Fishery
F
Fishing Mortality
Quick Definition
The instantaneous rate at which fish are removed from a population by fishing, denoted F in stock assessment equations.
📖 Full Definition
Fishing mortality (F) is the instantaneous mortality rate attributable to fishing, expressed as a dimensionless coefficient (per year) in the equation: Z = F + M, where Z is total instantaneous mortality and M is natural mortality. F = ln(N₀/Nₜ) due to fishing only. It is estimated in stock assessment models by fitting to age-structured catch-at-age data. The ratio F/F_MSY indicates whether a stock is overfished: values >1 mean fishing mortality exceeds the MSY target. Reducing F is the lever most directly controlled by fisheries managers.
🧪 Scientific Usage
F_0.1 (fishing mortality at 10% of the unfished slope of the yield-per-recruit curve) is an alternative, more conservative reference point to F_MSY used in some North Atlantic fisheries.