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We compared the seasonal biomass (??g 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 ??g/L) than in nonwinterkill lakes (13.8-129.4 ??g/L). In summer months (June-July), D. pulex biomass increased in all lakes but was generally higher in winterkill lakes (332.1-469. 3 ??g/L) than in nonwinterkill lakes (88.6-204.2 ??g/L). By September, D. pulex biomass was substantially higher in winterkill lakes (243.8 ??g/L) than in nonwinterkill lakes (1.0 ??g/L). The mean...
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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...
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The management and recovery of populations of bull trout Salvelinus confluentus requires a comprehensive understanding of habitat use across different systems, life stages, and life history forms. To address these needs, we collected microhabitat use and availability data in three fluvial populations of bull trout in eastern Oregon. We evaluated diel differences in microhabitat use, the consistency of microhabitat use across systems and size-classes based on preference, and our ability to predict bull trout microhabitat use. Diel comparisons suggested bull trout continue to use deeper microhabitats with cover but shift into significantly slower habitats during nighttime periods; however, we observed no discrete...
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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...
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We measured the importance of 24 fishing site attributes to Mississippi freshwater anglers. Factor analysis identified four multiattribute factors as important in the selection of fishing location: CLEAN ENVIRONMENT CATCH, COST AND HARVEST and AMENITIES AND SAFETY. In general, the importance of site selection factors differed little among anglers grouped by preferred type of fish, preferred fishing location (lakes and reservoirs, rivers and streams, ponds, or reservoir tailwaters), usual manner of fishing (engine-powered boat, nonpowered boat, or shore), or change in fishing frequency. COST AND HARVEST was more important to anglers with high harvest orientations. We found low correlations between site selection...
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Since the discovery of ruffe Gymnocephalus cernuus in the St. Louis River in 1987, state, federal, and tribal management agencies have sought to slow its spread to areas outside the western end of Lake Superior. A debate over control strategies highlighted uncertainties about seasonal movements of this species between Lake Superior and its western tributaries. One strategy called for eliminating reproducing populations in tributaries on the periphery of the range using chemical piscicides. That strategy rested on the assumption that ruffe congregate in tributaries during a predictable time of year. This study was designed to explore that assumption. Ruffe collections from the Iron and Sand rivers during 1995 indicated...
We measured water temperature at 87 sites in six streams in two different years (1998 and 1999) to test for association with the occurrence of Lahontan cutthroat trout Oncorhynchus clarki henshawi. Because laboratory studies suggest that Lahontan cutthroat trout begin to show signs of acute stress at warm (>22°C) temperatures, we focused on the maximum daily temperature. The maximum daily temperature associated with the occurrence of Lahontan cutthroat trout ranged from 18.9°C to 28.5°C. Occurrence was more likely at colder (<26°C) sites. In two streams, the maximum daily temperature associated with the occurrence of these trout was relatively cool (≤20°C). In these streams, the response to temperature may...
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Since their introduction in the 1970s, Silver Carp Hypophthalmichthys molitrix have spread throughout the Mississippi River basin. Management of any species relies on an accurate understanding of population characteristics and dynamics. However, Silver Carp seasonal sampling variation is unknown. Sampling during periods of peak catch rates would facilitate Silver Carp assessment and management, improving monitoring and removal techniques. The objective of this study was to evaluate adult Silver Carp seasonal sampling variation with boat electroshocking and trammel nets. Silver Carp were collected monthly (April–October) during 2014 and 2015 from four locations in the Des Moines River, Iowa. Trammel nets rarely captured...
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Subyearling fall chinook salmon's Oncorhynchus tshawytscha use of unaltered and riprap habitats in Lake Wallula of the Columbia River was determined with point abundance data collected by electrofishing in May 1994 and 1995. We documented the presence or absence of subyearlings at 277 sample sites and collected physical habitat information at each site. Based on logistic regression, we found that the probability of fish presence was greater in unaltered shoreline habitats than in riprap habitats. Substrate size was the most important factor in determining fish presence, with dominant substrates larger than 256 mm having the lowest probability of fish presence. Water velocity, also included in our model due to its...
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The radiation patterns of three versions of underwater radiotelemetry antennas were measured to compare the relative reception ranges in the horizontal and vertical planes, which are important considerations when designing detection systems. The received signal strengths of an antenna made by stripping shielding from a section of coaxial cable (stripped coax) and by two versions of a dipole antenna were measured at several orientations relative to a dipole transmit antenna under controlled field conditions. The received signal strengths were greater when the transmit and receive antennas were parallel to each other than when they were perpendicular, indicating that a parallel orientation provides optimal detection...
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When choosing a fish marking technique to address fishery related questions, it is important to consider factors that affect mark retention. Calcein, a chemical marking agent, is under investigation for potential use on fish. Two laboratory trials were conducted with calcein-marked lake trout Salvelinus namaycush to determine the effect of artificial sunlight on calcein mark intensity. In trial 1, fish exposed to 18,000 lx for 7 d lost 90% or more of the calcein mark intensity (relative to the colorimetric key, mg/L) on the head, body, ventral region, and pectoral fins relative to mark intensity in fish that were maintained in darkness. In trial 2, light intensity was reduced 2.5-3.0-fold. After 7 d of light exposure,...
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Approximately 22% of the waters of the Merritt Island National Wildlife Refuge, which encompasses the Kennedy Space Center, Florida, have been closed to public access and fishing since 1962. These closed areas offer an opportunity to test the effectiveness of 'no-take' sanctuaries by analyzing two replicated estuarine areas. Areas open and closed to fishing were sampled from November 1986 to January 1990 with 653 random trammel-net sets, each enclosing 3,721 m2. Samples from no-fishing areas had significantly (P < 0.05) greater abundance and larger fishes than fished areas. Relative abundance (standardized catch per unit effort, CPUE) in protected areas (6.4 fish/set) was 2.6 times greater than in the fished areas...
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An important issue surrounding biomonitoring in large rivers is the minimum sampling effort required to collect an adequate number of fish for accurate and precise determinations of biotic condition. During the summer of 2002, we sampled 15 randomly selected large-river sites in southern Idaho to evaluate the effects of sampling effort on an index of biotic integrity (IBI). Boat electrofishing was used to collect sample populations of fish in river reaches representing 40 and 100 times the mean channel width (MCW; wetted channel) at base flow. Minimum sampling effort was assessed by comparing the relation between reach length sampled and change in IBI score. Thirty-two species of fish in the families Catostomidae,...
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Current methods for estimation of age- and year-specific instantaneous mortality rates based on multiyear, multiple-age tagging studies assume that it is feasible to tag fish in a wide range of ages. For some species, however, only the youngest one or two age-classes are readily available for tagging. Given the practical advantages of tagging young fish only, an important question is whether such studies would provide the information needed for estimation of age-dependent mortality rates. We investigated three designs: tagging only the youngest available age-class, tagging the two youngest age-classes, and tagging the first five age-classes. We carried out simulation studies to assess estimator performance under...
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Three alternative gears—an AC electrofishing raft, bankpoles, and a 15-hoop-net set—were used in a standardized manner to sample channel catfish Ictalurus punctatus in three prairie streams of varying size in three seasons. We compared these gears as to time required per sample, size selectivity, mean catch per unit effort (CPUE) among months, mean CPUE within months, effect of fluctuating stream stage, and sensitivity to population size. According to these comparisons, the 15-hoop-net set used during stable water levels in October had the most desirable characteristics. Using our catch data, we estimated the precision of CPUE and size structure by varying sample sizes for the 15-hoop-net set. We recommend that...
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Numerous studies have examined the age and growth of shovelnose sturgeon Scaphirhynchus platorynchus, but only one study attempted to validate age estimation techniques. Therefore, our objective was to use marginal increment analysis to validate annulus formation in pectoral fin rays of shovelnose sturgeon collected from the Missouri River. We also compared the precision of age estimates between two different readers. Marginal increment distance indicated that for most of the populations an opaque band was laid down in pectoral fin rays during the summer. However, opaque bands were formed throughout the year in some individuals, which could be problematic when using fin rays for age estimation. The agreement of...
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Habitat use and movements of 25 adult cutthroat trout Oncorhynchus clarkii and 25 adult brook trout Salvelinus fontinalis from fall through winter 2002-2003 were assessed by means of radiotelemetry in a 7-km reach of a Rocky Mountains foothills stream. Temporal dynamics of winter habitat conditions were evaluated by regularly measuring the features of 30 pools and 5 beaver Castor canadensis ponds in the study reach. Groundwater inputs at three locations raised mean daily water temperatures in the stream channel during winter to 0.2-0.6??C and kept at least 250 m of the downstream channel free of ice, but the lack of surface ice further downstream led to the occurrence of frazil ice and anchor ice in pools and unstable...
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We double-marked largemouth bass Micropterus salmoides with Floy FD-68B anchor tags and visible implant elastomer (VIE) marks before stocking to compare retention of the two marks for age-0 (178 mm total length [TL]) and age-1 (273 mm TL) largemouth bass. In a short-term (31-d) evaluation, retention rate of anchor tags was over 94% for each age-class and retention of VIE marks was 98% in both age-classes. In a longer-term comparison of fish stocked into the Ohio River, retention was substantially higher for VIE marks (92.9%) than for anchor tags (42.9%) after 403 d (ages combined). Although anchor tags had high retention in two sizes of largemouth bass during the short-term experiment, they should not be used in...
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Fisheries studies often employ multiple gears that result in large percentages of zero values. We considered a zero-inflated Poisson (ZIP) model with random effects to address these excessive zeros. By employing a Bayesian ZIP model that simultaneously incorporates data from multiple gears to analyze data from the Missouri River, we were able to compare gears and make more year, segment, and macrohabitat comparisons than did the original data analysis. For channel catfish Ictalurus punctatus, our results rank (highest to lowest) the mean catch per unit area (CPUA) for gears (beach seine, benthic trawl, electrofishing, and drifting trammel net); years (1998 and 1997); macrohabitats (tributary mouth, connected secondary...