Content: Population genomics experiments of non-model organisms, such as most commercial fish, rely on isolating good integrity DNA from the study subjects. Yet, this task is not trivial as, when an organism dies, its DNA starts breaking down in small pieces. This process is called DNA degradation and can fortunately be stopped or slowed down by preserving the samples in cold and/or dry conditions. Here, we have assessed the effect of tissue type, storage time, preserving conditions and post-mortem intervale in fish DNA integrity. From the four factors tested, post-mortem intervale is the one that most drastically affects DNA integrity, tissues sampled after 24 hours of death yielding partial or totally degraded DNA. In order to preserve DNA integrity, we provide some recommendations to be considered when sampling fish tissue for genetic analysis.