Geology topics

Kristine J. Dunker

Publications and source records attributed to Kristine J. Dunker.

7 recordsLinked to original sources

USGS2021

Vulnerability of Pacific salmon to invasion of northern pike (Esox lucius) in Southcentral Alaska

The relentless role of invasive species in the extinction of native biota requires predictions of ecosystem vulnerability to inform proactive management strategies. The worldwide invasion and range expansion of predatory northern pike ( Esox lucius ) has been linked to the decline of native fishes and tools are needed to predict the vulnerability of habitats to invasion over broad geographic scales. To address this need, we coupled an intrinsic potential habitat modelling approach with a Bayesian network to evaluate the vulnerability of five culturally and economically vital species of Pacific salmon ( Oncorhynchus spp.) to invasion by northern pike. This study was conducted along 22,875 stream km in the Southcentral region of Alaska, USA. Pink salmon ( O . gorbuscha ) were the most vulnerable species, with 15.2% (2,458 km) of their calculated extent identified as “highly” vulnerable, followed closely by chum salmon ( O . keta , 14.8%; 2,557 km) and coho salmon ( O . kisutch , 14.7%; 2,536 km). Moreover, all five Pacific salmon species were highly vulnerable in 1,001 stream km of shared habitat. This simple to implement, adaptable, and cost-effective framework will allow prioritizing habitats for early detection and monitoring of invading northern pike.

Alaska↗

USGS2019

Trophic plasticity and the invasion of a renowned piscivore: A diet synthesis of northern pike (Esox lucius) from the native and introduced ranges in Alaska, U.S.A.

The invasion of non-native fishes is a leading cause of extinction and imperilment of native freshwater fishes. Evidence suggests that introduced species with generalist diets have the potential for greatest impacts through competition and predation even though populations are often comprised of specialist individuals. The northern pike (Esox lucius), a predatory fish, has been widely introduced outside its native range for recreational fishing purposes, especially in western North America, and it has been implicated in declines and extirpations of native fishes. We synthesized over 2,900 individual northern pike diet records across 31 waterbodies from the native and introduced ranges in Alaska to quantify the extent of diet specialization and generalization relative to freshwater prey communities. To control for effects of ontogenetic diet shifts, we separately analyzed major size classes of northern pike and inferred and visualized trophic plasticity from Prey-Specific Abundance indices and ordination. Diet generalization was common in northern pike among waterbodies and usually consisted of individuals consuming macroinvertebrates. However, when available, individual northern pike diets showed specialization on fishes, amphibians, small mammals, and dragonflies. The reliance on macroinvertebrate prey by northern pike from small, isolated lakes in the native and invasive ranges suggests that dietary plasticity facilitates persistence of these predators in the absence of preferred fish prey. Broadly, this synthesis supports the hypothesis that trophic plasticity and diet generalization widely occur among invasive and native populations of northern pike which is likely to enhance the probability of introduction success, exacerbate their environmental impacts, and complicate management of this potentially invasive freshwater predator.

Alaska↗

USGS2018

Tradeoffs of a portable, field-based environmental DNA platform for detecting invasive northern pike (Esox lucius) in Alaska

Environmental DNA (eDNA) has improved detection probabilities of aquatic invasive species but lab-based analytical platforms for eDNA analyses slow opportunities for rapid response. Effective approaches that address this analytical bottleneck and improve capacity for rapid response are urgently needed. We tested the sensitivity of a portable, field-based eDNA platform relative to widely used lab-based eDNA approaches for detecting invasive northern pike (Esox lucius) in eight lakes on Alaska’s Kenai Peninsula. The portable, field-based platform takes ~ 1 hr from sample collection to final results and uses a field-based DNA extraction kit, a shelf-stable assay, and a portable real-time PCR thermocycler. Lab-based approaches take days to weeks to months for final results and use lab-based DNA extraction kits, lab-bound assays, and benchtop real-time thermocyclers. We found that the portable, field-based approach was less sensitive than lab-based approaches and was more prone to inhibition, thus increasing potential for false-negatives. Until sensitivity and inhibition issues can be resolved, this portable, field-based approach is best viewed as a complement to rather than a replacement of standard eDNA lab-based approaches.

Alaska↗

USGS2018

The northern pike, a prized native but disastrous invasive: Chapter 14

As the chapters in this book describe, the northern pike Esox lucius Linneaus, 1758 is a fascinating fish that plays an important ecological role in structuring aquatic communities (chapter 8), has the capacity to aid lake restoration efforts (chapter 11), and contributes substantially to local economies, both as a highlysought after sport fish (chapter 12) and as a commercial fishing resource (chapter 13). However, despite the magnificent attributes of this fish, there is another side to its story. Specifically, what happens when northern pike, a highly efficient predator, becomes established outside its natural range? To explore this question, this chapter will investigate observed consequences from many locations where northern pike (hereafter referred to as “pike”) have been introduced and discuss potential reasons why pike, under the right circumstances, can be considered an invasive species.

Book chapter↗

USGS2016

Potential of environmental DNA to evaluate Northern pike ( Esox lucius ) eradication efforts: An experimental test and case study

Determining the success of invasive species eradication efforts is challenging because populations at very low abundance are difficult to detect. Environmental DNA (eDNA) sampling has recently emerged as a powerful tool for detecting rare aquatic animals; however, detectable fragments of DNA can persist over time despite absence of the targeted taxa and can therefore complicate eDNA sampling after an eradication event. This complication is a large concern for fish eradication efforts in lakes since killed fish can sink to the bottom and slowly decay. DNA released from these carcasses may remain detectable for long periods. Here, we evaluated the efficacy of eDNA sampling to detect invasive Northern pike ( Esox lucius ) following piscicide eradication efforts in southcentral Alaskan lakes. We used field observations and experiments to test the sensitivity of our Northern pike eDNA assay and to evaluate the persistence of detectable DNA emitted from Northern pike carcasses. We then used eDNA sampling and traditional sampling (i.e., gillnets) to test for presence of Northern pike in four lakes subjected to a piscicide-treatment designed to eradicate this species. We found that our assay could detect an abundant, free-roaming population of Northern pike and could also detect low-densities of Northern pike held in cages. For these caged Northern pike, probability of detection decreased with distance from the cage. We then stocked three lakes with Northern pike carcasses and collected eDNA samples 7, 35 and 70 days post-stocking. We detected DNA at 7 and 35 days, but not at 70 days. Finally, we collected eDNA samples ~ 230 days after four lakes were subjected to piscicide-treatments and detected Northern pike DNA in 3 of 179 samples, with a single detection at each of three lakes, though we did not catch any Northern pike in gillnets. Taken together, we found that eDNA can help to inform eradication efforts if used in conjunction with multiple lines of inquiry and sampling is delayed long enough to allow full degradation of DNA in the water.

PLoS ONE↗

USGS2014

Introduced northern pike consumption of salmonids in Southcentral Alaska

The impacts of introduced northern pike ( Esox lucius ) on salmonid populations have attracted much attention because salmonids are popular subsistence, sport and commercial fish. Concern over the predatory effects of introduced pike on salmonids is especially high in Southcentral Alaska, where pike were illegally introduced to the Susitna River basin in the 1950s. We used pike abundance, growth, and diet estimates and bioenergetics models to characterise the realised and potential consumptive impacts that introduced pike (age 2 and older) have on salmonids in Alexander Creek, a tributary to the Susitna River. We found that juvenile salmonids were the dominant prey item in pike diets and that pike could consume up to 1.10 metric tons (realised consumption) and 1.66 metric tons (potential consumption) of juvenile salmonids in a summer. Age 3–4 pike had the highest per capita consumption of juvenile salmonids, and age 2 and age 3–4 pike had the highest overall consumption of juvenile salmonid biomass. Using historical data on Chinook salmon and pike potential consumption of juvenile salmonids, we found that pike consumption of juvenile salmonids may lead to collapsed salmon stocks in Alexander Creek. Taken together, our results indicate that pike consume a substantial biomass of juvenile salmonids in Alexander Creek and that coexistence of pike and salmon is unlikely without management actions to reduce or eliminate introduced pike.

Alaska↗

USGS2013

Introduced northern pike predation on salmonids in southcentral Alaska

Northern pike ( Esox lucius ) are opportunistic predators that can switch to alternative prey species after preferred prey have declined. This trophic adaptability allows invasive pike to have negative effects on aquatic food webs. In Southcentral Alaska, invasive pike are a substantial concern because they have spread to important spawning and rearing habitat for salmonids and are hypothesised to be responsible for recent salmonid declines. We described the relative importance of salmonids and other prey species to pike diets in the Deshka River and Alexander Creek in Southcentral Alaska. Salmonids were once abundant in both rivers, but they are now rare in Alexander Creek. In the Deshka River, we found that juvenile Chinook salmon ( Oncorhynchus tshawytscha ) and coho salmon ( O. kisutch ) dominated pike diets and that small pike consumed more of these salmonids than large pike. In Alexander Creek, pike diets reflected the distribution of spawning salmonids, which decrease with distance upstream. Although salmonids dominated pike diets in the lowest reach of the stream, Arctic lamprey ( Lampetra camtschatica ) and slimy sculpin ( Cottus cognatus ) dominated pike diets in the middle and upper reaches. In both rivers, pike density did not influence diet and pike consumed smaller prey items than predicted by their gape-width. Our data suggest that (1) juvenile salmonids are a dominant prey item for pike, (2) small pike are the primary consumers of juvenile salmonids and (3) pike consume other native fish species when juvenile salmonids are less abundant. Implications of this trophic adaptability are that invasive pike can continue to increase while driving multiple species to low abundance.

Alaska↗