Geology topics

Bruce M. Davis

Publications and source records attributed to Bruce M. Davis.

11 recordsLinked to original sources

USGS2015

Diet shifts by planktivorous and benthivorous fishes in northern Lake Michigan in response to ecosystem changes

In Lake Michigan, diets of planktivorous and benthivorous fishes have varied over the past decades, in part owing to food web changes. To update diet information and compare them to a similar effort in 1994–1995, we analyzed the diets of seven benthivorous and planktivorous fish species collected along two northern Lake Michigan transects that spanned nearshore (18 m), intermediate (46 m), and offshore (91, 110, 128 m) bottom depths during spring, summer, and autumn of 2010. Calanoid copepods (e.g., Limnocalanus macrurus, Leptodiaptomus sicilis, and Senecella calanoides) comprised a majority of the diets in at least one season for all sizes of alewife (Alosa pseudoharengus), bloater (Coregonus hoyi), and rainbow smelt (Osmerus mordax). Similarly, Mysis diluviana was the highest proportion in at least one season for large sizes of alewife, bloater, and rainbow smelt, as well as slimy sculpin (Cottus cognatus) and deepwater sculpin (Myoxocephalus thompsonii). The diets of the remaining two species, ninespine stickleback (Pungitius pungitius) and round goby (Neogobius melanostomus), were dominated by herbivorous cladocerans or dreissenid mussels, respectively. Interspecific diet overlap was minimal at 18 and 46 m. In offshore waters, however, overlap was relatively high, driven by frequent consumption of Mysis. Relative to 1994–1995, 2010 diets revealed increased feeding on calanoid copepods and Mysis, with corresponding declining consumption of Diporeia spp. and herbivorous cladocerans. Relative diet weight was also higher in 1994–1995 than in 2010 for small and large bloater and both sculpin species. We hypothesize that the shifts in diets are reflective of community-level changes in invertebrate prey availability.

Wisconsin and Michigan↗

USGS2013

Feeding ecology of pelagic larval Burbot in Northern Lake Huron, Michigan

Burbot Lota lota are a key demersal piscivore across the Laurentian Great Lakes whose populations have declined by about 90% in recent decades. Larval Burbot typically hatch in the early spring and rely on abundant crustacean zooplankton prey. We examined the stomach contents of larval Burbot from inshore (≤15 m) and offshore sites (37 and 91 m) in northern Lake Huron, Michigan. Concurrent zooplankton vertical tows at the same sites showed that the prey community was dominated by calanoid copepods, dreissenid mussel veligers, and rotifers. Burbot consumed mostly cyclopoid copepods, followed by copepod nauplii and calanoid copepods. Chesson's index of selectivity was calculated and compared among sites and months for individual Burbot. According to this index, larval Burbot exhibited positive selection for cyclopoid copepods and copepod nauplii and negative selection for calanoid copepods, cladocerans, rotifers, and dreissenid veligers. This selectivity was consistent across sites and throughout the sampling period. Burbot displayed little variation in their prey preferences during the larval stage, which suggests that the recent shifts in zooplankton abundance due to the invasion of the predatory zooplankter Bythotrephes longimanus and competition from invasive Rainbow Smelt Osmerus mordax could negatively impact larval Burbot populations.

Michigan↗

USGS2012

Comparing seasonal dynamics of the Lake Huron zooplankton community between 1983-1984 and 2007 and revisiting the impact of Bythotrephes planktivory

Zooplankton community composition can be influenced by lake productivity as well as planktivory by fish or invertebrates. Previous analyses based on long-term Lake Huron zooplankton data from August reported a shift in community composition between the 1980s and 2000s: proportional biomass of calanoid copepods increased while that of cyclopoid copepods and herbivorous cladocerans decreased. Herein, we used seasonally collected data from Lake Huron in 1983–1984 and 2007 and reported similar shifts in proportional biomass. We also used a series of generalized additive models to explore differences in seasonal abundance by species and found that all three cyclopoid copepod species ( Diacyclops thomasi, Mesocylops edax, Tropocyclops prasinus mexicanus ) exhibited higher abundance in 1983–1984 than in 2007. Surprisingly, only one ( Epischura lacustris ) of seven calanoid species exhibited higher abundance in 2007. The results for cladocerans were also mixed with Bosmina spp. exhibiting higher abundance in 1983–1984, while Daphnia galeata mendotae reached a higher level of abundance in 2007. We used a subset of the 2007 data to estimate not only the vertical distribution of Bythotrephes longimanus and their prey, but also the consumption by Bythotrephes in the top 20 m of water. This epilimnetic layer was dominated by copepod copepodites and nauplii, and consumption either exceeded (Hammond Bay site) or equaled 65% (Detour site) of epilimnetic zooplankton production. The lack of spatial overlap between Bythotrephes and herbivorous cladocerans and cyclopoid copepod prey casts doubt on the hypothesis that Bythotrephes planktivory was the primary driver underlying the community composition changes in the 2000s.

Lake Huron↗

USGS2009

Lake St. Clair zooplankton: Evidence for post-Dreissena changes

We surveyed the zooplankton of Lake St. Clair at 12 sites over ten dates from May to October 2000. Mean zooplankton density by site and date was 168.6 individuals/L, with Dreissena spp. veligers the most abundant taxon at 122.7 individuals/L. Rotifers, copepods, and cladocerans were far lower in mean abundance than in the early 1970s (rotifers, 20.9/L; copepods, 18.1/L; and cladocerans, 6.8/L). Species richness of zooplankton taxa in 2000 was 147, which was virtually unchanged from that of the first reported survey in 1894. Overall, the decline in abundance was greatest for rotifers (-90%) and about equal for cladocerans (-69%) and copepods (-66%). The decrease in abundance of Daphnia spp. was especially dramatic in Canadian waters. The decline in the southeastern region was significant for all three major groups of zooplankton, whereas in the northwestern region the decline was significant only for rotifers. From June to August 2000, Lake St. Clair open waters were numerically dominated by Dreissena spp. veligers, with a reduced abundance of rotifers and crustaceans compared to pre-Dreissena spp. surveys. Mean nutrient concentrations were not different from the 1970s, but Secchi depth (greater) and chlorophyll a concentration (lower) were. Disproportionate reduction in rotifer abundance is consistent with hypotheses implicating direct consumption by settled Dreissena spp. Reduction of crustaceans is likely due to more complex interactions including removal of nauplii as well as resource competition for phytoplankton.

Michigan, Ontario↗

USGS2004

Characterization of Lake Michigan coastal lakes using zooplankton assemblages

Zooplankton assemblages and water quality were examined bi-weekly from 17 April to 19 October 1998 in 11 northeastern Lake Michigan coastal lakes of similar origin but varied in trophic status and limnological condition. All lakes were within or adjacent to Sleeping Bear Dunes National Lakeshore, Michigan. Zooplankton (principally microcrustaceans and rotifers) from triplicate Wisconsin net (80 I?m) vertical tows taken at each lake's deepest location were analyzed. Oxygen-temperature-pH-specific conductivity profiles and surface water quality were concurrently measured. Bray-Curtis similarity analysis showed small variations among sample replicates but large temporal differences. The potential use of zooplankton communities for environmental lake comparisons was evaluated by means of BIOENV (Primer 5.1) and principal component analyses. Zooplankton analyzed at the lowest identified taxonomic level yielded greatest sensitivity to limnological variation. Taxonomic and ecological aggregations of zooplankton data performed comparably, but less well than the finest taxonomic analysis. Secchi depth, chlorophyll a, and sulfate concentrations combined to give the best correlation with patterns of variation in the zooplankton data set. Principal component analysis of these variables revealed trophic status as the most influential major limnological gradient among the study lakes. Overall, zooplankton abundance was an excellent indicator of variation in trophic status.

Ecological Indicators↗

USGS2002

Application of truss analysis for the quantification of changes in fish condition

Conservation of skeletal structure and unique body ratios in fishes facilitated the development of truss analysis as a taxonomic tool to separate physically-similar species. The methodology is predicated on the measurement of across-body distances from a sequential series of connected polygons. Changes in body shape or condition among members of the same species can be quantified with the same technique, and we conducted a feeding experiment using yellow perch ( Perca flavescens ) to examine the utility of this approach. Ration size was used as a surrogate for fish condition, with fish receiving either a high (3.0% body wt/d) or a low ration (0.5%). Sequentially over our 11-week experiment, replicate ration groups of fish were removed and photographed while control fish were repeatedly weighed and measured. Standard indices of condition (total lipids, weight-length ratios, Fulton's condition) were compared to truss measurements determined from digitized pictures of fish. Condition indices showed similarity between rations while truss measures from the caudal region were important for quantifying changing body shape. These findings identify truss analysis as having use beyond traditional applications. It can potentially be used as a cheap, accurate, and precise descriptor of fish condition in the lab as shown here, and we hypothesize that it would be applicable in field studies.

Journal of Aquatic Ecosystem Stress and Recovery↗

USGS1998

Competition between larval lake herring (Coregonus artedi) and lake whitefish (Coregonus clupeaformis) for zooplankton

Diet and growth of larval lake herring (Coregonus artedi) and lake whitefish (Coregonus clupeaformis) were compared in mesocosm experiments in a small mesotrophic lake in southeastern Michigan. Fish were sampled from single-species and mixed assemblages in 2-m 3 cages for 8 weeks during April and May. Both species initially ate mostly cyclopoid copepodites and small cladocerans (Bosmia spp.). Schoener's index of diet overlap showed considerable overlap (70-90%). Lake whitefish ate Daphnia spp. and adult copepods about 2 weeks earlier than did lake herring, perhaps related to their larger mean mouth gape. Lake whitefish were consistently larger than lake herring until the eighth week, especially in the sympatric treatments. Lake whitefish appeared to have a negative effect on the growth of lake herring, as lake herring in mixed-species treatments were smaller and weighed less than lake herring reared in single-species treatments. The diet similarities of lake whitefish and lake herring larvae could make them competitors for food in the Great Lakes. The greater initial size of lake whitefish could allow them to eat larger prey earlier and thereby limit availability of these prey to lake herring at a crucial period of development.

Michigan↗

USGS1995

Effects of fish density and relative abundance on competition between larval lake herring and lake whitefish for zooplankton

Competition for zooplankton between larval lake herring ( Coregonus artedi ) and lake whitefish ( C. clupeaformis ) was compared in mesocosm experiments in a small lake. Both species were combined in test enclosures at relative abundances of 1:1 or 1:4 lake herring to lake whitefish at densities of 500; 1, 000; and 2, 000 fish per cage, and were allowed to feed ad libitum on available zooplankton. After 60 days, at 500 fish per cage and a 1:1 ratio, lake whitfish were significantly larger than lake herring. At 1, 000 and 2, 000 fish per cage, lake herring and lake whitefish exhibited similar depressed growth rates. Survival was lower (30-50%) in the nets with 2, 000 fish than in the lower fish densities. We suspect that diet similarities of juvenile lake herring and lake whitefish in addition to the larger size and more aggressive behavior of larval lake whitefish resulted in the depressed growth and poorer survival for lake herring.

Book chapter↗

USGS1994

Effects of pulsed turbidity and vessel traffic on lake herring eggs and larvae

Proposals to extend commercial shipping in the St. Marys River (connecting Lakes Superior and Huron) to include winter months have raised concerns regarding its effect on lake herring ( Coregonus artedi ). Because lake herring spawn in fall and their eggs overwinter in the river and hatch in spring, their hatching success could be impacted by early opening of the locks in spring. Our laboratory studies showed that under the range of turbidities expected in the river due to vessel traffic, lake herring eggs hatched and larvae fed adequately. Field incubation studies produced about 75% survival and 70% hatching success of lake herring eggs at two of three study sites. Collections in the river throughout the month following ice-out showed that sufficient plankton of appropriate size were available to ensure growth and survival of larval lake herring. We did not detect any negative impacts on the early life stages of lake herring as a result of sedimentation in the laboratory or field. However, detailing the spawning sites of lake herring and defining the normal survival-to-hatch in these areas are necessary before making accurate predictions of the effects of early season vessel traffic on lake herring hatching success.

Journal of Great Lakes Research↗

USGS1991

Distribution and abundance of caddisflies (Trichoptera) in the St. Clair-Detroit River system

Abundance and distribution patterns of the caddisflies of the St. Clair-Detroit River system were investigated in 1983–84. Collections of both adults and larvae yielded 70 species representing 34 genera and 12 families. Leptoceridae and Hydroptilidae were the most common families and Ceraclea the most common genus in number of species. This study adds 21 species to the Michigan record. The hydropsychids Cheumatopsyche (81, 63, 105 m −2 ; log-transformed values for mean and lower and upper 95% C.L.) and Hydropsyche (70, 57, 87 m −2 ) were the most abundant genera collected as larvae in the St. Clair and Detroit rivers, while Oecetis (41, 35, 47 m −2 ) was the most abundant in Lake St. Clair. Larval densities of caddisflies in the Detroit River were about twice those in the St. Clair River, but the number of genera collected in each river was about equal (22 vs. 23). Larval abundances were higher in October than May because most genera had substantial overwinter population declines. Low densities and species richness in some areas of the St. Clair-Detroit River system may reflect in part continued water quality problems, but community structure has markedly improved and representation of pollution-sensitive organisms has increased over a 12–15 year period.

Michigan↗

USGS1991

The measurement of mangrove characteristics in southwest Florida using spot multispectral data

An intensive in situ sampling program near Marco Island, Florida during 19–23 October 1988 collected information on mangrove type, maximum canopy height, and percent canopy closure. These data were correlated with selected vegetation index information derived from analysis of SPOT multispectral (XS) data obtained on 21 October 1988. The Normalized Difference (ND) vegetation index information was the most highly correlated index with percent canopy closure (r=0.91). Percent canopy closure information can be used as a surrogate for mangrove density which is of great value when predicting which parts of the mangrove ecosystem are at greatest risk after an oil spill occurs. Such information is very valuable when constructing oil spill Environmental Sensitivity Index (ESI) Maps for tropical regions of the world.

Florida↗