Nighttime observations (after 1900) were made when conditions were less than Beaufort 2 and the research vessel was located near the deep water edge. The research vessel motored along the edge of the sandbank where water depth typically drops, sometimes sharply, from ≤10 m to≥200 m within 0.5–1.0 km. Engines were turned off and the research platform drifted passively in the northbound current along the edge of the sandbank. A hydrophone was deployed to detect any GSK2126458 nmr acoustic cues of dolphins in the area.

Deck lights, and a floodlight located on the bridge, were used to facilitate identification and observations of both the prey and the dolphins. Although disturbance of foraging behavior is possible with lights, on occasion both deck lights and generators were turned

off during a drift and night-vision goggles allowed verification and detection of foraging dolphins. Once a drift offshore began, environmental conditions including location and water depth were recorded every 20 min. When dolphins were sighted from the boat, and often right next to the boat, group size was documented and age class composition and individual identifications were made when possible. Prey species were easily identified from the surface right next to the boat or underwater near the surface. Samples were collected using a dip net for verification during an observation or occasionally flew onto the deck during a chase by the dolphins. Divers regularly entered the water with cameras or an underwater video and hydrophones to document behaviors and sounds during feeding, as this is a semihabituated community of dolphins. buy LY2606368 On occasion, usually due to dangerous jellyfish at the surface, divers did not enter the water but observed

dolphins as they continued to chase and catch fish for hours next to the boat. Table 1 lists the number of observed foraging events and their variation in depth, distance traveled, mean duration, and prey species. Between 1991 and 2004, we collected 48 observations of nocturnal feeding. Duration of the drifting medchemexpress events ranged from 10 min to over 9 h (for some all night drifts) with an average of 3:20 h:min. Actual observations of dolphins during these drifts ranged from 10 min to over 8:45 h:min, with an average of 1:49 h:min. During foraging events, water depth ranged from a mean (± SD) minimum depth of 149.4 ± 75.9 m to a mean maximum depth of 307.6 ± 63.5 m. Observable groups (defined as animals engaged in similar behavior) of dolphins ranged in number from 1 to 15 with a mean of 6.8 ± 3.8 dolphins per foraging episode (Table S1). The most common prey species observed were flying fish (Family Exocoetidae), and squid (Doryteuthis sp.), followed by needlefish (Family Belonidae) and ballyhoo/halfbeaks (Family Hemiramphidae) (Table 1). Dolphins were observed from the surface chasing and consuming flying fish. Squid were chased just below the surface often into the depths.