Early survival rates and subsequent morphological abnormalities in landlocked, anadromous and hybrid (landlocked × anadromous) diploid and triploid Atlantic salmon

Abstract

Upwards of 95% triploidy was induced in landlocked, anadromous and hybrid (landlocked female × anadromous male) Atlantic salmon using heat shocks (5 min at 32°C, 20 min after fertilization and incubation at 10°C). On average, 23% of the treated eggs died within 24 h of fertilization. Most of the subsequent mortality occurred prior to hatching. In all cases, triploid hybrids had better survival rates than triploids of either pure form; triploid hybrids had survival rates comparable to those of diploid hybrids, whereas the survival rates of triploid pure forms were substantially lower than their respective diploid pure forms. Two types of morphological abnormalities were apparent in underyearling parr derived from control and heat shocked groups. Short gill covers were present in both diploid and triploid groups, and were not associated with the heat shock. Protruding lower jaws, however, were found almost exclusively in triploid fish, but were not present in all triploid fish within any particular treated group. No diploid fish originating from previously heat shocked eggs had protruding jaws, so the predisposition to this abnormality seems to depend on the triploid condition and not the heat shock.