This method first quantifies survey effort as length of track line sampled, then expresses SPUE as the number of whales sighted per standardized length of track.
3) all sightings were treated as single points, but the number of whales sighted is factored into the SPUE analysis.
For mapping purposes, the SPUE values were ranked into levels.
Calculations of effort and SPUE were performed with custom SAS programs developed at the University of Rhode Island.
Sightings of 203 whales occurred during unacceptable survey conditions (mostly due to high sea state), and eight whales were documented for cells with acceptable conditions but during which there was less than 2 km of effort during a particular 2-week period; therefore sightings of 1342 whales were included in the SPUE analysis.
The overall 5-year mean SPUE value for all 101 sampled cells was 11.
Annual mean SPUE was highest in 2000 and lowest in 2002 (Table 2), and the difference was almost an order of magnitude.
When separated into two-week periods pooled across all years, mean SPUE values varied considerably.
The timing of the SPUE maximum varied markedly between years: late February-early March in 1998, early to mid-April in 1999, late March--early April in 2000, early March to mid-April in 2001, and late February--early March in 2002.
The majority of cells within which right whales were sighted were inside the critical habitat, but 17 cells with SPUE >0 fell partially or entirely outside the critical habitat (Fig.
The SPUE analysis provided a more refined interpretation of raw sighting data than have earlier analyses by reducing bias caused by uneven allocation of effort.
Because aerial surveys were limited to summer and winter in the eastern Gulf of Mexico, data from these two seasons in this region were compared (by using a t-test) to data collected during surveys in the same two seasons in the western Gulf of Mexico to determine if mean whale shark SPUE was significantly different between the two areas.
There was no statistical difference in the SPUE of whale sharks between the eastern and western continental slope waters of the Gulf of Mexico (t-test, df=4, t-value=1.
The highest SPUE values that we observed occurred during the summer.
Number of Survey and region covered Season Effort (km) sharks SPUE UCS--western Gulf of Mexico winter 4382 1 0.