Original paper
Two new methods for Regime Change Analyses
Manly, Bryan F. J.; Chotkowski, M.
Archiv für Hydrobiologie Volume 167 Number 1-4 (2006), p. 593 - 607
28 references
published: Oct 5, 2006
DOI: 10.1127/0003-9136/2006/0167-0593
ArtNo. ESP141016770035, Price: 29.00 €
Abstract
DOI: 10. 1127/0003-9136/2006/0167-05930003-9136/06/0167-0593 $ 3. 75 2006 E. Schweizerbart’sche Verlagsbuchhandlung, D-70176 Stuttgart 594 Bryan F. J. Manly and M. Chotkowski Fig. 1. The Fall Midwater Trawl (FMWT) sampling stations in the Sacramento-San Joaquin Delta (䊉), with the areas used for stratification of the delta. There are no areas numbered 2, 6 and 9 for historical reasons. Joaquin Delta, California, USA. Part of the investigation of the reasons for this decline is focussed on the analysis of historic data on the abundance of fish, zooplankton and mysids species obtained by various sampling methods. In particular, there is interest in whether some or all of the sampled species have exhibited regime changes in abundance in the past, where a regime change is considered to occur if the abundance of a species shows a substantial increase or decrease or if there is an abrupt change in the trend from one year to the next. For the purpose of an example we consider in particular the data obtained from fall midwater trawl (FMWT) sampling of delta smelt Hypomesus transpacificus (Pisces: Osmeridae) for the years 1967 to 2004. There is particular interest in the delta smelt because it is currently listed as a threatened species under both the California State and Federal Endangered Species Act (58 Federal Register 128541993). The data for this fish consists of counts from samples taken from September to December in different geographical areas in the