The hunting strategies of pelagic thresher sharks (Alopias pelagicus) were investigated at Pescador Island in the Philippines. It has long been suspected that thresher sharks hunt with their scythe-like tails but the kinematics associated with the behaviour in the wild are poorly understood. From 61 observations recorded by handheld underwater video camera between June and October 2010, 25 thresher shark shunting events were analysed. Thresher sharks employed tail-slaps to debilitate sardines at all times of day. Hunting events comprised preparation, strike, wind-down recovery and prey item collection phases, which occurred sequentially. Preparation phases were significantly longer than the others, presumably to enable a shark to windup a tail-slap. Tail-slaps were initiated by an adduction of the pectoral fins, a manoeuvre that changed a thresher shark's pitch promoting its posterior region to lift rapidly, and stall its approach. Tail-slaps occurred with such force that they may have caused dissolved gas to diffuse out of the water column forming bubbles. Thresher sharks were able to consume more than one sardine at a time, suggesting that tail-slapping is an effective foraging strategy for hunting schooling prey. Pelagic thresher sharks appear to pursue sardines opportunistically by day and night, which may make them vulnerable to fisheries. Alopiids possess specialist pectoral and caudal fins that are likely to have evolved, at least in part, for tail-slapping. The evidence is now clear; thresher sharks really do hunt with their tails.

Raptor migration rarely involves long-distance movements across open oceans. One exception occurs along the East-Asian Oceanic Flyway. We collected migration data at two terrestrial hawkwatch sites along this flyway to better understand open-ocean movements along this largely overwater corridor. At the northern end of the Philippines, at Basco on the island of Batan, we recorded 7587 migratory raptors in autumn 2014. Near the southern end of the Philippines, at Cape San Agustin on the island of Mindanao, we recorded 27,399 raptors migrating in autumn 2012. Chinese Sparrowhawks (Accipiter soloensis) were the most common raptors observed, making up approximately 89% and 92% of total records for Basco and Cape San Agustin, respectively. The Grey-faced Buzzard (Butastur indicus) was the second most common raptor migrant, accounting for 8% of the total counts at both watch sites. The migration period was about 1-2 wk earlier at Basco, the more northerly site, than at Cape San Agustin. Overwater flights at Basco peaked in both the morning and late afternoon, whereas at Cape San Agustin there was only a morning peak. In general, the rate of migration passage at both sites was highest with clear skies when winds were blowing from the northwest. However, we observed interspecific differences in migration behavior at both sites, with Accipiters more likely to be observed with tailwinds and eastward winds, and Grey-faced Buzzards more likely observed with headwinds. These results help to characterize poorly known aspects of raptor biology and to identify potential migratory bottlenecks or key sites for raptor conservation in little-studied Philippine tropical ecosystems.

Oceanic sharks are vulnerable to overexploitation due to their life-history strategies, and efforts to protect them in the wild have been stalled by transjurisdictional conflicts of interest. The pelagic thresher shark (Alopias pelagicus) is one such species that visits a seamount in the Philippines where its dependable presence has catalysed a burgeoning dive tourism industry and the designation of a conservation area. Nothing is known of the range and turnover of this population, but the regularity with which these sharks interact with cleaner wrasse on the seamount provides important stability for regional businesses that lack empirical knowledge of their vulnerability. We fitted 14 pelagic thresher sharks with acoustic tags and monitored their fine scale movements for 66 days (June to mid-August 2014). Individuals were present at the seamount for 32% of their days at liberty, and 42% of the tagged sharks were still being detected there at the end of the study. Thresher sharks showed preferences for visiting specific locations on the seamount where they interact with cleaner fish, and estimates of their fidelity to these sites provided scalars for visual census. Pelagic thresher sharks moved away from the seamount after early morning visits to cleaning stations using swim speeds of 3.79 km h-1 (± SD 1.43). These movements demonstrated that they have access to the jurisdictional waters of five provincial territories when dispersing from and returning to the seamount on a diurnal basis. While the seamount offers cleaner-associated services and refuge provision for pelagic thresher sharks, their scale of movement leaves them vulnerable to fisheries that operate in the region. Natural history observations provide context and reveal bias for their application in the management and conservation of this rare and vulnerable shark species.

SummarySelected fish were measured on markets along the Davao Gulf, Philippines between 2009 and 2016, augmenting the number of Length-Weight relationships (LWR) published earlier for the same area. LWRs were calculated for 28 fishes including those of 12 firstly reported, rare species. SL-TL and SL-FL relationships were determined for 28 and 25 species (also including 8 and 12 newly reported relationships, respectively).Minimum size at which individuals start developing forked tails are provided for Fish were weighed on a portable weighing scale (1 g accuracy). | MATERIALS AND METHODS MostFish were not sexed and data analyses were conducted without considering differences between males and females. The position of the eyes was recorded for the flatfish Psettodes erumei. Formulas TL = p + q × SL and FL = s + t × SL were used for calculating LLRs.

We used acoustic telemetry to investigate the roles of depth and temperature in the daytime foraging behaviours of 13 tagged pelagic thresher sharks by monitoring their fine scale vertical movements in the Philippines. Cumulatively, pelagic thresher shark dives traversed the entire water column where they encountered temperatures that ranged from 33°C at the surface to 12°C at 250 m depths throughout the day, but the movements of individuals varied in the extent of both their deep and shallow water limits. Dives were not synchronized to diurnal cycles, and periodicity reflected cycles of similar dives, the dives themselves, deviations, cruising, and individuality. Pelagic thresher shark movements between the warm surface layer and cooler waters below the thermocline (155 – 175 m) may reflect a common Alopiid strategy that balances maintaining tolerable ambient water temperatures with opportunities to search for and forage on spatially patchy distributions of prey.