Analysis of monthly variation of biological conditions, metabolic parameters and antioxidative capacities in sea-based farmed Pacific abalone during summer days

Abstract

Pacific abalone, Haliotis discus hannai, has become the predominant farmed abalone species in Fujian, southern China, since 2006. As an introduced abalone species from northern China, mass mortality of the farmed Pacific abalones in Fujian often occurred during summer in recent years. However, this phenomenon of summer mortality still lacks thorough investigation. We conducted a field investigation to monitor biological conditions of the 2-year-old animals, including monthly survival rates; visual gonad index; monthly variation in metabolic parameters including protein, glycogen, and nonesterified fatty acid (NEFA) content; and enzyme activities of lactate dehydrogenase (LDH) and antioxidative capacities including superoxide dismutase (SOD) and total antioxidative capacity (T-AOC) from April to October 2014. A range of environmental parameters were assessed and correlated against biological indicators for abalone conditions, metabolic parameters, and antioxidative capacities. Results showed a total mortality rate of 58.58% over the sampled period. Visual gonad index assessment showed that the sampled animals had similar gonad development levels during each sampling date. Environmental parameters and abalone mortality monitored during the study showed significant positive correlation between seawater temperature and mortality of abalones. All energy resources tended to be depleted at the end of summer. Results also showed that both SOD and T-AOC increased in the first few months and then decreased in September and October. The variations of metabolic parameters and antioxidative capacities indicated an insufficient energy supply and peroxidative damage in the farmed animals during summer. This study provided the biological data of farmed Pacific abalone by field investigation in terms of summer mortality for the first time in southern China. These findings that might be applicable to the management and development of Pacific abalone aquaculture in sea-based farms of southern China were also discussed in the study.