Geology topics

Chris Olds

Publications and source records attributed to Chris Olds.

5 recordsLinked to original sources

USGS2024

Impacts of artificial rearing on cisco Coregonus artedi morphology, including pugheadedness

Cisco ( Coregonus artedi Lesueur, 1818) in the Laurentian Great Lakes declined throughout the 19th and 20th centuries. Managers are attempting to restore Great Lakes cisco and other coregonines using multiple approaches, including stocking. A potential obstacle to these efforts is that artificially reared coregonines can display deformities and morphological differences compared to wild fish, but the impacts of artificial rearing on cisco morphology are not well understood. We compared morphologies of wild cisco to their artificially reared offspring, including one family that was exposed to three rearing temperature treatments. We found that artificially reared cisco had smaller eyes, shallower bodies, fewer gill rakers, and longer paired fins than their wild parents. We also found that artificially reared cisco were pugheaded, and this result held for another cisco population and rearing facility. Across the temperature treatments we tested, rearing temperatures did not impact the degree of pugheadedness or other morphological differences. Our results have important implications for coregonine restoration efforts. Future work should evaluate whether morphological differences that arise through artificial rearing affect cisco fitness in the wild.

Canadian Journal of Zoology↗

USGS2023

Comparison of traditional and geometric morphometrics using Lake Huron ciscoes of the Coregonus artedi complex

Here we determine how traditional morphometrics (TM) compares with geometric morphometrics (GM) in discriminating among morphologies of four forms of ciscoes of the Coregonus artedi complex collected from Lake Huron. One of the forms comprised two groups of the same deepwater cisco separated by capture depth, whereas the other three forms were shallow-water ciscoes. Our three groups of shallow-water ciscoes were better separated (3% versus 19% overlap) in Principle Component Analysis (PCA) with TM data than with GM data incorporating semilandmarks (evenly spaced nonhomologous landmarks used to bridge between widely separated homologous landmarks). Our two deepwater cisco groups, comprising a putatively single form collected from different depths, separated more in PCAs with GM data (33% overlap) than in PCAs with TM data (66% overlap), an anomaly caused by greater decompression of the swimbladder and deformation of the body wall in the group captured at greater depths. Separation of the two deepwater cisco groups captured at different depths was not affected by the removal of semilandmarks. Assignment of forms using canonical variate analysis (CVA) accurately assigned 86% of individuals using TM data, 98% of individuals using GM data incorporating semilandmarks, and 100% of individuals using GM data without semilandmarks. However, we considered assignments from the same form of deepwater cisco into separate groups as misassignments resulting from different capture depths, which reduced the accuracy of assignments with GM data to 66% with semilandmarks. Our study implies that TM will continue to have an important role in morphological discrimination within Coregonus and other fishes similarly shaped.

Lake Huron↗

USGS2022

Variation of cisco egg size among Laurentian Great Lakes populations

Many fish species display inter-population and inter-individual egg size variation. Intra-specific differences in egg size seemingly reflect both energetic experiences of individual spawning fish and long-term population responses to differing ecosystems. Optimal egg size theory implies that selection influences a population’s mean egg size in response to its early-life environment, given the well-established trade-off between egg size and fecundity. Currently, there is strong interest in rehabilitation of Laurentian Great Lakes cisco, Coregonus artedi, which is characterized by inter-population variation of morphological and behavioral traits. However, the extent of cisco egg size variation is under-described. In fall 2018 and 2019, we collected egg samples by stripping ripe females at seven total locations in four Great Lakes. We measured unfertilized egg diameters using imaging software and compared mean egg diameters among locations with and without including maternal total length as a covariate. Lake Michigan females produced the largest eggs overall but were excluded from analyses using the total length covariate because of their significantly larger body sizes. Maternal length had a positive effect on egg size, and when accounting for this effect, females in Lake Huron produced the largest eggs followed by Lake Ontario and Lake Superior. We also found that egg size varied among locations within Lake Superior. These findings aligned with observations of morphological and behavioral differences among populations and suggest that cisco phenotypic variation at a fine spatial scale extends to reproductive biology. Consideration of cisco reproductive traits, such as egg size, may inform restoration strategies, including supplemental stocking.

Journal of Great Lakes Research↗

USGS2019

Status and trends of pelagic prey fish in Lake Huron, 2018

Scientists from the U.S. Geological Survey’s Great Lakes Science Center conducted integrated acoustic and mid-water trawl surveys of Lake Huron annually from 2004-2018. The 2018 survey was conducted during September and included transects in Lake Huron’s main basin, Georgian Bay, and North Channel. Mean lake-wide pelagic fish density was 1532 fish/ha and mean pelagic fish biomass was 4151 g/ha in 2018, which represents 128% and 108% of the long-term mean, respectively. Mean lake-wide biomass was 24% lower in 2018 and mean lake-wide fish density was 3.3% lower in 2018 as compared to 2017. Lake-wide density and biomass of small alewife (< 100 mm) increased significantly in 2018 and was due primarily to increased abundance in the western main basin. Lake-wide density of small rainbow smelt (< 90 mm) increased in 2018 and was a result of increased abundance in the eastern main basin, Georgian Bay, and the North Channel. Biomass of large rainbow smelt (> 90 mm) increased in 2018 and was a result of increased biomass in the main basin and Georgian Bay. Density of small bloater (< 120 mm) declined in the western main basin but increased in other regions of Lake Huron. Biomass of large bloater (> 120 mm) remained at levels similar to 2017 in most regions of Lake Huron. Emerald shiner density and biomass increased in 2018 due to increased abundance in the main basin south and main basin west regions. Density and biomass of large cisco (> 200 mm) declined marginally between 2017 and 2018, but cisco biomass and density has shown an increasing trend in the North Channel and Georgian Bay since 2011.

Lake Huron↗

USGS2018

Status and trends of pelagic prey fish in Lake Huron, 2017

Scientists from the U.S. Geological Survey’s Great Lakes Science Center conducted integrated acoustic and mid-water trawl surveys of Lake Huron in 1997 and annually from 2004-2017. The 2017 survey was conducted during September and included transects in Lake Huron’s main basin, Georgian Bay, and North Channel. Mean lake-wide pelagic fish density was 1582 fish/ha and mean pelagic fish biomass was 10.5 kg/ha in 2017, which represents 96% and 93% of the long-term mean respectively. Mean lake-wide biomass was 23% higher in 2017 as compared to 2016. The total estimated lake-wide standing stock biomass of pelagic fish species, excluding cisco, was ~49 kt (± 10.4 kt), consisting almost entirely of bloater (26.8 kt; 55%) and rainbow smelt (22 kt; 45%), with small contributions from sticklebacks (0.13 kt; 0.26 %), emerald shiner (0.09 kt; 0.18%), and alewife (0.004kt; <0.005%). Age-0 rainbow smelt abundance increased from 155 fish/ha in 2016 to 598 fish/ha in 2017. Biomass of age-1+ rainbow smelt increased from 2.5 kg/ha in 2016 to 4.1 kg/ha in 2017. Age-0 bloater abundance increased from 94 fish/ha in 2016 to 342 fish/ha in 2017. Biomass of age-1+ bloater in 2017 (5.0 kg/ha) remained at levels similar to 2016 (5.2 kg/ha). Emerald shiner density decreased from 38.6 fish/ha in 2016 to 19.5 fish/ha in 2017. Emerald shiner biomass remained at 0.02 kg/ha between 2016-2017 which represented 19% of the long-term mean. Cisco lake-wide mean biomass was estimated at 2.2 kg/ha and mean density was estimated at 5.1 fish/ha in 2017. Bloater and rainbow smelt will likely continue to be the primary pelagic species available to offshore predators in coming years.

Michigan, Ontario↗