Table 4 Considerations for researchers using Wildlife Computers MiniPAT deployments to maximise data recovery

Programming

Deployment length and programming regime

Wildlife Computers MiniPATs will generate 1 geolocation message per deployment day. For longer deployments, more geolocation messages need to be sent and successfully decoded to reach a target data volume (30% in this case; Fig. 5)

The temporal range of satellite passes varies with latitude (more frequent toward the poles). For tags transmitting at a mean latitude of 46 ± 5° N in the North Atlantic, researchers could expect an average of 2 ± 0.3 passes per hour and to receive 3 ± 1 successfully decoded messages per satellite pass (grand mean from 29 PSATs, range 0–15 messages per pass)—i.e., approximately 6–7 messages per hour

When transmitting, MiniPATs cycle through data messages chronologically with no preference (i.e., all the data for the ith day and then all the data for the ith+1 day and so on)

Based on our calculations, a tag deployed for 350 days generating only geolocation data (350 messages, geolocation data/total data proportion = 1) it would take approximately 26 h of transmitting to reach 30% (110 messages) and 88 h to reach 100% of geolocation data. Alternatively, if the same tag was instead programmed to generate one auxiliary message per day (730 messages, geolocation data/total data proportion = 0.5), then this time would double to 56 h and 176 h for 30% and 100% of geolocation data, respectively. If another data type were the key goal of the study (e.g., depth data) then this same principle could be applied

Consequently, if the geolocation data/total data proportion is low, then researchers should expect it to take proportionally longer for geolocation data to be transmitted (Fig. 5)

Longer deployments are less likely to transmit all geolocation data and are associated with larger uncertainty and error (e.g., Fig. 3)

Higher ratios of geolocation data to “other” data (TAD, PDT, MixLayer etc.) should result in a higher likelihood of tag geolocation messages being recovered in a shorter timeframe. This is unless depth data are also used for geolocation (e.g., HMMoce)

Transmission

Pop-up location

There is greater satellite coverage at the poles, so transmitting tags will be “seen” more frequently if they pop-up in more poleward locations

A higher proportion of transmissions will be received in more poleward locations

Tag transmission

The time a tag transmits for can vary but, in general, longer transmissions = more data transmitted (Fig. 1). For a tag that has collected 2000 messages, 100% data recovery may take upwards of 30 transmission days, which is unlikely

Positive relationship with data recovery

Tag damage

If a tag is damaged, this will likely negatively affect data transmission [43, 44]

Non-damaged tags transmit more data

Tag biofouling

Biofouling is a well-known and studied issue for slower moving species and species that inhabit warmer waters [43]. Application of antifoul could help ensure biofouling does not negatively impact tag flotation and orientation during transmission phase (e.g., excessive listing due to globules of anti-foul or biofouling on the antenna)

Non-biofouled tags transmit more data