Genetic parameters for Photobacterium damselae subsp. piscicida resistance, immunological markers and body weight in gilthead seabream (Sparus aurata)

A challenge test for Photobacterium damselae subsp. piscicida (Phdp) resistance was carried out in two juvenile populations of gilthead seabream (Sparus aurata L.): F2_ATL and F0_MED. At 250 days post-hatching (dph), a fish plasma sample was collected to measure humoral immune markers (peroxidase activity, bactericidal activity, and IgM immunoglobulin levels), and at 272 dph fish were weighed and inoculated with bacteria Phdp. From that time onwards, surviving fish were recorded for nine days, and days to death was registered. Heritabilities for body weight and Phdp survival were moderate, although for days to death the heritability was low. Regarding humoral immune markers, for peroxidase activity it was moderate, and for IgM levels and for bactericidal activity it was low. Genetic correlations for body weight with Phdp survival and days to death were high and positive, while with peroxidase activity and IgM levels they tended to be positive, although these estimates were not accurate. Regarding genetic correlations between Phdp survival and humoral immune markers, they were very high, positive with peroxidase activity, and negative with IgM levels and bactericidal activity. Some humoral immune markers, particularly peroxidase activity, along with performance traits such as body weight and absence of deformities, are proposed to be included in a selective breeding program to raise fish that are capable of coping with diseases