Vol. 55, 2016

(update: 2016.8.5)

Temporal and Spatial Site Sharing during Spawning in Snappers Symphorichthys spilurus and Lutjanus bohar (Pisces: Perciformes: Lutjanidae) in Waters around Peleliu Island, Palau

Jiro Sakaue^1,*, Hiroshi Akino², Manabu Endo², Hitoshi Ida¹, and Takashi Asahida¹

¹School of Marine Biosciences, Kitasato University
²Pacific Odyssey Ltd. DBA Day Dream

(Received 20 October 2015; Accepted 26 July 2016)

Jiro Sakaue, Hiroshi Akino, Manabu Endo, Hitoshi Ida, and Takashi Asahida (2016) Two species of Lutjanidae, Symphorichthys spilurus and Lutjanus bohar, form spawning aggregation, a large school specifically formed for reproduction. Although they share the same spawning site at the southernmost reef in Peleliu Island, Palau, timing of spawning and their behaviors in the spawning and resting sites differ. Although the spawning behaviors have reported previously, long term and integrated observations documenting the size of the aggregation, exact spawning duration and timing, detailed behavioral profiles, as well as oceanic conditions upon spawning have never been reported. Here, we conducted a comparative study for these species and found behavioral and environmental cues that might be key to differentiate their ecological characteristics. S. spilurus begun to aggregate at full moon. Aggregations of L. bohar on the other hand, started from four days before full moon. Size of the aggregation was > 50,000 in S. spilurus, but about 7,000 in L. bohar. Both species migrated from the resting area to the spawning site in a diel rhythm. S. spilurus started spawning every half-moon, between the full moon and the new moon, while L. bohar spawns on every full moon. The first spawning took place at around dawn but the time shifted. S. spilurus spawned only when the current directs toward the southeast (offshore flow), while L. bohar spawns only when the current directs toward the southwest (tidal flow). Characteristic swimming behavior was observed for S. spilurus, in that, one or few males that could successfully chase the quick-swimming female fish could fertilize the eggs. In contrast, the behavior of L. bohar, was in a manner typical of several other lutjanid fish. The comparative and long-term field observation conducted over 10 years identified clear differences in the spawning behaviors of S. spilurus and L. bohar. Key behavioral and environmental factors found here might be key determinants for the ecology of these species.

Key words: Symphorichthys spilurus, Lutjanus bohar, Spawning aggregation, Lunar cycle, Current direction, Site sharing.

Correspondence: E-mail: sakaue01@sml-palau.com