The effects of temperature and salinity of hatchery water on early development of chum salmon (Oncorhynchus keta)

• Published in: Aquaculture Vol. 549; p. 737738
• Main Authors: Ban, Masatoshi, Itou, Hiromi, Nakashima, Ayumi, Sada, Iwao, Toda, Shuuich, Kagaya, Manabu, Hirama, Yoshinobu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25-02-2022
• Subjects: Chum salmon; Early development; Global warming; Water salination; Water salination; Global warming; Chum salmon; Early development
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2021.737738

Chum salmon Oncorhynchus keta is the most abundant and industrially important salmonid in Japan, of which Japanese hatcheries release about 1.8 × 109 fry annually. However, recent global warming and earthquake-induced crustal movement might have changed hatchery water environments. To sustainably maintain and operate hatcheries in Japan, we report the effects of rearing water temperature and salinity on the early development of chum salmon derived from the Chitose River. Effects are evaluated in terms of eyed-egg (Eer), hatching (Htr), and survival (Sur) rates, alevin body size, and the quality of the egg envelope. Fertilized eggs were reared in groundwater (GW) at different temperatures (4, 7, 10, 13, 16 °C). Alevin reared at 4 °C were larger but had less yolk, while those reared at 16 °C were smaller but hatched precociously. A significant decrease in Htr and Sur was observed in the 4 °C treatment, which we regard to be because of the small amount of residual egg yolk at the time of hatching. Eggs were also fertilized in GW or different concentrations of brackish groundwater (BGW 0.5, 1.0, 2.1, 4.1, 8.3 psu), and continuously reared under the same salinity conditions at fertilization. Those BGW treatments at 1.0 and 2.1 psu had much lower Htr values than those reared in GW and salinities of 0.5 psu, despite their having a comparable Eer. Mortality in BGW treatments of 1.0 and 2.1 psu occurred during hatching, because of precocious hatching. No change in egg membrane proteins occurred after fertilization in 4.1 and 8.3 psu treatments, and embryos did not develop to an eyed-egg stage. These results suggest that constant temperatures of 4 and 16 °C, and salinities exceeding 1.0 psu during fertilization can prevent or interfere with the normal early development of chum salmon eggs and larvae in the Chitose River. To avoid the adverse effects of salination, fertilization with GW and hardening of the egg envelope effectively increase Sur dramatically, even after transfer to BGW.
•Water temperature and salination affect Chitose River chum salmon alevin survival.•Rearing at 4 °C prolongs alevin hatching, reduces egg yolk, and decreases survival.•Fertilization at salinity >1 psu reduces egg envelop hardening and survival.•Fertilization with groundwater for 1 h and egg envelope hardening increases survivalxy4.