directly proportional for age-0 channel catfish. We encourage researchers to use this aging technique to determine how abiotic and biotic factors influence early life history characteristics and ultimately the population dynamics of catfishes (Ictaluridae). ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗