Diel vertical migration of freshwater fishes and zooplankton
Diel vertical migration (DVM) is a commonly observed behavioral phenomenon among many different pelagic organisms. Organisms following a “classic” DVM trajectory occur at shallower depths at or above the thermocline at night and descend to deeper water at dawn. DVM behavior appears to be a means by which pelagic organisms balance the competing objectives of growing quickly and minimizing predation risk. For many visual foragers, feeding efficiency is greatest at the higher light levels near the surface during the day. Other visual predators, however, can also forage efficiently under such conditions so there is a risk to occupying environments that are ideal for feeding. We use mathematical models (visual foraging models and bioenergetic models) and field sampling (hydroacoustics, optical plankton counters, and trawls) to study DVM patterns and the tradeoff between risk and growth. Study sites include Lake Superior, a brackish bay of the Baltic Sea in Sweden called Himmerfjärden, and Lake Hovsgol in Mongolia.
This variety of study sites allow us to test hypotheses about the drivers of DVM by looking at how DVM patterns differ with changes in the environment or with the physiology of the species. For example, in Lake Superior organisms at three different trophic levels (Mysid shrimp, coregonids, and lake trout) all undergo a classic DVM. For coregonids, the vertical extent of their DVM differs by species. Larger bodied cisco (lake herring) undergo a relatively shallow DVM, perhaps because their size offers some protection from predation by lake trout. In contrast, young-of-the-year Atlantic herring in Himmerfjärden undergo a reverse DVM in which they move down toward the bottom at night. This pattern makes sense for them because they apparently do not feed at night. Moving to cooler water near the bottom allows them to save energy. In Lake Hovsgol, grayling undergo a shallow DVM from slightly above the thermocline at night to slightly below it during the day. Grayling have no pelagic predators in Lake Hovsgol and this pattern matches the DVM of their zooplankton prey.
Ahrenstorff, T.D., Jensen, O.P., Weidel, B.C., Mendsaikhan, B., and T.R. Hrabik. 2012. Abundance, spatial distribution, and diet of endangered Hovsgol grayling (Thymallus nigrescens). Environmental Biology of Fishes. 94:465-476 PDF
Jensen, O.P., S. Hansson, T. Didrikas, J. D. Stockwell, T. R. Hrabik, T. Axenrot, J. F. Kitchell. 2011. Foraging, bioenergetic, and predation constraints on diel vertical migration: field observations and modeling of reverse migration by young-of-year herring Clupea harengus. Journal of Fish Biology. 78: 449-465. PDF
Stockwell, J.D., T.R. Hrabik, O.P. Jensen, D.L. Yule, and M. Balge. 2010. Empirical evaluation of predator-driven diel vertical migration in Lake Superior. Canadian Journal of Fisheries and Aquatic Sciences 67:473-485. PDF
Jensen, O.P., P.M. Yurista, T.R. Hrabik, J.D. Stockwell. 2009. Densities and diel vertical migration of Mysis relicta in Lake Superior: a comparison of optical plankton counter and net-based approaches. Verh. Internat. Verein. Limnol. 30:957-963. PDF
Hrabik, T.R., O.P. Jensen, S.J.D. Martell, C.J. Walters, and J.F. Kitchell. 2006. Diel vertical migration in the Lake Superior pelagic community. I. Changes in vertical migration of coregonids in response to varying predation risk. Canadian Journal of Fisheries and Aquatic Sciences 63: 2286-2295. PDF
Jensen, O.P., T.R. Hrabik, S.J.D. Martell, C.J. Walters, and J.F. Kitchell. 2006. Diel vertical migration in the Lake Superior pelagic community. II. Modeling trade-offs at an intermediate trophic level. Canadian Journal of Fisheries and Aquatic Sciences 63: 2296- 2307. PDF
Photo credits Olaf Jensen, Uwe Kils, Brant Allen, Jeremy Monroe | Site design Freshwaters Illustrated