Research article

Factors influencing larval coregonine spatial distribution in Lake Geneva (Europe) and Lake Superior (North America) during a single season near known spawning sites

¹ The Nature Conservancy, Washburn 54891, WI, USA
² U.S. Geological Survey, Great Lakes Science Center, Lake Superior Biological Station, 2800 Lake Shore Drive, Ashland 54806, WI, USA
³ Univ. Savoie Mont Blanc, INRAE, CARRTEL, 74200 Thonon-les-Bains, France
⁴ Grand Portage Band of Lake Superior Chippewa, Grand Portage 55605, MN, USA
⁵ Rubenstein Ecosystem Science Laboratory, University of Vermont, Burlington 05401, VT, USA
⁶ U.S. Fish and Wildlife Service, 2800 Lake Shore Drive, Ashland 54806, WI, USA
⁷ U.S. Geological Survey, Great Lakes Science Center, 1451 Green Road, Ann Arbor 48105, MI, USA
⁸ Current address: Minnesota Department of Natural Resources, 1356 Highway 61 East, Grand Marais, Minnesota 55604, USA

^* Corresponding author: jamie.dobosenski@tnc.org

Received: 22 January 2024
Accepted: 27 June 2024

Abstract

Survival rate of the larval stage is an important driver of fish recruitment. To understand mechanisms regulating larval survival it is important to understand the relative importance of abiotic and biotic factors that shape larval spatial distributions. We studied larval Coregonus distributions in surface waters (surface to 1 m) by repeatedly sampling study sites in two lakes that varied greatly in trophic state and regional climate. We evaluated the importance of bathymetric depth, Julian Day, edible zooplankton densities (EZ, ind. L⁻¹) and wind vectors on larval spatial distributions using generalized additive modeling. In both systems, larval counts declined in a negative exponential fashion with bathymetric depth, indicating shallow depths are critical nursery habitat. The north-south wind vectors and Julian Day (which was positively correlated with surface temperature) influenced larval distributions in Lake Geneva with larval counts related to both variables linearly, whereas the east-west wind vector and EZ were unimportant. Highest larval counts were during an offshore south wind and declined slightly with Julian Day. In Lake Superior, bathymetric depth and the east-west wind vector influenced larval distributions and were unrelated to EZ, Julian Day, and the north-south wind vector. Larval counts were highest when onshore southwest winds preceded sampling. Differences in how wind affected larval distribution (offshore vs. onshore) might be related to larval size with Lake Superior larvae considerably smaller (average length 12.9 mm vs. 15.9 mm); thus, more apt to be subjected to advection. Within coastal waters, Julian Day and wind vectors influence distributions, but their importance seemingly varies lake-to-lake.