The interactive effects of temperature and food consumption on growth of larval Arctic cod (Boreogadus saida): a bioenergetic model

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in David, C. L., Ji, R., Bouchard, C., Hop, H., & Hutchings, J. A. The interactive effects of temperature and food consumption on growth of larval Arctic cod (Boreogadus saida): a bioenergetic model. Elementa: Science of the Anthropocene, 10(1), (2022): 00045, https://doi.org/10.1525/elementa.2021.00045.Understanding larval growth, mediated by the interaction of early life traits and environmental conditions, is crucial to elucidate population dynamics. We used a bioenergetic model as an integrative tool to simulate the growth of Arctic cod (Boreogadus saida) larvae and to test the sensitivity of modeled growth to temperature and food quantity and quality. The growth was computed as the energy gained through food consumption minus the energy lost through respiration and other metabolic processes. We extended a previously published bioenergetic model to cover the full range of larval length and used a simplified feeding module. This simplification allowed us to build a predictive tool that can be applied to larval Arctic cod at a large spatial scale. Our model suggested that with subzero temperatures in the High Arctic, larvae need to increase food consumption in order to reach the observed length-at-age in late summer. The modeled growth agreed well with the field observations in the High Arctic but was 2–3 times higher than the laboratory-derived growth rate, probably due to differences in food type and selective mortality. Our study reveals important knowledge gaps in our understanding of larval cod growth in the High Arctic, including the lack of empirical estimations of daily ration and respiration for larvae under the natural habitat temperatures.This research was undertaken thanks in part to funding from the Canada First Research Excellence Fund, through the Ocean Frontier Institute

Comparison of Expiring CP-25 and 3-Year Old CP-42 Plantings for Monarch Habitat Quality

Monarch butterflies have experienced a population decline of more than 80% in the past two decades, driven by the emergence of Roundup Ready beans and corn varieties. This development resulted in landowners spraying herbicides and killing all other plants in their field, including milkweeds, which is the genus of plants (Asclepias) that monarch caterpillars can only feed upon. Along with this development, an initiative to reintroduce native prairie ecosystems as part of the Conservation Reserve Program (CRP). In Iowa, over 80% of the land once was home to this prairie, now less than 0.1% of this rare ecosystem remains. Reintroducing this prairie to the environment is a necessary step to improving monarch populations. The University of Northern Iowa’s Tallgrass Prairie Center (UNI TPC) is investigating the quality and availability of tallgrass prairie habitat for monarch butterflies. Two CRP programs of interest are the CP-25 and CP-42 plantings. CP-25 are 10-15-year old fields with no milkweed planted and a mixture of grasses and forbs while CP-42 is planted for pollinator use and includes many milkweed and nectar producing plants. There are 218,482 acres of CP-42 planted in Iowa with over 400,000 acres planted countrywide. In 2021, 17 expiring CP-25 research sites were chosen and sampled for plant abundance and ground cover. Nested quadrats provided frequency data to procure 100 m2 of sampling area that was then collated with 3-year old CP-42 site frequency data. This planting comparison was used to evaluate the milkweed density, nectar plant frequency, and frequency by flowering period by changing the time and seed mix. We hypothesized that the younger planting would produce more nectar-producing species and habitat for the monarch butterflies to feed and lay eggs in. Results indicate that CP-42 fields were significantly higher in nectar-producing species abundance in the early flowering period relative to the CP-25 fields (p-value: 0.005); however, overall frequency of nectar plants in the middle and late flowering periods were comparable across seed mixes (p-values of 0.356 and 0.163, respectively). Milkweed density was slightly greater on CP-25 sites, 0.263 stems/m2 as opposed to 0.247 for CP-42, but more data is needed to evaluate the effects of nectar plant flowering time and resource availability on monarch habitat quality. Our results suggest that implementation of fewer milkweed plantings and greater abundance of early season nectar availability is needed to improve monarch larval habitat. CRP sites of differing mixes and ages showed similarities in nectar availability, suggesting that floral resources for monarch butterflies are not a problem

Spontaneous abortion rate and advanced maternal age: Consequences for prenatal diagnosis

Abstract Maternal age related and procedure-related fetal abortion rates were studied in 384 women aged 36 and over scheduled for transabdominal chorionic villus sampling (TA-CVS) at 12-14 weeks of gestation. The pre-TA-CVS abortion rate within 30 days of intake (at 6-10 weeks of gestation) rose from 1·9% at age 35-36 years to 10·9% at 40 years and older. Women entering in the 6th week of gestation had a greater probability of aborting before TA-CVS than women entering after day 48. 26 women aborted spontaneously before TA-CVS, the majority of abortions occuring at 10-12 weeks. TA-CVS was done in 346 women. 11 pregnancies were terminated because of genetic anomalies, and 8 women had spontaneous fetal loss. These findings justify delaying prenatal diagnosis in older pregnant women until 12 weeks of gestation