Passive Integrated Transponder Tags Research Articles

Effectiveness of fishways on the Pinka Stream and the Rába River, Central Europe: An evaluation with species from the order Cypriniformes

AbstractThis study assessed the functional effectiveness in terms of passage proportion of three fishways, one nature‐like bypass, one partly nature‐like bypass and partly technical pool‐type and one completely technical, on the Pinka Stream and Rába River in Western Hungary. Radio frequency identification with passive integrated transponder tagging was used to collect data on the upstream passage. A total of 2976 tagged individuals were included in the study; 2863 individuals were either barbel (Barbus barbus), nase (Chondrostoma nasus) or chub (Squalius cephalus), which were chosen as model species, and 113 individuals belonged to four other species. There were 540 individuals of the model species and 18 individuals of the other species detected while successfully ascending one of the fishways. The time‐to‐event (survival) analysis of the data of the model species revealed significant species‐specific differences in passage probability between the fishways. The passage probabilities of the barbel were the highest, and those of the nase were the lowest at all three fishways. The findings demonstrate that single‐species evaluations can lead to incorrect conclusions on fishway effectiveness. Technical fishways can be as effective as nature‐like ones, and hybrid solutions (technical fishways combined with nature‐like bypasses) can function as well. The limitations of the study and recommendations for further evaluations are also discussed.

Migratory passage and run size of American Shad and river herring in the Raritan River, New Jersey, USA

AbstractObjectiveRestoration of many populations of anadromous American Shad Alosa sapidissima and river herring (Alewife A. pseudoharengus and Blueback Herring A. aestivalis) has been hampered by the presence of barriers to their spawning migrations and insufficient monitoring of run size. Here, we describe results of a 10‐year (2012–2021) study of American Shad and river herring passage at the Island Farm Weir (IFW), the downstream‐most migration barrier on the Raritan River, New Jersey, United States.MethodsWe used passive integrated transponder tags applied to fish that were captured and released downstream of the IFW to estimate passage rates and migration delays associated with upstream movements through an antenna array on a vertical slot fishway within the weir. By combining estimated passage rates with video monitoring of the total numbers of American Shad and river herring transiting the fishway, we estimated the annual run size below the weir.ResultResults suggest that the fishway on the IFW is moderately effective for American Shad (passage rate = 41%; 95% credible interval [CI] = 21–61%) but ineffective for the smaller‐bodied river herring (passage rate = 0.5%, 95% CI = 0–2%; fallback‐adjusted passage rate = 1.1%, 95% CI = 0.0–4.5%). The IFW may have also delayed the spawning migrations of those fish that did pass, with total passage times ranging from 0.4 to 20.9 days (mean ± standard deviation = 8.2 ± 5.3 days) for American Shad and 15.0 days for the one river herring that passed within the same year that it was tagged. Run size estimates during the study period ranged from 103 to 2624 individuals for American Shad and from 1486 to 53,334 for river herring.ConclusionRestoration of these species in the Raritan River will likely require removal of the IFW or replacement of its current fish passage device with one that increases the passage rates of alosines.

Sport fish movement responses to a littoral zone coarse woody habitat addition

AbstractObjectiveFish movements and distributions throughout an ecosystem are important for understanding ecological interactions, conservation, and management. Coarse woody habitat (CWH) additions are a popular habitat enhancement tool that can influence movements and distributions of fishes; however, behavioral responses in relation to CWH additions are understudied. The objectives of our study were to test for changes in habitat use and behavioral responses of Muskellunge Esox masquinongy, Smallmouth Bass Micropterus dolomieu, and Walleye Sander vitreus to CWH additions in a small inland northern lake over 3 years and to evaluate two common forms of fish tracking to estimate daily movement of these fishes.MethodsWe used passive integrated transponder tag data collected continuously at 10 littoral sites and radiotelemetry data collected biweekly during the summer–fall months prior (2017) and following (2018–2019) CWH addition to examine movement behaviors and estimate daily probability of movement for the three species among lake habitats using multistate models.ResultWalleye were the most likely to remain near CWH, followed by Smallmouth Bass and Muskellunge. All species were more likely to move away from the modified and unmodified littoral zones and were more likely to remain in the offshore zone. Increased movement of fish may be in response to CWH creating a refuge for forage fish and subsequent increases in prey search times.ConclusionOur results suggest that CWH additions may alter established species‐specific annual movements, distributions, and habitat use to differing degrees in ecosystems, as our results differ from other CWH studies. Methodologically, radio‐tagging was most effective for offshore tracking but most labor intensive. Novel passive integrated transponder arrays (less labor intensive once installed) worked well to monitor movement between habitat types in shallow littoral areas. Long‐term monitoring of behavioral changes will be essential to assessing the stability changes caused by these habitat alterations.

Movement patterns of Japanese crayfish revealed by long-term tracking with a passive integrated transponder tag system

Movement patterns of Japanese crayfish revealed by long-term tracking with a passive integrated transponder tag system

Comparisons of donor stray percentages between hatchery‐ and natural‐origin Chinook Salmon and steelhead in the upper Columbia watershed

AbstractObjectiveArtificial propagation of Pacific salmon Oncorhynchus spp. is commonly used to achieve conservation and harvest goals. However, unintended effects of artificial propagation, such as high donor stray percentages, can reduce numbers of adults that return to target areas and also contribute spawners to different populations where they are undesirable. Until recently, it was difficult to assess if hatchery‐origin fish stray rates were atypical because few estimates of stray rates of natural‐origin fish were available. We sought to fill that gap by comparing donor stray percentages of hatchery‐ and natural‐origin Chinook Salmon O. tshawytscha and steelhead O. mykiss from the same locations.MethodsWe used 29,885 last passive integrated transponder tag detections of adult fish to estimate and compare donor stray percentages of hatchery‐origin and natural‐origin Chinook Salmon and steelhead in the upper Columbia River watershed between 2002 and 2018.ResultDonor stray percentages of hatchery‐origin spring, summer, and fall Chinook Salmon and steelhead were <0.3% at the upper Columbia basin scale and similar to natural‐origin donor stray percentages. Only steelhead donor stray percentages were higher for hatchery‐origin adults at the subbasin scale than natural‐origin counterparts and were <22% for all taxa. The percentage of hatchery‐origin steelhead and spring Chinook Salmon released in tributaries were detected at nontarget areas at higher percentages (<63%) than natural‐origin counterparts born in these tributaries. Returning hatchery‐origin and natural‐origin Chinook Salmon and steelhead generally strayed in an upstream direction in similar proportions. Juvenile spring Chinook Salmon that were moved 14–391 km from centralized hatcheries to tributaries for overwintering or final acclimation strayed at a much higher rate than those that completed their incubation, rearing, and acclimation at a single location, but this did not occur with steelhead. Other adaptive management actions that were implemented to reduce straying produced mixed results. A high proportion of stray hatchery‐origin spring Chinook Salmon initially homed to tributary weirs.ConclusionDonor stray percentages of hatchery‐origin Chinook Salmon and steelhead were generally not higher than natural‐origin donor stray percentages at larger spatial scales (e.g., upper Columbia basin and subbasin) but were higher at smaller spatial scales (e.g., tributaries). A variety of approaches can be considered to reduce undesirable production of strays, but most of them involve difficult management trade‐offs.

Biocompatibility of intraperitoneally implanted TEMPO-oxidized cellulose nanofiber hydrogels for antigen delivery in Atlantic salmon (Salmo salar L.) vaccines

Disease outbreaks are a major impediment to aquaculture production, and vaccines are integral for disease management. Vaccines can be expensive, vary in effectiveness, and come with adjuvant-induced adverse effects, causing fish welfare issues and negative economic impacts. Three-dimensional biopolymer hydrogels are an appealing new technology for vaccine delivery in aquaculture, with the potential for controlled release of multiple immunomodulators and antigens simultaneously, action as local depots, and tunable surface properties. This research examined the intraperitoneal implantation of a cross-linked TEMPO cellulose nanofiber (TOCNF) hydrogel formulated with a Vibrio anguillarum bacterin in Atlantic salmon with macroscopic and microscopic monitoring to 600-degree days post-implantation. Results demonstrated a modified passive integrated transponder tagging (PITT) device allowed for implantation of the hydrogel. However, the Atlantic salmon implanted with TOCNF hydrogels exhibited a significant foreign body response (FBR) compared to sham-injected negative controls. The FBR was characterized by gross and microscopic external and visceral proliferative lesions, granulomas, adhesions, and fibrosis surrounding the hydrogel using Speilberg scoring of the peritoneum and histopathology of the body wall and coelom. Acutely, gross monitoring displayed rapid coagulation of blood in response to the implantation wound with development of fibrinous adhesions surrounding the hydrogel by 72 h post-implantation consistent with early stage FBR. While these results were undesirable for aquaculture vaccines, this work informs on the innate immune response to an implanted biopolymer hydrogel in Atlantic salmon and directs future research using cellulose nanomaterial formulations in Atlantic salmon for a new generation of aquaculture vaccine technology.

Reducing the Impact of Tagging on Flatback Turtles Using Double Passive Integrated Transponder Tags

Reducing the Impact of Tagging on Flatback Turtles Using Double Passive Integrated Transponder Tags

Encounter rates and catch‐and‐release mortality of steelhead in the Snake River basin

AbstractObjectiveThe potential influence (i.e., impact rate) of catch‐and‐release fisheries on wild steelhead Oncorhynchus mykiss is poorly understood and is a function of the abundance of wild fish, how many fish are encountered by anglers (i.e., encounter rate), and the mortality of fish that are caught and released. In Idaho, estimates of wild steelhead encounter rates have been derived using the number of wild and hatchery steelhead passing Lower Granite Dam, the number of hatchery steelhead harvested, and the number of hatchery steelhead caught and released. The method includes assumptions that hatchery and wild steelhead have equal encounter rates and catch‐and‐release mortality is 5% for wild steelhead. Here, we investigated wild and hatchery steelhead encounter rates by anglers, estimated catch‐and‐release mortality, and concatenated both aspects to examine how existing recreational steelhead fisheries influence wild steelhead mortality.MethodsWe sampled, tagged, and released 1,251 spawn‐year 2020 (SY2020) and 1,956 spawn‐year 2021 (SY2021) adult steelhead at Lower Granite Dam with T‐bar anchor tags and passive integrated transponder (PIT) tags to estimate steelhead encounter rates and catch‐and‐release mortality. Differences in survival of caught steelhead and those not reported as caught were evaluated using detections at various locations (e.g., PIT arrays, weirs).ResultEstimated encounter rates were 43.7% (95% credible interval; 28.2%, 100.0%) for wild fish and 46.7% (29.6%, 100.0%) for adipose‐clipped fish in SY2020. In SY2021, encounter rates were 47.2% (32.4%, 100.0%) for wild fish and 52.3% (37.1%, 100.0%) for adipose‐clipped fish. Based on detections of caught fish and those not reported as caught, catch‐and‐release mortality of wild steelhead was estimated to be 1.6% (0.0%, 5.2%). Wild steelhead impact rates were 0.7% (0.0%, 2.7%) in SY2020 and 0.7% (0.0%, 2.8%) in SY2021.ConclusionEstimated rates of impact on wild steelhead were consistent and low across years despite major differences in the structure of the fisheries. Our results suggest assuming that encounter rates are equal between hatchery and wild steelhead, and that steelhead catch‐and‐release mortality is 5%, will likely lead to a conservative estimate of the wild steelhead impact occurring from catch‐and‐release fisheries.

Movement of an imperiled esocid fish in an agricultural drain

Animal movement is increasingly affected by human alterations to habitat and climate change. In wetland systems, widespread hydrologic alterations from agriculture have changed the shape, function, and stability of shallow streams and wetland habitats. These changes in habitat quality and quantity may be especially consequential for freshwater fishes such as Grass Pickerel (Esox americanus vermiculatus), a small predatory fish found in disjunct populations across southern Ontario and listed as Special Concern under Canada’s Species at Risk Act. To characterize Grass Pickerel movement response to stream-channel alterations, Fisheries and Oceans Canada implemented a tracking study to monitor the movements of a Grass Pickerel population in an agricultural drain on the Niagara Peninsula (Ontario, Canada). From 2009 to 2013, 2007 Grass Pickerel were tagged and tracked in the 37.3 km2 Beaver Creek watershed using a combination of mark-recapture surveys and eight fully automated passive integrated transponder tag antennas. Most individuals moved within 500 m (i.e., stationary fish) while 16% of the fish moved > 500 m (i.e., mobile fish), with a maximum median movement distance of 1.89 km and a maximum movement distance of 13.5 km (a long-tail distribution). Most movements occurred near the largest confluence where only a few were long-distance upstream or downstream movements. Mobile fish were larger than their stationary counterparts. Grass Pickerel in sites with higher abundance had more mobile fish, implying potential density dependence. Our results highlight that, while a long-distance dispersal ability exists in extant Grass Pickerel populations, the current conditions of riverscapes may prevent these dispersals from occurring. For declining Grass Pickerel populations, limitations to their movement ecology may substantially increase the likelihood of local extirpations.

Small tube-nosed seabirds fledge on the full moon and throughout the lunar cycle.

Many seabirds are attracted to anthropogenic light, and the risk is greater for recent fledglings. Moon phase predicts the probability of stranding (fewer birds strand on the full moon), but it remains uncertain whether moon phase is associated with when young seabirds fledge. Fledging behaviour of nocturnal, burrowing seabirds can be difficult to monitor using traditional methods but can provide insight into environmental factors that influence the risk of stranding. We used passive integrated transponder tags to monitor the fledging dates and times of Leach's storm-petrel (Hydrobates leucorhous) chicks across four breeding seasons (2017, 2018, 2021, 2022) at a major colony in Newfoundland and Labrador, Canada. We also assessed whether moon phase and incident illumination related to fledging date and time. The median fledge time was 1.6 h after sunset (0.6-11.7 h). The median fledge date was 10 October, and fledging dates ranged from 13 September to 13 November. Most importantly, moon phase was not associated with the time and date that Leach's storm-petrel chicks fledged. These results suggest that recently fledged storm-petrels are less attracted to anthropogenic light during high levels of natural illumination, which could indicate periods of higher stranding risk and help concentrate conservation efforts.

Movement and habitat shift responses of juvenile Atlantic Salmon (Salmo salar) to annually permanent stream flooding.

Reservoir formation in a river system changes a lotic environment to more lacustrine conditions, with impacts throughout the ecosystem. In this study, a river reach containing typical salmonid riffle/run habitat was flooded to create a large, deep pool from June to September in each of 3 years. We test the hypothesis that juvenile Atlantic salmon (Salmo salar) with their preference for run/riffle habitats will respond to the transformation to a lentic environment by moving into adjacent lotic environments. Movements of juvenile Atlantic salmon were monitored using a combination of biotelemetry (radio- and passive integrated transponder-tagging) and electrofishing. Results showed that no tracked fish moved away from the created pool habitat. Mass-specific growth rates showed the created pool habitat resulted in net growth of juveniles. The results confirm that fish may not immediately (i.e., at least for an approximate 2 months) respond to rapid, large-scale habitat alterations by moving to find similar habitat conditions outside the altered habitat. This is most probably related to plasticity of behavior and habitat use, and no change in biological conditions to a point that would negatively impact fish growth and survival, for example food availability, competition, or predation. The results also support the hypothesis that the relative importance of physical habitat variables is not universal among streams and populations, therefore limiting the value of applying standard habitat suitability criteria and use.

Examination of Muskellunge overwinter survival and growth in an earthen extensive culture pond

AbstractObjectiveTrack cohort survival, individual growth, and PIT tag retention, as well as relative growth rate, from fall to the following spring for age‐0 Muskellunge Esox masquinongy held in an extensive culture pond.MethodsA total of 806 age‐0 Muskellunge were provided a 12‐mm PIT tag in October 2021 and placed into a 0.1‐ha pond. Individual total length (mm) was recorded for each fish. When the pond was drained in March 2022, an assessment of survival and PIT tag retention was calculated for the cohort, as well as assessment of mean individual growth and relative growth rate.ResultMuskellunge experienced high survival (91.9%) but low individual mean growth (21.7 ± 0.2 mm [mean ± SE]). The mean length of surviving Muskellunge (267.8 ± 0.9 mm) was significantly greater than nonsurviving Muskellunge (251.4 ± 3.1 mm). However, smaller surviving Muskellunge did exhibit slightly improved growth compared to individuals that were initially longer.ConclusionThe results provide an expectation for overwinter survival and growth in an extensive culture pond. This can assist managers in developing expectations on the numbers and length of Muskellunge that will be available to stock the following spring, which has largely been unreported previously.

Food availability leads to more connected contact networks among peridomestic zoonotic reservoir hosts.

The North American deermouse (Peromyscus maniculatus) is a reservoir host for many zoonotic pathogens. Deermice have been well studied, but few studies have attempted to understand social interactions within the species despite these interactions being key to understanding disease transmission. We performed an experiment to determine if supplemental food or nesting material affected social interactions of deermice and tested if interactions increased with increasing population density. We constructed three simulated buildings that received one of three treatments: food, nesting material, or control. Mice were tagged with passive integrated transponder (PIT) tags, and their movement in and out of buildings was monitored with PIT tag readers. PIT tag readings were used to create contact networks, assuming a contact if two deermice were in the same building at the same time. We found that buildings with food led to contact networks that were approximately 10 times more connected than buildings with nesting material or control buildings. We also saw a significant effect of population density on the average number of contacts per individual. These results suggest that food supplementation which is common in peridomestic settings, can significantly increase contacts between reservoir hosts, potentially leading to increased transmission of zoonotic viruses within the reservoir host and from reservoir hosts to humans.

Reappraising the use of forearm rings for bat species

Long-term mark-recapture studies are essential for bat conservation. Over the last decades, millions of bats across Europe and America have been marked with forearm rings for this purpose. Although it is considered a cost-effective method compared to Passive Integrated Transponders (PIT) tags, direct injuries from using forearm rings have been reported since their very first use. Yet, their impact on bats' welfare has not been systematically evaluated and remains a highly controversial issue among the scientific community and policymakers. Here we assess the impact of forearm rings and PIT tags on the health of different bat species. We reviewed 12 years of the existing recapture data of free-ranging bats from NE Spain and evaluated the impact of both marking tools in a captive colony of Carollia perspicillata, by assessing the development of skin lesions and levels of cortisol metabolites in guano (CG) after marking. We report that 55.1 % (435/790) of the recaptured free-ranging bats with forearm rings presented skin lesions. All banded C. perspicillata (n = 22, 100 %) developed skin lesions, whereas none of the PIT-tagged (n = 21) presented lesions. Levels of CG were significantly higher after marking with forearm rings only for one group. Banded C. perspicillata exhibited discomfort-associated behaviours due to forearm rings. Under the “precautionary principle”, we recommend the ban of forearm rings for all bat species until species-specific studies under controlled conditions are performed and approved by a legally constituted ethics committee. Consideration of other long-term marking tools is mandatory to align with global bat conservation strategies.

Stray compositions of hatchery‐origin Chinook Salmon and steelhead in natural spawning populations of the upper Columbia watershed

AbstractObjectiveOne of the biggest concerns of operating hatchery salmonid programs is high straying of returning adults into nontarget populations and the possible homogenization of genetic diversity among populations caused by spawning of stray fish. The composition of hatchery‐origin stray Chinook Salmon Oncorhynchus tshawytscha and steelhead O. mykiss relative to the natural spawning populations, termed “recipient population stray composition,” was evaluated at three spatial scales in the upper Columbia River basin, where stray target limits were 5–10%.MethodsChinook Salmon carcasses were collected from 1999 to 2018 in spawning areas shortly after spawning, and carcasses were examined to determine origin. Steelhead strays and spawning escapement were evaluated using passive integrated transponder tags between 2013 and 2018. We calculated mean stray compositions for 1999–2018 and for 2014–2018.ResultThe mean recipient population stray compositions ranged between 0.02% and 87.35% and increased with decreasing spatial scale. Recipient stray compositions of all taxa at the basin scale were <3%, and summer and fall Chinook Salmon were <0.5%. Stray compositions in subbasins for all taxa ranged between 0.07% and 33.04%. Spring and summer Chinook Salmon exceeded 5% and 10% (summer Chinook Salmon) in some periods in the Entiat and Methow River subbasins, but stray compositions for all Chinook Salmon were <5% in the Wenatchee, Okanogan, and Hanford Reach subbasins for all periods. All steelhead stray compositions in subbasins exceeded 5%, except for those in the Wenatchee subbasin. Stray compositions of spring Chinook Salmon in tributaries ranged between 0.61% and 87.35%. Only the Chiwawa, Icicle, and Twisp rivers were consistently below 10%.ConclusionIn cases where recipient stray management targets were exceeded, some were the result of single hatchery contributions but others were the result of cumulative contributions from multiple hatcheries. Some solutions to reduce recipient stray compositions will likely involve a combination of changes to hatchery, harvest, and habitat management.

Testing the effects of passive integrated transponder (PIT) tags on survival, growth, and tag retention of common nase (Chondrostoma nasus L.) and European barbel (Barbus barbus L.)

Freshwater fish populations are in steep decline, prompting conservation measures and a need for their evaluation. Fish are increasingly monitored with passive integrated transponders (PIT), although the suitability of this tagging technique has not yet been validated for most European target species of conservation. Consequently, this study tested the effect of commonly used 12 mm full-duplex (FDX) PIT tags implanted into the abdominal cavity of common nase (Chondrostoma nasus L.) and European barbel (Barbus barbus L.). A controlled laboratory setup was used to compare survival, growth (both length and weight) and tag retention for two different size classes of sub-adults over 61 days. Survival in the treatment groups was high (96.7–100%) and not statistically different from the control groups (97.5–100%). Highest mortality occurred in small tagged barbel (n = 4; 96.7% survival), while no mortality occurred in large tagged nase. Mean growth rates for tagged fish (2.28 mm, 3.26 g) were similar to those of control fish (2.77 mm, 3.59 g). Overall tag retention rate was 99.0% and tag loss only occurred in nase. The results of this study demonstrate the suitability of PIT injection in the body cavity of nase and barbel > 100 mm TL, which is of high methodological importance given the increasing role these species play in PIT tag-based assessments of freshwater fish conservation in European rivers.

Development and use of a large, flexible antenna to detect fish implanted with passive integrated transponder tags

Development and use of a large, flexible antenna to detect fish implanted with passive integrated transponder tags

Influence of channel geomorphic units on bedload transport and river morphology during low‐magnitude bed‐forming floods coupled with sediment augmentation

AbstractIn this study, we map different types of channel geomorphic units in a sediment‐starved, residual‐flow reach before and after an artificial flood. Bedload particles of a previous sediment augmentation measure are tracked with passive integrated transponder tags, and water depth and flow velocity are recorded across 10 cross‐sections. The analysis focuses on the influence of channel geomorphic units on bedload transport and river morphology. Our hypotheses are (i) that during low‐magnitude bed‐forming floods with sediment pulse migration, existing channel geomorphic units influence bedload transport, and more specifically, (ii) that their type influences the retention rate of bedload particles. Furthermore, we hypothesise that (iii) the density of channel geomorphic units is linked to the hydromorphological diversity of a river section. We provide evidence that supports the first two hypotheses and contradicts the third one. We consider our results to be transferable to similarly regulated reaches based on an analysis of site‐specific conditions and alternative explanatory factors. Further research is needed to transfer the results to varying flood and sediment supply conditions in unregulated reaches.

Distribution and straying of minijack Chinook Salmon released from a captive broodstock hatchery program

AbstractObjectiveProduction of Chinook Salmon Oncorhynchus tshawytscha in hatcheries can unintentionally produce large numbers of age‐1 males, termed "minijacks," which pose ecological and genetic risks to target and nontarget populations. We evaluated the postrelease distribution of minijacks produced in a hatchery captive broodstock program targeting the White River in the Columbia River basin between 2010 and 2015.MethodsFish were passive integrated transponder (PIT)‐tagged in the hatchery (n = 218,555), and databases were searched to determine movement behavior and final detections on fixed PIT tag antenna arrays during the year in which they were released.ResultTwo main movement behaviors were detected: (1) residuals, which moved solely within the subbasin of release; and (2) migrants, which moved downstream into the Columbia River and then reascended the Columbia River in the year of release. Minijacks that reascended fish ladders in the Columbia River were most often detected at Rock Island and Bonneville dams, the nearest and furthest detection locations downstream of the Wenatchee River. Minijacks were last detected in all locations where spring Chinook Salmon spawn in the Wenatchee River subbasin (seven tributaries and one main‐stem area) and also in the Entiat River (an adjacent watershed); minijacks in eight of the nine locations were considered strays. Estimates of minijacks that strayed outside of the White River were between 61% and 100% annually and were influenced by release location. Minijacks were also more abundant than males of all older ages in some of the tributaries during some years. In addition, they were detected in these tributaries during periods when anadromous adults migrate into spawning areas and when spring Chinook Salmon spawn.ConclusionThe large amount of minijack production and the spatial and temporal overlap could pose genetic and ecological risks to both target and nontarget populations and particularly high straying poses risks to the maintenance of between‐population genetic variability.

Passage Efficiency of Alewife in a Denil Fishway Using Passive Integrated Transponder Tags

AbstractPopulations of river herring (Alewife Alosa Pseudoharengus and Blueback Herring A. aestivalis, collectively), once abundant in coastal rivers along the Atlantic coast, have seen precipitous population declines, likely due to many factors, including commercial fishing, habitat degradation, and dam construction. Efforts to restore populations include the construction of fishways at dams, but upstream passage success of fish through fishways is variable. To evaluate passage efficiency of a fishway on the Lamprey River in Newmarket, New Hampshire, Alewives were PIT tagged in 2013 (n = 621) and 2014 (n = 501) and antennas monitored fish in 2013–2015. Potential handling effects, diel movement patterns, and fishway saturation negatively affected passage success. The probability of Alewives successfully passing through the fishway into the river above the dam increased with total length. The estimated probability of passage success of an Alewife of mean total length (280 mm and 292 mm for males and females, respectively) that migrated back to the dam at least 1 year after tagging was 0.63 for males and 0.64 for females. Fishway selectivity presents a potential bias in data collection in freshwater systems, and our results suggest that sampling below a fishway should be coupled with data collected from within and above the fishway for a more complete demographic sample of the migratory population.