Infection Pressure on Fish in Cages

The paper’s master-equation ODE for n≥1 omits the detachment outflow term − n γ_n F_n(t): it prints dF_n/dt = β_{n−1} C F_{n−1} − β_n C F_n + (n+1) γ_{n+1} F_{n+1} (Eq. (6)), which breaks conservation of the total number of fish across compartments; the n=0 line correctly includes γ_1 F_1 − β_0 C F_0, but the general n≥1 line lacks the balancing loss to n−1. This is inconsistent with the preceding attachment/detachment rules (4)–(5) and the stated interpretation of C(t) = Vρ(t) as exogenous free-copepod abundance, and would cause ∑_n F_n to increase spuriously under detachment flows (a clear modeling error) . The candidate solution restores the missing − n γ_n F_n term, derives the conservative mean-field system, proves telescoping conservation of ∑_n F_n, and correctly specializes the stationary recursions for the two parameter-reduction cases the paper itself proposes (uniform β,γ and β0≠βacc with γ constant) .