Geology topics

Caroline Lynn Rosinski

Publications and source records attributed to Caroline Lynn Rosinski.

4 recordsLinked to original sources

USGS2021

Trophic ecology

The trophic ecology of lake charr Salvelinus namaycush morphotypes from small and large lakes within their native and introduced ranges is reviewed over the past 50 years. The lake charr is an apex predator in most habitats it occupies, where it plays a significant role in defining food webs. While often considered piscivores, lake charr feed on a range of aquatic prey throughout their life history, including zooplankton, benthic invertebrates, and fish, as well as terrestrial insects, mammals, birds, amphibians, and reptiles. Lake charr diets that vary within morphotypes among lakes and among sympatric morphotypes reflect differences in habitat use, prey availability, and individual preferences. Temporal variability in diet can result from seasonal prey pulses, thermal barriers, and long-term prey dynamics. Lake charr adapt quickly to consume invasive prey fishes, and often decimate native prey fishes and other piscivores in lakes into which they are introduced. Salient research topics in lake charr trophic ecology include: (1) how best to quantify spatial and temporal trophic niche space; and, (2) how changing environmental conditions, such as invasive species and lake warming, will influence lake charr feeding and broader lake food-web dynamics.

Book chapter↗

USGS2020

Niche partitioning among native ciscoes and nonnative Rainbow Smelt in Lake Superior

Several species of ciscoes Coregonus , subgenus Leucichthys that are native to the Laurentian Great Lakes are rare or extirpated. The restoration of Coregonus fishes is being actively pursued through stocking, and success may depend on the availability of unoccupied niche space. We described the spring–summer habitat occupancy and diets of three native cisco species (Bloater Coregonus hoyi , Cisco C. artedi, and Kiyi C. Kiyi ) and invasive Rainbow Smelt Osmerus mordax in Lake Superior and measured niche overlap among these species for both small and large sizes. The potential habitat area was highest for Cisco and Kiyi, followed by Bloater and Rainbow Smelt. The probability of overlap in habitat occupation, as measured by bathymetric depth, fish capture depth, distance from shore, and fish capture water temperature was highest for small Rainbow Smelt and Cisco. Trophic overlap, as measured by stomach contents and stable isotopes, was highest between small Bloater and Cisco and between large Bloater and Kiyi. All of the species showed significant ontogenetic change in both habitat occupation and diet. The overall niche overlap in spring–summer habitat and diet was greatest between small Cisco and Rainbow Smelt and between large Bloater and Kiyi; however, differences in individual niche dimensions likely limit competition for both species pairs. Synthesizing the diet and habitat niche data revealed nuanced niches that allow these seemingly similar planktivorous species to coexist. Kiyi had the least niche overlap with other cisco species and Rainbow Smelt, so from an available niche perspective Kiyi would be a strong candidate for reintroduction into lakes from which they were extirpated.

Lake Superior↗

USGS2020

Gut contents from multiple morphs of lake trout (Salvelinus namaycush) at two offshore shoals in Lake Superior

Four lake trout, Salvelinus namaycush , Walbaum 1792 morphs occur in Lake Superior: lean, siscowet, humper, and redfin. Diets of lean and siscowet have been relatively well described. However, less is known about diets of humper and redfin, and overall few studies have been conducted at offshore shoals. We compared gut content data among mature (357–867 mm) sympatric lake trout morphs caught at two offshore shoals in Lake Superior, Stannard Rock and Superior Shoal, in 2013 and 2014 (total n = 416). All morphs were caught in shallow (<50 m), mid (50–100 m), and deep (>100 m) strata. Invertebrates made up a greater portion of the stomach contents than did fish for all morphs by both percent occurrence and proportional biomass, and Mysis was the primary invertebrate consumed by all morphs at both sites. Coregonus spp. and deepwater sculpin, Myoxocephalus thompsonii were the most commonly consumed fish. Humper had the highest average proportional biomass of deepwater sculpin and had no other identifiable species of fish in their guts. Biomass of fish in redfin guts was highest for Coregonus spp., followed by similar amounts of deepwater sculpin and burbot, Lota lota . Diet overlap among morphs was high, and differences in prey consumption between sites are likely related to prey availability. Additional study is needed to determine if differences in trophic ecology between humper and other morphs are sufficient to support concurrent stocking of multiple morphs, particularly in light of recent declines in native prey fishes, especially Coregonus spp., in the Laurentian Great Lakes.

Lake Superior↗

USGS2019

Status and trends in the Lake Superior fish community, 2019

The Lake Superior fish community was sampled in 2019 with daytime bottom trawls at 76 nearshore and 35 offshore stations distributed throughout the lake. In the nearshore zone, 25,131 fish from 24 species or morphotypes were collected. The number of species collected at nearshore stations ranged from 0 to 15, with a mean of 5.6 and median of five. Nearshore mean biomass was 5.7 kg/ha which was similar to the past twenty-year average of 5.2 kg/ha and less than the 42-year period-of-record mean of 8.5 kg/ha. Lake Whitefish, Rainbow Smelt, Longnose Sucker, Bloater, lean Lake Trout, Cisco, Burbot, and siscowet Lake Trout had the highest total collected biomass. In the offshore zone, 13,145 fish from 11 species or morphotypes were collected. The number of species collected at offshore stations ranged from two to six, with a mean 3.6 and median of four. Deepwater Sculpin, Kiyi, and siscowet Lake Trout made up 99% of the total number of individuals and biomass collected in offshore waters. Mean and median offshore biomass for all species in 2019 was 7.0 kg/ha which was greater than the past eight-year average of 6.6 kg/ha. Recruitment, as measured by age-1 densities, was near the period-of-record lakewide average for Lake Whitefish (7 fish/ha) and Rainbow Smelt (137 fish/ha) and was lower than the period-of-record lakewide average for Bloater (4 fish/ha), Kiyi (1 fish/ha), and Cisco (<1 fish/ha). Lakewide average age-1 Cisco densities have been estimated at <1 fish/ha in twelve of the last twenty years. Survival of Coregonus species to age-1 continues to be a major concern of fishery managers.

Lake Superior↗