Reader Comments
Post a new comment on this article
Post Your Discussion Comment
Please follow our guidelines for comments and review our competing interests policy. Comments that do not conform to our guidelines will be promptly removed and the user account disabled. The following must be avoided:
- Remarks that could be interpreted as allegations of misconduct
- Unsupported assertions or statements
- Inflammatory or insulting language
Thank You!
Thank you for taking the time to flag this posting; we review flagged postings on a regular basis.
closeBias in Sampling Areas
Posted by goodalle on 01 Apr 2014 at 13:10 GMT
As a former resident of Fort Walton Beach, I cannot help but notice the detailed map of Choctawhatchee Bay and adjacent Gulf sea shores showing the sampling areas appears biased to locations where there are large areas of underwater vegetation or corridors along the coastline through which the manatees would migrate to reach the bay. While these are valid focus areas for searching for manatees it seems to ignore another focus: access to freshwater. A major impediment to manatee mobility throughout the Gulf Coast region is their need to find a source of freshwater. In Choctawhatchee Bay, that freshwater is located at the heads of the bayous. Indeed, the only time I ever observed a manatee in the area, it was directly off my family's dock a short distance outside the Cinco Bayou bridge. Cinco Bayou is fed by two freshwater streams. Garnier's Bayou adjacent to it has a much large freshwater stream and the water at the headwaters is almost completely fresh. Only one brackish lake is shown to have been sampled, and it would have provided a low quality fresh water supply compared to other locations in the sample area. It should also be noted, economic interests will bias the reporting of manatee sightings. In areas where manatees have been cited, the Florida Marine Patrol is obligated to enforce strict watercraft speed limits. This is viewed as an economic burden on the community by the local authorities and as such, sighting reports are subject to a high burden of proof before they area accepted. In the case where we sighted the manatee in Cinco Bayou, the FMP refused to accept the sighting without photographic proof of the manatees' presence.
RE: Bias in Sampling Areas
MartinJulien replied to goodalle on 14 Apr 2014 at 21:56 GMT
Thank you for your interest in our work.
As explained in our manuscript our area of inference was restricted to what we identified as likely manatee habitats (some of these habitats included: estuaries, rivers, creeks and coastal areas). We divided these habitats into plots and then randomly selected plots from our area of inference. We checked the location that you described and based on your description, it appears that it was in fact included in our area of inference (i.e., it could potentially have been randomly selected). The specific location that you mentioned was not surveyed simply because it was not randomly selected. Selecting plots based on prior sightings (or reports from the public) instead of using a random sampling process could have in fact introduced some potential errors.
Best regards
Julien