Hoop Nets Research Articles

An updated survey of freshwater fishes within Letchworth State Park and surrounding area's of the Genesee River.

The goal of this study was to gather information about freshwater fishes in Letchworth State Park (42.615275° N, -77.992825° W), a portion of New York State-owned land located in the Genesee River Watershed that lacks known data about its fish diversity. Fish collection took place between 2017 and 2019 in the Genesse River upstream and downstream of the falls using electrofishing, gill, hoop, and seine netting. This was the first attempt at a comprehensive survey of this portion of the river, which allowed for a baseline to be established regarding fish biodiversity in the region. The updated total number of species found in this portion of the Genesee River was 25, 22 of which were newly identified downstream of the falls in Letchworth State Park. We encourage further collection and continuation of this survey with consistent sampling techniques to raise awareness about the importance of freshwater fish diversity in stream ecosystems across the globe.

Why new scientific information is important for native fish conservation: A case study from the humpback chub (Gila cypha) in the Grand Canyon, U.S.A.

Abstract Habitat descriptions found in critical habitat designations and recovery plans are important for protecting endangered species. However, in order to protect critical habitat, it is necessary to update descriptions of habitat use when range shifts occur or new studies change the understanding of habitat use. This study examined the habitat use of a threatened desert fish to determine whether current habitat use matched the descriptions in recovery documents. Recovery documents describe humpback chub (Gila cypha) as being dependent on rocky, canyon‐bound habitats during all life stages, but recent surveys found humpback chub in open, silt‐laden habitats, suggesting this species may be able to occupy a wider range of habitats. Hoop net catch data from a long‐term monitoring project in the Colorado River were used to compare catches of two size classes: juvenile/subadult (<200 mm total length [TL]) and adult humpback chub (≥200 mm TL). Catch information was analysed on an individual net scale and on a geological segment scale using generalized linear mixed models. There was no difference in juvenile/subadult humpback chub catch between hoop nets set in rocky habitat compared with habitat with only fine sediment. Humpback chub catch for all life stages in a river segment characterized by silt banks exceeded or was not significantly different from catch in rocky segments. This case study demonstrates the importance of revisiting habitat descriptions, sampling in areas outside known or expected habitat and incorporating new data related to range expansion or habitat changes in recovery strategies to better describe and protect habitats that can support imperilled species.

Freshwater ichthyofauna of wetlands in Tablas Island, Romblon, The Philippines

The Philippines is a hotspot for biological variety and a hub for endemism on a worldwide scale. Despite this, most of the research has focused on terrestrial and marine biodiversity, with little knowledge of freshwater fish diversity and status. There has been no systematic research on these species in Romblon. As a result, this research was conducted. This study aims to evaluate the freshwater fishes of Tablas Island, Romblon, utilizing modified hoop nets, gill nets, scoop nets, and hook and line. A total of 44 species belonging to 36 genera and 19 families were identified. They are often found in rivers, and streams, while most of them are native to the Philippines, where they are being eaten by natives. The IUCN Red List placed the majority of these species in the Least Concern category. The dominating species was Gambusia affinis, with Giuris margaritaceus being the most frequent across all sites. A new locality record of an indigenous minnow species (Barbodes hemictenus) was found. The ichthyofauna of Tablas Island is diverse, with local species dominating. Only two introduced species were identified as threatened (Vulnerable). On the other hand, the rest were classified as Least Concern, Unknown, Not Evaluated, and Data Deficient.

RURAL TURTLES: ESTIMATING THE OCCUPANCY OF NORTHWESTERN POND TURTLES AND NON-NATIVE RED-EARED SLIDERS IN AGRICULTURAL HABITATS IN CALIFORNIA'S SACRAMENTO VALLEY AND SACRAMENTO-SAN JOAQUIN RIVER DELTA

The Northwestern Pond Turtle (Actinemys marmorata; WPT) was once widespread throughout the Sacramento Valley and the Sacramento-San Joaquin River Delta. Much of its historical range has been converted into agricultural land, reducing and altering aquatic habitat and surrounding uplands. Red-eared Sliders (Trachemys scripta elegans; RES) have been introduced throughout much of the existing WPT range, particularly near urban centers, potentially competing with WPT for resources. Previous surveys for turtles in central California have primarily focused on rivers, lakes, and protected wetlands. Little is known about where WPT and RES occur in the vast expanses of agricultural land across the Sacramento Valley and Sacramento-San Joaquin River Delta. Using aquatic hoop nets, we surveyed 142 locations (102 irrigation canal sites, 39 wetlands, 1 tidally influenced slough) across 8 counties during the summers of 2018 and 2019. Both species were detected in agricultural habitats. Using occupancy modeling, we estimated that WPT occur at 44 (95% CRI = 38–53) of our trapping sites and RES occur at 51 (41–66) sampled sites. Co-occurrence of these 2 species was rare; the species were found together at only 6 sites. RES were primarily found in restored wetlands near major roads and the Sacramento metropolitan area, whereas WPT were more commonly found farther from urban areas in wider canals. Our work provides a picture of how WPT and RES occupy this modified agroecosystem that can inform future conservation efforts.

Assessing trap bias in the endemic Australian genus of freshwater crayfish,

Freshwater crayfish are among the most endangered animal groups in the world. Appropriate management requires an understanding of sampling bias when assessing their distribution and abundance. We evaluated the effectiveness of a variety of sampling methods for detecting freshwater crayfish (genus Euastacus) in situ and potential biases towards individual-level traits associated with these methods. We also experimentally manipulated the presence of crayfish within opera house traps to determine the effects of trap residency on capture rate and the characteristics of crayfish approaching the traps. Baited hoop nets and baited remote underwater video surveys (BRUVS) detected significantly more crayfish than did unbaited video surveys (RUVS). Crayfish captured in baited hoop nets were significantly larger than were crayfish measured in the BRUV and RUV surveys, suggesting that hoop nets were biased to capturing larger animals. The experiment demonstrated that a greater number of crayfish entered empty rather than occupied traps; however, there were no differences in their body sizes. We highlight the importance of optimising sampling for freshwater crayfish to ensure reliable and robust population estimates. This is of critical importance as many have highly restricted ranges and face numerous threats. We contend that this will assist in informing conservation strategies to protect aquatic species at risk.

A NEW SPECIES OF MYXOBOLUS (CNIDARIA: MYXOSPOREA: MYXOBOLIDAE) FROM THE BLUE SUCKER, CYCLEPTUS ELONGATUS (LESUEUR) (CYPRINIFORMES: CATOSTOMIDAE: CYCLEPTINAE), FROM ARKANSAS.

During 9-10 February 2018 and 21-22 February 2020, 7 adult Blue Suckers, Cycleptus elongatus, were collected by hoop nets from the Red River, Little River County (n = 3), and the Black River, Lawrence County (n = 4), Arkansas, and their gills, gallbladders, fins, integument, other major organs, and musculature were examined for myxozoans. All 7 (100%) were infected with an unknown species of gill-infecting Myxobolus sp. Twenty formalin-fixed plasmodia (cysts) of Myxobolus cloutmani n. sp. were elliptoidal, 407 μm long × 270 μm wide. Formalin-fixed myxospores were orbicular to broadly elliptoidal, 8.7 μm long × 7.8 μm wide. Two polar capsules were pyriform and subequal in size, extending over halfway in the myxospore. The larger polar capsule was 5.5 μm long × 3.1 μm wide, while the shorter was 5.1 × 2.9 μm. A coiled polar filament possessed 5 or 6 coils. The myxospore was 3.7 μm thick in sutural view, with a distinct sutural ridge. Qualitative and quantitative morphological data were from formalin-fixed as well as ethanol-preserved spores, while molecular data consisted of a 2,010 base pair sequence of the partial 18S ribosomal RNA gene and a 2,502 base pair sequence of the partial 28S ribosomal RNA gene. Phylogenetic analysis grouped M. cloutmani n. sp. with the other catostomid-infecting myxobolids. This is the first myxozoan reported from C. elongatus.

Using Population Dynamics to Model Harvest Regulation Impacts to Channel Catfish in the Monongahela River, West Virginia

AbstractChannel Catfish Ictalurus punctatus were collected during 2018 and 2019 from the Monongahela River in West Virginia using hoop nets to estimate population dynamics. Length, weight, sex, fecundity, and age data were obtained from collected individuals. Population characteristics (e.g., relative abundance, size structure, age structure, growth, etc.) were modeled under three proposed length limits of 300, 375, and 450 mm. Simulation results indicated that growth overfishing may occur when exploitation rates reach 36% under a 300‐mm minimum length limit. Furthermore, recruitment overfishing began to occur at 40% exploitation under a 300‐mm minimum length limit. Additionally, simulations suggest that no recruitment or growth overfishing occur at minimum length limits of 375 mm or 450 mm until extremely high exploitation levels (>90%) are reached. Thus, future consideration should be given for implementation of a 375‐mm minimum length limit of Channel Catfish in the Monongahela River to prevent growth and recruitment overfishing while also ensuring anglers are still able to harvest Channel Catfish.

Explaining Channel Catfish Population Characteristics in Ohio Reservoirs

AbstractNorth American fisheries management agencies commit considerable resources to managing reservoir fisheries for Channel Catfish Ictalurus punctatus, which often includes stocking. However, Channel Catfish population characteristics often vary greatly among reservoirs, resulting in variable and unpredictable fishery quality. We sampled Channel Catfish populations in 44 Ohio reservoirs with tandem, baited hoop nets to understand relationships among population characteristics (density, as CPUE from hoop nets; growth, as mean length at age 7; mortality, as total annual mortality from catch‐curve analysis; and size structure, as proportional size distribution), stocking, and the relationships between these characteristics and reservoir size (as surface area), predator density (as Largemouth Bass Micropterus salmoides electrofishing CPUE), and productivity (as chlorophyll‐a concentration). We used multiple linear regression and an information theoretic approach to select the most parsimonious models for explaining observed variation in Channel Catfish density, growth, mortality, and size structure. We found that population density varied greatly among our study reservoirs, and none of our models sufficiently explained variation in density. Reservoir size and the interaction between reservoir size and population density explained the most variation in Channel Catfish growth, but productivity was also important. Small reservoirs (≤101 ha) had low to moderate densities and growth was uniformly slow; however, in larger reservoirs, lower densities resulted in faster growth. Growth increased as productivity increased. Total annual mortality was uniformly low (<0.26) but increased with density. Faster growth led to populations with larger size structures. These outcomes show that the largest Ohio reservoirs (≥406 ha) are the most suitable for supporting populations with fast growth and large size structures. Dense populations (CPUE > 50 Channel Catfish/net set) resulted in slower growth, greater mortality, and poor size structure. Future research to understand natural recruitment in reservoir Channel Catfish populations could be important for explaining variation in density.

Indexing Reservoir Channel Catfish Population Density and Size Structure with Tandem, Baited Hoop Nets

AbstractFisheries managers efficiently sample reservoir Channel Catfish Ictalurus punctatus populations with tandem, baited hoop nets. However, catchability (the fraction of a fish stock caught with a defined unit of effort) of Channel Catfish with this gear and the size selectivity of this gear are not fully known. Furthermore, scientists have not identified a standard sampling period that maximizes catches while minimizing variation in catchability. Here, we estimated Channel Catfish population density (number/ha) and catchability with tandem, baited hoop nets using mark–recapture methods in three Ohio reservoirs during May–July 2016–2018. We tested for differences in catchability (1) among reservoirs; (2) among 50‐mm length categories; and (3) by week. We then tested CPUE as an index of density by simulating the sampling of populations with different densities based on observed variation in catchability and estimating the statistical power to detect density differences. We found that total catchability differed among study reservoirs, among length categories, and among sampling events but did not consistently change during the May–July sampling period. Catchability of 50‐mm length categories did not differ among reservoirs. The greatest catchability was observed for 400–649‐mm Channel Catfish. Our power analysis showed that we could detect a large (>2:1 effect sizes) difference in density with 80% power by using 20 or more sample sites. Furthermore, our length‐category‐specific catchability estimates provide information to reduce bias in size structure, growth, and mortality estimates derived from Channel Catfish samples collected with tandem, baited hoop nets. We encourage further development, validation, and application of tandem, baited hoop nets to better understand differences in reservoir Channel Catfish densities and size structures.

Gear specific catch rates and size structure of channel catfish in the Upper Mississippi River

AbstractChannel catfish are important to the Mississippi River (i.e., ecologically, commercially, and recreationally). The dynamic rate functions (recruitment, growth, and mortality) of the population are important to proper management. However, different gears can produce varying estimates of these vital rates (e.g., size selectivity or age selectivity). We evaluated the effectiveness of three commonly used gear types for sampling channel catfish. Sampling was completed following United States Army Corps of Engineers' Long‐Term Resource Monitoring (LTRM) element sampling protocol; pulsed direct current daytime electrofishing, baited 37 mm hoop nets (large hoop net), baited 18 mm hoop nets (small hoop net), and a tandem hoop net set that included one large and one small hoop net. A total of 65,222 channel catfish were collected from 1993 to 2017. Channel catfish catch rates were lowest using daytime electrofishing and large hoop nets, while tandem hoop nets and small hoop nets had higher catch per unit effort (CPUE). Furthermore, tandem hoop nets collected a broader size distribution of channel catfish in comparison to daytime electrofishing, large hoop nets, and small hoop nets. As such, we recommend that tandem hoop nets should be used to evaluate channel catfish populations in the Upper Mississippi River as well as other riverine systems.

Population Dynamics and Simulated Effects of Length‐Based Trophy Regulations for Flathead and Channel Catfish in the Lower James River, South Dakota

AbstractCatfish are popular with anglers fishing southeastern South Dakota rivers, and a group of anglers has expressed concern about the perceived overharvest of trophy‐size catfish. However, existing data are insufficient for determining whether Flathead CatfishPylodictis olivarisand Channel CatfishIctalurus punctatusare being overharvested. Our objective was to determine the population dynamics of Flathead and Channel catfish and model potential outcomes of length‐based trophy regulations (one fish and no fish harvested over 610 mm) in the lower James River, South Dakota. Multiple gears were used to collect Flathead Catfish (low‐frequency electrofishing and trotlines) and Channel Catfish (baited hoop nets and low‐frequency electrofishing) during 2018, and samples were augmented with angler‐caught catfish collected from three angling tournaments. Pectoral spines were removed from a subsample of fish for age estimation; 305‐mm and larger fish received a Carlin dangler tag with a reward value of US$0, $10, or $100. Growth rates were slow to moderate for Flathead Catfish and moderate for Channel Catfish. Trophy‐size Flathead Catfish (TL ≥ 1,020 mm) were sampled, but few of the collected Channel Catfish exceeded preferred length (TL ≥ 610 mm). Total annual mortality was estimated at 25.7% for Flathead Catfish and 25.2% for Channel Catfish. Exploitation estimated from angler reward tag returns was less than 1% for each species. Yield‐per‐recruit models indicated that a regulation specifying one fish over 610 mm would slightly reduce yield for both species but would only increase the number of memorable‐length Flathead Catfish (860 mm) and Channel Catfish (710 mm) by less than 1%. A no‐harvest regulation would substantially reduce yield of Flathead Catfish and would increase the number of memorable‐length Flathead Catfish by approximately 2% and Channel Catfish by less than 1%. Information obtained during this study suggests that current Flathead and Channel Catfish populations have limited trophy potential and that length‐based trophy regulations would have limited impact on the abundance of large catfish in the lower James River.

Freshwater turtle bycatch research supports science‐based fisheries management

AbstractAlthough it is sometimes difficult for researchers to ensure that their work is used by resource managers to make informed decisions, an example where this knowledge–action gap has been breached is in research published inAquatic Conservation: Marine and Freshwater Ecosystems(AQC) – among other journals – that has assisted fisheries managers in identifying strategies for reducing freshwater turtle bycatch in commercial hoop net fisheries in Ontario, Canada.Research published in AQC has provided evidence towards a simple and effective method for preventing turtle bycatch mortality in hoop nets, which could be adopted by the fishers. Other research published in AQC evaluated the effect of bycatch mortality on the probability of persistence of turtle populations with population viability analyses, and outlined the need to minimize bycatch mortality to prevent local extirpation. Nine other papers have been published on freshwater turtle bycatch in Ontario, furthering our knowledge on this issue including seasonality and temperature effects on catches, other net modifications, post‐release effects and assisted recovery, and the perspectives of fishers.The research results were presented to local resource managers with further discussions involving industry and stakeholders to minimize turtle bycatch mortality. Over several years, researchers have provided information to resource managers; however, when an incident of high turtle mortality caught the public eye, the research was readily available and changes in regulations were quick to occur.Reasonably good communication among researchers, resource managers, industry, stakeholders, and the broader public allowed the rapid implementation of regulations to mitigate freshwater turtle bycatch mortality and bridged the knowledge–action gap between researchers and resource managers.Both articles published in AQC had practical conservation impacts and were influential in providing local resource managers with feasible solutions, and the impetus to change regulations. These impacts extended to other jurisdictions and their monitoring programmes, where methods to reduce turtle bycatch mortality were also implemented.

Catfish Population Characteristics among River Segments with Altered Fluvial Geomorphic Conditions in the Missouri River, Nebraska, USA

AbstractAlteration of river systems around the world has created novel environments that have been fragmented, homogenized, or transformed from their natural state, thus posing challenges for understanding how fish populations function. The Missouri River has undergone significant alteration through reservoir construction and channelization. Channel Catfish Ictalurus punctatus and Flathead Catfish Pylodictis olivaris both reside in various fragmented sections of the river, and there is a substantial gap in knowledge of how catfishes synchronously function in this modified system. From 2009 to 2018, we assessed catfishes with baited hoop nets and low‐frequency electrofishing among four different areas: upper and lower unchannelized segments and upper and lower channelized segments. Differences in population demographics and dynamics occurred for both species among segments. Both the highest and lowest relative abundances for Channel Catfish occurred in channelized segments, and Flathead Catfish relative abundance was lowest in both unchannelized segments. Subadult growth rates for both catfish species were greater in channelized segments. Channel Catfish mortality was highest in channelized segments, which was consistent with the maximum ages found in channelized (age 9) versus unchannelized (age 15) segments. High‐flow events in 2010 and 2011 led to an increase in recruitment, but populations declined in subsequent years. This long‐term assessment revealed spatial and temporal differences in population dynamics among varying levels of anthropogenic alteration. Our study illustrates how river modification and extreme climatological events may impact and structure catfish populations. These data provide a basis for assessing catfish throughout the Missouri River system and offer insight into how catfish populations in other altered large‐river systems might function.

Comparison of Growth, Body Weight, and Contribution to Recreational Creel of Channel Catfish and Channel Catfish × Blue Catfish Hybrids in Two Public Put–Grow–Take Fisheries in Kansas

AbstractFisheries managers in Kansas face increasing challenges to diversify angling opportunities and increase appeal to a broader audience. One method of diversification is the development of alternative fisheries to complement those that are already established. To address this desire for diversification, age‐1 Channel Catfish Ictalurus punctatus and age‐0 Channel Catfish × Blue Catfish I. furcatus hybrids were stocked in equal numbers at approximately equal sizes in two Kansas impoundments to compare growth, body weight, and return to creel in public put–grow–take systems. Catfish were sampled over a 3‐year period with a suite of gears, including gill nets, baited tandem hoop nets, and low‐frequency electrofishing. Additionally, creel surveys were conducted at both impoundments in 2015 and 2016 to estimate angling success. Hybrid catfish exhibited more rapid growth than Channel Catfish and reached the 381‐mm minimum harvest length approximately 267–343 d earlier in both impoundments. Channel Catfish weight was 1.01–1.06 times the hybrid catfish weight at 280 mm, 0.96–0.99 times the hybrid weight at 410 mm, and 0.88–0.95 times the hybrid weight at 610 mm. Angler success did not differ between types of catfish in either impoundment during either year, but low sample sizes prohibited thorough comparison. More Channel Catfish (N = 623) than hybrid catfish (N = 297) were encountered with sampling gears, but differences in catch rate by gear were minimal, with no discernable patterns. Results presented herein provide evidence that hybrid catfish might be suitable for public put–grow–take fisheries. Additionally, growth and production benefits of hybrid catfish may make them a more economical option than Channel Catfish in these types of fisheries.

Bat (Mammalia: Chiroptera) diversity, dominance, and richness in the southwestern region of Bhutan with three new records for the country

Bats are ecologically crucial as they are good pollinators and pest controllers, but are less known in Bhutan. We investigated bat diversity and richness in broadleaved forests of southwestern Bhutan. Fieldwork was carried out from July 2016 to April 2017 using mist nets and hoop nets. The main objective of the study was to document bat diversity and species richness. We captured 157 bats of 10 species belonging to four families. Two species (Myotis siligorensis Horsfield, 1855 and Rhinolophus affinis Horsfield, 1823) accounted for almost 52% of the total captures. Species richness of bats differed depending upon habitat types. Myotis siligorensis was captured more often from broadleaved forests whereas Rhinolophus macrotis Blyth, 1844 and Rhinolophus affinis were common around human settlements. The present study contributed three new records for Bhutan which increased the bat diversity from 65 to 68 species. We conclude that the southwestern region, especially Chukha District, could be one of the bat diversity hotspots in Bhutan.

Mono- vs multifilament baited conical hoop (tangle) nets: Effects on portunid catches and marine debris

Small, baited polyamide (PA) hoop (tangle) nets are a popular recreational fishing gear for targeting portunids (Scylla serrata and Portunus armatus) in southeastern Australia and are comparable to other tangle and entrapment gears used more broadly throughout tropic-temperate regions. While their selectivity is appropriate for legal-sized portunids (≥85 and ≥60 mm carapace length; CL, respectively) and bycatches are low, hoop nets can be damaged and lose twine as marine debris. We investigated an applied solution to this problem here by fishing conventional multifilament hoop nets (made from 0.98-mm diameter–Ø white twisted PA twine) against those made from three diameters (0.65–0.86 mm) of clear monofilament PA twine—a material currently prohibited throughout south-eastern Australian net-based gears owing to an historical perception of excessive efficiencies. Compared to the multifilament hoop nets, all three monofilament hoop nets similarly maintained diel catches of S. serrata but retained significantly fewer (by 67–92%) P. armatus, and without affecting non-target catches. Irrespective of the targeted species, there was less hoop-net damage and twine lost (reduced by 69–99% from an average of 114 mm lost 3-h overnight deployment–1 for the conventional hoop nets) among monofilament hoop nets, which was also negatively correlated to their twine diameter. The results were attributed to the greater stiffness and abrasion resistance of monofilament limiting (i) entangling among smaller P. armatus and (ii) breakage when targeting both species, respectively. For this fishing gear, monofilament clearly is not associated with greater efficiency as perceived; rather it might be encouraged as an inexpensive solution for mitigating marine debris among hoop nets when targeting S. serrata.

Effects of twine material on the marine debris and relative ghost fishing of portunid hoop (tangle) nets

Portunids are important to recreational fisheries in Australia and typically are harvested by baited gears. Most of these baited gears are considered environmentally benign, although small conical hoop (tangle) nets fished in southeastern Australia sometimes are damaged and lose twine, which becomes marine debris. Substituting conventional multifilament polyamide (PA) twine with alternative multi-monofilament and monofilament PA twines in hoop nets can dramatically reduce marine debris, but there remain unanswered questions concerning the relative fishing power of alternative twines among derelict hoop nets. This study addresses the shortfall in data by comparing the efficiencies and damage to replicate hoop nets made from the three twines and left to fish for short (one and two days), medium (three to five days) and long (ten and fourteen days) soaks. Irrespective of twine material or soak time, all hoop nets entangled the same numbers of giant mud crabs, Scylla serrata implying catch saturation within two days. Only four other animals were caught (all yellowfin bream, Acanthopagrus australis) and all died. At least some replicates of all hoop nets were damaged and lost twine, but this was greatest among the multifilament (up to a maximum of 9.3 m hoop-net deployment−1), followed by the multi-monofilament (up to 7.4 m hoop-net deployment−1) and monofilament hoop nets (1.4 m hoop-net deployment−1). Replacing the existing multifilament twine in hoop nets with monofilament when targeting S. serrata would maintain catches and minimise marine debris during conventional soaks, without increasing ghost fishing over the short term.

Distribution and Abundance of the Alligator Snapping Turtle (Macrochelys temminckii) in Southwestern Louisiana

High harvest rates during the 1900s led to declines of Macrochelys temminckii (Alligator Snapping Turtle) throughout much of its range. Recent research to determine the status of Alligator Snapping Turtles has been completed in some regions of Louisiana, but information is lacking for the southwestern region of the state. To determine the distribution and abundance of Alligator Snapping Turtles in southwestern Louisiana, we conducted trapping efforts in the lower Calcasieu, Mermentau, and lower Sabine river systems from March 2012 through October 2013 using baited hoop nets. In 731 trap nights, we captured 14 individuals (2 M, 4 F, 8 Juv) in the Mermentau and Calcasieu river systems. Our trapping efforts did not detect Alligator Snapping Turtles at Sabine River sites, although one individual was found dead on a fishing hook of a hanging limb line. Our catch per unit effort (CPUE) was 0.021 across the 3 river drainages. Population levels appear to be smaller than observed elsewhere in Louisiana and in neighboring southern states. We recommend that future surveys be conducted to determine population trajectories and that a system be implemented for monitoring commercial fishing bycatch and recreational harvest.

Evaluation of Unbaited Hoop Nets for Simultaneously Assessing Channel Catfish and Flathead Catfish populations in the Minnesota River

AbstractFisheries managers desire efficient sampling methods with sufficient precision for monitoring ictalurid catfish populations. For this study, I conducted single unbaited hoop‐net surveys in the Minnesota River to evaluate the efficacy of simultaneously assessing stock‐size (≥280‐mm) Channel Catfish Ictalurus punctatus and quality‐size (≥510‐mm) Flathead Catfish Pylodictis olivaris populations. I compared catch rates and length‐frequency distributions among months (April–September) and used resampling procedures to estimate the number of hoop‐net samples needed to achieve desirable precision of catch rate estimates and adequate statistical power. Catch rates (mean ± SE) were 2.1 ± 0.3 fish/net‐night for Channel Catfish and 0.8 ± 0.1 fish/net‐night for Flathead Catfish. Resampling procedures demonstrated that desirable precision (i.e., relative SE ≤ 25) and adequate statistical power (≥0.80 with α = 0.10) to detect 50% reductions in mean catch rates with two‐tailed t‐tests could be achieved for both species with as few as 68 hoop‐net samples during August. Unbaited hoop nets are effective for simultaneously assessing Channel Catfish and Flathead Catfish populations in the Minnesota River, and conducting surveys during August provides the best balance between catch rate and precision while minimizing perceived environmental and behavioral biases. However, the amount of sampling effort needed to detect small population changes (<50%) and to collect sufficient sample sizes for age and growth analyses may be logistically prohibitive. This study emphasizes the importance of evaluating precision and statistical power of sampling methods so that fisheries managers can identify the most suitable methods for their specific objectives.

Humpback Chub (Gila cypha) Range Expansion in the Western Grand Canyon

The Colorado River in the Grand Canyon holds the largest remaining population of Humpback Chub Gila cypha, an endangered fish endemic to the Colorado River basin. Early surveys in the 1990s found that most Humpback Chub occupied the Little Colorado River and nearby areas in the mainstem Colorado River and were uncommon in the western Grand Canyon (below Kanab Creek, at river kilometer [rkm] 257.2). From 1939 to 2002, the Colorado River was typically inundated by Lake Mead to rkm 407 (at full pool). Since 2000, Lake Mead water levels have declined, and the current inflow is located almost 100 km downstream at rkm 503.1. Thus, the Arizona Game and Fish Department (AGFD) extended its system-wide monitoring downstream to Pearce Ferry rapid (rkm 478.6) in 2011. Electrofishing is relatively inefficient at capturing Humpback Chub, but a small number of captures from 2011 to 2015 in the western Grand Canyon suggested that the Humpback Chub may have expanded its range downstream. Subsequently, hoop nets were added to AGFD system-wide monitoring in 2016 to better describe Humpback Chub distribution. The distribution of Humpback Chub observed in 2016 and 2017 differed from previous descriptions; we documented relatively large numbers of Humpback Chub, including age-0 fish, in the western Grand Canyon and observed the highest catches downstream of Diamond Creek (rkm 389.1). This suggests that a recent range expansion has occurred and that Humpback Chub in the western Grand Canyon do not utilize the Little Colorado River for reproduction and might therefore constitute a new subpopulation.