I am looking for a model describing how the predation pressure exerted by visual predators (i.e., mainly larval fish) on a small calanoid copepod changes throughout the year.
The system is a boreal lake. The involved species are brook trout (Salvelinus fontinalis) young-of-the-year (YOY) as the supposed major predator and Leptodiaptomus minutus as the prey. Other potential predators include minnows (e.g., Couesius plumbeus, Notropis atherinoides), however, we believe they play a minor role as their habitat is limited to the littoral zone.
Knowledge about the larval biology of brook trout appears to be scarce and incomplete, and it is quite possible that it turns out that they are not important predators of this copepod. However, this would be very valuable information too.
I am particularly interested in the seasonal change of the top-down control on the copepods, as I am trying to interpret results showing that these plankters undergo seasonal shifts in traits such as their individual dry weight.
Any suggestions of how to estimate the seasonal aspect of this factor, as well as useful information including larval development, typical seasonality of YOY biomass, YOY feeding preferences, relationship of feeding activity with environmental variables (e.g., water temperature) etc. will be highly appreciated! Big thanks to everyone who read until here ;-)
For example, Warren et al. (1986) argue that the seasonal pattern of copepod weight (dry mass per individual) in Lake Michigan is controlled by the abundance of YOY fish. While I observe a similar seasonal pattern of the copepod weight, the same fish species are not present at my study site, except for one (the spot-tail shiner Notropis hudsonius).
Warren, G., M. Evans, D. Jude, and J. Ayers. 1986. Seasonal variations in copepod size: effects of temperature, food abundance, and vertebrate predation. J. Plankt. Res. 8: 841–853.
Hi Tobias.
will you conduct your experiment in the field and/or in the laboratory? What is your question and/or hypothesis that do you want to answer or test? Based on your the answers propose a sample design! After that get in contact again! All the best, Mario
Thank you Mário, but I've already completed the field work and am now writing down the ms. Predation pressure would be an additional factor (among a range of differential variables I have obtained), potentially fruitful to better interpret the results I already have.
Though I'm not aware of a model that investigated exacly what you ask, there are a couple of papers that specifically deal with predation of copepods.
Colleen Petrik did studies of prey selection and relation of larval fish and copepods:
Petrik, C.M., Kristiansen, T., Lough, R.G., Davis, C.S., 2009. Prey selection of
larval haddock and cod on copepods with species-specific behavior: a modelbased
analysis. Marine Ecology Progress Series, 396: 123-143.
Petrik, Davis and Ji, 2010. Coupling models of hydrodynamics, prey, and larval haddock on Georges Bank. ICES CM 2010:L18
For models temperature is suggested as indicator for seasonal predation varibility due to increased grazing rates. From copepod viewpoint:
Plourde, Maps and Joly, 2009. Mortality and survival in early stages control recruitment in Clanus finmarchicus, J Plankton Res 31, 4, 371-388.
which we used in a 3d model:
Ji, Stegert and Davis, 2013. J Plankton Res. 35, 1, 66ß79 (see downloads).
Hope this helps,
Christoph
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