Daniel B. Hayes

Accounting for Multilevel Data Structures in Fisheries Data using Mixed Models

Multilevel data structures are those that have a hierarchical structure, in which response variables are measured at the lowest level of the hierarchy and modeled as a function of predictor variables measured at that level and higher levels of the hierarchy. For example, a multilevel data structure may consist of measurements taken on individual fish (lower level) that are nested within lakes or streams (higher level). Multilevel data structures are a common feature in fisheries research. We provide simulated fisheries data examples, similar in structure to other published studies, to illustrate the application of multilevel models and discuss how hypothesis testing and inferences can be incorrect if multilevel data structures are ignored. Ignoring multilevel data structures has implications for the use of commonly-used ordinary least squares (OLS) approaches to test hypotheses and to make inferences. Multilevel models are an alternate approach that circumvents problems associated with traditional OLS methods and allows valid inferences to be made.

Spatial Patterns Emphasize the Importance of Coastal Zones as Nursery Areas for Larval Walleye in Western Lake Erie

Abstract Lake Erie walleye Sander vitreus exhibits significant interannual variability in year-class strength. Recent research revealed the importance of larval growth and survival rates in determining walleye year-class strength in western Lake Erie, indicating that spatial and temporal overlap of larvae with good habitat conditions (e.g., abundant prey, warm waters) promoted walleye growth and survival. To assess the spatial overlap between walleye larvae and habitat parameters (water depth, temperature, water clarity, prey density) in western Lake Erie, we evaluated the spatial distribution of walleye larvae and these habitat parameters with intensive sampling at 30 to 36 sites during spring 1994–1999. We analyzed spatial relationships among pelagic walleye larvae and various habitat attributes using a geographic information system and principal components analysis. Larval walleye density was consistently highest at nearshore sites during all years and showed a high degree of spatial overlap with high ichthyoplankton density, and warm water temperatures. Larval walleye density was negatively associated with water depth and water clarity. Two principal components represented 79.6% of the total variability in site attributes. Principle components analysis supported our spatial analysis by graphically separating sites into distinct groups based on larval walleye density and habitat attributes. These analyses indicated that similar relationships between larval distribution and habitat attributes occur each year, emphasizing the importance of nearshore coastal zones as nursery areas for walleye.

Low-head Sea Lamprey Barrier Effects on Stream Habitat and Fish Communities in the Great Lakes Basin

Abstract Low-head barriers are used to block adult sea lamprey ( Petromyzon marinus ) from upstream spawning habitat. However, these barriers may impact stream fish communities through restriction of fish movement and habitat alteration. During the summer of 1996, the fish community and habitat conditions in twenty-four stream pairs were sampled across the Great Lakes basin. Seven of these stream pairs were re-sampled in 1997. Each pair consisted of a barrier stream with a low-head barrier and a reference stream without a low-head barrier. On average, barrier streams were significantly deeper (df = 179, P = 0.0018) and wider (df = 179, P = 0.0236) than reference streams, but temperature and substrate were similar (df = 183, P = 0.9027; df = 179, P = 0.999). Barrier streams contained approximately four more fish species on average than reference streams. However, streams with lowhead barriers showed a greater upstream decline in species richness compared to reference streams with a net loss of 2.4 species. Barrier streams also showed a peak in richness directly downstream of the barriers, indicating that these barriers block fish movement upstream. Using Sorensons similarity index (based on presence/absence), a comparison of fish community assemblages above and below low-head barriers was not significantly different than upstream and downstream sites on reference streams (n = 96, P > 0.05), implying they have relatively little effect on overall fish assemblage composition. Differences in the frequency of occurrence and abundance between barrier and reference streams was apparent for some species, suggesting their sensitivity to barriers.

Response of Yellow Perch and the Benthic Invertebrate Community to a Reduction in the Abundance of White Suckers

Abstract Competitive interactions between white suckers Catostomus commersoni and yellow perch Perca flavescens were evaluated in a whole-lake manipulation experiment with one treatment lake and one reference lake. After a 2-year pretreatment period, 80% of the adult white sucker population was removed from Douglas Lake, Michigan, with trap nets set during the spring spawning season of 1987. Following white sucker removal, the abundance of chironomid larvae and the mayfly Caenis sp. increased 13–18-fold in Douglas Lake, In Little Bear Lake, the control lake, Caenis sp. showed a 20% decline in abundance during the study period (1985–1989), and chironomid larvae showed a 2.2-fold increase over the same time period. Associated with the increase in benthic invertebrate abundance in Douglas Lake, the diet of adult (>age-0) yellow perch shifted from predominantly zooplankton to predominantly benthos. This shift was accompanied by an increase in mean stomach content weight and feeding rate, eventually becoming a...

Balancing Aquatic Habitat Fragmentation and Control of Invasive Species: Enhancing Selective Fish Passage at Sea Lamprey Control Barriers

Abstract Barriers to prevent spawning migrations of sea lampreys Petromyzon marinus remain an important component of an integrated sea lamprey management program in the Laurentian Great Lakes. Concerns about effects on nontarget fishes have led to the construction of specially designed vertical-slot trap-and-sort fishways to mitigate potential barrier effects. To improve passage at these fishways, we used passive integrated transponder technology to assess the performance of two fishways located on low-head sea lamprey barriers. Fishways on the Big Carp River (which flows into Lake Superior) and Cobourg Brook (which flows into Lake Ontario) were assessed for attraction efficiency, trap attraction and retention, and passage efficiency. Based on the results of these assessments, fishways were modified by increasing the trap volume and altering the funnel characteristics to reduce escapement from the trap and then reassessed. Attraction efficiency for all tagged fish was high (≥80%) at both sites in all year...

The Effects of the Stronach Dam Removal on Fish in the Pine River, Manistee County, Michigan

Abstract Although dam removal has been increasingly used as an option in dam management and as a river restoration tool, there are few studies providing detailed quantitative assessment of the response of fish populations to dam removal. In this study, we document the response of the fish community in the Pine River, Michigan, to the gradual removal of Stronach Dam. Ten sites were sampled annually during the course of the removal (1997–2003) and for 4 years following removal (2004–2007). Before the removal of Stronach Dam, 11 fish species were found only downstream of the dam, 1 species was found only upstream of the dam, and 19 species were captured both above and below the dam. Following removal, 8 species formerly found only below the dam utilized newly available portions of the river above the dam. Most fish species (18 of the 25 evaluated) showed an increase in abundance following removal, strongly supporting the idea that dam removal reduces multiple factors limiting riverine fishes. Brown trout Sal...

Predation on Walleye Eggs by Fish on Reefs in Western Lake Erie

ABSTRACT We examined diets of fishes from gillnet and egg pump collections conducted on reefs in western Lake Erie during walleye (Sander vitreus) egg incubation periods from 1994–1999 and 2004 to assess incidence of walleye eggs in fish diets. We collected no potential egg predators in samples taken in 1994 but from 1995–1999 and in 2004 we caught 22 different species of fish on reefs in addition to spawning walleye. In most years, white perch (Morone americana) stomachs contained more walleye eggs than any other species on the reefs averaging 253 eggs per stomach. We also found lower numbers of walleye eggs in the stomachs of channel catfish (Ictalurus punctatus; 53 eggs/stomach), johnny darter (Etheostoma nigrum; 2 eggs/stomach), logperch (Percina caprodes; 10 eggs/stomach), quillback (Carpiodes cyprinus; 184 eggs/stomach), rock bass (Ambloplites rupestris; 3 eggs/stomach), round goby (Neogobius melanostomus; 4 eggs/stomach), sculpin (Cottidae; 21 eggs/stomach), silver chub (Macrhybopsis storeriana; 3 eggs/stomach), spottail shiner (Notropis hudsonius; 14 eggs/stomach), trout-perch (Percopsis omiscomaycus; 30 eggs/stomach), white sucker (Catastomus commersonii; 20 eggs/stomach), and yellow perch (Perca flavescens; 181 eggs/stomach). Similar to other studies of predation on walleye eggs, our results indicate that prolonged incubation periods increase the potential for egg loss due to predation.

Linking fish population dynamics to habitat conditions: insights from the application of a process-oriented approach to several Great Lakes species

One of the major challenges facing fishery scientists and managers today is determining how fish populations are influenced by habitat conditions. Many approaches have been explored to address this challenge, all of which involve modeling at one level or another. In this paper, we explore a process-oriented model approach whereby the critical population processes of birth and death rates are explicitly linked to habitat conditions. Application of this approach to five species of Great Lakes fishes including: walleye (Sander vitreus), lake trout (Salvelinus namaycush), smallmouth bass (Micropterus dolomieu), yellow perch (Perca flavescens), and rainbow trout (Onchorynchus mykiss), yielded a number of insights into the modeling process. One of the foremost insights is that processes determining movement and transport of fish are critical components of such models since these processes largely determine the habitats fish occupy. Because of the importance of fish location, an individual-based model appears to be a nearly inescapable modeling requirement. There is, however, a paucity of field-based data directly relating birth, death, and movement rates to habitat conditions experienced by individual fish. There is also a paucity of habitat information at a fine temporal and spatial scale for many important habitat variables. Finally, the general occurrence of strong ontogenetic changes in the response of different life stages to habitat conditions emphasizes the need for a modeling approach that considers all life stages in an integrated fashion.

Removal of Walleye Eggs from Reefs in Western Lake Erie by a Catastrophic Storm

Abstract We document the removal of walleye Stizostedion vitreum eggs from reefs in western Lake Erie by a gale-force storm event during April 1998. From April 8 to April 10 of that year, the western basin reefs were exposed to sustained winds exceeding 80 km/h and originating from the east-northeast. This storm produced waves in excess of 4 m on the reefs and caused extensive flooding along the Ohio and Michigan shorelines owing to seiche activity. We sampled eggs on Cone, Crib, Locust Point, Niagara, Round, and Toussaint reefs on April 6, the day before the storm, and on April 10, the day after the storm. We found approximately 80% fewer eggs in the samples collected on April 10, a difference that was significant. Shallow sites on reefs lost significantly more eggs (87%) than deep sites (50%). The lower loss rate of eggs from deep sites was thought to be related to reduced wave energy at greater depths. The results of this study emphasize the importance of physical processes in structuring walleye early...

Variable Effects of Habitat Enhancement Structures across Species and Habitats in Michigan Reservoirs

Abstract The addition of habitat enhancement structures to aquatic systems is a common practice by fisheries managers hoping to increase production, spawning success, and angler catch rates of important sport fishes. However, quantitative evaluations of these efforts are few and typically do not include the extent to which natural habitat mediates the effects of habitat enhancement structures. We evaluated the effects of two types of habitat enhancement structure on four fish groups in four reservoirs of the Au Sable River, Michigan. Using a combination of sampling methods, we compared several response variables (including relative abundance, nesting, and angler catch rates) between areas with and without structures, as well as before and after structure placement, across a gradient of natural habitat conditions. The effects of half-log habitat enhancement structures were significant in some cases, but no significant effects were detected for AquaCrib structures. Smallmouth bass Micropterus dolomieu respo...