Expedición Internacional Vaquita Marina 2015: Survey Design

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Vaquita Woodcut Barb Taylor
Artwork by Barbara Taylor

Expedición International Vaquita Marina 2015 has undergone extensive international review.  The original design was drafted by the survey steering committee:  Lorenzo Rojas-Bracho (SEMARNAT), Barbara Taylor (NOAA Fisheries), Armando Jaramillo-Legorreta (SEMARNAT), Edwyna Nieto (SEMARNAT), Gustavo Cárdenas (SEMARNAT), Tim Gerrodette (NOAA Fisheries), Jay Barlow (NOAA Fisheries) and Annette Henry (NOAA Fisheries).  The steering committee agreed that the effort would benefit by an expert review and requested reviewers independently chosen by the International Whaling Commission Scientific Director and the President of the Society of Mammalogy.  A review was also agreed in a Mexico-USA bilateral meeting with coordinators Pablo Arenas for Mexico and Cisco Werner for the USA.  The two reviews were combined and the response to reviewers was discussed during a webinar chaired by Greg Donovan, Director of Science for the International Whaling Commission.  All reports and reviews are available in the links below together with the final survey design.

The figures shown below summarize the design.  The basic rationale is to cover the deeper water areas (20-50 meters) with the visual survey and the shallower water areas within the range of the vaquita with passive acoustic detectors (called CPODs).  There is an area of overlap (outlined in red) where there will be both visual and acoustic coverage.  The two greatest sources of imprecision in past surveys were the coverage in shallow waters and estimating the proportion of vaquitas seen on the trackline.  The grid of 134 CPODs should greatly increase precision in the shallow water areas.  Two independent teams of observers both using the 25 power binoculars will be used to gather the best data possible to estimate the proportion of vaquitas seen on the trackline.

Research Design for the 2015 Vaquita Abundance Study 330px    Details of Visual Transects in the Core Area for the 2015 Vaquita Abundance Study 330px 
Fig. 1. Research design for the 2015 vaquita abundance study. The area to be sampled visually is outlined in blue, and visual transects are shown as black north-south lines. The area to be sampled acoustically is outlined in green, and acoustic sensor (C-POD) locations are shown as black points. The area to be sampled with both acoustic and visual methods (the calibration area) is outlined in red. The gillnet exclusion area is shown as a dashed gray line, the Vaquita Refuge Area as a thin gray line, and Consag Rocks as a black triangle. Depth contours of 20m and 50m are shown.   Fig. 2. Details of visual transects in the core area for the 2015 vaquita abundance study. The core area is outlined in blue, and visual transects are shown as black north-south lines. Vaquita sightings are shown as red points, based on uniform survey coverage during the 1997 and 2008 surveys within the area outlined in gray. Depth contours of 20, 30, 40 and 50m are indicated by the diagonal ridges in the survey area. The black triangle shows the location of Consag Rocks. 

The survey design was also altered from the 2008 survey because of the anticipated decrease in the number of vaquitas that will likely result in fewer overall sightings.  To increase the number of sightings, about half of the time will be spent doing the primary tracklines (Figure 1) and half doing core tracklines (Figure 2) in the area of highest past vaquita density.  The analysis will be done by an expert panel composed of:  Lorenzo Rojas-Bracho (SEMARNAT), Armando Jaramillo-Legorreta (SEMARNAT), Miguel Angel Cisneros (INAPESCA), Barbara Taylor (NOAA Fisheries), Tim Gerrodette (NOAA Fisheries), Jeff Moore (NOAA Fisheries) , Jay Ver Hoef (NOAA Fisheries), Len Thomas (St. Andrews), Phillip Hammond (St. Andrews) and David Borchers (St. Andrews).

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Last modified: 10/23/2015