Scottish Marine and Freshwater Science Vol 12 No 9

Commercial aquaculture farm production data have long been used to investigate the causes of stock mortality with analyses of disease focussing on individual presumptive causes. Substantial differences in mortality rates attributed to a specific disease have been reported and an interaction with other infections may explain a part of this variation (reviewed by Kotob et al., 2016).

Aquarium-based disease challenge experiments can provide information on the potential effect of multiple infections on mortality although the estimates of magnitude are not necessarily applicable to commercial production conditions. A practicable approach to estimating the size of interactive effects between infections on mortality using farm production data is therefore desirable. The Cox proportional hazards model is one possibility.

This report indicates that the model can be used to estimate approximate animal-level multiplicative mortality effects arising from multiple infections within aquaculture production cycles.