SeaTag-MOD

Reporting Rates

February, 2014 (by Marco Flagg)

The below statistics is a first look at the ARGOS reporting rates of SeaTag-MOD satellite reporting rates organized by specific deployments. Customer identifying information is withheld. The statistics are based on all data of opportunity available at Desert Star the time of this report and date from early deployments of the tag in 2012 and 2013. The report is restricted to deployments of seven or more tags to limit noisy / potentially non-representative data from small sample sizes. For the purpose of this statistic, a tag is considered reporting if any number of validated ARGOS messages have been received after deployment.

DEPLOYMENT ID DEPLOYMENT YEAR ANIMAL FAMILY # OF TAGS DEPLOYED # OF TAGS REPORTING % REPORTING
1 2012

Anoplopomatidae

43 20 46.51%
2 2012

Odontaspididae

33 29 87.88%
3 2012

Istiophoridae

20 19 95.00%
4 2012

Istiophoridae

7 7 100%
5 2012

Scombridae

9 8 88.89%

Totals

112 83
Average: 74.11% 
Median: 88.89%

 Comparison to Musyl [1]

Musyl reported 577 out of 731 PSAT tags from MicroWave Telemetry and Wildlife Computer reporting. The average reporting rate for Musyl was 78.9% and the median reporting rate 81.8%. Removing deployments of less than seven tags from Musyl (i.e. same standard as statistics above), the average is 79.7% and median 83.6%.

Interpretation from an engineering perspective (by Marco Flagg, SeaTag-MOD designer)

The studies number of deployments was still quite small at five, although the total number of tags in the study is a reasonable sample size at 112. To the extent that this sample size supports an interpretation, the data shows generally often (4 out of 5 deployments) high reporting rates of 87.88% and above, but also the largest deployment of 43 tags with a reporting rate of only 46.51%. From the engineering perspective the tag's solar power can be expected to yield higher reporting rates than tags relying only on battery power (all other factors being equal), because two risk factors are removed: First, a battery failure or early depletion will not cause non-reporting in SeaTag-MOD. Second, battery powered tags require an immersion switch to limit transmitting to when the tag is at the surface. Fouling or failure of that switch may cause non-reporting. SeaTagMOD by contrast will transmit whenever its capacitors are fully solar charged, even if the tag is submerged.

Solar power may explain generally high reporting rates for SeaTag-MOD, but deployment #1 also shows that results can be variable. In case of deployment #1, the causes of low reporting were not exhaustively determined. However, this deployment had some risk factors. These including tagging a heavily fished species, the release at high latitudes in winter when sunlight charging is limited, and the potential of tags to drift ashore (and become inefficient transmitters) quickly. Tag design and human error play a role as well. Factors in beach recovered non-reporting tags from various deployments have included a cracked outer shell, torn off antenna and incorrect configuration of the tag (such as incorrect Argos ID or transmit day limit specified as zero).

[1]: Performance of pop-up satellite archival tags, Musyl et. al. 2011