Joseph F. Koonce

Sustainability of Hatchery-Dependent Salmonine Fisheries in Lake Ontario: The Conflict between Predator Demand and Prey Supply

Abstract The offshore fish community of Lake Ontario is presently dominated by intensively managed, nonnative species: Alewife Alosa pseudoharengus and rainbow smelt Osmerus mordax at the planktivore level and stocked salmonines at the piscivore level. Salmonine stocking rates per unit area of Lake Ontario are the highest in the Great Lakes, and fishery managers are concerned about the sustainability of the fishery under present stocking policies, particularly with the recent collapse of the Lake Michigan fishery for chinook salmon Oncorhynchus tshawytscha. In this paper, we describe and present the results of a simulation model that integrates predator demand estimates derived from bioenergetics, prey and predator population dynamics, and a predation model based on the multiple-species functional response, Model reconstructions of historical alewife biomass trends and salmonine diets corresponded reasonably well with existing data for the period 1978–1992. The simulations suggest that current predator de...

Sea Lamprey (Petromyzon marinus) Parasite-host Interactions in the Great Lakes

Prediction of how host mortality responds to efforts to control sea lampreys (Petromyzon marinus) is central to the integrated management strategy for sea lamprey (IMSL) in the Great Lakes. A parasite-host submodel is used as part of this strategy, and this includes a type-2 multi-species functional response, a developmental response, but no numerical response. General patterns of host species and size selection are consistent with the model assumptions, but some observations appear to diverge. For example, some patterns in sea lamprey marking on hosts suggest increases in selectivity for less preferred hosts and lower host survival when preferred hosts are scarce. Nevertheless, many of the IMSL assumptions may be adequate under conditions targeted by fish community objectives. Of great concern is the possibility that the survival of young parasites (parasitic-phase sea lampreys) varies substantially among lakes or over time. Joint analysis of abundance estimates for parasites being produced in streams and returning spawners could address this. Data on sea lamprey marks is a critical source of information on sea lamprey activity and potential effects. Theory connecting observed marks to sea lamprey feeding activity and host mortality is reviewed. Uncertainties regarding healing and attachment times, the probability of hosts surviving attacks, and problems in consistent classification of marks have led to widely divergent estimates of damages caused by sea lamprey. Laboratory and field studies are recommended to provide a firmer linkage between host blood loss, host mortality, and observed marks on surviving hosts, so as to improve estimates of damage.

An Economic Injury Level Approach to Establishing the Intensity of Sea Lamprey Control in the Great Lakes

Abstract Tightening budgetary constraints have forced the Great Lakes Fishery Commission to reevaluate the effectiveness of its program to control sea lamprey Petromyzon marinus in the Great Lakes. One rational option requires setting target levels of control for each of the Great Lakes. This paper is an analysis of an economic injury level approach to setting a target level of control for Lake Ontario. Using a decision support system for the integrated management of sea lamprey in Lake Ontario, we show that calculation of optimal levels of adult sea lamprey is feasible, We calculate that the economic injury level of adult sea lampreys in Lake Ontario is 30,000 fish (95% confidence interval, 16,400–43,600). We predict that this level of abundance could be achieved with an annual application of 9,400 kg of the lampricide TFM. Relative to this standard, Lake Ontario is currently undertreated for sea lamprey control. Implementation of this approach to setting target levels will require further work on estima...

The Sea Lamprey in Lake Erie: a Case History

Abstract Sea lampreys ( Petromyzon marinus ), first reported in Lake Erie in 1921, emigrated from Lake Ontario via the Welland Canal. It was not until the advent of pollution abatement, stream rehabilitation, and salmonid enhancement programs that sea lampreys proliferated. The Great Lakes Fishery Commission (GLFC), in co-operation with state, provincial, and federal fisheries agencies, implemented an integrated sea lamprey management (IMSL) plan for Lake Erie in 1986. Suppression of sea lampreys was nearly immediate, as indicated by declining larval-, parasitic-, and spawning-phase abundance, while survival of lake trout ( Salvelinus namaycush ) was markedly improved. Consistent with their vision statement, the GLFC began reducing lampricide use by the mid-1990s, while increasing reliance on alternative control methodologies. Reduction of treatment effort coincided with the development of new lampricide application techniques and treatment selection criteria, in addition to heightened regional concern for the impact of lampricide on non-target species. Subsequently, Lake Eries sea lamprey numbers have rebounded, and marking rates on lake trout have approached pre-control levels. It is hypothesized that Lake Eries rising abundance is primarily fuelled by untreated and residual larval populations, although some migration of parasitic-phase sea lampreys from Lake Huron is suspected. Model simulations infer that treatment effort on Lake Erie was sub-optimal from 1995 to 1998. Beginning in 1999, the GLFC enhanced measures to identify and control sources of sea lampreys. Based on historical abundance patterns and model results, it is anticipated that intensified management in Lake Erie will reduce sea lamprey numbers and provide an opportunity for lake trout restoration.

The History of Sea Lamprey Control in Lake Ontario and Updated Estimates of Suppression Targets

Abstract The Great Lakes Fishery Commission successfully coordinated fishery management and delivered an international program of sea lamprey ( Petromyzon marinus ) control and assessment that facilitated the rehabilitation of lake trout ( Salvelinus namaycush ) and development of a salmonid fishery in Lake Ontario during 1971 to 1999. During the 1980s and 1990s, the integrated management of sea lampreys (IMSL) strategy optimized control and assessment techniques and refined the stream selection process. The program focused primarily on the juvenile life stage (larval phase) through the application of the selective lampricide 3-trifluoromethyl-4-nitrophenol (TFM) to tributaries of the lake, although the addition of barriers to Lake Ontario tributaries appears to have reduced the reliance on TFM. By 1999, IMSL had eliminated sea lampreys in 20 of the 57 tributaries with historical records of production. Accordingly, the abundance of spawning phase sea lampreys showed a significant downward trend, and substantial declines in marking rates for large lake trout were observed. Targets for control were established through the lake trout rehabilitation plan, fish community objectives, and simulation models incorporating an economic injury level (EIL) approach. The EIL for sea lamprey control is the point in which more treatment is not economically justified. The updated IMSL model developed for Lake Ontario provided a tool to support trade-off analysis to estimate target levels of sea lamprey abundance relative to lake trout harvest. Comparison of model predictions and trends in spawning phase abundance revealed general agreement, but also pointed to inconsistencies that merit further investigation. The EIL of control based on the entire treatment history is 8,100 kg TFM per year, which produces a treatment residual of 4,100 adult sea lampreys. Given recent estimates of transformer production from the Niagara River, the annual contribution from untreated sources is estimated to be in the range of 10,000 to 15,000 adult sea lampreys. The target level (EIL) for adult sea lampreys in Lake Ontario is thus 14,100 to 19,100. Over the past 10 years, Lake Ontario TFM treatments have averaged 4,600 kg per year.

Viral hemorrhagic septicemia virus infection in Yellow perch, Perca flavescens, in Lake Erie

ABSTRACT Viral hemorrhagic septicemia virus (VHSV) infects wild and hatchery fish in Europe, Japan, and the Great Lakes and Pacific regions of North America. The virus was associated with a large die-off of yellow perch, Perca flavescens, in Lake Erie in 2006. To determine the infection pattern of VHSV, we sampled yellow perch during the spring, summer, and fall of 2007 and 2008 in the central basin of Lake Erie during routine sampling by the Ohio Division of Wildlife with bottom trawls in nearshore, mid-depth, and offshore locations near the Chagrin River. The Ohio Department of Agricultures Diagnostic Laboratories and the U.S. Fish and Wildlife Services La Crosse Fish Health Center tested for VHSV from homogenized samples obtained from yellow perch kidney, spleen, and brain. At each lake sample location, we also measured temperature, dissolved oxygen, and conductivity. In both years, we found yellow perch infected with VHSV during a threeweek period starting in the last week of spawning to early June. A high proportion of adult male and female yellow perch tested positive for VHSV during the infection period in our sample population. Infection appeared to be associated with temperatures between 12 and 18 °C and with significantly higher yellow perch densities during spawning. No large mortalities of yellow perch were observed during the VHSV infection period in 2007 and 2008.

Multicriteria Bayesian Analysis of Lower Trophic Level Uncertainties and Value of Research in Lake Erie

Human activities have severely disrupted the Lake Erie ecosystem. Recent changes in the structure of the lower trophic level associated with exotic species invasions and reduced nutrient loading have created ecological uncertainties for fisheries management. Decisions that naïvely assume certainty may be different and suboptimal compared to choices that consider uncertainty. Here we illustrate how multiobjective Bayesian decision analysis can recognize the multiple goals of management in evaluations of the effect of ecological uncertainties on management and the value of information from ecological research. Value judgments and subjective probabilities required by the decision analysis were provided by six Lake Erie fishery agency biologists. The Lake Erie Ecological Model was used to project the impacts of each combination of management actions and lower trophic level parameter values. The analysis shows that explicitly considering lower trophic level uncertainties can alter decisions concerning Lake Erie fishery harvests. Of the research projects considered, investigation of goby predation of zebra mussels (Dreissena sp.) and lakewide estimation of secondary production appear to have the greatest expected value for fisheries management. We also find that changes in the weights assigned to management goals affects decisions and value of information more than do changes in probability judgments.

Factors Affecting Accuracy of Stream Channel Slope Estimates Derived from Geographical Information Systems

Abstract Stream channel slope is often a critical component of geographical information systems (GIS)-based models of preferred habitat of aquatic species, but the relative accuracy of various GIS slope derivation methods is not well established. We examined the accuracy of GIS-derived stream slopes for a set of stream reaches in Idaho and Ohio. We also used the Ohio data set to examine in more detail the effects of stream reach length, source of GIS file representing the stream path (“shapefile”), and digital elevation model (DEM) resolution on the accuracy of GIS-derived slopes. The accuracy of GIS-derived slopes in the Ohio dataset improved with increasing reach length, but we could not draw any consistent conclusions about the effect of DEM resolution or shapefile. We present a simple and efficient method for improving GIS-derived slopes by identifying probable elevation errors in the GIS-derived longitudinal stream profiles. The resulting derived slopes were improved in all cases; the slopes derived ...

Predicting Sea Lamprey (Petromyzon marinus) Ammocoete Habitat Using Geographic Information Systems

ABSTRACT The sea lamprey (Petromyzon marinus) is an invasive, parasitic species with a long history of decimating fisheries in the Laurentian Great Lakes. The sea lamprey life cycle consists of stream larval ammocoete, open water parasitic, and adult spawning phases. Population control of sea lamprey is achieved mainly through the application of chemical lampricides that target the sedentary larval stage. The physical characteristics of preferred ammocoete habitat are well defined at the sub-reach scale (< 50 m). We tested whether the spatial distribution of beds of preferred ammocoete habitat depends upon a specific set of geomorphic variables (field-measured slope, and geographic information system (GIS)-derived curvature, radius of curvature, presence of a confluence, and valley wall type). We tested for this relationship at several spatial scales of stream length ranging from 50 m to 300 m, on the East Branch of the Chagrin River, Ohio, USA, a tributary stream to Lake Erie. Of the five geomorphic variables tested, field-measured slope and radius of curvature influence the probability of a stream segment containing preferred habitat at a stream segment length of 50 m. We found no relationships at longer stream segment lengths. GIS-estimated slopes were not sufficiently accurate at such short segment lengths, so the final model included radius of curvature only. These results are applicable to the Empiric Stream Treatment Ranking (ESTR) system, which ranks tributaries for treatment with lampricide based partially on the total amount of preferred ammocoete habitat. GIS-based estimates of the total amount of preferred ammocoete habitat may complement current field-based estimates, or provide a basis for nested sampling designs.

Effects of Improved Water Quality and Stream Treatment Rotation on Sea Lamprey Abundance: Implications for Lake Trout Rehabilitation in the Great Lakes

Efforts over the past 25 years to improve water quality in the Great Lakes basin may be counteracting progress toward lake trout rehabilitation that has been made possible by sea lamprey control. Improved water quality in streams has been linked to increased amounts of suitable sea lamprey spawning and ammocoete habitat leading to increased sea lamprey production. To assess the impact of improved water quality on sea lamprey production, we simulated transformer (young adult stage) production in a model stream assuming 50%, 75%, and 100% habitat availability. We also assessed the effect of lengthening the lampricide treatment cycle in streams; a proposed solution to inadequate funding of the sea lamprey control program. Increasing habitat availability dramatically increased the number of transformers produced in the stream; for example, doubling the available sea lamprey habitat resulted in a 2.5 fold increase in sea lamprey production. In addition, we found that the combined effects of improved water quality and lengthened lampricide treatment rotation caused transformer production to increase at a faster rate than either factor acting alone. Increased sea lamprey production directly impacts lake trout mortality and retards efforts toward achievement of lake trout rehabilitation goals. To counteract the improvement of sea lamprey habitat in tributaries, sea lamprey control efforts must be increased in order to enable lake trout rehabilitation to succeed.