Abstract
Many euryhaline wanderer species exhibit seasonal habitat changes, and temperature is suggested to play a key role in this phenomenon. To examine this possibility, we tested the hypothesis that adaptable temperature ranges of euryhaline wanderers are narrower in a non-natal osmotic environment than in their natal osmotic environment using dace Tribolodon hakonensis, a freshwater born euryhaline fish, and black porgy Acanthopagrus schlegelii, a marine born euryhaline fish. In both species, all individuals survived for 48 h in all the tested temperatures in their natal osmotic environments. In non-natal osmotic environments, however, both low (dace: 6 °C, black porgy: 10 °C) and high temperatures (dace: 30 °C, black porgy: 33 °C) significantly reduced their survival. These results indicate that euryhaline wanderers have a narrowed adaptable temperature range in non-natal osmotic environments. The similar trend observed in these two species of freshwater and marine fishes suggests that this may be a general characteristic in euryhaline wanderers and could be one of the causes of their seasonal movements.
Highlights
Knowledge of the life history and ecology of fishes in estuaries has been accumulating in recent years [1], and it is becoming increasingly clear that many euryhaline wanderer species have common characteristics including seasonal habitat changes
Freshwater born euryhaline wanderers such as the gizzard shad Dorosoma cepedianum and the Japanese dace Tribolodon hakonensis migrate back to freshwater habitats during the winter season for overwintering after they entered estuaries or coastal areas in summer [1, 6,7,8,9]
Individuals were kept in a 20-l plastic bucket with a lid, which was filled with river water taken from the sampling site, and were transported to the Maizuru Fisheries Research Station (MFRS) of Kyoto University located in Maizuru, Kyoto Prefecture (35°29N, 135°22E)
Summary
Knowledge of the life history and ecology of fishes in estuaries has been accumulating in recent years [1], and it is becoming increasingly clear that many euryhaline wanderer species have common characteristics including seasonal habitat changes. Keywords Acanthopagrus schlegelli · Euryhaline wanderer · Japanese black porgy · Japanese dace · Natal and non-natal osmotic environment · Seasonal habitat change · Adaptable temperature · Tribolodon hakonensis Since black porgy seemed to be less tolerant to a non-natal osmotic environment than dace in a preliminary experiment, they were first transferred to 10 ppt seawater from full strength seawater.
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