Trent M. Sutton

Overwinter Survival of Juvenile Lake Herring in Relation to Body Size, Physiological Condition, Energy Stores, and Food Ration

Abstract Populations of lake herring Coregonus artedi in Lake Superior have exhibited high recruitment variability over the past three decades. To improve our understanding of the mechanisms which influence year-class strength, we conducted a 225-d laboratory experiment to evaluate the effects of body size, physiological condition, energy stores, and food ration on the winter survival of age-0 lake herring. Small (total length (TL) range = 60–85 mm) and large (TL range = 86–110 mm) fish were maintained under thermal and photoperiod regimes that mimicked those in Lake Superior from October through May. Fish in each size-class were maintained at two feeding treatments: brine shrimp Artemia spp. ad libitum and no food. The mortality of large lake herring (fed, 3.8%; starved, 20.1%) was significantly less than that of small fish (fed, 11.7%; starved, 32.0%). Body condition and crude lipid content declined for all fish over the experiment; however, these variables were significantly greater for large fed (0.68...

Early Life Stage Mortality Rates of Lake Sturgeon in the Peshtigo River, Wisconsin

Abstract A thorough understanding of the early life history of lake sturgeon Acipenser fulvescens is critical for rehabilitation of this species. Recruitment of lake sturgeon is known to be variable, but the extent of that variation and mortality rates experienced by early life stages are unclear. The objective of this study was to quantify early life stage mortality and explore the variability in year-class strength by estimating total egg deposition and abundance of larval and age-0 juvenile lake sturgeon from the 2006 and 2007 year-classes in the Peshtigo River, Wisconsin. Egg mats, drift nets, and visual surveys were used to collect lake sturgeon eggs, larvae, and age-0 juveniles, respectively. Total egg deposition, larval abundance, and age-0 juvenile abundance were higher in 2007 than in 2006. The magnitude of difference ranged from 2 times for eggs to 11 times for age-0 juveniles. The rate of mortality from the larval stage to the age-0 juvenile stage was higher in 2006 (98.26%) than in 2007 (90.46...

Seasonal Movement Patterns, Habitat Use, and Home Range of Flathead Catfish in the Lower St. Joseph River, Michigan

Abstract Few studies have examined the seasonal movement patterns, habitat use, and home range of flathead catfish Pylodictis olivaris in lotic systems throughout the northern United States. We used ultrasonic telemetry on 39 flathead catfish (range, 430–1,132 mm total length) in the lower St. Joseph River, Michigan, to increase our understanding of these behaviors in northern populations of flathead catfish and to provide important information for the development of appropriate management strategies in this system. Transmitters were surgically implanted into the peritoneal cavity of selected individuals captured by means of low-voltage AC electrofishing during 2002 and 2003. Habitat use of flathead catfish was dominated by large woody debris and riprap at water depths less than 3 m during all seasons except winter, when fish utilized main-channel pool habitats associated with coarse substrates at water depths greater than 4 m. Flow rates at fish locations were not significantly different among seasons (r...

Community-level disruptions among zooplankton of pond mesocosms treated with a neem (azadirachtin) insecticide

A natural, plant-derived insecticide, neem, is being evaluated as an alternative insect pest control product for forestry in Canada. As part of the process to investigate the environmental safety of neem-based insecticides, a mesocosm experiment was conducted to assess the effects of neem on natural zooplankton communities. Replicate (n=5), shallow (<1 m) forest pond enclosures were treated with Neemix 4.5, at concentrations of 0.035 (the expected environmental concentration), 0.18, 0.70, and 1.75 mg/l active ingredient, azadirachtin. Zooplankton communities were quantitatively sampled over a 4-month experimental period in treated and control enclosures, and water samples were collected to track azadirachtin concentrations. Concentrations in water declined linearly with estimated DT(50) values of 25-29 days. Trends in abundance over time among populations of cladocerans, copepods, and rotifers were found to differ significantly among treatments. At the two highest test concentrations, adverse effects were obvious with significant reductions in several cladoceran species, and near elimination of the three major copepod species present. More subtle effects at the two lowest test concentrations were determined by comparing the community structure of enclosures across treatment levels and over time through an analytical process based on the multivariate statistical software, PRIMER. Significant effects on community structure were detected at both of these lower concentrations, including the expected environmental concentration of 0.035 mg/l azadirachtin. Differential responses among species (some increases, some decreases) caused detectable disruptions in community structure among zooplankton of treated enclosures. Perturbations to zooplankton communities were sufficient to cause measurable differences in system-level metabolism (midday dissolved oxygen concentrations) at all but the lowest test concentration.

Genetic structure of lake whitefish (Coregonus clupeaformis) in Lake Michigan

Genetic relationships among lake whitefish (Coregonus clupeaformis) spawning aggregates in Lake Michigan were assessed and used to predict a stock or management unit (MU) model for the resource. We hypothesized that distinct spawning aggregates represented potential MUs and that differences at molecular markers underlie population differentiation. Genetic stock identification using 11 microsatellite loci indicated the presence of six genetic MUs. Resolved MUs corresponded to geographically proximate spawning aggregates clustering into genetic groups. Within MUs, analyses suggested that all but one delineated MU was a stable grouping (i.e., no between-population differences), with the exception being the Hog Island – Traverse Bay grouping. Elk Rapids was the most genetically divergent population within Lake Michigan. However, low Fst values suggested that moderate to high levels of gene flow occur or have occurred in the past between MUs. Significant tests of isolation by distance and low pairwise Fst valu...

Predation on Early Life Stages of Lake Sturgeon in the Peshtigo River, Wisconsin

Abstract Mortality of early life stages can limit recruitment of fishes, and understanding the impacts of various sources of mortality has long been a goal of fisheries management. The impacts of predation on lake sturgeon Acipenser fulvescens are not well understood. The objective of this study was to identify and quantify sources of predation that affect lake sturgeon eggs, larvae, and age-0 juveniles in the Peshtigo River, Wisconsin, during 2006 and 2007. Egg bags were used to assess the rate of lake sturgeon egg consumption by crayfishes Orconectes spp. Potential piscine predators on eggs, larvae, or age-0 juveniles were captured using fyke nets, gill nets, hoop nets, and electrofishing for analysis of stomach contents. Crayfish consumed lake sturgeon eggs at an average rate of 9.4 eggs/d, and the population of crayfish within the lake sturgeon spawning habitat consumed an estimated 300,000 eggs during the incubation period. Numerous fish species were observed consuming lake sturgeon eggs, and piscine...

An Evaluation of Age Estimation Structures for Lake Whitefish in Lake Michigan: Selecting an Aging Method Based on Precision and a Decision Analysis

Abstract Declines in growth and condition of lake whitefish Coregonus clupeaformis in Lakes Huron and Michigan have led to increased mean age in the harvest and greater difficulty in scale age interpretation. We evaluated the precision and efficiency of scale acetate impressions, transverse pectoral fin ray sections, and transverse sagittal otolith sections for three lake whitefish stocks (Baileys Harbor, Naubinway, and Saugatuck) that were sampled in Lake Michigan during 2004 and 2005. We conducted a decision matrix analysis that incorporated capital, production, and personnel costs and precision of age estimates to determine the best aging method given current management priorities. For the Baileys Harbor stock, age estimates were systematically lower based on scales (mean = 7.85 years) than based on fin rays (8.44 years) or otoliths (8.78 years); fin ray and otolith estimates did not differ significantly. Similar results were observed for both Naubinway and Saugatuck stocks. For Baileys Harbor lake ...

Population Characteristics of Shovelnose Sturgeon in the Upper Wabash River, Indiana

Abstract Shovelnose sturgeon Scaphirhynchus platorynchus support a commercial fishery throughout much of the Mississippi and Missouri River drainages. There is concern that harvest closures for Eurasian sturgeons (Acipenseridae) may result in increased exploitation of shovelnose sturgeon to meet global demands for caviar. Population attributes of shovelnose sturgeon were examined in the upper Wabash River, Indiana, from April 2003 through November 2004 between Wabash and Terre Haute. Fish (N = 4,849) were captured by direct current electrofishing, experimental gill nets, and benthic trawls. Electrofishing catch per unit effort varied on a temporal basis, being highest for both reaches from March through May. The fork length of captured fish ranged from 273 to 858 mm, but few fish less than 550 mm were captured. Median fork length and wet weight were 683 mm and 1,208 g, respectively (ranges = 273–858 mm and 52–3,381 g). Shovelnose sturgeon ranged from ages 2 to 30, with 95% of the fish between ages 9 and 2...

Influence of External Transmitter Shape and Size on Tag Retention and Growth of Juvenile Lake Sturgeon

Abstract Few studies have examined the effects of external radio transmitters on small fish. We evaluated the influence of two shapes (cylindrical and compressed) and three sizes (small, medium, and large [approximately 1.25, 2.00, and 6.00% of body weight, respectively]) of dummy transmitters on the tag retention and growth of juvenile lake sturgeon Acipenser fulvescens in an 8-week laboratory experiment. Thirty-five lake sturgeon were contained in each of three tanks, with five fish in each tank assigned to each of the six transmitter treatments. The remaining five fish in each tank, which served as the control group, were handled but did not receive a transmitter. A greater number of compressed transmitters were shed than cylindrical transmitters, and more large transmitters were lost than small or medium transmitters. Fish with medium and large transmitters, regardless of shape, exhibited lower growth than fish with small transmitters or the control group from week 2 through the end of the study. Only...

Hatchery Performance Attributes of Juvenile Lake Sturgeon Fed Two Natural Food Types

Abstract The use of stocking programs to rehabilitate depressed populations of lake sturgeon Acipenser fulvescens requires the optimization of early life stage growth in hatchery settings. We evaluated the performance of juvenile lake sturgeon fed different proportions of two natural food types—adult brine shrimp Artemia spp. and larval bloodworms Chironomus spp.—over a 10-week laboratory experiment. The following five diet treatments were provided: (1) 100% bloodworms; (2) 75% bloodworms : 25% brine shrimp; (3) 50% bloodworms : 50% brine shrimp; (4) 25% bloodworms : 75% brine shrimp; and (5) 100% brine shrimp. Lake sturgeon growth was positively related to bloodworm content in the diet and was significantly different among treatments. Although the initial sizes of fish were similar, mean fork length and wet weight were greatest for the 100% bloodworm treatment (183.1 mm and 37.5 g, respectively) and lowest for the 100% brine shrimp diet (118.4 mm and 9.5 g) by the end of the study. Mean specific and abso...