Symphorichthys spilurus

Grzelak, Katarzyna & Sørensen, Martin V., 2022, Echinoderes landersi Grzelak & amp; Sørensen 2022, sp. nov., Zoological Studies 55 (44), pp. 1-15 : 7

Symphorichthys spilurus

The huge aggregation of S. spilurus on the reef performed the following diel migration: In the daytime, loose pre-spawning aggregations occurred at several resting areas located northeastern part of the spawning site as shown by the yellow zone in figure 2, where tidal currents were much weaker than the spawning ground. The distance from these resting areas to the spawning site was about 1.0 to 1.5 km. The loose aggregations left the resting area before sunset and scattered in the shallow place of south reef (white zone of Fig. 2 ) of about 10 to 15 m deep. They rested individually, letting themselves drift in the bottom layer. Before dawn, the rested fishes moved to the tip of the reef and aggregated to form a huge school. When the tidal current was strong, exceeding more than two knots (1.0 m/ sec), the aggregation formed close to the substrata forming a flat and wide aggregation. Under weaker tidal currents of less than one knot (0.5 m /sec); however, the aggregation became vertical with a narrower expansion. Individuals that completed the spawning at the site swam back to the sheltered resting area one by one. In the earlier stages of the aggregation, the fish remained around the reef wall area and did not move to the tip of the reef, and even if they aggregated at the tip of the reef around at half moon, actual spawning did not occur. They migrated around the spawning site of Peleliu corner as shown by white zone ( Fig. 2 ), about 3 km round trip every day after the beginning of aggregation through the spawning season.

Figures

Fig. 2. Observation site: southernmost reef of Peleliu Island. The “resting area” where sub-aggregate schools of S. spilurus and L. bohar gather are highlighted in yellow and red, respectively. The spawning ground is marked in white circle.