Techniques for surveying exploited species - Conservation and Sustainable Use - page 81

by measuring demographic rates such as survival and productivity, and this
understanding can be used to turn monitoring information into a predictive tool
(Chapter 5). The trick is to decide what information is essential, and what is not
justified by the expected degree of increase in your understanding.
So, before deciding on a survey strategy for an exploited species, define a range
of questions that could be tackled, assess the time and financial costs of the methods
necessary to address them and weigh these costs against the expected benefits. For
example, if your species is productive and fast-growing, an age-structured model is
unlikely to give you much of an improvement in predictive power over a simple
unstructured model (see Section 5.4), so the extra effort required to gather
age-specific demographic rates in the field will almost certainly not be justified. By
identifying the most efficient approach in this way, you can avoid wasting time and
resources attempting to gain data at a level of detail that turns out to be impossible
or unnecessary. We expand on the theme of monitoring and decision making
under information and resource constraints in Section 7.4.
2.7 Resources
2.7.1 Websites
Software
DISTANCE. Distance sampled line and point transects, including spatial analysis and
mapping: http://www.ruwpa.st-and.ac.uk/distance/index.html
DENSITY. Spatial Capture-Mark-Recapture analysis: http://www.landcareresearch.co.nz/
services/software/density/index.asp
MARK. Huge suite of mark-recapture analyses for survival, abundance and more: http://www
.warnercnr.colostate.edu/~gwhite/mark/mark.htm
CAPTURE. Useful web-based analysis engine for closed population mark-recapture abundance
estimation: http://www.mbr-pwrc.usgs.gov/software.html
PRESENCE. The models in Royle et al . (2003, 2005): http://www.mbr-pwrc.usgs.gov/
software/doc/presence/presence.html
BAND2. Sample size for dead recovery analysis: http://www.mbr-pwrc.usgs.gov/software.
html
R. A powerful and flexible programme for implementing virtually any statistical analysis, includ-
ing randomisation and bootstrapping, known fate survival analysis and GLMs for habitat
analysis: http://www.r-project.org/
USER (User Specified Estimation Routine). Can be used to fit multinomial models for change in
ratios, productivity and survival based on counts: http://www.cbr. washington.edu/paramest/
user/
MULTIFAN-CL. Implements statistical catch-at-age models based on either length or age struc-
ture of offtake: http://www.multifan-cl.org/
RANGES Analyses spatial data, including home-ranges, dispersal distances and habitat associa-
tions. Not free: http://www.anatrack.com/
RESAMPLING. A basic package for simple randomization and bootstrapping procedures,
including a useful introduction to the subject: http://www.uvm.edu/~dhowell/StatPages/
Resampling/Resampling.html