Sound generated by a payao and comparison with auditory sensitivity of jack mackerelTrachurus japonicus

Abstract

Sound generated by a payao, an anchored bamboo fish aggregating device, is believed to be attractive to fish; but until now, there is no available record of payao‐generated sound. This study presents payao‐generated sound recorded by a hydrophone at water depths of 5, 10 and 15 m from a fixed distance of 3 m relative to the payao, and compares the sound with the auditory sensitivity of jack mackerel Trachurus japonicus measured at discrete frequencies from 100 to 2000 Hz using the auditory brainstem response protocol. A consistent peak appeared in the sound spectrum at 49 Hz and showed an increasing sound pressure level with depth, which suggests that payao sound may come from the anchor rope. However, the contribution of the bamboo raft can not yet be discounted. The hearing threshold curve indicated that the most sensitive frequency range in jack mackerel is from 92.1 dB at 800 Hz to 111.0 dB at 200 Hz. These results show that the dominant frequency range of payao sound does not correspond with the high sensitivity frequency range of fish hearing.

Schooling behavior of juvenile yellowfin tunaThunnus albacaresaround a fish aggregating device (FAD) in the Philippines

“…CRT of YT 0702 was 6 days. These short CRTs were reported before on juveniles (Babaran et al 2008;Mitsunaga et al 2012). These results suggest that the juveniles were on a start line to start to migrate when they reach about 30 cm FL (Aprieto 1991).…”

“…Josse et al (1998) indicated the important role of the SSL, assimilated as food, in vertical and horizontal tuna movements, during daytime and night time. Babaran et al (2008) also suggested the possibility of the coincidence of swimming depth of juveniles and prey around a payao. Mitsunaga et al (2012) reported a diurnal vertical swimming pattern of a juvenile, as if following the diurnal migration patterns of prey organisms in the SSL.…”

“…The receiver decodes the ID numbers of fish implanted with coded ultrasonic transmitters within the detection zone and records the ID and time stamp in flash memory. A previous study determined the potential detection zone to be 500 m in radius (Babaran et al 2008). The receiver was installed from 19 to 30 October 2007.…”

“…A payao is a moored FAD composed of a bamboo raft, mooring rope, an anchor and palm fronds as an aggregator (Babaran et al 2008). Yellowfin tuna in the Western and Central Pacific Ocean (WCPO) grow up to approximately 50 cm fork length (FL) per annum (Yang et al 1969;Wankowski 1981).…”

Local Ecological Knowledge (LEK) on Fish Behavior Around Anchored FADs: the Case of Tuna Purse Seine and Ringnet Fishers from Southern Philippines

“…For instance, a more direct assessment might be needed such as using acoustic techniques to relate the size of schools of fish to these waiting times. The production of sounds by anchored FADs may help orient and attract tuna toward the structure (Babaran et al, 2008), since according to Tolimieri et al (2000), sound can serve as a navigational cue for fishes.…”