Comparing annual population growth estimates of the exotic invader Bythotrephes by using sediment and plankton records

The annual population growth of the exotic invader Bythotrephes cederstroemi was calculated from the spatial distribution and rate of accumulation of its diagnostic caudal processes in the sediments of Harp Lake, Ontario. To our knowledge, this is the first use of the sediment record to quantify the annual population growth of a zooplankton species on a whole‐lake scale with confidence estimates. In 1994, 553±254 (95% C.L.) animals m−2 were produced in Harp Lake, an estimate statistically indistinguishable from that developed independently from the plankton data and temperature‐dependent growth models (459 animals m−2). When annual population growth estimates will suffice, the sediment record offers several advantages. It requires less fieldwork than do plankton‐based approaches and requires the quantification of the means and variances of fewer parameters. It also can provide population growth estimates for the past. For example, the sediment record indicated that one‐third of all B. cederstroemi ever produced in Harp Lake predated the start of our plankton records in 1994. The sediment record may have other uses. The breakage of caudal processes may provide clues to the rates of fish predation on B. cederstroemi, suggesting, for example, that 40% of the Harp Lake B. cederstroemi were eaten by fish in 1994.