Beaver Archipelago Research Articles

Microbial community structure and microbial networks correspond to nutrient gradients within coastal wetlands of the Laurentian Great Lakes.

ABSTRACTMicrobial communities within the soil of Laurentian Great Lakes coastal wetlands drive biogeochemical cycles and provide several other ecosystem services. However, there exists a lack of understanding of how microbial communities respond to nutrient gradients and human activity in these systems. This research sought to address the lack of understanding through exploration of relationships among nutrient gradients, microbial community diversity, and microbial networks. Significant differences in microbial community structure were found among coastal wetlands within the western basin of Lake Erie and all other wetlands studied (three regions within Saginaw Bay and one region in the Beaver Archipelago). These diversity differences coincided with higher nutrient levels within the Lake Erie region. Site-to-site variability also existed within the majority of the regions studied, suggesting site-scale heterogeneity may impact microbial community structure. Several subnetworks of microbial communities and individual community members were related to chemical gradients among wetland regions, revealing several candidate indicator communities and taxa that may be useful for Great Lakes coastal wetland management. This research provides an initial characterization of microbial communities among Great Lakes coastal wetlands and demonstrates that microbial communities could be negatively impacted by anthropogenic activities.

A Disconnect between Science and Management for Double-Crested Cormorants (Phalacrocorax auritus) in Northern Lake Michigan, USA, 2000–2016

In 2000, studies began on the Double-crested Cormorant (Phalacrocorax auritus) in the Beaver Archipelago, Lake Michigan, Michigan, USA, and have continued through the present. Research was conducted to determine whether Double-crested Cormorants were preying on smallmouth bass (Micropterus dolomieu) and causing a decline in this fishery. Breeding Double-crested Cormorant population estimates were recorded to document population dynamics before management and throughout the intensive control program, initiated in 2007. Research included studies using telemetry, raft surveys, banding, game cameras, and development of several bioenergetics models. In addition, co-nesting species were monitored to investigate impacts of Double-crested Cormorant control on non-target species. Results indicated that Double-crested Cormorants do not negatively impact smallmouth bass populations, co-nesters or other components of the system. However, control measures were initiated and continued through 2015; litigation ended control activities in 2016. Research suggested that control led to abandonment by Double-crested Cormorants of traditional colony sites, a switch from ground to tree nesting, and impacts on co-nesting species. This review demonstrates a significant disconnect between science-based knowledge and chosen management practices. Although court rulings ceased Double-crested Cormorant control, this disconnect should be addressed and remedied; science-based knowledge should be emphasized in any future management.

Relationships between habitat characteristics and round goby abundance in Lakes Michigan and Huron

Abstract Expanding round goby ( Neogobius melanostomus ) populations threaten many native species throughout the Great Lakes. The qualities that make a habitat suitable for round gobies are oftentimes considered as single factors (e.g., substrate type or dreissenid mussels). A more thorough understanding of the environmental characteristics related to round goby abundance can help identify habitats that are less susceptible to invasion. This study examined the habitat characteristics associated with round goby abundance in the Beaver Archipelago of Lake Michigan and the Les Cheneaux and Saginaw Bay regions of Lake Huron. Chemical and physical variables, zooplankton, macroinvertebrate, and fish assemblages were sampled from open water and wetland habitats. Gradients in habitat characteristics, determined using ordination analyses and diversity indices, were correlated with round goby catch per unit effort (CPUE) using fyke nets. Round goby CPUE in the Beaver Archipelago was positively related to increasing productivity and a more diverse fish community. Round goby CPUE at Les Cheneaux was related to wave disturbance and fish species associated with greater habitat complexity, though habitat type alone did not explain these relationships. In contrast, round goby CPUE in highly productive Saginaw Bay wetlands was very low where fish diversity was high and assemblages were dominated by littoral species tolerant of eutrophic conditions. Overall, CPUE was related to indices of biological productivity, with the direction of these relationships varying among regions. Areas with high productivity, including some wetlands, may be less hospitable for round gobies and could serve as refugia for native species.

Double-Crested Cormorants (Phalacrocorax auritus) on the Move in the Beaver Archipelago, Northern Lake Michigan

Double-crested Cormorant (Phalacrocorax auritus) foraging locations in northern Lake Michigan were recorded in 2003 and 2010. In the interim, the invasive round goby (Neogobius melanostomus) appeared in 2006, and control of Double-crested Cormorants was initiated in 2007. Spatial data from 2003 and 2010 were analyzed to determine whether foraging distributions differed between sample periods. A multi-response permutation procedure found that a significant shift in foraging locations occurred between sample periods. Groups of Double-crested Cormorants foraged in the same key locations in both years, but foraging range expanded overall in 2010. Range expansion could be a response to the presence of the round goby, which is an abundant food source throughout Lake Michigan. The 2010 foraging location data corresponded with the early departure of Double-crested Cormorants from the Beaver Archipelago. The combined effects of control and the appearance of round goby in diets resulted in changes in numbers and distributions of foraging Double-crested Cormorants.

Double-crested Cormorant (Phalacrocorax auritus) chick bioenergetics following round goby (Neogobius melanostomus) invasion and implementation of cormorant population control

As the fish community changed in the Beaver Archipelago (northern Lake Michigan), so has the diet of breeding Double-crested Cormorants (Phalacrocorax auritus). In 2000, the energetically dense alewife (Alosa pseudoharengus) dominated the diet, but more recently, the relatively low quality round goby (Neogobius melanostomus) has become the most common prey item. Additionally, cormorant control measures have been underway in the archipelago. This study investigated decreases in cormorant chick numbers and changes in chick bioenergetics in response to this change in diet, as well as the influence of control efforts, and compared these results to an earlier study. Two colonies, one actively controlled the other only controlled following completion of this study, were investigated to determine changes in colony size throughout the breeding season, document chick diet, measure chick growth, and determine chick survivorship to fledging. The bioenergetics model estimated that in 2010, chicks consumed a greater biomass of prey to reach fledging due to the change in diet, but lower biomass overall due to fewer chicks in the system. Control efforts in combination with the change in diet reduced chick numbers. Overall, the impact of cormorant chicks on available fish biomass has declined in recent years due to control efforts. However, the birds have the potential to consume a greater biomass of round goby in the absence of control. The impact of cormorants on fisheries resources is complicated by the abundance and effects of non-native species.

Comparing Decadal Census Trends and Yearly Variation in Abundance and Distribution of Breeding Double-Crested Cormorants: Importance of Monitoring a Managed Species

Abstract. Binational colonial waterbird censuses were formally initiated in the Great Lakes in 1976, and have been repeated every eight to ten years. Although population estimates from these efforts are good trend indicators for some species, including Double-crested Cormorant (Phalacrocorax auritus), information is generally not available to examine population changes between census periods, especially at a local scale. The study examined shortterm, annual population changes and distribution patterns of cormorants in the Beaver Archipelago of northern Lake Michigan between 2000 and 2007, and compared these data to decadal trends. Although no control efforts were underway between 2000 and 2006, an egg-oiling and culling program was initiated in 2007, after the completion of the decadal census. The peak number of breeders was documented in 1997, with lower population sizes between 2000 and 2006; however, in 2007, the population again approached peak numbers, suggesting that immigration from other regions o...

Use of wetland versus open habitats by round gobies in lakes Michigan and Huron: Patterns of CPUE, length, and maturity

It has been suggested that some Great Lakes coastal wetlands may be resistant to invasion by several non-indigenous species including round goby, Neogobius melanostomus. However, there is inconclusive evidence regarding how susceptible exposed fringing coastal wetlands, in particular, are to round goby invasion. Therefore, we quantified round goby catch per unit effort (CPUE) using fyke nets in the Beaver Archipelago of Lake Michigan, and the Les Cheneaux islands and Saginaw Bay regions of Lake Huron. In addition, we examined the influence of body size and maturity on round goby habitat use. Catch per unit effort from fyke nets was highest in the Beaver Archipelago, where wetlands were dominated by small, immature round gobies and open water habitats were dominated by large adults. Fyke net catches within Les Cheneaux sites were similar between habitats and differences in size and maturity were not observed. Conversely, very few round goby were captured in wetlands of Saginaw Bay where CPUE was moderate in open water. This indicates that some exposed fringing wetlands in the Great Lakes, specifically those with high productivity, could have a higher degree of resistance to round goby invasion.

Fish Assemblage Shifts and Population Dynamics of Smallmouth Bass in the Beaver Archipelago, Northern Lake Michigan: A Comparison between Historical and Recent Time Periods amidst Ecosystem Changes

AbstractThe ecological and economic importance of Great Lakes nearshore areas and the paucity of information on nearshore Lake Michigan fish assemblages prompted us to document changes that occurred from a historical time period (1969–1972, 1975, 1977, and 1984) to a recent period (2005–2008) in a nearshore northern Lake Michigan (Beaver Archipelago) fish assemblage, with an emphasis on smallmouth bass Micropterus dolomieu. From historical to recent periods, the Beaver Archipelago fish assemblage shifted from predominantly brown bullheads Ameiurus nebulosus to predominantly smallmouth bass. Relative abundance of brown bullheads and white suckers Catostomus commersonii declined from historical to recent time periods, as did overall species richness. The relative abundance, recruitment variability, and mortality rates of smallmouth bass have not significantly changed since the historical time period, whereas both condition (ages 5–7) and growth (ages 2–7) of this species have significantly increased. Our results suggest that the smallmouth bass population in the Beaver Archipelago area has not been negatively affected by recent ecological changes (i.e., declining primary productivity, increasing benthic invertebrate densities, increasing numbers of double‐crested cormorants Phalacrocorax auritus, and increasing introductions of nonnative species). The smallmouth bass is currently the dominant nearshore species and remains a critical component of the nearshore fish assemblage in northern Lake Michigan.

Movement of smallmouth bass within the Beaver Island Archipelago, northern Lake Michigan

Fish movement may vary across a wide array of aquatic ecosystems and may be related to the overall size of the system inhabited. We investigated movement of smallmouth bass in Lake Michigan because this information is lacking for larger systems. A total of 16 smallmouth bass were surgically implanted with ultrasonic transmitters within the Beaver Archipelago, northern Lake Michigan. During 2007–2008, a maximum of one location per individual was recorded daily during three specific tracking periods – pre-spawn, spawning, and post-spawn – to determine diurnal movement patterns. Movement was evaluated as site fidelity, minimum displacement rate, maximum excursion rate, and distance from shore. Smallmouth bass exhibited greater maximum excursion rates during the spawn period compared to pre-spawn. Movement rates did not differ between tracking periods; however, movement rates were greater during the spawn period in 2007 than 2008. Both sexes moved further offshore to deeper water during post-spawn, but females were located further offshore than males during this period. Annual site fidelity was more evident during post-spawn than during spawning for both sexes. Two smallmouth bass emigrated outside of the Archipelago, suggesting this population may be more “open” in terms of individuals moving throughout northern Lake Michigan than previously thought. These results indicate smallmouth bass may move greater distances in larger aquatic systems and therefore larger management units (in terms of total area) should be established in Lake Michigan to account for these greater excursion distances.

Bioenergetics and Prey Consumption of Breeding Double-crested Cormorants in the Beaver Archipelago, Northern Lake Michigan

Colonial waterbirds are an important component of Great Lakes ecosystems. In order to investigate the role these birds play in an aquatic food web, bioenergetics models, using allometric equations, were applied to breeding double-crested cormorants ( Phalacrocorax auritus) and their offspring in the Beaver Archipelago, northern Lake Michigan. These models were parameterized using detailed information collected during the 2000 and 2001 breeding seasons, as well as literature values. Each breeding season was divided into stages in the models to reflect changes in cormorant diet and population size documented in the study area. The models estimated the total prey biomass consumed as 1,445 metric tonnes (mt) of prey in 2000, and 1,585 mt of prey in 2001. Each year, the majority of the prey biomass was alewife ( Alosa pseudoharengus), with these fish comprising a greater percentage of prey biomass consumed in 2001. An increase in cormorant reproductive success in 2001 may be linked to this increase in alewife biomass consumed; the breeding bird population size, however, declined in 2001 as compared to 2000. The other prey items, which are not considered to be species of commercial or sport value, were also important contributors to bird diet and consumption of these species did tend to vary from year-toyear. Overall, the application of bioenergetics models allows for greater understanding of the role of cormorants as predators and as energy links in the system.

Foraging Locations of Double-crested Cormorants in the Beaver Archipelago of Northern Lake Michigan: Potential for Impacts on Smallmouth Bass

Abstract The breeding population of Double-crested Cormorants (Phalacrocorax auritus) increased in the Beaver Archipelago of northern Lake Michigan, while simultaneously, a Smallmouth Bass (Micropterus dolomieui) population in the region declined. However, the role that cormorants played in this decline has remained uncertain. During summer 2003, VHF radiotelemetry and rafting locations were used to determine whether birds foraged primarily in bass habitat. The foraging activities of ten breeding cormorants were monitored by radiotelemetry from both land and water on a daily basis, weather permitting, throughout the breeding season. In addition, cormorant foraging raft locations were documented by boat survey throughout the breeding season. Radiotelemetry indicated that cormorants typically foraged 2.5 km away from their colonies, at the northeastern end of Beaver Island. This area overlaps with the area determined from rafting locations; however the latter were centered further south. These data allow fo...

A comparison of three methods to investigate the diet of breeding double-crested cormorants (Phalacrocorax auritus) in the Beaver Archipelago, northern Lake Michigan

A comparison of three methods to investigate the diet of breeding double-crested cormorants (Phalacrocorax auritus) in the Beaver Archipelago, northern Lake Michigan

Geographic and Size-related Variation in the Diet of Insular Populations of the Northern Watersnake

I studied microgeographic and size-related variation in the diet composition of the Northern Watersnake Nerodia sipedon sipedon in the Beaver Archipelago of Lake Michigan. Snakes from Lake Michigan shoreline sites were piscivorous whereas snakes from interior sites on Beaver Island ate mostly amphibians. Sculpin (Cottus sp.) were the dominant prey of all size classes, but a gradual size-related shift in diet may be occurring in archipelago snakes. Large snakes tended to eat larger prey than small snakes and to drop the smallest prey from their diets, but overlap in prey size occurred among all size classes of snakes. The diet composition of snakes from different sites is likely a reflection of local differences in prey abundance, as found in several previous studies. The overlap in prey size and prey type among snake size classes contradicts the results of some previous studies of Nerodia sp. and merits further investigation.

Frequency of Tail Breakage of the Northern Watersnake, <em>Nerodia sipedon sipedon</em>

I noted the frequency of broken tails of Northern Watersnakes, Nerodia sipedon sipedon, in the Beaver Archipelago of Northeastern Lake Michigan. Overall, 10% (22 of 220) of captured snakes had broken tails. This value is similar to published values for closely related snakes but is smaller than those reported for another Nerodia sipedon sipedon population. Unlike some previously published studies, the frequency of injured tails was not greater for females or lesser for first-year snakes. The mechanism behind the injury frequency observed here and the reason for differences between this and other studies are unknown.

Multivariate Analysis of Head Shape in Thamnophis s. sirtalis (Serpentes: Colubridae) among Island and Mainland Populations from Northeastern Lake Michigan

-Morphological variation in 14 head dimensions of 333 eastern garter snakes from four islands of the Beaver archipelago and adjacent Waugoshance Point, Michigan, was analyzed by multivariate statistical methods. Five principal component axes explained 62.8% of the variation in the data set. Statistically significant (P < 0.05) differences in head shape were found both among island populations and between islands and the mainland. Based on Mantel tests, the structure of the morphological variation was concordant neither with the history of geological events following the last glacial retreat nor with the genetic population structure derived from allozyme data. We suggest that natural selection based on prey availability may have effected the observed variation among these snake populations.