574 



Fishery Bulletin 104(4) 



Results 



All 14 tags, with the exception of one, functioned prop- 

 erly for the duration of the three experiments. The one 

 exception, attached to a halibut in situ, was deployed for 

 234 days, but it provided data for only the first 42 days 

 because the battery failed. Tracking durations for AMP 

 (range: 42-479 days) were always equal to or greater 

 than the tracking durations for TSP (range: 42-348 

 days) because the memory for the archival data filled 

 up before the summary data memory. 



In the tank experiment, TSP was a better estimator 

 of longitude than AMP. TSP rejected fewer outliers and 

 produced a higher percentage of days with longitude 

 estimates (89.5%) than AMP (82.9%). Additionally, the 

 mean longitude error magnitude for TSP (1.0° ±1.1° SD) 

 was significantly smaller than that of AMP (2.0° ±3.2° 

 SD) (^=.5.63, df=650, P<0.0001). Longitude errors were 

 larger from late-fall to mid-winter in both tags when 

 estimated by AMP, but not TSP. The mean longitude 

 bias of TSP (-0.12° ±1.5° SD) was significantly smaller 

 than that of AMP (-0.64° ±3.7° SD) (/ = 2.3. df=650, 

 P=0.0215). TSP was not significantly biased and AMP 

 had a significant mean longitude bias. 



In the tank experiment, TSP also produced a higher 

 percentage of days with latitude estimates (88.2%) than 

 AMP (81.6%). However, there was not a significant 

 difference in the mean latitude error magnitude be- 

 tween TSP (4.2° ±5.1° SD) and AMP (4.4° ±4.2° SD) 

 (^=0.36, df=641, P=0.7155). The mean positional bias 

 of TSP (-0.02° ±6.7° SD) was not significantly different 

 (/<0.0001, df=641, P=0.9730) from that of AMP (-0.08° 

 ±6.1° SD) and neither software type had a significant 

 mean positional bias. 



In the fixed mooring experiment, TSP was a better 

 estimator than AMP of longitude. In general, the tags 

 produced fewer longitude estimates as depth increased, 

 and at each depth, TSP generated more estimates than 

 AMP (Fig. 2). The mean longitude error magnitude for 

 both programs increased at greater depth (Fig. 3). The 

 mean error magnitude of AMP and TSP estimates was 

 not significantly different at 27 m and 57 m (P>0.50), 

 but AMP estimates quickly degraded starting at 96 

 m (Fig. 3). For the tags at 96 m and 146 m, the mean 

 error magnitudes for TSP estimates were significantly 

 smaller (P<0.0001) than the AMP estimates of the same 

 tags. The mean longitude biases of both AMP and TSP 

 were generally to the west (positive values) of the ac- 

 tual position of the tags, except for AMP at 96 m (Fig. 

 3). In several cases, the mean biases were relatively 

 small for both AMP and TSP, however both had large 

 variances. 



As with the longitude estimates in the fixed moor- 

 ing experiment, the percentage of days with latitude 

 estimates decreased at greater depths (Fig. 2). Unlike 

 longitude, latitude was not estimated accurately by the 

 tags. Mean latitude error magnitude was significantly 

 smaller for TSP than for AMP at all depths, except 

 146 m (Fig. 3). The mean error magnitude for both 

 AMP and TSP showed no relationship to increasing 



Percentage of days with position estimates 

 50 1 00 



50 



E. 



£ 100 



150 



200 



TSP latitude 

 TSP longitude 

 AMP latitude 

 AMP longitude 



Figure 2 



Percentage of days with longitude and 

 latitude estimates as a function of depth 

 in the fixed mooring experiment. Two 

 programs, Argos Message Processor 

 (AMP) and Time Series Processor (TSP), 

 were used to calculate daily longitude 

 and latitude. 



depth (Fig. 3). The mean latitude biases of the tags in 

 the fixed mooring experiment were greater than the 

 mean longitude biases, and the biases by AMP were 

 more variable than those of TSP (Fig. 3). Like longi- 

 tude in the fixed mooring experiment, latitude was not 

 estimated at 146 m during the winter and spring. The 

 time span without geolocation estimates was longer for 

 latitude (242 days) than for longitude (165 days). 



In the wild fish experiment, four tags reported on- 

 ly to Argos satellites and geoposition was estimated 

 from summary data by using AMP. The percentage 

 of days with longitude estimates ranged from 0.0% to 

 2.3% (mean=l.l% ±1.0% SD), whereas the percentage 

 of days with latitude estimates ranged from 0.0%' to 

 1.5% (mean=0.6% ±0.7% SD). The other four tags were 

 physically recovered and geoposition was estimated by 

 using both summary data for AMP and detailed data 

 for TSP. For AMP, the percentage of days with longi- 

 tude estimates ranged from 0.0% to 12.0% (mean=5.8% 

 ±5.9% SD), whereas the percentage of days with lati- 

 tude estimates ranged from 0.0 to 7.9% (mean=3.4% 

 ±3.5% SD). For TSP, the percentage of days with lon- 

 gitude estimates was higher, ranging from 9.9% to 

 32.3% (mean=19.7% ±9.4% SD) and days with latitude 

 estimates ranged from 9.9% to 26.6% (mean = 16.9% 

 ±7.2% SD). 



The mean error magnitude of the longitude estimates 

 for AMP (;; = 4: 2.98° ±2.43° SD) was slightly larger 

 than that of TSP (;;=10; 2.23° ±2.38 SD°). However, 

 the mean error magnitude of the latitude estimates for 

 AMP {n=4; 2.76° ±1.59° SD) was approximately half 

 that of TSP (5.65° ±4.11° SD). The mean longitude bias 



