Fish populations inside a well-enforced no-take zone rebound because removal pressure drops to zero, while spillover from the recovered zone can even boost catches just outside its border.
biomass(t+1) = biomass(t) + recovery*protected - fishing_pressure*(1-protected)
- Ocean grid size — ocean cells tracked for fish biomass.
- MPA coverage — fraction of the grid designated as a no-take marine protected area.
- Fishing pressure — harvest rate applied to unprotected cells.
- Biomass recovery rate — how fast fish populations rebound inside a protected cell.
Well-enforced MPAs like New Zealand's Goat Island reserve show fish biomass 5-10x higher than adjacent unprotected waters within a decade of protection.