Abstract:The embryonic development times, spawning timing and hatching rates of the black sea bream Acanthopagrus schlegelii were examined to investigate the potential effect of seawater temperature, tides and photoperiod on the reproductive rhythm of this species in Hiroshima Bay, Japan. Low temperatures decreased hatching rates and extended the hatching time, and the minimum temperature threshold for hatching was 15 C. Back-calculated spawning times indicated that the peak of spawning occurred just before sunset and … Show more
“…Decreased cumulative water temperature could imply a higher daily water temperature, therefore both correlations could finally imply the same. This trend has been observed in several other species, such as salmon, tuna, cod, black sea bream and flounder (Gillooly et al ., 2002; Gordoa & Carreras, 2014; Kawai et al ., 2022; Kurita et al ., 2011). In this study, we could not obtain data for hatching rate, egg size or developmental stage.…”
Fishes of the jawfish family Opistognathidae are cryptobenthic and distributed in subtropical seas, and new species are still being reported. Opistognathus spp. live alone in burrows and males orally brood their egg clutches. The life cycle of jawfish, including their reproductive behaviour, is poorly understood. Here we describe the natural reproduction and embryonic development of Opistognathus iyonis in Yamaguchi, Japan, based on underwater surveys for 3 years. Spawning was observed as female jawfish came into the male's burrow ~30 min before sunrise. The jawfish had a mean number of 4.4 egg clutches in the burrow through 48.2 days, and the egg took 12 days to hatching. The mean temperature for developmental days was 20.8°C. The mean and cumulative water temperature during development significantly correlated with the number of developmental days. During egg development, male jawfish took care of eggs by holding them for part of the time in their mouths. Hatching was observed ~20 min after sunset. When hatching occurred orally, eggs were pushed out and back repeatedly using the lower jaw; consequently, the egg clutches were let out in an upward direction. To our best knowledge, this is the first report of the reproductive behaviour of O. iyonis in the natural environment in the same area for several years.
“…Decreased cumulative water temperature could imply a higher daily water temperature, therefore both correlations could finally imply the same. This trend has been observed in several other species, such as salmon, tuna, cod, black sea bream and flounder (Gillooly et al ., 2002; Gordoa & Carreras, 2014; Kawai et al ., 2022; Kurita et al ., 2011). In this study, we could not obtain data for hatching rate, egg size or developmental stage.…”
Fishes of the jawfish family Opistognathidae are cryptobenthic and distributed in subtropical seas, and new species are still being reported. Opistognathus spp. live alone in burrows and males orally brood their egg clutches. The life cycle of jawfish, including their reproductive behaviour, is poorly understood. Here we describe the natural reproduction and embryonic development of Opistognathus iyonis in Yamaguchi, Japan, based on underwater surveys for 3 years. Spawning was observed as female jawfish came into the male's burrow ~30 min before sunrise. The jawfish had a mean number of 4.4 egg clutches in the burrow through 48.2 days, and the egg took 12 days to hatching. The mean temperature for developmental days was 20.8°C. The mean and cumulative water temperature during development significantly correlated with the number of developmental days. During egg development, male jawfish took care of eggs by holding them for part of the time in their mouths. Hatching was observed ~20 min after sunset. When hatching occurred orally, eggs were pushed out and back repeatedly using the lower jaw; consequently, the egg clutches were let out in an upward direction. To our best knowledge, this is the first report of the reproductive behaviour of O. iyonis in the natural environment in the same area for several years.
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