Month: November 2021

Lucas Jones presents his Masters Thesis research!

Posted on November 27, 2021November 27, 2021 by Hannes Baumann

The UConn Department of Marine Sciences

Presents a Master’s Thesis Presentation by

Lucas Jones

B.A., University of Connecticut, 2018

4:00 p.m., Monday, November 22, 2021

Marine Sciences Building, Seminar Room 103

**Using Low-Coverage, Whole Genome Sequencing to Study Northern Sand Lance (Ammodytes dubius) Population Connectivity in the Northwest Atlantic**

Northern sand lance (Ammodytes dubius) are key forage fish in Northwest Atlantic (NWA) shelf ecosystems, where they exclusively occur on coarse-grain, offshore sand banks. This patchy occurrence may result in genetically more fragmented, less connected populations, but traditional morphological or genomic approaches have so far been unsuccessful in fully resolving the species’ population structure and connectivity. My study pursued an alternative genomic approach, using low-coverage, whole genome sequencing (LcWGS) to address these important questions. I extracted DNA from 273 A.dubius specimens collected by collaborators from sevenregions across the species geographical range, from Greenland to New Jersey, USA. From LcWGS data, I identified 11,558,126 single nucleotide polymorphisms (SNPs) that allowed quantifying genetic differentiation between populations (F_ST), thereby revealing the genetic structuring of populations throughout the NWA. Despite the potentially homogenizing influence of the general north to south ocean circulation, I found a clear genetic break around Nova Scotia that delineated a northern from a southern A. dubius supergroup. Only within the southern supergroup, genetic distances increased with the geographic distance between sample sites. At the focal site of Stellwagen Bank (southern Gulf of Maine), A. dubius samples collected over several years (2014 – 2019) revealed small but significant temporal genetic differences that imply varying occupation of this offshore habitat by genetically different sand lance contingents. Inclusion of samples from the inshore congener A. americanus confirmed the clear genetic separation between both species and further determined that all sand lance caught on Stellwagen Bank are exclusively A. dubius. Overall, my work suggests the existence of two spatially distinct A. dubius populations with little ‘realized’ connectivity, which is critical knowledge to aid protection and management of offshore marine resources.

Major Advisor: Hannes Baumann

Associate Advisor: Nina Overgaard Therkildsen

Associate Advisor: Senjie Lin

ICES Journal of Marine Science publishes long-term fecundity study!

Posted on November 4, 2021November 4, 2021 by Hannes Baumann

2 November 2021. We are happy report that the ICES Journal of Marine Science just published the last major experimental paper on Atlantic silverside CO₂-sensitivity from our lab. Callie Concannon and co-authors report on two complementary, long-term rearing trials in 2015/16 and 2018/19, where silverside juveniles or newly fertilized embryos were reared under contrasting temperature and CO₂ conditions to maturity. This revealed negative effects of high CO₂ conditions on female fecundity, but only at the warm, not the cold temperature treatments (Fig. below). Our study and its data are novel, because they were generated by the first whole-life CO₂ rearing experiment of a fish and are the first empirical fecundity effects shown for a broadcast-spawning fish species.

The paper is also special to us, because its publication marks the erstwhile conclusion of our yearlong, NSF-funded efforts (OCE#1536165) to understand the CO₂ sensitivity and its mechanisms in this important forage fish and long-standing model in fish ecology and evolution. The project ran from 2015 - 2020, produced 15 publications, 2 book chapters, and over 40 presentations, while furthering the careers of a post-doc, a PhD student, 5 Master students and over 10 undergraduates.

A day on the water with CTDEEPs sturgeon researchers!

Posted on November 1, 2021November 4, 2021 by Hannes Baumann

28 September 2021. The day started nice enough but soon turned into dark threatening clouds, which the sturgeon researchers that day eyed with concern. Tom Savoy, Deb Pacileo, and Jacque Benway from CTDEEP, along with Kelli Mosca, Steve, Jake, and Hannes started to cast off late morning and slowly motored up the Connecticut River. "We're trying to catch the slack tide to set our sturgeon gill nets" explained Tom, the veteran sturgeon researcher, who has accompanied and steered most monitoring and protection efforts of these iconic fish over the past decades. It was Tom and his colleagues, who in 2014 caught the first baby Atlantic sturgeon in Connecticut River - a potential sign for a long hoped for recovery and the starting point of our project funded by CT SeaGrant.

The day trip was almost over, before it began. The downpour short but relentless and Jacque eyeing the lightening coming from the west with unease. But just before we could decide to fully head back, the radio call from the other boat that several sturgeon had indeed been caught in the gill nets! We therefore proceeded going through the routine measurement protocol that has been implemented for many years and is part of a federal permit to study this endangered species (No. 19641). Even a photograph is considered a sample, which is why we were glad to have our photographer Jacob Snyder (RedSkiesPhotography.com) fully accredited for the trip today. We saw with our own eyes, how a caught sturgeon was first being carefully pried loose from the gill-netting and placed in an aerated observation sump to prevent stress. All individuals are then checked for previously inserted tags using a specialized scanner (1) and if none is found, a new PIT-tag is inserted under the skin with the help of a syringe (3). All sturgeon are also measured for length (2), gape (5) and head width, and weighed (6) before being released back into the water. Tissue samples and in a limited number of fish also fin spine samples are taken for genetic information and growth data, the latter Kelli analyzed for her Masters Thesis.

The potential re-emergence of Atlantic sturgeon spawning in the Connecticut River is a success story of research and conservation, however, these efforts need to be sustained and widely communicated for the success to endure.