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North American Journal of Fisheries Management
American Fisheries Society
North American Journal of Fisheries Management

American Fisheries Society

0275-5947

North American Journal of Fisheries Management/Journal North American Journal of Fisheries ManagementSCIISTP
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    2页
      原文链接:
    • NSTL

    Maximum Economic Yield and Nonlinear Catchability

    Minling Pan
    17页
    查看更多>>摘要：Abstract Maximum economic yield (MEY) as derived from Schaefer’s (1957) bioeconomic model was potentially a major contribution to fishery management, but it has been hard to apply to fishery management in reality. Schaefer’s model with fixed catchability and associated linear CPUE does not match the variable nature of catchability resulting from technological progress and schooling behavior, leading to a biased estimation of MEY or economic optimal biomass (BMEY). This study improves on Schaefer’s model by incorporating nonlinear CPUE, where MEY depends on biomass relationships with catchability and with CPUE. When CPUE is constant, MEY is shown analytically to be the same as the biological optimal yield (maximum sustainable yield [MSY]) and the related optimal biomasses are equivalent (BMEY = BMSY). However, in cases of nonlinear CPUE, MEY might be closer to or further away from MSY. The less sensitive the CPUE is in response to changes in biomass, the closer the economic optimum BMEY is to the biological optimum BMSY. When CPUE is sensitive to changes in biomass, the benefit of leaving more fish in water (the stock effect) is more noticeable. Hence, this revised model can become an important component in matching fishery management goals to the realities of fisheries. Simulation analyses further illustrate that the traditional Schaefer economic optimum does not apply to all fisheries. This model provides the basis for fishery management to set a total catch limit (as a fishery management reference point) that could achieve MEY but also defines how MEY could be equal to, closer to, or further away from MSY based on characteristics of an individual fishery. For a fishery in overfished status, it helps fishery managers to decide a rebuilding target at BMSY or at a higher abundance than BMSY in order to achieve MEY and still meet biological reference points.
      原文链接:
    • NSTL
    • Wiley

    Age‐Structured Interactions among Reintroduced Sockeye Salmon, Resident Kokanee, Invasive Mysids, and their Zooplankton Prey in Skaha Lake, British Columbia

    Kim D. HyattDonald J. McQueenAthena D. OgdenRyan Benson...
    28页
    查看更多>>摘要：Abstract In 2004, after an 85+ year absence, Sockeye Salmon Oncorhynchus nerka were reintroduced into Skaha Lake, British Columbia. Prior to this, the lake’s planktivore community was dominated by kokanee (lacustrine Sockeye Salmon) and an invasive freshwater shrimp Mysis diluviana, and British Columbia fisheries managers were concerned that reintroduced Sockeye Salmon fry might reduce the abundance of zooplankton prey and negatively affect the abundance and size of kokanee available for the recreational fishery. We looked for possible adverse effects by introducing contrasting densities (0–2,309 fish/ha) of marked, hatchery‐origin Sockeye Salmon fry to Skaha Lake over 12?years (2005–2017). During each year, we monitored state change indicators of lake flushing, water temperature, nutrients, phytoplankton, microzooplankton, M. diluviana, kokanee, and Sockeye Salmon. Zooplankton consumption by Sockeye Salmon, kokanee, and M. diluviana was estimated via bioenergetics models. We found that (1) average densities of pelagic fish gradually increased above premanipulation densities and (2) survival (egg to winter) of kokanee fry was variable but positively associated with increased abundances of Sockeye Salmon fry. Average survival of age‐0 to age‐3+ kokanee in Skaha Lake exhibited no significant trends. We also found that (3) growth rates for age‐0 Sockeye Salmon fry and kokanee were stable during 2005–2013, despite moderate increases in fish abundance, but declined in 2017. This decline was associated with record‐high biomasses of kokanee and M. diluviana, record rates of zooplankton loss from predation and lake flushing, and reduced zooplankton production. We found that (4) bioenergetics data showed that, on average, 1.8% of annual zooplankton prey consumption was attributable to hatchery‐origin Sockeye Salmon fry, 2.8% to Lake Whitefish Coregonus clupeaformis, 13.9% to older kokanee, and 79.6% of the zooplankton was consumed by M. diluviana. We concluded that during 2005–2015 consumption by planktivores never exceeded production by zooplankton, but in 2017, when lake flushing rates were exceptionally high, consumption by planktivores exceeded lake‐carrying capacity for pelagic fish. Sockeye Salmon fry played virtually no part in these events.
      原文链接:
    • NSTL
    • Wiley

    Evaluating Target Levels of American White Pelican Abundance to Achieve Management Objectives for Adfluvial Yellowstone Cutthroat Trout

    Joshua L. McCormickArnold F. BrimmerCarson J. Watkins
    14页
    查看更多>>摘要：Abstract Recent declines in abundance of Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri in the upper Blackfoot River drainage in Idaho coincided with establishment of a nearby nesting colony and increased abundance of American white pelicans Pelecanus erythrorhynchos (hereafter, “pelicans”). Published pelican predation rates have been estimated to be as high as 70% on Yellowstone Cutthroat Trout in the Blackfoot River. Consequently, the Idaho Department of Fish and Game established management objectives for pelicans of less than 350 breeding pairs or 700 adults. However, a thorough assessment has not been conducted to evaluate if the pelican abundance objective would reduce predation to an extent that would allow Yellowstone Cutthroat Trout to recover to levels that meet minimum objectives for abundance. A Bayesian state‐space model that integrated survival and abundance data was used in this study to evaluate the effects of local pelican abundance on survival, abundance, and population growth rate of Yellowstone Cutthroat Trout. Survival of both juvenile and adfluvial adult Yellowstone Cutthroat Trout decreased as pelican abundance increased, and there was a positive relationship between survival of both life stages and population growth rate. If the current management objective for abundance of 700 breeding pelicans was met, the probability of meeting or exceeding the Yellowstone Cutthroat Trout objective was 0.44 and declined substantially as simulated pelican abundance increased beyond 700. Results of this study suggest that if pelican abundance can be maintained at or below the current management objective, there is a reasonable chance of meeting the management objective for Yellowstone Cutthroat Trout.
      原文链接:
    • NSTL
    • Wiley

    Natural Recruitment Potential of a Reintroduced Shovelnose Sturgeon Population in the Bighorn River, Wyoming

    Nicholas P. HogbergJoseph A. SkorupskiSamuel J. Hochhalter
    11页
    查看更多>>摘要：Abstract Shovelnose Sturgeon Scaphirhynchus platorynchus were extirpated from the Bighorn River, Wyoming during the 20th century after the construction of two main‐stem dams and the resulting modifications to fish passage and flow and thermal regimes. The species was reintroduced to the river between 1996 and 2020, but nothing was known about how these fish used the river and whether they could sustain themselves without consistent stocking. Radio telemetry during 2015–2018 identified at least two putative spawning locations 95.6 and 139.5 river kilometers upstream from a reservoir transition zone. Temperature and velocity data suggest that most of the drifting larvae will have insufficient fluvial habitat to complete their drift stage and are likely to enter the Bighorn Lake transition zone. Benthic dissolved oxygen concentrations in the reservoir transition zone were low enough to cause recruitment reduction or failure for drifting larvae that reach this habitat. Future monitoring will determine whether this population persists, but this study highlights the importance of understanding species life history and the causes of extirpations to better predict reintroduction success.
      原文链接:
    • NSTL
    • Wiley

    Proposed Standard Weight (Ws) Equation and Length Categories for Utah Chub

    Aaron R. BlackZachary S. BeardJon M. FlindersMichael C. Quist...
    10页
    查看更多>>摘要：Abstract Condition indices, such as relative weight (Wr), provide a simple method for comparing length–weight relationships among populations. However, no standard weight (Ws) equation?has been developed for Utah Chub Gila atraria, a species of important management focus in the Intermountain West. We obtained length–weight data for 30,541 Utah Chub from 24 populations in Idaho, Montana, Utah, and Wyoming. We used the regression line percentile (RLP), linear empirical percentile (EmP), and quadratic EmP methods to develop average (50th percentile) and above average (75th percentile) Ws equations. Additionally, Froese’s method was used to develop another Ws equation?for Utah Chub. Length‐related biases were detected in Ws equations developed using the RLP, 50th percentile quadratic EmP, and Froese methods. The linear EmP Ws equations did not exhibit length‐related biases for the 50th and 75th percentiles. We propose using the 75th percentile linear EmP Ws equation?for Utah Chub between 90 and 410?mm TL. The EmP 75th percentile equation?was log10(Ws)?=??4.938?+?3.031·log10(TL), where Ws is weight in grams and TL is in millimeters. The English equivalent of this equation?is log10(Ws)?=??3.335?+?3.031·log10(TL), where Ws is weight in pounds and TL is in inches for 4–16‐in Utah Chub. Additionally, we propose that minimum TLs of 100?mm (4 in; stock), 200?mm (8 in; quality), 250?mm (10 in; preferred), 300?mm (12 in; memorable), and 380?mm (15 in; trophy) be used to calculate proportional size distribution (PSD) indices. Better understanding Utah Chub populations using Wr and PSDs will aid managers in assessing management strategies (e.g., biological controls) focused on Utah Chub.
      原文链接:
    • NSTL
    • Wiley

    Modeling Distribution of Endemic Bartram’s Bass Micropterus?sp. cf.?coosae: Disturbance and Proximity to Invasion Source Increase Hybridization with Invasive Alabama Bass

    Brandon K. PeoplesEmily JudsonTanya L. DardenDaniel J. Farrae...
    13页
    查看更多>>摘要：Abstract “Bartram’s Bass” Micropterus?sp. cf.?coosae is endemic to the upper Savannah River basin of the southeastern United States and is threatened by hybridization with invasive Alabama Bass Micropterus henshalli. Bartram’s Bass have been functionally extirpated from reservoirs, and hybrid individuals have been detected in several tributaries. However, the extent of introgression in tributaries is currently unknown. Our objectives were to (1) assess the distribution of Bartram’s Bass, native Largemouth Bass M. salmoides, invasive Alabama Bass, and their hybrids in streams of the upper Savannah River basin and (2) quantify effects of abiotic variables on the distribution of each species. We sampled 154 locations in 2017 and 2018 and assigned genetic identity using hydrolysis probes and microsatellites. We?used conditional inference trees to quantify variables affecting the occurrence of each species and hybrids. We observed widespread hybridization across the basin. Pure Bartram’s Bass were collected at 27% (42) of sites, among which only 12 sites contained pure Bartram’s Bass and no other congeners. Thirty sites where pure Bartram’s Bass were collected contained hybrids. In the montane Blue Ridge ecoregion, occurrence of pure Bartram’s Bass was negatively affected by low levels of local‐scale developed land cover. In the lower‐relief Piedmont ecoregion, pure Bartram’s Bass were positively associated with watershed‐scale forest land cover and stream gradient. Distance from a reservoir was positively associated with occurrence of pure Bartram’s Bass in both ecoregions. Pure Bartram’s Bass are likely to occur with high probability in only 16% of nonimpounded stream segments; this represents a conservative estimate, and the true number is likely lower. However, future work accounting for incomplete detection of Bartram’s Bass will help to improve confidence in true extirpations. Conservation efforts may be more successful if implemented on stream segments farther from reservoirs or upstream of dispersal barriers preventing colonization of Alabama Bass.
      原文链接:
    • NSTL
    • Wiley

    Alternative Prey Reduces Largemouth Bass Predation Mortality on Newly Stocked Channel Catfish Fingerlings

    Cory BecherStephen M. TyszkoRichard D. ZweifelJoseph D. Conroy...
    12页
    查看更多>>摘要：Abstract Management agencies commonly stock Channel Catfish Ictalurus punctatus as advanced yearlings instead of fingerlings (age 0) to help reduce potential predation mortality despite uncertainty regarding the degree to which predation limits fingerling poststocking survival. To better understand whether fingerling survival during the first 7?d after stocking—when predation risk is likely greatest—could benefit from the presence of alternative prey fish, we conducted an experiment in 0.4‐ha ponds (N?=?18; 6 ponds/treatment) that measured fingerling (TL range?=?56–186?mm) survival in ponds with predators only (adult Largemouth Bass Micropterus salmoides; mean TL?=?327?mm; SE?=?21), with predators and alternative prey fishes (Bluegill Lepomis macrochirus and Goldfish Carassius auratus), or with neither (i.e., control ponds). Without alternative prey, fingerling Channel Catfish survival 1 week after stocking was significantly (P?<?0.01) lower (89%) than in the ponds with alternative prey (98%) or in the control treatment with no predators (97%). Our experiment also indicated the potential for alternative prey to promote fingerling survival by reducing water clarity, not just by serving as a buffer from predation. Further research, however, is needed to determine the degree to which our findings apply to larger ecosystems and to learn whether stocked fingerlings survive well enough after the initial stocking period to achieve desired management goals. Even so, our results suggest that alternative prey can reduce Largemouth Bass predation mortality on fingerlings immediately after stocking, which could influence Channel Catfish stocking approaches in some managed systems.
      原文链接:
    • NSTL
    • Wiley

    Relative Effectiveness of D‐Frame Dip Nets, Quatrefoil Light Traps, and Towed Ichthyoplankton Nets for Larval Muskellunge

    Jared E. KrebsEthan J. BrandtDaniel J. DembkowskiDaniel A. Isermann...
    7页
    查看更多>>摘要：Abstract Muskellunge Esox masquinongy are large, predatory game fish whose association with shallow, complex habitats is well documented, particularly during early life stages. Despite this association, relatively little guidance exists regarding effective sampling of Muskellunge larvae and previous efforts to sample larval Muskellunge have been met with limited success. Therefore, our objective was to determine the relative effectiveness of three sampling gears for capturing naturally produced Muskellunge larvae. Larvae were sampled during 2019 and 2020 at known Muskellunge spawning locations in Snipe Lake, Wisconsin, with D‐frame dip nets (1,000‐μm mesh), quatrefoil light traps, and towed ichthyoplankton nets (1,000‐μm mesh). Sixty larval Muskellunge were captured across all gears, and catches in D‐frame dip nets comprised nearly 87% (52 of 60) of the total catch. Furthermore, D‐frame dip nets captured the broadest size range of larval Muskellunge (TL range?=?14–33?mm). Greater effectiveness of D‐frame dip nets in comparison with other gears is likely related to their ability to be used in and around structurally complex habitats without fouling or clogging. Our results suggest that D‐frame dip nets should be considered as a cost‐ and time‐effective tool for targeting larval Muskellunge in complex habitats.
      原文链接:
    • NSTL
    • Wiley

    Chasing Northern Pike under Ice: Long‐Distance Movements Following Catch‐and‐Release Ice Angling

    Christopher M. SomersUna GoncinShayna HamiltonMichelle Chupik...
    10页
    查看更多>>摘要：Abstract Catch‐and‐release ice angling is a popular recreational activity, but little is known about the postrelease behavior of fish in the winter. Cold water temperatures and an ambush hunting strategy may constrain Northern Pike Esox lucius, limiting their postrelease movements to a small area near the capture location. We used manual acoustic telemetry to track 15 Northern Pike ranging from 56 to 98.5?cm total length for up to 7?d after catch‐and‐release ice angling in Buffalo Pound Lake, Saskatchewan, Canada. All of the fish but one moved unexpectedly long distances of several km over the tracking period. For the fish that were tracked over all 7?d, path lengths traveled ranged from 1.4 to 18.4?km. The minimum daily distance traveled ranged from 0 to 4.6?km and varied significantly by tracking day; the fish moved shorter distances on day 4 postrelease. There was a significant interaction between fish size and day postrelease; larger fish moved shorter minimum daily distances and dispersed shorter distances from the release site over the first 2?d of tracking. In contrast, by 5?d after release, both the largest and smallest fish had dispersed the longest distances from the release site and intermediate‐sized fish dispersed the least. The cumulative path length traveled by day 5 of tracking did not reveal any significant size‐based patterns. Our study raises the possibility that relatively large movements may be common for Northern Pike in the winter despite cold water temperatures and their expected foraging behavior. In addition, postrelease behavior varies with fish size. Habitat and space requirements for Northern Pike in the winter can encompass much larger areas and more habitat features than has been previously envisioned.
      原文链接:
    • NSTL
    • Wiley