Comparing methods for estimating larval sea lamprey (Petromyzon marinus) density in the St. Marys River for the purposes of control

The St. Marys River is a major producer of parasitic sea lampreys (Petromyzon marinus) to Lake Huron making it an important area for larval control. Bayluscide treatments are conducted in areas of high larval density requiring density estimation at fine spatial scales to inform treatment decisions. We evaluated six methods of estimating spatially specific density including the currently used sampling-based estimates, a generalized linear model (GLM) based on mean larval density per plot, a GLM based on larval density per sample, a generalized additive model based on mean larval density per plot, a spatial age-structured population model, and a hybrid approach, which averaged the best performing sampling- and model-based methods. Methods were evaluated based on accuracy in matching independent validation data. Specifically, the methods were evaluated based on their ability to project plot-level larval density, identify high density plots for treatment, and rank plots in order based on density resulting in high numbers of sea lampreys killed per hectare treated. Performance was variable, and no single method outperformed the others for all metrics. Although the sampling-based estimation method and the GLM based on catch data performed adequately for estimating density and identifying high density plots, the hybrid approach was identified as the best method to inform sea lamprey control decisions in the St. Marys River due to its consistent performance. Incorporating model-based approaches should lead to a more efficient and effective treatment program in the St. Marys River and aid in making decisions about the allocation of control resources.     

Effectiveness of Using Backpack Electrofishing Gear for Collecting Sea Lamprey (Petromyzon marinus) Larvae in Great Lakes Tributaries

The effects of water depth, larval density, stream conductance, temperature, lamprey length, and larval escapement were examined to determine the efficiency of sampling sea lamprey (Petromyzon marinus) larvae using direct current (DC) backpack electrofishing gear. A higher proportion of larvae of all sizes were collected per unit sampling effort when sample sites were shallower, contained fewer larvae, or were in streams of lower specific conductance (P < 0.001). Temperature did not affect the efficiency of sampling lamprey larvae in this study. The investigation of the effect of larval escapement on observed catch was inconclusive. Similar length distributions were found between lamprey larvae collected using electrofishing gear and those collected using either a suction dredge or collected during a lampricide treatment. These results have implications for the development of a sampling protocol that uses a single-pass electrofishing technique to estimate the overall abundance of sea lamprey larvae in a stream. This estimate is critical to determining the number of larvae with the potential to metamorphose as parasitic lamprey the following year, and consequently, the prioritization of streams for lampricide treatment.     

An Examination of the Plasticity of Gonad Development in Sea Lampreys,Petromyzon marinus: Observations through Gonadal Biopsies

Observations of larvae with atypical gonads led to this study to determine the extent of the plasticity of gonad development in larval, metamorphosing, and juvenile sea lampreys. Larval and early metamorphosing, sea lampreys underwent microsurgery to remove a biopsy of gonadal tissue. These biopsies were examined quantitatively and were categorized as ovaries, presumptive testes, or as atypical gonads. After a period of approximately 8 to 10 months, the larvae and subsequent juveniles were killed and the gonads were re-examined, again quantitatively, for any changes in gonad development. There was no significant change in the number of larvae with typical ovaries as a direct result of sex reversals and oocyte atresia. None of the metamorphosing lampreys initially biopsied had atypical gonads and no sex reversals were observed in this group. Oocyte number in typical ovaries of the larvae and metamorphosing lampreys did not change over the course of the study; however germ cell number increased significantly in typical testes of both larvae and metamorphosing lampreys. The results of the study confirm that the lability of sex in larval sea lampreys is much greater than previously thought; however, it is clear that sex is defined and does not appear to change once the lampreys have entered the juvenile period.     

The Sea Lamprey in Lake Erie: a Case History

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 Erie's sea lamprey numbers have rebounded, and marking rates on lake trout have approached pre-control levels. It is hypothesized that Lake Erie's 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 behavioural response of migratory sea lamprey (Petromyzon marinus) to potential damage-released larval and migratory chemical alarm cues

We investigated the presence of damage-released alarm cues and the reactions they may cause in landlocked migratory sea lamprey (Petromyzon marinus) using semi-natural laboratory conditions during the day. In two separate experiments, migratory sea lampreys were exposed to stimuli prepared from the skinless carcasses and skin tissue of larval sea lamprey and from the skin tissue and muscle tissue of migratory sea lamprey. Migratory female sea lamprey swam significantly longer after being exposed to the stimulus prepared from the skinless carcass of larval sea lamprey. No significant changes were seen in the behaviour of the migratory female lamprey in response to larval skin extract or in the behaviour of male sea lamprey to any experimental extract in the larval extract experiment. In the second experiment that utilised migratory lamprey stimuli, neither male and nor female migratory sea lamprey showed a significant difference in their behavioural response among different treatments and controls. Our findings indicate that adult female sea lamprey respond strongly to damage-released alarm cues from larval sea lamprey; hence, the latter holds promise for sea lamprey behavioural manipulations for control purposes during the day. Further research is needed to examine responses to damage-released alarm cues at night, when migratory sea lampreys are more active.     

Warmer waters increase the larval sea lamprey's (Petromyzon marinus) tolerance to the lampricide 3-trifluoromethyl-4-nitrophenol (TFM)

Invasive sea lampreys (Petromyzon marinus) in the Great Lakes are controlled by applying the pesticide (lampricide) 3-trifluoromethyl-4-nitrophenol (TFM) to waters infested with larval lamprey. However, treatment effectiveness can be undermined by “residual” larval sea lamprey that survive TFM exposure, and subsequently complete metamorphosis into parasitic juvenile sea lamprey that prey on culturally and economically important fishes. We investigated how season and temperature influenced the TFM tolerance of larval sea lamprey. Acute toxicity tests on lamprey collected from the Au Sable River, Michigan, revealed that the 12-h LC₅₀ and LC_99.9 were 2.0- to 2.5-fold greater in late spring and summer, than in early spring and fall. Subsequent toxicity tests indicated that greater TFM tolerance in summer was due to warmer temperatures, based on an almost 2-fold greater 12-h LC₅₀ and LC_99.9 in warm (24 °C) compared to cool (6 °C) water. Variations in energy stores (glycogen, lipid, protein) or condition did not appear to affect TFM sensitivity. We conclude that higher water temperature is the primary factor driving the larval sea lamprey's greater tolerance to TFM during the summer, possibly due to an increase in their capacity to detoxify TFM. Considering seasonal variations in temperature may be prudent when selecting and treating sea lamprey infested streams with TFM to minimize treatment residuals. In the longer term, increases in average and peak water temperatures due to climate change could result in greater TFM requirements and costs due to the greater tolerance of larval sea lamprey to TFM at warmer temperatures.     

Optimizing a Standardized Electrofishing Sampling Protocol for Warmwater Resident Sportfish in the Tallapoosa River,Alabama, USA

A two‐year electrofishing study was initiated in the Tallapoosa River, Alabama, to identify an optimal standardized sampling program for three principal resident sportfish: Alabama bass Micropterus henshalli, redbreast sunfish Lepomis auritus, and redeye bass Micropterus coosae. Samples were conducted in spring (May), summer (July), and fall (October) in 2010 and 2011 from seven 1‐h transects. Spring samples of Alabama bass had lower catch per effort (CPE) and were more skewed towards fish between 200 and 300 mm total length (TL) than samples in other seasons; whereas, fall samples collected more redeye bass >200 mm TL but CPE was similar among seasons. Fewer, but larger, redbreast sunfish were sampled during fall compared with other seasons. Mean CPE of all three species was independent of transect duration. The total time spent electrofishing and processing fish in order to estimate a mean CPE with a specified precision was a function of transect duration and CPE. More effort was needed as CPE decreased for most species, but the relations between transect duration and total effort were parabolic. A precision of within 10% of the mean CPE was unattainable for most species as a result of logistic considerations. Based on the results of this study, it appears that fall is the optimal sampling time for these species in the Tallapoosa River and the optimal transect duration is likely 10 min. At a precision level of 20% of the mean, the number of 10‐min transects required ranged from 5 to 40, with a total sample time for each individual species of 0.82–7.16 h. Copyright © 2014 John Wiley & Sons, Ltd.     

Optimizing sampling strategies for estimating mean water quality in lakes using geostatistical techniques with remote sensing

In planning a sampling regime, it is desirable that the sampling procedure should involve minimum estimation error for a given sample size or minimum sampling effort for a given accuracy. Two approaches for matching sampling effort to accuracy may be used: a classical approach, which ignores spatial dependence between observations, and uses a random scheme; and a geostatistical approach, which exploits spatial dependence, and uses a systematic scheme. Four Airborne Thematic Mapper images of two British lakes were processed to provide a chlorophyll index, reflecting variations in chlorophyll‐a concentration. Spatial structure was characterized using the variogram, and the modelled variogram was used in Kriging to plan sampling regimes for estimating the mean chlorophyll. For a given sample size, the systematic scheme incurred less error than the random scheme; and for a given error, the systematic scheme required smaller sample sizes than the random scheme. The relative advantage of the systematic approach over the random sampling approach increased with an increase in sample size and an increase in the proportion of variance in the data that was spatially dependent. This paper demonstrates that the sampling regime must be calibrated to the spatial dynamics of the lake under investigation, and suggests that remote sensing is the ideal means by which to determine such dynamics.     

Response of Larval Sea Lampreys (Petromyzon marinus) to Pulsed DC Electrical Stimuli in Laboratory Experiments

Four electrical factors that are used in pulsed DC electrofishing for larval sea lampreys (Petromyzon marinus) were evaluated in two laboratory studies to determine the optimal values to induce larval emergence over a range of water temperatures and conductivities. Burrowed larvae were exposed to combinations of pulsed DC electrical factors including five pulse frequencies, three pulse patterns, and two levels of duty cycle over a range of seven voltage gradients in two separate studies conducted at water temperatures of 10, 15, and 20°C and water conductivities of 25, 200, and 900 μS/cm. A four-way analysis of variance was used to determine significant (α = 0.05) influences of each electrical factor on larval emergence. Multiple comparison tests with Bonferroni adjustments were used to determine which values of each factor resulted in significantly higher emergence at each temperature and conductivity. Voltage gradient and pulse frequency significantly affected emergence according to the ANOVA model at each temperature and conductivity tested. Duty cycle and pulse pattern generally did not significantly influence the model. Findings suggest that a setting of 2.0 V/cm, 3 pulses/sec, 10% duty, and 2:2 pulse pattern seems the most promising in waters of medium conductivity and across a variety of temperatures. This information provides a basis for understanding larval response to pulsed DC electrofishing gear factors and identifies electrofisher settings that show promise to increase the efficiency of the gear during assessments for burrowed sea lamprey larvae.     

100 years of sea lampreys above Niagara Falls: A reflection on what happened and what we learned

In the one hundred years since sea lampreys (Petromyzon marinus) were discovered in Lake Erie, the species completed its invasion throughout the Great Lakes basin, contributed to the downfall of the commercial fishing industry, and served as a catalyst for the development of the collaborative fishery management regime that exists today. The sea lamprey invasion simultaneously caused wide-spread devastation while giving rise to a collective realization that the health of the Great Lakes would require ongoing cooperation among governments, scientists, and users of the resource. Since its inception, the effort to control sea lampreys in the Great Lakes has been defined by a “shoot for the moon” mentality. The desperation of communities directly harmed by the sea lamprey invasion, coupled with the determination and unyielding commitment to science by those tasked with addressing the problem, led to the formation of the only reported successful aquatic vertebrate invasive species control program at an ecosystem scale.     

Performance of a Vertical‐Slot Fish Pass for the Sea Lamprey Petromyzon marinus L. and Habitat Recolonization

In 2011, a vertical‐slot fish pass was built at the Coimbra Açude‐Ponte dam (Mondego River, Portugal), approximately 45 km upstream from the river mouth. The performance of this infrastructure for sea lamprey passage was evaluated between 2011 and 2015 using several complementary methodologies, namely radio telemetry [conventional and electromyogram (EMG)], passive integrated transponder (PIT) telemetry and electrofishing surveys. During the study period, the electrofishing revealed a 29‐fold increase in the abundance of larval sea lamprey upstream of the fish pass. Of the 20 radio‐tagged individuals released downstream from the dam, 33% managed to find and successfully surpass the obstacle in less than 2 weeks, reaching the spawning areas located in the upstream stretch of the main river and in one important tributary. Fish pass efficiency was assessed with a PIT antenna installed in the last upstream pool and revealed a 31% efficiency, with differences between and within migratory seasons. Time of day and river flow significantly influenced the attraction efficiency of the fish pass, with lampreys negotiating it mainly during the night period and when discharge was below 50 m³ s^?1. Sea lampreys tagged with EMG transmitters took 3 h to negotiate the fish pass, during which high muscular effort was only registered during passage, or passage attempts, of the vertical slots. The use of complementary methodologies provided a comprehensive passage evaluation for sea lamprey, a species for which there is a considerable paucity of valuable data concerning behavioural, physiological and environmental influences on obstacle negotiation. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.     

In situ assessment of lampricide toxicity to age-0 lake sturgeon

The lampricides 3-trifluoromethyl-4-nitrophenol (TFM) and 2′, 5-dichloro-4′-nitrosalicylanilide (niclosamide) are used to control sea lamprey (Petromyzon marinus), an invasive species in the Great Lakes. Age-0 lake sturgeon (Acipenser fulvescens), a species of conservation concern, share similar stream habitats with larval sea lampreys and these streams can be targeted for lampricide applications on a 3- to 5-year cycle. Previous laboratory research found that lake sturgeon smaller than 100 mm could be susceptible to lampricide treatments. We conducted stream-side toxicity (bioassay) and in situ studies in conjunction with 10 lampricide applications in nine Great Lakes tributaries to determine whether sea lamprey treatments could result in in situ age-0 lake sturgeon mortality, and developed a logistic model to help predict lake sturgeon survival during future treatments. In the bioassays the observed concentrations where no lake sturgeon mortality occurred (no observable effect concentration, NOEC) were at or greater than the observed sea lamprey minimum lethal concentration (MLC or LC99) in 7 of 10 tests. We found that the mean in situ survival of age-0 lake sturgeon during 10 lampricide applications was 80%, with a range of 45–100% survival within streams. Modeling indicated that in age-0 lake sturgeon survival was negatively correlated with absolute TFM concentration and stream alkalinity, and positively correlated with stream pH and temperature. Overall survival was higher than expected based on previous research, and we expect that these data will help managers with decisions on the trade-offs between sea lamprey control and the effect on stream-specific populations of age-0 lake sturgeon.     

Survival and metamorphosis of low-density populations of larval sea lampreys (Petromyzon marinus) in streams following lampricide treatment

Sea lamprey Petromyzon marinus control in the Great Lakes primarily involves application of lampricides to streams where larval production occurs to kill larvae prior to their metamorphosing and entering the lakes as parasites (juveniles). Because lampricides are not 100% effective, larvae that survive treatment may metamorphose before streams are again treated. Larvae that survive treatment have not been widely studied, so their dynamics are not well understood. We tagged and released larvae in six Great Lake tributaries following lampricide treatment and estimated vital demographic rates using multistate tag-recovery models. Model-averaged larval survivals ranged from 56.8 to 57.6%. Model-averaged adult recovery rates, which were the product of juvenile survivals and adult capture probabilities, ranged from 6.8 to 9.3%. Using stochastic simulations, we estimated production of juvenile sea lampreys from a hypothetical population of treatment survivors under different growth conditions based on parameter estimates from this research. For fast-growing populations, juvenile production peaked 2 years after treatment. For slow-growing populations, juvenile production was approximately one-third that of fast-growing populations, with production not peaking until 4 years after treatment. Our results suggest that dynamics (i.e., survival, metamorphosis) of residual larval populations are very similar to those of untreated larval populations. Consequently, residual populations do not necessarily warrant special consideration for the purpose of sea lamprey control and can be ranked for treatment along with other populations. Consecutive lampricide treatments, which are under evaluation by the sea lamprey control program, would be most effective for reducing juvenile production in large, fast-growing populations.     

POTENTIAL IMPACTS OF SMALL‐SCALE HYDROELECTRIC POWER GENERATION ON DOWNSTREAM MOVING LAMPREYS

Small‐scale hydropower is developing rapidly in many countries in response to policies of encouraging renewable energy and reducing reliance on fossil fuels. This rapid increase in the construction of hydroelectric turbines provides a substantial risk to migrating biota, especially fish. Some turbines, such as the Archimedes screw design, are regarded as relatively friendly to fish but have not yet been assessed for their potential impacts on threatened lamprey species. To assess the risk of impingement and the patterns of movement by emigrating river lamprey Lampetra fluviatilis transformers and drifting larval ammocoetes at the site of an Archimedes screw turbine in north‐east England, drift nets were set over the periods of January to June 2009 and November 2009 to May 2010. Drifting Lampetra sp. larvae were recorded in all sampling months, November to June, while emigrating lampreys were recorded in all months but June (93% captured between December and April), reflecting a higher period of impingement risk than expected. Night‐time catches were 24‐ and 8‐fold higher for transformers and larvae, respectively, than daytime catches. Catch per unit water volume data in different channel areas suggest that lamprey larvae behaved as passive particles within the river flow but that transformers selected areas of higher flow. Damage rates of lampreys passed through the screw were low (1.5%), suggesting minor impacts on downstream‐moving larval and juvenile lampreys. However, the cumulative potential impacts of multiple hydropower sites on downstream fish passage, including lampreys, should be considered by regulatory agencies when planning hydropower development within catchments. Copyright © 2012 John Wiley & Sons, Ltd.     

Seasonal Patterns in Growth,Blood Consumption,and Effects on Hosts by Parasitic-Phase Sea Lampreys in the Great Lakes: An Individual-Based Model Approach

An individual-based model (IBM) was developed for sea lamprey (Petromyzon marinus) populations in the Laurentian Great Lakes. The IBM was then calibrated to observed growth, by season, for sea lampreys in northern Lake Huron under two different water temperature regimes: a regime experienced by Seneca-strain lake trout (Salvelinus namaycush) and a regime experienced by Marquettestrain lake trout. Modeling results indicated that seasonal blood consumption under the Seneca regime was very similar to that under the Marquette regime. Simulated mortality of lake trout directly due to blood removal by sea lampreys occurred at nearly twice the rate during August and September under the Marquette regime than under the Seneca regime. However, cumulative sea lamprey-induced mortality on lake trout over the entire duration of the sea lamprey's parasitic phase was only 7% higher for the Marquette regime compared with the Seneca regime. Thus, these modeling results indicated that the strain composition of the host (lake trout) population was not important in determining total number of lake trout deaths or total blood consumption attributable to the sea lamprey population, given the sea lamprey growth pattern. Regardless of water temperature regime, both blood consumption rate by sea lampreys and rate of sea lamprey-induced mortality on lake trout peaked in late October. Elevated blood consumption in late October appeared to be unrelated to changes in water temperature. The IBM approach should prove useful in optimizing control of sea lampreys in the Laurentian Great Lakes.     

Assessing Assessment: Can the Expected Effects of the St. Marys River Sea Lamprey Control Strategy Be Detected?

In 1997 the Great Lakes Fishery Commission approved a 5-year (1998 to 2002) control strategy to reduce sea lamprey (Petromyzon marinus) production in the St. Marys River, the primary source of parasitic sea lampreys in northern Lake Huron. An assessment plan was developed to measure the success of the control strategy and decide on subsequent control efforts. The expected effects of the St. Marys River control strategy are described, the assessments in place to measure these effects are outlined, and the ability of these assessments to detect the expected effects are quantified. Several expected changes were predicted to be detectable: abundance of parasitic-phase sea lampreys and annual mortality of lake trout (Salvelinus namaycush) by 2001, abundance of spawning-phase sea lampreys by 2002, and relative return rates of lake trout and sea lamprey wounding rates on lake trout by 2005. Designing an effective assessment program to quantify the consequences of fishery management actions is a critical, but often overlooked ingredient of sound fisheries management.     

Variation in larval sea lamprey demographics among Great Lakes tributaries: A mixed-effects model analysis of historical survey data

Understanding variation in fish populations is valuable from both a management and an ecological perspective. Great Lakes sea lampreys are controlled primarily by treating tributaries with lampricides that target the larval stage. Great Lakes streams were divided into four categories based on their regularity of parasitic lamprey production inferred from the historic regularity of chemical treatments. This categorization was intended to direct future assessment efforts, but may also reflect differences in early demographics. We analyzed assessment data collected from 1959 to 2005 using mixed-effects models and variance components analyses to test for differences in recruitment and growth to age 1 among stream categories. Recruitment was twice as large in regularly treated streams as in irregularly treated streams, indicating that age-1 year-class strength is correlated with consistent chemical treatments. We found no differences in length at age 1 among stream categories; however, Lake Superior streams with irregular treatment histories exhibit more variation in length at age 1 than streams that are treated regularly. The majority of variation in length at age 1 was due to within-year variation, which was fairly consistent across stream types within each lake. Our results indicate that early life history differs among subsets of the Great Lakes sea lamprey population, and management practices should be modified to account for these differences. Mixed-effects models and variance components analyses are useful tools for analyzing large historical datasets for patterns of demographic variation within and among populations, whether the ultimate goal is pest control, harvesting, or conservation.     

Development and Evaluation of a New Predictive Model for Metamorphosis of Great Lakes Larval Sea Lamprey (Petromyzon marinus) Populations

Accurate forecasts of the number of larval sea lamprey (Petromyzon marinus) within a stream that will enter into metamorphosis are critical to currently used methods for allocating lampricide treatments among streams in the Great Lakes basin. To improve our ability to predict metamorphosis we used a mark-recapture technique, involving the marking of individual larval lamprey with sequentially coded wire tags, to combine information regarding individual and stream level parameters collected in year t, with direct observations of metamorphic outcome of lamprey recaptured in year t+1. We used these data to fit predictive models of metamorphosis. The best model demonstrated excellent predictive capabilities and highlighted the importance of weight, age, larval density, stream temperature and geographic location in determining when individual lamprey are likely to transform. While this model was informative, it required data whose measures are not practical to obtain routinely during the larval sea lamprey assessment program. A second model, limited to data inputs that can be easily obtained, was developed and included length of larvae the fall prior to metamorphosis, stream latitude and longitude, drainage area, average larval density in type-2 habitat, and stream lamprey production category (a measure of the regularity with which treatments are required). This model accurately predicted metamorphosis 20% more often than current models of metamorphosis; however, we recommend further validation on an independent set of streams before adoption by the Great Lakes Fishery Commission for ranking streams.     

Community Structure of Age‐0 Fishes in Paired Mainstem and Created Shallow‐water Habitats in the Lower Missouri River

Anthropogenic alterations to aquatic ecosystems have greatly reduced and homogenized riverine habitat, especially those used by larval and juvenile fishes. Creation of shallow‐water habitats is used as a restoration technique in response to altered conditions in several studies globally, but only recently in the USA. In the summer of 2012, the U.S. Army Corps of Engineers sampled larval and juvenile fishes at six paired sites (mainstem and constructed chute shallow‐water habitats) along a section of the Missouri River between Rulo, NE and St. Louis, MO, USA. From those samples, we enumerated and identified a total of 7622 fishes representing 12 families. Community responses of fishes to created shallow‐water habitats were assessed by comparisons of species richness and diversity measures between paired sites and among sampling events. Shannon entropy measures were transformed, and gamma diversity (total diversity) was partitioned into two components, alpha (within community) and beta (between community) diversity using a multiplicative decomposition method. Mantel test results suggest site location, time of sampling event and habitat type were drivers of larval and juvenile community structure. Paired t‐test results indicated little to no differences in beta diversity between habitat types; however, chute habitats had significantly higher alpha and gamma diversity as well as increased abundances of Asian carp larvae when compared with mainstem shallow‐water habitat. Our results not only show the importance of created shallow‐water habitat in promoting stream fish diversity but also highlight the role space and time may play in future restoration and management efforts. Copyright © 2015 John Wiley & Sons, Ltd.     

Evaluating Sampling Strategies for Larval Cisco (Coregonus artedi)

To improve our ability to assess larval cisco (Coregonus artedi) populations in Lake Superior, we conducted a study to compare several sampling strategies. First, we compared density estimates of larval cisco concurrently captured in surface waters with a 2 × 1-m paired neuston net and a 0.5-m (diameter) conical net. Density estimates obtained from the two gear types were not significantly different, suggesting that the conical net is a reasonable alternative to the more cumbersome and costly neuston net. Next, we assessed the effect of tow pattern (sinusoidal versus straight tows) to examine if propeller wash affected larval density. We found no effect of propeller wash on the catchability of larval cisco. Given the availability of global positioning systems, we recommend sampling larval cisco using straight tows to simplify protocols and facilitate straightforward measurements of volume filtered. Finally, we investigated potential trends in larval cisco density estimates by sampling four time periods during the light period of a day at individual sites. Our results indicate no significant trends in larval density estimates during the day. We conclude estimates of larval cisco density across space are not confounded by time at a daily timescale. Well-designed, cost effective surveys of larval cisco abundance will help to further our understanding of this important Great Lakes forage species.