Biology subjects

Marsden, J. E.

Publications and source records attributed to Marsden, J. E..

3 recordsLinked to original sources

bioRxiv2026

Thiamine availability and acquisition differ between natural and controlled environments

Thiamine Deficiency Complex (TDC) is a reproductive disorder that affects recruitment of diverse salmonine populations globally. Typical symptoms include behavioral and neurological abnormalities and high offspring mortality. TDC is common in hatcheries that rear salmonines obtained from wild populations, and symptoms are mitigated by thiamine treatment. However, no studies have quantified thiamine concentrations in wild embryos. Here, we evaluated whether fertilized eggs and/or embryos may acquire thiamine from natural sources (e.g., biotic breakdown products and diet) during development. Lake trout (Salvelinus namaycush) gametes were obtained from feral adults in Lake Champlain and fertilized eggs were grouped by family with paired rearing under natural (Lake Champlain) and artificial (controlled laboratory) conditions. Average thiamine concentrations were similar between lake-reared and laboratory-reared fish prior to hatch; however, lake-reared fish experienced significant increases in thiamine concentrations at and after hatching compared to previous stages and compared to laboratory-reared fish; laboratory-reared fish experienced no increases in thiamine concentrations. Water samples revealed an abundance of thiamine precursors and byproducts in the natural environment, which may serve as sources of thiamine for developing embryos. These results demonstrate that salmonine embryos can acquire thiamine from natural sources during development, which may mitigate effects of TDC.

ecology↗

bioRxiv2020

Rainbow smelt population responses to species invasions and change in environmental condition

Invasive species can have major disruptions on native food webs, yet the impact of species introductions and whether they will become invasive appears to be context-dependent. Rainbow smelt and alewife co-exist as invasive species in the Laurentian Great Lakes and as native species on the Atlantic coast of North America, but in Lake Champlain rainbow smelt is the dominant native forage fish and alewife are invasive. Alewife became abundant by 2007, providing an opportunity to explore the dynamics of these two species in a system where only one is invasive. We used data from a 31-year forage fish survey to compare demographics of rainbow smelt populations in three basins of Lake Champlain with different pelagic volumes, nutrient levels, and predator abundances. Rainbow smelt catch-per-unit-effort (CPUE) remained constant in the large, deep Main Lake before and after alewife invaded, but decreased in the two smaller basins. Declines were primarily a result of increased age-0 and age-1 mortality. Predation by top piscivores, system productivity, and resource competition alone could not explain the patterns in CPUE across the basins. The mechanisms that allow alewife and rainbow smelt to co-exist could be related to system volume and oxythermal habitat availability, and may explain why the two species do not negatively affect each other in other systems. Summer hypoxia in the smaller basins could force individuals into smaller habitat volumes with higher densities of competitors and cannibalistic adult smelt. Our findings suggest that habitat size mediates the impact of invasive alewife on native rainbow smelt.

ecology↗

bioRxiv2019

Differential lipid dynamics in stocked and wild juvenile lake trout

After more than 40 years of stocking, lake trout (Salvelinus namaycush) in Lake Champlain have started to exhibit strong, natural recruitment. The abrupt surge in recruitment suggests a change in limiting factors such as prey availability or overwinter survival. The distribution of juvenile wild lake trout varies in relative abundance among regions of Lake Champlain. The differences suggest the prey base, or foraging success, may vary geographically within the lake. Stocked and wild lake trout may differ in their ability to use resources and in overwinter survival. One metric that can indicate differences in resources across regions is lake trout lipid content, which reflects the quality of available food and serves as an important energy reserve for overwinter survival. We quantified total lipid content of stocked and wild juvenile lake trout across spatial (lake regions) and temporal (seasonal) scales. No spatial differences in lipid content were apparent. Wild fish had greater lipid content than stocked fish. Seasonally, stocked fish showed a continuous drop in lipid content from pre-winter levels at stocking to the following autumn. Wild fish showed a cyclical summer increase in lipids following winter depletion, which plateaued by autumn. The high lipid content of hatchery lake trout may be necessary as they acclimate to foraging in the wild. Hatcheries would benefit from evaluating whether post-stocking survival could be improved by altering feeding or rearing regimes.

ecology↗