SEARCH · Geology Reports

Results for “Fisheries”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,099 records · Page 61Linked to original sources

USGS2013

Using diets to reveal overlap and egg predation among benthivorous fishes in Lake Michigan

Ecological stability in the Laurentian Great Lakes has been altered by nonindigenous species, such as the Round Goby Neogobius melanostomus and dreissenid mussels, and by declines in native amphipods Diporeia spp. We evaluated whether these changes could influence diet overlap between three benthivorous fishes (Slimy Sculpin Cottus cognatus, Deepwater Sculpin Myoxocephalus thompsonii, and Round Goby) and whether predation on eggs of native species was occurring. We examined diets of fish collected at depths of 69–128 m in Lake Michigan offshore of Frankfort and Muskegon, Michigan, and Two Rivers and Sturgeon Bay, Wisconsin, during January–May 2009 and 2010. Important prey (by dry weight proportion and by percent frequency of occurrence) for Slimy Sculpin were Mysis (0.34; 45%), Diporeia (0.16; 34%), and Limnocalanus macrurus (0.22; 68%); important prey for Deepwater Sculpin were Mysis (0.74; 92%) and Diporeia (0.16; 54%). Round Goby consumed mainly bivalves (i.e., dreissenids: 0.68; 95%) and Mysis (0.15; 37%). The two sculpin species consumed the eggs of Bloaters Coregonus hoyi (Slimy Sculpin: 0.04, 11%; Deepwater Sculpin: 0.02, 7%) and the eggs of Deepwater Sculpin (Slimy Sculpin: 0.03, 13%; Deepwater Sculpin: 0.05, 16%) during February–May at all sites. Round Goby also consumed eggs of these species but at lower levels (≤0.01; <1%). Diet overlap was identified between sculpin species at Frankfort and Sturgeon Bay, suggesting possible interspecific competition, but their diets did not overlap at Two Rivers; diet overlap was never observed between Round Goby and either sculpin species. Given that (1) diet overlap varied by site and (2) diet proportions varied spatially more than temporally, benthivores appear to be exhibiting localized responses to recent ecological changes. Overall, these results reveal that egg predation and interspecific competition could be important interactions to consider in future examinations of the population dynamics of these species or in ecosystem models that forecast how fisheries will respond to possible perturbations or management scenarios.

Michigan↗

USGS2014

Growth and survival of sea lampreys from metamorphosis to spawning in Lake Huron

Larval Sea Lampreys Petromyzon marinus live burrowed in stream bottoms and then metamorphose into their parasitic stage. Among larvae that metamorphose in a given year (i.e., parasitic cohort), autumn out-migrants (October–December) to the Laurentian Great Lakes can feed on fish for up to 6 months longer than spring outmigrants (March–May), which overwinter in streams without feeding. We evaluated whether the season of outmigration affected growth or survival of newlymetamorphosed Sea Lampreys in LakeHuron. Newlymetamorphosed individuals (n=2,718) from three parasitic cohorts were netted during their out-migration from BlackMallard Creek, Michigan, to LakeHuron during autumn 1997 through spring 2000; each out-migrant was injected with a sequentially numbered coded wire tag and was released back into the creek. After up to 18 months of feeding in the Great Lakes, 224 (8.2%) Sea Lampreys were recaptured (in 1999–2001) as upstream-migrating adults in tributaries to Lakes Huron and Michigan. Recovery rates of autumn and spring out-migrants as adults were 9.4% and 7.8%, respectively, and these rates did not significantly differ. Overwinter feeding (i.e., as parasites) by autumn out-migrants did not produce adult mean sizes greater than those of spring out-migrants. Because we detected no growth or survival differences between autumn and spring out-migrants, the capture of newly metamorphosed Sea Lampreys at any point during their out-migration should provide equal reductions in damage to Great Lakes fisheries. The absence of a difference in growth or survival between autumn and spring out-migrants is an aspect of Sea Lamprey life history that yields resiliency to this invasive parasite and complicates efforts for its control in the Great Lakes.

Lake Huron↗

USGS2014

Relationships among walleye population characteristics and genetic diversity in northern Wisconsin Lakes

The maintenance of genetic integrity is an important goal of fisheries management, yet little is known regarding the effects of management actions (e.g., stocking, harvest regulations) on the genetic diversity of many important fish species. Furthermore, relationships between population characteristics and genetic diversity remain poorly understood. We examined relationships among population demographics (abundance, recruitment, sex ratio, and mean age of the breeding population), stocking intensity, and genetic characteristics (heterozygosity, effective number of alleles, allelic richness, Wright's inbreeding coefficient, effective population size [ N e ], mean d 2 [a measure of inbreeding], mean relatedness, and pairwise population Φ ST estimates) for 15 populations of Walleye Sander vitreus in northern Wisconsin. We also tested for potential demographic and genetic influences on Walleye body condition and early growth. Combinations of demographic variables explained 47.1–79.8% of the variation in genetic diversity. Skewed sex ratios contributed to a reduction in N e and subsequent increases in genetic drift and relatedness among individuals within populations; these factors were correlated to reductions in allelic richness and early growth rate. Levels of inbreeding were negatively related to both age-0 abundance and mean age, suggesting N e was influenced by recruitment and generational overlap. A negative relationship between the effective number of alleles and body condition suggests stocking affected underlying genetic diversity of recipient populations and the overall productivity of the population. These relationships may result from poor performance of stocked fish, outbreeding depression, or density-dependent factors. An isolation-by-distance pattern of genetic diversity was apparent in nonstocked populations, but was disrupted in stocked populations, suggesting that stocking affected genetic structure. Overall, demographic factors were related to genetic diversity and stocking appeared to alter allelic frequencies and the genetic structure of Walleye populations in Wisconsin, possibly resulting in disruption of local adaptation.

Wisconsin↗

USGS2017

Spatial and temporal consumption dynamics of trout in catch-and-release areas in Arkansas tailwaters

Restrictive angling regulations in tailwater trout fisheries may be unsuccessful if food availability limits energy for fish to grow. We examined spatial and temporal variation in energy intake and growth in populations of Brown Trout Salmo trutta and Rainbow Trout Oncorhynchus mykiss within three catch-and-release (C-R) areas in Arkansas tailwaters to evaluate food availability compared with consumption. Based on bioenergetic simulations, Rainbow Trout fed at submaintenance levels in both size-classes (≤400 mm TL, >400 mm TL) throughout most seasons. A particular bottleneck in food availability occurred in the winter for Rainbow Trout when the daily ration was substantially below the minimum required for maintenance, despite reduced metabolic costs associated with lower water temperatures. Rainbow Trout growth rates followed a similar pattern to consumption with negative growth rates during the winter periods. All three size-classes (<250 mm TL, 250–400 mm TL, >400 mm TL) of Brown Trout experienced high growth rates and limited temporal bottlenecks in food availability. We observed higher mean densities for Rainbow Trout (47–342 fish/ha) than for Brown Trout (3–84 fish/ha) in all C-R areas. Lower densities of Brown Trout coupled with an ontogenetic shift towards piscivory may have allowed for higher growth rates and sufficient consumption rates to meet energetic demands. Brown Trout at current densities were more effective in maintaining adequate growth rates and larger sizes in C-R areas than were Rainbow Trout. Bioenergetic simulations suggest that reducing stocking levels of Rainbow Trout in the tailwaters may be necessary in order to achieve increased catch rates of larger trout in the C-R areas.

Arkansas↗

USGS2011

Developing user-friendly habitat suitability tools from regional stream fish survey data

We developed user-friendly fish habitat suitability tools (plots) for fishery managers in Michigan; these tools are based on driving habitat variables and fish population estimates for several hundred stream sites throughout the state. We generated contour plots to show patterns in fish biomass for over 60 common species (and for 120 species grouped at the family level) in relation to axes of catchment area and low-flow yield (90% exceedance flow divided by catchment area) and also in relation to axes of mean and weekly range of July temperatures. The plots showed distinct patterns in fish habitat suitability at each level of biological organization studied and were useful for quantitatively comparing river sites. We demonstrate how these plots can be used to support stream management, and we provide examples pertaining to resource assessment, trout stocking, angling regulations, chemical reclamation of marginal trout streams, indicator species, instream flow protection, and habitat restoration. These straightforward and effective tools are electronically available so that managers can easily access and incorporate them into decision protocols and presentations.

North American Journal of Fisheries Management↗

USGS2011

Recovery of coded wire tags at a caspian tern colony in San Francisco Bay: A technique to evaluate impacts of avian predation on juvenile salmonids

We recovered coded wire tags (CWTs) from a colony of Caspian terns Hydroprogne caspia on Brooks Island in San Francisco Bay, California, to evaluate predation on juvenile salmonids originating from the Sacramento and San Joaquin rivers. Subsamples of colony substrate representing 11.7% of the nesting habitat used by the terns yielded 2,079 salmonid CWTs from fish released and subsequently consumed by terns in 2008. The estimated number of CWTs deposited on the entire tern colony was 40,143 (ranging from 26,763 to 80,288), once adjustments were made to account for tag loss and the total amount of nesting habitat used by terns. Tags ingested by terns and then egested on the colony were undamaged, and the tags' complete numeric codes were still identifiable. The CWTs found on the tern colony indicated that hatchery Chinook salmon Oncorhynchus tshawytscha trucked to and released in San Pablo Bay were significantly more likely to be consumed by Caspian terns than Chinook salmon that migrated in-river to the bay; 99.7% of all tags recovered were from bay-released Chinook salmon. Of the CWTs recovered on the tern colony, 98.0% were from fall-run Chinook salmon, indicating a higher susceptibility to tern predation than for the spring run type. None of the approximately 518,000 wild Chinook salmon that were coded-wire-tagged and released in the basin were recovered on the tern colony, suggesting that the impacts on wild, U.S. Endangered Species Act-listed Chinook salmon populations were minimal in 2008. Overall, we estimate that 0.3% of the approximately 12.3 million coded-wire-tagged Chinook salmon released in the basin in 2008 were subsequently consumed by Caspian terns from the Brooks Island colony. These results indicate that CWTs implanted in juvenile salmon can be recovered from a piscivorous waterbird colony and used to evaluate smolt losses for runs that are tagged. Abstract We recovered coded wire tags (CWTs) from a colony of Caspian terns Hydroprogne caspia on Brooks Island in San Francisco Bay, California, to evaluate predation on juvenile salmonids originating from the Sacramento and San Joaquin rivers. Subsamples of colony substrate representing 11.7% of the nesting habitat used by the terns yielded 2,079 salmonid CWTs from fish released and subsequently consumed by terns in 2008. The estimated number of CWTs deposited on the entire tern colony was 40,143 (ranging from 26,763 to 80,288), once adjustments were made to account for tag loss and the total amount of nesting habitat used by terns. Tags ingested by terns and then egested on the colony were undamaged, and the tags' complete numeric codes were still identifiable. The CWTs found on the tern colony indicated that hatchery Chinook salmon Oncorhynchus tshawytscha trucked to and released in San Pablo Bay were significantly more likely to be consumed by Caspian terns than Chinook salmon that migrated in-river to the bay; 99.7% of all tags recovered were from bay-released Chinook salmon. Of the CWTs recovered on the tern colony, 98.0% were from fall-run Chinook salmon, indicating a higher susceptibility to tern predation than for the spring run type. None of the approximately 518,000 wild Chinook salmon that were coded-wire-tagged and released in the basin were recovered on the tern colony, suggesting that the impacts on wild, U.S. Endangered Species Act-listed Chinook salmon populations were minimal in 2008. Overall, we estimate that 0.3% of the approximately 12.3 million coded-wire-tagged Chinook salmon released in the basin in 2008 were subsequently consumed by Caspian terns from the Brooks Island colony. These results indicate that CWTs implanted in juvenile salmon can be recovered from a piscivorous waterbird colony and used to evaluate smolt losses for runs that are tagged ?? American Fisheries Society 2011.

North American Journal of Fisheries Management↗

USGS2011

Spatiotemporal distribution and population characteristicsof a nonnative lake trout population, with implications for suppression

We evaluated the distribution and population characteristics of nonnative lake trout Salvelinus namaycush in Lake McDonald,Glacier National Park,Montana, to provide biological data in support of a potential suppression program. Using ultrasonic telemetry, we identified spatial and temporal distribution patterns by tracking 36 adult lake trout (1,137 relocations). Lake trout rarely occupied depths greater than 30 m and were commonly located in the upper hypolimnion directly below the metalimnion during thermal stratification. After breakdown of themetalimnion in the fall, lake trout primarily aggregated at two spawning sites. Lake trout population characteristics were similar to those of populations within the species' native range. However, lake trout in Lake McDonald exhibited lower total annual mortality (13.2%), latermaturity (age 12 formales, age 15 for females), lower body condition, and slower growth than are typically observed in the southern extent of their range. These results will be useful in determining where to target suppression activities (e.g., gillnetting, trap-netting, or electrofishing) and in evaluating responses to suppression efforts. Similar evaluations of lake trout distribution patterns and population characteristics are recommended to increase the likelihood that suppression programs will succeed. ?? American Fisheries Society 2011.

North American Journal of Fisheries Management↗

USGS2011

Movement and survival of brown trout and rainbow trout in an ozark tailwater river

We evaluated the movement of adult brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss in relation to a catch-andrelease area in the White River downstream from Beaver Dam, Arkansas. Nine fish of each species were implanted with radio transmitters and monitored from July 1996 to July 1997. The 1.5- km river length of a catch-and-release area (closed to angler harvest) was greater than the total linear range of 72% of the trout (13 of 18 fish), but it did not include two brown trout spawning riffles, suggesting that it effectively protects resident fish within the catch-and-release area except during spawning. The total detected linear range of movement varied from 172 to 3,559 m for brown trout and from 205 to 3,023mfor rainbow trout. The movements of both species appeared to be generally similar to that in unregulated river systems. The annual apparent survival of both trout species was less than 0.40, and exploitation was 44%.Management to protect fish on spawning riffles may be considered if management for wild brown trout becomes a priority. ?? American Fisheries Society 2011.

North American Journal of Fisheries Management↗

USGS2011

Selectivity evaluation for two experimental gill-net configurations used to sample Lake Erie walleyes

We used length frequencies of captured walleyes Sander vitreus to indirectly estimate and compare selectivity between two experimental gill-net configurations used to sample fish in Lake Erie: (1) a multifilament configuration currently used by the Ohio Department of Natural Resources (ODNR) with stretched-measure mesh sizes ranging from 51 to 127 mm and a constant filament diameter (0.37 mm); and (2) a monofilament configuration with mesh sizes ranging from 38 to 178 mm and varying filament diameter (range = 0.20–0.33 mm). Paired sampling with the two configurations revealed that the catch of walleyes smaller than 250 mm and larger than 600 mm was greater in the monofilament configuration than in the multifilament configuration, but the catch of 250–600-mm fish was greater in the multifilament configuration. Binormal selectivity functions yielded the best fit to observed walleye catches for both gill-net configurations based on model deviances. Incorporation of deviation terms in the binormal selectivity functions (i.e., to relax the assumption of geometric similarity) further improved the fit to observed catches. The final fitted selectivity functions produced results similar to those from the length-based catch comparisons: the monofilament configuration had greater selectivity for small and large walleyes and the multifilament configuration had greater selectivity for mid-sized walleyes. Computer simulations that incorporated the fitted binormal selectivity functions indicated that both nets were likely to result in some bias in age composition estimates and that the degree of bias would ultimately be determined by the underlying condition, mortality rate, and growth rate of the Lake Erie walleye population. Before the ODNR switches its survey gear, additional comparisons of the different gill-net configurations, such as fishing the net pairs across a greater range of depths and at more locations in the lake, should be conducted to maintain congruence in the fishery-independent survey time series.

North American Journal of Fisheries Management↗

USGS2011

Population dynamics of Lake Ontario lake trout during 1985-2007

Lake trout Salvelinus namaycush were extirpated from Lake Ontario circa 1950 owing to commercial and recreational fishing, predation by sea lampreys Petromyzon marinus , and habitat degradation. Since the 1970s, substantial efforts have been devoted to reestablishing a self-sustaining population through stocking, sea lamprey control, and harvest reduction. Although a stocking-supported population has been established, only limited natural reproduction has been detected. Since the 1990s, surveys have indicated a continuing decline in overall abundance despite fairly static stocking levels. We constructed a statistical catch-at-age model to describe the dynamics of Lake Ontario lake trout from 1985 to 2007 and explore what factor(s) could be causing the declines in abundance. Model estimates indicated that abundance had declined by approximately 76% since 1985. The factor that appeared most responsible for this was an increase in age-1 natural mortality rates from approximately 0.9 to 2.5 between 1985 and 2002. The largest source of mortality for age-2 and older fish was sea lamprey predation, followed by natural and recreational fishing mortality. Exploitation was low, harvest levels being uncertain and categorized by length rather than age. Accurate predictions of fishery harvest and survey catch per unit effort were obtained despite low harvest levels by using atypical data (e.g., numbers stocked as an absolute measure of recruitment) and a flexible modeling approach. Flexible approaches such as this might allow similar assessments for a wide range of lightly exploited stocks. The mechanisms responsible for declining age-1 lake trout survival are unknown, but the declines were coincident with an increase in the proportion of stocked fish that were of the Seneca strain and a decrease in the overall stocking rate. It is possible that earlier studies suggesting that Seneca strain lake trout would be successful in Lake Ontario are no longer applicable given the large ecosystem changes that have occurred subsequent to invasion by dreissenid mussels.

North American Journal of Fisheries Management↗

USGS2012

Site choice among Minnesota walleye anglers: The influence of resource conditions, regulations and catch orientation on Lake Preference

Understanding angler site choice preferences is important in the management of recreational fisheries to forecast angling demand and effort. This study investigated lake choice by recreational anglers fishing for walleye Sander vitreus in Minnesota and examined how choices were influenced by lake characteristics, angler demographics, and angler catch orientation. We collected data through a stated choice preference experiment using a survey administered to a sample of Minnesota resident ( n =1096) and nonresident ( n =535) anglers. Multinomial probit choice models were used to estimate preferences in lake choice. Lake characteristics included walleye abundance, walleye size, bag limit, slot limit, and distance from primary residence. Models included (1) lake characteristics only, (2) lake characteristics and angler demographics, and (3) lake characteristics with angler demographics and catch orientation factors. The coefficients of lake attributes had expected signs with greater preference for higher walleye abundance, larger walleye, bigger bag limits, absence of slot limits, and less driving time from home ( P <0.001 for all lake characteristics in the first model). Lake choice was influenced by the interaction of lake characteristics with age (negative with abundance of fish, P <0.100; positive with distance from home, P <0.001), metropolitan and out-of-state residency (positive with distance from home, P <0.001), and strength of preference for walleye (positive with distance, P <0.01). A stronger orientation to keep walleye was positively related to increased bag limits ( P <0.001) and negatively related to slot limits ( P <0.01). Study results have clear implications for managers—bag limits, relative to other lake characteristics, had a large influence on anglers’ lake choice for walleye fishing. Because of a stronger catch orientation among walleye anglers, low bag limits reduce lake preference. The results clarify the trade-offs that anglers make when selecting a place to fish for walleye and demonstrate how different management scenarios might influence angler participation.

Minnesota↗

USGS2012

The spatial scale for cisco recruitment dynamics in Lake Superior during 1978-2007

The cisco Coregonus artedi was once the most abundant fish species in the Great Lakes, but currently cisco populations are greatly reduced and management agencies are attempting to restore the species throughout the basin. To increase understanding of the spatial scale at which density‐independent and density‐dependent factors influence cisco recruitment dynamics in the Great Lakes, we used a Ricker stock–recruitment model to identify and quantify the appropriate spatial scale for modeling age‐1 cisco recruitment dynamics in Lake Superior. We found that the recruitment variation of ciscoes in Lake Superior was best described by a five‐parameter regional model with separate stock–recruitment relationships for the western, southern, eastern, and northern regions. The spatial scale for modeling was about 260 km (range = 230–290 km). We also found that the density‐independent recruitment rate and the rate of compensatory density dependence varied among regions at different rates. The density‐independent recruitment rate was constant among regions (3.6 age‐1 recruits/spawner), whereas the rate of compensatory density dependence varied 16‐fold among regions (range = −0.2 to −2.9/spawner). Finally, we found that peak recruitment and the spawning stock size that produced peak recruitment varied among regions. Both peak recruitment (0.5–7.1 age‐1 recruits/ha) and the spawning stock size that produced peak recruitment (0.3–5.3 spawners/ha) varied 16‐fold among regions. Our findings support the hypothesis that the factors driving cisco recruitment operate within four different regions of Lake Superior, suggest that large‐scale abiotic factors are more important than small‐scale biotic factors in influencing cisco recruitment, and suggest that fishery managers throughout Lake Superior and the entire Great Lakes basin should address cisco restoration and management efforts on a regional scale in each lake.

Lake Superior↗

USGS2012

Relying on fin erosion to identify hatchery-reared brown trout in a Tennessee river

Hatchery-induced fin erosion can be used to identify recently stocked catchable-size brown trout Salmo trutta during annual surveys to qualitatively estimate contributions to a fishery. However, little is known about the longevity of this mark and its effectiveness as a short-term (≤ 1 year) mass-marking technique. We evaluated hatchery-induced pectoral fin erosion as a mass-marking technique for short-term stocking evaluations by stocking microtagged brown trout in a tailwater and repeatedly sampling those fish to observe and measure their pectoral fins. At Dale Hollow National Fish Hatchery, 99.1% (228 of 230) of microtagged brown trout in outdoor concrete raceways had eroded pectoral fins 1 d prior to stocking. Between 34 and 68 microtagged and 26-35 wild brown trout were collected during eight subsequent electrofishing samples. In a blind test based on visual examination of pectoral fins at up to 322 d poststocking, one observer correctly identified 91.7% to 100.0% (mean of 96.9%) of microtagged brown trout prior to checking for microtags. In the laboratory, pectoral fin length and width measurements were recorded to statistically compare the fin measurements of wild and microtagged hatchery brown trout. With only one exception, all pectoral fin measurements on each date averaged significantly larger for wild trout than for microtagged brown trout. Based on the number of pectoral fin measurements falling below 95% prediction intervals, 93.7% (148 of 158) of microtagged trout were correctly identified as hatchery fish based on regression models up to 160 d poststocking. Only 72.2% (70 of 97) of microtagged trout were identified correctly after 160 d based on pectoral fin measurements and the regression models. We concluded that visual examination of pectoral fin erosion was a very effective way to identify stocked brown trout for up to 322 d poststocking.

North American Journal of Fisheries Management↗

USGS2012

A prototype splitter apparatus for dividing large catches of small fish

Due to financial and time constraints, it is often necessary in fisheries studies to divide large samples of fish and estimate total catch from the subsample. The subsampling procedure may involve potential human biases or may be difficult to perform in rough conditions. We present a prototype gravity-fed splitter apparatus for dividing large samples of small fish (30–100 mm TL). The apparatus features a tapered hopper with a sliding and removable shutter. The apparatus provides a comparatively stable platform for objectively obtaining subsamples, and it can be modified to accommodate different sizes of fish and different sample volumes. The apparatus is easy to build, inexpensive, and convenient to use in the field. To illustrate the performance of the apparatus, we divided three samples (total N = 2,000 fish) composed of four fish species. Our results indicated no significant bias in estimating either the number or proportion of each species from the subsample. Use of this apparatus or a similar apparatus can help to standardize subsampling procedures in large surveys of fish. The apparatus could be used for other applications that require dividing a large amount of material into one or more smaller subsamples.

North American Journal of Fisheries Management↗

USGS2012

Strategies to control a common carp population by pulsed commercial harvest

Commercial fisheries are commonly used to manage nuisance fishes in freshwater systems, but such efforts are often unsuccessful. Strategies for successfully controlling a nuisance population of common carp Cyprinus carpio by pulsed commercial harvest were evaluated with a combination of (1) field sampling, (2) population estimation and CPUE indexing, and (3) simulation using an exponential semidiscrete biomass dynamics model (SDBDM). The range of annual fishing mortalities ( F ) that resulted in successful control ( F = 0.244–0.265) was narrow. Common carp biomass dynamics were sensitive to unintentional underharvest due to high rates of surplus production and a biomass doubling time of 2.7 years. Simulations indicated that biomanipulation never achieved successful control unless supplemental fishing mortality was imposed. Harvest of a majority of annual production was required to achieve successful control, as indicated by the ecotrophic coefficient (EC). Readily available biomass data and tools such as SDBDMs and ECs can be used in an adaptive management framework to successfully control common carp and other nuisance fishes by pulsed commercial fishing.

North American Journal of Fisheries Management↗

USGS2013

An evaluation of liquid ammonia (ammonium hydroxide) as a candidate piscicide

Eradication of populations of nonnative aquatic species for the purpose of reintroducing native fish is often difficult because very few effective tools are available for removing aquatic organisms. This creates the need to evaluate new chemicals that could be used as management tools for native fish conservation. Ammonia is a natural product of fish metabolism and is naturally present in the environment at low levels, yet is known to be toxic to most aquatic species. Our objective was to determine the feasibility of using liquid ammonia as a fisheries management tool by evaluating its effectiveness at killing undesirable aquatic species and its persistence in a pond environment. A suite of invasive aquatic species commonly found in the southwestern USA were introduced into two experimental outdoor ponds located at the Rocky Mountain Research Station in Flagstaff, Arizona. Each pond was treated with ammonium hydroxide (29%) at 38 ppm. This target concentration was chosen because previous studies using anhydrous ammonia reported incomplete fish kills in ponds at concentrations less than 30 ppm. Water quality was monitored for 49 d to determine how quickly the natural bacteria in the environment converted the ammonia to nitrate. Ammonia levels remained above 8 ppm for 24 and 18 d, respectively, in ponds 1 and 2. Nitrite levels in each pond began to rise approximately 14 d after dosing with ammonia and stayed above 5 ppm for an additional 21 d in pond 1 and 18 d in pond 2. After 49 d all water in both ponds was drained and no fish, crayfish, or tadpoles were found to have survived the treatment, but aquatic turtles remained alive and appeared unaffected. Liquid ammonia appears to be an effective tool for removing many problematic invasive aquatic species and may warrant further investigation as a piscicide.

North American Journal of Fisheries Management↗

USGS2013

Mortality of Palmetto bass following catch-and-release angling

Palmetto bass (Striped Bass Morone saxatilis x White Bass M. chrysops ) have been stocked into reservoirs in the southeastern USA since the late 1960s and have gained widespread acceptance as a sport fish. These fisheries are growing in popularity and catch-and-release (CR) fishing is commonplace; however, there is a dearth of information on CR mortality of palmetto bass. We experimentally angled palmetto bass ( n = 56; >373-mm TL) in a Tennessee reservoir using traditional angling gear in water temperatures ranging from 13 °C to 32 °C. Ultrasonic transmitters equipped with floats were externally attached to fish, which were released immediately and tracked multiple times within 10 d of release. Mortality was negligible (3.6%) in fall and spring at cool water temperatures but was high (39.3%) in summer when water temperatures exceeded 26 °C. The best logistic regression model based on Akaike's information criterion for small sample sizes scores relied on water temperature alone to predict CR mortality of palmetto bass; there was little support for other models that included all possible combinations of the six other predictor variables we tested. Palmetto bass in our study experienced lower CR mortality than Striped Bass in other systems, but CR mortality rates for palmetto bass that approach or exceed 40% during summer are still problematic if the goal is to maintain fishing quality.

North American Journal of Fisheries Management↗

USGS2013

Predicting paddlefish roe yields using an extension of the Beverton–Holt equilibrium yield-per-recruit model

Equilibrium yield models predict the total biomass removed from an exploited stock; however, traditional yield models must be modified to simulate roe yields because a linear relationship between age (or length) and mature ovary weight does not typically exist. We extended the traditional Beverton-Holt equilibrium yield model to predict roe yields of Paddlefish Polyodon spathula in Kentucky Lake, Tennessee-Kentucky, as a function of varying conditional fishing mortality rates (10-70%), conditional natural mortality rates (cm; 9% and 18%), and four minimum size limits ranging from 864 to 1,016mm eye-to-fork length. These results were then compared to a biomass-based yield assessment. Analysis of roe yields indicated the potential for growth overfishing at lower exploitation rates and smaller minimum length limits than were suggested by the biomass-based assessment. Patterns of biomass and roe yields in relation to exploitation rates were similar regardless of the simulated value of cm, thus indicating that the results were insensitive to changes in cm. Our results also suggested that higher minimum length limits would increase roe yield and reduce the potential for growth overfishing and recruitment overfishing at the simulated cm values. Biomass-based equilibrium yield assessments are commonly used to assess the effects of harvest on other caviar-based fisheries; however, our analysis demonstrates that such assessments likely underestimate the probability and severity of growth overfishing when roe is targeted. Therefore, equilibrium roe yield-per-recruit models should also be considered to guide the management process for caviar-producing fish species.

North American Journal of Fisheries Management↗