NOTE Kerstetter et al.: Shark predation and scavenging on fishes equipped with satellite archival tags 



751 



tags, minimum straight-line distances were calculated 

 between the point of release and the first clearly trans- 

 mitted location of the tag following its release (pop-off) 

 (Argos location codes 0-3). 



At the time of tagging, the longline hook used to cap- 

 ture the fish was not visible in the mouth of the white 

 marlin. The leader was therefore cut as close as possible 

 to the fish before the fish was released, following the 

 standard operating procedure for the domestic pelagic 

 longline fleet. The fish was maintained alongside the 

 vessel for less than three minutes for the application of 

 the PSAT and a conventional streamer tag. Although the 

 white marlin was initially active at the side of the vessel, 

 some light bleeding from the gills was noted. After re- 

 lease, the fish swam away slowly under its own power. 



the dorsal musculature with a Wildlife Computers tita- 

 nium anchor. The tag was programmed to record the 

 temperature and depth occupied by the fish in binned 

 histograms, and the minimum and maximum tempera- 

 tures and depths for 12-hour time periods. However, 

 these 12-hour bins encompassed both day and night 

 periods. The tag was programmed to be released six 

 months after deployment. In the event of a premature 

 release, the tag was programmed to begin transmitting 

 stored data if it remained at the surface for longer than 

 three days. The opah was lively and quickly dived after 

 it was released. 



Results 



White marlin 2 (WM2) 



At 9:05 am on 2 August 2003, a white marlin was 

 observed on pelagic longline gear with the same configu- 

 ration in the same approximate area of Georges Bank as 

 WM1. The fish was caught by a circle hook (size 16/0) in 

 the right corner of the mouth, and although the stomach 

 was everted, the fish appeared to be in excellent physi- 

 cal condition. A PTT-100 HR tag had been activated at 

 6:30 am that morning, and was therefore collecting data 

 at the time of tagging. After the fish was brought to the 

 side of the vessel, both the PSAT and a conventional 

 streamer tag were attached to this fish in less than three 

 minutes by using the same protocol as that described for 

 WM1, and the fish swam strongly away from the vessel 

 after release without any evident bleeding. 



Opah 



At 5:52 pm local time on 21 November 2002, a female 

 opah was observed on pelagic longline gear set during 

 the day east of the Island of Hawaii. The fish was brought 

 to the side of the fishing vessel and a Wildlife Computers 

 (Redmond. WA) PAT2 model tag was attached through 



WM1 



Release of the PSAT was expected to occur on 10 Sep- 

 tember 2002 and the tag was expected to begin transmit- 

 ting data on that date, but the first transmission was 

 not received until almost two days later. At the time of 

 first transmission, the PSAT was 81.3 km (43.9 nmi) 

 west-southwest of the tagging location. A total of 81.5% 

 of the archived light level, temperature, and pressure 

 (depth) data was recovered. 



The light level, temperature, and pressure (depth) 

 readings over time are presented in Fig. 1 (A-C) and 

 summarized in Table 1. The first light level measure- 

 ments indicated that the fish was already in relatively 

 dark waters within one hour following its release. Light 

 levels continued to drop to almost zero during the next 

 ten hours and remained at that level for the next nine 

 days (Fig. 1A). During the next seven-day surface trans- 

 mission period, the tag recorded real-time day and night 

 differences in light levels, which indicated that the light 

 sensor was functioning properly. 



Sea surface temperatures in the area where the gear 

 was set and hauled back, varied from 25.2° to 26.7°C 

 (D. Kerstetter. unpubl. data) and the first temperature 



