Lutjanus bohar

Grzelak, Katarzyna & Sørensen, Martin V., 2022, Echinoderes landersi Grzelak & amp; Sørensen 2022, sp. nov., Zoological Studies 55 (44), pp. 1-15 : 7-8

Lutjanus bohar

Daytime, loose pre-spawning aggregations remained in a small resting area located off northwestern area of the spawning site as shown in red in figure 2, where tidal currents were much weaker than that in the protruded point of the spawning ground. The distance from the resting areas to the spawning site was about 300 m. After spawning they remained in the resting area all the day. Every early morning (before dawn) they moved from the resting area to the spawning site, and after spawning they returned to the resting area one by one. All the post-spawning fishes returned to the resting area within one to two hours. Thus the distance of the diel migration for spawning was about 0.6 km /day.

Nuptial coloration and spawning behaviors

The observed nuptial coloration of S. spilurus was as follows ( Fig. 6 ). Male: While forming the aggregation, the blue lines became darker, and the dorsal fin and a caudal fin became darker as well. Moreover, the color became much stronger during the courtship behavior; the body coloration became much stronger and was identical with dark body color. Female: Darkening of blue lines on the body, dorsal fin and caudal fin did not occur, while the whole body became pale and brighter which was identical with light body color. Nuptial coloration of L. bohar was less prominent than S. spilurus , but male exhibited darker and female showed lighter red nuptial coloration as shown in figure 6.

Spawning

Symphorichthys spilurus

At the spawning site, the aggregation of fully matured S. spilurus males and females formed in an ellipsoidal shape close to the bottom around 20 m depth when the current was weak, however, the school moved deeper to around 40 m depth when the current was strong. Dark colored males, i.e. fully matured individuals, occurred in the upper layers of the aggregation. The males followed a female and stimulated the flank of the female. At this time, sex ratio was not one to one but males dominated in number. After being stimulated by a male, the female started to swim up and down or right and left within the aggregation, and several males followed. The female kept the forefront position of the group and at a high swimming speed changing the directions quickly and abruptly. Female swam as if trying to shake off the following males. The direction of the rush swimming during the spawning was not constant, on some occasions a female swam horizontally, while other females swam in an arch, or even to obliquely downward, and thus the rush swimming direction was not predictable ( Fig. 7a ). Right after this behavior, emissions of smoke-like sperm were observed. Although the eggs are not visible, we were able to collect fertilized eggs after the spawning using the smoke-like sperms as marker. This mode of spawning was characterized by highly unpredictable swimming pattern of female fish and has hitherto not been reported in other reef fishes. In some cases a female escaped form the pursuing males as a result of its so quick motion, but in that case, the female did not release the eggs. The male fishes that could follow the quick-moving female spawned successfully. The number of the successful male can be one or few and the fish(es) release sperm at the same time. After the spawning, fish returned to the lower layers of the aggregation, and then gradually left the aggregation. Typically, spawning duration on a day of L. bohar was around 30-60 min, while that of S. spilurus lasted for 1-5h. Three females caught by spear fishing (average size of 45 cm SL, 2.2 kg BW), carried between 27 to 29 thousand eggs with a 0.8 mm in diameter.

Figures

Fig. 6. Nuptial coloration of: (a) S. spilurus and (b) L. bohar. Each male and female was marked M or F. Male were in the dark color morph, and female were in the light color morph.

Fig. 7. Photographs of actual spawning of (a) S. spilurus and (b) L. bohar. Dotted yellow trace indicates a locus of a rushing female individual.