John D. Rothlisberger

Aquatic Invasive Species Transport via Trailered Boats: What is Being Moved, Who is Moving it, and What Can Be Done

Abstract Trailered boats have been implicated in the spread of aquatic invasive species. There has been, however, little empirical research on the type and quantity of aquatic invasive species being transported, nor on the efficacy of management interventions (e.g., inspection crews, boat washing). In a study of small-craft boats and trailers, we collected numerous aquatic and terrestrial organisms, including some species that are morphologically similar to known aquatic invasive species. Additionally, a mail survey of registered boaters (n = 944, 11% response rate) and an in-person survey of boaters in the field (n = 459, 90% response rate) both indicated that more than twothirds of boaters do not always take steps to clean their boats. Furthermore, we used a controlled experiment to learn that visual inspection and hand removal can reduce the amount of macrophytes on boats by 88% ± 5% (mean ± SE), with high-pressure washing equally as effective (83% ± 4%) and low-pressure washing less so (62% ± 3% remov...

Ship-borne Nonindigenous Species Diminish Great Lakes Ecosystem Services

AbstractWe used structured expert judgment and economic analysis to quantify annual impacts on ecosystem services in the Great Lakes, North America of nonindigenous aquatic species introduced by ocean-going ships. For the US waters, median damages aggregated across multiple ecosystem services were 138 million per year, and there is a 5% chance that for sportfishing alone losses exceeded 800 million annually. Plausible scenarios of future damages in the US waters alone were similar in magnitude to the binational benefits of ocean-going shipping in the Great Lakes, suggesting more serious consideration is warranted for policy options to reduce the risk of future invasions via the St. Lawrence Seaway.

From Bait Shops to the Forest Floor: Earthworm Use and Disposal by Anglers

ABSTRACT Nonindigenous earthworms are causing large and undesirable changes to forests across the U.S. Upper Midwest. Because earthworms have slow rates of natural spread, and because their distribution remains patchy in many areas, it would be possible to slow the rate of invasion if vectors of introduction can be identified and controlled. Earthworm populations are often found near lakes, and it has been suggested that anglers discarding unwanted bait are a vector for the establishment of new populations. Here, we have surveyed the bait trade and anglers to determine whether bait stores sell known invasive species and whether angler behavior is likely to lead to these species becoming introduced near lakes. All bait stores surveyed sold known invasive species and 44% of anglers who purchase bait dispose of unwanted bait on land or in trash. We conclude that the bait trade and subsequent disposal of worms by anglers constitute a major vector for earthworm introductions. Thus, slowing the spread of invasive earthworms will require efforts to change the species sold at bait stores and/or efforts to change angler behavior.

Future declines of the binational Laurentian Great Lakes fisheries: the importance of environmental and cultural change

It is increasingly clear that future long-term environmental challenges (eg climate change) are being driven by economic and cultural choices, as well as by physical and biological mechanisms. We looked at the extent to which these apply to potential future changes in fisheries in the Laurentian Great Lakes. These fisheries rank among the most valuable freshwater fisheries in the world, but have declined markedly in recent decades. To investigate how these fisheries might develop in the future, we elicited projections from experts in fisheries and related fields. Experts provided assessments on variables relating to US and Canadian commercial (pounds landed) and sport (participation and expenditures) fisheries for the years 2006 and 2025. We measured each experts ability to quantify their uncertainty, producing performance-weighted combinations of expert estimates. All experts expected commercial fisheries to decline from 2006 to 2025, with greater declines in the US (25%) than in Canada (9%). Expectations for sport fishing differed more between lakes and less between countries, with median expected declines ranging from 1% to 13%. Experts attributed expected declines primarily to changes in economic market demands and shifts in societal interests. Increased attention to social and economic trends could aid Laurentian Great Lakes fishery policy and management.

Forecasting the Impacts of Silver and Bighead Carp on the Lake Erie Food Web

Nonindigenous bigheaded carps (Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix; hereafter, “Asian carps” [AC]) threaten to invade and disrupt food webs and fisheries in the Laurentian Great Lakes through their high consumption of plankton. To quantify the potential effects of AC on the food web in Lake Erie, we developed an Ecopath with Ecosim (EwE) food web model and simulated four AC diet composition scenarios (high, low, and no detritus and low detritus with Walleye Sander vitreus and Yellow Perch Perca flavescens larvae) and two nutrient load scenarios (the 1999 baseline load and 2£ the baseline [HP]). We quantified the uncertainty of the potential AC effects by coupling the EwE model with estimates of parameter uncertainty in AC production, consumption, and predator diets obtained using structured expert judgment. Our model projected mean § SD AC equilibrium biomass ranging from 52 § 34 to 104 § 75 kg/ha under the different scenarios. Relative to baseline simulations without AC, AC invasion under all detrital diet scenarios decreased the biomass of most fish and zooplankton groups. The effects of AC in the HP scenario were similar to those in the detrital diet scenarios except that the biomasses of most Walleye and Yellow Perch groups were greater under HP because these fishes were buffered from competition with AC by increased productivity at lower trophic levels. Asian carp predation on Walleye and Yellow Perch larvae caused biomass declines among all Walleye and Yellow Perch groups. Large food web impacts of AC occurred in only 2% of the simulations, where AC biomass exceeded 200 kg/ha, resulting in biomass declines of zooplankton and planktivorous fish near the levels observed in the Illinois River. Our findings suggest that AC would affect Lake Erie’s food web by competing with other planktivorous fishes and by providing additional prey for piscivores. Our methods provide a novel approach for including uncertainty into forecasts of invasive species’ impacts on aquatic food webs.

Using structured expert judgment to assess invasive species prevention: Asian carp and the Mississippi-Great Lakes hydrologic connection.

Recently, authors have theorized that invasive species prevention is more cost-effective than control in protecting ecosystem services. However, quantification of the effectiveness of prevention is rare because experiments at field scales are expensive or infeasible. We therefore used structured expert judgment to quantify the efficacy of 17 proposed strategies to prevent Asian carp invasion of the Laurentian Great Lakes via the hydrologic connection between the Mississippi and Great Lakes watersheds. Performance-weighted expert estimates indicated that hydrologic separation would prevent 99% (95,100; median, 5th and 95th percentiles) of Asian carp access, while electric and acoustic-bubble-strobe barriers would prevent 92% (85,95) and 92% (75,95), respectively. For all other strategies, estimated effectiveness was lower, with greater uncertainty. When potential invasions by other taxa are considered, the effectiveness of hydrologic separation increases relative to strategies that are effective primarily for fishes. These results could help guide invasive species management in many waterways globally.

The scotopic visual sensitivity of four species of trout: a comparative study

Abstract We compared the maximum scotopic visual sensitivity of 4 species of trout from twilight (mesotopic) to fully dark-adapted vision. Scotopic vision is the minimum number of photons to which a fully dark-adapted animal will show a behavioral response. A comparison of visual sensitivity under controlled laboratory conditions showed that brown trout (Salmo trutta) and brook trout (Salvelinus fontinalis) had maximum scotopic thresholds (1.1 × 10−4 μmol · m−2s−1, ∼0.005 lux) 2 times lower than rainbow trout (Oncorhyncus mykiss) and Snake River cutthroat trout (Oncorhynchus clarki bouvieri), which did not differ from each other (2.1 × 10−4 μmol · m−2s−1, ∼0.01 lux). A literature review tended to corroborate these results in that brown trout and brook trout were reported to be more active during the night and at twilight than cutthroat trout and rainbow trout. We also measured light intensity within open versus shaded reaches during the day, dusk, and night in 3 Rocky Mountain streams. The scotopic sensitivity of brown trout and brook trout was sufficient to allow foraging during all twilight periods and under average nighttime light intensities in open and shaded reaches, whereas the scotopic sensitivity of rainbow trout and cutthroat trout may restrict their foraging to relatively bright nocturnal conditions (twilight or a moonlit night). Native cutthroat trout restoration efforts may have greater success in open versus shaded stream reaches in the Rocky Mountains and elsewhere.

Use of structured expert judgment to forecast invasions by bighead and silver carp in Lake Erie

Identifying which nonindigenous species will become invasive and forecasting the damage they will cause is difficult and presents a significant problem for natural resource management. Often, the data or resources necessary for ecological risk assessment are incomplete or absent, leaving environmental decision makers ill equipped to effectively manage valuable natural resources. Structured expert judgment (SEJ) is a mathematical and performance-based method of eliciting, weighting, and aggregating expert judgments. In contrast to other methods of eliciting and aggregating expert judgments (where, for example, equal weights may be assigned to experts), SEJ weights each expert on the basis of his or her statistical accuracy and informativeness through performance measurement on a set of calibration variables. We used SEJ to forecast impacts of nonindigenous Asian carp (Hypophthalmichthys spp.) in Lake Erie, where it is believed not to be established. Experts quantified Asian carp biomass, production, and consumption and their impact on 4 fish species if Asian carp were to become established. According to experts, in Lake Erie Asian carp have the potential to achieve biomass levels that are similar to the sum of biomasses for several fishes that are harvested commercially or recreationally. However, the impact of Asian carp on the biomass of these fishes was estimated by experts to be small, relative to long term average biomasses, with little uncertainty. Impacts of Asian carp in tributaries and on recreational activities, water quality, or other species were not addressed. SEJ can be used to quantify key uncertainties of invasion biology and also provide a decision-support tool when the necessary information for natural resource management and policy is not available.

Limitations of Gravity Models in Predicting the Spread of Eurasian Watermilfoil

The effects of non-native invasive species are costly and environmentally damaging, and resources to slow their spread and reduce their effects are scarce. Models that accurately predict where new invasions will occur could guide the efficient allocation of resources to slow colonization. We assessed the accuracy of a model that predicts the probability of colonization of lakes in Wisconsin by Eurasian watermilfoil (Myriophyllum spicatum). We based this predictive model on 9 years (1990-1999) of sequence data of milfoil colonization of lakes larger than 25 ha (n =1803). We used milfoil colonization sequence data from 2000 to 2006 to test whether the model accurately predicted the number of lakes that actually were colonized from among the 200 lakes identified as being most likely to be colonized. We found that a lakes predicted probability of colonization was not correlated with whether a lake actually was colonized. Given the low predictability of colonization of specific lakes, we compared the efficacy of preventing milfoil from leaving occupied sites, which does not require predicting colonization probability, with protecting vacant sites from being colonized, which does require predicting colonization probability. Preventing organisms from leaving colonized sites reduced the likelihood of spread more than protecting vacant sites. Although we focused on the spread of a single species in a particular region, our results show the shortcomings of gravity models in predicting the spread of numerous non-native species to a variety of locations via a wide range of vectors.

The Gentle Subversive: Rachel Carson and the Rise of the Environmental Movement

In 2004 an editorialist for the New York Times Magazine likened the persistent intolerance of the use of DDT maintained by the U.S. public to the much-publicized persistence of DDT in the environment (Rosenberg 2004). The editorial argued that the extreme stigma placed on DDT by Rachel Carson’s book Silent Spring has impeded and at times prevented African countries from using the chemical to control malaria-transmitting mosquitoes, forcing them to rely instead on less effective, more-expensive pesticides and intervention measures. The claim is then made that this intolerant pressure has cost hundreds of thousands, if not millions, of African children their lives, and that Rachel Carson, because of Silent Spring, is implicated in this tragedy. Silent Spring is thus still an influential, even controversial and perhaps misunderstood, environmental book. The Gentle Subversive: Rachel Carson and the Rise of the Environmental Movement is a recent narrative biography that seeks to shed additional light on Rachel Carson as an author and on the role she and her books played in the U.S. environmental movement of the late 20th century. The book’s author, Mark Hamilton Lytle, is Professor of History and Environmental Studies at Bard College. Appropriately, the book’s 2007 publication year marks the 100th anniversary of Carson’s birth. Two biographies of Carson are already available, one by a close friend, published less than a decade after Carson’s death in 1964 (Brooks 1972), and the other, a lengthy, exhaustively researched volume published a decade ago (Lear 1997). A comparatively slender volume, The Gentle Subversive aims to be different in 2 important ways: format and focus. Formatically, this book is a narrative biography, striving to cast the facts and happenings of Carson’s life as a highly readable story, with ample descriptive detail. The focus of The Gentle Subversive is on Carson as a writer. This is welcome because Carson’s legacy is embodied in the books she wrote, particularly Silent Spring. Adding interest to this approach is Carson’s statement that, while it was clear how she developed her interest in nature (through her mother’s close involvement in her education about the natural world as a child), her fondness and proclivity for writing were a mystery (pp. 252–253). Lytle focuses the biography on this mystery, not solving it, but re porting on its development and consequences. While not surprising, it is ironic that Silent Spring (1962), wherein Carson details man’s insults and injuries to nature through the in discriminant use of pesticides, has produced her most lasting impact on the world. Silent Spring was not Carson’s most critically ac claimed work, nor did it focus on her true passion: the natural history of wild things, especially marine organisms, in their natural habitats. Given its writerly focus, The Gentle Subversive works its way chronologically through each of Carson’s major writing projects, beginning with several short stories she wrote for an acclaimed children’s magazine as an adolescent. Lytle carefully de scribes the development of each project idea and Carson’s preparation and process for bringing each to fruition. In her time Carson’s most acclaimed and popularly successful book was The Sea Around Us, winner of the 1952 nonfiction National Book Award. Her previous book, Under the Sea-Wind, though not as popular, also received high praise from critics. The success of these books established Carson’s reputation as a respected biologist and nature writer, imperative to the eventual impact of Silent Spring. Western North American Naturalist 69(1),